Re: [Qemu-devel] [Qemu-stable] Data corruption in Qemu 2.7.1

[Peter Lieven]

Am 17.01.2017 um 07:40 schrieb Fam Zheng:
> On Fri, 01/13 11:44, Peter Lieven wrote:
> > Hi,
> >
> > i currently facing a problem in our testing environment where I see file
> > system corruption with 2.7.1 on iSCSI and Local Storage (LVM).
> > Trying to bisect, but has anyone observed this before?
> The information here is too scarce to tell but a file corruption is more often a
> result of two writers modifying the disk concurrently. Have you ruled that out?
> Is the corruption reproducible?

My issue was primary with iSCSI and I cut bisect it. I already send a patch to 
the list:

commit 0bd57e907311be6e4f97394cfd9afebe271457e2
Author: Peter Lieven <address@hidden>
Date:   Mon Jan 16 16:10:26 2017 +0100

    block/iscsi: avoid data corruption with cache=writeback

    nb_cls_shrunk in iscsi_allocmap_update can become -1 if the
    request starts and ends within the same cluster. This results
    in passing -1 to bitmap_set and bitmap_clear and they don't
    handle negative values properly. In the end this leads to data
    corruption.

    Fixes: e1123a3b40a1a9a625a29c8ed4debb7e206ea690
    Cc: address@hidden
    Signed-off-by: Peter Lieven <address@hidden>

However, one user also reported corruption with LVM. I will check if he uses 
virtio-scsi.

Thanks,
Peter