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Date: Mon, 29 Apr 2024 21:23:07 +0800
From: Lance Yang <ioworker0@...il.com>
To: akpm@...ux-foundation.org
Cc: willy@...radead.org,
maskray@...gle.com,
ziy@...dia.com,
ryan.roberts@....com,
david@...hat.com,
21cnbao@...il.com,
mhocko@...e.com,
fengwei.yin@...el.com,
zokeefe@...gle.com,
shy828301@...il.com,
xiehuan09@...il.com,
libang.li@...group.com,
wangkefeng.wang@...wei.com,
songmuchun@...edance.com,
peterx@...hat.com,
minchan@...nel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org,
Lance Yang <ioworker0@...il.com>
Subject: [PATCH v3 2/3] mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop
In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
folios, start the pagewalk first, then call split_huge_pmd_address()
to split the folio.
Suggested-by: David Hildenbrand <david@...hat.com>
Signed-off-by: Lance Yang <ioworker0@...il.com>
---
include/linux/huge_mm.h | 2 ++
mm/huge_memory.c | 42 +++++++++++++++++++++--------------------
mm/rmap.c | 26 +++++++++++++++++++------
3 files changed, 44 insertions(+), 26 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index c8d3ec116e29..2daadfcc6776 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -36,6 +36,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr, pgprot_t newprot,
unsigned long cp_flags);
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, bool freeze, struct folio *folio);
vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write);
vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8261b5669397..145505a1dd05 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2584,6 +2584,27 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
pmd_populate(mm, pmd, pgtable);
}
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, bool freeze, struct folio *folio)
+{
+ VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
+ VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
+ VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
+ VM_BUG_ON(freeze && !folio);
+
+ /*
+ * When the caller requests to set up a migration entry, we
+ * require a folio to check the PMD against. Otherwise, there
+ * is a risk of replacing the wrong folio.
+ */
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
+ is_pmd_migration_entry(*pmd)) {
+ if (folio && folio != pmd_folio(*pmd))
+ return;
+ __split_huge_pmd_locked(vma, pmd, address, freeze);
+ }
+}
+
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address, bool freeze, struct folio *folio)
{
@@ -2595,26 +2616,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
(address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
ptl = pmd_lock(vma->vm_mm, pmd);
-
- /*
- * If caller asks to setup a migration entry, we need a folio to check
- * pmd against. Otherwise we can end up replacing wrong folio.
- */
- VM_BUG_ON(freeze && !folio);
- VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
-
- if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
- is_pmd_migration_entry(*pmd)) {
- /*
- * It's safe to call pmd_page when folio is set because it's
- * guaranteed that pmd is present.
- */
- if (folio && folio != pmd_folio(*pmd))
- goto out;
- __split_huge_pmd_locked(vma, pmd, range.start, freeze);
- }
-
-out:
+ split_huge_pmd_locked(vma, range.start, pmd, freeze, folio);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(&range);
}
diff --git a/mm/rmap.c b/mm/rmap.c
index 7e2575d669a9..e42f436c7ff3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1636,9 +1636,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
if (flags & TTU_SYNC)
pvmw.flags = PVMW_SYNC;
- if (flags & TTU_SPLIT_HUGE_PMD)
- split_huge_pmd_address(vma, address, false, folio);
-
/*
* For THP, we have to assume the worse case ie pmd for invalidation.
* For hugetlb, it could be much worse if we need to do pud
@@ -1650,6 +1647,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
range.end = vma_address_end(&pvmw);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address, range.end);
+ if (flags & TTU_SPLIT_HUGE_PMD) {
+ range.start = address & HPAGE_PMD_MASK;
+ range.end = (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
+ }
if (folio_test_hugetlb(folio)) {
/*
* If sharing is possible, start and end will be adjusted
@@ -1664,9 +1665,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
- /* Unexpected PMD-mapped THP? */
- VM_BUG_ON_FOLIO(!pvmw.pte, folio);
-
/*
* If the folio is in an mlock()d vma, we must not swap it out.
*/
@@ -1678,6 +1676,22 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
goto walk_done_err;
}
+ if (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)) {
+ /*
+ * We temporarily have to drop the PTL and start once
+ * again from that now-PTE-mapped page table.
+ */
+ split_huge_pmd_locked(vma, range.start, pvmw.pmd, false,
+ folio);
+ pvmw.pmd = NULL;
+ spin_unlock(pvmw.ptl);
+ flags &= ~TTU_SPLIT_HUGE_PMD;
+ continue;
+ }
+
+ /* Unexpected PMD-mapped THP? */
+ VM_BUG_ON_FOLIO(!pvmw.pte, folio);
+
pfn = pte_pfn(ptep_get(pvmw.pte));
subpage = folio_page(folio, pfn - folio_pfn(folio));
address = pvmw.address;
--
2.33.1
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