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    SubjectRe: [PATCH 6/7] migrate_pages(): fix failure counting for THP splitting
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    On 6/27/2022 10:24 AM, Huang Ying wrote:
    > If THP is failed to be migrated, it may be split and retry. But after
    > splitting, the head page will be left in "from" list, although THP
    > migration failure has been counted already. If the head page is
    > failed to be migrated too, the failure will be counted twice
    > incorrectly. So this is fixed in this patch via moving the head page
    > of THP after splitting to "thp_split_pages" too.
    >
    > Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
    > Fixes: 5984fabb6e82 ("mm: move_pages: report the number of non-attempted pages")
    > Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
    > Cc: Zi Yan <ziy@nvidia.com>
    > Cc: Yang Shi <shy828301@gmail.com>
    > ---

    Good catch. LGTM.
    Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>

    > mm/migrate.c | 7 ++++---
    > 1 file changed, 4 insertions(+), 3 deletions(-)
    >
    > diff --git a/mm/migrate.c b/mm/migrate.c
    > index 9d1883d5927f..70a0e1f34c03 100644
    > --- a/mm/migrate.c
    > +++ b/mm/migrate.c
    > @@ -1305,6 +1305,8 @@ static inline int try_split_thp(struct page *page, struct list_head *split_pages
    > lock_page(page);
    > rc = split_huge_page_to_list(page, split_pages);
    > unlock_page(page);
    > + if (!rc)
    > + list_move_tail(&page->lru, split_pages);
    >
    > return rc;
    > }
    > @@ -1364,7 +1366,6 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
    > thp_retry = 0;
    >
    > list_for_each_entry_safe(page, page2, from, lru) {
    > -retry:
    > /*
    > * THP statistics is based on the source huge page.
    > * Capture required information that might get lost
    > @@ -1411,7 +1412,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
    > nr_thp_failed++;
    > if (!try_split_thp(page, &thp_split_pages)) {
    > nr_thp_split++;
    > - goto retry;
    > + break;
    > }
    > /* Hugetlb migration is unsupported */
    > } else if (!no_subpage_counting) {
    > @@ -1431,7 +1432,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,
    > /* THP NUMA faulting doesn't split THP to retry. */
    > if (!nosplit && !try_split_thp(page, &thp_split_pages)) {
    > nr_thp_split++;
    > - goto retry;
    > + break;
    > }
    > } else if (!no_subpage_counting) {
    > nr_failed++;

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