[PATCH v4] mm,kfence: decouple kfence from page granularity mapping judgement

[Andrew Morton]

On Fri, 10 Mar 2023 17:30:04 +0800 Zhenhua Huang <quic_zhenhuah at quicinc.com> wrote:

> Kfence only needs its pool to be mapped as page granularity, previous
> judgement was a bit over protected. Decouple it from judgement and do
> page granularity mapping for kfence pool only [1].
> 
> To implement this, also relocate the kfence pool allocation before the
> linear mapping setting up, arm64_kfence_alloc_pool is to allocate phys
> addr, __kfence_pool is to be set after linear mapping set up.

Why make this change?  What are the benefits?  What are the user
visible effects?

> LINK: [1] https://lore.kernel.org/linux-arm-kernel/1675750519-1064-1-git-send-email-quic_zhenhuah@quicinc.com/T/

Chasing the links indicates that "page-granular mapping costed more (2M
per 1GB) memory".  Please spell all this out in this patch's changelog.

btw. this format:

Link: https://lore.kernel.org/linux-arm-kernel/1675750519-1064-1-git-send-email-quic_zhenhuah@quicinc.com/T/ [1]

is conventional.