ocfs2: Fix pos/len passed to ocfs2_write_cluster

This was broken for file systems whose cluster size is greater than page
size. Pos needs to be incremented as we loop through the descriptors, and
len needs to be capped to the size of a single cluster.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/aops.c

@@ -1211,18 +1211,33 @@ static int ocfs2_write_cluster_by_desc(struct address_space *mapping,
 				       loff_t pos, unsigned len)
 {
 	int ret, i;
+	loff_t cluster_off;
+	unsigned int local_len = len;
 	struct ocfs2_write_cluster_desc *desc;
+	struct ocfs2_super *osb = OCFS2_SB(mapping->host->i_sb);
 
 	for (i = 0; i < wc->w_clen; i++) {
 		desc = &wc->w_desc[i];
 
+		/*
+		 * We have to make sure that the total write passed in
+		 * doesn't extend past a single cluster.
+		 */
+		local_len = len;
+		cluster_off = pos & (osb->s_clustersize - 1);
+		if ((cluster_off + local_len) > osb->s_clustersize)
+			local_len = osb->s_clustersize - cluster_off;
+
 		ret = ocfs2_write_cluster(mapping, desc->c_phys,
 					  desc->c_unwritten, data_ac, meta_ac,
-					  wc, desc->c_cpos, pos, len);
+					  wc, desc->c_cpos, pos, local_len);
 		if (ret) {
 			mlog_errno(ret);
 			goto out;
 		}
+
+		len -= local_len;
+		pos += local_len;
 	}
 
 	ret = 0;