From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Ondrej Valousek <ondrej.valousek.xm@renesas.com>
CC:     Bruce Fields <bfields@fieldses.org>,
        Trond Myklebust <trondmy@hammerspace.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        Anna Schumaker <anna.schumaker@netapp.com>,
        "trondmy@kernel.org" <trondmy@kernel.org>
Subject: Re: [PATCH 0/8] Support btime and other NFSv4 specific attributes
Thread-Topic: [PATCH 0/8] Support btime and other NFSv4 specific attributes
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Date:   Thu, 6 Jan 2022 16:59:12 +0000
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> On Jan 6, 2022, at 11:13 AM, Ondrej Valousek <ondrej.valousek.xm@renesas.=
com> wrote:
>=20
> So I think this is what we eventually need (thanks for the pointers you g=
ave me!):
>=20
> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> index 5a93a5db4fb0..e88ae4ce5263 100644
> --- a/fs/nfsd/nfs4xdr.c
> +++ b/fs/nfsd/nfs4xdr.c
> @@ -2865,6 +2865,9 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct s=
vc_fh *fhp,
>        err =3D vfs_getattr(&path, &stat, STATX_BASIC_STATS, AT_STATX_SYNC=
_AS_STAT);
>        if (err)
>                goto out_nfserr;
> +       if (! stat.result_mask & STATX_BTIME)
> +               /* underlying FS does not offer btime so we can't share i=
t */
> +               bmval1 &=3D ~FATTR4_WORD1_TIME_CREATE;
>        if ((bmval0 & (FATTR4_WORD0_FILES_AVAIL | FATTR4_WORD0_FILES_FREE =
|
>                        FATTR4_WORD0_FILES_TOTAL | FATTR4_WORD0_MAXNAME)) =
||
>            (bmval1 & (FATTR4_WORD1_SPACE_AVAIL | FATTR4_WORD1_SPACE_FREE =
|
> @@ -3265,6 +3268,14 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct =
svc_fh *fhp,
>                p =3D xdr_encode_hyper(p, (s64)stat.mtime.tv_sec);
>                *p++ =3D cpu_to_be32(stat.mtime.tv_nsec);
>        }
> +       /* support for btime here */
> +        if (bmval1 & FATTR4_WORD1_TIME_CREATE) {
> +                p =3D xdr_reserve_space(xdr, 12);
> +                if (!p)
> +                        goto out_resource;
> +                p =3D xdr_encode_hyper(p, (s64)stat.btime.tv_sec);
> +                *p++ =3D cpu_to_be32(stat.btime.tv_nsec);
> +        }
>        if (bmval1 & FATTR4_WORD1_MOUNTED_ON_FILEID) {
>                struct kstat parent_stat;
>                u64 ino =3D stat.ino;
>=20
> diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h
> index 498e5a489826..5ef056ce7591 100644
> --- a/fs/nfsd/nfsd.h
> +++ b/fs/nfsd/nfsd.h
> @@ -364,7 +364,7 @@ void                nfsd_lockd_shutdown(void);
>  | FATTR4_WORD1_OWNER          | FATTR4_WORD1_OWNER_GROUP  | FATTR4_WORD1=
_RAWDEV           \
>  | FATTR4_WORD1_SPACE_AVAIL     | FATTR4_WORD1_SPACE_FREE   | FATTR4_WORD=
1_SPACE_TOTAL      \
>  | FATTR4_WORD1_SPACE_USED      | FATTR4_WORD1_TIME_ACCESS  | FATTR4_WORD=
1_TIME_ACCESS_SET  \
> - | FATTR4_WORD1_TIME_DELTA   | FATTR4_WORD1_TIME_METADATA    \
> + | FATTR4_WORD1_TIME_DELTA   | FATTR4_WORD1_TIME_METADATA   | FATTR4_WOR=
D1_TIME_CREATE      \
>  | FATTR4_WORD1_TIME_MODIFY     | FATTR4_WORD1_TIME_MODIFY_SET | FATTR4_W=
ORD1_MOUNTED_ON_FILEID)
>=20
> #define NFSD4_SUPPORTED_ATTRS_WORD2 0
>=20
> Legal Disclaimer: This e-mail communication (and any attachment/s) is con=
fidential and contains proprietary information, some or all of which may be=
 legally privileged. It is intended solely for the use of the individual or=
 entity to which it is addressed. Access to this email by anyone else is un=
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 is prohibited and may be unlawful.

Thanks, Ondrej.

This looks like an interesting new feature, however it's a little
late for the v5.17 merge window, IMO. (On the plus side, that gives
us a month or two for further review and deeper testing).

Also, the change needs to be submitted as a real patch. See the

   Documentation/process/submitting-patches.rst=20

file in the Linux kernel tree for information on the p's and q's.
In particular:

 -- you need a short and full patch description. The "Describe
    your changes" section explains the details.

 -- you need to ensure your employer permits you to contribute
    to the Linux kernel under GPLv2. The "Sign your work - the
    Developer's Certificate of Origin" section explains this.

I'm a little concerned about your Legal Disclaimer which suggests
that anything you have sent in e-mail is already owned by Renesas
and is therefore constrained for submission to the kernel. Before
submitting again, can you ask your legal team for clarification?

--
Chuck Lever