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

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Tuesday 04 Feb 2014 à 13:57:07 (+0100), Kevin Wolf a écrit :
> 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.

It's a reference to blkmirror.c by Marcello Tosati. A patch that was never merged.
https://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCkQFjAA&url=https%3A%2F%2Flists.gnu.org%2Farchive%2Fhtml%2Fqemu-devel%2F2011-05%2Fmsg02521.html&ei=FzzyUuOBEeSg0QX9jYCgCg&usg=AFQjCNG6W5qbmITacObTAD4ShOZlxky2bA&bvm=bv.60799247,d.d2k

> 
> > + *
> > + * 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