[PATCH v3 07/13] nfsd: fix reported change attr on a write delegation

[Jeff Layton <jlayton@kernel.org>]

If there's a write deleg outstanding and there are no writes yet from
the client, we'll currently just report the old, original change attr.

RFC 8881, section 10.4.3 describes a way to report the change attribute.

When there are no writes from the client yet, but the reported change
attribute in a CB_GETATTR indicates that the file has been modified,
then report the initial change attr + 1.

Once there have been writes from the client, use the value in the inode
instead.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfs4xdr.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index ccaee73de72b..a9827bb8a2f0 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2928,6 +2928,7 @@ struct nfsd4_fattr_args {
 	struct kstat		stat;
 	struct kstatfs		statfs;
 	struct nfs4_acl		*acl;
+	u64			change_attr;
 #ifdef CONFIG_NFSD_V4_SECURITY_LABEL
 	void			*context;
 	int			contextlen;
@@ -3027,7 +3028,6 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
 					 const struct nfsd4_fattr_args *args)
 {
 	const struct svc_export *exp = args->exp;
-	u64 c;
 
 	if (unlikely(exp->ex_flags & NFSEXP_V4ROOT)) {
 		u32 flush_time = convert_to_wallclock(exp->cd->flush_time);
@@ -3038,9 +3038,7 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
 			return nfserr_resource;
 		return nfs_ok;
 	}
-
-	c = nfsd4_change_attribute(&args->stat, d_inode(args->dentry));
-	return nfsd4_encode_changeid4(xdr, c);
+	return nfsd4_encode_changeid4(xdr, args->change_attr);
 }
 
 static __be32 nfsd4_encode_fattr4_size(struct xdr_stream *xdr,
@@ -3562,12 +3560,16 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 	err = vfs_getattr(&path, &args.stat,
 			  STATX_BASIC_STATS | STATX_BTIME | STATX_CHANGE_COOKIE,
 			  AT_STATX_SYNC_AS_STAT);
+	args.change_attr = nfsd4_change_attribute(&args.stat, d_inode(dentry));
 	if (dp) {
 		struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
 
-		if (ncf->ncf_file_modified)
+		if (ncf->ncf_file_modified) {
 			args.stat.size = ncf->ncf_cur_fsize;
-
+			/* If there have been no changes, report the initial cinfo + 1 */
+			if (args.change_attr == ncf->ncf_initial_cinfo)
+				args.change_attr = ncf->ncf_initial_cinfo + 1;
+		}
 		nfs4_put_stid(&dp->dl_stid);
 	}
 	if (err)

-- 
2.46.0