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Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.151.185] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: AE12380003 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 9eg3w3jjea8yfgkkw6z4t3njij87bs1t X-HE-Tag: 1689560937-586022 X-HE-Meta: U2FsdGVkX18upjZdxuzmhU9WhRKmdZVP8r7DNBI8XZ42Oka9Njeprxp0kVMBVdopIOx8q1taMIkEERMbKZB3uvLymit/rqXIyN5wmotWcyyNJVXwIBHwlsIUdVQgNrdZB8VCFdt39IY54/0RG/6gryHpnwhZ/jL1c81t+4ThVpFlDFmERi+onxmlNNA9yhGsiKOKIbsQ338KUbpcNmCuujISROP8mtPA2Worl9MOKhek9Js4RzqW8d5zkMZEJS3vIXDRCzZCJXL77RrTwe48CNvyTKWg6ntL7qsqjySPUIJ/yb4zr79mFwz+77Bvt1q70xJbQKhmEHA+0fHbbgql0UjzxkNf12e7GRvhR1T5mdu+96E73TOFnFRPK+i1arjy16OhFSwTt5l0PtW4lIKNrrP5iQRw51rvxKo8a3ZiqrWG4i2P/gftzTNbopELTbK0/g/iMbd2wlSyIshNbjW1+OHaesQXmUxRBI4+Z4mVucfwZJI5aj52CEtCAItTS7SLSMgKIRobkcToaAKhLX0CEaitVQd0dtXmDezDX1j9YnVPHOVikDtr1y6G7mOLbHfRFkSnntyLyrG67LjzVCg5uHxBruNE+nFLqFGry4ttkeKzQNiAI76I4+FI5zrCRDrPh8dxZX/LePf0DCZDjIiw8BBzCdZIkiS7MQ8ozZLNGwbgM7XaEZNWSamJ9nhKCeYsctyjTH6P71M8le/LUqk3MYhME4rb4h06p7iQe5QzmO4R5KRmriJ9NiDxUYjsfLp2MEPUGs8R5HR2wpJb0E16ibetSMgbu08WjUxQCV1e1Ov5GIqPK0sJlR2Wk8Qr0ny0EYPGiTyjZILt10rpeunOe1DArlTINeh7zslsdinFiIFBlnuc56zgZqrPXacix9GcgMkZ8ujlis620bT1uICj8gOHxbfMaoD9IP3pNKdwJ5fSZL4E2dDjbMDOjHj4dAHVelTGpuJnnL2T3HT6FpV OkuZdzHO oOlpjL8VPNV3Lrws2WVortAfLgV5nbrvmjrG/vyHGTNf6oGTn/IfOSBzOeg8/J1m8334fAuEFfY3Vxp2218YNjx2u8rbF3NkUlb9mFl2cG8UqKm+7c7+Uo2E+4gpm+npPqCtEps7auJRgxQtno/5o53dtCQxIJ6kllQ9GUXettjf7MJzsFe97YipszNpqBOGHoucHcEpM6zX4YmQ= 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 2023/7/15 11:56, Matthew Wilcox wrote: > On Sat, Jul 15, 2023 at 11:28:02AM +0800, Miaohe Lin wrote: >> When page table locked is held, the page can't be freed from under us. > > But the page isn't mapped into the page table ... there's a swap entry > in the page table, so I don't think your logic holds. > IIUC, device_private_entry will hold one page refcnt when it's set to page table. And there's similar code in do_swap_page(): vm_fault_t do_swap_page(struct vm_fault *vmf) if (unlikely(non_swap_entry(entry))) { if (is_device_private_entry(entry)) /* * Get a page reference while we know the page can't be * freed. */ get_page(vmf->page); pte_unmap_unlock(vmf->pte, vmf->ptl); ret = vmf->page->pgmap->ops->migrate_to_ram(vmf); put_page(vmf->page); ... If my logic doesn't hold, do_swap_page() will need to fix the code. Or am I miss something? Thanks Matthew.