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[2003:cb:c702:2e00:b9ea:114c:a3f5:327e]) by smtp.gmail.com with ESMTPSA id t14-20020a05600c198e00b003cfd4a50d5asm7387447wmq.34.2022.12.09.00.07.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 09 Dec 2022 00:07:45 -0800 (PST) Message-ID: <6209d614-b1f2-4501-6b8a-6d4095c309eb@redhat.com> Date: Fri, 9 Dec 2022 09:07:44 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: [PATCH v1] mm/userfaultfd: enable writenotify while userfaultfd-wp is enabled for a VMA To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ives van Hoorne , stable@vger.kernel.org, Andrew Morton , Hugh Dickins , Alistair Popple , Mike Rapoport , Nadav Amit , Andrea Arcangeli References: <20221208114137.35035-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 83276C0014 X-Rspamd-Server: rspam01 X-Stat-Signature: w8ejr9h6q34tsh4p8xuf465cguemwdij X-HE-Tag: 1670573269-993171 X-HE-Meta: U2FsdGVkX19jCm1fmd5eK0vwsL+l5+tnB5pffCD59GGHUuT3+CRfM+uOsMC3tmZHFxKji66SfUhM/Sj4y5Dty59xX36l/2zeaeQUsF7MPa6vTILGDMvNlULS9I4XPF5cbx4FPoOPjZKmDlQxwXhw7rqa6samVNzKULAjaGYDBgbg9iGVFd2Xh7z0O6jtMPKabLilNLJKPb7/zYPOLwMRVxIkzv4SgsyPaSi7z6VbDUf6O5RLI4DtqmH2Ct/i6aWE+lkHVsWhkrBQE0/IsHformjQfiJ1LmiltYLvXomzqUnDNwZDLBZSJl8apml/qggcXO45DGvRKt0xyePgUhRLlbCufKTvQfQC11lnjnr/WIunsqsvsviP9vypiwlreb3FF+5Np1HdLky136JqYn5XmaCRsIBPUqIhTJgzK+/k3ztKMBUaABxhgf6yQw1R0vmv5PU3u4gwgudM2ydmEmVj2gZlkbQlZfq7PyCwrKAZViAeo4+gwE8NsXVpToepS3BhFQ2nGyFn5ptBRN6n8mSloI8Bke6iWKD5oFbg2rCF2hC9BsSidcqMBhopd5seCzGOvoBPTROl28BZ7AoVel3TEU+obEpH3OQ20oiDg4fRJqdR3zOlB4eJju07ruYVzu4H5Ql9PDy+3J9SB5LfwO5npJdO7uc3sbdiTew5tsu30QN9h+kD4kXw3522Cct8gsrGKMLMNrvcuigR6TkeWUT8sagZ1XvxbX769V91KC3vymJ7MvhHw6SVvk5+b7FiJUjJPMAMUQT/ro4KehL72I8CUzmQN91jlK+CMKuh9xWtr6SD7os9TRDZcqtMzd7LKZDmIQ5CGaqegNnOLrksPUyZEbTWmqNUb0KyymNuRDP5u00+HIx3BTSIrcMECHhSRov7tbNoeDe5uj9CKGZ2yXB2JWL7HHr4jThsHE8JB4N0E2bohlte1TBQcm/hR4dqH3O4mDcuou1i8RfuXrSPfW4 C6rpU92G ifs8sgkt4E3su+RJ4N+RGaJUsN1ATDSLR1xcXydSgQLlMwmhWsUJkeKnbJAM5HPWMkp+UtUbojQ4Pe0Z9U+62A9gogvW1/HUhEgzGVb6wMVQjzwl0NyyqRbreWOMh0MXoTijRdJS09BHssUZmLEGOaFN40tMjbbMCXOnSAj8lVmw0vvpylMNM0rAu9WA91Iu0HwLAuB/1MRzRI1VMlFZlKSZQJg== 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 08.12.22 21:21, Peter Xu wrote: > On Thu, Dec 08, 2022 at 03:06:06PM -0500, Peter Xu wrote: >> On Thu, Dec 08, 2022 at 05:44:35PM +0100, David Hildenbrand wrote: >>> I'll wait for some more (+retest) before I resend tomorrow. >> >> One more thing just to double check: >> >> It's 6a56ccbcf6c6 ("mm/autonuma: use can_change_(pte|pmd)_writable() to >> replace savedwrite", 2022-11-30) that just started to break uffd-wp on >> numa, am I right? >> >> With the old code, pte_modify() will persist uffd-wp bit, afaict, and we >> used to do savedwrite for numa hints. That all look correct to me until >> the savedwrite removal patchset with/without vm_page_prot changes. >> >> If that's the case, we'd better also mention that in the commit message and >> has another Fixes: for that one to be clear. > > Nah, never mind. I think the savedwrite will not guarantee pte write > protected just like the migration path. The commit message is correct. Right, the problem is not the uffd-wp bit getting lost, but the write bit getting set, which is independent of 6a56ccbcf6c6. Thanks for double-checking 6a56ccbcf6c6. -- Thanks, David / dhildenb