Re: [PATCH 0/2] rbd: thick-provision image support

[Ilya Dryomov]

On Mon, Mar 19, 2018 at 1:00 PM, KAMEI Hitoshi
<hitoshi.kamei.xm@xxxxxxxxxxx> wrote:
> This patch series adds the thick-provision image support to
> /drivers/block/rbd.c relating to https://github.com/ceph/ceph/pull/18317.
> The rbd will not issue the discard operation to thick-provision
> images, if applied.
>
> The rbd should not discard any allocated blocks of thick-provision
> image to ensure writing data to rbd images. So this patch
> prevents from discarding allocated blocks on thick-provision
> image.
>
> This patch series creates sysfs file to manipulate thick-provision
> status. If users write "1" to /sys/bus/rbd/devices/<dev-id>/thick,
> then the image is changed to thick-provision image. And if users
> write "0" to it, then the image is changed to thin-provision
> image. I will add the code changing status for the rbd map command.

Hi Hitoshi,

I think it should be a map time option -- e.g. rbd map -o thick.
I don't see any reason for allowing tweaking this setting on a mapped
image.

I looked through https://github.com/ceph/ceph/pull/18317 and I don't
see an equivalent functionality there.  rbd_discard_on_zeroed_write_same
set to false makes the actual zeroes go on the wire, but I don't see
anything for ignoring discard requests.  Can you point me at that?

Thanks,

                Ilya