• Zach O'Keefe's avatar
    mm/khugepaged: record SCAN_PMD_MAPPED when scan_pmd() finds hugepage · 50722804
    Zach O'Keefe authored
    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 f72e7dcd ("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 f72e7dcd ("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.comSigned-off-by: default avatarZach O'Keefe <zokeefe@google.com>
    Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
    Cc: Alex Shi <alex.shi@linux.alibaba.com>
    Cc: Andrea Arcangeli <aarcange@redhat.com>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Cc: Axel Rasmussen <axelrasmussen@google.com>
    Cc: Chris Kennelly <ckennelly@google.com>
    Cc: Chris Zankel <chris@zankel.net>
    Cc: David Hildenbrand <david@redhat.com>
    Cc: David Rientjes <rientjes@google.com>
    Cc: Helge Deller <deller@gmx.de>
    Cc: Hugh Dickins <hughd@google.com>
    Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
    Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Matt Turner <mattst88@gmail.com>
    Cc: Max Filippov <jcmvbkbc@gmail.com>
    Cc: Miaohe Lin <linmiaohe@huawei.com>
    Cc: Michal Hocko <mhocko@suse.com>
    Cc: Minchan Kim <minchan@kernel.org>
    Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
    Cc: Pavel Begunkov <asml.silence@gmail.com>
    Cc: Peter Xu <peterx@redhat.com>
    Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
    Cc: SeongJae Park <sj@kernel.org>
    Cc: Song Liu <songliubraving@fb.com>
    Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    Cc: Vlastimil Babka <vbabka@suse.cz>
    Cc: Zi Yan <ziy@nvidia.com>
    Cc: Dan Carpenter <dan.carpenter@oracle.com>
    Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    50722804
internal.h 27.5 KB