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[87.17.106.94]) by smtp.gmail.com with ESMTPSA id s13-20020a170906a18d00b0072af102e65csm5149520ejy.152.2022.08.21.12.12.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 21 Aug 2022 12:12:33 -0700 (PDT) From: "Fabio M. De Francesco" To: Christoph Hellwig , Sagi Grimberg Cc: Chaitanya Kulkarni , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Chaitanya Kulkarni , Keith Busch , Ira Weiny Subject: Re: [PATCH v2] nvmet-tcp: Don't kmap() pages which can't come from HIGHMEM Date: Sun, 21 Aug 2022 21:12:30 +0200 Message-ID: <8107517.T7Z3S40VBb@opensuse> In-Reply-To: <20220821054602.GA25754@lst.de> References: <20220817184519.25141-1-fmdefrancesco@gmail.com> <20220821054602.GA25754@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220821_121250_285022_E9BB4243 X-CRM114-Status: GOOD ( 11.90 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On domenica 21 agosto 2022 07:46:02 CEST Christoph Hellwig wrote: > This introduced tons of pointless over 80 character lines, please stick > to a proper coding style. I'm sorry for this mistake. I'll break those long lines in the next version. > Also or in-kernel I/O wouldn't it make more sense to use a BVEC iter > insted of a KVEC if we have the pages anyway? Or does networking not > support them properly? I must admit I knew practically nothing about this code until I met it while doing my long journey towards kmap() and kmap_atomic() removals. I can say the same for regard to the differences between BVEC iter and KVEC iter. Since you are asking this, today I did some research and read code from other drivers/subsystems, despite this particular issue is out of the scope of my patch. I also read an interesting article in LWN: "The iov_iter interface" at https://lwn.net/Articles/625077/ I may very well be wrong, however I think that iov_iter_kvec() is better suited here. @Sagi, anything to add to this discussion? Thanks, Fabio