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>

fs/btrfs/delalloc-space.c

@@ -255,7 +255,7 @@ int btrfs_check_data_free_space(struct inode *inode,
 	/* Use new btrfs_qgroup_reserve_data to reserve precious data space. */
 	ret = btrfs_qgroup_reserve_data(inode, reserved, start, len);
 	if (ret < 0)
-		btrfs_free_reserved_data_space_noquota(inode, start, len);
+		btrfs_free_reserved_data_space_noquota(inode, len);
 	else
 		ret = 0;
 	return ret;
@@ -269,16 +269,13 @@ int btrfs_check_data_free_space(struct inode *inode,
  * which we can't sleep and is sure it won't affect qgroup reserved space.
  * Like clear_bit_hook().
  */
-void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
+void btrfs_free_reserved_data_space_noquota(struct inode *inode,
 					    u64 len)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	struct btrfs_space_info *data_sinfo;
 
-	/* Make sure the range is aligned to sectorsize */
-	len = round_up(start + len, fs_info->sectorsize) -
-	      round_down(start, fs_info->sectorsize);
-	start = round_down(start, fs_info->sectorsize);
+	ASSERT(IS_ALIGNED(len, fs_info->sectorsize));
 
 	data_sinfo = fs_info->data_sinfo;
 	spin_lock(&data_sinfo->lock);
@@ -303,7 +300,7 @@ void btrfs_free_reserved_data_space(struct inode *inode,
 	      round_down(start, root->fs_info->sectorsize);
 	start = round_down(start, root->fs_info->sectorsize);
 
-	btrfs_free_reserved_data_space_noquota(inode, start, len);
+	btrfs_free_reserved_data_space_noquota(inode, len);
 	btrfs_qgroup_free_data(inode, reserved, start, len);
 }
 

fs/btrfs/delalloc-space.h

@@ -13,7 +13,7 @@ void btrfs_free_reserved_data_space(struct inode *inode,
 void btrfs_delalloc_release_space(struct inode *inode,
 				  struct extent_changeset *reserved,
 				  u64 start, u64 len, bool qgroup_free);
-void btrfs_free_reserved_data_space_noquota(struct inode *inode, u64 start,
+void btrfs_free_reserved_data_space_noquota(struct inode *inode,
 					    u64 len);
 void btrfs_delalloc_release_metadata(struct btrfs_inode *inode, u64 num_bytes,
 				     bool qgroup_free);

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;
 		}
 	}