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Thu, 23 Jul 2020 08:53:29 +0000 (UTC) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B9ED1D6E; Thu, 23 Jul 2020 01:53:28 -0700 (PDT) Received: from [10.163.85.73] (unknown [10.163.85.73]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8E46D3F66F; Thu, 23 Jul 2020 01:53:26 -0700 (PDT) Subject: Re: [PATCH v2 2/4] mm/hugetlb.c: Remove the unnecessary non_swap_entry() To: Baoquan He Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, mike.kravetz@oracle.com, david@redhat.com, akpm@linux-foundation.org References: <20200723032248.24772-1-bhe@redhat.com> <20200723032248.24772-3-bhe@redhat.com> <20200723061437.GQ32539@MiWiFi-R3L-srv> From: Anshuman Khandual Message-ID: <7c0d19e9-4f90-9f74-d364-4d877ccf67f9@arm.com> Date: Thu, 23 Jul 2020 14:22:58 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20200723061437.GQ32539@MiWiFi-R3L-srv> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5A5C3180C3D27 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 07/23/2020 11:44 AM, Baoquan He wrote: > 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. > ~~~~~~~~ Something like above would be good.