diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 460d440310f2..50cd8a209012 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -855,6 +855,7 @@ static int ocfs2_alloc_write_ctxt(struct ocfs2_write_ctxt **wcp,
 				  struct ocfs2_super *osb, loff_t pos,
 				  unsigned len, struct buffer_head *di_bh)
 {
+	u32 cend;
 	struct ocfs2_write_ctxt *wc;
 
 	wc = kzalloc(sizeof(struct ocfs2_write_ctxt), GFP_NOFS);
@@ -862,7 +863,8 @@ static int ocfs2_alloc_write_ctxt(struct ocfs2_write_ctxt **wcp,
 		return -ENOMEM;
 
 	wc->w_cpos = pos >> osb->s_clustersize_bits;
-	wc->w_clen = ocfs2_clusters_for_bytes(osb->sb, len);
+	cend = (pos + len - 1) >> osb->s_clustersize_bits;
+	wc->w_clen = cend - wc->w_cpos + 1;
 	get_bh(di_bh);
 	wc->w_di_bh = di_bh;