Re: [PATCH] mm/cma: Add sysfs file 'release_pages_success'

[Andrew Morton]

On Tue,  6 Feb 2024 10:27:31 +0530 Anshuman Khandual <anshuman.khandual@xxxxxxx> wrote:

> This adds the following new sysfs file tracking the number of successfully
> released pages from a given CMA heap area. Also like before - this will be
> available via CONFIG_CMA_SYSFS, and help in determining active CMA pages
> available on the system.

"like before" is mysterious.  Is this referring to some other patch? 
To existing code?  Please be explicit and complete.

> /sys/kernel/mm/cma/<cma-heap-area>/release_pages_success
> 
> It adds an element 'nr_pages_released' (with CONFIG_CMA_SYSFS config) into
> 'struct cma' which gets updated during cma_release().

The changelog doesn't explain why Linux needs this feature.  The value
to our users.  Perhaps that info is buried in the link which is buried
below the ^---$, but as this is the most important part of a changelog,
it really should be spelled out here, completely and carefully please.

> ---
> This patch applies on v6.8-rc3
> 
> Some earlier relevant discussions regarding arm64 MTE dynamic tag storage
> in this regard can be found here.
> 
> https://lore.kernel.org/all/ZbpKyNVHfhf1-AAv@raptor/