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    SubjectRe: [Nbd] [RFC PATCH 1/1] nbd: replace kill_bdev() with __invalidate_device()
    On Mon, Mar 20, 2017 at 3:58 PM, Ming Lin <mlin@kernel.org> wrote:
    > From: Ratna Manoj Bolla <manoj.br@gmail.com>
    >
    > 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@gmail.com
    > ---
    > 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

    Hi Josef,

    Any comments?

    Thanks,
    Ming

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