Re: [PATCH v5 22/25] rnbd: server: sysfs interface functions

From: Jinpu Wang <jinpu.wang@cloud.ionos.com>
To: Leon Romanovsky <leon@kernel.org>
Cc: Jack Wang <jinpuwang@gmail.com>,
	linux-block@vger.kernel.org, linux-rdma@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>,
	Christoph Hellwig <hch@infradead.org>,
	Sagi Grimberg <sagi@grimberg.me>,
	Bart Van Assche <bvanassche@acm.org>,
	Doug Ledford <dledford@redhat.com>,
	Danil Kipnis <danil.kipnis@cloud.ionos.com>,
	rpenyaev@suse.de
Subject: Re: [PATCH v5 22/25] rnbd: server: sysfs interface functions
Date: Mon, 23 Dec 2019 09:33:49 +0100	[thread overview]
Message-ID: <CAMGffEnnS_HZVo_5D9O-v=6QYJXoaJ63u39cwFu+aiaNTNXTyA@mail.gmail.com> (raw)
In-Reply-To: <20191223081412.GM13335@unreal>

On Mon, Dec 23, 2019 at 9:14 AM Leon Romanovsky <leon@kernel.org> wrote:
>
> On Fri, Dec 20, 2019 at 04:51:06PM +0100, Jack Wang wrote:
> > From: Jack Wang <jinpu.wang@cloud.ionos.com>
> >
> > This is the sysfs interface to rnbd mapped devices on server side:
> >
> >   /sys/devices/virtual/rnbd-server/ctl/devices/<device_name>/
> >     |- block_dev
> >     |  *** link pointing to the corresponding block device sysfs entry
> >     |
> >     |- sessions/<session-name>/
> >     |  *** sessions directory
> >        |
> >        |- read_only
> >        |  *** is devices mapped as read only
> >        |
> >        |- mapping_path
> >           *** relative device path provided by the client during mapping
> >
> > Signed-off-by: Danil Kipnis <danil.kipnis@cloud.ionos.com>
> > Signed-off-by: Jack Wang <jinpu.wang@cloud.ionos.com>
> > ---
> >  drivers/block/rnbd/rnbd-srv-sysfs.c | 234 ++++++++++++++++++++++++++++
> >  1 file changed, 234 insertions(+)
> >  create mode 100644 drivers/block/rnbd/rnbd-srv-sysfs.c
> >
> > diff --git a/drivers/block/rnbd/rnbd-srv-sysfs.c b/drivers/block/rnbd/rnbd-srv-sysfs.c
> > new file mode 100644
> > index 000000000000..17258156cdf2
> > --- /dev/null
> > +++ b/drivers/block/rnbd/rnbd-srv-sysfs.c
> > @@ -0,0 +1,234 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * InfiniBand Network Block Driver
> > + *
> > + * Copyright (c) 2014 - 2017 ProfitBricks GmbH. All rights reserved.
> > + * Authors: Fabian Holler <mail@fholler.de>
> > + *          Jack Wang <jinpu.wang@profitbricks.com>
> > + *          Kleber Souza <kleber.souza@profitbricks.com>
> > + *          Danil Kipnis <danil.kipnis@profitbricks.com>
> > + *          Roman Penyaev <roman.penyaev@profitbricks.com>
> > + *          Milind Dumbare <Milind.dumbare@gmail.com>
> > + *
> > + * Copyright (c) 2017 - 2018 ProfitBricks GmbH. All rights reserved.
> > + * Authors: Danil Kipnis <danil.kipnis@profitbricks.com>
> > + *          Roman Penyaev <roman.penyaev@profitbricks.com>
> > + *
> > + * Copyright (c) 2018 - 2019 1&1 IONOS Cloud GmbH. All rights reserved.
> > + * Authors: Roman Penyaev <roman.penyaev@profitbricks.com>
> > + *          Jack Wang <jinpu.wang@cloud.ionos.com>
> > + *          Danil Kipnis <danil.kipnis@cloud.ionos.com>
> > + */
> > +
> > +/* Copyright (c) 2019 1&1 IONOS SE. All rights reserved.
> > + * Authors: Jack Wang <jinpu.wang@cloud.ionos.com>
> > + *          Danil Kipnis <danil.kipnis@cloud.ionos.com>
> > + *          Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
> > + *          Lutz Pogrell <lutz.pogrell@cloud.ionos.com>
> > + */
> > +#undef pr_fmt
> > +#define pr_fmt(fmt) KBUILD_MODNAME " L" __stringify(__LINE__) ": " fmt
> > +
> > +#include <uapi/linux/limits.h>
> > +#include <linux/kobject.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/stat.h>
> > +#include <linux/genhd.h>
> > +#include <linux/list.h>
> > +#include <linux/moduleparam.h>
> > +#include <linux/device.h>
> > +
> > +#include "rnbd-srv.h"
> > +
> > +static struct device *rnbd_dev;
> > +static struct class *rnbd_dev_class;
> > +static struct kobject *rnbd_devs_kobj;
> > +
> > +static struct kobj_type ktype = {
> > +     .sysfs_ops      = &kobj_sysfs_ops,
> > +};
> > +
> > +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_del(&dev->dev_sessions_kobj);
> > +     kobject_put(&dev->dev_sessions_kobj);
> > +err:
> > +     kobject_del(&dev->dev_kobj);
> > +     kobject_put(&dev->dev_kobj);
>
> You are using this _del/_put pattern a lot, from what I see
> kobject_put() is the only is needed.
>
> Thanks
Yes, you're right, for these 2 cases, kobject_put is enough, although
kobject_del is harmless here, which will unregister the kobject from
sysfs, and makes the                        kobject "invisible" to
user.

Will remove them next round.
Thanks