From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55643) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xsueh-0006Kw-EP for qemu-devel@nongnu.org; Mon, 24 Nov 2014 09:30:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Xsueb-0000N0-D1 for qemu-devel@nongnu.org; Mon, 24 Nov 2014 09:30:19 -0500 Received: from mail-pa0-f42.google.com ([209.85.220.42]:58783) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Xsueb-0000Mn-8I for qemu-devel@nongnu.org; Mon, 24 Nov 2014 09:30:13 -0500 Received: by mail-pa0-f42.google.com with SMTP id et14so9592340pad.15 for ; Mon, 24 Nov 2014 06:30:12 -0800 (PST) From: Ming Lei Date: Mon, 24 Nov 2014 22:29:38 +0800 Message-Id: <1416839379-19677-3-git-send-email-ming.lei@canonical.com> In-Reply-To: <1416839379-19677-1-git-send-email-ming.lei@canonical.com> References: <1416839379-19677-1-git-send-email-ming.lei@canonical.com> Subject: [Qemu-devel] [PATCH v5 2/3] linux-aio: handling -EAGAIN for !s->io_q.plugged case List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, Paolo Bonzini , Stefan Hajnoczi , Kevin Wolf Cc: Ming Lei Previously -EAGAIN is simply ignored for !s->io_q.plugged case, and sometimes it is easy to cause -EIO to VM, such as NVME device. This patch handles -EAGAIN by io queue for !s->io_q.plugged case, and it will be retried in following aio completion cb. Suggested-by: Paolo Bonzini Signed-off-by: Ming Lei --- block/linux-aio.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/block/linux-aio.c b/block/linux-aio.c index 70312a4..0cb098d 100644 --- a/block/linux-aio.c +++ b/block/linux-aio.c @@ -282,12 +282,17 @@ static int ioq_enqueue(struct qemu_laio_state *s, struct iocb *iocb) s->io_q.iocbs[idx++] = iocb; s->io_q.idx = idx; - /* submit immediately if queue depth is above 2/3 */ - if (idx > s->io_q.size * 2 / 3) { - return ioq_submit(s); + /* + * This is reached in two cases: queue not plugged but io_submit + * returned -EAGAIN, or queue plugged. In the latter case, start + * submitting some I/O if the queue is getting too full. In the + * former case, instead, wait until an I/O operation is completed. + */ + if (!s->io_q.plugged || likely(idx < s->io_q.size * 2 / 3)) { + return 0; } - return 0; + return ioq_submit(s); } void laio_io_plug(BlockDriverState *bs, void *aio_ctx) @@ -348,15 +353,18 @@ BlockAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd, } io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e)); - if (!s->io_q.plugged) { - if (io_submit(s->ctx, 1, &iocbs) < 0) { - goto out_free_aiocb; - } - } else { - if (ioq_enqueue(s, iocbs) < 0) { + /* Switch to queue mode until -EAGAIN is handled */ + if (!s->io_q.plugged && !s->io_q.idx) { + int ret = io_submit(s->ctx, 1, &iocbs); + if (ret >= 0) { + return &laiocb->common; + } else if (ret != -EAGAIN) { goto out_free_aiocb; } } + if (ioq_enqueue(s, iocbs) < 0) { + goto out_free_aiocb; + } return &laiocb->common; out_free_aiocb: -- 1.7.9.5