[Qemu-devel] [PATCH 00/10] Quorum disk image corruption resiliency

["Benoît Canet" <benoit.canet@gmail.com>]

This patchset create a block driver implementing a quorum using three qemu disk
images. Writes are mirrored on the three files.
For the reading part the three files are read at the same time and a vote is
done to determine which is the majority qiov version. It then return this
majority version to the upper layers.
When three differents versions of the data are returned by the lower layer the
quorum is broken and the read return -EIO.

The goal of this patchset is to be turned in a QEMU block filter living just
above raw-*.c and below qcow2/qed when the required infrastructure will be done.

Main use of this feature will be people using NFS appliances which can be
subjected to bitflip errors.

usage: -drive file=quorum:image1.raw:image2.raw:image3.raw,if=virtio,cache=none

in v2:

eblake: fix typos
        squash two first commits

afärber: Modify the Makefile on first commit

bcanet: move function prototype of quorum.c one patch down

open question:
    Would the ability to do quorum on 2n+1 images like Blue Swirl suggested be
    popular ?

Benoît Canet (10):
  quorum: Create quorum.c, add QuorumSingleAIOCB and QuorumAIOCB.
  quorum: Create BDRVQuorumState and BlkDriver and do init.
  quorum: Add quorum_open().
  quorum: Add quorum_close().
  quorum: Add quorum_getlength().
  quorum: Add quorum_aio_writev and its dependencies.
  blkverify: Make blkverify_iovec_clone() and blkverify_iovec_compare()
    public
  quorum: Add quorum_co_flush().
  quorum: Add quorum_aio_readv.
  quorum: Add quorum mechanism.

 block/Makefile.objs |    1 +
 block/blkverify.c   |    8 +-
 block/quorum.c      |  390 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 397 insertions(+), 2 deletions(-)
 create mode 100644 block/quorum.c

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1.7.9.5