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bh=+AFwl6Tdw7lCOQEeBIBUL2ttLPJdObo/6MKBRhbNoOU=; b=L/mcwp/1lxAsuKQOejMd0P3Kss9LJ1IGnk4bB3EygH2fbzFnrDNkBpD31Gs5r0pAmsC7OR oQa49IoHHOj+HnNeeWsUWMZfBevT+MtNrOsG1L93GICXfbdC6MS9pmvDopeC+Zk2HCqSvJ VCwZha73xfKsbywlo3n+qe/9yg2rYec= X-Stat-Signature: pzq7rqqcrteyzbcrwu7ixu9mwptg7kte X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=N4e5iqnu; spf=pass (imf23.hostedemail.com: domain of fengwei.yin@intel.com designates 192.55.52.43 as permitted sender) smtp.mailfrom=fengwei.yin@intel.com; arc=reject ("signature check failed: fail, {[1] = sig:microsoft.com:reject}"); dmarc=pass (policy=none) header.from=intel.com X-Rspamd-Queue-Id: 0FA06140082 X-Rspamd-Server: rspam03 X-HE-Tag: 1660788059-178283 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 8/18/2022 9:55 AM, Miaohe Lin wrote: >>>> /* >>>> * The memory barrier inside __SetPageUptodate makes sure that >>>> * preceding stores to the page contents become visible before >>>> * the set_pte_at() write. >>>> */ >>>> __SetPageUptodate(page); >>> IIUC, the case here we should make sure others (CPUs) can see new page’s >>> contents after they have saw PG_uptodate is set. I think commit 0ed361dec369 >>> can tell us more details. >>> >>> I also looked at commit 52f37629fd3c to see why we need a barrier before >>> set_pte_at(), but I didn’t find any info to explain why. I guess we want >>> to make sure the order between the page’s contents and subsequent memory >>> accesses using the corresponding virtual address, do you agree with this? >> This is my understanding also. Thanks. > That's also my understanding. Thanks both. I have an unclear thing (not related with this patch directly): Who is response for the read barrier in the read side in this case? For SetPageUptodate, there are paring write/read memory barrier. Regards Yin, Fengwei