mm: migrate: remove PageTransHuge check in numamigrate_isolate_page()

Patch series "mm: migrate: more folio conversion and unification", v3.

Convert more migrate functions to use a folio, it is also a preparation
for large folio migration support when balancing numa.

This patch (of 8):

The assert VM_BUG_ON_PAGE(order && !PageTransHuge(page), page) is not very
useful,

   1) for a tail/base page, order = 0, for a head page, the order > 0 &&
      PageTransHuge() is true
   2) there is a PageCompound() check and only base page is handled in
      do_numa_page(), and do_huge_pmd_numa_page() only handle PMD-mapped
      THP
   3) even though the page is a tail page, isolate_lru_page() will post
      a warning, and fail to isolate the page
   4) if large folio/pte-mapped THP migration supported in the future,
      we could migrate the entire folio if numa fault on a tail page

so just remove the check.

Link: https://lkml.kernel.org/r/20230913095131.2426871-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20230913095131.2426871-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Suggested-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/migrate.c b/mm/migrate.c
index eb6bc4053bc4e1c9d8a631b204eb4b608b8c2767..d1b8ab5a241719ded7b59964b399ca5cb56e2470 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2486,8 +2486,6 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
        int nr_pages = thp_nr_pages(page);
        int order = compound_order(page);
 
-       VM_BUG_ON_PAGE(order && !PageTransHuge(page), page);
-
        /* Do not migrate THP mapped by multiple processes */
        if (PageTransHuge(page) && total_mapcount(page) > 1)
                return 0;