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

[FUJITA Tomonori]

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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