btrfs: remove the start argument from btrfs_free_reserved_data_space_noquota()

The start argument for btrfs_free_reserved_data_space_noquota() is only
used to make sure the amount of bytes we decrement from the bytes_may_use
counter of the data space_info object is aligned to the filesystem's
sector size. It serves no other purpose.

All its current callers always pass a length argument that is already
aligned to the sector size, so we can make the start argument go away.
In fact its presence makes it impossible to use it in a context where we
just want to free a number of bytes for a range for which either we do
not know its start offset or for freeing multiple ranges at once (which
are not contiguous).

This change is preparatory work for a patch (third patch in this series)
that makes relocation of data block groups that are not full reserve less
data space.

Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6862cd7..07d20f6 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2087,7 +2087,7 @@ void btrfs_clear_delalloc_extent(struct inode *vfs_inode,
 		    (*bits & EXTENT_CLEAR_DATA_RESV))
 			btrfs_free_reserved_data_space_noquota(
 					&inode->vfs_inode,
-					state->start, len);
+					len);
 
 		percpu_counter_add_batch(&fs_info->delalloc_bytes, -len,
 					 fs_info->delalloc_batch);
@@ -7278,8 +7278,7 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map,
 			 * use the existing or preallocated extent, so does not
 			 * need to adjust btrfs_space_info's bytes_may_use.
 			 */
-			btrfs_free_reserved_data_space_noquota(inode, start,
-							       len);
+			btrfs_free_reserved_data_space_noquota(inode, len);
 			goto skip_cow;
 		}
 	}