From: Stefan Hajnoczi <stefanha@gmail.com>
To: Ming Lei <ming.lei@canonical.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Peter Maydell <peter.maydell@linaro.org>,
Fam Zheng <famz@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
qemu-devel@nongnu.org, Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch
Date: Thu, 3 Jul 2014 14:35:17 +0200 [thread overview]
Message-ID: <20140703123517.GC28032@stefanha-thinkpad.redhat.com> (raw)
In-Reply-To: <1404303528-7115-4-git-send-email-ming.lei@canonical.com>
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On Wed, Jul 02, 2014 at 08:18:48PM +0800, Ming Lei wrote:
> diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
> index c10b7b7..82bb276 100644
> --- a/hw/block/dataplane/virtio-blk.c
> +++ b/hw/block/dataplane/virtio-blk.c
> @@ -201,6 +201,9 @@ static void do_flush_cmd(VirtIOBlockDataPlane *s, VirtQueueElement *elem,
> req->elem = elem;
> req->inhdr = inhdr;
>
> + /* flush IOs queued first */
> + bdrv_flush_io_queue(s->blk->conf.bs);
> +
> bdrv_aio_flush(s->blk->conf.bs, complete_flush, req);
> }
>
I looked back at previous email threads but I don't understand why this
is necessary.
bdrv_aio_flush() commits the disk write cache, that means _already
completed_ writes will be on stable storage. However, it does not make
any guarantees about in-flight writes. So this seems like a pointless
call that can be dropped safely.
Stefan
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next prev parent reply other threads:[~2014-07-03 12:35 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 12:18 [Qemu-devel] [PATCH v4 0/3] linux-aio: introduce submit I/O as a batch Ming Lei
2014-07-02 12:18 ` [Qemu-devel] [PATCH v4 1/3] block: block: introduce APIs for submitting IO as Ming Lei
2014-07-02 12:46 ` Eric Blake
2014-07-03 9:40 ` Kevin Wolf
2014-07-02 12:18 ` [Qemu-devel] [PATCH v4 2/3] linux-aio: implement io plug, unplug and flush io queue Ming Lei
2014-07-03 9:40 ` Kevin Wolf
2014-07-03 9:51 ` Ming Lei
2014-07-03 10:04 ` Paolo Bonzini
2014-07-03 10:45 ` Ming Lei
2014-07-03 10:50 ` Paolo Bonzini
2014-07-03 11:31 ` Ming Lei
2014-07-03 10:22 ` Kevin Wolf
2014-07-03 10:24 ` Ming Lei
2014-07-03 10:30 ` Kevin Wolf
2014-07-03 12:24 ` Stefan Hajnoczi
2014-07-04 9:18 ` Ming Lei
2014-07-04 9:21 ` Ming Lei
2014-07-02 12:18 ` [Qemu-devel] [PATCH v4 3/3] dataplane: submit I/O as a batch Ming Lei
2014-07-03 9:44 ` Kevin Wolf
2014-07-03 9:49 ` Paolo Bonzini
2014-07-03 10:18 ` Kevin Wolf
2014-07-03 12:35 ` Stefan Hajnoczi [this message]
2014-07-03 12:37 ` Stefan Hajnoczi
2014-07-03 12:47 ` Ming Lei
2014-07-03 9:25 ` [Qemu-devel] [PATCH v4 0/3] linux-aio: introduce " Kevin Wolf
2014-07-03 12:36 ` Stefan Hajnoczi
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