From patchwork Mon Jul 9 01:15:52 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fam Zheng X-Patchwork-Id: 10513419 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 7A0E860318 for ; Mon, 9 Jul 2018 01:16:49 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 50E5B2852C for ; Mon, 9 Jul 2018 01:16:49 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 2D245285A8; Mon, 9 Jul 2018 01:16:49 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 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.wl.linuxfoundation.org (Postfix) with ESMTPS id 3F1B82852C for ; Mon, 9 Jul 2018 01:16:47 +0000 (UTC) Received: from localhost ([::1]:38771 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fcKnF-00021b-0R for patchwork-qemu-devel@patchwork.kernel.org; Sun, 08 Jul 2018 21:16:45 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:44990) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fcKma-0001fG-1q for qemu-devel@nongnu.org; Sun, 08 Jul 2018 21:16:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fcKmY-0005P3-Ju for qemu-devel@nongnu.org; Sun, 08 Jul 2018 21:16:04 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58292 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fcKmT-0005Mk-JF; Sun, 08 Jul 2018 21:15:57 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2B384402346D; Mon, 9 Jul 2018 01:15:56 +0000 (UTC) Received: from localhost (ovpn-12-16.pek2.redhat.com [10.72.12.16]) by smtp.corp.redhat.com (Postfix) with ESMTP id E2CEE2026D65; Mon, 9 Jul 2018 01:15:54 +0000 (UTC) Date: Mon, 9 Jul 2018 09:15:52 +0800 From: Fam Zheng To: Vladimir Sementsov-Ogievskiy Message-ID: <20180709011552.GA14487@lemon.usersys.redhat.com> References: <20180706183051.197403-1-vsementsov@virtuozzo.com> <20180706183051.197403-2-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20180706183051.197403-2-vsementsov@virtuozzo.com> User-Agent: Mutt/1.10.0 (2018-05-17) X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 09 Jul 2018 01:15:56 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 09 Jul 2018 01:15:56 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'famz@redhat.com' RCPT:'' X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 66.187.233.73 Subject: Re: [Qemu-devel] [PATCH v4 1/4] block/io: fix copy_range X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, qemu-block@nongnu.org, jcody@redhat.com, pl@kamp.de, qemu-devel@nongnu.org, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, pbonzini@redhat.com, jsnow@redhat.com Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: "Qemu-devel" X-Virus-Scanned: ClamAV using ClamSMTP On Fri, 07/06 21:30, Vladimir Sementsov-Ogievskiy wrote: > Here two things are fixed: > > 1. Architecture > > On each recursion step, we go to the child of src or dst, only for one > of them. So, it's wrong to create tracked requests for both on each > step. It leads to tracked requests duplication. > > 2. Wait for serializing requests on write path independently of > BDRV_REQ_NO_SERIALISING > > Before commit 9ded4a01149 "backup: Use copy offloading", > BDRV_REQ_NO_SERIALISING was used for only one case: read in > copy-on-write operation during backup. Also, the flag was handled only > on read path (in bdrv_co_preadv and bdrv_aligned_preadv). > > After 9ded4a01149, flag is used for not waiting serializing operations > on backup target (in same case of copy-on-write operation). This > behavior change is unsubstantiated and potentially dangerous, let's > drop it and add additional asserts and documentation. > > Signed-off-by: Vladimir Sementsov-Ogievskiy > --- > include/block/block.h | 13 +++++++ > block/io.c | 103 +++++++++++++++++++++++++++++++------------------- > 2 files changed, 78 insertions(+), 38 deletions(-) > > diff --git a/include/block/block.h b/include/block/block.h > index e5c7759a0c..a06a4d27de 100644 > --- a/include/block/block.h > +++ b/include/block/block.h > @@ -50,6 +50,19 @@ typedef enum { > * opened with BDRV_O_UNMAP. > */ > BDRV_REQ_MAY_UNMAP = 0x4, > + > + /* The BDRV_REQ_NO_SERIALISING means that we don't want to > + * wait_serialising_requests(), when reading. > + * > + * This flag is used for backup copy on write operation, when we need to > + * read old data before write (write notifier triggered). It is ok, due to > + * we already waited for serializing requests in initiative write (see > + * bdrv_aligned_pwritev), and it is necessary for the case when initiative > + * write is serializing itself (we'll dead lock waiting it). > + * > + * The described case is the only usage for the flag for now, so, it is > + * supported only for read operation and restricted for write. > + */ > BDRV_REQ_NO_SERIALISING = 0x8, > BDRV_REQ_FUA = 0x10, > BDRV_REQ_WRITE_COMPRESSED = 0x20, > diff --git a/block/io.c b/block/io.c > index 1a2272fad3..621b21c455 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -1572,6 +1572,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChild *child, > max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX), > align); > > + /* BDRV_REQ_NO_SERIALISING is only for read operation */ > + assert(!(flags & BDRV_REQ_NO_SERIALISING)); > waited = wait_serialising_requests(req); > assert(!waited || !req->serialising); > assert(req->overlap_offset <= offset); > @@ -2888,15 +2890,19 @@ void bdrv_unregister_buf(BlockDriverState *bs, void *host) > } > } > > -static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src, > - uint64_t src_offset, > - BdrvChild *dst, > - uint64_t dst_offset, > - uint64_t bytes, > - BdrvRequestFlags flags, > - bool recurse_src) > +/* Common part of bdrv_co_copy_range_from and bdrv_co_copy_range_to. > + * > + * Return -errno on failure, > + * 0 if successfully handled by bdrv_co_pwrite_zeroes > + * 1 to continue copy_range operation > + */ > +static int coroutine_fn bdrv_co_copy_range_check(BdrvChild *src, > + uint64_t src_offset, > + BdrvChild *dst, > + uint64_t dst_offset, > + uint64_t bytes, > + BdrvRequestFlags flags) > { > - BdrvTrackedRequest src_req, dst_req; > int ret; > > if (!dst || !dst->bs) { > @@ -2923,33 +2929,8 @@ static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src, > || src->bs->encrypted || dst->bs->encrypted) { > return -ENOTSUP; > } > - bdrv_inc_in_flight(src->bs); > - bdrv_inc_in_flight(dst->bs); > - tracked_request_begin(&src_req, src->bs, src_offset, > - bytes, BDRV_TRACKED_READ); > - tracked_request_begin(&dst_req, dst->bs, dst_offset, > - bytes, BDRV_TRACKED_WRITE); > > - if (!(flags & BDRV_REQ_NO_SERIALISING)) { > - wait_serialising_requests(&src_req); > - wait_serialising_requests(&dst_req); > - } > - if (recurse_src) { > - ret = src->bs->drv->bdrv_co_copy_range_from(src->bs, > - src, src_offset, > - dst, dst_offset, > - bytes, flags); > - } else { > - ret = dst->bs->drv->bdrv_co_copy_range_to(dst->bs, > - src, src_offset, > - dst, dst_offset, > - bytes, flags); > - } > - tracked_request_end(&src_req); > - tracked_request_end(&dst_req); > - bdrv_dec_in_flight(src->bs); > - bdrv_dec_in_flight(dst->bs); > - return ret; > + return 1; > } > > /* Copy range from @src to @dst. > @@ -2960,8 +2941,31 @@ int coroutine_fn bdrv_co_copy_range_from(BdrvChild *src, uint64_t src_offset, > BdrvChild *dst, uint64_t dst_offset, > uint64_t bytes, BdrvRequestFlags flags) > { > - return bdrv_co_copy_range_internal(src, src_offset, dst, dst_offset, > - bytes, flags, true); > + BdrvTrackedRequest req; > + int ret; > + > + ret = bdrv_co_copy_range_check(src, src_offset, dst, dst_offset, bytes, > + flags); I don't like a function called _check to already do I/O here. Instead, I think this is cleaner: diff --git a/block/io.c b/block/io.c index 1a2272fad3..694a94dfae 100644 --- a/block/io.c +++ b/block/io.c @@ -2923,32 +2923,34 @@ static int coroutine_fn bdrv_co_copy_range_internal(BdrvChild *src, || src->bs->encrypted || dst->bs->encrypted) { return -ENOTSUP; } - bdrv_inc_in_flight(src->bs); - bdrv_inc_in_flight(dst->bs); - tracked_request_begin(&src_req, src->bs, src_offset, - bytes, BDRV_TRACKED_READ); - tracked_request_begin(&dst_req, dst->bs, dst_offset, - bytes, BDRV_TRACKED_WRITE); - if (!(flags & BDRV_REQ_NO_SERIALISING)) { - wait_serialising_requests(&src_req); - wait_serialising_requests(&dst_req); - } if (recurse_src) { + bdrv_inc_in_flight(src->bs); + tracked_request_begin(&src_req, src->bs, src_offset, + bytes, BDRV_TRACKED_READ); + if (!(flags & BDRV_REQ_NO_SERIALISING)) { + wait_serialising_requests(&src_req); + } ret = src->bs->drv->bdrv_co_copy_range_from(src->bs, src, src_offset, dst, dst_offset, bytes, flags); + tracked_request_end(&src_req); + bdrv_dec_in_flight(src->bs); } else { + bdrv_inc_in_flight(dst->bs); + tracked_request_begin(&dst_req, dst->bs, dst_offset, + bytes, BDRV_TRACKED_WRITE); + /* BDRV_REQ_NO_SERIALISING is only for read operation, so we ignore it + * in flags. */ + wait_serialising_requests(&dst_req); ret = dst->bs->drv->bdrv_co_copy_range_to(dst->bs, src, src_offset, dst, dst_offset, bytes, flags); + tracked_request_end(&dst_req); + bdrv_dec_in_flight(dst->bs); } - tracked_request_end(&src_req); - tracked_request_end(&dst_req); - bdrv_dec_in_flight(src->bs); - bdrv_dec_in_flight(dst->bs); return ret; }