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c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1777309547; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=RNf7Qtsfx36oLLaeD/N/V5PatsHP0UT/LP0p18adqyc=; b=dyUA6vP5yOuy1t9xK/acm8c79iojvmzZQJeoKSuzR3r8x3t1B1l9Ws9wIFjUdtXzaE3LI1 CXmMVQ6aEYtyXSEi0aa+BF2bv+XboYLW8ByyBVOLuTMi9Hph9b712qVfW63L41zn0kJKgl TYkEEqL3EI2xqUTjTlOSYKHvMdMrJUo= X-MC-Unique: xeNFhFwbOXqFn5IM-6mYQQ-1 X-Mimecast-MFC-AGG-ID: xeNFhFwbOXqFn5IM-6mYQQ_1777309542 From: Kevin Wolf To: qemu-block@nongnu.org Cc: kwolf@redhat.com, hreitz@redhat.com, den@openvz.org, stefanha@redhat.com, qemu-stable@nongnu.org, qemu-devel@nongnu.org Subject: [PATCH 1/4] commit: Drain nodes across all of bdrv_commit() Date: Mon, 27 Apr 2026 19:05:17 +0200 Message-ID: <20260427170520.101242-2-kwolf@redhat.com> In-Reply-To: <20260427170520.101242-1-kwolf@redhat.com> References: <20260427170520.101242-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 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=lists1p.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-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: qemu development 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-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1777309593287154100 Content-Type: text/plain; charset="utf-8" The whole implementation of bdrv_commit() is only correct if no new writes come in while it's running: It has only a single loop checking the allocation status for each block and finally calls bdrv_make_empty() without checking if that throws away any new changes. We already have to drain while taking the graph write lock. Just extend the drained section to all of bdrv_commit() to make sure that we don't get any inconsistencies. Signed-off-by: Kevin Wolf --- block/commit.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/block/commit.c b/block/commit.c index 0d9e1a16d7a..c5e3ef03a21 100644 --- a/block/commit.c +++ b/block/commit.c @@ -518,6 +518,7 @@ int bdrv_commit(BlockDriverState *bs) if (!drv) return -ENOMEDIUM; =20 + bdrv_drain_all_begin(); bdrv_graph_rdlock_main_loop(); =20 backing_file_bs =3D bdrv_cow_bs(bs); @@ -549,6 +550,10 @@ int bdrv_commit(BlockDriverState *bs) BLK_PERM_ALL); backing =3D blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_AL= L); =20 + /* We drained all nodes, but still make requests through BlockBackends= */ + blk_set_disable_request_queuing(src, true); + blk_set_disable_request_queuing(backing, true); + ret =3D blk_insert_bs(src, bs, &local_err); if (ret < 0) { error_report_err(local_err); @@ -565,7 +570,7 @@ int bdrv_commit(BlockDriverState *bs) =20 bdrv_graph_rdunlock_main_loop(); =20 - bdrv_graph_wrlock_drained(); + bdrv_graph_wrlock(); bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort); bdrv_set_backing_hd(bs, commit_top_bs, &error_abort); bdrv_graph_wrunlock(); @@ -647,7 +652,7 @@ ro_cleanup: blk_unref(backing); =20 bdrv_graph_rdunlock_main_loop(); - bdrv_graph_wrlock_drained(); + bdrv_graph_wrlock(); if (bdrv_cow_bs(bs) !=3D backing_file_bs) { bdrv_set_backing_hd(bs, backing_file_bs, &error_abort); } @@ -663,6 +668,7 @@ ro_cleanup: =20 out: bdrv_graph_rdunlock_main_loop(); + bdrv_drain_all_end(); =20 return ret; } --=20 2.53.0