[stgt] [PATCHes] Updated patches for thin-provisioning support

[ronnie sahlberg]

Hi Tomo,

I think for safety it is better to require this as an explicit option,
but I dont have any strong opinion either for or against.

What changes do you you want me to implement for this patch ?
Do you want me to re-spin the patch and remove the option ?


regards
ronnie sahlberg


On Mon, Apr 2, 2012 at 10:26 AM, FUJITA Tomonori
<fujita.tomonori at lab.ntt.co.jp> wrote:
> On Mon, 02 Apr 2012 09:06:11 +0900 (JST)
> FUJITA Tomonori <fujita.tomonori at lab.ntt.co.jp> wrote:
>
>> On Sun, 1 Apr 2012 08:26:27 +1000
>> ronnie sahlberg <ronniesahlberg at gmail.com> wrote:
>>
>>> From 2830abc3935294eba621b781f72aecda604c65a7 Mon Sep 17 00:00:00 2001
>>> From: Ronnie Sahlberg <ronniesahlberg at gmail.com>
>>> Date: Sun, 1 Apr 2012 08:04:06 +1000
>>> Subject: [PATCH 2/2] SBC UNMAP: Add support for thin-provisioning and the UNMAP command.
>>>
>>> The UNMAP command is implemented using FALLOC_FL_PUNCH_HOLE and will
>>> release UNMAPPED blocks back to the underlying filesystem.
>>>
>>> FALLOC_FL_PUNCH_HOLE is fairly new addition to Linux but works on
>>> ext4 and XFS filesystems currently.
>>>
>>> Signed-off-by: Ronnie Sahlberg <ronniesahlberg at gmail.com>
>>> ---
>>>  doc/tgtadm.8.xml |   25 ++++++++++++++
>>>  usr/bs_rdwr.c    |   97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  usr/sbc.c        |   76 +++++++++++++++++++++++++++++++++++++++++-
>>>  usr/scsi.h       |    1 +
>>>  usr/spc.c        |   43 +++++++++++++++++++++--
>>>  usr/target.c     |    2 +
>>>  usr/tgtd.h       |    2 +
>>>  7 files changed, 241 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/doc/tgtadm.8.xml b/doc/tgtadm.8.xml
>>> index 668e184..a40f659 100644
>>> --- a/doc/tgtadm.8.xml
>>> +++ b/doc/tgtadm.8.xml
>>> @@ -352,6 +352,31 @@ tgtadm --lld iscsi --mode logicalunit --op update --tid 1 --lun 1 \
>>>           --params readonly=1
>>>        </screen>
>>>
>>> +      <varlistentry><term><option>thin_provisioning=<0|1></option></term>
>>> +        <listitem>
>>> +          <para>
>>> +        This controls the provisioning for the LUN. A thin-provisioned
>>> +        LUN is represented as a sparse file.
>>> +        TGTD supports provisioning type 2 for sparse files.
>>> +        When initiators use the SCSI UNMAP command TGTD will release
>>> +        the affected areas back to the filesystem using
>>> +        FALLOC_FL_PUNCH_HOLE.
>>> +          </para>
>>> +          <para>
>>> +        This parameter only applies to DISK devices.
>>> +          </para>
>>> +          <para>
>>> +        Thin-provisioning only works for LUNs stored on filesystems
>>> +        that support FALLOC_FL_PUNCH_HOLE.
>>> +          </para>
>>> +        </listitem>
>>> +      </varlistentry>
>>> +
>>> +      <screen format="linespecific">
>>> +tgtadm --lld iscsi --mode logicalunit --op update --tid 1 --lun 1 \
>>> +         --params thin_provisioning=1
>>> +      </screen>
>>
>> Users need to enable this explicitly?
>>
>> I mean that when a lu is added, tgtd can check if the backing storage
>> supports FALLOC_FL_PUNCH_HOLE then enables it automatically?
>
> Note that I'm not against providing the explict option to users but
> normally users has the option for this (e.g. btrfs mount option) on
> the initiator side. So even if tgtd automatically enables this, users
> can avoid using this feature. So I wonder that it's worth providing
> the explict option.
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