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SubjectRe: [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry()
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On 07/23/2020 08:52 AM, Baoquan He wrote:
> The checking is_migration_entry() and is_hwpoison_entry() are stricter
> than non_swap_entry(), means they have covered the conditional check
> which non_swap_entry() is doing.

They are no stricter as such but implicitly contains non_swap_entry() in itself.
If a swap entry tests positive for either is_[migration|hwpoison]_entry(), then
its swap_type() is among SWP_MIGRATION_READ, SWP_MIGRATION_WRITE and SWP_HWPOISON.
All these types >= MAX_SWAPFILES, exactly what is asserted with non_swap_entry().

>
> Hence remove the unnecessary non_swap_entry() in is_hugetlb_entry_migration()
> and is_hugetlb_entry_hwpoisoned() to simplify code.
>
> Signed-off-by: Baoquan He <bhe@redhat.com>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
> mm/hugetlb.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3569e731e66b..c14837854392 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3748,7 +3748,7 @@ bool is_hugetlb_entry_migration(pte_t pte)
> if (huge_pte_none(pte) || pte_present(pte))
> return false;
> swp = pte_to_swp_entry(pte);
> - if (non_swap_entry(swp) && is_migration_entry(swp))
> + if (is_migration_entry(swp))
> return true;
> else
> return false;
> @@ -3761,7 +3761,7 @@ static bool is_hugetlb_entry_hwpoisoned(pte_t pte)
> if (huge_pte_none(pte) || pte_present(pte))
> return false;
> swp = pte_to_swp_entry(pte);
> - if (non_swap_entry(swp) && is_hwpoison_entry(swp))
> + if (is_hwpoison_entry(swp))
> return true;
> else
> return false;
>

It would be better if the commit message contains details about
the existing redundant check. But either way.

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

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