RFC8881, section 10.4.3 has some specific guidance as to how the
delegated change attribute should be handled. We currently don't follow
that guidance properly.

In particular, when the file is modified, the server always reports the
initial change attribute + 1. Section 10.4.3 however indicates that it
should be incremented on every GETATTR request from other clients.

Only request the change attribute until the file has been modified. If
there is an outstanding delegation, then increment the cached change
attribute on every GETATTR.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/nfsd/nfs4callback.c |  8 +++++---
 fs/nfsd/nfs4xdr.c      | 15 +++++++++------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index 3877b53e429fd89899d7dc35086bee8bda6eed07..25acb8624b854f5d0d184efec660e1f72cad8885 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -361,12 +361,14 @@ static void
 encode_cb_getattr4args(struct xdr_stream *xdr, struct nfs4_cb_compound_hdr *hdr,
 			struct nfs4_cb_fattr *fattr)
 {
-	struct nfs4_delegation *dp =
-		container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
+	struct nfs4_delegation *dp = container_of(fattr, struct nfs4_delegation, dl_cb_fattr);
 	struct knfsd_fh *fh = &dp->dl_stid.sc_file->fi_fhandle;
+	struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
 	u32 bmap[1];
 
-	bmap[0] = FATTR4_WORD0_CHANGE | FATTR4_WORD0_SIZE;
+	bmap[0] = FATTR4_WORD0_SIZE;
+	if (!ncf->ncf_file_modified)
+		bmap[0] |= FATTR4_WORD0_CHANGE;
 
 	encode_nfs_cb_opnum4(xdr, OP_CB_GETATTR);
 	encode_nfs_fh4(xdr, fh);
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 53fac037611c05ff8ba2618f9e324a9cb54c3890..c8e8d3f0dff4bb5288186369aad821906e684db7 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2919,6 +2919,7 @@ 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;
@@ -3018,7 +3019,6 @@ 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);
@@ -3029,9 +3029,7 @@ static __be32 nfsd4_encode_fattr4_change(struct xdr_stream *xdr,
 			return nfserr_resource;
 		return nfs_ok;
 	}
-
-	c = nfsd4_change_attribute(&args->stat);
-	return nfsd4_encode_changeid4(xdr, c);
+	return nfsd4_encode_changeid4(xdr, args->change_attr);
 }
 
 static __be32 nfsd4_encode_fattr4_size(struct xdr_stream *xdr,
@@ -3556,11 +3554,16 @@ nfsd4_encode_fattr4(struct svc_rqst *rqstp, struct xdr_stream *xdr,
 	if (dp) {
 		struct nfs4_cb_fattr *ncf = &dp->dl_cb_fattr;
 
-		if (ncf->ncf_file_modified)
+		if (ncf->ncf_file_modified) {
+			++ncf->ncf_initial_cinfo;
 			args.stat.size = ncf->ncf_cur_fsize;
-
+		}
+		args.change_attr = ncf->ncf_initial_cinfo;
 		nfs4_put_stid(&dp->dl_stid);
+	} else {
+		args.change_attr = nfsd4_change_attribute(&args.stat);
 	}
+
 	if (err)
 		goto out_nfserr;
 

-- 
2.47.1