[patch 1/4 v2] vfs: utimensat(): ignore tv_sec if tv_nsec == UTIME_OMIT or UTIME_NOW

[Michael Kerrisk <mtk.manpages@googlemail.com>]

The POSIX.1 draft spec for utimensat() says that if a times[n].tv_nsec
field is UTIME_OMIT or UTIME_NOW, then the value in the corresponding
tv_sec field is ignored.  See the last sentence of this para, from
the spec:

    If the tv_nsec field of a timespec structure has
    the special value UTIME_NOW, the file's relevant
    timestamp shall be set to the greatest value
    supported by the file system that is not greater than
    the current time. If the tv_nsec field has the
    special value UTIME_OMIT, the file's relevant
    timestamp shall not be changed. In either case,
    the tv_sec field shall be ignored.

However the current Linux implementation requires the tv_sec value to be
zero (or the EINVAL error results). This requirement should be removed.

CC: Miklos Szeredi <miklos@szeredi.hu>
CC: Al Viro <viro@zeniv.linux.org.uk>
CC: Ulrich Drepper <drepper@redhat.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

--- linux-2.6.26-rc4/fs/utimes.c	2008-06-04 13:23:38.000000000 +0200
+++ linux-2.6.26-rc4-utimensat-fix-v4/fs/utimes.c	2008-06-04 13:22:44.000000000 +0200
@@ -169,14 +169,6 @@
 	if (utimes) {
 		if (copy_from_user(&tstimes, utimes, sizeof(tstimes)))
 			return -EFAULT;
-		if ((tstimes[0].tv_nsec == UTIME_OMIT ||
-		     tstimes[0].tv_nsec == UTIME_NOW) &&
-		    tstimes[0].tv_sec != 0)
-			return -EINVAL;
-		if ((tstimes[1].tv_nsec == UTIME_OMIT ||
-		     tstimes[1].tv_nsec == UTIME_NOW) &&
-		    tstimes[1].tv_sec != 0)
-			return -EINVAL;

 		/* Nothing to do, we must not even check the path.  */
 		if (tstimes[0].tv_nsec == UTIME_OMIT &&