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[70.30.145.63]) by smtp.gmail.com with ESMTPSA id b3-20020ac85bc3000000b003bfb820f17csm575151qtb.63.2023.03.02.14.29.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 14:29:51 -0800 (PST) Date: Thu, 2 Mar 2023 17:29:50 -0500 From: Peter Xu To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Mike Rapoport , Andrea Arcangeli , Jerome Glisse , Shaohua Li Subject: Re: [PATCH v1] mm/userfaultfd: propagate uffd-wp bit when PTE-mapping the huge zeropage Message-ID: References: <20230302175423.589164-1-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20230302175423.589164-1-david@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: autfryt39hdf9oetnirkuoiq6j9qpnuo X-Rspamd-Queue-Id: CEF7F2000B X-HE-Tag: 1677796194-498245 X-HE-Meta: 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 RugIElS/ +uSS8Tk7y56rD1UIrCxgkG7bFpdqjiIh4cgEDXqY1VnuBsTpX9sNBXIab1jqavA2FHkB9B43+/c5ZwJke1+Jgv2+adb2LLxWycnzMtn3bd6WZFQticn2g9+4cfBiXCJM1SJqrBz8hc7EM2aUDdxYEqgiLrPdR0B40+vWPoiqyzWaWtiD0PIZKB7FJhArMgFq1P+drOBrwvgIkIUSx7JM00zHr5Or2e6DfhVuf4pNxfzlhJ0Y+APF0H1RqR3nnxiL2xijdR2HOD5Khu3sbynT4wpG2QpLDJ2OFLO7W0pqw3OtImjXNsW/ytclqxZgKJ0Bq4r/53NLvxDAdgmnhfpObYI08xJ2jR2G9Qj58Ca2mj6Q4CEGsS1UOuQ2tNdhUtmJMGmRIY1n+TyRsIFxtwhRVcr475A== 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 Thu, Mar 02, 2023 at 06:54:23PM +0100, David Hildenbrand wrote: > Currently, we'd lose the userfaultfd-wp marker when PTE-mapping a huge > zeropage, resulting in the next write faults in the PMD range > not triggering uffd-wp events. > > Various actions (partial MADV_DONTNEED, partial mremap, partial munmap, > partial mprotect) could trigger this. However, most importantly, > un-protecting a single sub-page from the userfaultfd-wp handler when > processing a uffd-wp event will PTE-map the shared huge zeropage and > lose the uffd-wp bit for the remainder of the PMD. > > Let's properly propagate the uffd-wp bit to the PMDs. Ouch.. I thought this was reported once, probably it fell through the cracks. Acked-by: Peter Xu Thanks, -- Peter Xu