untangling do_lookup() - get rid of need_reval in !dentry case

Everything arriving into if (!dentry) will have need_reval = 1.
Indeed, the only way to get there with need_reval reset to 0 would
be via
	if (unlikely(d_need_lookup(dentry)))
		goto unlazy;
	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
		status = d_revalidate(dentry, nd);
	if (unlikely(status <= 0)) {
		if (status != -ECHILD)
			need_reval = 0;
		goto unlazy;
...
unlazy:
	/* no assignments to dentry */
	if (dentry && unlikely(d_need_lookup(dentry))) {
		dput(dentry);
		dentry = NULL;
	}
and if d_need_lookup() had already been false the first time around, it
will remain false on the second call as well.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -1181,7 +1181,6 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
 				return PTR_ERR(dentry);
 			}
 			/* known good */
-			need_reval = 0;
 			status = 1;
 		} else if (unlikely(d_need_lookup(dentry))) {
 			dentry = d_inode_lookup(parent, dentry, nd);
@@ -1190,10 +1189,8 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
 				return PTR_ERR(dentry);
 			}
 			/* known good */
-			need_reval = 0;
 			status = 1;
-		}
-		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
+		} else if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE))
 			status = d_revalidate(dentry, nd);
 		if (unlikely(status <= 0)) {
 			if (status < 0) {
@@ -1209,7 +1206,6 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
 					return PTR_ERR(dentry);
 				}
 				/* known good */
-				need_reval = 0;
 				status = 1;
 			}
 		}
@@ -1226,7 +1222,6 @@ static int do_lookup(struct nameidata *nd, struct qstr *name,
 		if (!d_invalidate(dentry)) {
 			dput(dentry);
 			dentry = NULL;
-			need_reval = 1;
 			goto retry;
 		}
 	}