On Sat, Jun 18, 2022 at 03:32:43PM +0800, Miaohe Lin wrote:
> When VM_BUG_ON check for THP migration entry, the existing code only check
> thp_migration_supported case, but not for !thp_migration_supported case.
> If !thp_migration_supported() and !pmd_present(), the original code may
> dead loop in theory. To make the VM_BUG_ON check more consistent, we need
> to catch both cases.
This patch makes no sense to me.
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/memory.c | 7 +++----
> 1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index fee2884481f2..6a9a17c7f58a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -5043,10 +5043,9 @@ static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
>
> barrier();
> if (unlikely(is_swap_pmd(vmf.orig_pmd))) {
> - VM_BUG_ON(thp_migration_supported() &&
> - !is_pmd_migration_entry(vmf.orig_pmd));
> - if (is_pmd_migration_entry(vmf.orig_pmd))
> - pmd_migration_entry_wait(mm, vmf.pmd);
> + VM_BUG_ON(!thp_migration_supported() ||
> + !is_pmd_migration_entry(vmf.orig_pmd));
> + pmd_migration_entry_wait(mm, vmf.pmd);
> return 0;
> }
> if (pmd_trans_huge(vmf.orig_pmd) || pmd_devmap(vmf.orig_pmd)) {
> --
> 2.23.0
>
>
