On Tue, Feb 12, 2013 at 11:06 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: > There are two problems with shutdown in the NBD driver. The first is > that receiving the NBD_DISCONNECT ioctl does not sync the filesystem; > this is useful because BLKFLSBUF is restricted to processes that have > CAP_SYS_ADMIN, and the NBD client may not possess it (fsync of the > block device does not sync the filesystem, either).
> The second is that once we clear the socket we have no guarantee that > later reads will come from the same backing storage. Thus the page cache > must be cleaned, lest reads that hit on the page cache will return stale > data from the previously-accessible disk. Paolo, Thanks for this. A problem indeed... Acked-by: paul.cleme...@steeleye.com > Cc: <sta...@vger.kernel.org> > Cc: <nbd-gene...@lists.sf.net> > Cc: Paul Clements <paul.cleme...@steeleye.com> > Cc: Andrew Morton <a...@linux-foundation.org> > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > drivers/block/nbd.c | 10 ++++++++++ > 1 files changed, 10 insertions(+), 0 deletions(-) > > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c > index 5603765..a9c5c7a 100644 > --- a/drivers/block/nbd.c > +++ b/drivers/block/nbd.c > @@ -608,12 +608,20 @@ static int __nbd_ioctl(struct block_device *bdev, > struct nbd_device *nbd, > struct request sreq; > > dev_info(disk_to_dev(nbd->disk), "NBD_DISCONNECT\n"); > + if (!nbd->sock) > + return -EINVAL; > > + mutex_unlock(&nbd->tx_lock); > + fsync_bdev(bdev); > + mutex_lock(&nbd->tx_lock); > blk_rq_init(NULL, &sreq); > sreq.cmd_type = REQ_TYPE_SPECIAL; > nbd_cmd(&sreq) = NBD_CMD_DISC; > + > + /* Check again after getting mutex back. */ > if (!nbd->sock) > return -EINVAL; > + > nbd_send_req(nbd, &sreq); > return 0; > } > @@ -627,6 +635,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct > nbd_device *nbd, > nbd_clear_que(nbd); > BUG_ON(!list_empty(&nbd->queue_head)); > BUG_ON(!list_empty(&nbd->waiting_queue)); > + kill_bdev(bdev); > if (file) > fput(file); > return 0; > @@ -719,6 +728,7 @@ static int __nbd_ioctl(struct block_device *bdev, struct > nbd_device *nbd, > nbd->file = NULL; > nbd_clear_que(nbd); > dev_warn(disk_to_dev(nbd->disk), "queue cleared\n"); > + kill_bdev(bdev); > queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, > nbd->disk->queue); > if (file) > fput(file); > -- > 1.7.1 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
