Re: [PATCH] zsmalloc: do not use bit_spin_lock

[Vitaly Wool]

On Sun, Dec 20, 2020 at 2:18 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote:
>
> On Sun, Dec 20, 2020 at 02:22:28AM +0200, Vitaly Wool wrote:
> > zsmalloc takes bit spinlock in its _map() callback and releases it
> > only in unmap() which is unsafe and leads to zswap complaining
> > about scheduling in atomic context.
> >
> > To fix that and to improve RT properties of zsmalloc, remove that
> > bit spinlock completely and use a bit flag instead.
>
> Isn't this just "I open coded bit spinlock to make the lockdep
> warnings go away"?

Not really because bit spinlock leaves preemption disabled.