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    SubjectRe: [PATCH] xfs: correct statx's result_mask value
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    On 1/7/19 11:15 PM, Su Yanjun <suyj.fnst@cn.fujitsu.com> wrote:
    >
    >
    > On 1/8/2019 1:07 PM, Darrick J. Wong wrote:
    >> On Tue, Jan 08, 2019 at 12:58:43PM +0800, Su Yanjun <suyj.fnst@cn.fujitsu.com> wrote:
    >>>
    >>> On 1/8/2019 2:04 AM, Eric Sandeen wrote:
    >>>> On 1/7/19 11:52 AM, Darrick J. Wong wrote:
    >>>>> On Mon, Jan 07, 2019 at 04:53:10AM -0500, Su Yanjun wrote:
    >>>>>> For statx syscall, xfs return the wrong result_mask.
    >>>>>>
    >>>>>> Signed-off-by: Su Yanjun<suyj.fnst@cn.fujitsu.com>
    >>>>>> ---
    >>>>>>    fs/xfs/xfs_iops.c | 3 +++
    >>>>>>    1 file changed, 3 insertions(+)
    >>>>>>
    >>>>>> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
    >>>>>> index f48ffd7..3811457 100644
    >>>>>> --- a/fs/xfs/xfs_iops.c
    >>>>>> +++ b/fs/xfs/xfs_iops.c
    >>>>>> @@ -521,6 +521,9 @@ xfs_vn_getattr(
    >>>>>>                stat->btime.tv_nsec = ip->i_d.di_crtime.t_nsec;
    >>>>>>            }
    >>>>>>        }
    >>>>>> +   
    >>>>>> +    /* Only return mask that we care */
    >>>>>> +    stat->result_mask &= request_mask;
    >>>>> Why not just:
    >>>>>
    >>>>>     stat->result_mask = STATX_BASIC_STATS;
    >>>>>
    >>>>> at the top of the function?
    >>>>>
    >>>>> I don't see the need to mask off result_mask at all, since we could some
    >>>>> day elect to return more than what's in request_mask...
    >>> When we run xfstests with nfs, the generic/423 case runs failed. So i review
    >>> the nfs'
    >>> nfs_getattr code it does validate the request_mask.
    >>>
    >>> Then i review the xfs' getattr code, it has no such check. Whatever
    >>> request_mask
    >>>   is set, the stat's result_mask always the 0x7ff.
    >> Yes, statx can return more data than what userspace callers ask for:
    >>
    >>> Maybe it has Unclear semantics about statx's result_mask.
    >> "A filesystem may also fill in fields that the caller didn't ask for if
    >> it has values for them available and the information is available at no
    >> extra cost.  If this happens, the  corresponding  bits will be set in
    >> stx_mask."
    >>
    >> --D
    >
    > I get it, then the testcase generic/423 may need update in xfstests.
    > Thanks for your reply.

    Can you please share the details of the failure you're seeing when you run
    it over nfs?

    Thanks,
    -=Eric

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