From: Miaohe Lin linmiaohe@huawei.com
[ Upstream commit babbbdd08af98a59089334eb3effbed5a7a0cf7f ]
If other processes are mapping any other subpages of the hugepage, i.e. in pte-mapped thp case, page_mapcount() will return 1 incorrectly. Then we would discard the page while other processes are still mapping it. Fix it by using total_mapcount() which can tell whether other processes are still mapping it.
Link: https://lkml.kernel.org/r/20210511134857.1581273-6-linmiaohe@huawei.com Fixes: b8d3c4c3009d ("mm/huge_memory.c: don't split THP page when MADV_FREE syscall is called") Reviewed-by: Yang Shi shy828301@gmail.com Signed-off-by: Miaohe Lin linmiaohe@huawei.com Cc: Alexey Dobriyan adobriyan@gmail.com Cc: "Aneesh Kumar K . V" aneesh.kumar@linux.ibm.com Cc: Anshuman Khandual anshuman.khandual@arm.com Cc: David Hildenbrand david@redhat.com Cc: Hugh Dickins hughd@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: Matthew Wilcox willy@infradead.org Cc: Minchan Kim minchan@kernel.org Cc: Ralph Campbell rcampbell@nvidia.com Cc: Rik van Riel riel@surriel.com Cc: Song Liu songliubraving@fb.com Cc: William Kucharski william.kucharski@oracle.com Cc: Zi Yan ziy@nvidia.com Cc: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- mm/huge_memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 4400957d8e4e..800d7de32af8 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1692,7 +1692,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, * If other processes are mapping this page, we couldn't discard * the page unless they all do MADV_FREE so let's skip the page. */ - if (page_mapcount(page) != 1) + if (total_mapcount(page) != 1) goto out;
if (!trylock_page(page))