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b=na5wZgH5KcpLTANe9sXcc5m1+sTkRkzEtr3h7ep/PCZsn8vxVGugP8DwJn0cw7mOX BXG0fBcJsMXU/+5E1uJ0637xaaNXg/vm2GGvFyJVhtc2Nc4FiQGC5rhjWf5FEyOnPC L9JzEdgOxMUu78S8j/OdI5D3A8z2825bdRFN2SGM82z7hyr3c4UveJA42ux1+ZY0d2 bc8FM4c+2MVN7TvCIcbakraLDa7EAtRPnfHglnPdLCmxq7dkPWRUC2E6jmkMal7KhZ RmP9ZWHgsmaGlvPbSQNJTFpvJNcDudSQjQ77G/Ubw6Aslw4s5fXxoqZWTbfUU36nJU sLs22rRTNGhUw== Message-ID: <34d76192-d00b-409a-8a1b-11a6c8433d66@zytor.com> Date: Tue, 20 Feb 2024 10:46:37 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 0/3] Cleanup for PAT Content-Language: en-US To: mawupeng , akpm@linux-foundation.org, dave.hansen@linux.intel.com, luto@kernel.org, tglx@linutronix.de, peterz@infradead.org, hpa@zytor.com Cc: linux-kernel@vger.kernel.org, x86@kernel.org, bp@suse.de, mingo@redhat.com, rdunlap@infradead.org, bhelgaas@google.com, linux-mm@kvack.org References: <20240220034835.507022-1-mawupeng1@huawei.com> <07d43633-d707-415d-a662-ecd3a50b12ae@zytor.com> <1f98fd3a-9a2c-437e-8e86-8c5f575917df@huawei.com> From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6C9B5180005 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: itww8njf73s38okq9113swrssxhm687j X-HE-Tag: 1708454818-578428 X-HE-Meta: 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 h7VGf3Cw +Gvd3xvB1fkTj49sBfKlDrxmAuV/ZsYEY9sJdD0KKfO8G2WPWUCV3ypIuJLcDM+H6MIgmcHy2+JM+UuufuI2nEbYlDwWkfbjozAh4XEuM648D+704lJlSKcbb+ed/2KmNpapEo0mRSTz/Kuyn+qHmN490V6UCgUJ6QQwG1Cx48F2c0UV7RFoF0kaVNr6bEMhdiq9nZVwBtioG4E8c/a4PZJd+j8CWnEgPMIpG 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 2/20/2024 1:06 AM, mawupeng wrote: > On 2024/2/20 16:37, Xin Li wrote: >> On 2/19/2024 7:48 PM, Wupeng Ma wrote: >> follow_phys() was introduced in commit 28b2ee20c7cba ("access_process_vm >> device memory infrastructure") in 2008 for getting a physical page address >> for a virtual address, and used in generic_access_phys(). And later it's >> used in x86 PAT code. >> >> Commit 03668a4debf4f ("mm: use generic follow_pte() in follow_phys()") made >> follow_phys() more of a wrapper of follow_pte(), and commit 96667f8a4382d >> ("mm: Close race in generic_access_phys") replaced follow_phys() with >> follow_pte() in generic_access_phys(). And the end result is that >> follow_phys() is used in x86 PAT code only. > > Thanks for the explanation. I have a better understanding of the history of > this function. > "git blame" tells the story. >> >> As follow_phys() in untrack_pfn() can be replaced with follow_pfn(), then > > Yes, this can be replaced with follow_pfn(). > >> maybe we don't have to keep follow_phys(), and just use follow_pte() in >> track_pfn_copy()? > > As follow_phys() will return unsigned long *prot which is need in track_pfn_copy(), > we need to do something with this. Commit 96667f8a4382d did that already. > Can we replace follow_pfn with follow_phys()? Sorry, I don't get your point. Thanks! Xin