From patchwork Fri Sep 23 12:52:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Hanna Czenczek X-Patchwork-Id: 12986550 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 6C9ECECAAD8 for ; Fri, 23 Sep 2022 13:11:22 +0000 (UTC) Received: from localhost ([::1]:44000 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1obiSf-0002kU-EW for qemu-devel@archiver.kernel.org; Fri, 23 Sep 2022 09:11:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:50364) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obiBx-00040K-4c for qemu-devel@nongnu.org; Fri, 23 Sep 2022 08:54:18 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:41656) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1obiBu-0004JE-7Z for qemu-devel@nongnu.org; Fri, 23 Sep 2022 08:54:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1663937640; 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: content-transfer-encoding:content-transfer-encoding; bh=Zz569WJEubvpPwJ+/KedVaVljupcbLCXPMoPviUWJn0=; b=fogz9xShH5UIoDWdUziXUUCc6LL4s4rqPvgn3XD47fmEoOXoZ+lEMt9RjV7lx1wU21+UWY nVq/p07O1AcXSW5UHaWOKQDJDuil8skWGoqVuC1ug5vqhluhx8dd55qHlsxqPN3NiIJ5Wn wzhjSEApKNvi1QXRfvQCD+x9ICBpJz4= 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-611-F1Yq7LehN-aZv_AotDgFfA-1; Fri, 23 Sep 2022 08:52:29 -0400 X-MC-Unique: F1Yq7LehN-aZv_AotDgFfA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2D1D9882820; Fri, 23 Sep 2022 12:52:29 +0000 (UTC) Received: from localhost (unknown [10.39.194.96]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D2A142166B26; Fri, 23 Sep 2022 12:52:28 +0000 (UTC) From: Hanna Reitz To: qemu-block@nongnu.org Cc: qemu-devel@nongnu.org, Hanna Reitz , Kevin Wolf , Stefan Hajnoczi Subject: [PATCH 0/3] blcok: Start/end drain on correct AioContext Date: Fri, 23 Sep 2022 14:52:24 +0200 Message-Id: <20220923125227.300202-1-hreitz@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 Received-SPF: pass client-ip=170.10.133.124; envelope-from=hreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.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, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, PP_MIME_FAKE_ASCII_TEXT=0.001, RCVD_IN_DNSWL_LOW=-0.7, 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" Hi, bdrv_replace_child_noperm() drains the child via bdrv_parent_drained_{begin,end}_single(). When it removes a child, the bdrv_parent_drained_end_single() at its end will be called on an empty child, making the BDRV_POLL_WHILE() in it poll the main AioContext (because c->bs is NULL). That’s wrong, though, because it’s supposed to operate on the parent. bdrv_parent_drained_end_single_no_poll() will have scheduled any BHs in the parents’ AioContext, which may be anything, not necessarily the main context. Therefore, we must poll the parent’s context. Patch 3 does this for both bdrv_parent_drained_{begin,end}_single(). Patch 1 ensures that we can legally call bdrv_child_get_parent_aio_context() from those functions (currently marked as GLOBAL_STATE_CODE(), which I don’t think it is), and patch 2 fixes blk_do_set_aio_context() to not cause an assertion failure if it beginning a drain can end up in blk_get_aio_context() before blk->ctx has been updated. Hanna Reitz (3): block: bdrv_child_get_parent_aio_context is not GS block-backend: Update ctx immediately after root block: Start/end drain on correct AioContext block.c | 2 +- block/block-backend.c | 4 +++- block/io.c | 6 ++++-- 3 files changed, 8 insertions(+), 4 deletions(-)