Re: [PATCH RFC -next v2 00/41] md/md-bitmap: introduce bitmap_operations and make structure internel

[Su Yue <l@damenly.org>]

On Wed 14 Aug 2024 at 15:10, Yu Kuai <yukuai1@huaweicloud.com> 
wrote:

> From: Yu Kuai <yukuai3@huawei.com>
>
> Changes in v2:
>  - add patch 1-8 to prevent dereference bitmap directly, and the 
>  last
>  patch to make bitmap structure internel.
>  - use plain function alls "bitmap_ops->xxx()" directly;
>
> The background is that currently bitmap is using a global 
> spin_lock,
> cauing lock contention and huge IO performance degration for all 
> raid
> levels.
>
> However, it's impossible to implement a new lock free bitmap 
> with
> current situation that md-bitmap exposes the internal 
> implementation
> with lots of exported apis. Hence bitmap_operations is invented, 
> to
> describe bitmap core implementation, and a new bitmap can be 
> introduced
> with a new bitmap_operations, we only need to switch to the new 
> one
> during initialization.
>
Is the new bitmap in plan?
>
> And with this we can build bitmap as kernel module, but that's 
> not
> our concern for now.
>
> Noted I just compile this patchset, not tested yet.
>

I've looked through the patchset almostly. The changes are quite
straightforward. IMO, it's good timing to  test it and drop RFC in 
next
version.

> Yu Kuai (41):
>   md/raid1: use md_bitmap_wait_behind_writes() in 
>   raid1_read_request()
>   md/md-bitmap: replace md_bitmap_status() with a new helper
>     md_bitmap_get_stats()
>   md: use new helper md_bitmap_get_stats() in 
>   update_array_info()
>   md/md-bitmap: add 'events_cleared' into struct md_bitmap_stats
>   md/md-bitmap: add 'sync_size' into struct md_bitmap_stats
>   md/md-bitmap: add 'file_pages' into struct md_bitmap_stats
>   md/md-bitmap: add 'behind_writes' and 'behind_wait' into 
>   struct
>     md_bitmap_stats
>   md/md-cluster: use helper md_bitmap_get_stats() to get pages 
>   in
>     resize_bitmaps()
>   md/md-bitmap: add a new helper md_bitmap_set_pages()
>   md/md-bitmap: introduce struct bitmap_operations
>   md/md-bitmap: simplify md_bitmap_create() + md_bitmap_load()
>   md/md-bitmap: merge md_bitmap_create() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_load() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_destroy() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_flush() into bitmap_operations
>   md/md-bitmap: make md_bitmap_print_sb() internal
>   md/md-bitmap: merge md_bitmap_update_sb() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_status() into bitmap_operations
>   md/md-bitmap: remove md_bitmap_setallbits()
>   md/md-bitmap: merge bitmap_write_all() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_dirty_bits() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_startwrite() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_endwrite() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_start_sync() into 
>   bitmap_operations
>   md/md-bitmap: remove the parameter 'aborted' for 
>   md_bitmap_end_sync()
>   md/md-bitmap: merge md_bitmap_end_sync() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_close_sync() into 
>   bitmap_operations
>   md/md-bitmap: mrege md_bitmap_cond_end_sync() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_sync_with_cluster() into
>     bitmap_operations
>   md/md-bitmap: merge md_bitmap_unplug_async() into 
>   md_bitmap_unplug()
>   md/md-bitmap: merge bitmap_unplug() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_daemon_work() into 
>   bitmap_operations
>   md/md-bitmap: pass in mddev directly for md_bitmap_resize()
>   md/md-bitmap: merge md_bitmap_resize() into bitmap_operations
>   md/md-bitmap: merge get_bitmap_from_slot() into 
>   bitmap_operations
>   md/md-bitmap: merge md_bitmap_copy_from_slot() into struct
>     bitmap_operation.
>   md/md-bitmap: merge md_bitmap_set_pages() into struct
>     bitmap_operations
>   md/md-bitmap: merge md_bitmap_free() into bitmap_operations
>   md/md-bitmap: merge md_bitmap_wait_behind_writes() into
>     bitmap_operations
>   md/md-bitmap: merge md_bitmap_enabled() into bitmap_operations
>   md/md-bitmap: make in memory structure internal
>
>  drivers/md/dm-raid.c     |   7 +-
>  drivers/md/md-bitmap.c   | 561 
>  +++++++++++++++++++++++++++++----------
>  drivers/md/md-bitmap.h   | 272 ++++---------------
>  drivers/md/md-cluster.c  |  79 +++---
>  drivers/md/md.c          | 133 ++++++----
>  drivers/md/md.h          |   3 +-
>  drivers/md/raid1-10.c    |   9 +-
>  drivers/md/raid1.c       |  78 +++---
>  drivers/md/raid10.c      |  73 ++---
>  drivers/md/raid5-cache.c |   8 +-
>  drivers/md/raid5.c       |  62 ++---
>  11 files changed, 731 insertions(+), 554 deletions(-)