Re: [PATCH] ext4: make concurrent DEFAULT shutdown waits killable

[diasyzhangqing@gmail.com]

On Tue 10-11-26 21:35:56, Jan Kara wrote:
> Err, no. This is really syzkaller self-inflicted damage we aren't going to
> work around. If anything you could make the wait on bd_fsfreeze_mutex
> in bdev_freeze() killable. That will actually be a sensible change and
> should address syzbot warning as well.

Thanks, that's indeed simpler.  All current callers of bdev_freeze()
(the generic FIFREEZE ioctl, ext4, ntfs, ntfs3, xfs) already propagate
the error, so only the wait itself needs to change:

---


#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
 block/bdev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/block/bdev.c b/block/bdev.c
index f20f91b3176e..e57be2320423 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -301,7 +301,9 @@ int bdev_freeze(struct block_device *bdev)
 {
 	int error = 0;
 
-	mutex_lock(&bdev->bd_fsfreeze_mutex);
+	error = mutex_lock_killable(&bdev->bd_fsfreeze_mutex);
+	if (error)
+		return error;
 
 	/* A device being removed from its filesystem refuses freezes. */
 	if (!atomic_inc_unless_negative(&bdev->bd_fsfreeze_count)) {
-- 
2.43.7