Messages in this thread | | | From | OGAWA Hirofumi <> | Subject | Re: utimensat fails to update ctime | Date | Mon, 21 Dec 2009 16:31:49 +0900 |
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Eric Blake <ebb9@byu.net> writes:
> POSIX requires that utimensat/futimens must update ctime in all cases > where any change is made (it only exempts when both atime and mtime were > requested as UTIME_OMIT, where the file must exist but no change is made). > Unfortunately, when atime is specified and mtime is UTIME_OMIT, the > kernel mistakenly behaves like read(), by updating atime but not ctime. > This in turn caused a regression in coreutils 8.2, visible through 'touch -a': > http://lists.gnu.org/archive/html/bug-coreutils/2009-12/msg00171.html > > Here is a simple program demonstrating the failure: > $ cat foo.c > #include <fcntl.h> > #include <unistd.h> > #include <sys/stat.h> > int > main () > { > int fd = creat ("file", 0600); > struct stat st1, st2; > struct timespec t[2] = { { 1000000000, 0 }, { 0, UTIME_OMIT } }; > fstat (fd, &st1); > sleep (1); > futimens (fd, t); > fstat (fd, &st2); > return st1.st_ctime == st2.st_ctime; > } > $ gcc -o foo foo.c -D_GNU_SOURCE > $ ./foo; echo $? > 1 > > The exit status should have been 0. > > GNU coreutils will end up working around the bug by calling fstat/[l]stat > prior to futimens/utimensat, and populating the mtime field with the > desired value rather than using UTIME_OMIT. But this is a pointless stat > call, which could be avoided if the kernel were fixed to comply with POSIX > by updating ctime even when mtime is UTIME_OMIT.
I couldn't reproduce this with your test program on my machine (latest linus tree). And that utime path looks like no problem, um..., can you provide output of strace or something?
Thanks. -- OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
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