On Fri, Jan 24, 2020 at 8:03 AM Hannes Reinecke <hare@xxxxxxx> wrote:
>
> On 1/23/20 7:45 PM, Ilya Dryomov wrote:
> > On Thu, Jan 23, 2020 at 1:44 PM Hannes Reinecke <hare@xxxxxxx> wrote:
> >>
> >> The rbd driver already provides additional information in sysfs
> >> under /sys/bus/rbd, so we should set the 'device' link in the block
> >> device to reference this information.
> >>
> >> Cc: David Disseldorp <ddiss@xxxxxxxx>
> >> Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
> >> ---
> >> drivers/block/rbd.c | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
> >> index 9f1f8689e316..3240b7744aeb 100644
> >> --- a/drivers/block/rbd.c
> >> +++ b/drivers/block/rbd.c
> >> @@ -6938,7 +6938,7 @@ static ssize_t do_rbd_add(struct bus_type *bus,
> >> if (rc)
> >> goto err_out_image_lock;
> >>
> >> - add_disk(rbd_dev->disk);
> >> + device_add_disk(&rbd_dev->dev, rbd_dev->disk, NULL);
> >> /* see rbd_init_disk() */
> >> blk_put_queue(rbd_dev->disk->queue);
> >
> > Hi Hannes,
> >
> > I looked at this a while ago and didn't go through with the patch
> > because I wasn't sure whether this symlink can point to something
> > arbitrary. IIRC it usually points a couple of levels up, to some
> > parent. In the rbd case, this would be a completely different tree:
> > /sys/devices/virtual -> /sys/bus/rbd.
> >
> Yes, this is expected.
> The 'device' link will _always_ point into a different tree; the
> accessor via /sys/block or /sys/bus are assumed to be virtual entries,
> with the 'device' link pointing to the underlying device.
> In our case the underlying device is also a virtual entity, but that's okay.
>
> > Do you know if there is precedent for this in some other driver?
> > Are you sure it's not going to break any assumptions?
> >
> Things like iscsi do the very same thing.
> And no, it doesn't break assumptions; quite the contrary.
I see, thanks for the explanation.
Queued up for 5.6.
Thanks,
Ilya
