Re: [PATCH] ceph: rbd option listing and tcp_nodelay support

[Ilya Dryomov <ilya.dryomov@inktank.com>]

On Wed, Jan 21, 2015 at 10:29 PM, Somnath Roy <Somnath.Roy@sandisk.com> wrote:
> Ilya,
> Regarding supported attribute list,  I think it could be a step towards better usability experience during rbd map command. Presently, if user gives wrong option or unsupported option it just errors out saying 'sysfs write failed' or so. User has no idea what went wrong.

# rbd map -o foobar test
rbd: unknown map option 'foobar'
rbd: couldn't parse map options

# rbd map -o fsid=foobar test
rbd: invalid fsid value 'foobar'
rbd: couldn't parse map options

Since about a year ago, rbd cli would try to parse supplied options.
Of course, the list of options it knows about is static, but your
attribute wouldn't solve that problem (or rather it will, but only for
simple boolean yes/no options, like crc or tcp_nodelay) because we also
try to sanity check the value, as the above fsid example shows.

> We can use this supported list from kernel module from rbd cli to show proper error message to the user.
> Another feature that we have implemented is rbd cli to consult the /etc/ceph/ceph.conf and take the rbd kernel supported options from there automatically if user has not provided any option during rbd map. User provided option during rbd map will always get priority though.

Did you mean "and take rbd kernel map options", i.e. take default
map options from ceph.conf?  I think that's a good idea.

Thanks,

                Ilya