1 files changed, 64 insertions, 24 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index d7a96cfdc50a..15cbc2bf4ff0 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -467,6 +467,15 @@ static inline int tree_mod_dont_log(struct btrfs_fs_info *fs_info,
         return 0;
 }
 
+/*
+ * This allocates memory and gets a tree modification sequence number when
+ * needed.
+ *
+ * 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.
+ */
 static inline int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
                                  struct tree_mod_elem **tm_ret)
 {
@@ -491,11 +500,11 @@ static inline int tree_mod_alloc(struct btrfs_fs_info *fs_info, gfp_t flags,
                  */
                 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;
         }
-        spin_unlock(&fs_info->tree_mod_seq_lock);
 
         return seq;
 }
@@ -521,7 +530,9 @@ tree_mod_log_insert_key_mask(struct btrfs_fs_info *fs_info,
         tm->slot = slot;
         tm->generation = btrfs_node_ptr_generation(eb, slot);
 
-        return __tree_mod_log_insert(fs_info, tm);
+        ret = __tree_mod_log_insert(fs_info, tm);
+        spin_unlock(&fs_info->tree_mod_seq_lock);
+        return ret;
 }
 
 static noinline int
@@ -559,7 +570,9 @@ tree_mod_log_insert_move(struct btrfs_fs_info *fs_info,
         tm->move.nr_items = nr_items;
         tm->op = MOD_LOG_MOVE_KEYS;
 
-        return __tree_mod_log_insert(fs_info, tm);
+        ret = __tree_mod_log_insert(fs_info, tm);
+        spin_unlock(&fs_info->tree_mod_seq_lock);
+        return ret;
 }
 
 static noinline int
@@ -580,7 +593,9 @@ tree_mod_log_insert_root(struct btrfs_fs_info *fs_info,
         tm->generation = btrfs_header_generation(old_root);
         tm->op = MOD_LOG_ROOT_REPLACE;
 
-        return __tree_mod_log_insert(fs_info, tm);
+        ret = __tree_mod_log_insert(fs_info, tm);
+        spin_unlock(&fs_info->tree_mod_seq_lock);
+        return ret;
 }
 
 static struct tree_mod_elem *
@@ -1023,6 +1038,10 @@ __tree_mod_log_oldest_root(struct btrfs_fs_info *fs_info,
                 looped = 1;
         }
 
+        /* if there's no old root to return, return what we found instead */
+        if (!found)
+                found = tm;
+
         return found;
 }
 
@@ -1143,22 +1162,36 @@ tree_mod_log_rewind(struct btrfs_fs_info *fs_info, struct extent_buffer *eb,
         return eb_rewin;
 }
 
+/*
+ * get_old_root() rewinds the state of @root's root node to the given @time_seq
+ * value. If there are no changes, the current root->root_node is returned. If
+ * anything changed in between, there's a fresh buffer allocated on which the
+ * rewind operations are done. In any case, the returned buffer is read locked.
+ * Returns NULL on error (with no locks held).
+ */
 static inline struct extent_buffer *
 get_old_root(struct btrfs_root *root, u64 time_seq)
 {
         struct tree_mod_elem *tm;
         struct extent_buffer *eb;
-        struct tree_mod_root *old_root;
-        u64 old_generation;
+        struct tree_mod_root *old_root = NULL;
+        u64 old_generation = 0;
+        u64 logical;
 
+        eb = btrfs_read_lock_root_node(root);
         tm = __tree_mod_log_oldest_root(root->fs_info, root, time_seq);
         if (!tm)
                 return root->node;
 
-        old_root = &tm->old_root;
-        old_generation = tm->generation;
+        if (tm->op == MOD_LOG_ROOT_REPLACE) {
+                old_root = &tm->old_root;
+                old_generation = tm->generation;
+                logical = old_root->logical;
+        } else {
+                logical = root->node->start;
+        }
 
-        tm = tree_mod_log_search(root->fs_info, old_root->logical, time_seq);
+        tm = tree_mod_log_search(root->fs_info, logical, time_seq);
         /*
          * there was an item in the log when __tree_mod_log_oldest_root
          * returned. this one must not go away, because the time_seq passed to
@@ -1166,22 +1199,25 @@ get_old_root(struct btrfs_root *root, u64 time_seq)
          */
         BUG_ON(!tm);
 
-        if (old_root->logical == root->node->start) {
-                /* there are logged operations for the current root */
-                eb = btrfs_clone_extent_buffer(root->node);
-        } else {
-                /* there's a root replace operation for the current root */
+        if (old_root)
                 eb = alloc_dummy_extent_buffer(tm->index << PAGE_CACHE_SHIFT,
                                                root->nodesize);
+        else
+                eb = btrfs_clone_extent_buffer(root->node);
+        btrfs_tree_read_unlock(root->node);
+        free_extent_buffer(root->node);
+        if (!eb)
+                return NULL;
+        btrfs_tree_read_lock(eb);
+        if (old_root) {
                 btrfs_set_header_bytenr(eb, eb->start);
                 btrfs_set_header_backref_rev(eb, BTRFS_MIXED_BACKREF_REV);
                 btrfs_set_header_owner(eb, root->root_key.objectid);
+                btrfs_set_header_level(eb, old_root->level);
+                btrfs_set_header_generation(eb, old_generation);
         }
-        if (!eb)
-                return NULL;
-        btrfs_set_header_level(eb, old_root->level);
-        btrfs_set_header_generation(eb, old_generation);
         __tree_mod_log_rewind(eb, time_seq, tm);
+        extent_buffer_get(eb);
 
         return eb;
 }
@@ -1650,8 +1686,6 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
             BTRFS_NODEPTRS_PER_BLOCK(root) / 4)
                 return 0;
 
-        btrfs_header_nritems(mid);
-
         left = read_node_slot(root, parent, pslot - 1);
         if (left) {
                 btrfs_tree_lock(left);
@@ -1681,7 +1715,6 @@ static noinline int balance_level(struct btrfs_trans_handle *trans,
                 wret = push_node_left(trans, root, left, mid, 1);
                 if (wret < 0)
                         ret = wret;
-                btrfs_header_nritems(mid);
         }
 
         /*
@@ -2615,9 +2648,7 @@ int btrfs_search_old_slot(struct btrfs_root *root, struct btrfs_key *key,
 
 again:
         b = get_old_root(root, time_seq);
-        extent_buffer_get(b);
         level = btrfs_header_level(b);
-        btrfs_tree_read_lock(b);
         p->locks[level] = BTRFS_READ_LOCK;
 
         while (b) {
@@ -5001,6 +5032,12 @@ next:
  */
 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
 {
+        return btrfs_next_old_leaf(root, path, 0);
+}
+
+int btrfs_next_old_leaf(struct btrfs_root *root, struct btrfs_path *path,
+                        u64 time_seq)
+{
         int slot;
         int level;
         struct extent_buffer *c;
@@ -5025,7 +5062,10 @@ again:
         path->keep_locks = 1;
         path->leave_spinning = 1;
 
-        ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+        if (time_seq)
+                ret = btrfs_search_old_slot(root, &key, path, time_seq);
+        else
+                ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
         path->keep_locks = 0;
 
         if (ret < 0)