Re: [Qemu-devel] [PATCH V17 01/12] quorum: Create quorum.c, add QuorumChildRequest and QuorumAIOCB.

[Max Reitz <mreitz@redhat.com>]

On 12.02.2014 23:06, Benoît Canet wrote:
> From: Benoît Canet <benoit@irqsave.net>
>
> Quorum is a block filter mirroring writes to num_children children.
> For reads quorum reads each children and does a vote.
> If more than vote_threshold versions are identicals the quorum is reached and

-pedantic: "identical", without "s"

> this winning version is returned to the guest. So quorum prevents bit corruption.
> For high availability purpose minority errors are reported via QMP but the guest
> does not see them.
>
> This patch create the driver C source file and introduce the structures that

"creates" and "introduces", with "s"

But since I'm not in -Werror mode, you may leave the reviewed-by. ;-)

Max

> will be used in asynchronous reads and writes.
>
> Signed-off-by: Benoit Canet <benoit@irqsave.net>
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> ---
>   block/Makefile.objs |  1 +
>   block/quorum.c      | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>   2 files changed, 54 insertions(+)
>   create mode 100644 block/quorum.c
>
> diff --git a/block/Makefile.objs b/block/Makefile.objs
> index e254a21..716556f 100644
> --- a/block/Makefile.objs
> +++ b/block/Makefile.objs
> @@ -3,6 +3,7 @@ block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-c
>   block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
>   block-obj-y += qed-check.o
>   block-obj-$(CONFIG_VHDX) += vhdx.o vhdx-endian.o vhdx-log.o
> +block-obj-y += quorum.o
>   block-obj-y += parallels.o blkdebug.o blkverify.o
>   block-obj-y += snapshot.o qapi.o
>   block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
> diff --git a/block/quorum.c b/block/quorum.c
> new file mode 100644
> index 0000000..950f5cc
> --- /dev/null
> +++ b/block/quorum.c
> @@ -0,0 +1,53 @@
> +/*
> + * Quorum Block filter
> + *
> + * Copyright (C) 2012-2014 Nodalink, EURL.
> + *
> + * Author:
> + *   Benoît Canet <benoit.canet@irqsave.net>
> + *
> + * Based on the design and code of blkverify.c (Copyright (C) 2010 IBM, Corp)
> + * and blkmirror.c (Copyright (C) 2011 Red Hat, Inc).
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "block/block_int.h"
> +
> +typedef struct QuorumAIOCB QuorumAIOCB;
> +
> +/* Quorum will create one instance of the following structure per operation it
> + * performs on its children.
> + * So for each read/write operation coming from the upper layer there will be
> + * $children_count QuorumChildRequest.
> + */
> +typedef struct QuorumChildRequest {
> +    BlockDriverAIOCB *aiocb;
> +    QEMUIOVector qiov;
> +    uint8_t *buf;
> +    int ret;
> +    QuorumAIOCB *parent;
> +} QuorumChildRequest;
> +
> +/* Quorum will use the following structure to track progress of each read/write
> + * operation received by the upper layer.
> + * This structure hold pointers to the QuorumChildRequest structures instances
> + * used to do operations on each children and track overall progress.
> + */
> +struct QuorumAIOCB {
> +    BlockDriverAIOCB common;
> +
> +    /* Request metadata */
> +    uint64_t sector_num;
> +    int nb_sectors;
> +
> +    QEMUIOVector *qiov;         /* calling IOV */
> +
> +    QuorumChildRequest *qcrs;   /* individual child requests */
> +    int count;                  /* number of completed AIOCB */
> +    int success_count;          /* number of successfully completed AIOCB */
> +
> +    bool is_read;
> +    int vote_ret;
> +};