nfsd: Properly compare and initialize kuids and kgids

Use uid_eq(uid, GLOBAL_ROOT_UID) instead of !uid.
Use gid_eq(gid, GLOBAL_ROOT_GID) instead of !gid.
Use uid_eq(uid, INVALID_UID) instead of uid == -1
Use gid_eq(uid, INVALID_GID) instead of gid == -1
Use uid = GLOBAL_ROOT_UID instead of uid = 0;
Use gid = GLOBAL_ROOT_GID instead of gid = 0;
Use !uid_eq(uid1, uid2) instead of uid1 != uid2.
Use !gid_eq(gid1, gid2) instead of gid1 != gid2.
Use uid_eq(uid1, uid2) instead of uid1 == uid2.

Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index d586117..31ff1d6 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -401,8 +401,8 @@
 
 	/* Revoke setuid/setgid on chown */
 	if (!S_ISDIR(inode->i_mode) &&
-	    (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) ||
-	     ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid))) {
+	    (((iap->ia_valid & ATTR_UID) && !uid_eq(iap->ia_uid, inode->i_uid)) ||
+	     ((iap->ia_valid & ATTR_GID) && !gid_eq(iap->ia_gid, inode->i_gid)))) {
 		iap->ia_valid |= ATTR_KILL_PRIV;
 		if (iap->ia_valid & ATTR_MODE) {
 			/* we're setting mode too, just clear the s*id bits */
@@ -1205,7 +1205,7 @@
 	 * send along the gid on create when it tries to implement
 	 * setgid directories via NFS:
 	 */
-	if (current_fsuid() != 0)
+	if (!uid_eq(current_fsuid(), GLOBAL_ROOT_UID))
 		iap->ia_valid &= ~(ATTR_UID|ATTR_GID);
 	if (iap->ia_valid)
 		return nfsd_setattr(rqstp, resfhp, iap, 0, (time_t)0);
@@ -2150,7 +2150,7 @@
 	 * with NFSv3.
 	 */
 	if ((acc & NFSD_MAY_OWNER_OVERRIDE) &&
-	    inode->i_uid == current_fsuid())
+	    uid_eq(inode->i_uid, current_fsuid()))
 		return 0;
 
 	/* This assumes  NFSD_MAY_{READ,WRITE,EXEC} == MAY_{READ,WRITE,EXEC} */