The patch titled
mm: compaction: expand comment on unmapped page swap cache
has been added to the -mm tree. Its filename is
mm-migration-allow-the-migration-of-pageswapcache-pages-fix.patch
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Subject: mm: compaction: expand comment on unmapped page swap cache
From: Mel Gorman <mel@xxxxxxxxx>
The comment on the handling of anon_vma for unmapped pages is a bit
sparse. Expand it.
Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/migrate.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff -puN mm/migrate.c~mm-migration-allow-the-migration-of-pageswapcache-pages-fix mm/migrate.c
--- a/mm/migrate.c~mm-migration-allow-the-migration-of-pageswapcache-pages-fix
+++ a/mm/migrate.c
@@ -612,9 +612,15 @@ static int unmap_and_move(new_page_t get
/*
* We cannot be sure that the anon_vma of an unmapped
- * swapcache page is safe to use. In this case, the
- * swapcache page gets migrated but the pages are not
- * remapped
+ * swapcache page is safe to use because we don't
+ * know in advance if the VMA that this page belonged
+ * to still exists. If the VMA and others sharing the
+ * data have been freed, then the anon_vma could
+ * already be invalid.
+ *
+ * To avoid this possibility, swapcache pages get
+ * migrated but are not remapped when migration
+ * completes
*/
remap_swapcache = 0;
} else {
_
Patches currently in -mm which might be from mel@xxxxxxxxx are
page-allocator-reduce-fragmentation-in-buddy-allocator-by-adding-buddies-that-are-merging-to-the-tail-of-the-free-lists.patch
mempolicy-remove-redundant-code.patch
mm-default-to-node-zonelist-ordering-when-nodes-have-only-lowmem.patch
mm-migration-take-a-reference-to-the-anon_vma-before-migrating.patch
mm-migration-do-not-try-to-migrate-unmapped-anonymous-pages.patch
mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration.patch
mm-allow-config_migration-to-be-set-without-config_numa-or-memory-hot-remove.patch
mm-allow-config_migration-to-be-set-without-config_numa-or-memory-hot-remove-fix.patch
mm-export-unusable-free-space-index-via-proc-unusable_index.patch
mm-export-fragmentation-index-via-proc-extfrag_index.patch
mm-move-definition-for-lru-isolation-modes-to-a-header.patch
mm-compaction-memory-compaction-core.patch
mm-compaction-memory-compaction-core-fix.patch
mm-compaction-add-proc-trigger-for-memory-compaction.patch
mm-compaction-add-proc-trigger-for-memory-compaction-fix.patch
mm-compaction-add-proc-trigger-for-memory-compaction-fix-fix.patch
mm-compaction-add-sys-trigger-for-per-node-memory-compaction.patch
mm-compaction-direct-compact-when-a-high-order-allocation-fails.patch
mm-compaction-direct-compact-when-a-high-order-allocation-fails-reject-fix.patch
mm-compaction-add-a-tunable-that-decides-when-memory-should-be-compacted-and-when-it-should-be-reclaimed.patch
mm-compaction-do-not-compact-within-a-preferred-zone-after-a-compaction-failure.patch
mm-migration-allow-the-migration-of-pageswapcache-pages.patch
mm-migration-allow-the-migration-of-pageswapcache-pages-fix.patch
mm-compaction-do-not-display-compaction-related-stats-when-config_compaction.patch
mm-compaction-do-not-display-compaction-related-stats-when-config_compaction-reject-fix.patch
delay-accounting-re-implement-c-for-getdelaysc-to-report-information-on-a-target-command.patch
delay-accounting-re-implement-c-for-getdelaysc-to-report-information-on-a-target-command-checkpatch-fixes.patch
add-debugging-aid-for-memory-initialisation-problems.patch
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