Btrfs: use ctl->unit for free space calculation instead of block_group->sectorsize

We should use ctl->unit for free space calculation instead of block_group->sectorsize
even though for free space use_bitmap or free space cluster we only have sectorsize assigned to ctl->unit currently. Also, we can keep it consisten in code style.
Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/free-space-cache.c

@@ -1353,7 +1353,7 @@ static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
 	u64 bitmap_bytes;
 	u64 extent_bytes;
 	u64 size = block_group->key.offset;
-	u64 bytes_per_bg = BITS_PER_BITMAP * block_group->sectorsize;
+	u64 bytes_per_bg = BITS_PER_BITMAP * ctl->unit;
 	int max_bitmaps = div64_u64(size + bytes_per_bg - 1, bytes_per_bg);
 
 	BUG_ON(ctl->total_bitmaps > max_bitmaps);
@@ -1639,8 +1639,7 @@ static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
 	 * some block groups are so tiny they can't be enveloped by a bitmap, so
 	 * don't even bother to create a bitmap for this
 	 */
-	if (BITS_PER_BITMAP * block_group->sectorsize >
-	    block_group->key.offset)
+	if (BITS_PER_BITMAP * ctl->unit > block_group->key.offset)
 		return false;
 
 	return true;
@@ -2287,10 +2286,10 @@ static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
 	unsigned long total_found = 0;
 	int ret;
 
-	i = offset_to_bit(entry->offset, block_group->sectorsize,
+	i = offset_to_bit(entry->offset, ctl->unit,
 			  max_t(u64, offset, entry->offset));
-	want_bits = bytes_to_bits(bytes, block_group->sectorsize);
-	min_bits = bytes_to_bits(min_bytes, block_group->sectorsize);
+	want_bits = bytes_to_bits(bytes, ctl->unit);
+	min_bits = bytes_to_bits(min_bytes, ctl->unit);
 
 again:
 	found_bits = 0;
@@ -2314,23 +2313,22 @@ static int btrfs_bitmap_cluster(struct btrfs_block_group_cache *block_group,
 
 	total_found += found_bits;
 
-	if (cluster->max_size < found_bits * block_group->sectorsize)
-		cluster->max_size = found_bits * block_group->sectorsize;
+	if (cluster->max_size < found_bits * ctl->unit)
+		cluster->max_size = found_bits * ctl->unit;
 
 	if (total_found < want_bits || cluster->max_size < cont1_bytes) {
 		i = next_zero + 1;
 		goto again;
 	}
 
-	cluster->window_start = start * block_group->sectorsize +
-		entry->offset;
+	cluster->window_start = start * ctl->unit + entry->offset;
 	rb_erase(&entry->offset_index, &ctl->free_space_offset);
 	ret = tree_insert_offset(&cluster->root, entry->offset,
 				 &entry->offset_index, 1);
 	BUG_ON(ret); /* -EEXIST; Logic error */
 
 	trace_btrfs_setup_cluster(block_group, cluster,
-				  total_found * block_group->sectorsize, 1);
+				  total_found * ctl->unit, 1);
 	return 0;
 }