The patch titled Subject: mm: migrate: fix THP's mapcount on isolation has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-migrate-fix-thps-mapcount-on-isolation.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------ From: Gavin Shan gshan@redhat.com Subject: mm: migrate: fix THP's mapcount on isolation Date: Thu, 24 Nov 2022 17:55:23 +0800
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 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 ---
mm/compaction.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)
--- a/mm/compaction.c~mm-migrate-fix-thps-mapcount-on-isolation +++ a/mm/compaction.c @@ -985,28 +985,28 @@ 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)) _
Patches currently in -mm which might be from gshan@redhat.com are
mm-migrate-fix-thps-mapcount-on-isolation.patch