bdev_mark_dead()'s @surprise == true means the device is already gone. The filesystem callback fs_bdev_mark_dead() honours this and skips sync_filesystem(), but the bare block device path (no ->mark_dead op) lost its !surprise guard when the holder ->mark_dead callback was wired up (see Fixes), and now calls sync_blockdev() unconditionally, which can hang forever waiting on writeback that can no longer complete. syzkaller hit this via nvme_reset_work()'s "I/O queues lost" path: nvme_mark_namespaces_dead() -> blk_mark_disk_dead() -> bdev_mark_dead(bdev, true) -> sync_blockdev() blocks in folio_wait_writeback(), wedging the reset worker and every task waiting on it. Skip the sync on surprise removal, matching fs_bdev_mark_dead(); invalidate_bdev() still runs. Orderly removal (surprise == false) is unchanged. Fixes: d8530de5a6e8 ("block: call into the file system for bdev_mark_dead") Found by FuzzNvme(Syzkaller with FEMU fuzzing framework). Acked-by: Sungwoo Kim Acked-by: Dave Tian Acked-by: Weidong Zhu Signed-off-by: Chao Shi --- block/bdev.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/block/bdev.c b/block/bdev.c index b8fbb9576110..7fc3f5ba22a3 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -1259,7 +1259,13 @@ void bdev_mark_dead(struct block_device *bdev, bool surprise) bdev->bd_holder_ops->mark_dead(bdev, surprise); else { mutex_unlock(&bdev->bd_holder_lock); - sync_blockdev(bdev); + /* + * On surprise removal the device is already gone; syncing is + * futile and can hang forever waiting on I/O that will never + * complete. Match fs_bdev_mark_dead(), which also skips it. + */ + if (!surprise) + sync_blockdev(bdev); } invalidate_bdev(bdev); -- 2.43.0