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Fri, 20 Jun 2025 18:24:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 6HJcJlmnVWhUEQAAD6G6ig (envelope-from ); Fri, 20 Jun 2025 18:24:25 +0000 Date: Fri, 20 Jun 2025 19:24:23 +0100 From: Pedro Falcato To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, Andrew Morton , Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , Dan Williams , Alistair Popple , Matthew Wilcox , Jan Kara , Alexander Viro , Christian Brauner , Zi Yan , Baolin Wang , Lorenzo Stoakes , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn Subject: Re: [PATCH RFC 03/14] mm: compare pfns only if the entry is present when inserting pfns/pages Message-ID: References: <20250617154345.2494405-1-david@redhat.com> <20250617154345.2494405-4-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250617154345.2494405-4-david@redhat.com> X-Rspamd-Queue-Id: 05CCDC0007 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: qng3qcj6xazdipg7qy38uxconynqe3ew X-HE-Tag: 1750443868-843629 X-HE-Meta: U2FsdGVkX1+AA82IZn9dD/bqAqAH5Zs5Wjv3Lq2olhmQxhEryTkzCOJxJN4T0ZbunwEv2XIGCD72ia8AIgppJ0befNv5sKdPDTLTUmSOdABJvslbiUiEraDVjoQ+L3W/+Shl3lUgMrAVST5Vxku3Rwu1W8E9Ezh1t/1DJdehJq/ONCrZ+7yBVdEgSuuyjpG1Si4IWomTlvvxEJ+igsQZ4T/GRrAUCM/ZbfzU0RfN8w0x4CG/xyw+u+kUQNLAZNYdiOWijPwZGV+d9NcU3wHn3FVZ/Hd8GmVn+l6yb8BB770UNMkLXsHF1I5hdUAB1eWF2AsjXWE4O4mRCMnOwO1zseVa7dhfpskOb+IjizMUJnAiRwMyUOhQpxF77P3X2OI8C6zbi+lrKUZyc5Ok2uMD30zruPpcaIt9dpAOhkKk8VCy+XoMEwCpdUn6i1ZnNzxhn3PN1KL8/o1aRr2Kay49eZ01l7GjEVkoiBs3jJJHx0bGN9tPSZ/LVExICdRe5XniBwHqNKqnldYxzSGIz+9s+2bCNWRMpdoeGuucSQlny9e++rVjtTNihNEchg0ZqNKFqKSy6128I9HRkmRSLjAjKg3PO5jK7hk6mMcjefom0L9XxAURD2W5316eheiYsvPFu1yM+Q+jXu3lRsIexDeaekcrhs13STZGDy6WIOrlfrmjZ5ZIJ0k6vjH6QasyjUo8AyGxhMVRLVmZrvKGlLwCMUtSMIi3w+qLJUvaBAGAmV6YSq9z+gQ7qUrHHR7BN1iJUQ+A729+rEbcS7Sg0oTH/+qqOS5ez3abG1xvUejaM6xXCLihFjJE3ToX1pk3YjgtdSmIfwTpZ8GjFrAz4b1B+IesXbhknLpusC+SMvHkI2trCRXwwbdHAyLKn0yK4f6EAJ6618yaXBVPkL4VG9MxcDYl0RjbOOqwbFE26w9z3qv5/Fhb5S13TrzANDt2dPkdlo8pAdR242Xx6t2c1p7 D3oiylcq NO8RodhFBxPMiCjJSxWH1eAsILctJiVp0FRKKgr2nFrtnPDW0bjEBqrAYdXnOYmN6U9WZCDH/Udv2HzbLtW4e9Oauq1QsT8+hmhjy50EtnhhYbvBCcopXXVTzSFlYV7LicjdVnrXjVOp0pPHOy9WOIoUJTsp4uZJvdTPEhb+r+rBnWp74caknq0ig3lsFhftk567utcb2eMT4j93QyJTAOl7mGvm06apRa0QNa2qV4SCy0FCp2Led+CihcP0OvA2oZos1wvGwB1L/2mf95oUXMQWOKZNmLeV5GS+MMjMFopxJEsXKc7WnHf1z06dI8V6tVLCvfDWRJOHeclI= 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: List-Subscribe: List-Unsubscribe: On Tue, Jun 17, 2025 at 05:43:34PM +0200, David Hildenbrand wrote: > Doing a pte_pfn() etc. of something that is not a present page table > entry is wrong. Let's check in all relevant cases where we want to > upgrade write permissions when inserting pfns/pages whether the entry > is actually present. > > It's not expected to have caused real harm in practice, so this is more a > cleanup than a fix for something that would likely trigger in some > weird circumstances. Couldn't we e.g have a swap entry's "pfn" accidentally match the one we're inserting? Isn't that a correctness problem? > > At some point, we should likely unify the two pte handling paths, > similar to how we did it for pmds/puds. > > Signed-off-by: David Hildenbrand Nice little cleanup, thanks. Reviewed-by: Pedro Falcato -- Pedro