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Wed, 2 Sep 2020 17:10:30 +0000 (UTC) Date: Wed, 2 Sep 2020 18:10:27 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Markus Armbruster Subject: Re: [PATCH v4 5/6] util: give a specific error message when O_DIRECT doesn't work Message-ID: <20200902171027.GS403297@redhat.com> References: <20200821172105.608752-1-berrange@redhat.com> <20200821172105.608752-6-berrange@redhat.com> <87o8mybvmu.fsf@dusky.pond.sub.org> <20200825152319.GX107278@redhat.com> <875z957ixy.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <875z957ixy.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0.001 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.61; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/02 03:24:55 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Kevin Wolf , Max Reitz , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-block@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Aug 26, 2020 at 01:19:53PM +0200, Markus Armbruster wrote: > Now back to my dislike of the #ifdeffery I voiced in reply to PATCH 2. > > Code now: > > #ifdef O_CLOEXEC > flags |= O_CLOEXEC; > #endif /* O_CLOEXEC */ > > ret = open(name, flags, mode); > > #ifndef O_CLOEXEC > if (ret >= 0) { > qemu_set_cloexec(ret); > } > #endif /* ! O_CLOEXEC */ > > if (ret == -1) { > const char *action = flags & O_CREAT ? "create" : "open"; > #ifdef O_DIRECT > if (errno == EINVAL && (flags & O_DIRECT)) { > ret = open(name, flags & ~O_DIRECT, mode); > if (ret != -1) { > close(ret); > [O_DIRECT not supported error...] > errno = EINVAL; /* close() clobbered earlier errno */ > return -1; > } > } > #endif /* O_DIRECT */ > [generic error...] > } > > Compare: > > #ifdef O_CLOEXEC > flags |= O_CLOEXEC; > ret = open(name, flags, mode); > #else > ret = open(name, flags, mode); > if (ret >= 0) { > qemu_set_cloexec(ret); > } > #endif /* ! O_CLOEXEC */ > > if (ret == -1) { > const char *action = flags & O_CREAT ? "create" : "open"; > #ifdef O_DIRECT > if (errno == EINVAL && (flags & O_DIRECT)) { > ret = open(name, flags & ~O_DIRECT, mode); > if (ret != -1) { > close(ret); > [O_DIRECT not supported error...] > errno = EINVAL; /* close() clobbered earlier errno */ > return -1; > } > } > #endif /* O_DIRECT */ > [generic error...] > } > > I like this a bit better, but not enough to make a strong > recommendation, let alone demand. In v5 I've gone with neither approach, and instead spun off a helper method qemu_open_cloexec which I think is clearer than both. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|