Merge branch 'qgroup' of git://git.jan-o-sch.net/btrfs-unstable into for-linus

Conflicts:
	fs/btrfs/ioctl.c
	fs/btrfs/ioctl.h
	fs/btrfs/transaction.c
	fs/btrfs/transaction.h

Signed-off-by: Chris Mason <chris.mason@fusionio.com>

15 files changed, 2697 insertions, 242 deletions

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 0c4fa2befae7..0bc4d3a10a5f 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -8,7 +8,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
            extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \
            export.o tree-log.o free-space-cache.o zlib.o lzo.o \
            compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
-           reada.o backref.o ulist.o
+           reada.o backref.o ulist.o qgroup.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
index a383c18e74e8..7d80ddd8f544 100644
--- a/fs/btrfs/backref.c
+++ b/fs/btrfs/backref.c
@@ -773,9 +773,8 @@ static int __add_keyed_refs(struct btrfs_fs_info *fs_info,
  */
 static int find_parent_nodes(struct btrfs_trans_handle *trans,
                              struct btrfs_fs_info *fs_info, u64 bytenr,
-                             u64 delayed_ref_seq, u64 time_seq,
-                             struct ulist *refs, struct ulist *roots,
-                             const u64 *extent_item_pos)
+                             u64 time_seq, struct ulist *refs,
+                             struct ulist *roots, const u64 *extent_item_pos)
 {
         struct btrfs_key key;
         struct btrfs_path *path;
@@ -837,7 +836,7 @@ again:
                                 btrfs_put_delayed_ref(&head->node);
                                 goto again;
                         }
-                        ret = __add_delayed_refs(head, delayed_ref_seq,
+                        ret = __add_delayed_refs(head, time_seq,
                                                  &prefs_delayed);
                         mutex_unlock(&head->mutex);
                         if (ret) {
@@ -981,8 +980,7 @@ static void free_leaf_list(struct ulist *blocks)
  */
 static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 delayed_ref_seq, u64 time_seq,
-                                struct ulist **leafs,
+                                u64 time_seq, struct ulist **leafs,
                                 const u64 *extent_item_pos)
 {
         struct ulist *tmp;
@@ -997,7 +995,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
                 return -ENOMEM;
         }
 
-        ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
+        ret = find_parent_nodes(trans, fs_info, bytenr,
                                 time_seq, *leafs, tmp, extent_item_pos);
         ulist_free(tmp);
 
@@ -1024,8 +1022,7 @@ static int btrfs_find_all_leafs(struct btrfs_trans_handle *trans,
  */
 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 delayed_ref_seq, u64 time_seq,
-                                struct ulist **roots)
+                                u64 time_seq, struct ulist **roots)
 {
         struct ulist *tmp;
         struct ulist_node *node = NULL;
@@ -1043,7 +1040,7 @@ int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
 
         ULIST_ITER_INIT(&uiter);
         while (1) {
-                ret = find_parent_nodes(trans, fs_info, bytenr, delayed_ref_seq,
+                ret = find_parent_nodes(trans, fs_info, bytenr,
                                         time_seq, tmp, *roots, NULL);
                 if (ret < 0 && ret != -ENOENT) {
                         ulist_free(tmp);
@@ -1376,11 +1373,9 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
         struct ulist *roots = NULL;
         struct ulist_node *ref_node = NULL;
         struct ulist_node *root_node = NULL;
-        struct seq_list seq_elem = {};
         struct seq_list tree_mod_seq_elem = {};
         struct ulist_iterator ref_uiter;
         struct ulist_iterator root_uiter;
-        struct btrfs_delayed_ref_root *delayed_refs = NULL;
 
         pr_debug("resolving all inodes for extent %llu\n",
                         extent_item_objectid);
@@ -1391,16 +1386,11 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
                 trans = btrfs_join_transaction(fs_info->extent_root);
                 if (IS_ERR(trans))
                         return PTR_ERR(trans);
-
-                delayed_refs = &trans->transaction->delayed_refs;
-                spin_lock(&delayed_refs->lock);
-                btrfs_get_delayed_seq(delayed_refs, &seq_elem);
-                spin_unlock(&delayed_refs->lock);
                 btrfs_get_tree_mod_seq(fs_info, &tree_mod_seq_elem);
         }
 
         ret = btrfs_find_all_leafs(trans, fs_info, extent_item_objectid,
-                                   seq_elem.seq, tree_mod_seq_elem.seq, &refs,
+                                   tree_mod_seq_elem.seq, &refs,
                                    &extent_item_pos);
         if (ret)
                 goto out;
@@ -1408,8 +1398,7 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
         ULIST_ITER_INIT(&ref_uiter);
         while (!ret && (ref_node = ulist_next(refs, &ref_uiter))) {
                 ret = btrfs_find_all_roots(trans, fs_info, ref_node->val,
-                                                seq_elem.seq,
-                                                tree_mod_seq_elem.seq, &roots);
+                                           tree_mod_seq_elem.seq, &roots);
                 if (ret)
                         break;
                 ULIST_ITER_INIT(&root_uiter);
@@ -1431,7 +1420,6 @@ int iterate_extent_inodes(struct btrfs_fs_info *fs_info,
 out:
         if (!search_commit_root) {
                 btrfs_put_tree_mod_seq(fs_info, &tree_mod_seq_elem);
-                btrfs_put_delayed_seq(delayed_refs, &seq_elem);
                 btrfs_end_transaction(trans, fs_info->extent_root);
         }
 
diff --git a/fs/btrfs/backref.h b/fs/btrfs/backref.h
index c18d8ac7b795..3a1ad3e2dcb0 100644
--- a/fs/btrfs/backref.h
+++ b/fs/btrfs/backref.h
@@ -58,8 +58,7 @@ int paths_from_inode(u64 inum, struct inode_fs_paths *ipath);
 
 int btrfs_find_all_roots(struct btrfs_trans_handle *trans,
                                 struct btrfs_fs_info *fs_info, u64 bytenr,
-                                u64 delayed_ref_seq, u64 time_seq,
-                                struct ulist **roots);
+                                u64 time_seq, struct ulist **roots);
 
 struct btrfs_data_container *init_data_container(u32 total_bytes);
 struct inode_fs_paths *init_ipath(s32 total_bytes, struct btrfs_root *fs_root,
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 67fe46fdee6f..fb21431fe4e0 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -321,7 +321,7 @@ struct tree_mod_root {
 struct tree_mod_elem {
         struct rb_node node;
         u64 index;              /* shifted logical */
-        struct seq_list elem;
+        u64 seq;
         enum mod_log_op op;
 
         /* this is used for MOD_LOG_KEY_* and MOD_LOG_MOVE_KEYS operations */
@@ -341,20 +341,50 @@ struct tree_mod_elem {
         struct tree_mod_root old_root;
 };
 
-static inline void
-__get_tree_mod_seq(struct btrfs_fs_info *fs_info, struct seq_list *elem)
+static inline void tree_mod_log_read_lock(struct btrfs_fs_info *fs_info)
 {
-        elem->seq = atomic_inc_return(&fs_info->tree_mod_seq);
-        list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
+        read_lock(&fs_info->tree_mod_log_lock);
 }
 
-void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
-                            struct seq_list *elem)
+static inline void tree_mod_log_read_unlock(struct btrfs_fs_info *fs_info)
+{
+        read_unlock(&fs_info->tree_mod_log_lock);
+}
+
+static inline void tree_mod_log_write_lock(struct btrfs_fs_info *fs_info)
+{
+        write_lock(&fs_info->tree_mod_log_lock);
+}
+
+static inline void tree_mod_log_write_unlock(struct btrfs_fs_info *fs_info)
 {
-        elem->flags = 1;
+        write_unlock(&fs_info->tree_mod_log_lock);
+}
+
+/*
+ * This adds a new blocker to the tree mod log's blocker list if the @elem
+ * passed does not already have a sequence number set. So when a caller expects
+ * to record tree modifications, it should ensure to set elem->seq to zero
+ * before calling btrfs_get_tree_mod_seq.
+ * Returns a fresh, unused tree log modification sequence number, even if no new
+ * blocker was added.
+ */
+u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
+                           struct seq_list *elem)
+{
+        u64 seq;
+
+        tree_mod_log_write_lock(fs_info);
         spin_lock(&fs_info->tree_mod_seq_lock);
-        __get_tree_mod_seq(fs_info, elem);
+        if (!elem->seq) {
+                elem->seq = btrfs_inc_tree_mod_seq(fs_info);
+                list_add_tail(&elem->list, &fs_info->tree_mod_seq_list);
+        }
+        seq = btrfs_inc_tree_mod_seq(fs_info);
         spin_unlock(&fs_info->tree_mod_seq_lock);
+        tree_mod_log_write_unlock(fs_info);
+
+        return seq;
 }
 
 void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
@@ -371,41 +401,46 @@ void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
         if (!seq_putting)
                 return;
 
-        BUG_ON(!(elem->flags & 1));
         spin_lock(&fs_info->tree_mod_seq_lock);
         list_del(&elem->list);
+        elem->seq = 0;
 
         list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
-                if ((cur_elem->flags & 1) && cur_elem->seq < min_seq) {
+                if (cur_elem->seq < min_seq) {
                         if (seq_putting > cur_elem->seq) {
                                 /*
                                  * blocker with lower sequence number exists, we
                                  * cannot remove anything from the log
                                  */
-                                goto out;
+                                spin_unlock(&fs_info->tree_mod_seq_lock);
+                                return;
                         }
                         min_seq = cur_elem->seq;
                 }
         }
+        spin_unlock(&fs_info->tree_mod_seq_lock);
+
+        /*
+         * we removed the lowest blocker from the blocker list, so there may be
+         * more processible delayed refs.
+         */
+        wake_up(&fs_info->tree_mod_seq_wait);
 
         /*
          * anything that's lower than the lowest existing (read: blocked)
          * sequence number can be removed from the tree.
          */
-        write_lock(&fs_info->tree_mod_log_lock);
+        tree_mod_log_write_lock(fs_info);
         tm_root = &fs_info->tree_mod_log;
         for (node = rb_first(tm_root); node; node = next) {
                 next = rb_next(node);
                 tm = container_of(node, struct tree_mod_elem, node);
-                if (tm->elem.seq > min_seq)
+                if (tm->seq > min_seq)
                         continue;
                 rb_erase(node, tm_root);
-                list_del(&tm->elem.list);
                 kfree(tm);
         }
-        write_unlock(&fs_info->tree_mod_log_lock);
-out:
-        spin_unlock(&fs_info->tree_mod_seq_lock);
+        tree_mod_log_write_unlock(fs_info);
 }
 
 /*
@@ -423,11 +458,9 @@ __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
         struct rb_node **new;
         struct rb_node *parent = NULL;
         struct tree_mod_elem *cur;
-        int ret = 0;
 
-        BUG_ON(!tm || !tm->elem.seq);
+        BUG_ON(!tm || !tm->seq);
 
-        write_lock(&fs_info->tree_mod_log_lock);
         tm_root = &fs_info->tree_mod_log;
         new = &tm_root->rb_node;
         while (*new) {
@@ -437,88 +470,81 @@ __tree_mod_log_insert(struct btrfs_fs_info *fs_info, struct tree_mod_elem *tm)
                         new = &((*new)->rb_left);
                 else if (cur->index > tm->index)
                         new = &((*new)->rb_right);
-                else if (cur->elem.seq < tm->elem.seq)
+                else if (cur->seq < tm->seq)
                         new = &((*new)->rb_left);
-                else if (cur->elem.seq > tm->elem.seq)
+                else if (cur->seq > tm->seq)
                         new = &((*new)->rb_right);
                 else {
                         kfree(tm);
-                        ret = -EEXIST;
-                        goto unlock;
+                        return -EEXIST;
                 }
         }
 
         rb_link_node(&tm->node, parent, new);
         rb_insert_color(&tm->node, tm_root);
-unlock:
-        write_unlock(&fs_info->tree_mod_log_lock);
-        return ret;
+        return 0;
 }
 
+/*
+ * Determines if logging can be omitted. Returns 1 if it can. Otherwise, it
+ * returns zero with the tree_mod_log_lock acquired. The caller must hold
+ * this until all tree mod log insertions are recorded in the rb tree and then
+ * call tree_mod_log_write_unlock() to release.
+ */
 static inline int tree_mod_dont_log(struct btrfs_fs_info *fs_info,
                                     struct extent_buffer *eb) {
         smp_mb();
         if (list_empty(&(fs_info)->tree_mod_seq_list))
                 return 1;
-        if (!eb)
-                return 0;
-        if (btrfs_header_level(eb) == 0)
+        if (eb && btrfs_header_level(eb) == 0)
+                return 1;
+
+        tree_mod_log_write_lock(fs_info);
+        if (list_empty(&fs_info->tree_mod_seq_list)) {
+                /*
+                 * someone emptied the list while we were waiting for the lock.
+                 * we must not add to the list when no blocker exists.
+                 */
+                tree_mod_log_write_unlock(fs_info);
                 return 1;
+        }
+
         return 0;
 }
 
 /*
- * This allocates memory and gets a tree modification sequence number when
- * needed.
+ * This allocates memory and gets a tree modification sequence number.
  *
- * Returns 0 when no sequence number is needed, < 0 on error.
- * Returns 1 when a sequence number was added. In this case,
- * fs_info->tree_mod_seq_lock was acquired and must be released by the caller
- * after inserting into the rb tree.
+ * Returns <0 on error.
+ * Returns >0 (the added sequence number) on success.
  */
 static inline int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
                                  struct tree_mod_elem **tm_ret)
 {
         struct tree_mod_elem *tm;
-        int seq;
 
-        if (tree_mod_dont_log(fs_info, NULL))
-                return 0;
-
-        tm = *tm_ret = kzalloc(sizeof(*tm), flags);
+        /*
+         * once we switch from spin locks to something different, we should
+         * honor the flags parameter here.
+         */
+        tm = *tm_ret = kzalloc(sizeof(*tm), GFP_ATOMIC);
         if (!tm)
                 return -ENOMEM;
 
-        tm->elem.flags = 0;
-        spin_lock(&fs_info->tree_mod_seq_lock);
-        if (list_empty(&fs_info->tree_mod_seq_list)) {
-                /*
-                 * someone emptied the list while we were waiting for the lock.
-                 * we must not add to the list, because no blocker exists. items
-                 * are removed from the list only when the existing blocker is
-                 * removed from the list.
-                 */
-                kfree(tm);
-                seq = 0;
-                spin_unlock(&fs_info->tree_mod_seq_lock);
-        } else {
-                __get_tree_mod_seq(fs_info, &tm->elem);
-                seq = tm->elem.seq;
-        }
-
-        return seq;
+        tm->seq = btrfs_inc_tree_mod_seq(fs_info);
+        return tm->seq;
 }
 
-static noinline int
-tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
-                             struct extent_buffer *eb, int slot,
-                             enum mod_log_op op, gfp_t flags)
+static inline int
+__tree_mod_log_insert_key(struct btrfs_fs_info *fs_info,
+                          struct extent_buffer *eb, int slot,
+                          enum mod_log_op op, gfp_t flags)
 {
-        struct tree_mod_elem *tm;
         int ret;
+        struct tree_mod_elem *tm;
 
         ret = tree_mod_alloc(fs_info, flags, &tm);
-        if (ret <= 0)
+        if (ret < 0)
                 return ret;
 
         tm->index = eb->start >> PAGE_CACHE_SHIFT;
@@ -530,8 +556,22 @@ tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
         tm->slot = slot;
         tm->generation = btrfs_node_ptr_generation(eb, slot);
 
-        ret = __tree_mod_log_insert(fs_info, tm);
-        spin_unlock(&fs_info->tree_mod_seq_lock);
+        return __tree_mod_log_insert(fs_info, tm);
+}
+
+static noinline int
+tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
+                             struct extent_buffer *eb, int slot,
+                             enum mod_log_op op, gfp_t flags)
+{
+        int ret;
+
+        if (tree_mod_dont_log(fs_info, eb))
+                return 0;
+
+        ret = __tree_mod_log_insert_key(fs_info, eb, slot, op, flags);
+
+        tree_mod_log_write_unlock(fs_info);
         return ret;
 }
 
@@ -543,6 +583,14 @@ tree_mod_log_insert_key(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
 }
 
 static noinline int
+tree_mod_log_insert_key_locked(struct btrfs_fs_info *fs_info,
+                             struct extent_buffer *eb, int slot,
+                             enum mod_log_op op)
+{
+        return __tree_mod_log_insert_key(fs_info, eb, slot, op, GFP_NOFS);
+}
+
+static noinline int
 tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
                          struct extent_buffer *eb, int dst_slot, int src_slot,
                          int nr_items, gfp_t flags)
@@ -555,14 +603,14 @@ tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
                 return 0;
 
         for (i = 0; i + dst_slot < src_slot && i < nr_items; i++) {
-                ret = tree_mod_log_insert_key(fs_info, eb, i + dst_slot,
+                ret = tree_mod_log_insert_key_locked(fs_info, eb, i + dst_slot,
                                               MOD_LOG_KEY_REMOVE_WHILE_MOVING);
                 BUG_ON(ret < 0);
         }
 
         ret = tree_mod_alloc(fs_info, flags, &tm);
-        if (ret <= 0)
-                return ret;
+        if (ret < 0)
+                goto out;
 
         tm->index = eb->start >> PAGE_CACHE_SHIFT;
         tm->slot = src_slot;
@@ -571,10 +619,26 @@ tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
         tm->op = MOD_LOG_MOVE_KEYS;
 
         ret = __tree_mod_log_insert(fs_info, tm);
-        spin_unlock(&fs_info->tree_mod_seq_lock);
+out:
+        tree_mod_log_write_unlock(fs_info);
         return ret;
 }
 
+static inline void
+__tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
+{
+        int i;
+        u32 nritems;
+        int ret;
+
+        nritems = btrfs_header_nritems(eb);
+        for (i = nritems - 1; i >= 0; i--) {
+                ret = tree_mod_log_insert_key_locked(fs_info, eb, i,
+                                              MOD_LOG_KEY_REMOVE_WHILE_FREEING);
+                BUG_ON(ret < 0);
+        }
+}
+
 static noinline int
 tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
                          struct extent_buffer *old_root,
@@ -583,9 +647,14 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
         struct tree_mod_elem *tm;
         int ret;
 
+        if (tree_mod_dont_log(fs_info, NULL))
+                return 0;
+
+        __tree_mod_log_free_eb(fs_info, old_root);
+
         ret = tree_mod_alloc(fs_info, flags, &tm);
-        if (ret <= 0)
-                return ret;
+        if (ret < 0)
+                goto out;
 
         tm->index = new_root->start >> PAGE_CACHE_SHIFT;
         tm->old_root.logical = old_root->start;
@@ -594,7 +663,8 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
         tm->op = MOD_LOG_ROOT_REPLACE;
 
         ret = __tree_mod_log_insert(fs_info, tm);
-        spin_unlock(&fs_info->tree_mod_seq_lock);
+out:
+        tree_mod_log_write_unlock(fs_info);
         return ret;
 }
 
@@ -608,7 +678,7 @@ __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
         struct tree_mod_elem *found = NULL;
         u64 index = start >> PAGE_CACHE_SHIFT;
 
-        read_lock(&fs_info->tree_mod_log_lock);
+        tree_mod_log_read_lock(fs_info);
         tm_root = &fs_info->tree_mod_log;
         node = tm_root->rb_node;
         while (node) {
@@ -617,18 +687,18 @@ __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
                         node = node->rb_left;
                 } else if (cur->index > index) {
                         node = node->rb_right;
-                } else if (cur->elem.seq < min_seq) {
+                } else if (cur->seq < min_seq) {
                         node = node->rb_left;
                 } else if (!smallest) {
                         /* we want the node with the highest seq */
                         if (found)
-                                BUG_ON(found->elem.seq > cur->elem.seq);
+                                BUG_ON(found->seq > cur->seq);
                         found = cur;
                         node = node->rb_left;
-                } else if (cur->elem.seq > min_seq) {
+                } else if (cur->seq > min_seq) {
                         /* we want the node with the smallest seq */
                         if (found)
-                                BUG_ON(found->elem.seq < cur->elem.seq);
+                                BUG_ON(found->seq < cur->seq);
                         found = cur;
                         node = node->rb_right;
                 } else {
@@ -636,7 +706,7 @@ __tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq,
                         break;
                 }
         }
-        read_unlock(&fs_info->tree_mod_log_lock);
+        tree_mod_log_read_unlock(fs_info);
 
         return found;
 }
@@ -664,7 +734,7 @@ tree_mod_log_search(struct btrfs_fs_info *fs_info, u64 start, u64 min_seq)
         return __tree_mod_log_search(fs_info, start, min_seq, 0);
 }
 
-static inline void
+static noinline void
 tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
                      struct extent_buffer *src, unsigned long dst_offset,
                      unsigned long src_offset, int nr_items)
@@ -675,18 +745,23 @@ tree_mod_log_eb_copy(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
         if (tree_mod_dont_log(fs_info, NULL))
                 return;
 
-        if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0)
+        if (btrfs_header_level(dst) == 0 && btrfs_header_level(src) == 0) {
+                tree_mod_log_write_unlock(fs_info);
                 return;
+        }
 
-        /* speed this up by single seq for all operations? */
         for (i = 0; i < nr_items; i++) {
-                ret = tree_mod_log_insert_key(fs_info, src, i + src_offset,
-                                              MOD_LOG_KEY_REMOVE);
+                ret = tree_mod_log_insert_key_locked(fs_info, src,
+                                                     i + src_offset,
+                                                     MOD_LOG_KEY_REMOVE);
                 BUG_ON(ret < 0);
-                ret = tree_mod_log_insert_key(fs_info, dst, i + dst_offset,
-                                              MOD_LOG_KEY_ADD);
+                ret = tree_mod_log_insert_key_locked(fs_info, dst,
+                                                     i + dst_offset,
+                                                     MOD_LOG_KEY_ADD);
                 BUG_ON(ret < 0);
         }
+
+        tree_mod_log_write_unlock(fs_info);
 }
 
 static inline void
@@ -699,7 +774,7 @@ tree_mod_log_eb_move(struct btrfs_fs_info *fs_info, struct extent_buffer *dst,
         BUG_ON(ret < 0);
 }
 
-static inline void
+static noinline void
 tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
                           struct extent_buffer *eb,
                           struct btrfs_disk_key *disk_key, int slot, int atomic)
@@ -712,30 +787,22 @@ tree_mod_log_set_node_key(struct btrfs_fs_info *fs_info,
         BUG_ON(ret < 0);
 }
 
-static void tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
-                                 struct extent_buffer *eb)
+static noinline void
+tree_mod_log_free_eb(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
 {
-        int i;
-        int ret;
-        u32 nritems;
-
         if (tree_mod_dont_log(fs_info, eb))
                 return;
 
-        nritems = btrfs_header_nritems(eb);
-        for (i = nritems - 1; i >= 0; i--) {
-                ret = tree_mod_log_insert_key(fs_info, eb, i,
-                                              MOD_LOG_KEY_REMOVE_WHILE_FREEING);
-                BUG_ON(ret < 0);
-        }
+        __tree_mod_log_free_eb(fs_info, eb);
+
+        tree_mod_log_write_unlock(fs_info);
 }
 
-static inline void
+static noinline void
 tree_mod_log_set_root_pointer(struct btrfs_root *root,
                               struct extent_buffer *new_root_node)
 {
         int ret;
-        tree_mod_log_free_eb(root->fs_info, root->node);
         ret = tree_mod_log_insert_root(root->fs_info, root->node,
                                        new_root_node, GFP_NOFS);
         BUG_ON(ret < 0);
@@ -1069,7 +1136,7 @@ __tree_mod_log_rewind(struct extent_buffer *eb, u64 time_seq,
         unsigned long p_size = sizeof(struct btrfs_key_ptr);
 
         n = btrfs_header_nritems(eb);
-        while (tm && tm->elem.seq >= time_seq) {
+        while (tm && tm->seq >= time_seq) {
                 /*
                  * all the operations are recorded with the operator used for
                  * the modification. as we're going backwards, we do the
@@ -2722,6 +2789,78 @@ done:
 }
 
 /*
+ * helper to use instead of search slot if no exact match is needed but
+ * instead the next or previous item should be returned.
+ * When find_higher is true, the next higher item is returned, the next lower
+ * otherwise.
+ * When return_any and find_higher are both true, and no higher item is found,
+ * return the next lower instead.
+ * When return_any is true and find_higher is false, and no lower item is found,
+ * return the next higher instead.
+ * It returns 0 if any item is found, 1 if none is found (tree empty), and
+ * < 0 on error
+ */
+int btrfs_search_slot_for_read(struct btrfs_root *root,
+                               struct btrfs_key *key, struct btrfs_path *p,
+                               int find_higher, int return_any)
+{
+        int ret;
+        struct extent_buffer *leaf;
+
+again:
+        ret = btrfs_search_slot(NULL, root, key, p, 0, 0);
+        if (ret <= 0)
+                return ret;
+        /*
+         * a return value of 1 means the path is at the position where the
+         * item should be inserted. Normally this is the next bigger item,
+         * but in case the previous item is the last in a leaf, path points
+         * to the first free slot in the previous leaf, i.e. at an invalid
+         * item.
+         */
+        leaf = p->nodes[0];
+
+        if (find_higher) {
+                if (p->slots[0] >= btrfs_header_nritems(leaf)) {
+                        ret = btrfs_next_leaf(root, p);
+                        if (ret <= 0)
+                                return ret;
+                        if (!return_any)
+                                return 1;
+                        /*
+                         * no higher item found, return the next
+                         * lower instead
+                         */
+                        return_any = 0;
+                        find_higher = 0;
+                        btrfs_release_path(p);
+                        goto again;
+                }
+        } else {
+                if (p->slots[0] >= btrfs_header_nritems(leaf)) {
+                        /* we're sitting on an invalid slot */
+                        if (p->slots[0] == 0) {
+                                ret = btrfs_prev_leaf(root, p);
+                                if (ret <= 0)
+                                        return ret;
+                                if (!return_any)
+                                        return 1;
+                                /*
+                                 * no lower item found, return the next
+                                 * higher instead
+                                 */
+                                return_any = 0;
+                                find_higher = 1;
+                                btrfs_release_path(p);
+                                goto again;
+                        }
+                        --p->slots[0];
+                }
+        }
+        return 0;
+}
+
+/*
  * adjust the pointers going up the tree, starting at level
  * making sure the right key of each node is points to 'key'.
  * This is used after shifting pointers to the left, so it stops
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index a0ee2f8e0566..00f9a50f986d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -91,6 +91,9 @@ struct btrfs_ordered_sum;
 /* for storing balance parameters in the root tree */
 #define BTRFS_BALANCE_OBJECTID -4ULL
 
+/* holds quota configuration and tracking */
+#define BTRFS_QUOTA_TREE_OBJECTID 8ULL
+
 /* orhpan objectid for tracking unlinked/truncated files */
 #define BTRFS_ORPHAN_OBJECTID -5ULL
 
@@ -883,6 +886,72 @@ struct btrfs_block_group_item {
         __le64 flags;
 } __attribute__ ((__packed__));
 
+/*
+ * is subvolume quota turned on?
+ */
+#define BTRFS_QGROUP_STATUS_FLAG_ON             (1ULL << 0)
+/*
+ * SCANNING is set during the initialization phase
+ */
+#define BTRFS_QGROUP_STATUS_FLAG_SCANNING       (1ULL << 1)
+/*
+ * Some qgroup entries are known to be out of date,
+ * either because the configuration has changed in a way that
+ * makes a rescan necessary, or because the fs has been mounted
+ * with a non-qgroup-aware version.
+ * Turning qouta off and on again makes it inconsistent, too.
+ */
+#define BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT   (1ULL << 2)
+
+#define BTRFS_QGROUP_STATUS_VERSION        1
+
+struct btrfs_qgroup_status_item {
+        __le64 version;
+        /*
+         * the generation is updated during every commit. As older
+         * versions of btrfs are not aware of qgroups, it will be
+         * possible to detect inconsistencies by checking the
+         * generation on mount time
+         */
+        __le64 generation;
+
+        /* flag definitions see above */
+        __le64 flags;
+
+        /*
+         * only used during scanning to record the progress
+         * of the scan. It contains a logical address
+         */
+        __le64 scan;
+} __attribute__ ((__packed__));
+
+struct btrfs_qgroup_info_item {
+        __le64 generation;
+        __le64 rfer;
+        __le64 rfer_cmpr;
+        __le64 excl;
+        __le64 excl_cmpr;
+} __attribute__ ((__packed__));
+
+/* flags definition for qgroup limits */
+#define BTRFS_QGROUP_LIMIT_MAX_RFER     (1ULL << 0)
+#define BTRFS_QGROUP_LIMIT_MAX_EXCL     (1ULL << 1)
+#define BTRFS_QGROUP_LIMIT_RSV_RFER     (1ULL << 2)
+#define BTRFS_QGROUP_LIMIT_RSV_EXCL     (1ULL << 3)
+#define BTRFS_QGROUP_LIMIT_RFER_CMPR    (1ULL << 4)
+#define BTRFS_QGROUP_LIMIT_EXCL_CMPR    (1ULL << 5)
+
+struct btrfs_qgroup_limit_item {
+        /*
+         * only updated when any of the other values change
+         */
+        __le64 flags;
+        __le64 max_rfer;
+        __le64 max_excl;
+        __le64 rsv_rfer;
+        __le64 rsv_excl;
+} __attribute__ ((__packed__));
+
 struct btrfs_space_info {
         u64 flags;
 
@@ -1030,6 +1099,13 @@ struct btrfs_block_group_cache {
         struct list_head cluster_list;
 };
 
+/* delayed seq elem */
+struct seq_list {
+        struct list_head list;
+        u64 seq;
+};
+
+/* fs_info */
 struct reloc_control;
 struct btrfs_device;
 struct btrfs_fs_devices;
@@ -1044,6 +1120,7 @@ struct btrfs_fs_info {
         struct btrfs_root *dev_root;
         struct btrfs_root *fs_root;
         struct btrfs_root *csum_root;
+        struct btrfs_root *quota_root;
 
         /* the log root tree is a directory of all the other log roots */
         struct btrfs_root *log_root_tree;
@@ -1144,6 +1221,8 @@ struct btrfs_fs_info {
         spinlock_t tree_mod_seq_lock;
         atomic_t tree_mod_seq;
         struct list_head tree_mod_seq_list;
+        struct seq_list tree_mod_seq_elem;
+        wait_queue_head_t tree_mod_seq_wait;
 
         /* this protects tree_mod_log */
         rwlock_t tree_mod_log_lock;
@@ -1298,6 +1377,29 @@ struct btrfs_fs_info {
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
         u32 check_integrity_print_mask;
 #endif
+        /*
+         * quota information
+         */
+        unsigned int quota_enabled:1;
+
+        /*
+         * quota_enabled only changes state after a commit. This holds the
+         * next state.
+         */
+        unsigned int pending_quota_state:1;
+
+        /* is qgroup tracking in a consistent state? */
+        u64 qgroup_flags;
+
+        /* holds configuration and tracking. Protected by qgroup_lock */
+        struct rb_root qgroup_tree;
+        spinlock_t qgroup_lock;
+
+        /* list of dirty qgroups to be written at next commit */
+        struct list_head dirty_qgroups;
+
+        /* used by btrfs_qgroup_record_ref for an efficient tree traversal */
+        u64 qgroup_seq;
 
         /* filesystem state */
         u64 fs_state;
@@ -1527,6 +1629,30 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_DEV_ITEM_KEY      216
 #define BTRFS_CHUNK_ITEM_KEY    228
 
+/*
+ * Records the overall state of the qgroups.
+ * There's only one instance of this key present,
+ * (0, BTRFS_QGROUP_STATUS_KEY, 0)
+ */
+#define BTRFS_QGROUP_STATUS_KEY         240
+/*
+ * Records the currently used space of the qgroup.
+ * One key per qgroup, (0, BTRFS_QGROUP_INFO_KEY, qgroupid).
+ */
+#define BTRFS_QGROUP_INFO_KEY           242
+/*
+ * Contains the user configured limits for the qgroup.
+ * One key per qgroup, (0, BTRFS_QGROUP_LIMIT_KEY, qgroupid).
+ */
+#define BTRFS_QGROUP_LIMIT_KEY          244
+/*
+ * Records the child-parent relationship of qgroups. For
+ * each relation, 2 keys are present:
+ * (childid, BTRFS_QGROUP_RELATION_KEY, parentid)
+ * (parentid, BTRFS_QGROUP_RELATION_KEY, childid)
+ */
+#define BTRFS_QGROUP_RELATION_KEY       246
+
 #define BTRFS_BALANCE_ITEM_KEY  248
 
 /*
@@ -2508,6 +2634,49 @@ static inline void btrfs_set_dev_stats_value(struct extent_buffer *eb,
                             sizeof(val));
 }
 
+/* btrfs_qgroup_status_item */
+BTRFS_SETGET_FUNCS(qgroup_status_generation, struct btrfs_qgroup_status_item,
+                   generation, 64);
+BTRFS_SETGET_FUNCS(qgroup_status_version, struct btrfs_qgroup_status_item,
+                   version, 64);
+BTRFS_SETGET_FUNCS(qgroup_status_flags, struct btrfs_qgroup_status_item,
+                   flags, 64);
+BTRFS_SETGET_FUNCS(qgroup_status_scan, struct btrfs_qgroup_status_item,
+                   scan, 64);
+
+/* btrfs_qgroup_info_item */
+BTRFS_SETGET_FUNCS(qgroup_info_generation, struct btrfs_qgroup_info_item,
+                   generation, 64);
+BTRFS_SETGET_FUNCS(qgroup_info_rfer, struct btrfs_qgroup_info_item, rfer, 64);
+BTRFS_SETGET_FUNCS(qgroup_info_rfer_cmpr, struct btrfs_qgroup_info_item,
+                   rfer_cmpr, 64);
+BTRFS_SETGET_FUNCS(qgroup_info_excl, struct btrfs_qgroup_info_item, excl, 64);
+BTRFS_SETGET_FUNCS(qgroup_info_excl_cmpr, struct btrfs_qgroup_info_item,
+                   excl_cmpr, 64);
+
+BTRFS_SETGET_STACK_FUNCS(stack_qgroup_info_generation,
+                         struct btrfs_qgroup_info_item, generation, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_qgroup_info_rfer, struct btrfs_qgroup_info_item,
+                         rfer, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_qgroup_info_rfer_cmpr,
+                         struct btrfs_qgroup_info_item, rfer_cmpr, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_qgroup_info_excl, struct btrfs_qgroup_info_item,
+                         excl, 64);
+BTRFS_SETGET_STACK_FUNCS(stack_qgroup_info_excl_cmpr,
+                         struct btrfs_qgroup_info_item, excl_cmpr, 64);
+
+/* btrfs_qgroup_limit_item */
+BTRFS_SETGET_FUNCS(qgroup_limit_flags, struct btrfs_qgroup_limit_item,
+                   flags, 64);
+BTRFS_SETGET_FUNCS(qgroup_limit_max_rfer, struct btrfs_qgroup_limit_item,
+                   max_rfer, 64);
+BTRFS_SETGET_FUNCS(qgroup_limit_max_excl, struct btrfs_qgroup_limit_item,
+                   max_excl, 64);
+BTRFS_SETGET_FUNCS(qgroup_limit_rsv_rfer, struct btrfs_qgroup_limit_item,
+                   rsv_rfer, 64);
+BTRFS_SETGET_FUNCS(qgroup_limit_rsv_excl, struct btrfs_qgroup_limit_item,
+                   rsv_excl, 64);
+
 static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
 {
         return sb->s_fs_info;
@@ -2703,6 +2872,8 @@ int btrfs_force_chunk_alloc(struct btrfs_trans_handle *trans,
 int btrfs_trim_fs(struct btrfs_root *root, struct fstrim_range *range);
 
 int btrfs_init_space_info(struct btrfs_fs_info *fs_info);
+int btrfs_delayed_refs_qgroup_accounting(struct btrfs_trans_handle *trans,
+                                         struct btrfs_fs_info *fs_info);
 /* ctree.c */
 int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
                      int level, int *slot);
@@ -2753,6 +2924,9 @@ int btrfs_search_slot(struct btrfs_trans_handle *trans, struct btrfs_root
                       ins_len, int cow);
 int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key,
                           struct btrfs_path *p, u64 time_seq);
+int btrfs_search_slot_for_read(struct btrfs_root *root,
+                               struct btrfs_key *key, struct btrfs_path *p,
+                               int find_higher, int return_any);
 int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                        struct btrfs_root *root, struct extent_buffer *parent,
                        int start_slot, int cache_only, u64 *last_ret,
@@ -2835,11 +3009,22 @@ static inline void free_fs_info(struct btrfs_fs_info *fs_info)
         kfree(fs_info->chunk_root);
         kfree(fs_info->dev_root);
         kfree(fs_info->csum_root);
+        kfree(fs_info->quota_root);
         kfree(fs_info->super_copy);
         kfree(fs_info->super_for_commit);
         kfree(fs_info);
 }
 
+/* tree mod log functions from ctree.c */
+u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
+                           struct seq_list *elem);
+void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
+                            struct seq_list *elem);
+static inline u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
+{
+        return atomic_inc_return(&fs_info->tree_mod_seq);
+}
+
 /* root-item.c */
 int btrfs_find_root_ref(struct btrfs_root *tree_root,
                         struct btrfs_path *path,
@@ -3198,17 +3383,49 @@ void btrfs_reada_detach(void *handle);
 int btree_readahead_hook(struct btrfs_root *root, struct extent_buffer *eb,
                          u64 start, int err);
 
-/* delayed seq elem */
-struct seq_list {
+/* qgroup.c */
+struct qgroup_update {
         struct list_head list;
-        u64 seq;
-        u32 flags;
+        struct btrfs_delayed_ref_node *node;
+        struct btrfs_delayed_extent_op *extent_op;
 };
 
-void btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
-                            struct seq_list *elem);
-void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
-                            struct seq_list *elem);
+int btrfs_quota_enable(struct btrfs_trans_handle *trans,
+                       struct btrfs_fs_info *fs_info);
+int btrfs_quota_disable(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info);
+int btrfs_quota_rescan(struct btrfs_fs_info *fs_info);
+int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
+                              struct btrfs_fs_info *fs_info, u64 src, u64 dst);
+int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
+                              struct btrfs_fs_info *fs_info, u64 src, u64 dst);
+int btrfs_create_qgroup(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info, u64 qgroupid,
+                        char *name);
+int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
+                              struct btrfs_fs_info *fs_info, u64 qgroupid);
+int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
+                       struct btrfs_fs_info *fs_info, u64 qgroupid,
+                       struct btrfs_qgroup_limit *limit);
+int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info);
+void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info);
+struct btrfs_delayed_extent_op;
+int btrfs_qgroup_record_ref(struct btrfs_trans_handle *trans,
+                            struct btrfs_delayed_ref_node *node,
+                            struct btrfs_delayed_extent_op *extent_op);
+int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
+                             struct btrfs_fs_info *fs_info,
+                             struct btrfs_delayed_ref_node *node,
+                             struct btrfs_delayed_extent_op *extent_op);
+int btrfs_run_qgroups(struct btrfs_trans_handle *trans,
+                      struct btrfs_fs_info *fs_info);
+int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
+                         struct btrfs_fs_info *fs_info, u64 srcid, u64 objectid,
+                         struct btrfs_qgroup_inherit *inherit);
+int btrfs_qgroup_reserve(struct btrfs_root *root, u64 num_bytes);
+void btrfs_qgroup_free(struct btrfs_root *root, u64 num_bytes);
+
+void assert_qgroups_uptodate(struct btrfs_trans_handle *trans);
 
 static inline int is_fstree(u64 rootid)
 {
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index 13ae7b04790e..da7419ed01bb 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -233,22 +233,26 @@ int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
         return 0;
 }
 
-int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
+int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
+                            struct btrfs_delayed_ref_root *delayed_refs,
                             u64 seq)
 {
         struct seq_list *elem;
-
-        assert_spin_locked(&delayed_refs->lock);
-        if (list_empty(&delayed_refs->seq_head))
-                return 0;
-
-        elem = list_first_entry(&delayed_refs->seq_head, struct seq_list, list);
-        if (seq >= elem->seq) {
-                pr_debug("holding back delayed_ref %llu, lowest is %llu (%p)\n",
-                         seq, elem->seq, delayed_refs);
-                return 1;
+        int ret = 0;
+
+        spin_lock(&fs_info->tree_mod_seq_lock);
+        if (!list_empty(&fs_info->tree_mod_seq_list)) {
+                elem = list_first_entry(&fs_info->tree_mod_seq_list,
+                                        struct seq_list, list);
+                if (seq >= elem->seq) {
+                        pr_debug("holding back delayed_ref %llu, lowest is "
+                                 "%llu (%p)\n", seq, elem->seq, delayed_refs);
+                        ret = 1;
+                }
         }
-        return 0;
+
+        spin_unlock(&fs_info->tree_mod_seq_lock);
+        return ret;
 }
 
 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
@@ -525,8 +529,8 @@ static noinline void add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
         ref->is_head = 0;
         ref->in_tree = 1;
 
-        if (is_fstree(ref_root))
-                seq = inc_delayed_seq(delayed_refs);
+        if (need_ref_seq(for_cow, ref_root))
+                seq = btrfs_get_tree_mod_seq(fs_info, &trans->delayed_ref_elem);
         ref->seq = seq;
 
         full_ref = btrfs_delayed_node_to_tree_ref(ref);
@@ -584,8 +588,8 @@ static noinline void add_delayed_data_ref(struct btrfs_fs_info *fs_info,
         ref->is_head = 0;
         ref->in_tree = 1;
 
-        if (is_fstree(ref_root))
-                seq = inc_delayed_seq(delayed_refs);
+        if (need_ref_seq(for_cow, ref_root))
+                seq = btrfs_get_tree_mod_seq(fs_info, &trans->delayed_ref_elem);
         ref->seq = seq;
 
         full_ref = btrfs_delayed_node_to_data_ref(ref);
@@ -658,10 +662,12 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
         add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
                                    num_bytes, parent, ref_root, level, action,
                                    for_cow);
-        if (!is_fstree(ref_root) &&
-            waitqueue_active(&delayed_refs->seq_wait))
-                wake_up(&delayed_refs->seq_wait);
+        if (!need_ref_seq(for_cow, ref_root) &&
+            waitqueue_active(&fs_info->tree_mod_seq_wait))
+                wake_up(&fs_info->tree_mod_seq_wait);
         spin_unlock(&delayed_refs->lock);
+        if (need_ref_seq(for_cow, ref_root))
+                btrfs_qgroup_record_ref(trans, &ref->node, extent_op);
 
         return 0;
 }
@@ -707,10 +713,12 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
         add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
                                    num_bytes, parent, ref_root, owner, offset,
                                    action, for_cow);
-        if (!is_fstree(ref_root) &&
-            waitqueue_active(&delayed_refs->seq_wait))
-                wake_up(&delayed_refs->seq_wait);
+        if (!need_ref_seq(for_cow, ref_root) &&
+            waitqueue_active(&fs_info->tree_mod_seq_wait))
+                wake_up(&fs_info->tree_mod_seq_wait);
         spin_unlock(&delayed_refs->lock);
+        if (need_ref_seq(for_cow, ref_root))
+                btrfs_qgroup_record_ref(trans, &ref->node, extent_op);
 
         return 0;
 }
@@ -736,8 +744,8 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
                                    num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
                                    extent_op->is_data);
 
-        if (waitqueue_active(&delayed_refs->seq_wait))
-                wake_up(&delayed_refs->seq_wait);
+        if (waitqueue_active(&fs_info->tree_mod_seq_wait))
+                wake_up(&fs_info->tree_mod_seq_wait);
         spin_unlock(&delayed_refs->lock);
         return 0;
 }
diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
index 413927fb9957..0d7c90c366b6 100644
--- a/fs/btrfs/delayed-ref.h
+++ b/fs/btrfs/delayed-ref.h
@@ -139,26 +139,6 @@ struct btrfs_delayed_ref_root {
         int flushing;
 
         u64 run_delayed_start;
-
-        /*
-         * seq number of delayed refs. We need to know if a backref was being
-         * added before the currently processed ref or afterwards.
-         */
-        u64 seq;
-
-        /*
-         * seq_list holds a list of all seq numbers that are currently being
-         * added to the list. While walking backrefs (btrfs_find_all_roots,
-         * qgroups), which might take some time, no newer ref must be processed,
-         * as it might influence the outcome of the walk.
-         */
-        struct list_head seq_head;
-
-        /*
-         * when the only refs we have in the list must not be processed, we want
-         * to wait for more refs to show up or for the end of backref walking.
-         */
-        wait_queue_head_t seq_wait;
 };
 
 static inline void btrfs_put_delayed_ref(struct btrfs_delayed_ref_node *ref)
@@ -195,34 +175,28 @@ int btrfs_delayed_ref_lock(struct btrfs_trans_handle *trans,
 int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
                            struct list_head *cluster, u64 search_start);
 
-static inline u64 inc_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs)
-{
-        assert_spin_locked(&delayed_refs->lock);
-        ++delayed_refs->seq;
-        return delayed_refs->seq;
-}
+int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info,
+                            struct btrfs_delayed_ref_root *delayed_refs,
+                            u64 seq);
 
-static inline void
-btrfs_get_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
-                      struct seq_list *elem)
+/*
+ * delayed refs with a ref_seq > 0 must be held back during backref walking.
+ * this only applies to items in one of the fs-trees. for_cow items never need
+ * to be held back, so they won't get a ref_seq number.
+ */
+static inline int need_ref_seq(int for_cow, u64 rootid)
 {
-        assert_spin_locked(&delayed_refs->lock);
-        elem->seq = delayed_refs->seq;
-        list_add_tail(&elem->list, &delayed_refs->seq_head);
-}
+        if (for_cow)
+                return 0;
 
-static inline void
-btrfs_put_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
-                      struct seq_list *elem)
-{
-        spin_lock(&delayed_refs->lock);
-        list_del(&elem->list);
-        wake_up(&delayed_refs->seq_wait);
-        spin_unlock(&delayed_refs->lock);
-}
+        if (rootid == BTRFS_FS_TREE_OBJECTID)
+                return 1;
 
-int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
-                            u64 seq);
+        if ((s64)rootid >= (s64)BTRFS_FIRST_FREE_OBJECTID)
+                return 1;
+
+        return 0;
+}
 
 /*
  * a node might live in a head or a regular ref, this lets you
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 1a4a2a975926..05f4fb6e0607 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1225,6 +1225,82 @@ static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info)
         return root;
 }
 
+struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
+                                     struct btrfs_fs_info *fs_info,
+                                     u64 objectid)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_root *tree_root = fs_info->tree_root;
+        struct btrfs_root *root;
+        struct btrfs_key key;
+        int ret = 0;
+        u64 bytenr;
+
+        root = btrfs_alloc_root(fs_info);
+        if (!root)
+                return ERR_PTR(-ENOMEM);
+
+        __setup_root(tree_root->nodesize, tree_root->leafsize,
+                     tree_root->sectorsize, tree_root->stripesize,
+                     root, fs_info, objectid);
+        root->root_key.objectid = objectid;
+        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
+        root->root_key.offset = 0;
+
+        leaf = btrfs_alloc_free_block(trans, root, root->leafsize,
+                                      0, objectid, NULL, 0, 0, 0);
+        if (IS_ERR(leaf)) {
+                ret = PTR_ERR(leaf);
+                goto fail;
+        }
+
+        bytenr = leaf->start;
+        memset_extent_buffer(leaf, 0, 0, sizeof(struct btrfs_header));
+        btrfs_set_header_bytenr(leaf, leaf->start);
+        btrfs_set_header_generation(leaf, trans->transid);
+        btrfs_set_header_backref_rev(leaf, BTRFS_MIXED_BACKREF_REV);
+        btrfs_set_header_owner(leaf, objectid);
+        root->node = leaf;
+
+        write_extent_buffer(leaf, fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(leaf),
+                            BTRFS_FSID_SIZE);
+        write_extent_buffer(leaf, fs_info->chunk_tree_uuid,
+                            (unsigned long)btrfs_header_chunk_tree_uuid(leaf),
+                            BTRFS_UUID_SIZE);
+        btrfs_mark_buffer_dirty(leaf);
+
+        root->commit_root = btrfs_root_node(root);
+        root->track_dirty = 1;
+
+
+        root->root_item.flags = 0;
+        root->root_item.byte_limit = 0;
+        btrfs_set_root_bytenr(&root->root_item, leaf->start);
+        btrfs_set_root_generation(&root->root_item, trans->transid);
+        btrfs_set_root_level(&root->root_item, 0);
+        btrfs_set_root_refs(&root->root_item, 1);
+        btrfs_set_root_used(&root->root_item, leaf->len);
+        btrfs_set_root_last_snapshot(&root->root_item, 0);
+        btrfs_set_root_dirid(&root->root_item, 0);
+        root->root_item.drop_level = 0;
+
+        key.objectid = objectid;
+        key.type = BTRFS_ROOT_ITEM_KEY;
+        key.offset = 0;
+        ret = btrfs_insert_root(trans, tree_root, &key, &root->root_item);
+        if (ret)
+                goto fail;
+
+        btrfs_tree_unlock(leaf);
+
+fail:
+        if (ret)
+                return ERR_PTR(ret);
+
+        return root;
+}
+
 static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
                                          struct btrfs_fs_info *fs_info)
 {
@@ -1396,6 +1472,9 @@ struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
                 return fs_info->dev_root;
         if (location->objectid == BTRFS_CSUM_TREE_OBJECTID)
                 return fs_info->csum_root;
+        if (location->objectid == BTRFS_QUOTA_TREE_OBJECTID)
+                return fs_info->quota_root ? fs_info->quota_root :
+                                             ERR_PTR(-ENOENT);
 again:
         spin_lock(&fs_info->fs_roots_radix_lock);
         root = radix_tree_lookup(&fs_info->fs_roots_radix,
@@ -1823,6 +1902,10 @@ static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
         free_extent_buffer(info->extent_root->commit_root);
         free_extent_buffer(info->csum_root->node);
         free_extent_buffer(info->csum_root->commit_root);
+        if (info->quota_root) {
+                free_extent_buffer(info->quota_root->node);
+                free_extent_buffer(info->quota_root->commit_root);
+        }
 
         info->tree_root->node = NULL;
         info->tree_root->commit_root = NULL;
@@ -1832,6 +1915,10 @@ static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
         info->extent_root->commit_root = NULL;
         info->csum_root->node = NULL;
         info->csum_root->commit_root = NULL;
+        if (info->quota_root) {
+                info->quota_root->node = NULL;
+                info->quota_root->commit_root = NULL;
+        }
 
         if (chunk_root) {
                 free_extent_buffer(info->chunk_root->node);
@@ -1862,6 +1949,7 @@ int open_ctree(struct super_block *sb,
         struct btrfs_root *csum_root;
         struct btrfs_root *chunk_root;
         struct btrfs_root *dev_root;
+        struct btrfs_root *quota_root;
         struct btrfs_root *log_tree_root;
         int ret;
         int err = -EINVAL;
@@ -1873,9 +1961,10 @@ int open_ctree(struct super_block *sb,
         csum_root = fs_info->csum_root = btrfs_alloc_root(fs_info);
         chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info);
         dev_root = fs_info->dev_root = btrfs_alloc_root(fs_info);
+        quota_root = fs_info->quota_root = btrfs_alloc_root(fs_info);
 
         if (!tree_root || !extent_root || !csum_root ||
-            !chunk_root || !dev_root) {
+            !chunk_root || !dev_root || !quota_root) {
                 err = -ENOMEM;
                 goto fail;
         }
@@ -1944,6 +2033,8 @@ int open_ctree(struct super_block *sb,
         fs_info->free_chunk_space = 0;
         fs_info->tree_mod_log = RB_ROOT;
 
+        init_waitqueue_head(&fs_info->tree_mod_seq_wait);
+
         /* readahead state */
         INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_WAIT);
         spin_lock_init(&fs_info->reada_lock);
@@ -2032,6 +2123,13 @@ int open_ctree(struct super_block *sb,
         init_rwsem(&fs_info->cleanup_work_sem);
         init_rwsem(&fs_info->subvol_sem);
 
+        spin_lock_init(&fs_info->qgroup_lock);
+        fs_info->qgroup_tree = RB_ROOT;
+        INIT_LIST_HEAD(&fs_info->dirty_qgroups);
+        fs_info->qgroup_seq = 1;
+        fs_info->quota_enabled = 0;
+        fs_info->pending_quota_state = 0;
+
         btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
         btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
 
@@ -2356,6 +2454,17 @@ retry_root_backup:
                 goto recovery_tree_root;
         csum_root->track_dirty = 1;
 
+        ret = find_and_setup_root(tree_root, fs_info,
+                                  BTRFS_QUOTA_TREE_OBJECTID, quota_root);
+        if (ret) {
+                kfree(quota_root);
+                quota_root = fs_info->quota_root = NULL;
+        } else {
+                quota_root->track_dirty = 1;
+                fs_info->quota_enabled = 1;
+                fs_info->pending_quota_state = 1;
+        }
+
         fs_info->generation = generation;
         fs_info->last_trans_committed = generation;
 
@@ -2415,6 +2524,9 @@ retry_root_backup:
                                " integrity check module %s\n", sb->s_id);
         }
 #endif
+        ret = btrfs_read_qgroup_config(fs_info);
+        if (ret)
+                goto fail_trans_kthread;
 
         /* do not make disk changes in broken FS */
         if (btrfs_super_log_root(disk_super) != 0 &&
@@ -2425,7 +2537,7 @@ retry_root_backup:
                         printk(KERN_WARNING "Btrfs log replay required "
                                "on RO media\n");
                         err = -EIO;
-                        goto fail_trans_kthread;
+                        goto fail_qgroup;
                 }
                 blocksize =
                      btrfs_level_size(tree_root,
@@ -2434,7 +2546,7 @@ retry_root_backup:
                 log_tree_root = btrfs_alloc_root(fs_info);
                 if (!log_tree_root) {
                         err = -ENOMEM;
-                        goto fail_trans_kthread;
+                        goto fail_qgroup;
                 }
 
                 __setup_root(nodesize, leafsize, sectorsize, stripesize,
@@ -2474,7 +2586,7 @@ retry_root_backup:
                         printk(KERN_WARNING
                                "btrfs: failed to recover relocation\n");
                         err = -EINVAL;
-                        goto fail_trans_kthread;
+                        goto fail_qgroup;
                 }
         }
 
@@ -2484,10 +2596,10 @@ retry_root_backup:
 
         fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
         if (!fs_info->fs_root)
-                goto fail_trans_kthread;
+                goto fail_qgroup;
         if (IS_ERR(fs_info->fs_root)) {
                 err = PTR_ERR(fs_info->fs_root);
-                goto fail_trans_kthread;
+                goto fail_qgroup;
         }
 
         if (sb->s_flags & MS_RDONLY)
@@ -2511,6 +2623,8 @@ retry_root_backup:
 
         return 0;
 
+fail_qgroup:
+        btrfs_free_qgroup_config(fs_info);
 fail_trans_kthread:
         kthread_stop(fs_info->transaction_kthread);
 fail_cleaner:
@@ -3109,6 +3223,8 @@ int close_ctree(struct btrfs_root *root)
         fs_info->closing = 2;
         smp_mb();
 
+        btrfs_free_qgroup_config(root->fs_info);
+
         if (fs_info->delalloc_bytes) {
                 printk(KERN_INFO "btrfs: at unmount delalloc count %llu\n",
                        (unsigned long long)fs_info->delalloc_bytes);
@@ -3128,6 +3244,10 @@ int close_ctree(struct btrfs_root *root)
         free_extent_buffer(fs_info->dev_root->commit_root);
         free_extent_buffer(fs_info->csum_root->node);
         free_extent_buffer(fs_info->csum_root->commit_root);
+        if (fs_info->quota_root) {
+                free_extent_buffer(fs_info->quota_root->node);
+                free_extent_buffer(fs_info->quota_root->commit_root);
+        }
 
         btrfs_free_block_groups(fs_info);
 
@@ -3258,7 +3378,7 @@ int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
         return btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
 }
 
-static int btree_lock_page_hook(struct page *page, void *data,
+int btree_lock_page_hook(struct page *page, void *data,
                                 void (*flush_fn)(void *))
 {
         struct inode *inode = page->mapping->host;
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index 05b3fab39f7e..95e147eea239 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -89,6 +89,12 @@ int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
 int btrfs_cleanup_transaction(struct btrfs_root *root);
 void btrfs_cleanup_one_transaction(struct btrfs_transaction *trans,
                                   struct btrfs_root *root);
+void btrfs_abort_devices(struct btrfs_root *root);
+struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
+                                     struct btrfs_fs_info *fs_info,
+                                     u64 objectid);
+int btree_lock_page_hook(struct page *page, void *data,
+                                void (*flush_fn)(void *));
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 void btrfs_init_lockdep(void);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 71b2d1c7da69..44f06201f376 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -34,6 +34,8 @@
 #include "locking.h"
 #include "free-space-cache.h"
 
+#undef SCRAMBLE_DELAYED_REFS
+
 /*
  * control flags for do_chunk_alloc's force field
  * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk
@@ -2217,6 +2219,7 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
         struct btrfs_delayed_ref_node *ref;
         struct btrfs_delayed_ref_head *locked_ref = NULL;
         struct btrfs_delayed_extent_op *extent_op;
+        struct btrfs_fs_info *fs_info = root->fs_info;
         int ret;
         int count = 0;
         int must_insert_reserved = 0;
@@ -2255,7 +2258,7 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
                 ref = select_delayed_ref(locked_ref);
 
                 if (ref && ref->seq &&
-                    btrfs_check_delayed_seq(delayed_refs, ref->seq)) {
+                    btrfs_check_delayed_seq(fs_info, delayed_refs, ref->seq)) {
                         /*
                          * there are still refs with lower seq numbers in the
                          * process of being added. Don't run this ref yet.
@@ -2337,7 +2340,7 @@ static noinline int run_clustered_refs(struct btrfs_trans_handle *trans,
                 }
 
 next:
-                do_chunk_alloc(trans, root->fs_info->extent_root,
+                do_chunk_alloc(trans, fs_info->extent_root,
                                2 * 1024 * 1024,
                                btrfs_get_alloc_profile(root, 0),
                                CHUNK_ALLOC_NO_FORCE);
@@ -2347,21 +2350,99 @@ next:
         return count;
 }
 
-static void wait_for_more_refs(struct btrfs_delayed_ref_root *delayed_refs,
+static void wait_for_more_refs(struct btrfs_fs_info *fs_info,
+                               struct btrfs_delayed_ref_root *delayed_refs,
                                unsigned long num_refs,
                                struct list_head *first_seq)
 {
         spin_unlock(&delayed_refs->lock);
         pr_debug("waiting for more refs (num %ld, first %p)\n",
                  num_refs, first_seq);
-        wait_event(delayed_refs->seq_wait,
+        wait_event(fs_info->tree_mod_seq_wait,
                    num_refs != delayed_refs->num_entries ||
-                   delayed_refs->seq_head.next != first_seq);
+                   fs_info->tree_mod_seq_list.next != first_seq);
         pr_debug("done waiting for more refs (num %ld, first %p)\n",
-                 delayed_refs->num_entries, delayed_refs->seq_head.next);
+                 delayed_refs->num_entries, fs_info->tree_mod_seq_list.next);
         spin_lock(&delayed_refs->lock);
 }
 
+#ifdef SCRAMBLE_DELAYED_REFS
+/*
+ * Normally delayed refs get processed in ascending bytenr order. This
+ * correlates in most cases to the order added. To expose dependencies on this
+ * order, we start to process the tree in the middle instead of the beginning
+ */
+static u64 find_middle(struct rb_root *root)
+{
+        struct rb_node *n = root->rb_node;
+        struct btrfs_delayed_ref_node *entry;
+        int alt = 1;
+        u64 middle;
+        u64 first = 0, last = 0;
+
+        n = rb_first(root);
+        if (n) {
+                entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
+                first = entry->bytenr;
+        }
+        n = rb_last(root);
+        if (n) {
+                entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
+                last = entry->bytenr;
+        }
+        n = root->rb_node;
+
+        while (n) {
+                entry = rb_entry(n, struct btrfs_delayed_ref_node, rb_node);
+                WARN_ON(!entry->in_tree);
+
+                middle = entry->bytenr;
+
+                if (alt)
+                        n = n->rb_left;
+                else
+                        n = n->rb_right;
+
+                alt = 1 - alt;
+        }
+        return middle;
+}
+#endif
+
+int btrfs_delayed_refs_qgroup_accounting(struct btrfs_trans_handle *trans,
+                                         struct btrfs_fs_info *fs_info)
+{
+        struct qgroup_update *qgroup_update;
+        int ret = 0;
+
+        if (list_empty(&trans->qgroup_ref_list) !=
+            !trans->delayed_ref_elem.seq) {
+                /* list without seq or seq without list */
+                printk(KERN_ERR "btrfs: qgroup accounting update error, list is%s empty, seq is %llu\n",
+                        list_empty(&trans->qgroup_ref_list) ? "" : " not",
+                        trans->delayed_ref_elem.seq);
+                BUG();
+        }
+
+        if (!trans->delayed_ref_elem.seq)
+                return 0;
+
+        while (!list_empty(&trans->qgroup_ref_list)) {
+                qgroup_update = list_first_entry(&trans->qgroup_ref_list,
+                                                 struct qgroup_update, list);
+                list_del(&qgroup_update->list);
+                if (!ret)
+                        ret = btrfs_qgroup_account_ref(
+                                        trans, fs_info, qgroup_update->node,
+                                        qgroup_update->extent_op);
+                kfree(qgroup_update);
+        }
+
+        btrfs_put_tree_mod_seq(fs_info, &trans->delayed_ref_elem);
+
+        return ret;
+}
+
 /*
  * this starts processing the delayed reference count updates and
  * extent insertions we have queued up so far.  count can be
@@ -2398,11 +2479,18 @@ int btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
                        2 * 1024 * 1024, btrfs_get_alloc_profile(root, 0),
                        CHUNK_ALLOC_NO_FORCE);
 
+        btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
+
         delayed_refs = &trans->transaction->delayed_refs;
         INIT_LIST_HEAD(&cluster);
 again:
         consider_waiting = 0;
         spin_lock(&delayed_refs->lock);
+
+#ifdef SCRAMBLE_DELAYED_REFS
+        delayed_refs->run_delayed_start = find_middle(&delayed_refs->root);
+#endif
+
         if (count == 0) {
                 count = delayed_refs->num_entries * 2;
                 run_most = 1;
@@ -2437,7 +2525,7 @@ again:
                                 num_refs = delayed_refs->num_entries;
                                 first_seq = root->fs_info->tree_mod_seq_list.next;
                         } else {
-                                wait_for_more_refs(delayed_refs,
+                                wait_for_more_refs(root->fs_info, delayed_refs,
                                                    num_refs, first_seq);
                                 /*
                                  * after waiting, things have changed. we
@@ -2502,6 +2590,7 @@ again:
         }
 out:
         spin_unlock(&delayed_refs->lock);
+        assert_qgroups_uptodate(trans);
         return 0;
 }
 
@@ -4479,6 +4568,13 @@ int btrfs_delalloc_reserve_metadata(struct inode *inode, u64 num_bytes)
         csum_bytes = BTRFS_I(inode)->csum_bytes;
         spin_unlock(&BTRFS_I(inode)->lock);
 
+        if (root->fs_info->quota_enabled) {
+                ret = btrfs_qgroup_reserve(root, num_bytes +
+                                           nr_extents * root->leafsize);
+                if (ret)
+                        return ret;
+        }
+
         ret = reserve_metadata_bytes(root, block_rsv, to_reserve, flush);
         if (ret) {
                 u64 to_free = 0;
@@ -4557,6 +4653,11 @@ void btrfs_delalloc_release_metadata(struct inode *inode, u64 num_bytes)
 
         trace_btrfs_space_reservation(root->fs_info, "delalloc",
                                       btrfs_ino(inode), to_free, 0);
+        if (root->fs_info->quota_enabled) {
+                btrfs_qgroup_free(root, num_bytes +
+                                        dropped * root->leafsize);
+        }
+
         btrfs_block_rsv_release(root, &root->fs_info->delalloc_block_rsv,
                                 to_free);
 }
@@ -5193,8 +5294,8 @@ static noinline int check_ref_cleanup(struct btrfs_trans_handle *trans,
         rb_erase(&head->node.rb_node, &delayed_refs->root);
 
         delayed_refs->num_entries--;
-        if (waitqueue_active(&delayed_refs->seq_wait))
-                wake_up(&delayed_refs->seq_wait);
+        if (waitqueue_active(&root->fs_info->tree_mod_seq_wait))
+                wake_up(&root->fs_info->tree_mod_seq_wait);
 
         /*
          * we don't take a ref on the node because we're removing it from the
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 17facea6a51c..e54b663fd3aa 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -336,7 +336,8 @@ static noinline int btrfs_ioctl_fitrim(struct file *file, void __user *arg)
 static noinline int create_subvol(struct btrfs_root *root,
                                   struct dentry *dentry,
                                   char *name, int namelen,
-                                  u64 *async_transid)
+                                  u64 *async_transid,
+                                  struct btrfs_qgroup_inherit **inherit)
 {
         struct btrfs_trans_handle *trans;
         struct btrfs_key key;
@@ -368,6 +369,11 @@ static noinline int create_subvol(struct btrfs_root *root,
         if (IS_ERR(trans))
                 return PTR_ERR(trans);
 
+        ret = btrfs_qgroup_inherit(trans, root->fs_info, 0, objectid,
+                                   inherit ? *inherit : NULL);
+        if (ret)
+                goto fail;
+
         leaf = btrfs_alloc_free_block(trans, root, root->leafsize,
                                       0, objectid, NULL, 0, 0, 0);
         if (IS_ERR(leaf)) {
@@ -484,7 +490,7 @@ fail:
 
 static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
                            char *name, int namelen, u64 *async_transid,
-                           bool readonly)
+                           bool readonly, struct btrfs_qgroup_inherit **inherit)
 {
         struct inode *inode;
         struct btrfs_pending_snapshot *pending_snapshot;
@@ -502,6 +508,10 @@ static int create_snapshot(struct btrfs_root *root, struct dentry *dentry,
         pending_snapshot->dentry = dentry;
         pending_snapshot->root = root;
         pending_snapshot->readonly = readonly;
+        if (inherit) {
+                pending_snapshot->inherit = *inherit;
+                *inherit = NULL;        /* take responsibility to free it */
+        }
 
         trans = btrfs_start_transaction(root->fs_info->extent_root, 5);
         if (IS_ERR(trans)) {
@@ -635,7 +645,8 @@ static inline int btrfs_may_create(struct inode *dir, struct dentry *child)
 static noinline int btrfs_mksubvol(struct path *parent,
                                    char *name, int namelen,
                                    struct btrfs_root *snap_src,
-                                   u64 *async_transid, bool readonly)
+                                   u64 *async_transid, bool readonly,
+                                   struct btrfs_qgroup_inherit **inherit)
 {
         struct inode *dir  = parent->dentry->d_inode;
         struct dentry *dentry;
@@ -662,11 +673,11 @@ static noinline int btrfs_mksubvol(struct path *parent,
                 goto out_up_read;
 
         if (snap_src) {
-                error = create_snapshot(snap_src, dentry,
-                                        name, namelen, async_transid, readonly);
+                error = create_snapshot(snap_src, dentry, name, namelen,
+                                        async_transid, readonly, inherit);
         } else {
                 error = create_subvol(BTRFS_I(dir)->root, dentry,
-                                      name, namelen, async_transid);
+                                      name, namelen, async_transid, inherit);
         }
         if (!error)
                 fsnotify_mkdir(dir, dentry);
@@ -1375,11 +1386,9 @@ out:
 }
 
 static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
-                                                    char *name,
-                                                    unsigned long fd,
-                                                    int subvol,
-                                                    u64 *transid,
-                                                    bool readonly)
+                                char *name, unsigned long fd, int subvol,
+                                u64 *transid, bool readonly,
+                                struct btrfs_qgroup_inherit **inherit)
 {
         struct file *src_file;
         int namelen;
@@ -1403,7 +1412,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
 
         if (subvol) {
                 ret = btrfs_mksubvol(&file->f_path, name, namelen,
-                                     NULL, transid, readonly);
+                                     NULL, transid, readonly, inherit);
         } else {
                 struct inode *src_inode;
                 src_file = fget(fd);
@@ -1422,7 +1431,7 @@ static noinline int btrfs_ioctl_snap_create_transid(struct file *file,
                 }
                 ret = btrfs_mksubvol(&file->f_path, name, namelen,
                                      BTRFS_I(src_inode)->root,
-                                     transid, readonly);
+                                     transid, readonly, inherit);
                 fput(src_file);
         }
 out_drop_write:
@@ -1444,7 +1453,7 @@ static noinline int btrfs_ioctl_snap_create(struct file *file,
 
         ret = btrfs_ioctl_snap_create_transid(file, vol_args->name,
                                               vol_args->fd, subvol,
-                                              NULL, false);
+                                              NULL, false, NULL);
 
         kfree(vol_args);
         return ret;
@@ -1458,6 +1467,7 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
         u64 transid = 0;
         u64 *ptr = NULL;
         bool readonly = false;
+        struct btrfs_qgroup_inherit *inherit = NULL;
 
         vol_args = memdup_user(arg, sizeof(*vol_args));
         if (IS_ERR(vol_args))
@@ -1465,7 +1475,8 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
         vol_args->name[BTRFS_SUBVOL_NAME_MAX] = '\0';
 
         if (vol_args->flags &
-            ~(BTRFS_SUBVOL_CREATE_ASYNC | BTRFS_SUBVOL_RDONLY)) {
+            ~(BTRFS_SUBVOL_CREATE_ASYNC | BTRFS_SUBVOL_RDONLY |
+              BTRFS_SUBVOL_QGROUP_INHERIT)) {
                 ret = -EOPNOTSUPP;
                 goto out;
         }
@@ -1474,10 +1485,21 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
                 ptr = &transid;
         if (vol_args->flags & BTRFS_SUBVOL_RDONLY)
                 readonly = true;
+        if (vol_args->flags & BTRFS_SUBVOL_QGROUP_INHERIT) {
+                if (vol_args->size > PAGE_CACHE_SIZE) {
+                        ret = -EINVAL;
+                        goto out;
+                }
+                inherit = memdup_user(vol_args->qgroup_inherit, vol_args->size);
+                if (IS_ERR(inherit)) {
+                        ret = PTR_ERR(inherit);
+                        goto out;
+                }
+        }
 
         ret = btrfs_ioctl_snap_create_transid(file, vol_args->name,
-                                              vol_args->fd, subvol,
-                                              ptr, readonly);
+                                              vol_args->fd, subvol, ptr,
+                                              readonly, &inherit);
 
         if (ret == 0 && ptr &&
             copy_to_user(arg +
@@ -1486,6 +1508,7 @@ static noinline int btrfs_ioctl_snap_create_v2(struct file *file,
                 ret = -EFAULT;
 out:
         kfree(vol_args);
+        kfree(inherit);
         return ret;
 }
 
@@ -3401,6 +3424,183 @@ out:
         return ret;
 }
 
+static long btrfs_ioctl_quota_ctl(struct btrfs_root *root, void __user *arg)
+{
+        struct btrfs_ioctl_quota_ctl_args *sa;
+        struct btrfs_trans_handle *trans = NULL;
+        int ret;
+        int err;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (root->fs_info->sb->s_flags & MS_RDONLY)
+                return -EROFS;
+
+        sa = memdup_user(arg, sizeof(*sa));
+        if (IS_ERR(sa))
+                return PTR_ERR(sa);
+
+        if (sa->cmd != BTRFS_QUOTA_CTL_RESCAN) {
+                trans = btrfs_start_transaction(root, 2);
+                if (IS_ERR(trans)) {
+                        ret = PTR_ERR(trans);
+                        goto out;
+                }
+        }
+
+        switch (sa->cmd) {
+        case BTRFS_QUOTA_CTL_ENABLE:
+                ret = btrfs_quota_enable(trans, root->fs_info);
+                break;
+        case BTRFS_QUOTA_CTL_DISABLE:
+                ret = btrfs_quota_disable(trans, root->fs_info);
+                break;
+        case BTRFS_QUOTA_CTL_RESCAN:
+                ret = btrfs_quota_rescan(root->fs_info);
+                break;
+        default:
+                ret = -EINVAL;
+                break;
+        }
+
+        if (copy_to_user(arg, sa, sizeof(*sa)))
+                ret = -EFAULT;
+
+        if (trans) {
+                err = btrfs_commit_transaction(trans, root);
+                if (err && !ret)
+                        ret = err;
+        }
+
+out:
+        kfree(sa);
+        return ret;
+}
+
+static long btrfs_ioctl_qgroup_assign(struct btrfs_root *root, void __user *arg)
+{
+        struct btrfs_ioctl_qgroup_assign_args *sa;
+        struct btrfs_trans_handle *trans;
+        int ret;
+        int err;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (root->fs_info->sb->s_flags & MS_RDONLY)
+                return -EROFS;
+
+        sa = memdup_user(arg, sizeof(*sa));
+        if (IS_ERR(sa))
+                return PTR_ERR(sa);
+
+        trans = btrfs_join_transaction(root);
+        if (IS_ERR(trans)) {
+                ret = PTR_ERR(trans);
+                goto out;
+        }
+
+        /* FIXME: check if the IDs really exist */
+        if (sa->assign) {
+                ret = btrfs_add_qgroup_relation(trans, root->fs_info,
+                                                sa->src, sa->dst);
+        } else {
+                ret = btrfs_del_qgroup_relation(trans, root->fs_info,
+                                                sa->src, sa->dst);
+        }
+
+        err = btrfs_end_transaction(trans, root);
+        if (err && !ret)
+                ret = err;
+
+out:
+        kfree(sa);
+        return ret;
+}
+
+static long btrfs_ioctl_qgroup_create(struct btrfs_root *root, void __user *arg)
+{
+        struct btrfs_ioctl_qgroup_create_args *sa;
+        struct btrfs_trans_handle *trans;
+        int ret;
+        int err;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (root->fs_info->sb->s_flags & MS_RDONLY)
+                return -EROFS;
+
+        sa = memdup_user(arg, sizeof(*sa));
+        if (IS_ERR(sa))
+                return PTR_ERR(sa);
+
+        trans = btrfs_join_transaction(root);
+        if (IS_ERR(trans)) {
+                ret = PTR_ERR(trans);
+                goto out;
+        }
+
+        /* FIXME: check if the IDs really exist */
+        if (sa->create) {
+                ret = btrfs_create_qgroup(trans, root->fs_info, sa->qgroupid,
+                                          NULL);
+        } else {
+                ret = btrfs_remove_qgroup(trans, root->fs_info, sa->qgroupid);
+        }
+
+        err = btrfs_end_transaction(trans, root);
+        if (err && !ret)
+                ret = err;
+
+out:
+        kfree(sa);
+        return ret;
+}
+
+static long btrfs_ioctl_qgroup_limit(struct btrfs_root *root, void __user *arg)
+{
+        struct btrfs_ioctl_qgroup_limit_args *sa;
+        struct btrfs_trans_handle *trans;
+        int ret;
+        int err;
+        u64 qgroupid;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if (root->fs_info->sb->s_flags & MS_RDONLY)
+                return -EROFS;
+
+        sa = memdup_user(arg, sizeof(*sa));
+        if (IS_ERR(sa))
+                return PTR_ERR(sa);
+
+        trans = btrfs_join_transaction(root);
+        if (IS_ERR(trans)) {
+                ret = PTR_ERR(trans);
+                goto out;
+        }
+
+        qgroupid = sa->qgroupid;
+        if (!qgroupid) {
+                /* take the current subvol as qgroup */
+                qgroupid = root->root_key.objectid;
+        }
+
+        /* FIXME: check if the IDs really exist */
+        ret = btrfs_limit_qgroup(trans, root->fs_info, qgroupid, &sa->lim);
+
+        err = btrfs_end_transaction(trans, root);
+        if (err && !ret)
+                ret = err;
+
+out:
+        kfree(sa);
+        return ret;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
                 cmd, unsigned long arg)
 {
@@ -3422,6 +3622,8 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_snap_create_v2(file, argp, 0);
         case BTRFS_IOC_SUBVOL_CREATE:
                 return btrfs_ioctl_snap_create(file, argp, 1);
+        case BTRFS_IOC_SUBVOL_CREATE_V2:
+                return btrfs_ioctl_snap_create_v2(file, argp, 1);
         case BTRFS_IOC_SNAP_DESTROY:
                 return btrfs_ioctl_snap_destroy(file, argp);
         case BTRFS_IOC_SUBVOL_GETFLAGS:
@@ -3485,6 +3687,14 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_balance_progress(root, argp);
         case BTRFS_IOC_GET_DEV_STATS:
                 return btrfs_ioctl_get_dev_stats(root, argp);
+        case BTRFS_IOC_QUOTA_CTL:
+                return btrfs_ioctl_quota_ctl(root, argp);
+        case BTRFS_IOC_QGROUP_ASSIGN:
+                return btrfs_ioctl_qgroup_assign(root, argp);
+        case BTRFS_IOC_QGROUP_CREATE:
+                return btrfs_ioctl_qgroup_create(root, argp);
+        case BTRFS_IOC_QGROUP_LIMIT:
+                return btrfs_ioctl_qgroup_limit(root, argp);
         }
 
         return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 4e3e5d342a2b..3f9701d571ea 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -32,15 +32,46 @@ struct btrfs_ioctl_vol_args {
 
 #define BTRFS_SUBVOL_CREATE_ASYNC       (1ULL << 0)
 #define BTRFS_SUBVOL_RDONLY             (1ULL << 1)
+#define BTRFS_SUBVOL_QGROUP_INHERIT     (1ULL << 2)
 #define BTRFS_FSID_SIZE 16
 #define BTRFS_UUID_SIZE 16
 
+#define BTRFS_QGROUP_INHERIT_SET_LIMITS (1ULL << 0)
+
+struct btrfs_qgroup_limit {
+        __u64   flags;
+        __u64   max_rfer;
+        __u64   max_excl;
+        __u64   rsv_rfer;
+        __u64   rsv_excl;
+};
+
+struct btrfs_qgroup_inherit {
+        __u64   flags;
+        __u64   num_qgroups;
+        __u64   num_ref_copies;
+        __u64   num_excl_copies;
+        struct btrfs_qgroup_limit lim;
+        __u64   qgroups[0];
+};
+
+struct btrfs_ioctl_qgroup_limit_args {
+        __u64   qgroupid;
+        struct btrfs_qgroup_limit lim;
+};
+
 #define BTRFS_SUBVOL_NAME_MAX 4039
 struct btrfs_ioctl_vol_args_v2 {
         __s64 fd;
         __u64 transid;
         __u64 flags;
-        __u64 unused[4];
+        union {
+                struct {
+                        __u64 size;
+                        struct btrfs_qgroup_inherit __user *qgroup_inherit;
+                };
+                __u64 unused[4];
+        };
         char name[BTRFS_SUBVOL_NAME_MAX + 1];
 };
 
@@ -299,6 +330,25 @@ struct btrfs_ioctl_get_dev_stats {
         __u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX]; /* pad to 1k */
 };
 
+#define BTRFS_QUOTA_CTL_ENABLE  1
+#define BTRFS_QUOTA_CTL_DISABLE 2
+#define BTRFS_QUOTA_CTL_RESCAN  3
+struct btrfs_ioctl_quota_ctl_args {
+        __u64 cmd;
+        __u64 status;
+};
+
+struct btrfs_ioctl_qgroup_assign_args {
+        __u64 assign;
+        __u64 src;
+        __u64 dst;
+};
+
+struct btrfs_ioctl_qgroup_create_args {
+        __u64 create;
+        __u64 qgroupid;
+};
+
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
                                    struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -343,6 +393,8 @@ struct btrfs_ioctl_get_dev_stats {
 #define BTRFS_IOC_WAIT_SYNC  _IOW(BTRFS_IOCTL_MAGIC, 22, __u64)
 #define BTRFS_IOC_SNAP_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 23, \
                                    struct btrfs_ioctl_vol_args_v2)
+#define BTRFS_IOC_SUBVOL_CREATE_V2 _IOW(BTRFS_IOCTL_MAGIC, 24, \
+                                   struct btrfs_ioctl_vol_args_v2)
 #define BTRFS_IOC_SUBVOL_GETFLAGS _IOR(BTRFS_IOCTL_MAGIC, 25, __u64)
 #define BTRFS_IOC_SUBVOL_SETFLAGS _IOW(BTRFS_IOCTL_MAGIC, 26, __u64)
 #define BTRFS_IOC_SCRUB _IOWR(BTRFS_IOCTL_MAGIC, 27, \
@@ -365,6 +417,14 @@ struct btrfs_ioctl_get_dev_stats {
                                         struct btrfs_ioctl_ino_path_args)
 #define BTRFS_IOC_DEVICES_READY _IOR(BTRFS_IOCTL_MAGIC, 39, \
                                      struct btrfs_ioctl_vol_args)
+#define BTRFS_IOC_QUOTA_CTL _IOWR(BTRFS_IOCTL_MAGIC, 40, \
+                               struct btrfs_ioctl_quota_ctl_args)
+#define BTRFS_IOC_QGROUP_ASSIGN _IOW(BTRFS_IOCTL_MAGIC, 41, \
+                               struct btrfs_ioctl_qgroup_assign_args)
+#define BTRFS_IOC_QGROUP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 42, \
+                               struct btrfs_ioctl_qgroup_create_args)
+#define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
+                               struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
                                       struct btrfs_ioctl_get_dev_stats)
 #endif
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
new file mode 100644
index 000000000000..bc424ae5a81a
--- /dev/null
+++ b/fs/btrfs/qgroup.c
@@ -0,0 +1,1571 @@
+/*
+ * Copyright (C) 2011 STRATO.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/sched.h>
+#include <linux/pagemap.h>
+#include <linux/writeback.h>
+#include <linux/blkdev.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+#include "ctree.h"
+#include "transaction.h"
+#include "disk-io.h"
+#include "locking.h"
+#include "ulist.h"
+#include "ioctl.h"
+#include "backref.h"
+
+/* TODO XXX FIXME
+ *  - subvol delete -> delete when ref goes to 0? delete limits also?
+ *  - reorganize keys
+ *  - compressed
+ *  - sync
+ *  - rescan
+ *  - copy also limits on subvol creation
+ *  - limit
+ *  - caches fuer ulists
+ *  - performance benchmarks
+ *  - check all ioctl parameters
+ */
+
+/*
+ * one struct for each qgroup, organized in fs_info->qgroup_tree.
+ */
+struct btrfs_qgroup {
+        u64 qgroupid;
+
+        /*
+         * state
+         */
+        u64 rfer;       /* referenced */
+        u64 rfer_cmpr;  /* referenced compressed */
+        u64 excl;       /* exclusive */
+        u64 excl_cmpr;  /* exclusive compressed */
+
+        /*
+         * limits
+         */
+        u64 lim_flags;  /* which limits are set */
+        u64 max_rfer;
+        u64 max_excl;
+        u64 rsv_rfer;
+        u64 rsv_excl;
+
+        /*
+         * reservation tracking
+         */
+        u64 reserved;
+
+        /*
+         * lists
+         */
+        struct list_head groups;  /* groups this group is member of */
+        struct list_head members; /* groups that are members of this group */
+        struct list_head dirty;   /* dirty groups */
+        struct rb_node node;      /* tree of qgroups */
+
+        /*
+         * temp variables for accounting operations
+         */
+        u64 tag;
+        u64 refcnt;
+};
+
+/*
+ * glue structure to represent the relations between qgroups.
+ */
+struct btrfs_qgroup_list {
+        struct list_head next_group;
+        struct list_head next_member;
+        struct btrfs_qgroup *group;
+        struct btrfs_qgroup *member;
+};
+
+/* must be called with qgroup_lock held */
+static struct btrfs_qgroup *find_qgroup_rb(struct btrfs_fs_info *fs_info,
+                                           u64 qgroupid)
+{
+        struct rb_node *n = fs_info->qgroup_tree.rb_node;
+        struct btrfs_qgroup *qgroup;
+
+        while (n) {
+                qgroup = rb_entry(n, struct btrfs_qgroup, node);
+                if (qgroup->qgroupid < qgroupid)
+                        n = n->rb_left;
+                else if (qgroup->qgroupid > qgroupid)
+                        n = n->rb_right;
+                else
+                        return qgroup;
+        }
+        return NULL;
+}
+
+/* must be called with qgroup_lock held */
+static struct btrfs_qgroup *add_qgroup_rb(struct btrfs_fs_info *fs_info,
+                                          u64 qgroupid)
+{
+        struct rb_node **p = &fs_info->qgroup_tree.rb_node;
+        struct rb_node *parent = NULL;
+        struct btrfs_qgroup *qgroup;
+
+        while (*p) {
+                parent = *p;
+                qgroup = rb_entry(parent, struct btrfs_qgroup, node);
+
+                if (qgroup->qgroupid < qgroupid)
+                        p = &(*p)->rb_left;
+                else if (qgroup->qgroupid > qgroupid)
+                        p = &(*p)->rb_right;
+                else
+                        return qgroup;
+        }
+
+        qgroup = kzalloc(sizeof(*qgroup), GFP_ATOMIC);
+        if (!qgroup)
+                return ERR_PTR(-ENOMEM);
+
+        qgroup->qgroupid = qgroupid;
+        INIT_LIST_HEAD(&qgroup->groups);
+        INIT_LIST_HEAD(&qgroup->members);
+        INIT_LIST_HEAD(&qgroup->dirty);
+
+        rb_link_node(&qgroup->node, parent, p);
+        rb_insert_color(&qgroup->node, &fs_info->qgroup_tree);
+
+        return qgroup;
+}
+
+/* must be called with qgroup_lock held */
+static int del_qgroup_rb(struct btrfs_fs_info *fs_info, u64 qgroupid)
+{
+        struct btrfs_qgroup *qgroup = find_qgroup_rb(fs_info, qgroupid);
+        struct btrfs_qgroup_list *list;
+
+        if (!qgroup)
+                return -ENOENT;
+
+        rb_erase(&qgroup->node, &fs_info->qgroup_tree);
+        list_del(&qgroup->dirty);
+
+        while (!list_empty(&qgroup->groups)) {
+                list = list_first_entry(&qgroup->groups,
+                                        struct btrfs_qgroup_list, next_group);
+                list_del(&list->next_group);
+                list_del(&list->next_member);
+                kfree(list);
+        }
+
+        while (!list_empty(&qgroup->members)) {
+                list = list_first_entry(&qgroup->members,
+                                        struct btrfs_qgroup_list, next_member);
+                list_del(&list->next_group);
+                list_del(&list->next_member);
+                kfree(list);
+        }
+        kfree(qgroup);
+
+        return 0;
+}
+
+/* must be called with qgroup_lock held */
+static int add_relation_rb(struct btrfs_fs_info *fs_info,
+                           u64 memberid, u64 parentid)
+{
+        struct btrfs_qgroup *member;
+        struct btrfs_qgroup *parent;
+        struct btrfs_qgroup_list *list;
+
+        member = find_qgroup_rb(fs_info, memberid);
+        parent = find_qgroup_rb(fs_info, parentid);
+        if (!member || !parent)
+                return -ENOENT;
+
+        list = kzalloc(sizeof(*list), GFP_ATOMIC);
+        if (!list)
+                return -ENOMEM;
+
+        list->group = parent;
+        list->member = member;
+        list_add_tail(&list->next_group, &member->groups);
+        list_add_tail(&list->next_member, &parent->members);
+
+        return 0;
+}
+
+/* must be called with qgroup_lock held */
+static int del_relation_rb(struct btrfs_fs_info *fs_info,
+                           u64 memberid, u64 parentid)
+{
+        struct btrfs_qgroup *member;
+        struct btrfs_qgroup *parent;
+        struct btrfs_qgroup_list *list;
+
+        member = find_qgroup_rb(fs_info, memberid);
+        parent = find_qgroup_rb(fs_info, parentid);
+        if (!member || !parent)
+                return -ENOENT;
+
+        list_for_each_entry(list, &member->groups, next_group) {
+                if (list->group == parent) {
+                        list_del(&list->next_group);
+                        list_del(&list->next_member);
+                        kfree(list);
+                        return 0;
+                }
+        }
+        return -ENOENT;
+}
+
+/*
+ * The full config is read in one go, only called from open_ctree()
+ * It doesn't use any locking, as at this point we're still single-threaded
+ */
+int btrfs_read_qgroup_config(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_key key;
+        struct btrfs_key found_key;
+        struct btrfs_root *quota_root = fs_info->quota_root;
+        struct btrfs_path *path = NULL;
+        struct extent_buffer *l;
+        int slot;
+        int ret = 0;
+        u64 flags = 0;
+
+        if (!fs_info->quota_enabled)
+                return 0;
+
+        path = btrfs_alloc_path();
+        if (!path) {
+                ret = -ENOMEM;
+                goto out;
+        }
+
+        /* default this to quota off, in case no status key is found */
+        fs_info->qgroup_flags = 0;
+
+        /*
+         * pass 1: read status, all qgroup infos and limits
+         */
+        key.objectid = 0;
+        key.type = 0;
+        key.offset = 0;
+        ret = btrfs_search_slot_for_read(quota_root, &key, path, 1, 1);
+        if (ret)
+                goto out;
+
+        while (1) {
+                struct btrfs_qgroup *qgroup;
+
+                slot = path->slots[0];
+                l = path->nodes[0];
+                btrfs_item_key_to_cpu(l, &found_key, slot);
+
+                if (found_key.type == BTRFS_QGROUP_STATUS_KEY) {
+                        struct btrfs_qgroup_status_item *ptr;
+
+                        ptr = btrfs_item_ptr(l, slot,
+                                             struct btrfs_qgroup_status_item);
+
+                        if (btrfs_qgroup_status_version(l, ptr) !=
+                            BTRFS_QGROUP_STATUS_VERSION) {
+                                printk(KERN_ERR
+                                 "btrfs: old qgroup version, quota disabled\n");
+                                goto out;
+                        }
+                        if (btrfs_qgroup_status_generation(l, ptr) !=
+                            fs_info->generation) {
+                                flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+                                printk(KERN_ERR
+                                        "btrfs: qgroup generation mismatch, "
+                                        "marked as inconsistent\n");
+                        }
+                        fs_info->qgroup_flags = btrfs_qgroup_status_flags(l,
+                                                                          ptr);
+                        /* FIXME read scan element */
+                        goto next1;
+                }
+
+                if (found_key.type != BTRFS_QGROUP_INFO_KEY &&
+                    found_key.type != BTRFS_QGROUP_LIMIT_KEY)
+                        goto next1;
+
+                qgroup = find_qgroup_rb(fs_info, found_key.offset);
+                if ((qgroup && found_key.type == BTRFS_QGROUP_INFO_KEY) ||
+                    (!qgroup && found_key.type == BTRFS_QGROUP_LIMIT_KEY)) {
+                        printk(KERN_ERR "btrfs: inconsitent qgroup config\n");
+                        flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+                }
+                if (!qgroup) {
+                        qgroup = add_qgroup_rb(fs_info, found_key.offset);
+                        if (IS_ERR(qgroup)) {
+                                ret = PTR_ERR(qgroup);
+                                goto out;
+                        }
+                }
+                switch (found_key.type) {
+                case BTRFS_QGROUP_INFO_KEY: {
+                        struct btrfs_qgroup_info_item *ptr;
+
+                        ptr = btrfs_item_ptr(l, slot,
+                                             struct btrfs_qgroup_info_item);
+                        qgroup->rfer = btrfs_qgroup_info_rfer(l, ptr);
+                        qgroup->rfer_cmpr = btrfs_qgroup_info_rfer_cmpr(l, ptr);
+                        qgroup->excl = btrfs_qgroup_info_excl(l, ptr);
+                        qgroup->excl_cmpr = btrfs_qgroup_info_excl_cmpr(l, ptr);
+                        /* generation currently unused */
+                        break;
+                }
+                case BTRFS_QGROUP_LIMIT_KEY: {
+                        struct btrfs_qgroup_limit_item *ptr;
+
+                        ptr = btrfs_item_ptr(l, slot,
+                                             struct btrfs_qgroup_limit_item);
+                        qgroup->lim_flags = btrfs_qgroup_limit_flags(l, ptr);
+                        qgroup->max_rfer = btrfs_qgroup_limit_max_rfer(l, ptr);
+                        qgroup->max_excl = btrfs_qgroup_limit_max_excl(l, ptr);
+                        qgroup->rsv_rfer = btrfs_qgroup_limit_rsv_rfer(l, ptr);
+                        qgroup->rsv_excl = btrfs_qgroup_limit_rsv_excl(l, ptr);
+                        break;
+                }
+                }
+next1:
+                ret = btrfs_next_item(quota_root, path);
+                if (ret < 0)
+                        goto out;
+                if (ret)
+                        break;
+        }
+        btrfs_release_path(path);
+
+        /*
+         * pass 2: read all qgroup relations
+         */
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_RELATION_KEY;
+        key.offset = 0;
+        ret = btrfs_search_slot_for_read(quota_root, &key, path, 1, 0);
+        if (ret)
+                goto out;
+        while (1) {
+                slot = path->slots[0];
+                l = path->nodes[0];
+                btrfs_item_key_to_cpu(l, &found_key, slot);
+
+                if (found_key.type != BTRFS_QGROUP_RELATION_KEY)
+                        goto next2;
+
+                if (found_key.objectid > found_key.offset) {
+                        /* parent <- member, not needed to build config */
+                        /* FIXME should we omit the key completely? */
+                        goto next2;
+                }
+
+                ret = add_relation_rb(fs_info, found_key.objectid,
+                                      found_key.offset);
+                if (ret)
+                        goto out;
+next2:
+                ret = btrfs_next_item(quota_root, path);
+                if (ret < 0)
+                        goto out;
+                if (ret)
+                        break;
+        }
+out:
+        fs_info->qgroup_flags |= flags;
+        if (!(fs_info->qgroup_flags & BTRFS_QGROUP_STATUS_FLAG_ON)) {
+                fs_info->quota_enabled = 0;
+                fs_info->pending_quota_state = 0;
+        }
+        btrfs_free_path(path);
+
+        return ret < 0 ? ret : 0;
+}
+
+/*
+ * This is only called from close_ctree() or open_ctree(), both in single-
+ * treaded paths. Clean up the in-memory structures. No locking needed.
+ */
+void btrfs_free_qgroup_config(struct btrfs_fs_info *fs_info)
+{
+        struct rb_node *n;
+        struct btrfs_qgroup *qgroup;
+        struct btrfs_qgroup_list *list;
+
+        while ((n = rb_first(&fs_info->qgroup_tree))) {
+                qgroup = rb_entry(n, struct btrfs_qgroup, node);
+                rb_erase(n, &fs_info->qgroup_tree);
+
+                WARN_ON(!list_empty(&qgroup->dirty));
+
+                while (!list_empty(&qgroup->groups)) {
+                        list = list_first_entry(&qgroup->groups,
+                                                struct btrfs_qgroup_list,
+                                                next_group);
+                        list_del(&list->next_group);
+                        list_del(&list->next_member);
+                        kfree(list);
+                }
+
+                while (!list_empty(&qgroup->members)) {
+                        list = list_first_entry(&qgroup->members,
+                                                struct btrfs_qgroup_list,
+                                                next_member);
+                        list_del(&list->next_group);
+                        list_del(&list->next_member);
+                        kfree(list);
+                }
+                kfree(qgroup);
+        }
+}
+
+static int add_qgroup_relation_item(struct btrfs_trans_handle *trans,
+                                    struct btrfs_root *quota_root,
+                                    u64 src, u64 dst)
+{
+        int ret;
+        struct btrfs_path *path;
+        struct btrfs_key key;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = src;
+        key.type = BTRFS_QGROUP_RELATION_KEY;
+        key.offset = dst;
+
+        ret = btrfs_insert_empty_item(trans, quota_root, path, &key, 0);
+
+        btrfs_mark_buffer_dirty(path->nodes[0]);
+
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int del_qgroup_relation_item(struct btrfs_trans_handle *trans,
+                                    struct btrfs_root *quota_root,
+                                    u64 src, u64 dst)
+{
+        int ret;
+        struct btrfs_path *path;
+        struct btrfs_key key;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = src;
+        key.type = BTRFS_QGROUP_RELATION_KEY;
+        key.offset = dst;
+
+        ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
+        if (ret < 0)
+                goto out;
+
+        if (ret > 0) {
+                ret = -ENOENT;
+                goto out;
+        }
+
+        ret = btrfs_del_item(trans, quota_root, path);
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int add_qgroup_item(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *quota_root, u64 qgroupid)
+{
+        int ret;
+        struct btrfs_path *path;
+        struct btrfs_qgroup_info_item *qgroup_info;
+        struct btrfs_qgroup_limit_item *qgroup_limit;
+        struct extent_buffer *leaf;
+        struct btrfs_key key;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_INFO_KEY;
+        key.offset = qgroupid;
+
+        ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
+                                      sizeof(*qgroup_info));
+        if (ret)
+                goto out;
+
+        leaf = path->nodes[0];
+        qgroup_info = btrfs_item_ptr(leaf, path->slots[0],
+                                 struct btrfs_qgroup_info_item);
+        btrfs_set_qgroup_info_generation(leaf, qgroup_info, trans->transid);
+        btrfs_set_qgroup_info_rfer(leaf, qgroup_info, 0);
+        btrfs_set_qgroup_info_rfer_cmpr(leaf, qgroup_info, 0);
+        btrfs_set_qgroup_info_excl(leaf, qgroup_info, 0);
+        btrfs_set_qgroup_info_excl_cmpr(leaf, qgroup_info, 0);
+
+        btrfs_mark_buffer_dirty(leaf);
+
+        btrfs_release_path(path);
+
+        key.type = BTRFS_QGROUP_LIMIT_KEY;
+        ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
+                                      sizeof(*qgroup_limit));
+        if (ret)
+                goto out;
+
+        leaf = path->nodes[0];
+        qgroup_limit = btrfs_item_ptr(leaf, path->slots[0],
+                                  struct btrfs_qgroup_limit_item);
+        btrfs_set_qgroup_limit_flags(leaf, qgroup_limit, 0);
+        btrfs_set_qgroup_limit_max_rfer(leaf, qgroup_limit, 0);
+        btrfs_set_qgroup_limit_max_excl(leaf, qgroup_limit, 0);
+        btrfs_set_qgroup_limit_rsv_rfer(leaf, qgroup_limit, 0);
+        btrfs_set_qgroup_limit_rsv_excl(leaf, qgroup_limit, 0);
+
+        btrfs_mark_buffer_dirty(leaf);
+
+        ret = 0;
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int del_qgroup_item(struct btrfs_trans_handle *trans,
+                           struct btrfs_root *quota_root, u64 qgroupid)
+{
+        int ret;
+        struct btrfs_path *path;
+        struct btrfs_key key;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_INFO_KEY;
+        key.offset = qgroupid;
+        ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
+        if (ret < 0)
+                goto out;
+
+        if (ret > 0) {
+                ret = -ENOENT;
+                goto out;
+        }
+
+        ret = btrfs_del_item(trans, quota_root, path);
+        if (ret)
+                goto out;
+
+        btrfs_release_path(path);
+
+        key.type = BTRFS_QGROUP_LIMIT_KEY;
+        ret = btrfs_search_slot(trans, quota_root, &key, path, -1, 1);
+        if (ret < 0)
+                goto out;
+
+        if (ret > 0) {
+                ret = -ENOENT;
+                goto out;
+        }
+
+        ret = btrfs_del_item(trans, quota_root, path);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int update_qgroup_limit_item(struct btrfs_trans_handle *trans,
+                                    struct btrfs_root *root, u64 qgroupid,
+                                    u64 flags, u64 max_rfer, u64 max_excl,
+                                    u64 rsv_rfer, u64 rsv_excl)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct extent_buffer *l;
+        struct btrfs_qgroup_limit_item *qgroup_limit;
+        int ret;
+        int slot;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_LIMIT_KEY;
+        key.offset = qgroupid;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+        if (ret > 0)
+                ret = -ENOENT;
+
+        if (ret)
+                goto out;
+
+        l = path->nodes[0];
+        slot = path->slots[0];
+        qgroup_limit = btrfs_item_ptr(l, path->slots[0],
+                                      struct btrfs_qgroup_limit_item);
+        btrfs_set_qgroup_limit_flags(l, qgroup_limit, flags);
+        btrfs_set_qgroup_limit_max_rfer(l, qgroup_limit, max_rfer);
+        btrfs_set_qgroup_limit_max_excl(l, qgroup_limit, max_excl);
+        btrfs_set_qgroup_limit_rsv_rfer(l, qgroup_limit, rsv_rfer);
+        btrfs_set_qgroup_limit_rsv_excl(l, qgroup_limit, rsv_excl);
+
+        btrfs_mark_buffer_dirty(l);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int update_qgroup_info_item(struct btrfs_trans_handle *trans,
+                                   struct btrfs_root *root,
+                                   struct btrfs_qgroup *qgroup)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct extent_buffer *l;
+        struct btrfs_qgroup_info_item *qgroup_info;
+        int ret;
+        int slot;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_INFO_KEY;
+        key.offset = qgroup->qgroupid;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+        if (ret > 0)
+                ret = -ENOENT;
+
+        if (ret)
+                goto out;
+
+        l = path->nodes[0];
+        slot = path->slots[0];
+        qgroup_info = btrfs_item_ptr(l, path->slots[0],
+                                 struct btrfs_qgroup_info_item);
+        btrfs_set_qgroup_info_generation(l, qgroup_info, trans->transid);
+        btrfs_set_qgroup_info_rfer(l, qgroup_info, qgroup->rfer);
+        btrfs_set_qgroup_info_rfer_cmpr(l, qgroup_info, qgroup->rfer_cmpr);
+        btrfs_set_qgroup_info_excl(l, qgroup_info, qgroup->excl);
+        btrfs_set_qgroup_info_excl_cmpr(l, qgroup_info, qgroup->excl_cmpr);
+
+        btrfs_mark_buffer_dirty(l);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+static int update_qgroup_status_item(struct btrfs_trans_handle *trans,
+                                     struct btrfs_fs_info *fs_info,
+                                    struct btrfs_root *root)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct extent_buffer *l;
+        struct btrfs_qgroup_status_item *ptr;
+        int ret;
+        int slot;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_STATUS_KEY;
+        key.offset = 0;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+        if (ret > 0)
+                ret = -ENOENT;
+
+        if (ret)
+                goto out;
+
+        l = path->nodes[0];
+        slot = path->slots[0];
+        ptr = btrfs_item_ptr(l, slot, struct btrfs_qgroup_status_item);
+        btrfs_set_qgroup_status_flags(l, ptr, fs_info->qgroup_flags);
+        btrfs_set_qgroup_status_generation(l, ptr, trans->transid);
+        /* XXX scan */
+
+        btrfs_mark_buffer_dirty(l);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+/*
+ * called with qgroup_lock held
+ */
+static int btrfs_clean_quota_tree(struct btrfs_trans_handle *trans,
+                                  struct btrfs_root *root)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        int ret;
+
+        if (!root)
+                return -EINVAL;
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        while (1) {
+                key.objectid = 0;
+                key.offset = 0;
+                key.type = 0;
+
+                path->leave_spinning = 1;
+                ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+                if (ret > 0) {
+                        if (path->slots[0] == 0)
+                                break;
+                        path->slots[0]--;
+                } else if (ret < 0) {
+                        break;
+                }
+
+                ret = btrfs_del_item(trans, root, path);
+                if (ret)
+                        goto out;
+                btrfs_release_path(path);
+        }
+        ret = 0;
+out:
+        root->fs_info->pending_quota_state = 0;
+        btrfs_free_path(path);
+        return ret;
+}
+
+int btrfs_quota_enable(struct btrfs_trans_handle *trans,
+                       struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *quota_root;
+        struct btrfs_path *path = NULL;
+        struct btrfs_qgroup_status_item *ptr;
+        struct extent_buffer *leaf;
+        struct btrfs_key key;
+        int ret = 0;
+
+        spin_lock(&fs_info->qgroup_lock);
+        if (fs_info->quota_root) {
+                fs_info->pending_quota_state = 1;
+                spin_unlock(&fs_info->qgroup_lock);
+                goto out;
+        }
+        spin_unlock(&fs_info->qgroup_lock);
+
+        /*
+         * initially create the quota tree
+         */
+        quota_root = btrfs_create_tree(trans, fs_info,
+                                       BTRFS_QUOTA_TREE_OBJECTID);
+        if (IS_ERR(quota_root)) {
+                ret =  PTR_ERR(quota_root);
+                goto out;
+        }
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
+        key.objectid = 0;
+        key.type = BTRFS_QGROUP_STATUS_KEY;
+        key.offset = 0;
+
+        ret = btrfs_insert_empty_item(trans, quota_root, path, &key,
+                                      sizeof(*ptr));
+        if (ret)
+                goto out;
+
+        leaf = path->nodes[0];
+        ptr = btrfs_item_ptr(leaf, path->slots[0],
+                                 struct btrfs_qgroup_status_item);
+        btrfs_set_qgroup_status_generation(leaf, ptr, trans->transid);
+        btrfs_set_qgroup_status_version(leaf, ptr, BTRFS_QGROUP_STATUS_VERSION);
+        fs_info->qgroup_flags = BTRFS_QGROUP_STATUS_FLAG_ON |
+                                BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+        btrfs_set_qgroup_status_flags(leaf, ptr, fs_info->qgroup_flags);
+        btrfs_set_qgroup_status_scan(leaf, ptr, 0);
+
+        btrfs_mark_buffer_dirty(leaf);
+
+        spin_lock(&fs_info->qgroup_lock);
+        fs_info->quota_root = quota_root;
+        fs_info->pending_quota_state = 1;
+        spin_unlock(&fs_info->qgroup_lock);
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+int btrfs_quota_disable(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *tree_root = fs_info->tree_root;
+        struct btrfs_root *quota_root;
+        int ret = 0;
+
+        spin_lock(&fs_info->qgroup_lock);
+        fs_info->quota_enabled = 0;
+        fs_info->pending_quota_state = 0;
+        quota_root = fs_info->quota_root;
+        fs_info->quota_root = NULL;
+        btrfs_free_qgroup_config(fs_info);
+        spin_unlock(&fs_info->qgroup_lock);
+
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = btrfs_clean_quota_tree(trans, quota_root);
+        if (ret)
+                goto out;
+
+        ret = btrfs_del_root(trans, tree_root, &quota_root->root_key);
+        if (ret)
+                goto out;
+
+        list_del(&quota_root->dirty_list);
+
+        btrfs_tree_lock(quota_root->node);
+        clean_tree_block(trans, tree_root, quota_root->node);
+        btrfs_tree_unlock(quota_root->node);
+        btrfs_free_tree_block(trans, quota_root, quota_root->node, 0, 1);
+
+        free_extent_buffer(quota_root->node);
+        free_extent_buffer(quota_root->commit_root);
+        kfree(quota_root);
+out:
+        return ret;
+}
+
+int btrfs_quota_rescan(struct btrfs_fs_info *fs_info)
+{
+        /* FIXME */
+        return 0;
+}
+
+int btrfs_add_qgroup_relation(struct btrfs_trans_handle *trans,
+                              struct btrfs_fs_info *fs_info, u64 src, u64 dst)
+{
+        struct btrfs_root *quota_root;
+        int ret = 0;
+
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = add_qgroup_relation_item(trans, quota_root, src, dst);
+        if (ret)
+                return ret;
+
+        ret = add_qgroup_relation_item(trans, quota_root, dst, src);
+        if (ret) {
+                del_qgroup_relation_item(trans, quota_root, src, dst);
+                return ret;
+        }
+
+        spin_lock(&fs_info->qgroup_lock);
+        ret = add_relation_rb(quota_root->fs_info, src, dst);
+        spin_unlock(&fs_info->qgroup_lock);
+
+        return ret;
+}
+
+int btrfs_del_qgroup_relation(struct btrfs_trans_handle *trans,
+                              struct btrfs_fs_info *fs_info, u64 src, u64 dst)
+{
+        struct btrfs_root *quota_root;
+        int ret = 0;
+        int err;
+
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = del_qgroup_relation_item(trans, quota_root, src, dst);
+        err = del_qgroup_relation_item(trans, quota_root, dst, src);
+        if (err && !ret)
+                ret = err;
+
+        spin_lock(&fs_info->qgroup_lock);
+        del_relation_rb(fs_info, src, dst);
+
+        spin_unlock(&fs_info->qgroup_lock);
+
+        return ret;
+}
+
+int btrfs_create_qgroup(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info, u64 qgroupid, char *name)
+{
+        struct btrfs_root *quota_root;
+        struct btrfs_qgroup *qgroup;
+        int ret = 0;
+
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = add_qgroup_item(trans, quota_root, qgroupid);
+
+        spin_lock(&fs_info->qgroup_lock);
+        qgroup = add_qgroup_rb(fs_info, qgroupid);
+        spin_unlock(&fs_info->qgroup_lock);
+
+        if (IS_ERR(qgroup))
+                ret = PTR_ERR(qgroup);
+
+        return ret;
+}
+
+int btrfs_remove_qgroup(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info, u64 qgroupid)
+{
+        struct btrfs_root *quota_root;
+        int ret = 0;
+
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = del_qgroup_item(trans, quota_root, qgroupid);
+
+        spin_lock(&fs_info->qgroup_lock);
+        del_qgroup_rb(quota_root->fs_info, qgroupid);
+
+        spin_unlock(&fs_info->qgroup_lock);
+
+        return ret;
+}
+
+int btrfs_limit_qgroup(struct btrfs_trans_handle *trans,
+                       struct btrfs_fs_info *fs_info, u64 qgroupid,
+                       struct btrfs_qgroup_limit *limit)
+{
+        struct btrfs_root *quota_root = fs_info->quota_root;
+        struct btrfs_qgroup *qgroup;
+        int ret = 0;
+
+        if (!quota_root)
+                return -EINVAL;
+
+        ret = update_qgroup_limit_item(trans, quota_root, qgroupid,
+                                       limit->flags, limit->max_rfer,
+                                       limit->max_excl, limit->rsv_rfer,
+                                       limit->rsv_excl);
+        if (ret) {
+                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+                printk(KERN_INFO "unable to update quota limit for %llu\n",
+                       (unsigned long long)qgroupid);
+        }
+
+        spin_lock(&fs_info->qgroup_lock);
+
+        qgroup = find_qgroup_rb(fs_info, qgroupid);
+        if (!qgroup) {
+                ret = -ENOENT;
+                goto unlock;
+        }
+        qgroup->lim_flags = limit->flags;
+        qgroup->max_rfer = limit->max_rfer;
+        qgroup->max_excl = limit->max_excl;
+        qgroup->rsv_rfer = limit->rsv_rfer;
+        qgroup->rsv_excl = limit->rsv_excl;
+
+unlock:
+        spin_unlock(&fs_info->qgroup_lock);
+
+        return ret;
+}
+
+static void qgroup_dirty(struct btrfs_fs_info *fs_info,
+                         struct btrfs_qgroup *qgroup)
+{
+        if (list_empty(&qgroup->dirty))
+                list_add(&qgroup->dirty, &fs_info->dirty_qgroups);
+}
+
+/*
+ * btrfs_qgroup_record_ref is called when the ref is added or deleted. it puts
+ * the modification into a list that's later used by btrfs_end_transaction to
+ * pass the recorded modifications on to btrfs_qgroup_account_ref.
+ */
+int btrfs_qgroup_record_ref(struct btrfs_trans_handle *trans,
+                            struct btrfs_delayed_ref_node *node,
+                            struct btrfs_delayed_extent_op *extent_op)
+{
+        struct qgroup_update *u;
+
+        BUG_ON(!trans->delayed_ref_elem.seq);
+        u = kmalloc(sizeof(*u), GFP_NOFS);
+        if (!u)
+                return -ENOMEM;
+
+        u->node = node;
+        u->extent_op = extent_op;
+        list_add_tail(&u->list, &trans->qgroup_ref_list);
+
+        return 0;
+}
+
+/*
+ * btrfs_qgroup_account_ref is called for every ref that is added to or deleted
+ * from the fs. First, all roots referencing the extent are searched, and
+ * then the space is accounted accordingly to the different roots. The
+ * accounting algorithm works in 3 steps documented inline.
+ */
+int btrfs_qgroup_account_ref(struct btrfs_trans_handle *trans,
+                             struct btrfs_fs_info *fs_info,
+                             struct btrfs_delayed_ref_node *node,
+                             struct btrfs_delayed_extent_op *extent_op)
+{
+        struct btrfs_key ins;
+        struct btrfs_root *quota_root;
+        u64 ref_root;
+        struct btrfs_qgroup *qgroup;
+        struct ulist_node *unode;
+        struct ulist *roots = NULL;
+        struct ulist *tmp = NULL;
+        struct ulist_iterator uiter;
+        u64 seq;
+        int ret = 0;
+        int sgn;
+
+        if (!fs_info->quota_enabled)
+                return 0;
+
+        BUG_ON(!fs_info->quota_root);
+
+        ins.objectid = node->bytenr;
+        ins.offset = node->num_bytes;
+        ins.type = BTRFS_EXTENT_ITEM_KEY;
+
+        if (node->type == BTRFS_TREE_BLOCK_REF_KEY ||
+            node->type == BTRFS_SHARED_BLOCK_REF_KEY) {
+                struct btrfs_delayed_tree_ref *ref;
+                ref = btrfs_delayed_node_to_tree_ref(node);
+                ref_root = ref->root;
+        } else if (node->type == BTRFS_EXTENT_DATA_REF_KEY ||
+                   node->type == BTRFS_SHARED_DATA_REF_KEY) {
+                struct btrfs_delayed_data_ref *ref;
+                ref = btrfs_delayed_node_to_data_ref(node);
+                ref_root = ref->root;
+        } else {
+                BUG();
+        }
+
+        if (!is_fstree(ref_root)) {
+                /*
+                 * non-fs-trees are not being accounted
+                 */
+                return 0;
+        }
+
+        switch (node->action) {
+        case BTRFS_ADD_DELAYED_REF:
+        case BTRFS_ADD_DELAYED_EXTENT:
+                sgn = 1;
+                break;
+        case BTRFS_DROP_DELAYED_REF:
+                sgn = -1;
+                break;
+        case BTRFS_UPDATE_DELAYED_HEAD:
+                return 0;
+        default:
+                BUG();
+        }
+
+        /*
+         * the delayed ref sequence number we pass depends on the direction of
+         * the operation. for add operations, we pass (node->seq - 1) to skip
+         * the delayed ref's current sequence number, because we need the state
+         * of the tree before the add operation. for delete operations, we pass
+         * (node->seq) to include the delayed ref's current sequence number,
+         * because we need the state of the tree after the delete operation.
+         */
+        ret = btrfs_find_all_roots(trans, fs_info, node->bytenr,
+                                   sgn > 0 ? node->seq - 1 : node->seq, &roots);
+        if (ret < 0)
+                goto out;
+
+        spin_lock(&fs_info->qgroup_lock);
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                goto unlock;
+
+        qgroup = find_qgroup_rb(fs_info, ref_root);
+        if (!qgroup)
+                goto unlock;
+
+        /*
+         * step 1: for each old ref, visit all nodes once and inc refcnt
+         */
+        tmp = ulist_alloc(GFP_ATOMIC);
+        if (!tmp) {
+                ret = -ENOMEM;
+                goto unlock;
+        }
+        seq = fs_info->qgroup_seq;
+        fs_info->qgroup_seq += roots->nnodes + 1; /* max refcnt */
+
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(roots, &uiter))) {
+                struct ulist_node *tmp_unode;
+                struct ulist_iterator tmp_uiter;
+                struct btrfs_qgroup *qg;
+
+                qg = find_qgroup_rb(fs_info, unode->val);
+                if (!qg)
+                        continue;
+
+                ulist_reinit(tmp);
+                                                /* XXX id not needed */
+                ulist_add(tmp, qg->qgroupid, (unsigned long)qg, GFP_ATOMIC);
+                ULIST_ITER_INIT(&tmp_uiter);
+                while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
+                        struct btrfs_qgroup_list *glist;
+
+                        qg = (struct btrfs_qgroup *)tmp_unode->aux;
+                        if (qg->refcnt < seq)
+                                qg->refcnt = seq + 1;
+                        else
+                                ++qg->refcnt;
+
+                        list_for_each_entry(glist, &qg->groups, next_group) {
+                                ulist_add(tmp, glist->group->qgroupid,
+                                          (unsigned long)glist->group,
+                                          GFP_ATOMIC);
+                        }
+                }
+        }
+
+        /*
+         * step 2: walk from the new root
+         */
+        ulist_reinit(tmp);
+        ulist_add(tmp, qgroup->qgroupid, (unsigned long)qgroup, GFP_ATOMIC);
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(tmp, &uiter))) {
+                struct btrfs_qgroup *qg;
+                struct btrfs_qgroup_list *glist;
+
+                qg = (struct btrfs_qgroup *)unode->aux;
+                if (qg->refcnt < seq) {
+                        /* not visited by step 1 */
+                        qg->rfer += sgn * node->num_bytes;
+                        qg->rfer_cmpr += sgn * node->num_bytes;
+                        if (roots->nnodes == 0) {
+                                qg->excl += sgn * node->num_bytes;
+                                qg->excl_cmpr += sgn * node->num_bytes;
+                        }
+                        qgroup_dirty(fs_info, qg);
+                }
+                WARN_ON(qg->tag >= seq);
+                qg->tag = seq;
+
+                list_for_each_entry(glist, &qg->groups, next_group) {
+                        ulist_add(tmp, glist->group->qgroupid,
+                                  (unsigned long)glist->group, GFP_ATOMIC);
+                }
+        }
+
+        /*
+         * step 3: walk again from old refs
+         */
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(roots, &uiter))) {
+                struct btrfs_qgroup *qg;
+                struct ulist_node *tmp_unode;
+                struct ulist_iterator tmp_uiter;
+
+                qg = find_qgroup_rb(fs_info, unode->val);
+                if (!qg)
+                        continue;
+
+                ulist_reinit(tmp);
+                ulist_add(tmp, qg->qgroupid, (unsigned long)qg, GFP_ATOMIC);
+                ULIST_ITER_INIT(&tmp_uiter);
+                while ((tmp_unode = ulist_next(tmp, &tmp_uiter))) {
+                        struct btrfs_qgroup_list *glist;
+
+                        qg = (struct btrfs_qgroup *)tmp_unode->aux;
+                        if (qg->tag == seq)
+                                continue;
+
+                        if (qg->refcnt - seq == roots->nnodes) {
+                                qg->excl -= sgn * node->num_bytes;
+                                qg->excl_cmpr -= sgn * node->num_bytes;
+                                qgroup_dirty(fs_info, qg);
+                        }
+
+                        list_for_each_entry(glist, &qg->groups, next_group) {
+                                ulist_add(tmp, glist->group->qgroupid,
+                                          (unsigned long)glist->group,
+                                          GFP_ATOMIC);
+                        }
+                }
+        }
+        ret = 0;
+unlock:
+        spin_unlock(&fs_info->qgroup_lock);
+out:
+        ulist_free(roots);
+        ulist_free(tmp);
+
+        return ret;
+}
+
+/*
+ * called from commit_transaction. Writes all changed qgroups to disk.
+ */
+int btrfs_run_qgroups(struct btrfs_trans_handle *trans,
+                      struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *quota_root = fs_info->quota_root;
+        int ret = 0;
+
+        if (!quota_root)
+                goto out;
+
+        fs_info->quota_enabled = fs_info->pending_quota_state;
+
+        spin_lock(&fs_info->qgroup_lock);
+        while (!list_empty(&fs_info->dirty_qgroups)) {
+                struct btrfs_qgroup *qgroup;
+                qgroup = list_first_entry(&fs_info->dirty_qgroups,
+                                          struct btrfs_qgroup, dirty);
+                list_del_init(&qgroup->dirty);
+                spin_unlock(&fs_info->qgroup_lock);
+                ret = update_qgroup_info_item(trans, quota_root, qgroup);
+                if (ret)
+                        fs_info->qgroup_flags |=
+                                        BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+                spin_lock(&fs_info->qgroup_lock);
+        }
+        if (fs_info->quota_enabled)
+                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_ON;
+        else
+                fs_info->qgroup_flags &= ~BTRFS_QGROUP_STATUS_FLAG_ON;
+        spin_unlock(&fs_info->qgroup_lock);
+
+        ret = update_qgroup_status_item(trans, fs_info, quota_root);
+        if (ret)
+                fs_info->qgroup_flags |= BTRFS_QGROUP_STATUS_FLAG_INCONSISTENT;
+
+out:
+
+        return ret;
+}
+
+/*
+ * copy the acounting information between qgroups. This is necessary when a
+ * snapshot or a subvolume is created
+ */
+int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans,
+                         struct btrfs_fs_info *fs_info, u64 srcid, u64 objectid,
+                         struct btrfs_qgroup_inherit *inherit)
+{
+        int ret = 0;
+        int i;
+        u64 *i_qgroups;
+        struct btrfs_root *quota_root = fs_info->quota_root;
+        struct btrfs_qgroup *srcgroup;
+        struct btrfs_qgroup *dstgroup;
+        u32 level_size = 0;
+
+        if (!fs_info->quota_enabled)
+                return 0;
+
+        if (!quota_root)
+                return -EINVAL;
+
+        /*
+         * create a tracking group for the subvol itself
+         */
+        ret = add_qgroup_item(trans, quota_root, objectid);
+        if (ret)
+                goto out;
+
+        if (inherit && inherit->flags & BTRFS_QGROUP_INHERIT_SET_LIMITS) {
+                ret = update_qgroup_limit_item(trans, quota_root, objectid,
+                                               inherit->lim.flags,
+                                               inherit->lim.max_rfer,
+                                               inherit->lim.max_excl,
+                                               inherit->lim.rsv_rfer,
+                                               inherit->lim.rsv_excl);
+                if (ret)
+                        goto out;
+        }
+
+        if (srcid) {
+                struct btrfs_root *srcroot;
+                struct btrfs_key srckey;
+                int srcroot_level;
+
+                srckey.objectid = srcid;
+                srckey.type = BTRFS_ROOT_ITEM_KEY;
+                srckey.offset = (u64)-1;
+                srcroot = btrfs_read_fs_root_no_name(fs_info, &srckey);
+                if (IS_ERR(srcroot)) {
+                        ret = PTR_ERR(srcroot);
+                        goto out;
+                }
+
+                rcu_read_lock();
+                srcroot_level = btrfs_header_level(srcroot->node);
+                level_size = btrfs_level_size(srcroot, srcroot_level);
+                rcu_read_unlock();
+        }
+
+        /*
+         * add qgroup to all inherited groups
+         */
+        if (inherit) {
+                i_qgroups = (u64 *)(inherit + 1);
+                for (i = 0; i < inherit->num_qgroups; ++i) {
+                        ret = add_qgroup_relation_item(trans, quota_root,
+                                                       objectid, *i_qgroups);
+                        if (ret)
+                                goto out;
+                        ret = add_qgroup_relation_item(trans, quota_root,
+                                                       *i_qgroups, objectid);
+                        if (ret)
+                                goto out;
+                        ++i_qgroups;
+                }
+        }
+
+
+        spin_lock(&fs_info->qgroup_lock);
+
+        dstgroup = add_qgroup_rb(fs_info, objectid);
+        if (!dstgroup)
+                goto unlock;
+
+        if (srcid) {
+                srcgroup = find_qgroup_rb(fs_info, srcid);
+                if (!srcgroup)
+                        goto unlock;
+                dstgroup->rfer = srcgroup->rfer - level_size;
+                dstgroup->rfer_cmpr = srcgroup->rfer_cmpr - level_size;
+                srcgroup->excl = level_size;
+                srcgroup->excl_cmpr = level_size;
+                qgroup_dirty(fs_info, dstgroup);
+                qgroup_dirty(fs_info, srcgroup);
+        }
+
+        if (!inherit)
+                goto unlock;
+
+        i_qgroups = (u64 *)(inherit + 1);
+        for (i = 0; i < inherit->num_qgroups; ++i) {
+                ret = add_relation_rb(quota_root->fs_info, objectid,
+                                      *i_qgroups);
+                if (ret)
+                        goto unlock;
+                ++i_qgroups;
+        }
+
+        for (i = 0; i <  inherit->num_ref_copies; ++i) {
+                struct btrfs_qgroup *src;
+                struct btrfs_qgroup *dst;
+
+                src = find_qgroup_rb(fs_info, i_qgroups[0]);
+                dst = find_qgroup_rb(fs_info, i_qgroups[1]);
+
+                if (!src || !dst) {
+                        ret = -EINVAL;
+                        goto unlock;
+                }
+
+                dst->rfer = src->rfer - level_size;
+                dst->rfer_cmpr = src->rfer_cmpr - level_size;
+                i_qgroups += 2;
+        }
+        for (i = 0; i <  inherit->num_excl_copies; ++i) {
+                struct btrfs_qgroup *src;
+                struct btrfs_qgroup *dst;
+
+                src = find_qgroup_rb(fs_info, i_qgroups[0]);
+                dst = find_qgroup_rb(fs_info, i_qgroups[1]);
+
+                if (!src || !dst) {
+                        ret = -EINVAL;
+                        goto unlock;
+                }
+
+                dst->excl = src->excl + level_size;
+                dst->excl_cmpr = src->excl_cmpr + level_size;
+                i_qgroups += 2;
+        }
+
+unlock:
+        spin_unlock(&fs_info->qgroup_lock);
+out:
+        return ret;
+}
+
+/*
+ * reserve some space for a qgroup and all its parents. The reservation takes
+ * place with start_transaction or dealloc_reserve, similar to ENOSPC
+ * accounting. If not enough space is available, EDQUOT is returned.
+ * We assume that the requested space is new for all qgroups.
+ */
+int btrfs_qgroup_reserve(struct btrfs_root *root, u64 num_bytes)
+{
+        struct btrfs_root *quota_root;
+        struct btrfs_qgroup *qgroup;
+        struct btrfs_fs_info *fs_info = root->fs_info;
+        u64 ref_root = root->root_key.objectid;
+        int ret = 0;
+        struct ulist *ulist = NULL;
+        struct ulist_node *unode;
+        struct ulist_iterator uiter;
+
+        if (!is_fstree(ref_root))
+                return 0;
+
+        if (num_bytes == 0)
+                return 0;
+
+        spin_lock(&fs_info->qgroup_lock);
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                goto out;
+
+        qgroup = find_qgroup_rb(fs_info, ref_root);
+        if (!qgroup)
+                goto out;
+
+        /*
+         * in a first step, we check all affected qgroups if any limits would
+         * be exceeded
+         */
+        ulist = ulist_alloc(GFP_ATOMIC);
+        ulist_add(ulist, qgroup->qgroupid, (unsigned long)qgroup, GFP_ATOMIC);
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(ulist, &uiter))) {
+                struct btrfs_qgroup *qg;
+                struct btrfs_qgroup_list *glist;
+
+                qg = (struct btrfs_qgroup *)unode->aux;
+
+                if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_RFER) &&
+                    qg->reserved + qg->rfer + num_bytes >
+                    qg->max_rfer)
+                        ret = -EDQUOT;
+
+                if ((qg->lim_flags & BTRFS_QGROUP_LIMIT_MAX_EXCL) &&
+                    qg->reserved + qg->excl + num_bytes >
+                    qg->max_excl)
+                        ret = -EDQUOT;
+
+                list_for_each_entry(glist, &qg->groups, next_group) {
+                        ulist_add(ulist, glist->group->qgroupid,
+                                  (unsigned long)glist->group, GFP_ATOMIC);
+                }
+        }
+        if (ret)
+                goto out;
+
+        /*
+         * no limits exceeded, now record the reservation into all qgroups
+         */
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(ulist, &uiter))) {
+                struct btrfs_qgroup *qg;
+
+                qg = (struct btrfs_qgroup *)unode->aux;
+
+                qg->reserved += num_bytes;
+        }
+
+out:
+        spin_unlock(&fs_info->qgroup_lock);
+        ulist_free(ulist);
+
+        return ret;
+}
+
+void btrfs_qgroup_free(struct btrfs_root *root, u64 num_bytes)
+{
+        struct btrfs_root *quota_root;
+        struct btrfs_qgroup *qgroup;
+        struct btrfs_fs_info *fs_info = root->fs_info;
+        struct ulist *ulist = NULL;
+        struct ulist_node *unode;
+        struct ulist_iterator uiter;
+        u64 ref_root = root->root_key.objectid;
+
+        if (!is_fstree(ref_root))
+                return;
+
+        if (num_bytes == 0)
+                return;
+
+        spin_lock(&fs_info->qgroup_lock);
+
+        quota_root = fs_info->quota_root;
+        if (!quota_root)
+                goto out;
+
+        qgroup = find_qgroup_rb(fs_info, ref_root);
+        if (!qgroup)
+                goto out;
+
+        ulist = ulist_alloc(GFP_ATOMIC);
+        ulist_add(ulist, qgroup->qgroupid, (unsigned long)qgroup, GFP_ATOMIC);
+        ULIST_ITER_INIT(&uiter);
+        while ((unode = ulist_next(ulist, &uiter))) {
+                struct btrfs_qgroup *qg;
+                struct btrfs_qgroup_list *glist;
+
+                qg = (struct btrfs_qgroup *)unode->aux;
+
+                qg->reserved -= num_bytes;
+
+                list_for_each_entry(glist, &qg->groups, next_group) {
+                        ulist_add(ulist, glist->group->qgroupid,
+                                  (unsigned long)glist->group, GFP_ATOMIC);
+                }
+        }
+
+out:
+        spin_unlock(&fs_info->qgroup_lock);
+        ulist_free(ulist);
+}
+
+void assert_qgroups_uptodate(struct btrfs_trans_handle *trans)
+{
+        if (list_empty(&trans->qgroup_ref_list) && !trans->delayed_ref_elem.seq)
+                return;
+        printk(KERN_ERR "btrfs: qgroups not uptodate in trans handle %p: list is%s empty, seq is %llu\n",
+                trans, list_empty(&trans->qgroup_ref_list) ? "" : " not",
+                trans->delayed_ref_elem.seq);
+        BUG();
+}
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 328b95f67660..cc20e95ea289 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -38,7 +38,6 @@ void put_transaction(struct btrfs_transaction *transaction)
         if (atomic_dec_and_test(&transaction->use_count)) {
                 BUG_ON(!list_empty(&transaction->list));
                 WARN_ON(transaction->delayed_refs.root.rb_node);
-                WARN_ON(!list_empty(&transaction->delayed_refs.seq_head));
                 memset(transaction, 0, sizeof(*transaction));
                 kmem_cache_free(btrfs_transaction_cachep, transaction);
         }
@@ -126,7 +125,6 @@ loop:
         cur_trans->delayed_refs.num_heads = 0;
         cur_trans->delayed_refs.flushing = 0;
         cur_trans->delayed_refs.run_delayed_start = 0;
-        cur_trans->delayed_refs.seq = 1;
 
         /*
          * although the tree mod log is per file system and not per transaction,
@@ -145,10 +143,8 @@ loop:
         }
         atomic_set(&fs_info->tree_mod_seq, 0);
 
-        init_waitqueue_head(&cur_trans->delayed_refs.seq_wait);
         spin_lock_init(&cur_trans->commit_lock);
         spin_lock_init(&cur_trans->delayed_refs.lock);
-        INIT_LIST_HEAD(&cur_trans->delayed_refs.seq_head);
 
         INIT_LIST_HEAD(&cur_trans->pending_snapshots);
         list_add_tail(&cur_trans->list, &fs_info->trans_list);
@@ -299,6 +295,7 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
         struct btrfs_transaction *cur_trans;
         u64 num_bytes = 0;
         int ret;
+        u64 qgroup_reserved = 0;
 
         if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
                 return ERR_PTR(-EROFS);
@@ -317,6 +314,14 @@ static struct btrfs_trans_handle *start_transaction(struct btrfs_root *root,
          * the appropriate flushing if need be.
          */
         if (num_items > 0 && root != root->fs_info->chunk_root) {
+                if (root->fs_info->quota_enabled &&
+                    is_fstree(root->root_key.objectid)) {
+                        qgroup_reserved = num_items * root->leafsize;
+                        ret = btrfs_qgroup_reserve(root, qgroup_reserved);
+                        if (ret)
+                                return ERR_PTR(ret);
+                }
+
                 num_bytes = btrfs_calc_trans_metadata_size(root, num_items);
                 ret = btrfs_block_rsv_add(root,
                                           &root->fs_info->trans_block_rsv,
@@ -349,12 +354,16 @@ again:
         h->transaction = cur_trans;
         h->blocks_used = 0;
         h->bytes_reserved = 0;
+        h->root = root;
         h->delayed_ref_updates = 0;
         h->use_count = 1;
         h->adding_csums = 0;
         h->block_rsv = NULL;
         h->orig_rsv = NULL;
         h->aborted = 0;
+        h->qgroup_reserved = qgroup_reserved;
+        h->delayed_ref_elem.seq = 0;
+        INIT_LIST_HEAD(&h->qgroup_ref_list);
 
         smp_mb();
         if (cur_trans->blocked && may_wait_transaction(root, type)) {
@@ -505,6 +514,24 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
                 return 0;
         }
 
+        /*
+         * do the qgroup accounting as early as possible
+         */
+        err = btrfs_delayed_refs_qgroup_accounting(trans, info);
+
+        btrfs_trans_release_metadata(trans, root);
+        trans->block_rsv = NULL;
+        /*
+         * the same root has to be passed to start_transaction and
+         * end_transaction. Subvolume quota depends on this.
+         */
+        WARN_ON(trans->root != root);
+
+        if (trans->qgroup_reserved) {
+                btrfs_qgroup_free(root, trans->qgroup_reserved);
+                trans->qgroup_reserved = 0;
+        }
+
         while (count < 2) {
                 unsigned long cur = trans->delayed_ref_updates;
                 trans->delayed_ref_updates = 0;
@@ -559,6 +586,7 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
             root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR) {
                 err = -EIO;
         }
+        assert_qgroups_uptodate(trans);
 
         memset(trans, 0, sizeof(*trans));
         kmem_cache_free(btrfs_trans_handle_cachep, trans);
@@ -777,6 +805,13 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
         ret = btrfs_run_dev_stats(trans, root->fs_info);
         BUG_ON(ret);
 
+        ret = btrfs_run_qgroups(trans, root->fs_info);
+        BUG_ON(ret);
+
+        /* run_qgroups might have added some more refs */
+        ret = btrfs_run_delayed_refs(trans, root, (unsigned long)-1);
+        BUG_ON(ret);
+
         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
                 next = fs_info->dirty_cowonly_roots.next;
                 list_del_init(next);
@@ -949,6 +984,14 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                 }
         }
 
+        ret = btrfs_qgroup_inherit(trans, fs_info, root->root_key.objectid,
+                                   objectid, pending->inherit);
+        kfree(pending->inherit);
+        if (ret) {
+                pending->error = ret;
+                goto fail;
+        }
+
         key.objectid = objectid;
         key.offset = (u64)-1;
         key.type = BTRFS_ROOT_ITEM_KEY;
@@ -1345,6 +1388,13 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                         goto cleanup_transaction;
 
                 /*
+                 * running the delayed items may have added new refs. account
+                 * them now so that they hinder processing of more delayed refs
+                 * as little as possible.
+                 */
+                btrfs_delayed_refs_qgroup_accounting(trans, root->fs_info);
+
+                /*
                  * rename don't use btrfs_join_transaction, so, once we
                  * set the transaction to blocked above, we aren't going
                  * to get any new ordered operations.  We can safely run
@@ -1456,6 +1506,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
                             root->fs_info->chunk_root->node);
         switch_commit_root(root->fs_info->chunk_root);
 
+        assert_qgroups_uptodate(trans);
         update_super_roots(root);
 
         if (!root->fs_info->log_root_recovering) {
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index d314a74b4968..e8b8416c688b 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -20,6 +20,7 @@
 #define __BTRFS_TRANSACTION__
 #include "btrfs_inode.h"
 #include "delayed-ref.h"
+#include "ctree.h"
 
 struct btrfs_transaction {
         u64 transid;
@@ -49,6 +50,7 @@ struct btrfs_transaction {
 struct btrfs_trans_handle {
         u64 transid;
         u64 bytes_reserved;
+        u64 qgroup_reserved;
         unsigned long use_count;
         unsigned long blocks_reserved;
         unsigned long blocks_used;
@@ -58,12 +60,21 @@ struct btrfs_trans_handle {
         struct btrfs_block_rsv *orig_rsv;
         int aborted;
         int adding_csums;
+        /*
+         * this root is only needed to validate that the root passed to
+         * start_transaction is the same as the one passed to end_transaction.
+         * Subvolume quota depends on this
+         */
+        struct btrfs_root *root;
+        struct seq_list delayed_ref_elem;
+        struct list_head qgroup_ref_list;
 };
 
 struct btrfs_pending_snapshot {
         struct dentry *dentry;
         struct btrfs_root *root;
         struct btrfs_root *snap;
+        struct btrfs_qgroup_inherit *inherit;
         /* block reservation for the operation */
         struct btrfs_block_rsv block_rsv;
         /* extra metadata reseration for relocation */