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mm/huge_memory: simplify pgtable deposit detection

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Whether a PMD has a deposited PTE page table only depends on whether the
architecture requires deposits or the VMA is anonymous.

Implement this rule directly in vma_has_deposited_pgtable(), avoiding
mistaking a non-anonymous raw PFN PMD for one with a deposit and
attempting to withdraw a page table that was never deposited.

There is no known in-tree workload that triggers this.  Mostly a
defensive/simplifying change.

Link: https://lore.kernel.org/20260917054015.23553-1-lance.yang@linux.dev
Signed-off-by: Lance Yang <lance.yang@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: David Hildenbrand <david@kernel.org>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Acked-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
This commit is contained in:
Lance Yang 2026-09-17 13:40:15 +08:00 committed by Andrew Morton
parent 37158d8eb8
commit bcf7b0c3a0
1 changed files with 5 additions and 17 deletions
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22
mm/huge_memory.c
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@ -2520,25 +2520,13 @@ static struct folio *normal_or_softleaf_folio_pmd(struct vm_area_struct *vma,
return pmd_to_softleaf_folio(pmdval);
}
static bool has_deposited_pgtable(struct vm_area_struct *vma, pmd_t pmdval,
struct folio *folio)
static bool vma_has_deposited_pgtable(struct vm_area_struct *vma)
{
/* Some architectures require unconditional depositing. */
if (arch_needs_pgtable_deposit())
return true;
/*
* Huge zero always deposited except for DAX which handles itself, see
* set_huge_zero_folio().
* PMDs in anonymous VMAs always have a deposited page table. PMDs in
* other VMAs only have one when required by the architecture.
*/
if (is_huge_zero_pmd(pmdval))
return !vma_is_dax(vma);
/*
* Otherwise, only anonymous folios are deposited, see
* __do_huge_pmd_anonymous_page().
*/
return folio && folio_test_anon(folio);
return arch_needs_pgtable_deposit() || vma_is_anonymous(vma);
}
/**
@ -2578,7 +2566,7 @@ bool zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
is_present = pmd_present(orig_pmd);
folio = normal_or_softleaf_folio_pmd(vma, addr, orig_pmd, is_present);
has_deposit = has_deposited_pgtable(vma, orig_pmd, folio);
has_deposit = vma_has_deposited_pgtable(vma);
if (folio)
zap_huge_pmd_folio(mm, vma, orig_pmd, folio, is_present);
if (has_deposit)