[PATCH v2 4/5] NFSD: Name the fh_maxsize value that carries no NFS version

nfsd_set_fh_dentry() selects behavior specific to an NFS protocol
version by matching fh_maxsize against NFS_FHSIZE, NFS3_FHSIZE, or
NFS4_FHSIZE. A filehandle that reaches NFSD outside an NFS request has
no such version. nlm_fopen() opts out of the switch by passing a bare
0, which matches no arm, and the literal says nothing about why, so an
adjacent comment has to carry it.

Signed-off-by: Chuck Lever <[email protected]>
---
 fs/nfsd/lockd.c |  3 +--
 fs/nfsd/nfsfh.c |  2 ++
 fs/nfsd/nfsfh.h | 14 ++++++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/lockd.c b/fs/nfsd/lockd.c
index f5a4f352f8ab..5ec0f5456063 100644
--- a/fs/nfsd/lockd.c
+++ b/fs/nfsd/lockd.c
@@ -34,8 +34,7 @@ static int nlm_fopen(struct svc_rqst *rqstp, struct nfs_fh *f,
 	int		access;
 	struct svc_fh	fh;
 
-	/* must initialize before using! but maxsize doesn't matter */
-	fh_init(&fh,0);
+	fh_init(&fh, NFSD_FHSIZE_UNSPEC);
 	fh.fh_handle.fh_size = f->size;
 	memcpy(&fh.fh_handle.fh_raw, f->data, f->size);
 	fh.fh_export = NULL;
diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
index fd721a5a6b37..b1f3c22af525 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -335,6 +335,8 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net,
 	}
 
 	switch (fhp->fh_maxsize) {
+	case NFSD_FHSIZE_UNSPEC:
+		break;
 	case NFS4_FHSIZE:
 		if (dentry->d_sb->s_export_op->flags & EXPORT_OP_NOATOMIC_ATTR)
 			fhp->fh_no_atomic_attr = true;
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index ab15b59ac7b3..7d8e3f015307 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -246,6 +246,20 @@ fh_copy_shallow(struct knfsd_fh *dst, const struct knfsd_fh *src)
 	memcpy(&dst->fh_raw, &src->fh_raw, src->fh_size);
 }
 
+#define NFSD_FHSIZE_UNSPEC	0
+
+/**
+ * fh_init - Prepare a file handle for fh_compose() or fh_verify()
+ * @fhp: File handle to initialize
+ * @maxsize: Largest file handle, in bytes, to build in @fhp
+ *
+ * @maxsize bounds the handle fh_compose() may build: NFS_FHSIZE,
+ * NFS3_FHSIZE, and NFS4_FHSIZE additionally select version-specific
+ * handling in fh_verify(). Callers that only verify an incoming
+ * handle pass NFSD_FHSIZE_UNSPEC, which cannot be composed.
+ *
+ * Return: @fhp
+ */
 static __inline__ struct svc_fh *
 fh_init(struct svc_fh *fhp, int maxsize)
 {
-- 
2.54.0