From 50722804423680488b8063f6cc9a451333bf6f9b Mon Sep 17 00:00:00 2001 From: Zach O'Keefe Date: Wed, 6 Jul 2022 16:59:26 -0700 Subject: mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage When scanning an anon pmd to see if it's eligible for collapse, return SCAN_PMD_MAPPED if the pmd already maps a hugepage. Note that SCAN_PMD_MAPPED is different from SCAN_PAGE_COMPOUND used in the file-collapse path, since the latter might identify pte-mapped compound pages. This is required by MADV_COLLAPSE which necessarily needs to know what hugepage-aligned/sized regions are already pmd-mapped. In order to determine if a pmd already maps a hugepage, refactor mm_find_pmd(): Return mm_find_pmd() to it's pre-commit f72e7dcdd252 ("mm: let mm_find_pmd fix buggy race with THP fault") behavior. ksm was the only caller that explicitly wanted a pte-mapping pmd, so open code the pte-mapping logic there (pmd_present() and pmd_trans_huge() checks). Undo revert change in commit f72e7dcdd252 ("mm: let mm_find_pmd fix buggy race with THP fault") that open-coded split_huge_pmd_address() pmd lookup and use mm_find_pmd() instead. Link: https://lkml.kernel.org/r/20220706235936.2197195-9-zokeefe@google.com Signed-off-by: Zach O'Keefe Reviewed-by: Yang Shi Cc: Alex Shi Cc: Andrea Arcangeli Cc: Arnd Bergmann Cc: Axel Rasmussen Cc: Chris Kennelly Cc: Chris Zankel Cc: David Hildenbrand Cc: David Rientjes Cc: Helge Deller Cc: Hugh Dickins Cc: Ivan Kokshaysky Cc: James Bottomley Cc: Jens Axboe Cc: "Kirill A. Shutemov" Cc: Matthew Wilcox Cc: Matt Turner Cc: Max Filippov Cc: Miaohe Lin Cc: Michal Hocko Cc: Minchan Kim Cc: Pasha Tatashin Cc: Pavel Begunkov Cc: Peter Xu Cc: Rongwei Wang Cc: SeongJae Park Cc: Song Liu Cc: Thomas Bogendoerfer Cc: Vlastimil Babka Cc: Zi Yan Cc: Dan Carpenter Cc: "Souptick Joarder (HPE)" Signed-off-by: Andrew Morton --- include/trace/events/huge_memory.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/trace/events/huge_memory.h b/include/trace/events/huge_memory.h index d651f3437367..55392bf30a03 100644 --- a/include/trace/events/huge_memory.h +++ b/include/trace/events/huge_memory.h @@ -11,6 +11,7 @@ EM( SCAN_FAIL, "failed") \ EM( SCAN_SUCCEED, "succeeded") \ EM( SCAN_PMD_NULL, "pmd_null") \ + EM( SCAN_PMD_MAPPED, "page_pmd_mapped") \ EM( SCAN_EXCEED_NONE_PTE, "exceed_none_pte") \ EM( SCAN_EXCEED_SWAP_PTE, "exceed_swap_pte") \ EM( SCAN_EXCEED_SHARED_PTE, "exceed_shared_pte") \ -- cgit v1.2.3-59-g8ed1b