From nobody Tue Nov 4 21:44:00 2025 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 153072673911067.497117101335; Wed, 4 Jul 2018 10:52:19 -0700 (PDT) Received: from localhost ([::1]:48469 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1falwk-0001ZG-Vt for importer@patchew.org; Wed, 04 Jul 2018 13:52:07 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33082) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1faluw-0000Un-Il for qemu-devel@nongnu.org; Wed, 04 Jul 2018 13:50:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1falut-0006Yy-57 for qemu-devel@nongnu.org; Wed, 04 Jul 2018 13:50:14 -0400 Received: from relay.sw.ru ([185.231.240.75]:48370) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1falus-0006Te-T9; Wed, 04 Jul 2018 13:50:11 -0400 Received: from vz-out.virtuozzo.com ([185.231.240.5] helo=kvm.sw.ru) by relay.sw.ru with esmtp (Exim 4.90_1) (envelope-from ) id 1falup-0004FF-3R; Wed, 04 Jul 2018 20:50:07 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-devel@nongnu.org, qemu-block@nongnu.org Date: Wed, 4 Jul 2018 20:50:03 +0300 Message-Id: <20180704175006.519184-2-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.11.1 In-Reply-To: <20180704175006.519184-1-vsementsov@virtuozzo.com> References: <20180704175006.519184-1-vsementsov@virtuozzo.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 185.231.240.75 Subject: [Qemu-devel] [PATCH v2 1/4] block: disallow BDRV_REQ_NO_SERIALISING for write 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, vsementsov@virtuozzo.com, famz@redhat.com, ronniesahlberg@gmail.com, jcody@redhat.com, pl@kamp.de, mreitz@redhat.com, stefanha@redhat.com, den@openvz.org, pbonzini@redhat.com, jsnow@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 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. Signed-off-by: Vladimir Sementsov-Ogievskiy --- include/block/block.h | 13 +++++++++++++ block/io.c | 7 ++++++- 2 files changed, 19 insertions(+), 1 deletion(-) 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 =3D 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, du= e to + * we already waited for serializing requests in initiative write (see + * bdrv_aligned_pwritev), and it is necessary for the case when initia= tive + * 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 =3D 0x8, BDRV_REQ_FUA =3D 0x10, BDRV_REQ_WRITE_COMPRESSED =3D 0x20, diff --git a/block/io.c b/block/io.c index 1a2272fad3..51bef9fc50 100644 --- a/block/io.c +++ b/block/io.c @@ -1572,6 +1572,8 @@ static int coroutine_fn bdrv_aligned_pwritev(BdrvChil= d *child, max_transfer =3D QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT= _MAX), align); =20 + /* BDRV_REQ_NO_SERIALISING is only for read operation */ + assert(!(flags & BDRV_REQ_NO_SERIALISING)); waited =3D wait_serialising_requests(req); assert(!waited || !req->serialising); assert(req->overlap_offset <=3D offset); @@ -2931,9 +2933,12 @@ static int coroutine_fn bdrv_co_copy_range_internal(= BdrvChild *src, bytes, BDRV_TRACKED_WRITE); =20 if (!(flags & BDRV_REQ_NO_SERIALISING)) { + /* BDRV_REQ_NO_SERIALISING is only for read */ wait_serialising_requests(&src_req); - wait_serialising_requests(&dst_req); } + + wait_serialising_requests(&dst_req); + if (recurse_src) { ret =3D src->bs->drv->bdrv_co_copy_range_from(src->bs, src, src_offset, --=20 2.11.1