The patch titled
Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one
has been added to the -mm tree. Its filename is
mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
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------------------------------------------------------
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Subject: mm: migrate: do not migrate HugeTLB page whose refcount is one
All pages isolated for the migration have an elevated reference count and
therefore seeing a reference count equal to 1 means that the last user of
the page has dropped the reference and the page has became unused and
there doesn't make much sense to migrate it anymore. This has been done
for regular pages and this patch does the same for hugetlb pages.
Although the likelihood of the race is rather small for hugetlb pages it
makes sense the two code paths in sync.
Link: https://lkml.kernel.org/r/20210115124942.46403-2-songmuchun@xxxxxxxxxxxxx
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Acked-by: Yang Shi <shy828301@xxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 6 ++++++
1 file changed, 6 insertions(+)
--- a/mm/migrate.c~mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one
+++ a/mm/migrate.c
@@ -1280,6 +1280,12 @@ static int unmap_and_move_huge_page(new_
return -ENOSYS;
}
+ if (page_count(hpage) == 1) {
+ /* page was freed from under us. So we are done. */
+ putback_active_hugepage(hpage);
+ return MIGRATEPAGE_SUCCESS;
+ }
+
new_hpage = get_new_page(hpage, private);
if (!new_hpage)
return -ENOMEM;
_
Patches currently in -mm which might be from songmuchun@xxxxxxxxxxxxx are
mm-hugetlbfs-fix-cannot-migrate-the-fallocated-hugetlb-page.patch
mm-hugetlb-fix-a-race-between-freeing-and-dissolving-the-page.patch
mm-hugetlb-fix-a-race-between-isolating-and-freeing-page.patch
mm-hugetlb-remove-vm_bug_on_page-from-page_huge_active.patch
mm-migrate-do-not-migrate-hugetlb-page-whose-refcount-is-one.patch
mm-memcontrol-optimize-per-lruvec-stats-counter-memory-usage.patch
mm-memcontrol-fix-nr_anon_thps-accounting-in-charge-moving.patch
mm-memcontrol-convert-nr_anon_thps-account-to-pages.patch
mm-memcontrol-convert-nr_file_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_thps-account-to-pages.patch
mm-memcontrol-convert-nr_shmem_pmdmapped-account-to-pages.patch
mm-memcontrol-convert-nr_file_pmdmapped-account-to-pages.patch
mm-memcontrol-make-the-slab-calculation-consistent.patch
