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[188.193.207.173]) by smtp.gmail.com with ESMTPSA id e9-20020a170906c00900b006d4a45869basm2087116ejz.199.2022.03.25.02.06.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 25 Mar 2022 02:06:58 -0700 (PDT) Message-ID: Date: Fri, 25 Mar 2022 10:06:57 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.5.0 Subject: Re: [RFC 3/3] scsi: target: tcmu: Support zero copy Content-Language: en-US To: Xiaoguang Wang , linux-mm@kvack.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org Cc: linux-block@vger.kernel.org, xuyu@linux.alibaba.com References: <20220318095531.15479-1-xiaoguang.wang@linux.alibaba.com> <20220318095531.15479-4-xiaoguang.wang@linux.alibaba.com> <94b00e49-5efb-658f-3142-42e7cc551d19@gmail.com> <57da7e54-f582-3b10-52a9-5166adacf4e6@linux.alibaba.com> From: Bodo Stroesser In-Reply-To: <57da7e54-f582-3b10-52a9-5166adacf4e6@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: cd7y5eo8nrt9o1z6sa41qzpo4q1xh7rf Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=euZVYebC; spf=pass (imf22.hostedemail.com: domain of bostroesser@gmail.com designates 209.85.208.42 as permitted sender) smtp.mailfrom=bostroesser@gmail.com; dmarc=pass (policy=none) header.from=gmail.com X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E20A3C001F X-HE-Tag: 1648199219-154445 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000463, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 23.03.22 15:33, Xiaoguang Wang wrote: ... snip ... >> What happens if the tcmu device currently is not open / mapped? > I'm not sure how it will happen. > But we may check whether udev->vma has a valid value. If yes, > it'll enter tcmu_cmd_zerocopy_map(). > Yeah, but what I also wanted to suggest is, that if userspace maps the uio device while zero copy cmds already being in the ring, you have to iterate over those cmds and populate the mapping. Bodo