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[2003:d8:2f1f:3f00:731a:f5e5:774e:d40c]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf270fbd01sm19047514f8f.13.2025.09.02.01.23.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 Sep 2025 01:23:52 -0700 (PDT) Message-ID: <05f628ba-c24b-4180-87be-e5a577dc4e4d@redhat.com> Date: Tue, 2 Sep 2025 10:23:51 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [Patch v2] selftests/mm: check content to see whether mremap corrupt data To: Wei Yang Cc: Zi Yan , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org References: <20250831022701.2595-1-richard.weiyang@gmail.com> <61E58B7C-23D0-49FE-8D0C-CE0B672114E2@nvidia.com> <0a0b0018-9427-4201-bf53-6aeb251bc482@redhat.com> <1D88E773-C11E-4F28-A13A-1A681898198B@nvidia.com> <5a796574-0a3c-4040-b0bc-3ff757402759@redhat.com> <20250902025112.d2n3o4imeptppctd@master> <20250902081342.rthx5sopowmg4hyb@master> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 55185C000F X-Stat-Signature: tjj8c43hr3gzyebud5z1593fqybsqtkr X-Rspam-User: X-HE-Tag: 1756801436-219382 X-HE-Meta: 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 2QcAx0Sb 8/qZkUk7jBpcQaKqTSMkk120qP5l5IcvY6O2dlDyXnCB7ZieqNrO+i5/kK3G8J8ubDwSOTctUVTs7Y84szuN0EKulwbeJyve/5rQQPak4pDNccyp6rnlU7iBrSf874G5RF+Dz7Jca7aBbJ/huCMhpvaV/dG+TXKJFoOJ7D1AKDqHMGiTRkd+OM1F5kKRbCxmbgvlOoyUhJMakYpPpmq2lPfedB7S0KXbg5JoHoxdTwRmDps++VKvhS6U/huJswPS3rNUZOwgWSdMUNW4oQbWHKgD9liLUHjS8CBpFq2v/CGhjeMSHl4nhzKxadLOhDO8t5MmxgZGvMjWAGLg0Dl0a8ERCzwWoS6sWxQbqc9a4d1ktLgJtxUi3zfFOOXvV/cqFZU6B6A1uGsddYqlHgABW8YxZoNhN9hnurj0ywfkCpIMAtawhIs6srOj6rScDmeXeOx/XJ1gq3ZzeAUU= 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: List-Subscribe: List-Unsubscribe: On 02.09.25 10:13, Wei Yang wrote: > On Tue, Sep 02, 2025 at 09:49:48AM +0200, David Hildenbrand wrote: >>>> + /* >>>> + * To challenge spitting code, we will mremap page[x] of the >>>> + * thp[x] into a smaller area, and trigger the split from that >>>> + * smaller area. This will end up replacing the PMD mappings in >>>> + * the thp_area by PTE mappings first, leaving the THPs unsplit. >>>> + */ > > This confuse me a little. How about move "and trigger the split from that > smaller area" to the end? So that I know mremap convert to pte-mapping and > leave thp unsplit. Then we do the split. > After spleeping over it, what about the following? + /* + * To challenge spitting code, we will mremap a single page of each + * THP (page[i] of thp[i]) in the thp_area into page_area. This will + * replace the PMD mappings in the thp_area by PTE mappings first, + * but leaving the THP unsplit, to then create a page-sized hole in + * the thp_area. + * We will then manually trigger splitting of all THPs through the + * single mremap'ed pages of each THP in the page_area. + */ -- Cheers David / dhildenb