btrfs: fix a deadlock in btrfs_scan_one_device()
pathname resolution under a global mutex, taken on some paths in ->mount()
is a Bad Idea(tm) - think what happens if said pathname resolution triggers
automount of some btrfs instance and walks into attempt to grab the same
mutex. Deadlock - we are waiting for daemon to finish walking the path,
daemon is waiting for us to release the mutex...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index f4b839f..96bb3c0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -706,8 +706,6 @@
u64 devid;
u64 transid;
- mutex_lock(&uuid_mutex);
-
flags |= FMODE_EXCL;
bdev = blkdev_get_by_path(path, flags, holder);
@@ -716,6 +714,7 @@
goto error;
}
+ mutex_lock(&uuid_mutex);
ret = set_blocksize(bdev, 4096);
if (ret)
goto error_close;
@@ -737,9 +736,9 @@
brelse(bh);
error_close:
+ mutex_unlock(&uuid_mutex);
blkdev_put(bdev, flags);
error:
- mutex_unlock(&uuid_mutex);
return ret;
}