NFSD: Change name of extended attribute containing junction

As of fedfs-utils-0.8.0, user space stores all NFS junction
information in a single extended attribute: "trusted.junction.nfs".

Both FedFS and NFS basic junctions are stored in this one attribute,
and the intention is that all future forms of NFS junction metadata
will be stored in this attribute.  Other protocols may use a different
extended attribute.

Thus NFSD needs to look only for that one extended attribute.  The
"trusted.junction.type" xattr is deprecated.  fedfs-utils-0.8.0 will
continue to attach a "trusted.junction.type" xattr to junctions, but
future fedfs-utils releases may no longer do that.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

fs/nfsd/vfs.c

@@ -594,8 +594,19 @@ nfsd4_get_nfs4_acl(struct svc_rqst *rqstp, struct dentry *dentry, struct nfs4_ac
 	return error;
 }
 
-#define NFSD_XATTR_JUNCTION_PREFIX XATTR_TRUSTED_PREFIX "junction."
-#define NFSD_XATTR_JUNCTION_TYPE NFSD_XATTR_JUNCTION_PREFIX "type"
+/*
+ * NFS junction information is stored in an extended attribute.
+ */
+#define NFSD_JUNCTION_XATTR_NAME	XATTR_TRUSTED_PREFIX "junction.nfs"
+
+/**
+ * nfsd4_is_junction - Test if an object could be an NFS junction
+ *
+ * @dentry: object to test
+ *
+ * Returns 1 if "dentry" appears to contain NFS junction information.
+ * Otherwise 0 is returned.
+ */
 int nfsd4_is_junction(struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
@@ -606,7 +617,7 @@ int nfsd4_is_junction(struct dentry *dentry)
 		return 0;
 	if (!(inode->i_mode & S_ISVTX))
 		return 0;
-	if (vfs_getxattr(dentry, NFSD_XATTR_JUNCTION_TYPE, NULL, 0) <= 0)
+	if (vfs_getxattr(dentry, NFSD_JUNCTION_XATTR_NAME, NULL, 0) <= 0)
 		return 0;
 	return 1;
 }