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From:   Chuck Lever <chuck.lever@oracle.com>
To:     Bruce Fields <bfields@fieldses.org>
CC:     Christoph Hellwig <hch@infradead.org>,
        Bruce Fields <bfields@redhat.com>,
        Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Trond Myklebust <trondmy@hammerspace.com>,
        Anna Schumaker <schumakeranna@gmail.com>
Subject: Re: [PATCH 1/2 v2] nfs: use change attribute for NFS re-exports
Thread-Topic: [PATCH 1/2 v2] nfs: use change attribute for NFS re-exports
Thread-Index: AQHW9nSnA3biWk5MsEeVX3kj9quDKKo/EesA
Date:   Fri, 29 Jan 2021 20:43:37 +0000
Message-ID: <E33A57FC-5B34-4621-B4FA-55FD0B5BBA28@oracle.com>
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 <20210120084638.GA3678536@infradead.org>
 <20210121202756.GA13298@pick.fieldses.org>
 <20210122082059.GA119852@infradead.org> <20210129192629.GC8033@fieldses.org>
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Hi Bruce-

> On Jan 29, 2021, at 2:26 PM, J. Bruce Fields <bfields@fieldses.org> wrote=
:
>=20
> From: "J. Bruce Fields" <bfields@redhat.com>
>=20
> When exporting NFS, we may as well use the real change attribute
> returned by the original server instead of faking up a change attribute
> from the ctime.
>=20
> Note we can't do that by setting I_VERSION--that would also turn on the
> logic in iversion.h which treats the lower bit specially, and that
> doesn't make sense for NFS.
>=20
> So instead we define a new export operation for filesystems like NFS
> that want to manage the change attribute themselves.
>=20
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>

These two patches have replaced the v1 patches from last week in
the for-next branch at

git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux.git

These are included provisionally while review and further testing
is ongoing.


> ---
> fs/nfs/export.c          | 18 ++++++++++++++++++
> fs/nfsd/nfsfh.h          |  5 ++++-
> include/linux/exportfs.h |  1 +
> 3 files changed, 23 insertions(+), 1 deletion(-)
>=20
> diff --git a/fs/nfs/export.c b/fs/nfs/export.c
> index 7412bb164fa7..f2b34cfe286c 100644
> --- a/fs/nfs/export.c
> +++ b/fs/nfs/export.c
> @@ -167,10 +167,28 @@ nfs_get_parent(struct dentry *dentry)
> 	return parent;
> }
>=20
> +static u64 nfs_fetch_iversion(struct inode *inode)
> +{
> +	struct nfs_server *server =3D NFS_SERVER(inode);
> +
> +	/* Is this the right call?: */
> +	nfs_revalidate_inode(server, inode);
> +	/*
> +	 * Also, note we're ignoring any returned error.  That seems to be
> +	 * the practice for cache consistency information elsewhere in
> +	 * the server, but I'm not sure why.
> +	 */
> +	if (server->nfs_client->rpc_ops->version >=3D 4)
> +		return inode_peek_iversion_raw(inode);
> +	else
> +		return time_to_chattr(&inode->i_ctime);
> +}
> +
> const struct export_operations nfs_export_ops =3D {
> 	.encode_fh =3D nfs_encode_fh,
> 	.fh_to_dentry =3D nfs_fh_to_dentry,
> 	.get_parent =3D nfs_get_parent,
> +	.fetch_iversion =3D nfs_fetch_iversion,
> 	.flags =3D EXPORT_OP_NOWCC|EXPORT_OP_NOSUBTREECHK|
> 		EXPORT_OP_CLOSE_BEFORE_UNLINK|EXPORT_OP_REMOTE_FS|
> 		EXPORT_OP_NOATOMIC_ATTR,
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index cb20c2cd3469..f58933519f38 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -12,6 +12,7 @@
> #include <linux/sunrpc/svc.h>
> #include <uapi/linux/nfsd/nfsfh.h>
> #include <linux/iversion.h>
> +#include <linux/exportfs.h>
>=20
> static inline __u32 ino_t_to_u32(ino_t ino)
> {
> @@ -264,7 +265,9 @@ fh_clear_wcc(struct svc_fh *fhp)
> static inline u64 nfsd4_change_attribute(struct kstat *stat,
> 					 struct inode *inode)
> {
> -	if (IS_I_VERSION(inode)) {
> +	if (inode->i_sb->s_export_op->fetch_iversion)
> +		return inode->i_sb->s_export_op->fetch_iversion(inode);
> +	else if (IS_I_VERSION(inode)) {
> 		u64 chattr;
>=20
> 		chattr =3D  stat->ctime.tv_sec;
> diff --git a/include/linux/exportfs.h b/include/linux/exportfs.h
> index 9f4d4bcbf251..fe848901fcc3 100644
> --- a/include/linux/exportfs.h
> +++ b/include/linux/exportfs.h
> @@ -213,6 +213,7 @@ struct export_operations {
> 			  bool write, u32 *device_generation);
> 	int (*commit_blocks)(struct inode *inode, struct iomap *iomaps,
> 			     int nr_iomaps, struct iattr *iattr);
> +	u64 (*fetch_iversion)(struct inode *);
> #define	EXPORT_OP_NOWCC			(0x1) /* don't collect v3 wcc data */
> #define	EXPORT_OP_NOSUBTREECHK		(0x2) /* no subtree checking */
> #define	EXPORT_OP_CLOSE_BEFORE_UNLINK	(0x4) /* close files before unlink =
*/
> --=20
> 2.29.2
>=20

--
Chuck Lever