Re: [PATCH v2 5/5] nfs: don't clear STATX_ATIME from result_mask

From: Miklos Szeredi
Date: Fri Oct 19 2018 - 16:48:39 EST

On Fri, Oct 19, 2018 at 8:14 PM, Trond Myklebust
<trondmy@xxxxxxxxxxxxxxx> wrote:
> On Fri, 2018-10-19 at 19:46 +0200, Miklos Szeredi wrote:

>> How is it then that only STATX_ATIME is cleared and not the other
>> fields?
> It isn't just the atime. We can also fail to revalidate the ctime and
> mtime if they are not being requested by the user.
>> Note: junk != stale. The statx definition doesn't talk about the
>> fields being up-to-date, except for AT_STATX_FORCE_SYNC, so stale
>> attributes are okay, and do not warrant clearing the result_mask.
> I disagree. stale == junk here, because the default of
> AT_STATX_SYNC_AS_STAT is described by the manpage as "Do whatever
> stat(2) does." which this is not.

Ah, you are talking about this:

/* Is the user requesting attributes that might need revalidation? */
goto out_no_update;

Well, if this is triggered for statx(..., STATX_ATIME,
AT_STATX_SYNC_AS_STAT) and MNT_NOATIME, then yes, result will be junk.
Which means that the code is wrong, it shouldn't do that.

Otherwise (if something other than STATX_ATIME or STATX_INO or
STATX_TYPE is given as well) it *will* do the same thing as what
stat(2) does, so in that case STATX_ATIME should not be cleared (yet
it is cleared).

I can do a patch, but not tonight...