On Thu, 26 Apr 2007 18:49:05 -0400 Ulrich Drepper <[EMAIL PROTECTED]> wrote:
> > The next revision of POSIX will support fine-grained filesystem timestamps > the way we already support. struct stat will report nanosecond values. So > far so good. > > During the development one additional problem was found: there is no > interface to set the file timestamp with that precision. utimes only takes a > timeval structure which allows only micro-second resolution. Does the spec say what the OS should do if (ts_nsec => 1e9)? > This is why the utimensat() interface was created. It is basically the same > as our futimesat() interface but it takes a timespec structure. > > While adding this new interface two more features got added. Programmers > sometimes/often only want to set one value. This currently requires reading > the current value with stat() and then use this value in the futimesat() > call. This is slow and might create even wrong results (the file could have > been updated in the meantime). If the tv_nsec value of either of the > elements of the utimes parameter to utimensat() is UTIME_OMIT no update of > that respective value is performed. ITYM "If the value of either of the elements..." +#define UTIME_NOW ((1l << 30) - 1l) +#define UTIME_OMIT ((1l << 30) - 2l) OK, so there's no collision on ts_nsec if unnormalised timespecs are disallowed. But there's a potential collision on ts_sec? Do we know what date that corresponds to? > The second extension allows to set one of the values to the correct current > time. Today it is only possible to set both values at the same time. Once > again this is slower and might to lead to incorrect results. The use of > UTIME_NOW for the respective tv_nsec value implements this functionality. > > The resulting patch is attached. It modifies the do_utimes function which is > also used in the compat code. The callers are adjusted. Most of the added > code are checks for invalid parameters. In fact, I think one problem where > the old code wouldn't recognize certain overflows (if tv_nsec * 1000 > overflows). > > I've tested the code on x86-64. Do you have a testcase app which can be used by arch maintainers? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
