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    Subject[PATCH 5.4 59/71] mm: page_vma_mapped_walk(): prettify PVMW_MIGRATION block
    Date
    From: Hugh Dickins <hughd@google.com>

    page_vma_mapped_walk() cleanup: rearrange the !pmd_present() block to
    follow the same "return not_found, return not_found, return true"
    pattern as the block above it (note: returning not_found there is never
    premature, since existence or prior existence of huge pmd guarantees
    good alignment).

    Link: https://lkml.kernel.org/r/378c8650-1488-2edf-9647-32a53cf2e21@google.com
    Signed-off-by: Hugh Dickins <hughd@google.com>
    Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
    Reviewed-by: Peter Xu <peterx@redhat.com>
    Cc: Alistair Popple <apopple@nvidia.com>
    Cc: Matthew Wilcox <willy@infradead.org>
    Cc: Ralph Campbell <rcampbell@nvidia.com>
    Cc: Wang Yugui <wangyugui@e16-tech.com>
    Cc: Will Deacon <will@kernel.org>
    Cc: Yang Shi <shy828301@gmail.com>
    Cc: Zi Yan <ziy@nvidia.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    mm/page_vma_mapped.c | 30 ++++++++++++++----------------
    1 file changed, 14 insertions(+), 16 deletions(-)

    diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
    index 76503169c1e2..f9833b1e586a 100644
    --- a/mm/page_vma_mapped.c
    +++ b/mm/page_vma_mapped.c
    @@ -193,24 +193,22 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
    if (pmd_page(pmde) != page)
    return not_found(pvmw);
    return true;
    - } else if (!pmd_present(pmde)) {
    - if (thp_migration_supported()) {
    - if (!(pvmw->flags & PVMW_MIGRATION))
    - return not_found(pvmw);
    - if (is_migration_entry(pmd_to_swp_entry(pmde))) {
    - swp_entry_t entry = pmd_to_swp_entry(pmde);
    + }
    + if (!pmd_present(pmde)) {
    + swp_entry_t entry;

    - if (migration_entry_to_page(entry) != page)
    - return not_found(pvmw);
    - return true;
    - }
    - }
    - return not_found(pvmw);
    - } else {
    - /* THP pmd was split under us: handle on pte level */
    - spin_unlock(pvmw->ptl);
    - pvmw->ptl = NULL;
    + if (!thp_migration_supported() ||
    + !(pvmw->flags & PVMW_MIGRATION))
    + return not_found(pvmw);
    + entry = pmd_to_swp_entry(pmde);
    + if (!is_migration_entry(entry) ||
    + migration_entry_to_page(entry) != page)
    + return not_found(pvmw);
    + return true;
    }
    + /* THP pmd was split under us: handle on pte level */
    + spin_unlock(pvmw->ptl);
    + pvmw->ptl = NULL;
    } else if (!pmd_present(pmde)) {
    /*
    * If PVMW_SYNC, take and drop THP pmd lock so that we
    --
    2.30.2
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