mm: thp: remove redundant pgtable check in set_huge_zero_page()

When the pgtable is NULL in the set_huge_zero_page(), we should not
increment the count of PTE page table pages by calling mm_inc_nr_ptes().
Otherwise we may receive the following warning when the mm exits:

	BUG: non-zero pgtables_bytes on freeing mm

Now we can't observe the above warning since only
do_huge_pmd_anonymous_page() invokes set_huge_zero_page() and the pgtable
can not be NULL.

Therefore, instead of moving mm_inc_nr_ptes() to the non-NULL branch of
pgtable, it is better to remove the redundant pgtable check directly.

Link: https://lkml.kernel.org/r/20220818082748.40021-1-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 37105d9..286a70c 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -770,8 +770,7 @@ static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
                return;
        entry = mk_pmd(zero_page, vma->vm_page_prot);
        entry = pmd_mkhuge(entry);
-       if (pgtable)
-               pgtable_trans_huge_deposit(mm, pmd, pgtable);
+       pgtable_trans_huge_deposit(mm, pmd, pgtable);
        set_pmd_at(mm, haddr, pmd, entry);
        mm_inc_nr_ptes(mm);
 }