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 1CDF5C48BEB for ; Wed, 21 Feb 2024 15:46:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rcoYS-0005s0-QO; Wed, 21 Feb 2024 10:30:42 -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 1rcoNM-0006Nd-JC for qemu-devel@nongnu.org; Wed, 21 Feb 2024 10:19:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rcitP-0003Ab-5x for qemu-devel@nongnu.org; Wed, 21 Feb 2024 04:27:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1708507674; 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=UgCoAvodRLVzHJkgildrLHAc/XRACmSJVVWSYWw3g44=; b=cyGEFNsrmUwcB/yn8D0xrB3MFfBHE/xran4Ar84eJkLZQ/fIoCRAqX5WppdriQmVC46y3b kKTIjyb0Rk52XHTNLuqOp7+mb99b5sjAlEdkqrdxIjCZvbxOF0sEGdG1j0AqM6xHylRbnK Ydc6xDGLHtnijrTIjcvdcEmOrrn5jSw= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-660-_MkwwRkmMkm-fha1rgxBBA-1; Wed, 21 Feb 2024 04:27:50 -0500 X-MC-Unique: _MkwwRkmMkm-fha1rgxBBA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 159A538143AF; Wed, 21 Feb 2024 09:27:50 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.55]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E64B240C94A7; Wed, 21 Feb 2024 09:27:49 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id E9D1321E6740; Wed, 21 Feb 2024 10:27:48 +0100 (CET) From: Markus Armbruster To: Fabiano Rosas Cc: qemu-devel@nongnu.org, berrange@redhat.com, Peter Xu , Claudio Fontana Subject: Re: [PATCH v4 32/34] monitor: fdset: Match against O_DIRECT In-Reply-To: <20240220224138.24759-33-farosas@suse.de> (Fabiano Rosas's message of "Tue, 20 Feb 2024 19:41:36 -0300") References: <20240220224138.24759-1-farosas@suse.de> <20240220224138.24759-33-farosas@suse.de> Date: Wed, 21 Feb 2024 10:27:48 +0100 Message-ID: <878r3exj3f.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.133.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, 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_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 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: 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 Fabiano Rosas writes: > We're about to enable the use of O_DIRECT in the migration code and > due to the alignment restrictions imposed by filesystems we need to > make sure the flag is only used when doing aligned IO. > > The migration will do parallel IO to different regions of a file, so > we need to use more than one file descriptor. Those cannot be obtained > by duplicating (dup()) since duplicated file descriptors share the > file status flags, including O_DIRECT. If one migration channel does > unaligned IO while another sets O_DIRECT to do aligned IO, the > filesystem would fail the unaligned operation. > > The add-fd QMP command along with the fdset code are specifically > designed to allow the user to pass a set of file descriptors with > different access flags into QEMU to be later fetched by code that > needs to alternate between those flags when doing IO. > > Extend the fdset matching function to behave the same with the > O_DIRECT flag. > > Signed-off-by: Fabiano Rosas > --- > monitor/fds.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/monitor/fds.c b/monitor/fds.c > index 9a28e4b72b..42bf3eb982 100644 > --- a/monitor/fds.c > +++ b/monitor/fds.c > @@ -413,6 +413,12 @@ static bool monitor_fdset_flags_match(int flags, int fd_flags) static bool monitor_fdset_flags_match(int flags, int fd_flags) { bool match = false; > if ((flags & O_ACCMODE) == (fd_flags & O_ACCMODE)) { > match = true; > + > +#ifdef O_DIRECT > + if ((flags & O_DIRECT) != (fd_flags & O_DIRECT)) { > + match = false; > + } > +#endif > } > > return match; } I'd prefer something like static bool monitor_fdset_flags_match(int flags, int fd_flags) { #ifdef O_DIRECT if ((flags & O_DIRECT) != (fd_flags & O_DIRECT)) { return false; } #endif if ((flags & O_ACCMODE) != (fd_flags & O_ACCMODE)) { return false; } return true; }