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([2605:e000:100e:8c61:ff2c:a74f:a461:daa2]) by smtp.gmail.com with ESMTPSA id h65sm19881667pfb.210.2020.08.17.06.58.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Aug 2020 06:58:55 -0700 (PDT) Subject: Re: [PATCH RESEND] block: loop: set discard granularity and alignment for block device backed loop To: Ming Lei Cc: linux-block@vger.kernel.org, Coly Li , Hannes Reinecke , Xiao Ni , "Martin K . Petersen" , Evan Green , Gwendal Grignou , Chaitanya Kulkarni , Andrzej Pietrasiewicz , Christoph Hellwig , stable@vger.kernel.org References: <20200817100130.2496059-1-ming.lei@redhat.com> From: Jens Axboe Message-ID: Date: Mon, 17 Aug 2020 06:58:53 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200817100130.2496059-1-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 8/17/20 3:01 AM, Ming Lei wrote: > In case of block device backend, if the backend supports write zeros, the > loop device will set queue flag of QUEUE_FLAG_DISCARD. However, > limits.discard_granularity isn't setup, and this way is wrong, > see the following description in Documentation/ABI/testing/sysfs-block: > > A discard_granularity of 0 means that the device does not support > discard functionality. > > Especially 9b15d109a6b2 ("block: improve discard bio alignment in > __blkdev_issue_discard()") starts to take q->limits.discard_granularity > for computing max discard sectors. And zero discard granularity may cause > kernel oops, or fail discard request even though the loop queue claims > discard support via QUEUE_FLAG_DISCARD. > > Fix the issue by setup discard granularity and alignment. Applied, thanks. -- Jens Axboe