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([2601:647:4000:d7:597d:a863:13de:4665]) by smtp.gmail.com with ESMTPSA id h64sm6616093pfg.191.2020.03.28.12.31.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 28 Mar 2020 12:31:09 -0700 (PDT) Subject: Re: [PATCH v11 23/26] block/rnbd: server: sysfs interface functions To: Jack Wang , linux-block@vger.kernel.org, linux-rdma@vger.kernel.org Cc: axboe@kernel.dk, hch@infradead.org, sagi@grimberg.me, leon@kernel.org, dledford@redhat.com, jgg@ziepe.ca, danil.kipnis@cloud.ionos.com, rpenyaev@suse.de, pankaj.gupta@cloud.ionos.com References: <20200320121657.1165-1-jinpu.wang@cloud.ionos.com> <20200320121657.1165-24-jinpu.wang@cloud.ionos.com> From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: <8ecc1c47-bad0-dadb-7861-8776b89f0174@acm.org> Date: Sat, 28 Mar 2020 12:31:08 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200320121657.1165-24-jinpu.wang@cloud.ionos.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 2020-03-20 05:16, Jack Wang wrote: > This is the sysfs interface to rnbd mapped devices on server side: > > /sys/devices/virtual/rnbd-server/ctl/devices// > |- block_dev > | *** link pointing to the corresponding block device sysfs entry > | > |- sessions// > | *** sessions directory > | > |- read_only > | *** is devices mapped as read only > | > |- mapping_path > *** relative device path provided by the client during mapping > > +static struct kobj_type ktype = { > + .sysfs_ops = &kobj_sysfs_ops, > +}; >From Documentation/kobject.txt: "One important point cannot be overstated: every kobject must have a release() method." I think this is something that Greg KH feels very strongly about. Please fix this. > +int rnbd_srv_create_dev_sysfs(struct rnbd_srv_dev *dev, > + struct block_device *bdev, > + const char *dir_name) > +{ > + struct kobject *bdev_kobj; > + int ret; > + > + ret = kobject_init_and_add(&dev->dev_kobj, &ktype, > + rnbd_devs_kobj, dir_name); > + if (ret) > + return ret; > + > + ret = kobject_init_and_add(&dev->dev_sessions_kobj, > + &ktype, > + &dev->dev_kobj, "sessions"); > + if (ret) > + goto err; > + > + bdev_kobj = &disk_to_dev(bdev->bd_disk)->kobj; > + ret = sysfs_create_link(&dev->dev_kobj, bdev_kobj, "block_dev"); > + if (ret) > + goto err2; > + > + return 0; > + > +err2: > + kobject_put(&dev->dev_sessions_kobj); > +err: > + kobject_put(&dev->dev_kobj); > + return ret; > +} Please choose more descriptive names for the goto labels, e.g. put_sess_kobj and put_dev_kobj. > +static ssize_t read_only_show(struct kobject *kobj, struct kobj_attribute *attr, > + char *page) > +{ > + struct rnbd_srv_sess_dev *sess_dev; > + > + sess_dev = container_of(kobj, struct rnbd_srv_sess_dev, kobj); > + > + return scnprintf(page, PAGE_SIZE, "%s\n", > + (sess_dev->open_flags & FMODE_WRITE) ? "0" : "1"); > +} The scnprintf() statement looks overcomplicated. How about the following? return scnprintf(page, PAGE_SIZE, "%d\n", (sess_dev->open_flags & FMODE_WRITE) != 0); > +void rnbd_srv_destroy_dev_session_sysfs(struct rnbd_srv_sess_dev *sess_dev) > +{ > + DECLARE_COMPLETION_ONSTACK(sysfs_compl); > + > + sysfs_remove_group(&sess_dev->kobj, > + &rnbd_srv_default_dev_session_attr_group); > + > + sess_dev->sysfs_release_compl = &sysfs_compl; > + kobject_del(&sess_dev->kobj); > + kobject_put(&sess_dev->kobj); > + wait_for_completion(&sysfs_compl); > +} Why is there a wait_for_completion() call in the above function? I think Greg KH strongly disagrees with such calls in functions that remove sysfs attributes. > +int rnbd_srv_create_sysfs_files(void) > +{ > + int err; > + > + rnbd_dev_class = class_create(THIS_MODULE, "rnbd-server"); > + if (IS_ERR(rnbd_dev_class)) > + return PTR_ERR(rnbd_dev_class); > + > + rnbd_dev = device_create(rnbd_dev_class, NULL, > + MKDEV(0, 0), NULL, "ctl"); > + if (IS_ERR(rnbd_dev)) { > + err = PTR_ERR(rnbd_dev); > + goto cls_destroy; > + } > + rnbd_devs_kobj = kobject_create_and_add("devices", &rnbd_dev->kobj); > + if (!rnbd_devs_kobj) { > + err = -ENOMEM; > + goto dev_destroy; > + } > + > + return 0; > + > +dev_destroy: > + device_destroy(rnbd_dev_class, MKDEV(0, 0)); > +cls_destroy: > + class_destroy(rnbd_dev_class); > + > + return err; > +} Please mention the device class in the description of this patch. Thanks, Bart.