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/auth.c b/fs/nfsd/auth.c
index 4d6642b..06cddd5 100644
--- a/fs/nfsd/auth.c
+++ b/fs/nfsd/auth.c
@@ -47,9 +47,9 @@
 		if (!gi)
 			goto oom;
 	} else if (flags & NFSEXP_ROOTSQUASH) {
-		if (!new->fsuid)
+		if (uid_eq(new->fsuid, GLOBAL_ROOT_UID))
 			new->fsuid = exp->ex_anon_uid;
-		if (!new->fsgid)
+		if (gid_eq(new->fsgid, GLOBAL_ROOT_GID))
 			new->fsgid = exp->ex_anon_gid;
 
 		gi = groups_alloc(rqgi->ngroups);
@@ -66,9 +66,9 @@
 		gi = get_group_info(rqgi);
 	}
 
-	if (new->fsuid == (uid_t) -1)
+	if (uid_eq(new->fsuid, INVALID_UID))
 		new->fsuid = exp->ex_anon_uid;
-	if (new->fsgid == (gid_t) -1)
+	if (gid_eq(new->fsgid, INVALID_GID))
 		new->fsgid = exp->ex_anon_gid;
 
 	ret = set_groups(new, gi);
@@ -76,7 +76,7 @@
 	if (ret < 0)
 		goto error;
 
-	if (new->fsuid)
+	if (!uid_eq(new->fsuid, GLOBAL_ROOT_UID))
 		new->cap_effective = cap_drop_nfsd_set(new->cap_effective);
 	else
 		new->cap_effective = cap_raise_nfsd_set(new->cap_effective,