linux-kernel - Re: [PATCH v5 00/15] md/md-bitmap: introduce CONFIG_MD

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Message-ID: <CALTww2_nfqeoR+h6rLCtCvr3Gh-b-tqpDhg4QimaZcC9AbUsnA@mail.gmail.com>
Date: Mon, 28 Jul 2025 13:37:32 +0800
From: Xiao Ni <xni@...hat.com>
To: Yu Kuai <yukuai1@...weicloud.com>
Cc: agk@...hat.com, snitzer@...nel.org, mpatocka@...hat.com, song@...nel.org, 
	yukuai3@...wei.com, dm-devel@...ts.linux.dev, linux-raid@...r.kernel.org, 
	linux-kernel@...r.kernel.org, yi.zhang@...wei.com, yangerkun@...wei.com, 
	johnny.chenyi@...wei.com
Subject: Re: [PATCH v5 00/15] md/md-bitmap: introduce CONFIG_MD_BITMAP

On Mon, Jul 7, 2025 at 9:36 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> From: Yu Kuai <yukuai3@...wei.com>
>
> Changes in v5:
>  - rebase on the top of md-6.17;
>  - fix compile problem if md-mod is build as module;
>  - fix two problems for lvm2 dm-raid tests, patch 5,13
>  - other cleanups;
> Changes in v4:
>  - rebase on the top of other patchset;
> Changes in v3:
>  - update commit message.
> Changes in v2:
>  - don't export apis, and don't support build md-bitmap as module
>
> Due to known performance issues with md-bitmap and the unreasonable
> implementations like following:
>
>  - self-managed pages, bitmap_storage->filemap;
>  - self-managed IO submitting like filemap_write_page();
>  - global spin_lock
>  ...
>
> I have decided not to continue optimizing based on the current bitmap
> implementation, and plan to invent a new lock-less bitmap. And a new
> kconfig option is a good way for isolation.
>
> However, we still encourage anyone who wants to continue optimizing the
> current implementation
>
> Yu Kuai (15):
>   md/raid1: change r1conf->r1bio_pool to a pointer type
>   md/raid1: remove struct pool_info and related code
>   md/md-bitmap: remove the parameter 'init' for bitmap_ops->resize()
>   md/md-bitmap: merge md_bitmap_group into bitmap_operations
>   md/md-bitmap: add a new parameter 'flush' to bitmap_ops->enabled
>   md/md-bitmap: add md_bitmap_registered/enabled() helper
>   md/md-bitmap: handle the case bitmap is not enabled before
>     start_sync()
>   md/md-bitmap: handle the case bitmap is not enabled before end_sync()
>   md/raid1: check bitmap before behind write
>   md/raid1: check before referencing mddev->bitmap_ops
>   md/raid10: check before referencing mddev->bitmap_ops
>   md/raid5: check before referencing mddev->bitmap_ops
>   md/dm-raid: check before referencing mddev->bitmap_ops
>   md: check before referencing mddev->bitmap_ops
>   md/md-bitmap: introduce CONFIG_MD_BITMAP
>
>  drivers/md/Kconfig      |  18 +++++
>  drivers/md/Makefile     |   3 +-
>  drivers/md/dm-raid.c    |  18 +++--
>  drivers/md/md-bitmap.c  |  74 +++++++++---------
>  drivers/md/md-bitmap.h  |  62 ++++++++++++++-
>  drivers/md/md-cluster.c |   2 +-
>  drivers/md/md.c         | 112 +++++++++++++++++++--------
>  drivers/md/md.h         |   4 +-
>  drivers/md/raid1-10.c   |   2 +-
>  drivers/md/raid1.c      | 163 +++++++++++++++++++---------------------
>  drivers/md/raid1.h      |  22 +-----
>  drivers/md/raid10.c     |  49 ++++++------
>  drivers/md/raid5.c      |  30 ++++----
>  13 files changed, 330 insertions(+), 229 deletions(-)
>
> --
> 2.39.2
>
>

The patch set looks good to me.
Reviewed-by: Xiao Ni <xni@...hat.com>