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authorJan Schmidt <list.btrfs@jan-o-sch.net>2012-06-11 10:52:38 +0200
committerJan Schmidt <list.btrfs@jan-o-sch.net>2012-06-14 18:52:39 +0200
commit3310c36eef330766fd23d50796287ad764929e24 (patch)
tree536c3d52b7ff1044d0a00ca86fd436c846d486ab
parent3d7806eca43e73a9721d2e09369200ed93036bd0 (diff)
downloadlinux-stericsson-3310c36eef330766fd23d50796287ad764929e24.tar.gz
Btrfs: fix race in tree mod log addition
When adding to the tree modification log, we grab two locks at different stages. We must not drop the outer lock until we're done with section protected by the inner lock. This moves the unlock call for the outer lock to the appropriate position. Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
-rw-r--r--fs/btrfs/ctree.c23
1 files changed, 19 insertions, 4 deletions
diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index cb76b2a1b908..04b06bcf2ca9 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 *