1 files changed, 55 insertions, 4 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 7aa6ad1f014d..d763457b3cce 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1883,10 +1883,12 @@ static int remove_extent_backref(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
+#define in_range(b, first, len)        ((b) >= (first) && (b) < (first) + (len))
 static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
 			       u64 *discarded_bytes)
 {
-	int ret = 0;
+	int j, ret = 0;
+	u64 bytes_left, end;
 	u64 aligned_start = ALIGN(start, 1 << 9);
 
 	if (WARN_ON(start != aligned_start)) {
@@ -1896,11 +1898,60 @@ static int btrfs_issue_discard(struct block_device *bdev, u64 start, u64 len,
 	}
 
 	*discarded_bytes = 0;
-	if (len) {
-		ret = blkdev_issue_discard(bdev, start >> 9, len >> 9,
+
+	if (!len)
+		return 0;
+
+	end = start + len;
+	bytes_left = len;
+
+	/* Skip any superblocks on this device. */
+	for (j = 0; j < BTRFS_SUPER_MIRROR_MAX; j++) {
+		u64 sb_start = btrfs_sb_offset(j);
+		u64 sb_end = sb_start + BTRFS_SUPER_INFO_SIZE;
+		u64 size = sb_start - start;
+
+		if (!in_range(sb_start, start, bytes_left) &&
+		    !in_range(sb_end, start, bytes_left) &&
+		    !in_range(start, sb_start, BTRFS_SUPER_INFO_SIZE))
+			continue;
+
+		/*
+		 * Superblock spans beginning of range.  Adjust start and
+		 * try again.
+		 */
+		if (sb_start <= start) {
+			start += sb_end - start;
+			if (start > end) {
+				bytes_left = 0;
+				break;
+			}
+			bytes_left = end - start;
+			continue;
+		}
+
+		if (size) {
+			ret = blkdev_issue_discard(bdev, start >> 9, size >> 9,
+						   GFP_NOFS, 0);
+			if (!ret)
+				*discarded_bytes += size;
+			else if (ret != -EOPNOTSUPP)
+				return ret;
+		}
+
+		start = sb_end;
+		if (start > end) {
+			bytes_left = 0;
+			break;
+		}
+		bytes_left = end - start;
+	}
+
+	if (bytes_left) {
+		ret = blkdev_issue_discard(bdev, start >> 9, bytes_left >> 9,
 					   GFP_NOFS, 0);
 		if (!ret)
-			*discarded_bytes = len;
+			*discarded_bytes += bytes_left;
 	}
 	return ret;
 }