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[24.61.119.116]) by smtp.gmail.com with ESMTPSA id h18-20020ac846d2000000b003a55fe9f352sm5713126qto.64.2022.12.12.05.22.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Dec 2022 05:22:20 -0800 (PST) Date: Mon, 12 Dec 2022 08:22:26 -0500 From: Brian Foster To: Al Viro Cc: Nhat Pham , akpm@linux-foundation.org, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, willy@infradead.org, kernel-team@meta.com Subject: Re: [PATCH v2 3/4] cachestat: implement cachestat syscall Message-ID: References: <20221205175140.1543229-1-nphamcs@gmail.com> <20221205175140.1543229-4-nphamcs@gmail.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Queue-Id: C5850A001F X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: yswm7huodtshssqr5ycnbshh3bcyo45k X-HE-Tag: 1670851345-898160 X-HE-Meta: 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 YcnGTalH E9qZ9a7DghL9sDb9oPXJCfjbi0XOL/JD5ja8cp/n1tYJQmq0icNXIZRqkNTpDAwqlAS4aBC58DNjcYGwlM76+SiCk/4Rl9KIetsv+gFK/50eGtvs= 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 Sat, Dec 10, 2022 at 11:51:32PM +0000, Al Viro wrote: > On Mon, Dec 05, 2022 at 09:51:39AM -0800, Nhat Pham wrote: > > > + if (!access_ok(cstat, sizeof(struct cachestat))) > > + return -EFAULT; > > What for? You are using copy_to_user() later, right? > > > + f = fdget(fd); > > + if (f.file) { > > It would be easier to read if you inverted the condition here. > Seconded.. I mentioned the same the last time I looked at this. On looking again, perhaps it might even make sense to create a filemap_cachestat() to split up the syscall bits from the associated map walking bits..? That subsequently raises the question of whether a new .c file is really necessary.. Brian