Re: [Qemu-devel] [PATCH V15 01/13] quorum: Create quorum.c, add QuorumSingleAIOCB and QuorumAIOCB.

[Kevin Wolf <kwolf@redhat.com>]

Am 03.02.2014 um 22:51 hat Benoît Canet geschrieben:
> From: Benoît Canet <benoit@irqsave.net>
> 
> Signed-off-by: Benoit Canet <benoit@irqsave.net>
> Reviewed-by: Max Reitz <mreitz@redhat.com>
> ---
>  block/Makefile.objs |  1 +
>  block/quorum.c      | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 55 insertions(+)
>  create mode 100644 block/quorum.c
> 
> diff --git a/block/Makefile.objs b/block/Makefile.objs
> index 4e8c91e..a2650b9 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..17695d6
> --- /dev/null
> +++ b/block/quorum.c
> @@ -0,0 +1,54 @@
> +/*
> + * 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).

I think you were planning to respin anyway, so I'll practice my
nitpicking: The file is called mirror.c, not blkmirror.c.

> + *
> + * 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 QuorumSingleAIOCB.
> + */
> +typedef struct QuorumSingleAIOCB {
> +    BlockDriverAIOCB *aiocb;

So this isn't a real AIOCB, but it merely points to one. Perhaps
something like QuorumChildRequest would be a more precise name?

> +    QEMUIOVector qiov;
> +    uint8_t *buf;

The combination of a linear buffer and qiov is unusual. It looks like
there may be a reason for it (otherwise qemu_iovec_clone() wouldn't
exist), but I don't understand it yet at this point. Could hint at a
lack of documentation.

I might back come to this later in the patch series.

> +    int ret;
> +    QuorumAIOCB *parent;
> +} QuorumSingleAIOCB;
> +
> +/* 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 QuorumSingleAIOCB 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 */
> +
> +    QuorumSingleAIOCB *aios;    /* individual AIOs */
> +    int count;                  /* number of completed AIOCB */
> +    int success_count;          /* number of successfully completed AIOCB */
> +    bool *finished;             /* completion signal for cancel */
> +
> +    bool is_read;
> +    int vote_ret;
> +};

Kevin