Re: [PATCH mm-unstable hotfix] mm/zswap: fix zswap_pools_lock usages after changing to percpu_ref

[Matthew Wilcox]

On Wed, Feb 28, 2024 at 03:18:32PM +0000, Chengming Zhou wrote:
> Now the release of zswap pool is controlled by percpu_ref, its release
> callback (__zswap_pool_empty()) will be called when percpu_ref hit 0.
> But this release callback may potentially be called from RCU callback
> context by percpu_ref_kill(), which maybe in the interrupt context.
> 
> So we need to use spin_lock_irqsave() and spin_unlock_irqrestore()
> in the release callback: __zswap_pool_empty(). In other task context
> places, spin_lock_irq() and spin_unlock_irq() are enough to avoid
> potential deadlock.

RCU callback context is BH, not IRQ, so it's enough to use
spin_lock_bh(), no?