(2010/11/18 17:28), Philipp Hahn wrote:
> Hello,
>
> Am Donnerstag 18 November 2010 01:41:39 schrieb Hidetoshi Seto:
>> This patch introduce a fallback mechanism for old systems that do not
>> support utimensat(). This fix build failure with following warnings:
>
>> +#ifdef CONFIG_UTIMENSAT
>> + return utimensat(dirfd, path, times, flags);
>> +#else
>> + /* Fallback: use utimes() instead of utimensat() */
>
> Since we also had a problem with utimestat() some time ago with Samba
> <http://lists.samba.org/archive/samba-technical/2010-November/074613.html>
> I'd like to comment on that:
>
> Your have to be careful about compile-time-detection and runtime-detection:
> If
> you later run your utimestat()-enabled binary on an older kernel not
> supporting that syscall, you get -1 as the return-value and errno=ENOSYS. So
> even if you detected utimesatat() during compile-time, please always provide
> a fallback for run-time.
> This is less important for people compiling there own version of kvm, but is
> essential for Linux distributions, since people often run newer kvm versions
> on older kernels.
Hum, you have a good point.
Well, then I'll change it like:
-#ifdef CONFIG_UTIMENSAT
- return utimensat(dirfd, path, times, flags);
-#else
+ {
+ int ret = utimensat(dirfd, path, times, flags);
+ if (ret != -1 || errno != ENOSYS) {
+ return ret;
+ }
+ }
Thanks,
H.Seto
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