Yeah I think this is ok, I’ll throw it on my queue for fixes for this cycle. Thanks, Josef On 3/20/17, 6:58 PM, "Ming Lin" <mlin@xxxxxxxxxx> wrote: From: Ratna Manoj Bolla <manoj.br@xxxxxxxxx> When a filesystem is mounted on a nbd device and on a disconnect, because of kill_bdev(), and resetting bdev size to zero, buffer_head mappings are getting destroyed under mounted filesystem. After a bdev size reset(i.e bdev->bd_inode->i_size = 0) on a disconnect, followed by a sys_umount(), generic_shutdown_super()->... ->__sync_blockdev()->... -blkdev_writepages()->... ->do_invalidatepage()->... -discard_buffer() is discarding superblock buffer_head assumed to be in mapped state by ext4_commit_super(). [mlin: ported to 4.11-rc2] Signed-off-by: Ratna Manoj Bolla <manoj.br@xxxxxxxxx --- drivers/block/nbd.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index cb4ccfc..a6a3643 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -125,7 +125,8 @@ static const char *nbdcmd_to_ascii(int cmd) static int nbd_size_clear(struct nbd_device *nbd, struct block_device *bdev) { - bd_set_size(bdev, 0); + if (bdev->bd_openers <= 1) + bd_set_size(bdev, 0); set_capacity(nbd->disk, 0); kobject_uevent(&nbd_to_dev(nbd)->kobj, KOBJ_CHANGE); @@ -603,6 +604,8 @@ static void nbd_reset(struct nbd_device *nbd) static void nbd_bdev_reset(struct block_device *bdev) { + if (bdev->bd_openers > 1) + return; set_device_ro(bdev, false); bdev->bd_inode->i_size = 0; if (max_part > 0) { @@ -666,7 +669,8 @@ static int nbd_clear_sock(struct nbd_device *nbd, struct block_device *bdev) { sock_shutdown(nbd); nbd_clear_que(nbd); - kill_bdev(bdev); + + __invalidate_device(bdev, true); nbd_bdev_reset(bdev); /* * We want to give the run thread a chance to wait for everybody -- 1.8.3.1