address hfs on-disk corruption robustness review comments

Address Roman's review comments for the previously sent on-disk
corruption hfs robustness patch.

- use 0 as a failure value, rather than making a new macro HFS_BAD_KEYLEN,
and use a switch statement instead of if's.

- Add new fail: target to __hfs_brec_find to skip assignments using bad
values when exiting with a failure.

[[e-mail]: coding-style fixes]
Signed-off-by: Eric Sandeen <[e-mail]>
Cc: Roman Zippel <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/hfs/bfind.c

···
 		rec = (e + b) / 2;
 		len = hfs_brec_lenoff(bnode, rec, &off);
 		keylen = hfs_brec_keylen(bnode, rec);
-		if (keylen == HFS_BAD_KEYLEN) {
+		if (keylen == 0) {
 			res = -EINVAL;
-			goto done;
+			goto fail;
 		}
 		hfs_bnode_read(bnode, fd->key, off, keylen);
 		cmpval = bnode->tree->keycmp(fd->key, fd->search_key);
···
 	if (rec != e && e >= 0) {
 		len = hfs_brec_lenoff(bnode, e, &off);
 		keylen = hfs_brec_keylen(bnode, e);
-		if (keylen == HFS_BAD_KEYLEN) {
+		if (keylen == 0) {
 			res = -EINVAL;
-			goto done;
+			goto fail;
 		}
 		hfs_bnode_read(bnode, fd->key, off, keylen);
 	}
···
 	fd->keylength = keylen;
 	fd->entryoffset = off + keylen;
 	fd->entrylength = len - keylen;
+fail:
 	return res;
 }
 
···
 
 	len = hfs_brec_lenoff(bnode, fd->record, &off);
 	keylen = hfs_brec_keylen(bnode, fd->record);
-	if (keylen == HFS_BAD_KEYLEN) {
+	if (keylen == 0) {
 		res = -EINVAL;
 		goto out;
 	}

fs/hfs/brec.c

···
 			if (retval > node->tree->max_key_len + 2) {
 				printk(KERN_ERR "hfs: keylen %d too large\n",
 					retval);
-				retval = HFS_BAD_KEYLEN;
+				retval = 0;
 			}
 		} else {
 			retval = (hfs_bnode_read_u8(node, recoff) | 1) + 1;
 			if (retval > node->tree->max_key_len + 1) {
 				printk(KERN_ERR "hfs: keylen %d too large\n",
 					retval);
-				retval = HFS_BAD_KEYLEN;
+				retval = 0;
 			}
 		}
 	}

fs/hfs/btree.c

···
 		goto fail_page;
 	if (!tree->node_count)
 		goto fail_page;
-	if ((id == HFS_EXT_CNID) && (tree->max_key_len != HFS_MAX_EXT_KEYLEN)) {
-		printk(KERN_ERR "hfs: invalid extent max_key_len %d\n",
-			tree->max_key_len);
-		goto fail_page;
-	}
-	if ((id == HFS_CAT_CNID) && (tree->max_key_len != HFS_MAX_CAT_KEYLEN)) {
-		printk(KERN_ERR "hfs: invalid catalog max_key_len %d\n",
-			tree->max_key_len);
-		goto fail_page;
+	switch (id) {
+	case HFS_EXT_CNID:
+		if (tree->max_key_len != HFS_MAX_EXT_KEYLEN) {
+			printk(KERN_ERR "hfs: invalid extent max_key_len %d\n",
+				tree->max_key_len);
+			goto fail_page;
+		}
+		break;
+	case HFS_CAT_CNID:
+		if (tree->max_key_len != HFS_MAX_CAT_KEYLEN) {
+			printk(KERN_ERR "hfs: invalid catalog max_key_len %d\n",
+				tree->max_key_len);
+			goto fail_page;
+		}
+		break;
+	default:
+		BUG();
 	}
 
 	tree->node_size_shift = ffs(size) - 1;

fs/hfs/hfs.h

···
 #define HFS_MAX_NAMELEN		128
 #define HFS_MAX_VALENCE		32767U
 
-#define HFS_BAD_KEYLEN		0xFF
-
 /* Meanings of the drAtrb field of the MDB,
  * Reference: _Inside Macintosh: Files_ p. 2-61
  */