Re: [PATCH v4] md/raid5: fix atomicity violation in raid5_cache_count

On Thu, Feb 1, 2024 at 11:11 PM Yu Kuai yukuai1@huaweicloud.com wrote:

Hi,

在 2024/01/30 15:37, Song Liu 写道:

...

On Thu, Jan 11, 2024 at 11:10 PM Gui-Dong Han 2045gemini@gmail.com wrote:

...

[...]

...

     raid5_release_stripe(sh);

•   conf->max_nr_stripes++;
  

•   WRITE_ONCE(conf->max_nr_stripes, conf->max_nr_stripes + 1);
  

This is weird. We are reading max_nr_stripes without READ_ONCE.

We don't need READ_ONCE() here because writers are protected by 'cache_size_mutex', there are no concurrent writers, it's safe to read 'max_nr_stripes' directly.

OK, that makes sense. Applied to md-6.9.

Thanks, Song