From: Gavin Shan <gshan@xxxxxxxxxx> commit 829ae0f81ce093d674ff2256f66a714753e9ce32 upstream. 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. Besides, The page's refcount is increased a bit earlier to avoid the page is released when the check is executed. Link: https://lkml.kernel.org/r/20221124095523.31061-1-gshan@xxxxxxxxxx Fixes: 1da2f328fa64 ("mm,thp,compaction,cma: allow THP migration for CMA allocations") Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx> Reported-by: Zhenyu Zhang <zhenyzha@xxxxxxxxxx> Tested-by: Zhenyu Zhang <zhenyzha@xxxxxxxxxx> Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: David Hildenbrand <david@xxxxxxxxxx> Cc: Alistair Popple <apopple@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: William Kucharski <william.kucharski@xxxxxxxxxx> Cc: Zi Yan <ziy@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> [5.7+] Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) --- a/mm/compaction.c +++ b/mm/compaction.c @@ -987,28 +987,28 @@ isolate_migratepages_block(struct compac } /* + * Be careful not to clear PageLRU until after we're + * sure the page is not being freed elsewhere -- the + * page release code relies on it. + */ + if (unlikely(!get_page_unless_zero(page))) + goto isolate_fail; + + /* * Migration will fail if an anonymous page is pinned in memory, * so avoid taking lru_lock and isolating it unnecessarily in an * admittedly racy check. */ mapping = page_mapping(page); - if (!mapping && page_count(page) > page_mapcount(page)) - goto isolate_fail; + if (!mapping && (page_count(page) - 1) > total_mapcount(page)) + goto isolate_fail_put; /* * Only allow to migrate anonymous pages in GFP_NOFS context * because those do not depend on fs locks. */ if (!(cc->gfp_mask & __GFP_FS) && mapping) - goto isolate_fail; - - /* - * Be careful not to clear PageLRU until after we're - * sure the page is not being freed elsewhere -- the - * page release code relies on it. - */ - if (unlikely(!get_page_unless_zero(page))) - goto isolate_fail; + goto isolate_fail_put; /* Only take pages on LRU: a check now makes later tests safe */ if (!PageLRU(page))
