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From: Muchun Song In-Reply-To: Date: Thu, 18 Aug 2022 11:39:04 +0800 Cc: sj@kernel.org, Andrew Morton , damon@lists.linux.dev, Linux MM , linux-kernel@vger.kernel.org, Mike Kravetz Content-Transfer-Encoding: quoted-printable Message-Id: <6F99AE03-3C74-4E5B-87E1-6F3232BEEBB5@linux.dev> References: <2838b6737bc259cf575ff11fd1c4b7fdb340fa73.1660717122.git.baolin.wang@linux.alibaba.com> <5173E308-2403-4667-9162-865CF7F11838@linux.dev> To: Baolin Wang X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gIhBAaU7; spf=pass (imf22.hostedemail.com: domain of muchun.song@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660793992; a=rsa-sha256; cv=none; b=q419aTgKZiHwTp1eMBUVUChb30lHe7UpdbTboYqFXoF0wJlbYIYJmnE92oy7z0u18Rb85U y3sX5uLA0RJvnVTVkY92X+etNduziQu81A63Vxos1tQZx7QefUTlyigddBNtYhl06RZY1m qisfW1gHkZIVWesBT1Uc7iGdHqzJNDU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660793992; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=KUyb1pCJ/oDKXbqiOy+EBzbV0azHcNvfFJQrGl3ZoHw=; b=KSlb44i95U2SF3pGPfe4jYuU5UJ1uOcYhTf7011n3yqh5nCvr2EmmfxZsALSzP+JBf3qVU dBu2LP/N6ordAxH1/GigKZE30Ox6zGU14HPXjoYaFvaXa0z8onUsEVYF9vXEAGfKZfN8AM 4kc9I9kQYPeVBTlw/aifUvLiV2qHHdY= X-Rspamd-Queue-Id: 8B223C019B Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=gIhBAaU7; spf=pass (imf22.hostedemail.com: domain of muchun.song@linux.dev designates 94.23.1.103 as permitted sender) smtp.mailfrom=muchun.song@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: nh3jomwmyrjwymyahxox317ytnsymiqs X-HE-Tag: 1660793992-763904 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 Aug 18, 2022, at 10:57, Baolin Wang = wrote: >=20 >=20 >=20 > =E5=9C=A8 8/18/2022 10:41 AM, Muchun Song =E5=86=99=E9=81=93: >>> On Aug 17, 2022, at 14:21, Baolin Wang = wrote: >>>=20 >>> The pmd_huge() is used to validate if the pmd entry is mapped by a = huge >>> page, also including the case of non-present (migration or = hwpoisoned) >>> pmd entry on arm64 or x86 architectures. Thus we should validate if = it >>> is present before making the pmd entry old or getting young state, >>> otherwise we can not get the correct corresponding page. >>>=20 >>> Signed-off-by: Baolin Wang >>> --- >>> mm/damon/vaddr.c | 10 ++++++++++ >>> 1 file changed, 10 insertions(+) >>>=20 >>> diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c >>> index 3c7b9d6..1d16c6c 100644 >>> --- a/mm/damon/vaddr.c >>> +++ b/mm/damon/vaddr.c >>> @@ -304,6 +304,11 @@ static int damon_mkold_pmd_entry(pmd_t *pmd, = unsigned long addr, >>>=20 >>> if (pmd_huge(*pmd)) { >>> ptl =3D pmd_lock(walk->mm, pmd); >>> + if (!pmd_present(*pmd)) { >> Unluckily, we should use pte_present here. See commit c9d398fa23788. = We can use >> huge_ptep_get() to get a hugetlb pte, so it=E2=80=99s better to put = the check after >> pmd_huge. >=20 > IMO this is not the case for hugetlb, and the hugetlb case will be = handled by damon_mkold_hugetlb_entry(), which already used pte_present() = for hugetlb case. Well, I thought it is hugetlb related since I saw the usage of pmd_huge. = If it is THP case, why not use pmd_trans_huge? Thanks. >=20 >> Cc Mike to make sure I am not missing something. >> Muchun, >> Thanks. >>> + spin_unlock(ptl); >>> + return 0; >>> + } >>> + >>> if (pmd_huge(*pmd)) { >>> damon_pmdp_mkold(pmd, walk->mm, addr); >>> spin_unlock(ptl); >>> @@ -431,6 +436,11 @@ static int damon_young_pmd_entry(pmd_t *pmd, = unsigned long addr, >>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE >>> if (pmd_huge(*pmd)) { >>> ptl =3D pmd_lock(walk->mm, pmd); >>> + if (!pmd_present(*pmd)) { >>> + spin_unlock(ptl); >>> + return 0; >>> + } >>> + >>> if (!pmd_huge(*pmd)) { >>> spin_unlock(ptl); >>> goto regular_page; >>> --=20 >>> 1.8.3.1