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From: Jason Dillaman <jdillama@redhat.com>
Date: Wed, 21 Mar 2018 06:31:20 +0800
Message-ID: <CA+aFP1AunD_KvE5JkFAzzEtu+D5dKS_nhEbyvS9COQM2PXuDCw@mail.gmail.com>
Subject: Re: [PATCH 0/2] rbd: thick-provision image support
To: Ilya Dryomov <idryomov@gmail.com>
Cc: KAMEI Hitoshi <hitoshi.kamei.xm@hitachi.com>,
        Sage Weil <sage@redhat.com>, Alex Elder <elder@kernel.org>,
        Ceph Development <ceph-devel@vger.kernel.org>,
        linux-kernel@vger.kernel.org
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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@gmail.com> wrote:
> On Mon, Mar 19, 2018 at 1:00 PM, KAMEI Hitoshi
> <hitoshi.kamei.xm@hitachi.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