ext4: clean up ext4_match() and callers

When ext4 encryption was originally merged, we were encrypting the
user-specified filename in ext4_match(), introducing a lot of additional
complexity into ext4_match() and its callers.  This has since been
changed to encrypt the filename earlier, so we can remove the gunk
that's no longer needed.  This more or less reverts ext4_search_dir()
and ext4_find_dest_de() to the way they were in the v4.0 kernel.
Signed-off-by: NEric Biggers <ebiggers@google.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/namei.c

@@ -1237,18 +1237,17 @@ static void dx_insert_block(struct dx_frame *frame, u32 hash, ext4_lblk_t block)
 }
 
 /*
- * NOTE! unlike strncmp, ext4_match returns 1 for success, 0 for failure.
+ * Test whether a directory entry matches the filename being searched for.
  *
- * `len <= EXT4_NAME_LEN' is guaranteed by caller.
- * `de != NULL' is guaranteed by caller.
+ * Return: %true if the directory entry matches, otherwise %false.
  */
-static inline int ext4_match(struct ext4_filename *fname,
-			     struct ext4_dir_entry_2 *de)
+static inline bool ext4_match(const struct ext4_filename *fname,
+			      const struct ext4_dir_entry_2 *de)
 {
 	struct fscrypt_name f;
 
 	if (!de->inode)
-		return 0;
+		return false;
 
 	f.usr_fname = fname->usr_fname;
 	f.disk_name = fname->disk_name;
@@ -1269,48 +1268,31 @@ int ext4_search_dir(struct buffer_head *bh, char *search_buf, int buf_size,
 	struct ext4_dir_entry_2 * de;
 	char * dlimit;
 	int de_len;
-	int res;
 
 	de = (struct ext4_dir_entry_2 *)search_buf;
 	dlimit = search_buf + buf_size;
 	while ((char *) de < dlimit) {
 		/* this code is executed quadratically often */
 		/* do minimal checking `by hand' */
-		if ((char *) de + de->name_len <= dlimit) {
-			res = ext4_match(fname, de);
-			if (res < 0) {
-				res = -1;
-				goto return_result;
-			}
-			if (res > 0) {
-				/* found a match - just to be sure, do
-				 * a full check */
-				if (ext4_check_dir_entry(dir, NULL, de, bh,
-						bh->b_data,
-						 bh->b_size, offset)) {
-					res = -1;
-					goto return_result;
-				}
-				*res_dir = de;
-				res = 1;
-				goto return_result;
-			}
-
+		if ((char *) de + de->name_len <= dlimit &&
+		    ext4_match(fname, de)) {
+			/* found a match - just to be sure, do
+			 * a full check */
+			if (ext4_check_dir_entry(dir, NULL, de, bh, bh->b_data,
+						 bh->b_size, offset))
+				return -1;
+			*res_dir = de;
+			return 1;
 		}
 		/* prevent looping on a bad block */
 		de_len = ext4_rec_len_from_disk(de->rec_len,
 						dir->i_sb->s_blocksize);
-		if (de_len <= 0) {
-			res = -1;
-			goto return_result;
-		}
+		if (de_len <= 0)
+			return -1;
 		offset += de_len;
 		de = (struct ext4_dir_entry_2 *) ((char *) de + de_len);
 	}
-
-	res = 0;
-return_result:
-	return res;
+	return 0;
 }
 
 static int is_dx_internal_node(struct inode *dir, ext4_lblk_t block,
@@ -1814,24 +1796,15 @@ int ext4_find_dest_de(struct inode *dir, struct inode *inode,
 	int nlen, rlen;
 	unsigned int offset = 0;
 	char *top;
-	int res;
 
 	de = (struct ext4_dir_entry_2 *)buf;
 	top = buf + buf_size - reclen;
 	while ((char *) de <= top) {
 		if (ext4_check_dir_entry(dir, NULL, de, bh,
-					 buf, buf_size, offset)) {
-			res = -EFSCORRUPTED;
-			goto return_result;
-		}
-		/* Provide crypto context and crypto buffer to ext4 match */
-		res = ext4_match(fname, de);
-		if (res < 0)
-			goto return_result;
-		if (res > 0) {
-			res = -EEXIST;
-			goto return_result;
-		}
+					 buf, buf_size, offset))
+			return -EFSCORRUPTED;
+		if (ext4_match(fname, de))
+			return -EEXIST;
 		nlen = EXT4_DIR_REC_LEN(de->name_len);
 		rlen = ext4_rec_len_from_disk(de->rec_len, buf_size);
 		if ((de->inode ? rlen - nlen : rlen) >= reclen)
@@ -1839,15 +1812,11 @@ int ext4_find_dest_de(struct inode *dir, struct inode *inode,
 		de = (struct ext4_dir_entry_2 *)((char *)de + rlen);
 		offset += rlen;
 	}
-
 	if ((char *) de > top)
-		res = -ENOSPC;
-	else {
-		*dest_de = de;
-		res = 0;
-	}
-return_result:
-	return res;
+		return -ENOSPC;
+
+	*dest_de = de;
+	return 0;
 }
 
 int ext4_insert_dentry(struct inode *dir,