Re: [Qemu-devel] [RFC V8 00/13] Quorum block filter.

[Benoît Canet]

Hi,

My customer no longer provide me financial support to write/maintain Quorum
because snapshots will be missing for a long time.

As you (Eric, Stefanha and Kevin) helped me to improve Quorum by spending time
doing code reviews I need your answers to the following question.

Do you feel that Quorum would be a valuable asset if it get merged in QEMU.

If so I will iterate on your reviews to get it in a mergeable state.

Best regards

Benoît

> Le Monday 28 Jan 2013 à 18:07:12 (+0100), Benoît Canet a écrit :
> This patchset is rebased on top of "cutils: unsigned int parsing functions"
> by "Eduardo Habkost".
> 
> It must be applied on top of "Pave the way for protocol snapshot creation"
> 
> This patchset create a block driver implementing a quorum using total qemu 
> disk
> images. Writes are mirrored on the $total files.
> For the reading part the $total files are read at the same time and a vote is
> done to determine if a qiov version is present $threshold or more times. It 
> then
> return this majority version to the upper layers.
> When i < $threshold 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.
> 
> This patchset can be used to replace blkverify and the out of tree blkmirror.
> 
> usage: -drive
> file=quorum:threshold/total:image_1.raw:...:image_total.raw,if=virtio,cache=none
> 
> v8: merge qiov in QuorumSingleAIOB [Stefan]
> 
> v7.5:
>     Allow creation of snapshots
>     Extract utility functions of quorum_open and quorum_close
>     reorder patches so quorum_open and quorum_close are added last
> 
> v7:
>     parse total and threshold with parse_uint [Eric]
>     return proper qerrors in quorum_open [Eric]
>     Use sha256 for comparing blocks [Eric]
>     Update the rest of the voting function to the new way of doing [Benoît]
> 
> V6:
>     fix commit message of "quorum: Add quorum_open() and quorum_close()." 
> [Eric]
>     return error after a vote in quorum_co_flush [Eric]
>     Fix bitrot caused by headers and structures renaming [Benoît]
>     initialize finished to NULL to prevent crash [Benoît]
>     convert internal quorum code to uint64_t instead of int64_t [Benoît]
> 
> V5:
> 
> Eric Blake: revert back separator to ":"
>             rewrite quorum_getlength
> 
> Benoît Canet: use memcmp to compare iovec excepted for the blkverify case
>               use strstart to parse argument in open
> 
> Benoît Canet (13):
>   quorum: Create quorum.c, add QuorumSingleAIOCB and QuorumAIOCB.
>   quorum: Create BDRVQuorumState and BlkDriver and do init.
>   quorum: Add quorum_aio_writev and its dependencies.
>   blkverify: Extract qemu_iovec_clone() and qemu_iovec_compare() from
>     blkverify.
>   quorum: Add quorum_aio_readv.
>   quorum: Add quorum mechanism.
>   quorum: Add quorum_getlength().
>   quorum: Add quorum_invalidate_cache().
>   quorum: Add quorum_co_is_allocated.
>   quorum: Add quorum_co_flush().
>   quorum: Add quorum_snapshot_img_create.
>   quorum: Add quorum_snapshot_reopen.
>   quorum: Add quorum_open() and quorum_close().
> 
>  block/Makefile.objs   |    1 +
>  block/blkverify.c     |  108 +-----
>  block/quorum.c        |  906 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  configure             |   22 ++
>  include/qemu-common.h |    2 +
>  util/iov.c            |  103 ++++++
>  6 files changed, 1036 insertions(+), 106 deletions(-)
>  create mode 100644 block/quorum.c
> 
> -- 
> 1.7.10.4
>