The patch titled
Subject: mm: migrate: simplify the refcount validation when migrating hugetlb mapping
has been added to the -mm tree. Its filename is
mm-migrate-simplify-the-refcount-validation-when-migrating-hugetlb-mapping.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-migrate-simplify-the-refcount-validation-when-migrating-hugetlb-mapping.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-migrate-simplify-the-refcount-validation-when-migrating-hugetlb-mapping.patch
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------------------------------------------------------
From: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Subject: mm: migrate: simplify the refcount validation when migrating hugetlb mapping
There is no need to validate the hugetlb page's refcount before trying to
freeze the hugetlb page's expected refcount, instead we can just rely on
the page_ref_freeze() to simplify the validation.
Moreover we are always under the page lock when migrating the hugetlb page
mapping, which means nowhere else can remove it from the page cache, so we
can remove the xas_load() validation under the i_pages lock.
Link: https://lkml.kernel.org/r/eb2fbbeaef2b1714097b9dec457426d682ee0635.1649676424.git.baolin.wang@xxxxxxxxxxxxxxxxx
Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/migrate.c~mm-migrate-simplify-the-refcount-validation-when-migrating-hugetlb-mapping
+++ a/mm/migrate.c
@@ -477,11 +477,6 @@ int migrate_huge_page_move_mapping(struc
xas_lock_irq(&xas);
expected_count = 2 + page_has_private(page);
- if (page_count(page) != expected_count || xas_load(&xas) != page) {
- xas_unlock_irq(&xas);
- return -EAGAIN;
- }
-
if (!page_ref_freeze(page, expected_count)) {
xas_unlock_irq(&xas);
return -EAGAIN;
_
Patches currently in -mm which might be from baolin.wang@xxxxxxxxxxxxxxxxx are
mm-migrate-simplify-the-refcount-validation-when-migrating-hugetlb-mapping.patch
