The patch titled
Subject: thp: make sure we replace the right page with migration entires
has been added to the -mm tree. Its filename is
thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: thp: make sure we replace the right page with migration entires
split_huge_pmd_address(freeze == true) would split the pmd and setup
migration entries into ptes.
To get it work properly we need a page to check pmd against. Otherwise
we can end up replacing wrong page (i.e. after COW break).
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/huge_mm.h | 4 ++--
mm/huge_memory.c | 17 +++++++++++++----
mm/rmap.c | 3 ++-
3 files changed, 17 insertions(+), 7 deletions(-)
diff -puN include/linux/huge_mm.h~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix include/linux/huge_mm.h
--- a/include/linux/huge_mm.h~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix
+++ a/include/linux/huge_mm.h
@@ -109,7 +109,7 @@ void __split_huge_pmd(struct vm_area_str
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
- bool freeze);
+ bool freeze, struct page *page);
#if HPAGE_PMD_ORDER >= MAX_ORDER
#error "hugepages can't be allocated by the buddy allocator"
@@ -180,7 +180,7 @@ static inline void deferred_split_huge_p
do { } while (0)
static inline void split_huge_pmd_address(struct vm_area_struct *vma,
- unsigned long address, bool freeze) {}
+ unsigned long address, bool freeze, struct page *page) {}
static inline int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
diff -puN mm/huge_memory.c~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix mm/huge_memory.c
--- a/mm/huge_memory.c~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix
+++ a/mm/huge_memory.c
@@ -3007,7 +3007,7 @@ out:
}
void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address,
- bool freeze)
+ bool freeze, struct page *page)
{
pgd_t *pgd;
pud_t *pud;
@@ -3024,6 +3024,15 @@ void split_huge_pmd_address(struct vm_ar
pmd = pmd_offset(pud, address);
if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
return;
+
+ /*
+ * If caller asks to setup a migration entries, we need a page to check
+ * pmd against. Otherwise we can end up replacing wrong page.
+ */
+ VM_BUG_ON(freeze && !page);
+ if (page && page != pmd_page(*pmd))
+ return;
+
/*
* Caller holds the mmap_sem write mode, so a huge pmd cannot
* materialize from under us.
@@ -3044,7 +3053,7 @@ void vma_adjust_trans_huge(struct vm_are
if (start & ~HPAGE_PMD_MASK &&
(start & HPAGE_PMD_MASK) >= vma->vm_start &&
(start & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
- split_huge_pmd_address(vma, start, false);
+ split_huge_pmd_address(vma, start, false, NULL);
/*
* If the new end address isn't hpage aligned and it could
@@ -3054,7 +3063,7 @@ void vma_adjust_trans_huge(struct vm_are
if (end & ~HPAGE_PMD_MASK &&
(end & HPAGE_PMD_MASK) >= vma->vm_start &&
(end & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= vma->vm_end)
- split_huge_pmd_address(vma, end, false);
+ split_huge_pmd_address(vma, end, false, NULL);
/*
* If we're also updating the vma->vm_next->vm_start, if the new
@@ -3068,7 +3077,7 @@ void vma_adjust_trans_huge(struct vm_are
if (nstart & ~HPAGE_PMD_MASK &&
(nstart & HPAGE_PMD_MASK) >= next->vm_start &&
(nstart & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE <= next->vm_end)
- split_huge_pmd_address(next, nstart, false);
+ split_huge_pmd_address(next, nstart, false, NULL);
}
}
diff -puN mm/rmap.c~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix mm/rmap.c
--- a/mm/rmap.c~thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix
+++ a/mm/rmap.c
@@ -1432,7 +1432,8 @@ static int try_to_unmap_one(struct page
goto out;
if (flags & TTU_SPLIT_HUGE_PMD) {
- split_huge_pmd_address(vma, address, flags & TTU_MIGRATION);
+ split_huge_pmd_address(vma, address,
+ flags & TTU_MIGRATION, page);
/* check if we have anything to do after split */
if (page_mapcount(page) == 0)
goto out;
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
thp-cleanup-split_huge_page.patch
thp-vmstats-count-deferred-split-events.patch
mm-tracing-refresh-__def_vmaflag_names.patch
mm-cleanup-pte_alloc-interfaces.patch
rmap-introduce-rmap_walk_locked.patch
rmap-extend-try_to_unmap-to-be-usable-by-split_huge_page.patch
mm-make-remove_migration_ptes-beyond-mm-migrationc.patch
thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers.patch
thp-rewrite-freeze_page-unfreeze_page-with-generic-rmap-walkers-fix.patch
thp-fix-deadlock-in-split_huge_pmd.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-2.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-3.patch
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