{"id":2229022,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2229022/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260427170520.101242-2-kwolf@redhat.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.1/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260427170520.101242-2-kwolf@redhat.com>","date":"2026-04-27T17:05:17","name":"[1/4] commit: Drain nodes across all of bdrv_commit()","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"dfeea151a4133a66301dfc0abf44f8578e9477f0","submitter":{"id":2714,"url":"http://patchwork.ozlabs.org/api/1.1/people/2714/?format=json","name":"Kevin Wolf","email":"kwolf@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260427170520.101242-2-kwolf@redhat.com/mbox/","series":[{"id":501688,"url":"http://patchwork.ozlabs.org/api/1.1/series/501688/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501688","date":"2026-04-27T17:05:16","name":"qcow2: Fix corruption on discard during write with COW","version":1,"mbox":"http://patchwork.ozlabs.org/series/501688/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2229022/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2229022/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 header.b=dyUA6vP5;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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Mon, 27 Apr 2026 13:05:48 -0400","from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com\n (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by\n relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3,\n cipher=TLS_AES_256_GCM_SHA384) id us-mta-339-xeNFhFwbOXqFn5IM-6mYQQ-1; Mon,\n 27 Apr 2026 13:05:43 -0400","from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com\n (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111])\n (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)\n key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest\n SHA256)\n (No client certificate requested)\n by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS\n id CF1251800609; Mon, 27 Apr 2026 17:05:41 +0000 (UTC)","from merkur.fritz.box (unknown [10.44.49.22])\n by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP\n id 951A5180047F; Mon, 27 Apr 2026 17:05:39 +0000 (UTC)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;\n s=mimecast20190719; t=1777309547;\n h=from:from:reply-to:subject:subject:date:date:message-id:message-id:\n to:to:cc:cc:mime-version:mime-version:\n content-transfer-encoding:content-transfer-encoding:\n in-reply-to:in-reply-to:references:references;\n bh=RNf7Qtsfx36oLLaeD/N/V5PatsHP0UT/LP0p18adqyc=;\n b=dyUA6vP5yOuy1t9xK/acm8c79iojvmzZQJeoKSuzR3r8x3t1B1l9Ws9wIFjUdtXzaE3LI1\n CXmMVQ6aEYtyXSEi0aa+BF2bv+XboYLW8ByyBVOLuTMi9Hph9b712qVfW63L41zn0kJKgl\n 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,\n 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":"8bit","X-Scanned-By":"MIMEDefang 3.4.1 on 10.30.177.111","Received-SPF":"pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com;\n 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,\n DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001,\n 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":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"The whole implementation of bdrv_commit() is only correct if no new\nwrites come in while it's running: It has only a single loop checking\nthe allocation status for each block and finally calls bdrv_make_empty()\nwithout checking if that throws away any new changes.\n\nWe already have to drain while taking the graph write lock. Just extend\nthe drained section to all of bdrv_commit() to make sure that we don't\nget any inconsistencies.\n\nSigned-off-by: Kevin Wolf \n---\n block/commit.c | 10 ++++++++--\n 1 file changed, 8 insertions(+), 2 deletions(-)","diff":"diff --git a/block/commit.c b/block/commit.c\nindex 0d9e1a16d7a..c5e3ef03a21 100644\n--- a/block/commit.c\n+++ b/block/commit.c\n@@ -518,6 +518,7 @@ int bdrv_commit(BlockDriverState *bs)\n if (!drv)\n return -ENOMEDIUM;\n \n+ bdrv_drain_all_begin();\n bdrv_graph_rdlock_main_loop();\n \n backing_file_bs = bdrv_cow_bs(bs);\n@@ -549,6 +550,10 @@ int bdrv_commit(BlockDriverState *bs)\n BLK_PERM_ALL);\n backing = blk_new(ctx, BLK_PERM_WRITE | BLK_PERM_RESIZE, BLK_PERM_ALL);\n \n+ /* We drained all nodes, but still make requests through BlockBackends */\n+ blk_set_disable_request_queuing(src, true);\n+ blk_set_disable_request_queuing(backing, true);\n+\n ret = blk_insert_bs(src, bs, &local_err);\n if (ret < 0) {\n error_report_err(local_err);\n@@ -565,7 +570,7 @@ int bdrv_commit(BlockDriverState *bs)\n \n bdrv_graph_rdunlock_main_loop();\n \n- bdrv_graph_wrlock_drained();\n+ bdrv_graph_wrlock();\n bdrv_set_backing_hd(commit_top_bs, backing_file_bs, &error_abort);\n bdrv_set_backing_hd(bs, commit_top_bs, &error_abort);\n bdrv_graph_wrunlock();\n@@ -647,7 +652,7 @@ ro_cleanup:\n blk_unref(backing);\n \n bdrv_graph_rdunlock_main_loop();\n- bdrv_graph_wrlock_drained();\n+ bdrv_graph_wrlock();\n if (bdrv_cow_bs(bs) != backing_file_bs) {\n bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);\n }\n@@ -663,6 +668,7 @@ ro_cleanup:\n \n out:\n bdrv_graph_rdunlock_main_loop();\n+ bdrv_drain_all_end();\n \n return ret;\n }\n","prefixes":["1/4"]}