On 01.09.25 17:03, David Hildenbrand wrote:
Let's disallow handing out PFN ranges with non-contiguous pages, so we can remove the nth-page usage in __cma_alloc(), and so any callers don't have to worry about that either when wanting to blindly iterate pages.
This is really only a problem in configs with SPARSEMEM but without SPARSEMEM_VMEMMAP, and only when we would cross memory sections in some cases.
Will this cause harm? Probably not, because it's mostly 32bit that does not support SPARSEMEM_VMEMMAP. If this ever becomes a problem we could look into allocating the memmap for the memory sections spanned by a single CMA region in one go from memblock.
Reviewed-by: Alexandru Elisei alexandru.elisei@arm.com Reviewed-by: Lorenzo Stoakes lorenzo.stoakes@oracle.com Signed-off-by: David Hildenbrand david@redhat.com
@Andrew, the following fixup on top. I'm still cross-compiling it, but at the time you read this mail my cross compiles should have been done.
From cbfa2763e1820b917ce3430f45e5f3a55eb2970f Mon Sep 17 00:00:00 2001 From: David Hildenbrand david@redhat.com Date: Tue, 9 Sep 2025 05:50:13 -0400 Subject: [PATCH] fixup: mm/cma: refuse handing out non-contiguous page ranges
Apparently we can have NUMMU configs with SPARSEMEM enabled.
Signed-off-by: David Hildenbrand david@redhat.com --- mm/util.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/util.c b/mm/util.c index 248f877f629b6..6c1d64ed02211 100644 --- a/mm/util.c +++ b/mm/util.c @@ -1306,6 +1306,7 @@ unsigned int folio_pte_batch(struct folio *folio, pte_t *ptep, pte_t pte, { return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr, 0); } +#endif /* CONFIG_MMU */
#if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP) /** @@ -1342,4 +1343,3 @@ bool page_range_contiguous(const struct page *page, unsigned long nr_pages) } EXPORT_SYMBOL(page_range_contiguous); #endif -#endif /* CONFIG_MMU */