From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E8051C4332F for ; Fri, 11 Nov 2022 16:55:23 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1otXIf-0007GC-LS; Fri, 11 Nov 2022 11:54:41 -0500 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 1otXIb-0007Fg-Lm for qemu-devel@nongnu.org; Fri, 11 Nov 2022 11:54:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1otXIa-0008Fl-3e for qemu-devel@nongnu.org; Fri, 11 Nov 2022 11:54:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1668185673; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=BgSMyecpdjcve5jvMTZmGBHWDho5+PadRDOxdWJTFbM=; b=B1t5LkvjdiqDLGB5ug7ONjU59j5rY3p5qGdqC0zMI9+xBJh1KMdqyY011UqFg2kdd/6dW5 fWXcrCyh/qTp9ssW8PvPTBtxRFUBbMY8HTllImR9mKPkmqvfg6IB+lzaOYw1laUC2ZlsGP Qxr2V/XZQBcSLF7h26G0Kq5uQFyyxFU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-503-jXvj7D6IPvaO137EDikeWg-1; Fri, 11 Nov 2022 11:54:30 -0500 X-MC-Unique: jXvj7D6IPvaO137EDikeWg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BA9FC101A54E; Fri, 11 Nov 2022 16:54:29 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.152]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9E5101415127; Fri, 11 Nov 2022 16:54:28 +0000 (UTC) Date: Fri, 11 Nov 2022 17:54:24 +0100 From: Kevin Wolf To: Vladimir Sementsov-Ogievskiy Cc: qemu-block@nongnu.org, eesposit@redhat.com, stefanha@redhat.com, hreitz@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH 06/13] block: Drain invidual nodes during reopen Message-ID: References: <20221108123738.530873-1-kwolf@redhat.com> <20221108123738.530873-7-kwolf@redhat.com> <18167aa9-e9e6-ea2c-ad96-68a7c972a371@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <18167aa9-e9e6-ea2c-ad96-68a7c972a371@yandex-team.ru> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.7 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 09.11.2022 um 17:00 hat Vladimir Sementsov-Ogievskiy geschrieben: > In subject: individual > > On 11/8/22 15:37, Kevin Wolf wrote: > > bdrv_reopen() and friends use subtree drains as a lazy way of covering > > all the nodes they touch. Turns out that this lazy way is a lot more > > complicated than just draining the nodes individually, even not > > accounting for the additional complexity in the drain mechanism itself. > > > > Simplify the code by switching to draining the individual nodes that are > > already managed in the BlockReopenQueue anyway. > > > > Signed-off-by: Kevin Wolf > > --- > > block.c | 11 ++++------- > > block/replication.c | 6 ------ > > blockdev.c | 13 ------------- > > 3 files changed, 4 insertions(+), 26 deletions(-) > > > > [..] > > > bdrv_reopen_queue_free(queue); > > - for (p = drained; p; p = p->next) { > > - BlockDriverState *bs = p->data; > > - AioContext *ctx = bdrv_get_aio_context(bs); > > - > > - aio_context_acquire(ctx); > > In bdrv_reopen_queue_free() we don't have this acquire()/release() > pair around bdrv_drained_end(). We don't need it anymore? Good catch, I think we do. Reopen is a bit messy with AioContext locks. I think the rule is supposed to be that bdrv_reopen_queue() requires that the lock for bs->aio_context is held, and bdrv_reopen_multiple() requires that no AioContext lock is held, right? Because the former is not actually true: qmp_blockdev_reopen() and the 'replication' block driver do indeed take the lock, but bdrv_reopen() drops it for both functions! So I think we also need an additional fix for bdrv_reopen() to drop the lock only after calling bdrv_reopen_queue(). It may not have made a difference before, but now that we call bdrv_drained_begin() in it, it seems important. Kevin