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Wed, 21 Feb 2024 13:37:39 +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 8Jw4L6P81WX1dQAAD6G6ig (envelope-from ); Wed, 21 Feb 2024 13:37:39 +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: <878r3exj3f.fsf@pond.sub.org> References: <20240220224138.24759-1-farosas@suse.de> <20240220224138.24759-33-farosas@suse.de> <878r3exj3f.fsf@pond.sub.org> Date: Wed, 21 Feb 2024 10:37:37 -0300 Message-ID: <87plwqaqfy.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=Zb6i8Et1; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=V546OEb3 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-1.52 / 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(-0.01)[46.90%]; 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)[-1.000]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from] X-Rspamd-Queue-Id: 7C34122194 Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; 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: > >> 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.