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[2003:cb:c713:a600:7ca0:23b3:d48a:97c7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36b367d9576sm4396129f8f.31.2024.07.26.01.04.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 26 Jul 2024 01:04:47 -0700 (PDT) Message-ID: <17256b99-ab26-4f7b-9100-2fc42b233af2@redhat.com> Date: Fri, 26 Jul 2024 10:04:46 +0200 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/2] mm/hugetlb: fix hugetlb vs. core-mm PT locking To: Baolin Wang , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Muchun Song , Peter Xu , Oscar Salvador , stable@vger.kernel.org References: <20240725183955.2268884-1-david@redhat.com> <20240725183955.2268884-3-david@redhat.com> <0067dfe6-b9a6-4e98-9eef-7219299bfe58@linux.alibaba.com> <707d8937-d4c8-43b3-bc19-70f0038522a9@linux.alibaba.com> Content-Language: en-US From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit >> >>> +     * >>> +     * If that does not hold for an architecture, then that architecture >>> +     * must disable split PT locks such that all *_lockptr() functions >>> +     * will give us the same result: the per-MM PT lock. >>> +     */ >>> +    if (huge_page_size(h) < PMD_SIZE) >>> +        return pte_lockptr(mm, pte); >>> +    else if (huge_page_size(h) < PUD_SIZE) >>>           return pmd_lockptr(mm, (pmd_t *) pte); >> >> IIUC, as I said above, this change doesn't fix the inconsistent lock for >> cont-PMD size hugetlb for GUP, and it will also break the lock rule for >> unmapping/migrating a cont-PMD size hugetlb (use mm->page_table_lock >> before for cont-PMD size hugetlb before). > > After more thinking, I realized I confused the PMD table with the PMD > entry. Therefore, using the PMD table's lock is safe for cont-PMD size > hugetlb. This change looks good to me. Sorry for noise. > Thanks for the review, highly appreciated! -- Cheers, David / dhildenb