[PATCH] kNFSd: NFSv4: allow resfh==fhp in fh_compose()

Change fh_compose() so that it will do the right thing if fhp==res_fh.
(This is convenient in the NFSv4 LOOKUP operation, which _replaces_
CURRENT_FH with the filehandle obtained by lookup.)

This requires extracting the interesting parts of the reference
filehandle first, then calling fh_put if it is a re-use.

fs/nfsd/nfsfh.c

@@ -317,6 +317,8 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry, st
 	 *
 	 */
 
+	u8 ref_fh_version = 0;
+	u8 ref_fh_fsid_type = 0;
 	struct inode * inode = dentry->d_inode;
 	struct dentry *parent = dentry->d_parent;
 	__u32 *datap;
@@ -326,6 +328,13 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry, st
 		parent->d_name.name, dentry->d_name.name,
 		(inode ? inode->i_ino : 0));
 
+	if (ref_fh) {
+		ref_fh_version = ref_fh->fh_handle.fh_version;
+		ref_fh_fsid_type = ref_fh->fh_handle.fh_fsid_type;
+		if (ref_fh == fhp)
+			fh_put(ref_fh);
+	}
+
 	if (fhp->fh_locked || fhp->fh_dentry) {
 		printk(KERN_ERR "fh_compose: fh %s/%s not initialized!\n",
 			parent->d_name.name, dentry->d_name.name);
@@ -337,8 +346,7 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry, st
 	fhp->fh_dentry = dentry; /* our internal copy */
 	fhp->fh_export = exp;
 
-	if (ref_fh &&
-	    ref_fh->fh_handle.fh_version == 0xca) {
+	if (ref_fh_version == 0xca) {
 		/* old style filehandle please */
 		memset(&fhp->fh_handle.fh_base, 0, NFS_FHSIZE);
 		fhp->fh_handle.fh_size = NFS_FHSIZE;
@@ -354,7 +362,7 @@ fh_compose(struct svc_fh *fhp, struct svc_export *exp, struct dentry *dentry, st
 		fhp->fh_handle.fh_auth_type = 0;
 		datap = fhp->fh_handle.fh_auth+0;
 		if ((exp->ex_flags & NFSEXP_FSID) &&
-		    (!ref_fh || ref_fh->fh_handle.fh_fsid_type == 1)) {
+		    (ref_fh_fsid_type == 1)) {
 			fhp->fh_handle.fh_fsid_type = 1;
 			/* fsid_type 1 == 4 bytes filesystem id */
 			*datap++ = exp->ex_fsid;