The patch titled
Subject: mm: fix handling PTE-mapped THPs in page_referenced()
has been added to the -mm tree. Its filename is
mm-fix-handling-pte-mapped-thps-in-page_referenced.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-fix-handling-pte-mapped-thps-in-page_referenced.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-handling-pte-mapped-thps-in-page_referenced.patch
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From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: fix handling PTE-mapped THPs in page_referenced()
For PTE-mapped THP page_check_address_transhuge() is not adequate: it
cannot find all relevant PTEs, only the first one. It means we can miss
some references of the page and it can result in suboptimal decisions by
vmscan.
Let's switch it to page_vma_mapped_walk().
I don't think it's subject for stable@: it's not fatal. The only side
effect is that THP can be swapped out when it shouldn't.
Link: http://lkml.kernel.org/r/20170129173858.45174-4-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Srikar Dronamraju <srikar@xxxxxxxxxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 66 ++++++++++++++++++++++++++--------------------------
1 file changed, 34 insertions(+), 32 deletions(-)
diff -puN mm/rmap.c~mm-fix-handling-pte-mapped-thps-in-page_referenced mm/rmap.c
--- a/mm/rmap.c~mm-fix-handling-pte-mapped-thps-in-page_referenced
+++ a/mm/rmap.c
@@ -886,45 +886,48 @@ struct page_referenced_arg {
static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
unsigned long address, void *arg)
{
- struct mm_struct *mm = vma->vm_mm;
struct page_referenced_arg *pra = arg;
- pmd_t *pmd;
- pte_t *pte;
- spinlock_t *ptl;
+ struct page_vma_mapped_walk pvmw = {
+ .page = page,
+ .vma = vma,
+ .address = address,
+ };
int referenced = 0;
- if (!page_check_address_transhuge(page, mm, address, &pmd, &pte, &ptl))
- return SWAP_AGAIN;
+ while (page_vma_mapped_walk(&pvmw)) {
+ address = pvmw.address;
- if (vma->vm_flags & VM_LOCKED) {
- if (pte)
- pte_unmap(pte);
- spin_unlock(ptl);
- pra->vm_flags |= VM_LOCKED;
- return SWAP_FAIL; /* To break the loop */
- }
+ if (vma->vm_flags & VM_LOCKED) {
+ page_vma_mapped_walk_done(&pvmw);
+ pra->vm_flags |= VM_LOCKED;
+ return SWAP_FAIL; /* To break the loop */
+ }
- if (pte) {
- if (ptep_clear_flush_young_notify(vma, address, pte)) {
- /*
- * Don't treat a reference through a sequentially read
- * mapping as such. If the page has been used in
- * another mapping, we will catch it; if this other
- * mapping is already gone, the unmap path will have
- * set PG_referenced or activated the page.
- */
- if (likely(!(vma->vm_flags & VM_SEQ_READ)))
+ if (pvmw.pte) {
+ if (ptep_clear_flush_young_notify(vma, address,
+ pvmw.pte)) {
+ /*
+ * Don't treat a reference through
+ * a sequentially read mapping as such.
+ * If the page has been used in another mapping,
+ * we will catch it; if this other mapping is
+ * already gone, the unmap path will have set
+ * PG_referenced or activated the page.
+ */
+ if (likely(!(vma->vm_flags & VM_SEQ_READ)))
+ referenced++;
+ }
+ } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
+ if (pmdp_clear_flush_young_notify(vma, address,
+ pvmw.pmd))
referenced++;
+ } else {
+ /* unexpected pmd-mapped page? */
+ WARN_ON_ONCE(1);
}
- pte_unmap(pte);
- } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) {
- if (pmdp_clear_flush_young_notify(vma, address, pmd))
- referenced++;
- } else {
- /* unexpected pmd-mapped page? */
- WARN_ON_ONCE(1);
+
+ pra->mapcount--;
}
- spin_unlock(ptl);
if (referenced)
clear_page_idle(page);
@@ -936,7 +939,6 @@ static int page_referenced_one(struct pa
pra->vm_flags |= vma->vm_flags;
}
- pra->mapcount--;
if (!pra->mapcount)
return SWAP_SUCCESS; /* To break the loop */
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-sleeping-function-called-from-invalid-context-shmem_undo_range.patch
mm-drop-zap_details-ignore_dirty.patch
mm-drop-zap_details-check_swap_entries.patch
mm-drop-unused-argument-of-zap_page_range.patch
oom-reaper-use-madvise_dontneed-logic-to-decide-if-unmap-the-vma.patch
uprobes-split-thps-before-trying-replace-them.patch
mm-introduce-page_vma_mapped_walk.patch
mm-fix-handling-pte-mapped-thps-in-page_referenced.patch
mm-fix-handling-pte-mapped-thps-in-page_idle_clear_pte_refs.patch
mm-rmap-check-all-vmas-that-pte-mapped-thp-can-be-part-of.patch
mm-convert-page_mkclean_one-to-use-page_vma_mapped_walk.patch
mm-convert-try_to_unmap_one-to-use-page_vma_mapped_walk.patch
mm-ksm-convert-write_protect_page-to-use-page_vma_mapped_walk.patch
mm-uprobes-convert-__replace_page-to-use-page_vma_mapped_walk.patch
mm-convert-page_mapped_in_vma-to-use-page_vma_mapped_walk.patch
mm-drop-page_check_address_transhuge.patch
mm-convert-remove_migration_pte-to-use-page_vma_mapped_walk.patch
--
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