Re: [Qemu-devel] [RFC V7 00/11] Quorum block filter

[Zhi Yong Wu]

On Sat, Jan 19, 2013 at 1:30 AM, Benoît Canet <address@hidden> wrote:
> This patchset is rebased on top of "cutils: unsigned int parsing functions"
> by "Eduardo Habkost".
>
> 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
I don't know if the following case can be handled correctly.
For example, quorum:2/3:image1.raw:image2.raw:image3.raw
Let us assume that some data in image2.raw and image3.raw get
corrupted, and the two images are now completely identical; while
image1.raw doesn't get corrupted. In this case, how will your vote
method know if which image gets corrupted and which image doesn't?

>
> in this version:
>     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 (11):
>   quorum: Create quorum.c, add QuorumSingleAIOCB and QuorumAIOCB.
>   quorum: Create BDRVQuorumState and BlkDriver and do init.
>   quorum: Add quorum_open() and quorum_close().
>   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().
>
>  block/Makefile.objs   |    1 +
>  block/blkverify.c     |  108 +------
>  block/quorum.c        |  789 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  configure             |   22 ++
>  include/qemu-common.h |    2 +
>  util/iov.c            |  103 +++++++
>  6 files changed, 919 insertions(+), 106 deletions(-)
>  create mode 100644 block/quorum.c
>
> --
> 1.7.10.4
>
>



-- 
Regards,

Zhi Yong Wu