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Wed, 8 Jul 2020 06:45:48 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id F05101132FD2; Wed, 8 Jul 2020 08:45:46 +0200 (CEST) From: Markus Armbruster To: Daniel P. =?utf-8?Q?Berrang=C3=A9?= Subject: Re: [PATCH v2 1/3] util: validate whether O_DIRECT is supported after failure References: <20200702125612.2176194-1-berrange@redhat.com> <20200702125612.2176194-2-berrange@redhat.com> Date: Wed, 08 Jul 2020 08:45:46 +0200 In-Reply-To: <20200702125612.2176194-2-berrange@redhat.com> ("Daniel P. =?utf-8?Q?Berrang=C3=A9=22's?= message of "Thu, 2 Jul 2020 13:56:10 +0100") Message-ID: <878sfu4i91.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=207.211.31.81; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/07/07 17:25:09 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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: , Cc: Kevin Wolf , qemu-block@nongnu.org, qemu-devel@nongnu.org, P J P , Max Reitz , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Daniel P. Berrang=C3=A9 writes: > Currently we suggest that a filesystem may not support O_DIRECT after > seeing an EINVAL. Other things can cause EINVAL though, so it is better > to do an explicit check, and then report a definitive error message. > > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > util/osdep.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/util/osdep.c b/util/osdep.c > index 4829c07ff6..e2b7507ee2 100644 > --- a/util/osdep.c > +++ b/util/osdep.c > @@ -332,9 +332,11 @@ int qemu_open(const char *name, int flags, ...) > } > =20 > #ifdef O_CLOEXEC > - ret =3D open(name, flags | O_CLOEXEC, mode); > -#else > + flags |=3D O_CLOEXEC; > +#endif > ret =3D open(name, flags, mode); > + > +#ifndef O_CLOEXEC > if (ret >=3D 0) { > qemu_set_cloexec(ret); > } I'd prefer something like #ifdef O_CLOEXEC flags |=3D O_CLOEXEC; ret =3D open(name, flags, mode); #else ret =3D open(name, flags, mode); if (ret >=3D 0) { qemu_set_cloexec(ret); } #endif Continues to duplicate open(), but spares me the effort to fuse two #ifdef sections in my head to understand what is being done in each case. > @@ -342,8 +344,13 @@ int qemu_open(const char *name, int flags, ...) > =20 > #ifdef O_DIRECT > if (ret =3D=3D -1 && errno =3D=3D EINVAL && (flags & O_DIRECT)) { > - error_report("file system may not support O_DIRECT"); > - errno =3D EINVAL; /* in case it was clobbered */ > + int newflags =3D flags & ~O_DIRECT; > + ret =3D open(name, newflags, mode); I'd prefer the more concise ret =3D open(name, flags & ~O_DIRECT, mode); > + if (ret !=3D -1) { > + close(ret); > + error_report("file system does not support O_DIRECT"); > + errno =3D EINVAL; > + } > } > #endif /* O_DIRECT */ The function now reports to stderr in just one of many failure modes. That's wrong. Looks like the next patch fixes this defect. I'd swap the two.