Re: [PATCH] rbd: add ioctl for rbd

[Guangliang Zhao <guangliang@unitedstack.com>]

On Mon, Sep 16, 2013 at 08:57:57PM -0700, Sage Weil wrote:

Hi Sage,

> On Mon, 16 Sep 2013, Guangliang Zhao wrote:
> > When running the following commands:
> >     [root@ceph0 mnt]# blockdev --setro /dev/rbd2
> >     [root@ceph0 mnt]# blockdev --getro /dev/rbd2
> >     0
> > 
> > The block setro didn't take effect, it is because
> > the rbd doesn't support ioctl of block driver.
> > 
> > This resolves:
> > 	http://tracker.ceph.com/issues/6265
> > 
> > Signed-off-by: Guangliang Zhao <guangliang@unitedstack.com>
> > ---
> >  drivers/block/rbd.c |   54 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 54 insertions(+)
> > 
> > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> > index 2f00778..9f2057a 100644
> > --- a/drivers/block/rbd.c
> > +++ b/drivers/block/rbd.c
> > @@ -508,10 +508,64 @@ static void rbd_release(struct gendisk *disk, fmode_t mode)
> >  	put_device(&rbd_dev->dev);
> >  }
> >  
> > +static int rbd_ioctl(struct block_device *bdev, fmode_t mode,
> > +			unsigned int cmd, unsigned long arg)
> > +{
> > +	struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
> > +	int ro, ret = 0;
> > +
> > +	BUG_ON(!rbd_dev);
> > +	spin_lock_irq(&rbd_dev->lock);
> > +	if (rbd_dev->open_count > 1) {
> > +		spin_unlock_irq(&rbd_dev->lock);
> > +		ret = -EBUSY;
> > +		goto out;
> > +	}
> > +	spin_unlock_irq(&rbd_dev->lock);
> > +
> > +	switch (cmd) {
> > +	case BLKROSET:
> > +		if (get_user(ro, (int __user *)(arg))) {
> > +			ret = -EFAULT;
> > +			goto out;
> > +		}
> > +
> > +		/* Snapshot doesn't allow to write*/
> > +		if (rbd_dev->spec->snap_id != CEPH_NOSNAP && ro) {
> > +			ret = -EROFS;
> > +			goto out;
> > +		}
> > +
> > +		if (rbd_dev->mapping.read_only != ro) {
> > +			rbd_dev->mapping.read_only = ro;
> > +			goto out;
> > +		}
> 
> I'm not too familiar with this code, but I did a quick grep for ROSET and 
> it looks like md.c and dasd_ioctl.c both use the set_disk_ro() helper.  
> Should we call that in addition to setting our own read_only flag?

Yes, you are right, I missed it. set_disk_ro() would set other corresponding 
things, such as sysfs, disk partitions, etc.

> 
> Also, do you mind making a simple test for this?  A bash script that does 
> rbd map, sets the disk as ro, and verifies it can't write to it via dd, or 
> something along those lines.  It should go into ceph.git/qa/workunits/rbd/ 
> somewhere.

I have tested with the new version patch: 

root@ceph-client01:~# rbd map img
root@ceph-client01:~# blockdev --getro /dev/rbd1
0
root@ceph-client01:~# cat /sys/block/rbd1/ro 
0
root@ceph-client01:~# blockdev --setro /dev/rbd1
root@ceph-client01:~# blockdev --getro /dev/rbd1
1
root@ceph-client01:~# cat /sys/block/rbd1/ro 
1
root@ceph-client01:~# dd if=/dev/zero of=/dev/rbd1 count=1
dd: opening `/dev/rbd1': Read-only file system`
root@ceph-client01:~# blockdev --setrw /dev/rbd1
root@ceph-client01:~# blockdev --getro /dev/rbd1
0
root@ceph-client01:~# cat /sys/block/rbd1/ro 
0
root@ceph-client01:~# dd if=/dev/zero of=/dev/rbd1 count=1
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.14989 s, 3.4 kB/s

I would send the patch v2 soon.

> 
> Thanks!
> sage
> 
> 
> > +
> > +		break;
> > +	default:
> > +		ret = -EINVAL;
> > +	}
> > +
> > +out:
> > +	return ret;
> > +}
> > +
> > +#ifdef CONFIG_COMPAT
> > +static int rbd_compat_ioctl(struct block_device *bdev, fmode_t mode,
> > +				unsigned int cmd, unsigned long arg)
> > +{
> > +	return rbd_ioctl(bdev, mode, cmd, arg);
> > +}
> > +#endif /* CONFIG_COMPAT */
> > +
> >  static const struct block_device_operations rbd_bd_ops = {
> >  	.owner			= THIS_MODULE,
> >  	.open			= rbd_open,
> >  	.release		= rbd_release,
> > +	.ioctl			= rbd_ioctl,
> > +#ifdef CONFIG_COMPAT
> > +	.compat_ioctl		= rbd_compat_ioctl,
> > +#endif
> >  };
> >  
> >  /*
> > -- 
> > 1.7.9.5
> > 
> > --
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> > 
> > 

-- 
Best regards,
Guangliang