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Thu, 23 Jul 2020 06:14:44 +0000 (UTC) Received: from localhost (ovpn-13-53.pek2.redhat.com [10.72.13.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DAD345FC3B; Thu, 23 Jul 2020 06:14:40 +0000 (UTC) Date: Thu, 23 Jul 2020 14:14:37 +0800 From: Baoquan He To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mike.kravetz@oracle.com, david@redhat.com, akpm@linux-foundation.org Subject: Re: [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry() Message-ID: <20200723061437.GQ32539@MiWiFi-R3L-srv> References: <20200723032248.24772-1-bhe@redhat.com> <20200723032248.24772-3-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/23/20 at 10:36am, Anshuman Khandual wrote: > > > 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 > > Reviewed-by: Mike Kravetz > > Reviewed-by: David Hildenbrand > > --- > > 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. Thanks for your advice. Do you think updating the log as below is OK? ~~~~~~~~ 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(). So the checking non_swap_entry() in is_hugetlb_entry_migration() and is_hugetlb_entry_hwpoisoned() is redundant. Let's remove it to optimize code. ~~~~~~~~ Thanks Baoquan