Re: [PATCH net-next] page_pool: disable direct recycling based on pool->cpuid on destroy

[Alexander Lobakin]

From: Alexander Lobakin <aleksander.lobakin@xxxxxxxxx>
Date: Thu, 15 Feb 2024 12:39:05 +0100

> Now that direct recycling is performed basing on pool->cpuid when set,
> memory leaks are possible:
> 
> 1. A pool is destroyed.
> 2. Alloc cache is emptied (it's done only once).
> 3. pool->cpuid is still set.
> 4. napi_pp_put_page() does direct recycling basing on pool->cpuid.
> 5. Now alloc cache is not empty, but it won't ever be freed.
> 
> In order to avoid that, rewrite pool->cpuid to -1 when unlinking NAPI to
> make sure no direct recycling will be possible after emptying the cache.
> This involves a bit of overhead as pool->cpuid now must be accessed
> via READ_ONCE() to avoid partial reads.
> Rename page_pool_unlink_napi() -> page_pool_disable_direct_recycling()
> to reflect what it actually does and unexport it.

PW says "Changes requested", but I don't see any in the thread, did I
miss something? :D

Thanks,
Olek