From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: "Kevin Wolf" <kwolf@redhat.com>, "Max Reitz" <mreitz@redhat.com>,
"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
qemu-block@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v4 5/6] util: give a specific error message when O_DIRECT doesn't work
Date: Wed, 2 Sep 2020 18:10:27 +0100 [thread overview]
Message-ID: <20200902171027.GS403297@redhat.com> (raw)
In-Reply-To: <875z957ixy.fsf@dusky.pond.sub.org>
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
--
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next prev parent reply other threads:[~2020-09-02 17:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 17:20 [PATCH v4 0/6] block: improve error reporting for unsupported O_DIRECT Daniel P. Berrangé
2020-08-21 17:21 ` [PATCH v4 1/6] util: rename qemu_open() to qemu_open_old() Daniel P. Berrangé
2020-08-21 17:21 ` [PATCH v4 2/6] util: refactor qemu_open_old to split off variadic args handling Daniel P. Berrangé
2020-08-25 14:56 ` Markus Armbruster
2020-08-25 15:03 ` Daniel P. Berrangé
2020-08-26 11:19 ` Markus Armbruster
2020-08-21 17:21 ` [PATCH v4 3/6] util: add Error object for qemu_open_internal error reporting Daniel P. Berrangé
2020-08-25 15:14 ` Markus Armbruster
2020-08-25 15:36 ` Daniel P. Berrangé
2020-08-26 11:03 ` Markus Armbruster
2020-08-27 13:27 ` Daniel P. Berrangé
2020-08-21 17:21 ` [PATCH v4 4/6] util: introduce qemu_open and qemu_create with " Daniel P. Berrangé
2020-08-25 15:16 ` Markus Armbruster
2020-08-21 17:21 ` [PATCH v4 5/6] util: give a specific error message when O_DIRECT doesn't work Daniel P. Berrangé
2020-08-25 15:19 ` Markus Armbruster
2020-08-25 15:23 ` Daniel P. Berrangé
2020-08-26 11:19 ` Markus Armbruster
2020-09-02 17:10 ` Daniel P. Berrangé [this message]
2020-08-21 17:21 ` [PATCH v4 6/6] block/fileb: switch to use qemu_open/qemu_create for improved errors Daniel P. Berrangé
2020-08-25 15:28 ` Markus Armbruster
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