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Re: utimensat fails to update ctime

To: Eric Blake <ebb9@xxxxxxx>
Subject: Re: utimensat fails to update ctime
From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Date: Tue, 22 Dec 2009 18:00:36 +0900
Cc: Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, Christoph Hellwig <hch@xxxxxx>, Miklos Szeredi <miklos@xxxxxxxxxx>, fuse-devel@xxxxxxxxxxxxxxxxxxxxx
In-reply-to: <4B304D04.6040501@xxxxxxx> (Eric Blake's message of "Mon, 21 Dec 2009 21:37:24 -0700")
References: <4B2B156D.9040604@xxxxxxx> <87aaxclr4q.fsf@xxxxxxxxxxxxxxxxxxx> <4B2F7421.10005@xxxxxxx> <4B2F7A95.3010708@xxxxxxx> <87hbrkjrk8.fsf@xxxxxxxxxxxxxxxxxxx> <4B304D04.6040501@xxxxxxx>
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.1.90 (gnu/linux)
Eric Blake <ebb9@xxxxxxx> 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@xxxxxxxxxxxxxxxxxx>

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