The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

Possible dependencies:

829ae0f81ce0 ("mm: migrate: fix THP's mapcount on isolation") 89f6c88a6ab4 ("mm: __isolate_lru_page_prepare() in isolate_migratepages_block()")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 829ae0f81ce093d674ff2256f66a714753e9ce32 Mon Sep 17 00:00:00 2001 From: Gavin Shan gshan@redhat.com Date: Thu, 24 Nov 2022 17:55:23 +0800 Subject: [PATCH] mm: migrate: fix THP's mapcount on isolation

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@redhat.com Fixes: 1da2f328fa64 ("mm,thp,compaction,cma: allow THP migration for CMA allocations") Signed-off-by: Gavin Shan gshan@redhat.com Reported-by: Zhenyu Zhang zhenyzha@redhat.com Tested-by: Zhenyu Zhang zhenyzha@redhat.com Suggested-by: David Hildenbrand david@redhat.com Acked-by: David Hildenbrand david@redhat.com Cc: Alistair Popple apopple@nvidia.com Cc: Hugh Dickins hughd@google.com Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Matthew Wilcox willy@infradead.org Cc: William Kucharski william.kucharski@oracle.com Cc: Zi Yan ziy@nvidia.com Cc: stable@vger.kernel.org [5.7+] Signed-off-by: Andrew Morton akpm@linux-foundation.org

diff --git a/mm/compaction.c b/mm/compaction.c index c51f7f545afe..1f6da31dd9a5 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -984,29 +984,29 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, 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; + /* * 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))