10 files changed, 668 insertions, 46 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index eaf286abad17..46f52e1beade 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -99,6 +99,9 @@ struct btrfs_ordered_sum;
  */
 #define BTRFS_EXTENT_CSUM_OBJECTID -10ULL
 
+/* For storing free space cache */
+#define BTRFS_FREE_SPACE_OBJECTID -11ULL
+
 /* dummy objectid represents multiple objectids */
 #define BTRFS_MULTIPLE_OBJECTIDS -255ULL
 
@@ -265,6 +268,22 @@ struct btrfs_chunk {
         /* additional stripes go here */
 } __attribute__ ((__packed__));
 
+#define BTRFS_FREE_SPACE_EXTENT 1
+#define BTRFS_FREE_SPACE_BITMAP 2
+
+struct btrfs_free_space_entry {
+        __le64 offset;
+        __le64 bytes;
+        u8 type;
+} __attribute__ ((__packed__));
+
+struct btrfs_free_space_header {
+        struct btrfs_disk_key location;
+        __le64 generation;
+        __le64 num_entries;
+        __le64 num_bitmaps;
+} __attribute__ ((__packed__));
+
 static inline unsigned long btrfs_chunk_item_size(int num_stripes)
 {
         BUG_ON(num_stripes == 0);
@@ -365,8 +384,10 @@ struct btrfs_super_block {
 
         char label[BTRFS_LABEL_SIZE];
 
+        __le64 cache_generation;
+
         /* future expansion */
-        __le64 reserved[32];
+        __le64 reserved[31];
         u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
 } __attribute__ ((__packed__));
 
@@ -375,12 +396,12 @@ struct btrfs_super_block {
  * ones specified below then we will fail to mount
  */
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF    (1ULL << 0)
-#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL   (2ULL << 0)
+#define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL   (1ULL << 1)
 
 #define BTRFS_FEATURE_COMPAT_SUPP               0ULL
 #define BTRFS_FEATURE_COMPAT_RO_SUPP            0ULL
-#define BTRFS_FEATURE_INCOMPAT_SUPP             \
-        (BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF | \
+#define BTRFS_FEATURE_INCOMPAT_SUPP                     \
+        (BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF |         \
          BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL)
 
 /*
@@ -750,6 +771,14 @@ enum btrfs_caching_type {
         BTRFS_CACHE_FINISHED    = 2,
 };
 
+enum btrfs_disk_cache_state {
+        BTRFS_DC_WRITTEN        = 0,
+        BTRFS_DC_ERROR          = 1,
+        BTRFS_DC_CLEAR          = 2,
+        BTRFS_DC_SETUP          = 3,
+        BTRFS_DC_NEED_WRITE     = 4,
+};
+
 struct btrfs_caching_control {
         struct list_head list;
         struct mutex mutex;
@@ -763,6 +792,7 @@ struct btrfs_block_group_cache {
         struct btrfs_key key;
         struct btrfs_block_group_item item;
         struct btrfs_fs_info *fs_info;
+        struct inode *inode;
         spinlock_t lock;
         u64 pinned;
         u64 reserved;
@@ -773,8 +803,11 @@ struct btrfs_block_group_cache {
         int extents_thresh;
         int free_extents;
         int total_bitmaps;
-        int ro;
-        int dirty;
+        int ro:1;
+        int dirty:1;
+        int iref:1;
+
+        int disk_cache_state;
 
         /* cache tracking stuff */
         int cached;
@@ -1192,6 +1225,7 @@ struct btrfs_root {
 #define BTRFS_MOUNT_NOSSD               (1 << 9)
 #define BTRFS_MOUNT_DISCARD             (1 << 10)
 #define BTRFS_MOUNT_FORCE_COMPRESS      (1 << 11)
+#define BTRFS_MOUNT_SPACE_CACHE         (1 << 12)
 
 #define btrfs_clear_opt(o, opt)         ((o) &= ~BTRFS_MOUNT_##opt)
 #define btrfs_set_opt(o, opt)           ((o) |= BTRFS_MOUNT_##opt)
@@ -1665,6 +1699,27 @@ static inline void btrfs_set_dir_item_key(struct extent_buffer *eb,
         write_eb_member(eb, item, struct btrfs_dir_item, location, key);
 }
 
+BTRFS_SETGET_FUNCS(free_space_entries, struct btrfs_free_space_header,
+                   num_entries, 64);
+BTRFS_SETGET_FUNCS(free_space_bitmaps, struct btrfs_free_space_header,
+                   num_bitmaps, 64);
+BTRFS_SETGET_FUNCS(free_space_generation, struct btrfs_free_space_header,
+                   generation, 64);
+
+static inline void btrfs_free_space_key(struct extent_buffer *eb,
+                                        struct btrfs_free_space_header *h,
+                                        struct btrfs_disk_key *key)
+{
+        read_eb_member(eb, h, struct btrfs_free_space_header, location, key);
+}
+
+static inline void btrfs_set_free_space_key(struct extent_buffer *eb,
+                                            struct btrfs_free_space_header *h,
+                                            struct btrfs_disk_key *key)
+{
+        write_eb_member(eb, h, struct btrfs_free_space_header, location, key);
+}
+
 /* struct btrfs_disk_key */
 BTRFS_SETGET_STACK_FUNCS(disk_key_objectid, struct btrfs_disk_key,
                          objectid, 64);
@@ -1876,6 +1931,8 @@ BTRFS_SETGET_STACK_FUNCS(super_incompat_flags, struct btrfs_super_block,
                          incompat_flags, 64);
 BTRFS_SETGET_STACK_FUNCS(super_csum_type, struct btrfs_super_block,
                          csum_type, 16);
+BTRFS_SETGET_STACK_FUNCS(super_cache_generation, struct btrfs_super_block,
+                         cache_generation, 64);
 
 static inline int btrfs_super_csum_size(struct btrfs_super_block *s)
 {
@@ -2115,6 +2172,7 @@ int btrfs_set_block_group_ro(struct btrfs_root *root,
                              struct btrfs_block_group_cache *cache);
 int btrfs_set_block_group_rw(struct btrfs_root *root,
                              struct btrfs_block_group_cache *cache);
+void btrfs_put_block_group_cache(struct btrfs_fs_info *info);
 /* ctree.c */
 int btrfs_bin_search(struct extent_buffer *eb, struct btrfs_key *key,
                      int level, int *slot);
@@ -2426,6 +2484,10 @@ void btrfs_run_delayed_iputs(struct btrfs_root *root);
 int btrfs_prealloc_file_range(struct inode *inode, int mode,
                               u64 start, u64 num_bytes, u64 min_size,
                               loff_t actual_len, u64 *alloc_hint);
+int btrfs_prealloc_file_range_trans(struct inode *inode,
+                                    struct btrfs_trans_handle *trans, int mode,
+                                    u64 start, u64 num_bytes, u64 min_size,
+                                    loff_t actual_len, u64 *alloc_hint);
 extern const struct dentry_operations btrfs_dentry_operations;
 
 /* ioctl.c */
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 64f10082f048..45cf64fc1e3e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1685,7 +1685,6 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         __setup_root(4096, 4096, 4096, 4096, tree_root,
                      fs_info, BTRFS_ROOT_TREE_OBJECTID);
 
-
         bh = btrfs_read_dev_super(fs_devices->latest_bdev);
         if (!bh)
                 goto fail_iput;
@@ -1993,6 +1992,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         if (!(sb->s_flags & MS_RDONLY)) {
                 down_read(&fs_info->cleanup_work_sem);
                 btrfs_orphan_cleanup(fs_info->fs_root);
+                btrfs_orphan_cleanup(fs_info->tree_root);
                 up_read(&fs_info->cleanup_work_sem);
         }
 
@@ -2421,6 +2421,7 @@ int close_ctree(struct btrfs_root *root)
         fs_info->closing = 1;
         smp_mb();
 
+        btrfs_put_block_group_cache(fs_info);
         if (!(fs_info->sb->s_flags & MS_RDONLY)) {
                 ret =  btrfs_commit_super(root);
                 if (ret)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 32d094002a57..aab40fb3faed 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2688,6 +2688,109 @@ next_block_group(struct btrfs_root *root,
         return cache;
 }
 
+static int cache_save_setup(struct btrfs_block_group_cache *block_group,
+                            struct btrfs_trans_handle *trans,
+                            struct btrfs_path *path)
+{
+        struct btrfs_root *root = block_group->fs_info->tree_root;
+        struct inode *inode = NULL;
+        u64 alloc_hint = 0;
+        int num_pages = 0;
+        int retries = 0;
+        int ret = 0;
+
+        /*
+         * If this block group is smaller than 100 megs don't bother caching the
+         * block group.
+         */
+        if (block_group->key.offset < (100 * 1024 * 1024)) {
+                spin_lock(&block_group->lock);
+                block_group->disk_cache_state = BTRFS_DC_WRITTEN;
+                spin_unlock(&block_group->lock);
+                return 0;
+        }
+
+again:
+        inode = lookup_free_space_inode(root, block_group, path);
+        if (IS_ERR(inode) && PTR_ERR(inode) != -ENOENT) {
+                ret = PTR_ERR(inode);
+                btrfs_release_path(root, path);
+                goto out;
+        }
+
+        if (IS_ERR(inode)) {
+                BUG_ON(retries);
+                retries++;
+
+                if (block_group->ro)
+                        goto out_free;
+
+                ret = create_free_space_inode(root, trans, block_group, path);
+                if (ret)
+                        goto out_free;
+                goto again;
+        }
+
+        /*
+         * We want to set the generation to 0, that way if anything goes wrong
+         * from here on out we know not to trust this cache when we load up next
+         * time.
+         */
+        BTRFS_I(inode)->generation = 0;
+        ret = btrfs_update_inode(trans, root, inode);
+        WARN_ON(ret);
+
+        if (i_size_read(inode) > 0) {
+                ret = btrfs_truncate_free_space_cache(root, trans, path,
+                                                      inode);
+                if (ret)
+                        goto out_put;
+        }
+
+        spin_lock(&block_group->lock);
+        if (block_group->cached != BTRFS_CACHE_FINISHED) {
+                spin_unlock(&block_group->lock);
+                goto out_put;
+        }
+        spin_unlock(&block_group->lock);
+
+        num_pages = (int)div64_u64(block_group->key.offset, 1024 * 1024 * 1024);
+        if (!num_pages)
+                num_pages = 1;
+
+        /*
+         * Just to make absolutely sure we have enough space, we're going to
+         * preallocate 12 pages worth of space for each block group.  In
+         * practice we ought to use at most 8, but we need extra space so we can
+         * add our header and have a terminator between the extents and the
+         * bitmaps.
+         */
+        num_pages *= 16;
+        num_pages *= PAGE_CACHE_SIZE;
+
+        ret = btrfs_check_data_free_space(inode, num_pages);
+        if (ret)
+                goto out_put;
+
+        ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, num_pages,
+                                              num_pages, num_pages,
+                                              &alloc_hint);
+        btrfs_free_reserved_data_space(inode, num_pages);
+out_put:
+        iput(inode);
+out_free:
+        btrfs_release_path(root, path);
+out:
+        spin_lock(&block_group->lock);
+        if (ret)
+                block_group->disk_cache_state = BTRFS_DC_ERROR;
+        else
+                block_group->disk_cache_state = BTRFS_DC_SETUP;
+        spin_unlock(&block_group->lock);
+
+        return ret;
+}
+
 int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root)
 {
@@ -2700,6 +2803,25 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
         if (!path)
                 return -ENOMEM;
 
+again:
+        while (1) {
+                cache = btrfs_lookup_first_block_group(root->fs_info, last);
+                while (cache) {
+                        if (cache->disk_cache_state == BTRFS_DC_CLEAR)
+                                break;
+                        cache = next_block_group(root, cache);
+                }
+                if (!cache) {
+                        if (last == 0)
+                                break;
+                        last = 0;
+                        continue;
+                }
+                err = cache_save_setup(cache, trans, path);
+                last = cache->key.objectid + cache->key.offset;
+                btrfs_put_block_group(cache);
+        }
+
         while (1) {
                 if (last == 0) {
                         err = btrfs_run_delayed_refs(trans, root,
@@ -2709,6 +2831,11 @@ int btrfs_write_dirty_block_groups(struct btrfs_trans_handle *trans,
 
                 cache = btrfs_lookup_first_block_group(root->fs_info, last);
                 while (cache) {
+                        if (cache->disk_cache_state == BTRFS_DC_CLEAR) {
+                                btrfs_put_block_group(cache);
+                                goto again;
+                        }
+
                         if (cache->dirty)
                                 break;
                         cache = next_block_group(root, cache);
@@ -2883,11 +3010,16 @@ int btrfs_check_data_free_space(struct inode *inode, u64 bytes)
         struct btrfs_space_info *data_sinfo;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         u64 used;
-        int ret = 0, committed = 0;
+        int ret = 0, committed = 0, alloc_chunk = 1;
 
         /* make sure bytes are sectorsize aligned */
         bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
 
+        if (root == root->fs_info->tree_root) {
+                alloc_chunk = 0;
+                committed = 1;
+        }
+
         data_sinfo = BTRFS_I(inode)->space_info;
         if (!data_sinfo)
                 goto alloc;
@@ -2906,7 +3038,7 @@ again:
                  * if we don't have enough free bytes in this space then we need
                  * to alloc a new chunk.
                  */
-                if (!data_sinfo->full) {
+                if (!data_sinfo->full && alloc_chunk) {
                         u64 alloc_target;
 
                         data_sinfo->force_alloc = 1;
@@ -3777,12 +3909,12 @@ static int update_block_group(struct btrfs_trans_handle *trans,
                               struct btrfs_root *root,
                               u64 bytenr, u64 num_bytes, int alloc)
 {
-        struct btrfs_block_group_cache *cache;
+        struct btrfs_block_group_cache *cache = NULL;
         struct btrfs_fs_info *info = root->fs_info;
-        int factor;
         u64 total = num_bytes;
         u64 old_val;
         u64 byte_in_group;
+        int factor;
 
         /* block accounting for super block */
         spin_lock(&info->delalloc_lock);
@@ -3804,11 +3936,17 @@ static int update_block_group(struct btrfs_trans_handle *trans,
                         factor = 2;
                 else
                         factor = 1;
+
                 byte_in_group = bytenr - cache->key.objectid;
                 WARN_ON(byte_in_group > cache->key.offset);
 
                 spin_lock(&cache->space_info->lock);
                 spin_lock(&cache->lock);
+
+                if (btrfs_super_cache_generation(&info->super_copy) != 0 &&
+                    cache->disk_cache_state < BTRFS_DC_CLEAR)
+                        cache->disk_cache_state = BTRFS_DC_CLEAR;
+
                 cache->dirty = 1;
                 old_val = btrfs_block_group_used(&cache->item);
                 num_bytes = min(total, cache->key.offset - byte_in_group);
@@ -7814,6 +7952,40 @@ out:
         return ret;
 }
 
+void btrfs_put_block_group_cache(struct btrfs_fs_info *info)
+{
+        struct btrfs_block_group_cache *block_group;
+        u64 last = 0;
+
+        while (1) {
+                struct inode *inode;
+
+                block_group = btrfs_lookup_first_block_group(info, last);
+                while (block_group) {
+                        spin_lock(&block_group->lock);
+                        if (block_group->iref)
+                                break;
+                        spin_unlock(&block_group->lock);
+                        block_group = next_block_group(info->tree_root,
+                                                       block_group);
+                }
+                if (!block_group) {
+                        if (last == 0)
+                                break;
+                        last = 0;
+                        continue;
+                }
+
+                inode = block_group->inode;
+                block_group->iref = 0;
+                block_group->inode = NULL;
+                spin_unlock(&block_group->lock);
+                iput(inode);
+                last = block_group->key.objectid + block_group->key.offset;
+                btrfs_put_block_group(block_group);
+        }
+}
+
 int btrfs_free_block_groups(struct btrfs_fs_info *info)
 {
         struct btrfs_block_group_cache *block_group;
@@ -7897,6 +8069,8 @@ int btrfs_read_block_groups(struct btrfs_root *root)
         struct btrfs_key key;
         struct btrfs_key found_key;
         struct extent_buffer *leaf;
+        int need_clear = 0;
+        u64 cache_gen;
 
         root = info->extent_root;
         key.objectid = 0;
@@ -7906,6 +8080,11 @@ int btrfs_read_block_groups(struct btrfs_root *root)
         if (!path)
                 return -ENOMEM;
 
+        cache_gen = btrfs_super_cache_generation(&root->fs_info->super_copy);
+        if (cache_gen != 0 &&
+            btrfs_super_generation(&root->fs_info->super_copy) != cache_gen)
+                need_clear = 1;
+
         while (1) {
                 ret = find_first_block_group(root, path, &key);
                 if (ret > 0)
@@ -7928,6 +8107,9 @@ int btrfs_read_block_groups(struct btrfs_root *root)
                 INIT_LIST_HEAD(&cache->list);
                 INIT_LIST_HEAD(&cache->cluster_list);
 
+                if (need_clear)
+                        cache->disk_cache_state = BTRFS_DC_CLEAR;
+
                 /*
                  * we only want to have 32k of ram per block group for keeping
                  * track of free space, and if we pass 1/2 of that we want to
@@ -8032,6 +8214,7 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
         cache->key.offset = size;
         cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
         cache->sectorsize = root->sectorsize;
+        cache->fs_info = root->fs_info;
 
         /*
          * we only want to have 32k of ram per block group for keeping track
@@ -8088,7 +8271,9 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
         struct btrfs_path *path;
         struct btrfs_block_group_cache *block_group;
         struct btrfs_free_cluster *cluster;
+        struct btrfs_root *tree_root = root->fs_info->tree_root;
         struct btrfs_key key;
+        struct inode *inode;
         int ret;
 
         root = root->fs_info->extent_root;
@@ -8097,8 +8282,6 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
         BUG_ON(!block_group);
         BUG_ON(!block_group->ro);
 
-        memcpy(&key, &block_group->key, sizeof(key));
-
         /* make sure this block group isn't part of an allocation cluster */
         cluster = &root->fs_info->data_alloc_cluster;
         spin_lock(&cluster->refill_lock);
@@ -8117,6 +8300,40 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
         path = btrfs_alloc_path();
         BUG_ON(!path);
 
+        inode = lookup_free_space_inode(root, block_group, path);
+        if (!IS_ERR(inode)) {
+                btrfs_orphan_add(trans, inode);
+                clear_nlink(inode);
+                /* One for the block groups ref */
+                spin_lock(&block_group->lock);
+                if (block_group->iref) {
+                        block_group->iref = 0;
+                        block_group->inode = NULL;
+                        spin_unlock(&block_group->lock);
+                        iput(inode);
+                } else {
+                        spin_unlock(&block_group->lock);
+                }
+                /* One for our lookup ref */
+                iput(inode);
+        }
+
+        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+        key.offset = block_group->key.objectid;
+        key.type = 0;
+
+        ret = btrfs_search_slot(trans, tree_root, &key, path, -1, 1);
+        if (ret < 0)
+                goto out;
+        if (ret > 0)
+                btrfs_release_path(tree_root, path);
+        if (ret == 0) {
+                ret = btrfs_del_item(trans, tree_root, path);
+                if (ret)
+                        goto out;
+                btrfs_release_path(tree_root, path);
+        }
+
         spin_lock(&root->fs_info->block_group_cache_lock);
         rb_erase(&block_group->cache_node,
                  &root->fs_info->block_group_cache_tree);
@@ -8140,6 +8357,8 @@ int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
         block_group->space_info->bytes_readonly -= block_group->key.offset;
         spin_unlock(&block_group->space_info->lock);
 
+        memcpy(&key, &block_group->key, sizeof(key));
+
         btrfs_clear_space_info_full(root->fs_info);
 
         btrfs_put_block_group(block_group);
diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index f488fac04d99..05efcc7061a7 100644
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -23,10 +23,165 @@
 #include "ctree.h"
 #include "free-space-cache.h"
 #include "transaction.h"
+#include "disk-io.h"
 
 #define BITS_PER_BITMAP         (PAGE_CACHE_SIZE * 8)
 #define MAX_CACHE_BYTES_PER_GIG (32 * 1024)
 
+struct inode *lookup_free_space_inode(struct btrfs_root *root,
+                                      struct btrfs_block_group_cache
+                                      *block_group, struct btrfs_path *path)
+{
+        struct btrfs_key key;
+        struct btrfs_key location;
+        struct btrfs_disk_key disk_key;
+        struct btrfs_free_space_header *header;
+        struct extent_buffer *leaf;
+        struct inode *inode = NULL;
+        int ret;
+
+        spin_lock(&block_group->lock);
+        if (block_group->inode)
+                inode = igrab(block_group->inode);
+        spin_unlock(&block_group->lock);
+        if (inode)
+                return inode;
+
+        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+        key.offset = block_group->key.objectid;
+        key.type = 0;
+
+        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (ret < 0)
+                return ERR_PTR(ret);
+        if (ret > 0) {
+                btrfs_release_path(root, path);
+                return ERR_PTR(-ENOENT);
+        }
+
+        leaf = path->nodes[0];
+        header = btrfs_item_ptr(leaf, path->slots[0],
+                                struct btrfs_free_space_header);
+        btrfs_free_space_key(leaf, header, &disk_key);
+        btrfs_disk_key_to_cpu(&location, &disk_key);
+        btrfs_release_path(root, path);
+
+        inode = btrfs_iget(root->fs_info->sb, &location, root, NULL);
+        if (!inode)
+                return ERR_PTR(-ENOENT);
+        if (IS_ERR(inode))
+                return inode;
+        if (is_bad_inode(inode)) {
+                iput(inode);
+                return ERR_PTR(-ENOENT);
+        }
+
+        spin_lock(&block_group->lock);
+        if (!root->fs_info->closing) {
+                block_group->inode = igrab(inode);
+                block_group->iref = 1;
+        }
+        spin_unlock(&block_group->lock);
+
+        return inode;
+}
+
+int create_free_space_inode(struct btrfs_root *root,
+                            struct btrfs_trans_handle *trans,
+                            struct btrfs_block_group_cache *block_group,
+                            struct btrfs_path *path)
+{
+        struct btrfs_key key;
+        struct btrfs_disk_key disk_key;
+        struct btrfs_free_space_header *header;
+        struct btrfs_inode_item *inode_item;
+        struct extent_buffer *leaf;
+        u64 objectid;
+        int ret;
+
+        ret = btrfs_find_free_objectid(trans, root, 0, &objectid);
+        if (ret < 0)
+                return ret;
+
+        ret = btrfs_insert_empty_inode(trans, root, path, objectid);
+        if (ret)
+                return ret;
+
+        leaf = path->nodes[0];
+        inode_item = btrfs_item_ptr(leaf, path->slots[0],
+                                    struct btrfs_inode_item);
+        btrfs_item_key(leaf, &disk_key, path->slots[0]);
+        memset_extent_buffer(leaf, 0, (unsigned long)inode_item,
+                             sizeof(*inode_item));
+        btrfs_set_inode_generation(leaf, inode_item, trans->transid);
+        btrfs_set_inode_size(leaf, inode_item, 0);
+        btrfs_set_inode_nbytes(leaf, inode_item, 0);
+        btrfs_set_inode_uid(leaf, inode_item, 0);
+        btrfs_set_inode_gid(leaf, inode_item, 0);
+        btrfs_set_inode_mode(leaf, inode_item, S_IFREG | 0600);
+        btrfs_set_inode_flags(leaf, inode_item, BTRFS_INODE_NOCOMPRESS |
+                              BTRFS_INODE_PREALLOC | BTRFS_INODE_NODATASUM);
+        btrfs_set_inode_nlink(leaf, inode_item, 1);
+        btrfs_set_inode_transid(leaf, inode_item, trans->transid);
+        btrfs_set_inode_block_group(leaf, inode_item,
+                                    block_group->key.objectid);
+        btrfs_mark_buffer_dirty(leaf);
+        btrfs_release_path(root, path);
+
+        key.objectid = BTRFS_FREE_SPACE_OBJECTID;
+        key.offset = block_group->key.objectid;
+        key.type = 0;
+
+        ret = btrfs_insert_empty_item(trans, root, path, &key,
+                                      sizeof(struct btrfs_free_space_header));
+        if (ret < 0) {
+                btrfs_release_path(root, path);
+                return ret;
+        }
+        leaf = path->nodes[0];
+        header = btrfs_item_ptr(leaf, path->slots[0],
+                                struct btrfs_free_space_header);
+        memset_extent_buffer(leaf, 0, (unsigned long)header, sizeof(*header));
+        btrfs_set_free_space_key(leaf, header, &disk_key);
+        btrfs_mark_buffer_dirty(leaf);
+        btrfs_release_path(root, path);
+
+        return 0;
+}
+
+int btrfs_truncate_free_space_cache(struct btrfs_root *root,
+                                    struct btrfs_trans_handle *trans,
+                                    struct btrfs_path *path,
+                                    struct inode *inode)
+{
+        loff_t oldsize;
+        int ret = 0;
+
+        trans->block_rsv = root->orphan_block_rsv;
+        ret = btrfs_block_rsv_check(trans, root,
+                                    root->orphan_block_rsv,
+                                    0, 5);
+        if (ret)
+                return ret;
+
+        oldsize = i_size_read(inode);
+        btrfs_i_size_write(inode, 0);
+        truncate_pagecache(inode, oldsize, 0);
+
+        /*
+         * We don't need an orphan item because truncating the free space cache
+         * will never be split across transactions.
+         */
+        ret = btrfs_truncate_inode_items(trans, root, inode,
+                                         0, BTRFS_EXTENT_DATA_KEY);
+        if (ret) {
+                WARN_ON(1);
+                return ret;
+        }
+
+        return btrfs_update_inode(trans, root, inode);
+}
+
 static inline unsigned long offset_to_bit(u64 bitmap_start, u64 sectorsize,
                                           u64 offset)
 {
diff --git a/fs/btrfs/free-space-cache.h b/fs/btrfs/free-space-cache.h
index 890a8e79011b..45be29e5f01e 100644
--- a/fs/btrfs/free-space-cache.h
+++ b/fs/btrfs/free-space-cache.h
@@ -27,6 +27,17 @@ struct btrfs_free_space {
         struct list_head list;
 };
 
+struct inode *lookup_free_space_inode(struct btrfs_root *root,
+                                      struct btrfs_block_group_cache
+                                      *block_group, struct btrfs_path *path);
+int create_free_space_inode(struct btrfs_root *root,
+                            struct btrfs_trans_handle *trans,
+                            struct btrfs_block_group_cache *block_group,
+                            struct btrfs_path *path);
+int btrfs_truncate_free_space_cache(struct btrfs_root *root,
+                                    struct btrfs_trans_handle *trans,
+                                    struct btrfs_path *path,
+                                    struct inode *inode);
 int btrfs_add_free_space(struct btrfs_block_group_cache *block_group,
                          u64 bytenr, u64 size);
 int btrfs_remove_free_space(struct btrfs_block_group_cache *block_group,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c03864406af3..1af1ea88e8a8 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1700,6 +1700,7 @@ static int btrfs_finish_ordered_io(struct inode *inode, u64 start, u64 end)
                                                 ordered_extent->len);
                 BUG_ON(ret);
         } else {
+                BUG_ON(root == root->fs_info->tree_root);
                 ret = insert_reserved_file_extent(trans, inode,
                                                 ordered_extent->file_offset,
                                                 ordered_extent->start,
@@ -3196,7 +3197,7 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle *trans,
 
         BUG_ON(new_size > 0 && min_type != BTRFS_EXTENT_DATA_KEY);
 
-        if (root->ref_cows)
+        if (root->ref_cows || root == root->fs_info->tree_root)
                 btrfs_drop_extent_cache(inode, new_size & (~mask), (u64)-1, 0);
 
         path = btrfs_alloc_path();
@@ -3344,7 +3345,8 @@ delete:
                 } else {
                         break;
                 }
-                if (found_extent && root->ref_cows) {
+                if (found_extent && (root->ref_cows ||
+                                     root == root->fs_info->tree_root)) {
                         btrfs_set_path_blocking(path);
                         ret = btrfs_free_extent(trans, root, extent_start,
                                                 extent_num_bytes, 0,
@@ -3675,7 +3677,8 @@ void btrfs_evict_inode(struct inode *inode)
         int ret;
 
         truncate_inode_pages(&inode->i_data, 0);
-        if (inode->i_nlink && btrfs_root_refs(&root->root_item) != 0)
+        if (inode->i_nlink && (btrfs_root_refs(&root->root_item) != 0 ||
+                               root == root->fs_info->tree_root))
                 goto no_delete;
 
         if (is_bad_inode(inode)) {
@@ -3888,7 +3891,14 @@ static void inode_tree_del(struct inode *inode)
         }
         spin_unlock(&root->inode_lock);
 
-        if (empty && btrfs_root_refs(&root->root_item) == 0) {
+        /*
+         * Free space cache has inodes in the tree root, but the tree root has a
+         * root_refs of 0, so this could end up dropping the tree root as a
+         * snapshot, so we need the extra !root->fs_info->tree_root check to
+         * make sure we don't drop it.
+         */
+        if (empty && btrfs_root_refs(&root->root_item) == 0 &&
+            root != root->fs_info->tree_root) {
                 synchronize_srcu(&root->fs_info->subvol_srcu);
                 spin_lock(&root->inode_lock);
                 empty = RB_EMPTY_ROOT(&root->inode_tree);
@@ -4282,14 +4292,24 @@ int btrfs_write_inode(struct inode *inode, struct writeback_control *wbc)
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_trans_handle *trans;
         int ret = 0;
+        bool nolock = false;
 
         if (BTRFS_I(inode)->dummy_inode)
                 return 0;
 
+        smp_mb();
+        nolock = (root->fs_info->closing && root == root->fs_info->tree_root);
+
         if (wbc->sync_mode == WB_SYNC_ALL) {
-                trans = btrfs_join_transaction(root, 1);
+                if (nolock)
+                        trans = btrfs_join_transaction_nolock(root, 1);
+                else
+                        trans = btrfs_join_transaction(root, 1);
                 btrfs_set_trans_block_group(trans, inode);
-                ret = btrfs_commit_transaction(trans, root);
+                if (nolock)
+                        ret = btrfs_end_transaction_nolock(trans, root);
+                else
+                        ret = btrfs_commit_transaction(trans, root);
         }
         return ret;
 }
@@ -6308,6 +6328,21 @@ void btrfs_destroy_inode(struct inode *inode)
                 spin_unlock(&root->fs_info->ordered_extent_lock);
         }
 
+        if (root == root->fs_info->tree_root) {
+                struct btrfs_block_group_cache *block_group;
+
+                block_group = btrfs_lookup_block_group(root->fs_info,
+                                                BTRFS_I(inode)->block_group);
+                if (block_group && block_group->inode == inode) {
+                        spin_lock(&block_group->lock);
+                        block_group->inode = NULL;
+                        spin_unlock(&block_group->lock);
+                        btrfs_put_block_group(block_group);
+                } else if (block_group) {
+                        btrfs_put_block_group(block_group);
+                }
+        }
+
         spin_lock(&root->orphan_lock);
         if (!list_empty(&BTRFS_I(inode)->i_orphan)) {
                 printk(KERN_INFO "BTRFS: inode %lu still on the orphan list\n",
@@ -6340,7 +6375,8 @@ int btrfs_drop_inode(struct inode *inode)
 {
         struct btrfs_root *root = BTRFS_I(inode)->root;
 
-        if (btrfs_root_refs(&root->root_item) == 0)
+        if (btrfs_root_refs(&root->root_item) == 0 &&
+            root != root->fs_info->tree_root)
                 return 1;
         else
                 return generic_drop_inode(inode);
@@ -6757,27 +6793,33 @@ out_unlock:
         return err;
 }
 
-int btrfs_prealloc_file_range(struct inode *inode, int mode,
-                              u64 start, u64 num_bytes, u64 min_size,
-                              loff_t actual_len, u64 *alloc_hint)
+static int __btrfs_prealloc_file_range(struct inode *inode, int mode,
+                                       u64 start, u64 num_bytes, u64 min_size,
+                                       loff_t actual_len, u64 *alloc_hint,
+                                       struct btrfs_trans_handle *trans)
 {
-        struct btrfs_trans_handle *trans;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_key ins;
         u64 cur_offset = start;
         int ret = 0;
+        bool own_trans = true;
 
+        if (trans)
+                own_trans = false;
         while (num_bytes > 0) {
-                trans = btrfs_start_transaction(root, 3);
-                if (IS_ERR(trans)) {
-                        ret = PTR_ERR(trans);
-                        break;
+                if (own_trans) {
+                        trans = btrfs_start_transaction(root, 3);
+                        if (IS_ERR(trans)) {
+                                ret = PTR_ERR(trans);
+                                break;
+                        }
                 }
 
                 ret = btrfs_reserve_extent(trans, root, num_bytes, min_size,
                                            0, *alloc_hint, (u64)-1, &ins, 1);
                 if (ret) {
-                        btrfs_end_transaction(trans, root);
+                        if (own_trans)
+                                btrfs_end_transaction(trans, root);
                         break;
                 }
 
@@ -6810,11 +6852,30 @@ int btrfs_prealloc_file_range(struct inode *inode, int mode,
                 ret = btrfs_update_inode(trans, root, inode);
                 BUG_ON(ret);
 
-                btrfs_end_transaction(trans, root);
+                if (own_trans)
+                        btrfs_end_transaction(trans, root);
         }
         return ret;
 }
 
+int btrfs_prealloc_file_range(struct inode *inode, int mode,
+                              u64 start, u64 num_bytes, u64 min_size,
+                              loff_t actual_len, u64 *alloc_hint)
+{
+        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
+                                           min_size, actual_len, alloc_hint,
+                                           NULL);
+}
+
+int btrfs_prealloc_file_range_trans(struct inode *inode,
+                                    struct btrfs_trans_handle *trans, int mode,
+                                    u64 start, u64 num_bytes, u64 min_size,
+                                    loff_t actual_len, u64 *alloc_hint)
+{
+        return __btrfs_prealloc_file_range(inode, mode, start, num_bytes,
+                                           min_size, actual_len, alloc_hint, trans);
+}
+
 static long btrfs_fallocate(struct inode *inode, int mode,
                             loff_t offset, loff_t len)
 {
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index b37d723b9d4a..af339eee55b8 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -29,6 +29,7 @@
 #include "locking.h"
 #include "btrfs_inode.h"
 #include "async-thread.h"
+#include "free-space-cache.h"
 
 /*
  * backref_node, mapping_node and tree_block start with this
@@ -3191,6 +3192,54 @@ static int block_use_full_backref(struct reloc_control *rc,
         return ret;
 }
 
+static int delete_block_group_cache(struct btrfs_fs_info *fs_info,
+                                    struct inode *inode, u64 ino)
+{
+        struct btrfs_key key;
+        struct btrfs_path *path;
+        struct btrfs_root *root = fs_info->tree_root;
+        struct btrfs_trans_handle *trans;
+        unsigned long nr;
+        int ret = 0;
+
+        if (inode)
+                goto truncate;
+
+        key.objectid = ino;
+        key.type = BTRFS_INODE_ITEM_KEY;
+        key.offset = 0;
+
+        inode = btrfs_iget(fs_info->sb, &key, root, NULL);
+        if (!inode || IS_ERR(inode) || is_bad_inode(inode)) {
+                if (inode && !IS_ERR(inode))
+                        iput(inode);
+                return -ENOENT;
+        }
+
+truncate:
+        path = btrfs_alloc_path();
+        if (!path) {
+                ret = -ENOMEM;
+                goto out;
+        }
+
+        trans = btrfs_join_transaction(root, 0);
+        if (IS_ERR(trans)) {
+                btrfs_free_path(path);
+                goto out;
+        }
+
+        ret = btrfs_truncate_free_space_cache(root, trans, path, inode);
+
+        btrfs_free_path(path);
+        nr = trans->blocks_used;
+        btrfs_end_transaction(trans, root);
+        btrfs_btree_balance_dirty(root, nr);
+out:
+        iput(inode);
+        return ret;
+}
+
 /*
  * helper to add tree blocks for backref of type BTRFS_EXTENT_DATA_REF_KEY
  * this function scans fs tree to find blocks reference the data extent
@@ -3217,15 +3266,27 @@ static int find_data_references(struct reloc_control *rc,
         int counted;
         int ret;
 
-        path = btrfs_alloc_path();
-        if (!path)
-                return -ENOMEM;
-
         ref_root = btrfs_extent_data_ref_root(leaf, ref);
         ref_objectid = btrfs_extent_data_ref_objectid(leaf, ref);
         ref_offset = btrfs_extent_data_ref_offset(leaf, ref);
         ref_count = btrfs_extent_data_ref_count(leaf, ref);
 
+        /*
+         * This is an extent belonging to the free space cache, lets just delete
+         * it and redo the search.
+         */
+        if (ref_root == BTRFS_ROOT_TREE_OBJECTID) {
+                ret = delete_block_group_cache(rc->extent_root->fs_info,
+                                               NULL, ref_objectid);
+                if (ret != -ENOENT)
+                        return ret;
+                ret = 0;
+        }
+
+        path = btrfs_alloc_path();
+        if (!path)
+                return -ENOMEM;
+
         root = read_fs_root(rc->extent_root->fs_info, ref_root);
         if (IS_ERR(root)) {
                 err = PTR_ERR(root);
@@ -3860,6 +3921,8 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
 {
         struct btrfs_fs_info *fs_info = extent_root->fs_info;
         struct reloc_control *rc;
+        struct inode *inode;
+        struct btrfs_path *path;
         int ret;
         int rw = 0;
         int err = 0;
@@ -3882,6 +3945,26 @@ int btrfs_relocate_block_group(struct btrfs_root *extent_root, u64 group_start)
                 rw = 1;
         }
 
+        path = btrfs_alloc_path();
+        if (!path) {
+                err = -ENOMEM;
+                goto out;
+        }
+
+        inode = lookup_free_space_inode(fs_info->tree_root, rc->block_group,
+                                        path);
+        btrfs_free_path(path);
+
+        if (!IS_ERR(inode))
+                ret = delete_block_group_cache(fs_info, inode, 0);
+        else
+                ret = PTR_ERR(inode);
+
+        if (ret && ret != -ENOENT) {
+                err = ret;
+                goto out;
+        }
+
         rc->data_inode = create_reloc_inode(fs_info, rc->block_group);
         if (IS_ERR(rc->data_inode)) {
                 err = PTR_ERR(rc->data_inode);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 1776dbd8dc98..5c23eb8d6ba3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -68,7 +68,7 @@ enum {
         Opt_nodatacow, Opt_max_inline, Opt_alloc_start, Opt_nobarrier, Opt_ssd,
         Opt_nossd, Opt_ssd_spread, Opt_thread_pool, Opt_noacl, Opt_compress,
         Opt_compress_force, Opt_notreelog, Opt_ratio, Opt_flushoncommit,
-        Opt_discard, Opt_err,
+        Opt_discard, Opt_space_cache, Opt_err,
 };
 
 static match_table_t tokens = {
@@ -92,6 +92,7 @@ static match_table_t tokens = {
         {Opt_flushoncommit, "flushoncommit"},
         {Opt_ratio, "metadata_ratio=%d"},
         {Opt_discard, "discard"},
+        {Opt_space_cache, "space_cache"},
         {Opt_err, NULL},
 };
 
@@ -235,6 +236,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
                 case Opt_discard:
                         btrfs_set_opt(info->mount_opt, DISCARD);
                         break;
+                case Opt_space_cache:
+                        printk(KERN_INFO "btrfs: enabling disk space caching\n");
+                        btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+                        break;
                 case Opt_err:
                         printk(KERN_INFO "btrfs: unrecognized mount option "
                                "'%s'\n", p);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 66e4c66cc63b..e7144c48ed79 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -163,6 +163,7 @@ enum btrfs_trans_type {
         TRANS_START,
         TRANS_JOIN,
         TRANS_USERSPACE,
+        TRANS_JOIN_NOLOCK,
 };
 
 static int may_wait_transaction(struct btrfs_root *root, int type)
@@ -186,7 +187,8 @@ again:
         if (!h)
                 return ERR_PTR(-ENOMEM);
 
-        mutex_lock(&root->fs_info->trans_mutex);
+        if (type != TRANS_JOIN_NOLOCK)
+                mutex_lock(&root->fs_info->trans_mutex);
         if (may_wait_transaction(root, type))
                 wait_current_trans(root);
 
@@ -195,7 +197,8 @@ again:
 
         cur_trans = root->fs_info->running_transaction;
         cur_trans->use_count++;
-        mutex_unlock(&root->fs_info->trans_mutex);
+        if (type != TRANS_JOIN_NOLOCK)
+                mutex_unlock(&root->fs_info->trans_mutex);
 
         h->transid = cur_trans->transid;
         h->transaction = cur_trans;
@@ -224,9 +227,11 @@ again:
                 }
         }
 
-        mutex_lock(&root->fs_info->trans_mutex);
+        if (type != TRANS_JOIN_NOLOCK)
+                mutex_lock(&root->fs_info->trans_mutex);
         record_root_in_trans(h, root);
-        mutex_unlock(&root->fs_info->trans_mutex);
+        if (type != TRANS_JOIN_NOLOCK)
+                mutex_unlock(&root->fs_info->trans_mutex);
 
         if (!current->journal_info && type != TRANS_USERSPACE)
                 current->journal_info = h;
@@ -244,6 +249,12 @@ struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
         return start_transaction(root, 0, TRANS_JOIN);
 }
 
+struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root,
+                                                          int num_blocks)
+{
+        return start_transaction(root, 0, TRANS_JOIN_NOLOCK);
+}
+
 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
                                                          int num_blocks)
 {
@@ -348,7 +359,7 @@ int btrfs_should_end_transaction(struct btrfs_trans_handle *trans,
 }
 
 static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
-                          struct btrfs_root *root, int throttle)
+                          struct btrfs_root *root, int throttle, int lock)
 {
         struct btrfs_transaction *cur_trans = trans->transaction;
         struct btrfs_fs_info *info = root->fs_info;
@@ -376,18 +387,19 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 
         btrfs_trans_release_metadata(trans, root);
 
-        if (!root->fs_info->open_ioctl_trans &&
+        if (lock && !root->fs_info->open_ioctl_trans &&
             should_end_transaction(trans, root))
                 trans->transaction->blocked = 1;
 
-        if (cur_trans->blocked && !cur_trans->in_commit) {
+        if (lock && cur_trans->blocked && !cur_trans->in_commit) {
                 if (throttle)
                         return btrfs_commit_transaction(trans, root);
                 else
                         wake_up_process(info->transaction_kthread);
         }
 
-        mutex_lock(&info->trans_mutex);
+        if (lock)
+                mutex_lock(&info->trans_mutex);
         WARN_ON(cur_trans != info->running_transaction);
         WARN_ON(cur_trans->num_writers < 1);
         cur_trans->num_writers--;
@@ -395,7 +407,8 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
         if (waitqueue_active(&cur_trans->writer_wait))
                 wake_up(&cur_trans->writer_wait);
         put_transaction(cur_trans);
-        mutex_unlock(&info->trans_mutex);
+        if (lock)
+                mutex_unlock(&info->trans_mutex);
 
         if (current->journal_info == trans)
                 current->journal_info = NULL;
@@ -411,13 +424,19 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root)
 {
-        return __btrfs_end_transaction(trans, root, 0);
+        return __btrfs_end_transaction(trans, root, 0, 1);
 }
 
 int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans,
                                    struct btrfs_root *root)
 {
-        return __btrfs_end_transaction(trans, root, 1);
+        return __btrfs_end_transaction(trans, root, 1, 1);
+}
+
+int btrfs_end_transaction_nolock(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root)
+{
+        return __btrfs_end_transaction(trans, root, 0, 0);
 }
 
 /*
@@ -966,6 +985,8 @@ static void update_super_roots(struct btrfs_root *root)
         super->root = root_item->bytenr;
         super->generation = root_item->generation;
         super->root_level = root_item->level;
+        if (super->cache_generation != 0 || btrfs_test_opt(root, SPACE_CACHE))
+                super->cache_generation = root_item->generation;
 }
 
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index e104986d0bfd..15f83e1c1ef7 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -87,10 +87,14 @@ static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
 
 int btrfs_end_transaction(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root);
+int btrfs_end_transaction_nolock(struct btrfs_trans_handle *trans,
+                                 struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
                                                    int num_items);
 struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
                                                   int num_blocks);
+struct btrfs_trans_handle *btrfs_join_transaction_nolock(struct btrfs_root *root,
+                                                          int num_blocks);
 struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r,
                                                          int num_blocks);
 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,