Re: [PATCH RFC -next 00/26] md/md-bitmap: introduce bitmap_operations

[Christoph Hellwig <hch@infradead.org>]

On Sat, Aug 10, 2024 at 10:08:28AM +0800, Yu Kuai wrote:
> From: Yu Kuai <yukuai3@huawei.com>
> 
> 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.
> 
> 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.

Refactoring the bitmap code to be modular seems like a good idea.

But I'd just turn this into plain function calls and maybe a hidden
data structure if you feel really fancy.  No need to introduce expensive
indirect calls and a separate module.