NFSD: Update file_hashtbl() helpers

Enable callers to use const pointers for type safety.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>

fs/nfsd/nfs4state.c

@@ -721,7 +721,7 @@ static unsigned int ownerstr_hashval(struct xdr_netobj *ownername)
 #define FILE_HASH_BITS                   8
 #define FILE_HASH_SIZE                  (1 << FILE_HASH_BITS)
 
-static unsigned int file_hashval(struct svc_fh *fh)
+static unsigned int file_hashval(const struct svc_fh *fh)
 {
 	struct inode *inode = d_inode(fh->fh_dentry);
 
@@ -4686,7 +4686,7 @@ move_to_close_lru(struct nfs4_ol_stateid *s, struct net *net)
 
 /* search file_hashtbl[] for file */
 static struct nfs4_file *
-find_file_locked(struct svc_fh *fh, unsigned int hashval)
+find_file_locked(const struct svc_fh *fh, unsigned int hashval)
 {
 	struct nfs4_file *fp;