[sheepdog] Call to sd_truncate()

[Hadrien KOHL]

I am using the latest version of qemu (tag v1.7.0). I compiled myself today
to be sure. What version of sheepdog were you using? I think I compiled the
tag v0.7.5.

Did you use the same parameters to start the virtual machine? I'm
suspecting virtio to be a problem.
I will make some more test tomorrow.

Thank you for your help.

Hadrien Kohl


2013/12/12 Liu Yuan <namei.unix at gmail.com>

> On Thu, Dec 12, 2013 at 01:47:25PM +0100, Hadrien KOHL wrote:
> > 2013/12/12 Liu Yuan <namei.unix at gmail.com>
> >
> > > On Thu, Dec 12, 2013 at 12:25:52PM +0100, Hadrien KOHL wrote:
> > > > I just sent the question to the qemu developer mailing list. But as I
> > > did,
> > > > I remembered this sd_truncate is also called
> > > > from  sd_co_writev(BlockDriverState *bs, int64_t sector_num, int
> > > > nb_sectors, QEMUIOVector *qiov):
> > > >
> > > > static coroutine_fn int sd_co_writev(BlockDriverState *bs, int64_t
> > > > sector_num,
> > > >                         int nb_sectors, QEMUIOVector *qiov)
> > > > {
> > > >     SheepdogAIOCB *acb;
> > > >      int ret;
> > > >
> > > >     if (bs->growable && sector_num + nb_sectors > bs->total_sectors)
> {
> > > >         ret = sd_truncate(bs, (sector_num + nb_sectors) *
> > > BDRV_SECTOR_SIZE);
> > > >         if (ret < 0) {
> > > >             return ret;
> > > >         }
> > >
> > > From the code, so if growable is true, seems that sheepdog support
> > > automatic
> > > grow of volume. So my last email about 'can't resize live VM' is wrong.
> > >
> > > By a simply glance of the code, seems that bs->growable is set by
> qcow2.c,
> > > which
> > > indicate that this might be a feature from qcow2 format.
> > >
> > > >         bs->total_sectors = sector_num + nb_sectors;
> > > >     }
> > > >
> > > >     acb = sd_aio_setup(bs, qiov, sector_num, nb_sectors);
> > > >     acb->aio_done_func = sd_write_done;
> > > >     acb->aiocb_type = AIOCB_WRITE_UDATA;
> > > >
> > > >     ret = sd_co_rw_vector(acb);
> > > > ...
> > > > }
> > > >
> > > > This function is mapped to bdrv_co_writev in the qemu driver.
> > > > Looking at the test in this function, the only way a shrink could
> happen
> > > -
> > > > I guess - is if the units in sector_num and nb_sectors are
> inconsistent
> > > > (esp since there's a conversion to "BDRV_SECTOR_SIZE") in relation to
> > > > bs->total_sectors.
> > > > I am using qcow2 file format and created the image with qemu-img -t
> qcow2
> > > > create sheepdog:name. Could it be related?
> > >
> > > I think this might be a bug about running qcow2 in sheepdog, but I
> can't
> > > figure
> > > out what is the problem by statically reviewing the code. Is there a
> > > reliable
> > > way to reproduce it?
> > >
> >
> > Here is a way to reproduce:
> >
> > First I create a test image. Then I boot (here using gentoo live cd).
> >
> > # qemu-img create -f qcow2 sheepdog:test 10G
> > Formatting 'sheepdog:test', fmt=qcow2 size=10737418240 encryption=off
> > cluster_size=65536 lazy_refcounts=off
> > # qemu-system-x86_64 -drive
> > file=sheepdog:127.0.0.1:7000
> :test,if=none,id=virtio-disk0,format=qcow2,cache=writeback
> > -cdrom /vm/iso/install-amd64-minimal-20131010.iso -boot cd -m 256 -name
> > test -vnc 172.16.0.11:0
> >
> > Then once logged in the machine via vnc:
> > # mkfs.ext4 /dev/vda
> > # mkdir /mnt/vda
> >
> > Then I start receiving:
> >
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> > qemu-system-x86_64: shrinking is not supported
> >
> > And IO buffer errors on the guest:
> >
> > Buffer I/O error on device vda, logical block XXXXXXX
> >
> > Hadrien
> >
>
> Just had a test with ubuntu 12.04 live CD following your steps and no
> problem at
> all. I am running latest QEMU, so can you try latest QEMU such as v1.7?
>
> yliu at ubuntu-precise:~/sheepdog$ qemu-img info sheepdog:test
> image: sheepdog:test
> file format: qcow2
> virtual size: 10G (10737418240 bytes)
> disk size: 136M
> cluster_size: 65536
> Format specific information:
>     compat: 1.1
>     lazy refcounts: false
>
> Thanks
> Yuan
>
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