From 10f6327b5d26660e06120ba17cff993cb616b1d2 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 17 Nov 2011 15:05:22 -0500 Subject: [PATCH] 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 --- fs/btrfs/volumes.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index f4b839fd3c9d..96bb3c0a79b0 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -706,8 +706,6 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, u64 devid; u64 transid; - mutex_lock(&uuid_mutex); - flags |= FMODE_EXCL; bdev = blkdev_get_by_path(path, flags, holder); @@ -716,6 +714,7 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, goto error; } + mutex_lock(&uuid_mutex); ret = set_blocksize(bdev, 4096); if (ret) goto error_close; @@ -737,9 +736,9 @@ int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder, brelse(bh); error_close: + mutex_unlock(&uuid_mutex); blkdev_put(bdev, flags); error: - mutex_unlock(&uuid_mutex); return ret; }