From patchwork Wed Mar 16 14:16:48 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 8600971 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id C070B9F6E1 for ; Wed, 16 Mar 2016 14:17:37 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 214E6202F2 for ; Wed, 16 Mar 2016 14:17:37 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 5AC08202AE for ; Wed, 16 Mar 2016 14:17:36 +0000 (UTC) Received: from localhost ([::1]:56593 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agCGV-00036X-Kf for patchwork-qemu-devel@patchwork.kernel.org; Wed, 16 Mar 2016 10:17:35 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42089) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agCGD-00032O-96 for qemu-devel@nongnu.org; Wed, 16 Mar 2016 10:17:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1agCG9-00060I-8k for qemu-devel@nongnu.org; Wed, 16 Mar 2016 10:17:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58955) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1agCG9-0005zn-1A for qemu-devel@nongnu.org; Wed, 16 Mar 2016 10:17:13 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id BB6117F6A7 for ; Wed, 16 Mar 2016 14:17:12 +0000 (UTC) Received: from donizetti.redhat.com (ovpn-112-54.ams2.redhat.com [10.36.112.54]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u2GEGwc0001673; Wed, 16 Mar 2016 10:17:11 -0400 From: Paolo Bonzini To: qemu-devel@nongnu.org Date: Wed, 16 Mar 2016 15:16:48 +0100 Message-Id: <1458137817-15383-8-git-send-email-pbonzini@redhat.com> In-Reply-To: <1458137817-15383-1-git-send-email-pbonzini@redhat.com> References: <1458137817-15383-1-git-send-email-pbonzini@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: famz@redhat.com, stefanha@redhat.com Subject: [Qemu-devel] [PATCH v2 07/16] block: change drain to look only at one child at a time X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP bdrv_requests_pending is checking children to also wait until internal requests (such as metadata writes) have completed. However, checking children is in general overkill. Children requests can be of two kinds: - requests caused by an operation on bs, e.g. a bdrv_aio_write to bs causing a write to bs->file->bs. In this case, the parent's in_flight count will always be incremented by at least one for every request in the child. - asynchronous metadata writes or flushes. Such writes can be started even if bs's in_flight count is zero, but not after the .bdrv_drain callback has been invoked. This patch therefore changes bdrv_drain to finish I/O in the parent (after which the parent's in_flight will be locked to zero), call bdrv_drain (after which the parent will not generate I/O on the child anymore), and then wait for internal I/O in the children to complete. Signed-off-by: Paolo Bonzini Reviewed-by: Fam Zheng --- v1->v2: moved bdrv_drain callback after in_flight is 0 in the parent [from QED drain discussion] block/io.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-) diff --git a/block/io.c b/block/io.c index a9a23a6..db975ab 100644 --- a/block/io.c +++ b/block/io.c @@ -237,16 +237,25 @@ bool bdrv_requests_pending(BlockDriverState *bs) return false; } -static void bdrv_drain_recurse(BlockDriverState *bs) +static bool bdrv_drain_io_recurse(BlockDriverState *bs) { BdrvChild *child; + bool waited = false; + + while (atomic_read(&bs->in_flight) > 0) { + aio_poll(bdrv_get_aio_context(bs), true); + waited = true; + } if (bs->drv && bs->drv->bdrv_drain) { bs->drv->bdrv_drain(bs); } + QLIST_FOREACH(child, &bs->children, next) { - bdrv_drain_recurse(child->bs); + waited |= bdrv_drain_io_recurse(child->bs); } + + return waited; } /* @@ -264,11 +273,7 @@ void bdrv_drain(BlockDriverState *bs) { bdrv_no_throttling_begin(bs); bdrv_io_unplugged_begin(bs); - bdrv_drain_recurse(bs); - while (bdrv_requests_pending(bs)) { - /* Keep iterating */ - aio_poll(bdrv_get_aio_context(bs), true); - } + bdrv_drain_io_recurse(bs); bdrv_io_unplugged_end(bs); bdrv_no_throttling_end(bs); } @@ -295,7 +300,6 @@ void bdrv_drain_all(void) } bdrv_no_throttling_begin(bs); bdrv_io_unplugged_begin(bs); - bdrv_drain_recurse(bs); aio_context_release(aio_context); if (!g_slist_find(aio_ctxs, aio_context)) { @@ -319,10 +323,7 @@ void bdrv_drain_all(void) aio_context_acquire(aio_context); while ((bs = bdrv_next(bs))) { if (aio_context == bdrv_get_aio_context(bs)) { - if (bdrv_requests_pending(bs)) { - aio_poll(aio_context, true); - waited = true; - } + waited |= bdrv_drain_io_recurse(bs); } } aio_context_release(aio_context);