From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53302) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zp66E-0000Ya-SY for qemu-devel@nongnu.org; Wed, 21 Oct 2015 22:59:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zp66D-0005qL-Oo for qemu-devel@nongnu.org; Wed, 21 Oct 2015 22:59:30 -0400 Date: Thu, 22 Oct 2015 10:59:20 +0800 From: Fam Zheng Message-ID: <20151022025920.GE11063@ad.usersys.redhat.com> References: <1445393209-26545-1-git-send-email-famz@redhat.com> <1445393209-26545-12-git-send-email-famz@redhat.com> <20151022022035.GA3026@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151022022035.GA3026@localhost.localdomain> Subject: Re: [Qemu-devel] [Qemu-block] [PATCH v5 11/12] qed: Implement .bdrv_drain List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jeff Cody Cc: kwolf@redhat.com, pbonzini@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org, stefanha@redhat.com On Wed, 10/21 22:20, Jeff Cody wrote: > On Wed, Oct 21, 2015 at 10:06:48AM +0800, Fam Zheng wrote: > > The "need_check_timer" is used to clear the "NEED_CHECK" flag in the > > image header after a grace period once metadata update has finished. In > > compliance to the bdrv_drain semantics we should make sure it remains > > deleted once .bdrv_drain is called. > > > > Call the qed_need_check_timer_cb manually to update the header > > immediately. > > > > Signed-off-by: Fam Zheng > > --- > > block/qed.c | 7 +++++++ > > 1 file changed, 7 insertions(+) > > > > diff --git a/block/qed.c b/block/qed.c > > index 5ea05d4..e9dcb4d 100644 > > --- a/block/qed.c > > +++ b/block/qed.c > > @@ -375,6 +375,12 @@ static void bdrv_qed_attach_aio_context(BlockDriverState *bs, > > } > > } > > > > +static void bdrv_qed_drain(BlockDriverState *bs) > > +{ > > + qed_cancel_need_check_timer(bs->opaque); > > + qed_need_check_timer_cb(bs->opaque); > > +} > > + > > Uh oh. > > This causes a segfault sometimes, and other times an abort: > > > # ./qemu-img create -f qed test.qed 512M > Formatting 'test.qed', fmt=qed size=536870912 cluster_size=65536 > > # ./qemu-io -c "read 0 512M" test.qed > read 536870912/536870912 bytes at offset 0 > 512 MiB, 1 ops; 0.0556 sec (8.988 GiB/sec and 17.9759 ops/sec) > Segmentation fault (core dumped) > > > If I run the above qemu-io command with gdb, it will abort in > qed_plug_allocating_write_reqs(). > > I'd hazard a guess (I have not verified) that it is due to the > qed_header_write() call triggered by the aio flush callback function > qed_clear_need_check(). The aio flush is done inside the > qed_need_check_timer_cb() call. Good catch, I think it's because of the second bdrv_drain in bdrv_close(), when the first bdrv_aio_flush in qed_need_check_timer_cb hasn't finished. We need a different bdrv_qed_drain implementation here. Fam > > > > > static int bdrv_qed_open(BlockDriverState *bs, QDict *options, int flags, > > Error **errp) > > { > > @@ -1676,6 +1682,7 @@ static BlockDriver bdrv_qed = { > > .bdrv_check = bdrv_qed_check, > > .bdrv_detach_aio_context = bdrv_qed_detach_aio_context, > > .bdrv_attach_aio_context = bdrv_qed_attach_aio_context, > > + .bdrv_drain = bdrv_qed_drain, > > }; > > > > static void bdrv_qed_init(void) > > -- > > 2.4.3 > > > >