Re: [PATCH v2] mm/hugetlb: allow crashkernel to reuse hugetlb CMA memory

[sashiko-bot@kernel.org]

> crashkernel=size,cma reserves a separate CMA pool. On systems that
> already reserve several gigabytes with hugetlb_cma= (which is common in
> the Meta fleet), the crash kernel cannot use that existing memory as
> part of its working set. With hugetlb_cma=6G, requesting another 2G
> with crashkernel=2G,cma brings the total CMA reservation to 8G, none of
> which can serve unmovable kernel allocations.
> 
> Use existing HugeTLB CMA memory first for crashkernel=size,cma and
> reserve dedicated CMA areas only for the remainder. With hugetlb_cma=6G,
> a 2G request reuses 2G without reserving more CMA. With hugetlb_cma=2G,
> a 4G request reuses 2G and reserves another 2G.
> 
> The full HugeTLB CMA pool remains available to HugeTLB and movable
> allocations during normal operation. After a crash, the capture kernel
> can use the selected ranges as working memory. The conventional
> [ ... ]
> CMA alignment, and report any shortfall. Ignore malformed optional sizes
> and reject requests that would overflow page rounding.
> 
> Suggested-by: Breno Leitao <leitao@debian.org>
> Signed-off-by: Usama Arif <usama.arif@linux.dev>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261106165142.2847916-1-usama.arif@linux.dev?part=1