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Thu, 06 Jul 2023 18:27:22 -0700 (PDT) MIME-Version: 1.0 References: <20230623164015.3431990-1-jiaqiyan@google.com> <20230623164015.3431990-3-jiaqiyan@google.com> <20230705235705.GE41006@monkey> <20230706220612.GA3768@monkey> In-Reply-To: <20230706220612.GA3768@monkey> From: Jiaqi Yan Date: Thu, 6 Jul 2023 18:27:11 -0700 Message-ID: Subject: Re: [PATCH v2 2/4] mm/hwpoison: check if a subpage of a hugetlb folio is raw HWPOISON To: Mike Kravetz Cc: naoya.horiguchi@nec.com, songmuchun@bytedance.com, shy828301@gmail.com, linmiaohe@huawei.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, duenwen@google.com, axelrasmussen@google.com, jthoughton@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 8C2E21A0010 X-Stat-Signature: 9y6xwiu5c4gy36duesmub644tbq918r9 X-HE-Tag: 1688693243-764469 X-HE-Meta: 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 ZV4Z+yXC 77J7WWDF9DG3Wb9ksZHSJ6e+YJ4QqENjpZF54JdmfeQPMlM+mJdMQRyBBUvAJ6/LO1g9oAr76GJV2khEwap/uEv5vyPV3h3dCsuGG3ViNMQIIcgKJAxrFFbJsMoKf+Abg4KXD9c940ImOukQbH1wbb3/YGUBYNMbHd2kDMAzrjWwn84EFzfu1oSD5hwlF52XLQ5QpEp3VFlEHDZA3Nnz9rNhW2lLhdGKrtgEj8Rs3YWx5w2ejK+rkrZaGaCmWJ/dWUT3Ul1jOoVwwXVkgnHfzJCTmipACt3HRqlVN 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 Thu, Jul 6, 2023 at 3:06=E2=80=AFPM Mike Kravetz wrote: > > On 07/06/23 11:25, Jiaqi Yan wrote: > > On Wed, Jul 5, 2023 at 4:57=E2=80=AFPM Mike Kravetz wrote: > > > On 06/23/23 16:40, Jiaqi Yan wrote: > > > > > > > > +bool is_raw_hwp_subpage(struct folio *folio, struct page *subpage) > > > > +{ > > > > + bool ret; > > > > + > > > > + spin_lock_irq(&hugetlb_lock); > > > > + ret =3D __is_raw_hwp_subpage(folio, subpage); > > > > + spin_unlock_irq(&hugetlb_lock); > > > > > > Can you describe what races the hugetlb_lock prevents here? > > > > I think we should sync here with __get_huge_page_for_hwpoison, who > > iterates and inserts an entry to raw_hwp_list. llist itself doesn't > > ensure insertion is synchronized with iterating from > > __is_raw_hwp_subpage. > > > > Ok, makes sense. And, since this is only called in the file read patch > when we encounter a PageHWPoison(page), the overhead of the lock cycles > is not of concern. Yes, thanks for pointing this out, (which I forgot), as is_raw_hwp_subpage() is after PageHWPoison check in hugetlbfs_read_iter. I think both this and the reason why holding the lock is worth mentioning in the commit msg. > > You can add, > > Reviewed-by: Mike Kravetz > -- > Mike Kravetz