Re: utimensat fails to update ctime

OGAWA Hirofumi
2009-12-22T09:00:02Z

Eric Blake <ebb9@byu.net> writes:

> According to OGAWA Hirofumi on 12/21/2009 8:05 AM:
>>> It may also be file-system dependent. On the machine where I saw the
>>> original failure:
>>>> $ uname -a
>>>> Linux fencepost 2.6.26-2-xen-amd64 #1 SMP Thu Nov 5 04:27:12 UTC 2009
>>>> x86_64 GNU/Linux
>>> $ df -T .
>>> Filesystem Type 1K-blocks Used Available Use% Mounted on
>>> /dev/sdb1 xfs 419299328 269018656 150280672 65% /srv/data
>>
>> Thanks.
>>
>> This is good point. This would be xfs issue or design. xfs seems to have
>> own special handling of ctime.
>
> Here's another report, this time about an mtime update not happening on
> ntfs-3g. http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/19336

It is likely the issue of libfuse or ntfs-3g. I don't know about ntfs-3g
people at all. So, for now, just Cc: to fuse people.

> utimensat(0, NULL, {UTIME_OMIT, UTIME_NOW}, 0) = 0

>From this, "ia_valid" will have "ATTR_CTIME | ATTR_MTIME". And the
request would pass to userland via fuse of kernel part, then it will be
handled by libfuse.

>From quick grep of libfuse and ntfs-3g (would not be latest), ntfs-3g is
using "struct fuse_operations", not "struct fuse_lowlevel_ops".

So, fuse_lib_setattr() would be the handler for it in libfuse. And, from
the following part, it seems to require the both of MTIME and ATIME to
call ntfs-3g's ->utime handler.

I don't know whether it is limitation or bug in fuse_operations.
Any ideas?

if (!err &&
(valid & (FUSE_SET_ATTR_ATIME | FUSE_SET_ATTR_MTIME)) ==
(FUSE_SET_ATTR_ATIME | FUSE_SET_ATTR_MTIME)) {
struct timespec tv[2];
tv[0].tv_sec = attr->st_atime;
tv[0].tv_nsec = ST_ATIM_NSEC(attr);
tv[1].tv_sec = attr->st_mtime;
tv[1].tv_nsec = ST_MTIM_NSEC(attr);
err = fuse_fs_utimens(f->fs, path, tv);
}

Thanks.
--
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>