On Tue, Jul 02, 2013 at 11:38:33AM +0200, Kevin Wolf wrote:
> Am 01.07.2013 um 13:29 hat Stefan Hajnoczi geschrieben:
> > Since 80ccf93b we flush the block device during close. The
> > bdrv_drain_all() call should come before bdrv_flush() to ensure guest
> > write requests have completed. Otherwise we may miss pending writes
> > when flushing.
> >
> > However, there is still a slight change that cancelling a blockjob or
> > doing bdrv_flush() might leave an I/O request running, so call
> > bdrv_drain_all() again for safety as the final step.
> >
> > Cc: qemu-sta...@nongnu.org
> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
> > ---
> > block.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/block.c b/block.c
> > index 6c493ad..fca55b1 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -1358,11 +1358,12 @@ void bdrv_reopen_abort(BDRVReopenState
> > *reopen_state)
> >
> > void bdrv_close(BlockDriverState *bs)
> > {
> > - bdrv_flush(bs);
> > + bdrv_drain_all(); /* complete guest I/O */
> > if (bs->job) {
> > block_job_cancel_sync(bs->job);
> > }
> > - bdrv_drain_all();
> > + bdrv_flush(bs);
> > + bdrv_drain_all(); /* in case blockjob or flush started I/O */
> > notifier_list_notify(&bs->close_notifiers, bs);
>
> I think we need the bdrv_drain_all() immediately before calling
> bdrv_flush(), so that block job writes are flushed as well. You can
> probably move the first one there, there doesn't seem to be a reason to
> drain guest requests and block job requests separately.
Good idea, will fix in v2.
Stefan
