On Thu, 26 Apr 2007 23:41:01 +0530 "Amit K. Arora" [off-list ref] wrote:

+unsigned int ext4_ext_check_overlap(struct inode *inode,
+					struct ext4_extent *newext,
+					struct ext4_ext_path *path)
+{
+	unsigned long b1, b2;
+	unsigned int depth, len1;
+
+	b1 = le32_to_cpu(newext->ee_block);
+	len1 = le16_to_cpu(newext->ee_len);
+	depth = ext_depth(inode);
+	if (!path[depth].p_ext)
+		goto out;
+	b2 = le32_to_cpu(path[depth].p_ext->ee_block);
+
+	/* get the next allocated block if the extent in the path
+	 * is before the requested block(s) */
+	if (b2 < b1) {
+		b2 = ext4_ext_next_allocated_block(path);
+		if (b2 == EXT_MAX_BLOCK)
+			goto out;
+	}
+
+	if (b1 + len1 > b2) {

Are we sure that b1+len cannot wrap through zero here?

+		newext->ee_len = cpu_to_le16(b2 - b1);
+		return 1;
+	}