From nobody Sat Nov 15 19:39:03 2025 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 174861817171698.60759537262061; Fri, 30 May 2025 08:16:11 -0700 (PDT) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uL1PD-0003OU-49; Fri, 30 May 2025 11:12:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uL1P9-0003Ds-SY; Fri, 30 May 2025 11:12:19 -0400 Received: from proxmox-new.maurer-it.com ([94.136.29.106]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1uL1P7-0002HB-Jg; Fri, 30 May 2025 11:12:19 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 17E9C44A86; Fri, 30 May 2025 17:11:44 +0200 (CEST) From: Fiona Ebner To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, kwolf@redhat.com, den@virtuozzo.com, andrey.drobyshev@virtuozzo.com, hreitz@redhat.com, stefanha@redhat.com, eblake@redhat.com, jsnow@redhat.com, vsementsov@yandex-team.ru, xiechanglong.d@gmail.com, wencongyang2@huawei.com, berto@igalia.com, fam@euphon.net, ari@tuxera.com Subject: [PATCH v4 14/48] block: move drain outside of quorum_add_child() Date: Fri, 30 May 2025 17:10:51 +0200 Message-Id: <20250530151125.955508-15-f.ebner@proxmox.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250530151125.955508-1-f.ebner@proxmox.com> References: <20250530151125.955508-1-f.ebner@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=94.136.29.106; envelope-from=f.ebner@proxmox.com; helo=proxmox-new.maurer-it.com X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1748618173607116600 Content-Type: text/plain; charset="utf-8" This is part of resolving the deadlock mentioned in commit "block: move draining out of bdrv_change_aio_context() and mark GRAPH_RDLOCK". The quorum_add_child() callback runs under the graph lock, so it is not allowed to drain. It is only called as the .bdrv_add_child() callback, which is only called in the bdrv_add_child() function, which also runs under the graph lock. The bdrv_add_child() function is called by qmp_x_blockdev_change(), where a drained section is introduced. Signed-off-by: Fiona Ebner --- Changes in v4: * Document requirement that all nodes need to be drained for bdrv_add_child() wrapper and callback. * Split common comment for bdrv_add_child()/bdrv_del_child() to become one comment for each function. * Add comment for bdrv_add_child() callback. block.c | 10 ++++++++-- block/quorum.c | 2 -- blockdev.c | 2 ++ include/block/block_int-common.h | 7 +++++++ 4 files changed, 17 insertions(+), 4 deletions(-) diff --git a/block.c b/block.c index 6fc87aa318..f6c2f7e208 100644 --- a/block.c +++ b/block.c @@ -8220,8 +8220,10 @@ char *bdrv_dirname(BlockDriverState *bs, Error **err= p) } =20 /* - * Hot add/remove a BDS's child. So the user can take a child offline when - * it is broken and take a new child online + * Hot add a BDS's child. Used in combination with bdrv_del_child, so the = user + * can take a child offline when it is broken and take a new child online. + * + * All block nodes must be drained. */ void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_b= s, Error **errp) @@ -8261,6 +8263,10 @@ void bdrv_add_child(BlockDriverState *parent_bs, Blo= ckDriverState *child_bs, parent_bs->drv->bdrv_add_child(parent_bs, child_bs, errp); } =20 +/* + * Hot remove a BDS's child. Used in combination with bdrv_add_child, so t= he + * user can take a child offline when it is broken and take a new child on= line. + */ void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error *= *errp) { BdrvChild *tmp; diff --git a/block/quorum.c b/block/quorum.c index ea17b0ec13..ed8ce801ee 100644 --- a/block/quorum.c +++ b/block/quorum.c @@ -1096,10 +1096,8 @@ quorum_add_child(BlockDriverState *bs, BlockDriverSt= ate *child_bs, Error **errp) /* We can safely add the child now */ bdrv_ref(child_bs); =20 - bdrv_drain_all_begin(); child =3D bdrv_attach_child(bs, child_bs, indexstr, &child_of_bds, BDRV_CHILD_DATA, errp); - bdrv_drain_all_end(); if (child =3D=3D NULL) { s->next_child_index--; return; diff --git a/blockdev.c b/blockdev.c index 750beba41f..bd5ca77619 100644 --- a/blockdev.c +++ b/blockdev.c @@ -3531,6 +3531,7 @@ void qmp_x_blockdev_change(const char *parent, const = char *child, BlockDriverState *parent_bs, *new_bs =3D NULL; BdrvChild *p_child; =20 + bdrv_drain_all_begin(); bdrv_graph_wrlock(); =20 parent_bs =3D bdrv_lookup_bs(parent, parent, errp); @@ -3568,6 +3569,7 @@ void qmp_x_blockdev_change(const char *parent, const = char *child, =20 out: bdrv_graph_wrunlock(); + bdrv_drain_all_end(); } =20 BlockJobInfoList *qmp_query_block_jobs(Error **errp) diff --git a/include/block/block_int-common.h b/include/block/block_int-com= mon.h index 168f703fa1..f9e742f812 100644 --- a/include/block/block_int-common.h +++ b/include/block/block_int-common.h @@ -396,6 +396,13 @@ struct BlockDriver { int GRAPH_RDLOCK_PTR (*bdrv_probe_geometry)( BlockDriverState *bs, HDGeometry *geo); =20 + /** + * Hot add a BDS's child. Used in combination with bdrv_del_child, so = the + * user can take a child offline when it is broken and take a new child + * online. + * + * All block nodes must be drained. + */ void GRAPH_WRLOCK_PTR (*bdrv_add_child)( BlockDriverState *parent, BlockDriverState *child, Error **errp); =20 --=20 2.39.5