romfs_lookup: switch to d_splice_alias()

... and hash negative lookups
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/romfs/super.c

@@ -213,7 +213,7 @@ static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 				   unsigned int flags)
 {
 	unsigned long offset, maxoff;
-	struct inode *inode;
+	struct inode *inode = NULL;
 	struct romfs_inode ri;
 	const char *name;		/* got from dentry */
 	int len, ret;
@@ -233,7 +233,7 @@ static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 
 	for (;;) {
 		if (!offset || offset >= maxoff)
-			goto out0;
+			break;
 
 		ret = romfs_dev_read(dir->i_sb, offset, &ri, sizeof(ri));
 		if (ret < 0)
@@ -244,37 +244,19 @@ static struct dentry *romfs_lookup(struct inode *dir, struct dentry *dentry,
 				       len);
 		if (ret < 0)
 			goto error;
-		if (ret == 1)
-			break;
-
-		/* next entry */
-		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
-	}
-
+		if (ret == 1) {
 			/* Hard link handling */
 			if ((be32_to_cpu(ri.next) & ROMFH_TYPE) == ROMFH_HRD)
 				offset = be32_to_cpu(ri.spec) & ROMFH_MASK;
-
 			inode = romfs_iget(dir->i_sb, offset);
-	if (IS_ERR(inode)) {
-		ret = PTR_ERR(inode);
-		goto error;
+			break;
 		}
-	goto outi;
 
-	/*
-	 * it's a bit funky, _lookup needs to return an error code
-	 * (negative) or a NULL, both as a dentry.  ENOENT should not
-	 * be returned, instead we need to create a negative dentry by
-	 * d_add(dentry, NULL); and return 0 as no error.
-	 * (Although as I see, it only matters on writable file
-	 * systems).
-	 */
-out0:
-	inode = NULL;
-outi:
-	d_add(dentry, inode);
-	ret = 0;
+		/* next entry */
+		offset = be32_to_cpu(ri.next) & ROMFH_MASK;
+	}
+
+	return d_splice_alias(inode, dentry);
 error:
 	return ERR_PTR(ret);
 }