Re: [PATCH v4 05/10] mm/cma: Allow dynamically creating CMA areas

["David Hildenbrand (Arm)" <david@kernel.org>]

On 8/7/26 17:54, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> There is no technical reason why there should be a limited number of CMA
> regions, so extract some code into helpers and use them to create extra
> functions (cma_create() and cma_free()) that allow creating and freeing,
> respectively, CMA regions dynamically at runtime.
> 
> The static array of CMA areas cannot be replaced by dynamically created
> areas because for many of them, allocation must not fail and some cases
> may need to initialize them before the slab allocator is even available.
> To account for this, keep these "early" areas in a separate list and
> track the dynamic areas in a separate list.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---

Sorry that I didn't get to reply earlier to

	https://lore.kernel.org/all/anS0nxAwCXGWZRl9@orome/

But I am still not convinced why we shouldn't just have a single array that
grows dynamically.

"
After replying to T.J. I think this static array is actually a nice
feature in a way. It allows us to more easily make a distinction between
the regular CMA regions created from reserved-memory regions that
represent classic carveouts, and the more versatile CMA areas that could
be used for any purpose.

Telling the two types apart could obviously also be solved using some
kind of flag stored with the CMA area, but at this point I don't really
see a reason why the two lists would need to be unified.
"

Really, cma_for_each_early_area() + cma_for_each_area() is just nasty.

I'd strongly vote to unify unless there is a very good reason to do it
separately.

-- 
Cheers,

David