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

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Date:   Wed, 21 Mar 2018 06:31:20 +0800
From:   Jason Dillaman <jdillama@...hat.com>
To:     Ilya Dryomov <idryomov@...il.com>
Cc:     KAMEI Hitoshi <hitoshi.kamei.xm@...achi.com>,
        Sage Weil <sage@...hat.com>, Alex Elder <elder@...nel.org>,
        Ceph Development <ceph-devel@...r.kernel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] rbd: thick-provision image support

There isn't currently an option to disable discards in librbd.
However, given that's the intent of this change, why not name the
option along the lines of "discard_disbled"?

On Tue, Mar 20, 2018 at 10:06 PM, Ilya Dryomov <idryomov@...il.com> wrote:
> On Mon, Mar 19, 2018 at 1:00 PM, KAMEI Hitoshi
> <hitoshi.kamei.xm@...achi.com> 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
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-- 
Jason