+ mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch added to -mm tree

+ mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/huge_memory.c: don't discard hugepage if other processes are mapping it
has been added to the -mm tree.  Its filename is
     mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch

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------------------------------------------------------
From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/huge_memory.c: don't discard hugepage if other processes are mapping it

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>
---

 mm/huge_memory.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/huge_memory.c~mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it
+++ a/mm/huge_memory.c
@@ -1610,7 +1610,7 @@ bool madvise_free_huge_pmd(struct mmu_ga
 	 * 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))
_

Patches currently in -mm which might be from linmiaohe@huawei.com are

mm-swapfile-use-percpu_ref-to-serialize-against-concurrent-swapoff.patch
swap-fix-do_swap_page-race-with-swapoff.patch
mm-swap-remove-confusing-checking-for-non_swap_entry-in-swap_ra_info.patch
mm-shmem-fix-shmem_swapin-race-with-swapoff.patch
mm-huge_memoryc-remove-dedicated-macro-hpage_cache_index_mask.patch
mm-huge_memoryc-use-page-deferred_list.patch
mm-huge_memoryc-add-missing-read-only-thp-checking-in-transparent_hugepage_enabled.patch
mm-huge_memoryc-remove-unnecessary-tlb_remove_page_size-for-huge-zero-pmd.patch
mm-huge_memoryc-dont-discard-hugepage-if-other-processes-are-mapping-it.patch