mm-rmap-fix-cont-pte-pmd-size-hugetlb-issue-when-migration.patch removed from -mm tree
The quilt patch titled
Subject: mm: rmap: fix CONT-PTE/PMD size hugetlb issue when migration
has been removed from the -mm tree. Its filename was
mm-rmap-fix-cont-pte-pmd-size-hugetlb-issue-when-migration.patch
This patch was dropped because it was merged into the mm-stable branch\nof git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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From: Baolin Wang <[email protected]>
Subject: mm: rmap: fix CONT-PTE/PMD size hugetlb issue when migration
On some architectures (like ARM64), it can support CONT-PTE/PMD size hugetlb, which means it can support not only PMD/PUD size hugetlb: 2M and 1G, but also CONT-PTE/PMD size: 64K and 32M if a 4K page size specified.
When migrating a hugetlb page, we will get the relevant page table entry by huge_pte_offset() only once to nuke it and remap it with a migration pte entry. This is correct for PMD or PUD size hugetlb, since they always contain only one pmd entry or pud entry in the page table.
However this is incorrect for CONT-PTE and CONT-PMD size hugetlb, since they can contain several continuous pte or pmd entry with same page table attributes. So we will nuke or remap only one pte or pmd entry for this CONT-PTE/PMD size hugetlb page, which is not expected for hugetlb migration. The problem is we can still continue to modify the subpages' data of a hugetlb page during migrating a hugetlb page, which can cause a serious data consistent issue, since we did not nuke the page table entry and set a migration pte for the subpages of a hugetlb page.
To fix this issue, we should change to use huge_ptep_clear_flush() to nuke a hugetlb page table, and remap it with set_huge_pte_at() and set_huge_swap_pte_at() when migrating a hugetlb page, which already considered the CONT-PTE or CONT-PMD size hugetlb.
---
include/linux/hugetlb.h | 11 +++++++++++ mm/rmap.c | 24 ++++++++++++++++++------ 2 files changed, 29 insertions(+), 6 deletions(-)
include/linux/hugetlb.h renamed from include/linux/hugetlb.h~mm-rmap-fix-cont-pte-pmd-size-hugetlb-issue-when-migration +11 -0
@@ -1093,6 +1093,17 @@ static inline void set_huge_swap_pte_at( pte_t *ptep, pte_t pte, unsigned long sz) { } + +static inline pte_t huge_ptep_clear_flush (struct vm_area_struct *vma, +unsigned long addr,pte_t *ptep) +{ +return *ptep; +} + +static inline void set_huge_pte_at (struct mm_struct *mm,unsigned long addr, +pte_t *ptep,pte_t pte) +{ +}#endif /* CONFIG_HUGETLB_PAGE */ static inline spinlock_t *huge_pte_lock(struct hstate *h,
mm/rmap.c renamed from mm/rmap.c~mm-rmap-fix-cont-pte-pmd-size-hugetlb-issue-when-migration +18 -6
@@ -1926,13 +1926,15 @@ static bool try_to_migrate_one(struct fobreak ; } } + +/* Nuke the hugetlb page table entry */ + pteval =huge_ptep_clear_flush (vma, address, pvmw.pte); }else {flush_cache_page (vma, address,pte_pfn (*pvmw.pte)); +/* Nuke the page table entry. */ + pteval =ptep_clear_flush (vma, address, pvmw.pte); } -/* Nuke the page table entry. */ - pteval =ptep_clear_flush (vma, address, pvmw.pte); -/* Set the dirty flag on the folio now the pte is gone. */ if (pte_dirty (pteval))folio_mark_dirty (folio);
@@ -2017,7 +2019,10 @@ static bool try_to_migrate_one(struct fopte_t swp_pte;if (arch_unmap_one (mm, vma, address, pteval) <0 ) { -set_pte_at (mm, address, pvmw.pte, pteval); +if (folio_test_hugetlb (folio)) +set_huge_pte_at (mm, address, pvmw.pte, pteval); +else +set_pte_at (mm, address, pvmw.pte, pteval); ret = false;page_vma_mapped_walk_done (&pvmw);break ;
@@ -2026,7 +2031,10 @@ static bool try_to_migrate_one(struct fo !anon_exclusive, subpage);if (anon_exclusive &&page_try_share_anon_rmap (subpage)) { -set_pte_at (mm, address, pvmw.pte, pteval); +if (folio_test_hugetlb (folio)) +set_huge_pte_at (mm, address, pvmw.pte, pteval); +else +set_pte_at (mm, address, pvmw.pte, pteval); ret = false;page_vma_mapped_walk_done (&pvmw);break ;
@@ -2052,7 +2060,11 @@ static bool try_to_migrate_one(struct fo swp_pte =pte_swp_mksoft_dirty (swp_pte);if (pte_uffd_wp (pteval)) swp_pte =pte_swp_mkuffd_wp (swp_pte); -set_pte_at (mm, address, pvmw.pte, swp_pte); +if (folio_test_hugetlb (folio)) +set_huge_swap_pte_at (mm, address, pvmw.pte, + swp_pte,vma_mmu_pagesize (vma)); +else +set_pte_at (mm, address, pvmw.pte, swp_pte);trace_set_migration_pte (address,pte_val (swp_pte),compound_order (&folio->page));/*
_
Patches currently in -mm which might be from [email protected] are