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 0C020C433FE for ; Wed, 27 Apr 2022 16:13:24 +0000 (UTC) Received: from localhost ([::1]:57344 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1njkI7-00029d-36 for qemu-devel@archiver.kernel.org; Wed, 27 Apr 2022 12:13:23 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51872) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1njkAj-00021N-JU for qemu-devel@nongnu.org; Wed, 27 Apr 2022 12:05:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51250) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1njkAg-00062j-OV for qemu-devel@nongnu.org; Wed, 27 Apr 2022 12:05:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651075542; 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=1NjJqv6ImhofR4h6mItDP8C4Zka1Nf7Nm3gNYXsIMws=; b=fHVU+JN+LO6pV4z0srBGtIIhscO5RTNyJCuADD2q+yALgZO7BNfHtyUIlzFe0VKj/jX3qF C6HAyRWqFNMEI9emzBRoJu8aoi0t7Rh5EhFIMahpL+gNB/iWWjClLFqHLnCpdS9qTs+qr8 bW+xIbYVNQRC9qdN1FSEAMq0TAW5s/Y= 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-516-at7dwll0OiCrsrjRYlNFqA-1; Wed, 27 Apr 2022 12:05:38 -0400 X-MC-Unique: at7dwll0OiCrsrjRYlNFqA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1D13F801005; Wed, 27 Apr 2022 16:05:38 +0000 (UTC) Received: from redhat.com (unknown [10.39.195.52]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 45B2E401A992; Wed, 27 Apr 2022 16:05:37 +0000 (UTC) Date: Wed, 27 Apr 2022 18:05:35 +0200 From: Kevin Wolf To: Hanna Reitz Subject: Re: [PATCH 2/4] qcow2: Do not reopen data_file in invalidate_cache Message-ID: References: <20220427114057.36651-1-hreitz@redhat.com> <20220427114057.36651-3-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220427114057.36651-3-hreitz@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.082, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: , Cc: Emanuele Giuseppe Esposito , Paolo Bonzini , qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 27.04.2022 um 13:40 hat Hanna Reitz geschrieben: > qcow2_co_invalidate_cache() closes and opens the qcow2 file, by calling > qcow2_close() and qcow2_do_open(). These two functions must thus be > usable from both a global-state and an I/O context. > > As they are, they are not safe to call in an I/O context, because they > use bdrv_unref_child() and bdrv_open_child() to close/open the data_file > child, respectively, both of which are global-state functions. When > used from qcow2_co_invalidate_cache(), we do not need to close/open the > data_file child, though (we do not do this for bs->file or bs->backing > either), and so we should skip it in the qcow2_co_invalidate_cache() > path. > > To do so, add a parameter to qcow2_do_open() and qcow2_close() to make > them skip handling s->data_file, and have qcow2_co_invalidate_cache() > exempt it from the memset() on the BDRVQcow2State. > > (Note that the QED driver similarly closes/opens the QED image by > invoking bdrv_qed_close()+bdrv_qed_do_open(), but both functions seem > safe to use in an I/O context.) > > Fixes: https://gitlab.com/qemu-project/qemu/-/issues/945 > Signed-off-by: Hanna Reitz This feels a bit like a hack, and we'll have to change it again if we ever want to allow changing the data_file with reopen. But it should do the job for now. Kevin