The patch titled
Subject: mm: thp: clear PageDoubleMap flag when the last PMD map gone
has been added to the -mm tree. Its filename is
mm-thp-clear-pagedoublemap-flag-when-the-last-pmd-map-gone.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-clear-pagedoublemap-flag-when-the-last-pmd-map-gone.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-clear-pagedoublemap-flag-when-the-last-pmd-map-gone.patch
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------------------------------------------------------
From: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Subject: mm: thp: clear PageDoubleMap flag when the last PMD map gone
File THP sets PageDoubleMap flag when the first it gets PTE mapped, but
the flag is never cleared until the THP is freed. This result in
unbalanced state although it is not a big deal.
Clear the flag when the last compound_mapcount is gone. It should be
cleared when all the PTE maps are gone (become PMD mapped only) as well,
but this needs check all subpage's _mapcount every time any subpage's rmap
is removed, the overhead may be not worth. The anonymous THP also just
clears PageDoubleMap flag when the last PMD map is gone.
Link: http://lkml.kernel.org/r/1571938066-29031-1-git-send-email-yang.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Song Liu <songliubraving@xxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/rmap.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/rmap.c~mm-thp-clear-pagedoublemap-flag-when-the-last-pmd-map-gone
+++ a/mm/rmap.c
@@ -1256,6 +1256,9 @@ static void page_remove_file_rmap(struct
__dec_node_page_state(page, NR_SHMEM_PMDMAPPED);
else
__dec_node_page_state(page, NR_FILE_PMDMAPPED);
+
+ /* The last PMD map is gone */
+ ClearPageDoubleMap(compound_head(page));
} else {
if (!atomic_add_negative(-1, &page->_mapcount))
goto out;
_
Patches currently in -mm which might be from yang.shi@xxxxxxxxxxxxxxxxx are
mm-thp-handle-page-cache-thp-correctly-in-pagetranscompoundmap.patch
mm-thp-handle-page-cache-thp-correctly-in-pagetranscompoundmap-v4.patch
mm-vmscan-remove-unused-scan_control-parameter-from-pageout.patch
mm-thp-clear-pagedoublemap-flag-when-the-last-pmd-map-gone.patch
