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dkim=none (message not signed) header.d=none;redhat.com; dmarc=none action=none header.from=virtuozzo.com; Received: from AM7PR08MB5494.eurprd08.prod.outlook.com (2603:10a6:20b:dc::15) by AM5PR0801MB1907.eurprd08.prod.outlook.com (2603:10a6:203:4a::11) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4108.25; Thu, 6 May 2021 09:21:45 +0000 Received: from AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133]) by AM7PR08MB5494.eurprd08.prod.outlook.com ([fe80::b403:c1a9:6bb7:133%7]) with mapi id 15.20.4108.026; Thu, 6 May 2021 09:21:45 +0000 Subject: Re: [PATCH v4 4/6] block: Support multiple reopening with x-blockdev-reopen To: Kevin Wolf Cc: Alberto Garcia , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz References: From: Vladimir Sementsov-Ogievskiy Message-ID: Date: Thu, 6 May 2021 12:21:42 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 In-Reply-To: Content-Type: text/plain; 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envelope-from=vsementsov@virtuozzo.com; helo=EUR04-VI1-obe.outbound.protection.outlook.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, MSGID_FROM_MTA_HEADER=0.001, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 05.05.2021 19:18, Kevin Wolf wrote: >> And then, bdrv_reopen_multiple() is called with no aio context >> acquired, and no drained section.. And it shoud be refactored to >> properly operate with acquiring and realeasing the contexts and >> drained sections when needed... > The drained section shouldn't be a problem, we can keep this. In fact, > we need this, it is a documented requirement of bdrv_reopen_multiple(). > We just need to drop the AioContext lock after drained_begin. > > bdrv_reopen_multiple() should really document its requirements regarding > AioContext locks. It probably doesn't really care, but requires that > it be called from the main thread. > >> (note preexisting problem of reopen, that during reopen the whole tree >> may be moved to another aio context, but we continue operations with >> acquired old aio context which is wrong). > Do we even acquire the old AioContext? > I think, I mean aio_context_acquire(ctx); in current qmp_x_blockdev_reopen().. And I remember, that you said about that problem. Still, may be I misunderstood (or misremember). Doesn't worth digging, I'd prefer just review v5 with a fresh eye when it comes. -- Best regards, Vladimir