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[2003:cb:c706:1300:6f08:1748:eba7:b2a9]) by smtp.gmail.com with ESMTPSA id n4-20020a5d51c4000000b002efb55de21dsm10542399wrv.103.2023.04.11.07.18.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Apr 2023 07:18:58 -0700 (PDT) Message-ID: <81a2070a-f7aa-2185-8211-26b57815e968@redhat.com> Date: Tue, 11 Apr 2023 16:18:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.1 Subject: Re: [PATCH] mm/huge_memory: conditionally call maybe_mkwrite() and drop pte_wrprotect() in __split_huge_pmd_locked() To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org References: <20230411141529.428991-1-david@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230411141529.428991-1-david@redhat.com> 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-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: B0A9940005 X-Stat-Signature: awzkgn598bxmchnzk85skjzgjzsbuupo X-Rspam-User: X-HE-Tag: 1681222742-446401 X-HE-Meta: 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 IkMTv8aW S5j1ahkT/oUJaYOzG/qanr+zigazdvt9asDpNi1zJqpbldiepzrTV9zqaMwFsPNBE8vuRRVukwwAnjkJj641rbdXj36oUsKSjj60neZkRgkGvlNeQlqjYZJ7vcLuqPE/H4iLV0Ium/JOEV8EIzD6WVcoDwc4AwllU0w0qeK7CBqLdIo0mOjLAkBQ6Hy2UxilTi73N9h/F1a8YK3h2k85o97dBM8PCGaR3F3xb7/i2WY/9f9FvabQTcLssB3ar3dRJXwCgkpkxen56NC32t0qTCUzFmWO1jauWPS+txpYKWyblokfh6OHLN0vaLCbQsCWZ3xmkURtI47BvrH+AYpZ047A6Lzi/3MYDyndIRSEHhyO2pRHApaytZkOCzUzY2YR6Mk/xq44PLHk3aXxSod3IaS3l1WEtv+N4qC+6aKlrq4tV0vT7OYRsPRExApaJN0/XIC+7vZjcvvLFJQFzYUvOY1+YVg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.006406, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 11.04.23 16:15, David Hildenbrand wrote: > No need to call maybe_mkwrite() to then wrprotect if the source PMD was not > writable. > > It's worth nothing that this now allows for PTEs to be writable even if > the source PMD was not writable: if vma->vm_page_prot includes write > permissions. > > As documented in commit 931298e103c2 ("mm/userfaultfd: rely on > vma->vm_page_prot in uffd_wp_range()"), any mechanism that intends to > have pages wrprotected (COW, writenotify, mprotect, uffd-wp, softdirty, > ...) has to properly adjust vma->vm_page_prot upfront, to not include > write permissions. If vma->vm_page_prot includes write permissions, the > PTE/PMD can be writable as default. > > This now mimics the handling in mm/migrate.c:remove_migration_pte() and in > mm/huge_memory.c:remove_migration_pmd(), which has been in place for a > long time (except that 96a9c287e25d ("mm/migrate: fix wrongly apply write > bit after mkdirty on sparc64") temporarily changed it). > > Signed-off-by: David Hildenbrand > --- Ignore this one, it's a duplicate of 6/6 and I forgot to delete that patch before triggering git send-email ... -- Thanks, David / dhildenb