From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59612) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1adGPT-0008UU-Q1 for qemu-devel@nongnu.org; Tue, 08 Mar 2016 07:06:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1adGPO-0003t6-NT for qemu-devel@nongnu.org; Tue, 08 Mar 2016 07:06:43 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42210) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1adGPO-0003sY-IZ for qemu-devel@nongnu.org; Tue, 08 Mar 2016 07:06:38 -0500 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 46480804E2 for ; Tue, 8 Mar 2016 12:06:38 +0000 (UTC) References: <1457431876-8475-1-git-send-email-stefanha@redhat.com> From: Paolo Bonzini Message-ID: <56DEC04A.1060501@redhat.com> Date: Tue, 8 Mar 2016 13:06:34 +0100 MIME-Version: 1.0 In-Reply-To: <1457431876-8475-1-git-send-email-stefanha@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] Revert "qed: Implement .bdrv_drain" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , qemu-devel@nongnu.org Cc: Kevin Wolf , Fam Zheng On 08/03/2016 11:11, Stefan Hajnoczi wrote: > This reverts commit df9a681dc9ad41c9cdeb9ecc5d060ba9abd27e01. > > Note that commit df9a681dc9ad41c9cdeb9ecc5d060ba9abd27e01 included some > unrelated hunks, possibly due to a merge failure or an overlooked > squash. This only reverts the qed .bdrv_drain() implementation. > > The qed .bdrv_drain() implementation is unsafe and can lead to a double > request completion. > > Paolo Bonzini reports: > "The problem is that bdrv_qed_drain calls qed_plug_allocating_write_reqs > unconditionally, but this is not correct if an allocating write is > queued. In this case, qed_unplug_allocating_write_reqs will restart the > allocating write and possibly cause it to complete. The aiocb however > is still in use for the L2/L1 table writes, and will then be completed > again as soon as the table writes are stable." > > For QEMU 2.6 we can simply revert this commit. A full solution for the > qed need check timer may be added if the bdrv_drain() implementation is > extended. > > Reported-by: Paolo Bonzini > Signed-off-by: Stefan Hajnoczi Acked-by: Paolo Bonzini Paolo > --- > block/qed.c | 13 ------------- > 1 file changed, 13 deletions(-) > > Passes ./check -qed. > > diff --git a/block/qed.c b/block/qed.c > index 404be1e..3da8021 100644 > --- a/block/qed.c > +++ b/block/qed.c > @@ -376,18 +376,6 @@ static void bdrv_qed_attach_aio_context(BlockDriverState *bs, > } > } > > -static void bdrv_qed_drain(BlockDriverState *bs) > -{ > - BDRVQEDState *s = bs->opaque; > - > - /* Cancel timer and start doing I/O that were meant to happen as if it > - * fired, that way we get bdrv_drain() taking care of the ongoing requests > - * correctly. */ > - qed_cancel_need_check_timer(s); > - qed_plug_allocating_write_reqs(s); > - bdrv_aio_flush(s->bs, qed_clear_need_check, s); > -} > - > static int bdrv_qed_open(BlockDriverState *bs, QDict *options, int flags, > Error **errp) > { > @@ -1692,7 +1680,6 @@ 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) >