btrfs: remove unused sectorsize member

The sectorsize member of btrfs_block_group_cache is unused. So remove it, this
reduces the number of holes in the struct.

With patch:
/* size: 856, cachelines: 14, members: 40 */
/* sum members: 837, holes: 4, sum holes: 19 */
/* bit holes: 1, sum bit holes: 29 bits */
/* last cacheline: 24 bytes */

Without patch:
/* size: 864, cachelines: 14, members: 41 */
/* sum members: 841, holes: 5, sum holes: 23 */
/* bit holes: 1, sum bit holes: 29 bits */
/* last cacheline: 32 bytes */

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ctree.h

@@ -558,7 +558,6 @@ struct btrfs_block_group_cache {
 	u64 bytes_super;
 	u64 flags;
 	u64 cache_generation;
-	u32 sectorsize;
 
 	/*
 	 * If the free space extent count exceeds this number, convert the block

fs/btrfs/extent-tree.c

@@ -9952,7 +9952,6 @@ btrfs_create_block_group_cache(struct btrfs_fs_info *fs_info,
 	cache->key.offset = size;
 	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
 
-	cache->sectorsize = fs_info->sectorsize;
 	cache->fs_info = fs_info;
 	cache->full_stripe_len = btrfs_full_stripe_len(fs_info,
 						       &fs_info->mapping_tree,

fs/btrfs/tests/btrfs-tests.c

@@ -211,7 +211,6 @@ btrfs_alloc_dummy_block_group(struct btrfs_fs_info *fs_info,
 	cache->key.objectid = 0;
 	cache->key.offset = length;
 	cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
-	cache->sectorsize = fs_info->sectorsize;
 	cache->full_stripe_len = fs_info->sectorsize;
 	cache->fs_info = fs_info;
 

fs/btrfs/tests/free-space-tree-tests.c

@@ -81,7 +81,7 @@ static int __check_free_space_extents(struct btrfs_trans_handle *trans,
 					i++;
 				}
 				prev_bit = bit;
-				offset += cache->sectorsize;
+				offset += fs_info->sectorsize;
 			}
 		}
 		if (prev_bit == 1) {