Re: [PATCH] zsmalloc: move LRU update from zs_map_object() to zs_malloc()

[Sergey Senozhatsky <senozhatsky@chromium.org>]

On (23/05/08 09:00), Nhat Pham wrote:
> > The deeper bug here is that zs_map_object() tries to add the page to
> > the LRU list while the shrinker has it isolated for reclaim. This is
> > way too sutble and error prone. Even if it worked now, it'll cause
> > corruption issues down the line.
> >
> > For example, Nhat is adding a secondary entry point to reclaim.
> > Reclaim expects that a page that's on the LRU is also on the fullness
> > list, so this would lead to a double remove_zspage() and BUG_ON().
> >
> > This patch doesn't just fix the crash, it eliminates the deeper LRU
> > isolation issue and makes the code more robust and simple.
> 
> I agree. IMO, less unnecessary concurrent interaction is always a
> win for developers' and maintainers' cognitive load.

Thanks for all the explanations.

> As a side benefit - this also gets rid of the inelegant check
> (mm == ZS_MM_WO). The fact that we had to include a
> a multi-paragraph explanation for a 3-line piece of code
> should have been a red flag.

Minchan had some strong opinion on that, so we need to hear from him
before we decide how do we fix it.