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authorLi Zefan <lizf@cn.fujitsu.com>2011-12-07 04:38:24 +0100
committerLi Zefan <lizf@cn.fujitsu.com>2012-01-11 03:26:54 +0100
commitb367e47fb3a70f5d24ebd6faf7d42436d485fb2d (patch)
tree5acc05bae14070f2dad3433a1482fe3a7bab0744
parentBtrfs: update global block_rsv when creating a new block group (diff)
downloadlinux-b367e47fb3a70f5d24ebd6faf7d42436d485fb2d.tar.xz
linux-b367e47fb3a70f5d24ebd6faf7d42436d485fb2d.zip
Btrfs: fix possible deadlock when opening a seed device
The correct lock order is uuid_mutex -> volume_mutex -> chunk_mutex, but when we mount a filesystem which has backing seed devices, we have this lock chain: open_ctree() lock(chunk_mutex); read_chunk_tree(); read_one_dev(); open_seed_devices(); lock(uuid_mutex); and then we hit a lockdep splat. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
-rw-r--r--fs/btrfs/disk-io.c2
-rw-r--r--fs/btrfs/volumes.c9
2 files changed, 7 insertions, 4 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 3f9d5551e582..858ab347413e 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2270,9 +2270,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
(unsigned long)btrfs_header_chunk_tree_uuid(chunk_root->node),
BTRFS_UUID_SIZE);
- mutex_lock(&fs_info->chunk_mutex);
ret = btrfs_read_chunk_tree(chunk_root);
- mutex_unlock(&fs_info->chunk_mutex);
if (ret) {
printk(KERN_WARNING "btrfs: failed to read chunk tree on %s\n",
sb->s_id);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 563ef650850e..fbb493b28d5a 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -3506,7 +3506,7 @@ static int open_seed_devices(struct btrfs_root *root, u8 *fsid)
struct btrfs_fs_devices *fs_devices;
int ret;
- mutex_lock(&uuid_mutex);
+ BUG_ON(!mutex_is_locked(&uuid_mutex));
fs_devices = root->fs_info->fs_devices->seed;
while (fs_devices) {
@@ -3544,7 +3544,6 @@ static int open_seed_devices(struct btrfs_root *root, u8 *fsid)
fs_devices->seed = root->fs_info->fs_devices->seed;
root->fs_info->fs_devices->seed = fs_devices;
out:
- mutex_unlock(&uuid_mutex);
return ret;
}
@@ -3687,6 +3686,9 @@ int btrfs_read_chunk_tree(struct btrfs_root *root)
if (!path)
return -ENOMEM;
+ mutex_lock(&uuid_mutex);
+ lock_chunks(root);
+
/* first we search for all of the device items, and then we
* read in all of the chunk items. This way we can create chunk
* mappings that reference all of the devices that are afound
@@ -3737,6 +3739,9 @@ again:
}
ret = 0;
error:
+ unlock_chunks(root);
+ mutex_unlock(&uuid_mutex);
+
btrfs_free_path(path);
return ret;
}