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SubjectRe: [NFS] [PATCH] NFS server does not update mtime on setattr request
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On Wed, 2006-06-07 at 11:26 -0400, Peter Staubach wrote:
> J. Bruce Fields wrote:
>
> >On Wed, Jun 07, 2006 at 10:44:50AM -0400, Peter Staubach wrote:
> >
> >
> >>I saw that wording too and assumed what I think that you assumed. I
> >>assumed that that meant that if the new size is equal to the old size,
> >>then nothing should be changed. However, that does not seem to be how
> >>those words are to be interpreted. They are to be interpreted as "if
> >>the new length of the file can be successfully set, then the
> >>mtime/ctime should be changed".
> >>
> >>
> >
> >What's the basis for that interpretation? The language seems extremely
> >clear:
> >
> > "On successful completion, if the file size is changed, these
> > functions will mark for update the st_ctime and st_mtime fields
> > of the file, and if the file is a regular file, the S_ISUID and
> > S_ISGID bits of the file mode may be cleared."
> >
> >Why are you concerned about this? Do you have an actual application
> >that breaks?
> >
>
> Yes, there is a customer who is quite unhappy that the semantics over Linux
> client NFS are different than those of BSD, Solaris, and local file system
> access on Linux itself. The basis for my work is based on a bugzilla from
> this customer.
>
> My interpretation is based on looking at the local behavior on Linux, which
> changes mtime/ctime even if the file size does not change, and SunOS, which
> changes mtime/ctime even if the file size does not change and is very
> heavily SUSv3 compliant.
>
> In this case, "changed" does not mean "made different". It simply means
> that the file size is set to the new value.
>
> I would have chosen different words or a different interpretation too,
> but all of the evidence suggests that the semantics are as I stated.

We've already fixed this to be SuSv3 compliant for both create and
truncate. Your "safe" suggestion would break truncate again. That is why
it is being vetoed.

Cheers,
Trond

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