merging pick_link() with get_link(), part 3

After a pure jump ("/" or procfs-style symlink) we don't need to
hold the link anymore.  link_path_walk() dropped it if such case
had been detected, lookup_last/do_last() (i.e. old trailing_symlink())
left it on the stack - it ended up calling terminate_walk() shortly
anyway, which would've purged the entire stack.

Do it in get_link() itself instead.  Simpler logics that way...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -1154,7 +1154,9 @@ const char *get_link(struct nameidata *nd)
 		} else {
 			res = get(dentry, inode, &last->done);
 		}
-		if (IS_ERR_OR_NULL(res))
+		if (!res)
+			goto all_done;
+		if (IS_ERR(res))
 			return res;
 	}
 	if (*res == '/') {
@@ -1164,9 +1166,11 @@ const char *get_link(struct nameidata *nd)
 		while (unlikely(*++res == '/'))
 			;
 	}
-	if (!*res)
-		res = NULL;
-	return res;
+	if (*res)
+		return res;
+all_done: // pure jump
+	put_link(nd);
+	return NULL;
 }
 
 /*
@@ -2211,11 +2215,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 
 			if (IS_ERR(s))
 				return PTR_ERR(s);
-			err = 0;
-			if (unlikely(!s)) {
-				/* jumped */
-				put_link(nd);
-			} else {
+			if (likely(s)) {
 				nd->stack[nd->depth - 1].name = name;
 				name = s;
 				continue;