Re: [PATCH 0/6] Simplifications around submit_bio_hook

[David Sterba <dsterba@suse.cz>]

On Wed, Apr 10, 2019 at 05:24:37PM +0300, Nikolay Borisov wrote:
> I've been taking a look at the submit_bio_hook et al  and I saw some
> opportunities for improvement. First I begin by simplifying the definition of 
> submit_bio_hook callback and making one of its arguments explicit. 
> 
> Patch 3 removes a redundant extent_io_tree argument that was passed through 
> several layers of functions and ultimately made it somewhat cumbersome to reason
> what extent_io_tree is being used. 
> 
> Patch 4 and 5 hardcode a 0 being passed  for the bio_offset parameter to
> btrfs_submit_bio_start/btree_submit_bio_start since it only matters for DIO. 
> 
> Patch 6 finally does away with the bio_offset parameter of submit_bio_hook. 
> 
> Here is the output of bloat-o-meter for posterity:
> 
> add/remove: 0/0 grow/shrink: 4/7 up/down: 48/-319 (-271)
> Function                                     old     new   delta
> read_extent_buffer_pages                     784     822     +38
> btrfs_add_ordered_sum                        100     104      +4
> btrfs_submit_bio_hook                        364     367      +3
> btree_submit_bio_hook                        175     178      +3
> end_bio_extent_readpage                     2119    2116      -3
> btrfs_reloc_clone_csums                      272     262     -10
> btrfs_csum_one_bio                          1358    1348     -10
> btree_read_extent_buffer_pages               282     272     -10
> readahead_tree_block                          73      55     -18
> reada_tree_block_flagged                     194     165     -29
> submit_one_bio                               313      74    -239
> Total: Before=1072719, After=1072448, chg -0.03%
> 
> Nikolay Borisov (6):
>   btrfs: Define submit_bio_hook's type directly
>   btrfs: Change submit_bio_hook to taking an inode directly
>   btrfs: Remove 'tree' argument from read_extent_buffer_pages
>   btrfs: Pass 0 for bio_offset to btrfs_wq_submit_bio
>   btrfs: Always pass 0 bio_offset for btree_submit_bio_start
>   btrfs: Remove bio_offset argument from submit_bio_hook

Patchset added to misc-next, thanks.