diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
index a177eae..addd7c5 100644
--- a/fs/ocfs2/alloc.c
+++ b/fs/ocfs2/alloc.c
@@ -7304,13 +7304,24 @@
 
 static int ocfs2_trim_extent(struct super_block *sb,
 			     struct ocfs2_group_desc *gd,
-			     u32 start, u32 count)
+			     u64 group, u32 start, u32 count)
 {
 	u64 discard, bcount;
+	struct ocfs2_super *osb = OCFS2_SB(sb);
 
 	bcount = ocfs2_clusters_to_blocks(sb, count);
-	discard = le64_to_cpu(gd->bg_blkno) +
-			ocfs2_clusters_to_blocks(sb, start);
+	discard = ocfs2_clusters_to_blocks(sb, start);
+
+	/*
+	 * For the first cluster group, the gd->bg_blkno is not at the start
+	 * of the group, but at an offset from the start. If we add it while
+	 * calculating discard for first group, we will wrongly start fstrim a
+	 * few blocks after the desried start block and the range can cross
+	 * over into the next cluster group. So, add it only if this is not
+	 * the first cluster group.
+	 */
+	if (group != osb->first_cluster_group_blkno)
+		discard += le64_to_cpu(gd->bg_blkno);
 
 	trace_ocfs2_trim_extent(sb, (unsigned long long)discard, bcount);
 
@@ -7318,7 +7329,7 @@
 }
 
 static int ocfs2_trim_group(struct super_block *sb,
-			    struct ocfs2_group_desc *gd,
+			    struct ocfs2_group_desc *gd, u64 group,
 			    u32 start, u32 max, u32 minbits)
 {
 	int ret = 0, count = 0, next;
@@ -7337,7 +7348,7 @@
 		next = ocfs2_find_next_bit(bitmap, max, start);
 
 		if ((next - start) >= minbits) {
-			ret = ocfs2_trim_extent(sb, gd,
+			ret = ocfs2_trim_extent(sb, gd, group,
 						start, next - start);
 			if (ret < 0) {
 				mlog_errno(ret);
@@ -7435,7 +7446,8 @@
 		}
 
 		gd = (struct ocfs2_group_desc *)gd_bh->b_data;
-		cnt = ocfs2_trim_group(sb, gd, first_bit, last_bit, minlen);
+		cnt = ocfs2_trim_group(sb, gd, group,
+				       first_bit, last_bit, minlen);
 		brelse(gd_bh);
 		gd_bh = NULL;
 		if (cnt < 0) {