Btrfs: fix race in tree mod log addition

[cascardo/linux.git] / fs / btrfs / ctree.c

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cb76b2a..04b06bc 100644 (file)
--- 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 *