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Re: [fuse-devel] utimensat fails to update ctime

To: ctrn3e8 <ctrn3e8@xxxxxxxxx>
Subject: Re: [fuse-devel] utimensat fails to update ctime
From: Eric Blake <ebb9@xxxxxxx>
Date: Wed, 23 Dec 2009 17:50:04 -0700
Cc: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>, Jean-Pierre André <jean-pierre.andre@xxxxxxxxxx>, fuse-devel@xxxxxxxxxxxxxxxxxxxxx, Miklos Szeredi <miklos@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, xfs@xxxxxxxxxxx, bug-coreutils <bug-coreutils@xxxxxxx>
In-reply-to: <4B32B303.6070807@xxxxxxxxx>
References: <4B2B156D.9040604@xxxxxxx> <87aaxclr4q.fsf@xxxxxxxxxxxxxxxxxxx> <4B2F7421.10005@xxxxxxx> <4B2F7A95.3010708@xxxxxxx> <87hbrkjrk8.fsf@xxxxxxxxxxxxxxxxxxx> <4B304D04.6040501@xxxxxxx> <87d427jscr.fsf@xxxxxxxxxxxxxxxxxxx> <4B3097C4.3060803@xxxxxxxxxx> <874onjjnln.fsf@xxxxxxxxxxxxxxxxxxx> <4B30B67A.7080703@xxxxxxxxxx> <87ljgvi1an.fsf@xxxxxxxxxxxxxxxxxxx> <4B30F0C9.2020702@xxxxxxxxxx> <87my1aevro.fsf@xxxxxxxxxxxxxxxxxxx> <4B3212ED.4090208@xxxxxxx> <4B32B303.6070807@xxxxxxxxx>
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According to ctrn3e8 on 12/23/2009 5:17 PM:
> The strace has the following function call  (and it may be because I am
> looking at the trace rather than the actual source):

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

> The two don't seem to match.  Is this just because of the way the trace is 
> printed?

Yes.  When the tv_nsec field is UTIME_OMIT or UTIME_NOW, the tv_sec field
is irrelevant.  Therefore, to save on space, strace omits the tv_sec field
in its output.  But rest assured that the kernel has read access to all
four 32-bit words located at the timespec pointer passed in the syscall.

> No mention of ntfs-3g support for nanosecond time stamping.

Read the rest of the thread on lkml - that is a known issue, which will
probably not be solved any sooner than January (all the patches this week
only dealt with mishandling of UTIME_OMIT).

- --
Don't work too hard, make some time for fun as well!

Eric Blake             ebb9@xxxxxxx
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