Messages in this thread Patch in this message | | | From | Gavin Shan <> | Subject | [PATCH] mm: migrate: Fix THP's mapcount on isolation | Date | Wed, 23 Nov 2022 08:57:52 +0800 |
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The issue is reported when removing memory through virtio_mem device. The transparent huge page, experienced copy-on-write fault, is wrongly regarded as pinned. The transparent huge page is escaped from being isolated in isolate_migratepages_block(). The transparent huge page can't be migrated and the corresponding memory block can't be put into offline state.
Fix it by replacing page_mapcount() with total_mapcount(). With this, the transparent huge page can be isolated and migrated, and the memory block can be put into offline state.
Fixes: 3917c80280c9 ("thp: change CoW semantics for anon-THP") Cc: stable@vger.kernel.org # v5.8+ Reported-by: Zhenyu Zhang <zhenyzha@redhat.com> Suggested-by: David Hildenbrand <david@redhat.com> Signed-off-by: Gavin Shan <gshan@redhat.com> --- mm/compaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/compaction.c b/mm/compaction.c index c51f7f545afe..c408b5e04c1d 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -990,7 +990,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, * admittedly racy check. */ mapping = page_mapping(page); - if (!mapping && page_count(page) > page_mapcount(page)) + if (!mapping && page_count(page) > total_mapcount(page)) goto isolate_fail; /* -- 2.23.0
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