Re: [Scst-devel] Update in size is not seen by scst.

[Alessandro M. <ale...@gm...>]

2013/6/25 Bart Van Assche <bva...@ac...>

> On 06/25/13 14:18, Alessandro MACUZ wrote:
>
>> Hi all,
>>
>> my setup is made of ZFS block devices and I use vdisk_blockio handler to
>> present them to a VMhost.
>>
>> When I change the size of zfs block device (zfs set volsize=xxG
>> zpool/etc/etc/blah) I don't see this reflected by SCST.
>> This is what I do
>>
>> root@server:/sys/kernel/scst_**tgt/handlers/vdisk_blockio/**
>> sandbox_disk1#
>> cat size_mb
>> 5120
>> root@server:/sys/kernel/scst_**tgt/handlers/vdisk_blockio/**
>> sandbox_disk1#
>> zfs set volsize=15G zserver/machines/sandbox/disk1
>> root@server:/sys/kernel/scst_**tgt/handlers/vdisk_blockio/**
>> sandbox_disk1#
>> zfs get volsize zserver/machines/sandbox/disk1
>> NAME                              PROPERTY  VALUE    SOURCE
>> zserver/machines/sandbox/disk1  volsize   15G      local
>> root@server:/sys/kernel/scst_**tgt/handlers/vdisk_blockio/**
>> sandbox_disk1#
>> cat size_mb
>> 5120
>> root@server:/sys/kernel/scst_**tgt/handlers/vdisk_blockio/**
>> sandbox_disk1#
>>
>> I'm told that such changes should be automatically detected by SCST. The
>> problem arose because in my set up when I change the size this is not
>> seen on the VM hosts and I have to delete the handler and recreate it.
>>
>
> Please have a look at the documentation of the "resync_size" sysfs
> attribute in scst/README.
>
> Bart.
>
>
Thanks Bart,

in the README I read

"The following parameters possible for vdisk_blockio: filename,
blocksize, nv_cache, read_only, removable, thin_provisioned. See
vdisk_fileio above for description of those parameters."

Indeed resync_size is not available when creating vdisk_blockio and the
parameter is not accepted

root@server:/sys/kernel/scst_tgt/handlers/vdisk_blockio# echo "add_device
sandbox_disk1
filename=/dev/zvol/zserver/machines/sandbox/disk1;resync_size=1;nv_cache=1;thin_provisioned=1"
> mgmt
bash: echo: write error: Invalid argument

root@server:/opt/trunk2/2.2.x/scst# dmesg -T
...
[Tue Jun 25 15:05:02 2013] dev_vdisk: ***ERROR***: Unknown parameter
resync_size (device sandbox_disk1)

Is there any other way to achieve the same result without
deleting/recreating the handler?

Was such option left aside for block device because they are not supposed
to change in size? Actually they can change.
Will it be added in the future or there are other constraints that prevent
to implement it for block devices?

Thanks,

Alex