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Fri, 4 Sep 2020 06:03:38 +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 442511045; Thu, 3 Sep 2020 23:03:38 -0700 (PDT) Received: from [10.163.70.23] (unknown [10.163.70.23]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6D4F43F71F; Thu, 3 Sep 2020 23:03:36 -0700 (PDT) Subject: Re: [PATCH v4 11/13] mm/debug_vm_pgtable/pmd_clear: Don't use pmd/pud_clear on pte entries To: "Aneesh Kumar K.V" , linux-mm@kvack.org, akpm@linux-foundation.org Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org References: <20200902114222.181353-1-aneesh.kumar@linux.ibm.com> <20200902114222.181353-12-aneesh.kumar@linux.ibm.com> From: Anshuman Khandual Message-ID: <8251b4b6-63ee-cbf8-63dd-c0031a010a4b@arm.com> Date: Fri, 4 Sep 2020 11:33:04 +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: <20200902114222.181353-12-aneesh.kumar@linux.ibm.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 7D8DF180B3C83 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam01 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 09/02/2020 05:12 PM, Aneesh Kumar K.V wrote: > pmd_clear() should not be used to clear pmd level pte entries. > > Signed-off-by: Aneesh Kumar K.V > --- > mm/debug_vm_pgtable.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 26023d990bd0..b53903fdee85 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -196,6 +196,8 @@ static void __init pmd_advanced_tests(struct mm_struct *mm, > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_young(pmd)); > > + /* Clear the pte entries */ > + pmdp_huge_get_and_clear(mm, vaddr, pmdp); > pgtable = pgtable_trans_huge_withdraw(mm, pmdp); > } > > @@ -319,6 +321,8 @@ static void __init pud_advanced_tests(struct mm_struct *mm, > pudp_test_and_clear_young(vma, vaddr, pudp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_young(pud)); > + > + pudp_huge_get_and_clear(mm, vaddr, pudp); > } > > static void __init pud_leaf_tests(unsigned long pfn, pgprot_t prot) > @@ -442,8 +446,6 @@ static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp, > * This entry points to next level page table page. > * Hence this must not qualify as pud_bad(). > */ > - pmd_clear(pmdp); > - pud_clear(pudp); > pud_populate(mm, pudp, pmdp); > pud = READ_ONCE(*pudp); > WARN_ON(pud_bad(pud)); > @@ -575,7 +577,6 @@ static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp, > * This entry points to next level page table page. > * Hence this must not qualify as pmd_bad(). > */ > - pmd_clear(pmdp); > pmd_populate(mm, pmdp, pgtable); > pmd = READ_ONCE(*pmdp); > WARN_ON(pmd_bad(pmd)); > Why pxxp_huge_get_and_clear() cannot be called inside pxx_populate_tests() functions itself ? Nonetheless, this does not seem to cause any problem.