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 9417CC48BF8 for ; Thu, 22 Feb 2024 13:26:54 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rd95n-0002AP-TF; Thu, 22 Feb 2024 08:26:27 -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 1rd95j-00028f-KY for qemu-devel@nongnu.org; Thu, 22 Feb 2024 08:26:24 -0500 Received: from smtp-out1.suse.de ([195.135.223.130]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1rd95h-0002xu-KL for qemu-devel@nongnu.org; Thu, 22 Feb 2024 08:26:23 -0500 Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 6880C22121; Thu, 22 Feb 2024 13:26:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1708608378; h=from:from:reply-to: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=X90iM6miTr+pxUM9OWdvPcOsEAIioh5Ugv2mgfX5Nac=; b=A9TzbaqIpfJFcDEGVrcjTynm6ZVUzZIWklOmz7BOoP8HBxU4FJKylavV76bYX/f0rlUbmK +JdEOSHIcLgjYR7lFIx+AO1VvlC8ThvXlkHF01vEBE/PpjTV9TU4eeM1FeoZkggW+utPCS Jhs48xWS1YBFcRhDvirViKqJHBbyTqs= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1708608378; h=from:from:reply-to: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=X90iM6miTr+pxUM9OWdvPcOsEAIioh5Ugv2mgfX5Nac=; b=2AUP2POpSzQRZanCKcF/W9oY3/t6GRmEveC/N6Pmq2p5LfM0Trj8UrR29CmRz8pULiz92w dgoMOoTrST0GiLDw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1708608378; h=from:from:reply-to: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=X90iM6miTr+pxUM9OWdvPcOsEAIioh5Ugv2mgfX5Nac=; b=A9TzbaqIpfJFcDEGVrcjTynm6ZVUzZIWklOmz7BOoP8HBxU4FJKylavV76bYX/f0rlUbmK +JdEOSHIcLgjYR7lFIx+AO1VvlC8ThvXlkHF01vEBE/PpjTV9TU4eeM1FeoZkggW+utPCS Jhs48xWS1YBFcRhDvirViKqJHBbyTqs= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1708608378; h=from:from:reply-to: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=X90iM6miTr+pxUM9OWdvPcOsEAIioh5Ugv2mgfX5Nac=; b=2AUP2POpSzQRZanCKcF/W9oY3/t6GRmEveC/N6Pmq2p5LfM0Trj8UrR29CmRz8pULiz92w dgoMOoTrST0GiLDw== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id DB7EC13A8C; Thu, 22 Feb 2024 13:26:17 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 9zZAKHlL12VCOQAAD6G6ig (envelope-from ); Thu, 22 Feb 2024 13:26:17 +0000 From: Fabiano Rosas To: Markus Armbruster 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: <87a5ntyol6.fsf@pond.sub.org> References: <20240220224138.24759-1-farosas@suse.de> <20240220224138.24759-33-farosas@suse.de> <878r3exj3f.fsf@pond.sub.org> <87plwqaqfy.fsf@suse.de> <87a5ntyol6.fsf@pond.sub.org> Date: Thu, 22 Feb 2024 10:26:15 -0300 Message-ID: <87wmqwaavc.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=A9TzbaqI; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=2AUP2POp X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.51 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_FIVE(0.00)[5]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; NEURAL_HAM_SHORT(-0.20)[-0.997]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-Rspamd-Queue-Id: 6880C22121 Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, RCVD_IN_DNSWL_MED=-2.3, 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 Markus Armbruster writes: > Fabiano Rosas writes: > >> Markus Armbruster writes: >> >>> 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; >>> } >> >> This makes the O_DIRECT flag dictate the outcome when it's present. I >> want O_DIRECT to be considered only when all other flags have matched. >> >> Otherwise we regress the original use-case if the user happened to have >> put O_DIRECT in the flags. A non-match due to different O_ACCMODE would >> become a match due to (possibly) matching O_DIRECT. > > The fact that I missed this signifies one of two things: either was > suffering from code review brain (quite possible!), or this needs a > comment and/or clearer coding. > > If I understand you correctly, you want to return true when the bits > selected by the two masks together match. > > If we didn't need ifdeffery, we wouldn't use nested conditionals for > comparing bits under a mask. We'd use something like > > int mask = O_ACCMODE | O_DIRECT; > > return (flags & mask) == (fd_flags & mask); > > Bring back the ifdeffery: > > int mask = O_ACCMODE; > > #ifdef O_DIRECT > mask |= O_DIRECT; > #endif > > return (flags & mask) == (fd_flags & mask); Could be. I'll change it. > > Or maybe even > > #ifndef O_DIRECT > #define O_DIRECT 0 > #endif > > int mask = O_ACCMODE | O_DIRECT; > > return (flags & mask) == (fd_flags & mask); > > Not sure this is even worth a helper function. Agreed. > > Or am I stull suffering from code review brain? Yes, stull suffering. =)