From fd1464105cb37a3b50a72c1d2902e97a71950af8 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 18 Oct 2023 17:29:24 +0200 Subject: fs: Avoid grabbing sb->s_umount under bdev->bd_holder_lock The implementation of bdev holder operations such as fs_bdev_mark_dead() and fs_bdev_sync() grab sb->s_umount semaphore under bdev->bd_holder_lock. This is problematic because it leads to disk->open_mutex -> sb->s_umount lock ordering which is counterintuitive (usually we grab higher level (e.g. filesystem) locks first and lower level (e.g. block layer) locks later) and indeed makes lockdep complain about possible locking cycles whenever we open a block device while holding sb->s_umount semaphore. Implement a function bdev_super_lock_shared() which safely transitions from holding bdev->bd_holder_lock to holding sb->s_umount on alive superblock without introducing the problematic lock dependency. We use this function fs_bdev_sync() and fs_bdev_mark_dead(). Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20231018152924.3858-1-jack@suse.cz Link: https://lore.kernel.org/r/20231017184823.1383356-1-hch@lst.de Reviewed-by: Christoph Hellwig Signed-off-by: Christian Brauner --- block/bdev.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'block/bdev.c') diff --git a/block/bdev.c b/block/bdev.c index 4628dcb1da8a..9838085102b3 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -1012,9 +1012,10 @@ void bdev_mark_dead(struct block_device *bdev, bool surprise) mutex_lock(&bdev->bd_holder_lock); if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead) bdev->bd_holder_ops->mark_dead(bdev, surprise); - else + else { + mutex_unlock(&bdev->bd_holder_lock); sync_blockdev(bdev); - mutex_unlock(&bdev->bd_holder_lock); + } invalidate_bdev(bdev); } -- cgit