The patch titled
Subject: mm: page migration use migration entry for swapcache too
has been added to the -mm tree. Its filename is
mm-page-migration-use-migration-entry-for-swapcache-too.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page-migration-use-migration-entry-for-swapcache-too.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page-migration-use-migration-entry-for-swapcache-too.patch
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From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm: page migration use migration entry for swapcache too
Hitherto page migration has avoided using a migration entry for a
swapcache page mapped into userspace, apparently for historical reasons.
So any page blessed with swapcache would entail a minor fault when it's
next touched, which page migration otherwise tries to avoid. Swapcache in
an mlocked area is rare, so won't often matter, but still better fixed.
Just rearrange the block in try_to_unmap_one(), to handle TTU_MIGRATION
before checking PageAnon, that's all (apart from some reindenting).
Well, no, that's not quite all: doesn't this by the way fix a soft_dirty
bug, that page migration of a file page was forgetting to transfer the
soft_dirty bit? Probably not a serious bug: if I understand correctly,
soft_dirty afficionados usually have to handle file pages separately
anyway; but we publish the bit in /proc/<pid>/pagemap on file mappings as
well as anonymous, so page migration ought not to perturb it.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 63 ++++++++++++++++++++++++----------------------------
1 file changed, 30 insertions(+), 33 deletions(-)
diff -puN mm/rmap.c~mm-page-migration-use-migration-entry-for-swapcache-too mm/rmap.c
--- a/mm/rmap.c~mm-page-migration-use-migration-entry-for-swapcache-too
+++ a/mm/rmap.c
@@ -1379,47 +1379,44 @@ static int try_to_unmap_one(struct page
dec_mm_counter(mm, MM_ANONPAGES);
else
dec_mm_counter(mm, MM_FILEPAGES);
+ } else if (IS_ENABLED(CONFIG_MIGRATION) && (flags & TTU_MIGRATION)) {
+ swp_entry_t entry;
+ pte_t swp_pte;
+ /*
+ * Store the pfn of the page in a special migration
+ * pte. do_swap_page() will wait until the migration
+ * pte is removed and then restart fault handling.
+ */
+ entry = make_migration_entry(page, pte_write(pteval));
+ swp_pte = swp_entry_to_pte(entry);
+ if (pte_soft_dirty(pteval))
+ swp_pte = pte_swp_mksoft_dirty(swp_pte);
+ set_pte_at(mm, address, pte, swp_pte);
} else if (PageAnon(page)) {
swp_entry_t entry = { .val = page_private(page) };
pte_t swp_pte;
-
- if (PageSwapCache(page)) {
- /*
- * Store the swap location in the pte.
- * See handle_pte_fault() ...
- */
- if (swap_duplicate(entry) < 0) {
- set_pte_at(mm, address, pte, pteval);
- ret = SWAP_FAIL;
- goto out_unmap;
- }
- if (list_empty(&mm->mmlist)) {
- spin_lock(&mmlist_lock);
- if (list_empty(&mm->mmlist))
- list_add(&mm->mmlist, &init_mm.mmlist);
- spin_unlock(&mmlist_lock);
- }
- dec_mm_counter(mm, MM_ANONPAGES);
- inc_mm_counter(mm, MM_SWAPENTS);
- } else if (IS_ENABLED(CONFIG_MIGRATION)) {
- /*
- * Store the pfn of the page in a special migration
- * pte. do_swap_page() will wait until the migration
- * pte is removed and then restart fault handling.
- */
- BUG_ON(!(flags & TTU_MIGRATION));
- entry = make_migration_entry(page, pte_write(pteval));
+ /*
+ * Store the swap location in the pte.
+ * See handle_pte_fault() ...
+ */
+ VM_BUG_ON_PAGE(!PageSwapCache(page), page);
+ if (swap_duplicate(entry) < 0) {
+ set_pte_at(mm, address, pte, pteval);
+ ret = SWAP_FAIL;
+ goto out_unmap;
}
+ if (list_empty(&mm->mmlist)) {
+ spin_lock(&mmlist_lock);
+ if (list_empty(&mm->mmlist))
+ list_add(&mm->mmlist, &init_mm.mmlist);
+ spin_unlock(&mmlist_lock);
+ }
+ dec_mm_counter(mm, MM_ANONPAGES);
+ inc_mm_counter(mm, MM_SWAPENTS);
swp_pte = swp_entry_to_pte(entry);
if (pte_soft_dirty(pteval))
swp_pte = pte_swp_mksoft_dirty(swp_pte);
set_pte_at(mm, address, pte, swp_pte);
- } else if (IS_ENABLED(CONFIG_MIGRATION) &&
- (flags & TTU_MIGRATION)) {
- /* Establish migration entry for a file page */
- swp_entry_t entry;
- entry = make_migration_entry(page, pte_write(pteval));
- set_pte_at(mm, address, pte, swp_entry_to_pte(entry));
} else
dec_mm_counter(mm, MM_FILEPAGES);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
memcg-simplify-and-inline-__mem_cgroup_from_kmem-fix-2.patch
mm-documentation-undoc-non-linear-vmas.patch
mm-rmap-use-pte-lock-not-mmap_sem-to-set-pagemlocked.patch
mm-page-migration-fix-pagemlocked-on-migrated-pages.patch
mm-rename-mem_cgroup_migrate-to-mem_cgroup_replace_page.patch
mm-correct-a-couple-of-page-migration-comments.patch
mm-page-migration-use-the-put_new_page-whenever-necessary.patch
mm-page-migration-trylock-newpage-at-same-level-as-oldpage.patch
mm-page-migration-remove_migration_ptes-at-lockunlock-level.patch
mm-simplify-page-migrations-anon_vma-comment-and-flow.patch
mm-page-migration-use-migration-entry-for-swapcache-too.patch
mm-page-migration-avoid-touching-newpage-until-no-going-back.patch
mm-migrate-dirty-page-without-clear_page_dirty_for_io-etc.patch
mm-use-unsigned-int-for-page-order-fix-2.patch
mm-dont-split-thp-page-when-syscall-is-called-fix-4.patch
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