Re: [Qemu-devel] [PATCH alt 1/7] block: Add status callback to bdrv_amend_options()

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

The Thursday 31 Jul 2014 à 09:51:05 (+0200), Benoît Canet wrote :
> The Saturday 26 Jul 2014 à 21:22:05 (+0200), Max Reitz wrote :
> 
> > Depending on the changed options and the image format,
> > bdrv_amend_options() may take a significant amount of time. In these
> > cases, a way to be informed about the operation's status is desirable.
> > 
> > Since the operation is rather complex and may fundamentally change the
> > image, implementing it as AIO or a couroutine does not seem feasible. On
> > the other hand, implementing it as a block job would be significantly
> > more difficult than a simple callback and would not add benefits other
> > than progress report to the amending operation, because it should not
> > actually be run as a block job at all.
> > 
> > A callback may not be very pretty, but it's very easy to implement and
> > perfectly fits its purpose here.
> > 
> > Signed-off-by: Max Reitz <mreitz@redhat.com>
> > ---
> >  block.c                   | 5 +++--
> >  block/qcow2.c             | 5 ++++-
> >  include/block/block.h     | 5 ++++-
> >  include/block/block_int.h | 3 ++-
> >  qemu-img.c                | 2 +-
> >  5 files changed, 14 insertions(+), 6 deletions(-)
> > 
> > diff --git a/block.c b/block.c
> > index 3e252a2..4c8d4d8 100644
> > --- a/block.c
> > +++ b/block.c
> > @@ -5708,12 +5708,13 @@ void bdrv_add_before_write_notifier(BlockDriverState *bs,
> >      notifier_with_return_list_add(&bs->before_write_notifiers, notifier);
> >  }
> >  
> > -int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts)
> > +int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
> > +                       BlockDriverAmendStatusCB *status_cb)
> >  {
> >      if (!bs->drv->bdrv_amend_options) {
> >          return -ENOTSUP;
> >      }
> > -    return bs->drv->bdrv_amend_options(bs, opts);
> > +    return bs->drv->bdrv_amend_options(bs, opts, status_cb);
> >  }
> >  
> >  /* This function will be called by the bdrv_recurse_is_first_non_filter method
> > diff --git a/block/qcow2.c b/block/qcow2.c
> > index b0faa69..757f890 100644
> > --- a/block/qcow2.c
> > +++ b/block/qcow2.c
> > @@ -2210,7 +2210,8 @@ static int qcow2_downgrade(BlockDriverState *bs, int target_version)
> >      return 0;
> >  }
> >  
> > -static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
> > +static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
> > +                               BlockDriverAmendStatusCB *status_cb)
> >  {
> >      BDRVQcowState *s = bs->opaque;
> >      int old_version = s->qcow_version, new_version = old_version;
> > @@ -2223,6 +2224,8 @@ static int qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts)
> >      int ret;
> >      QemuOptDesc *desc = opts->list->desc;
> >  
> > +    (void)status_cb;
> 
> This look like a temporary hack to please the compiler.
> Am I right ? Should be comment this ?

For the further patch I now understand this I am just suprised that you need to silence a unused function parameter.

Reviewed-by: Benoit Canet <benoit@irqsave.net>

> 
> > +
> >      while (desc && desc->name) {
> >          if (!qemu_opt_find(opts, desc->name)) {
> >              /* only change explicitly defined options */
> > diff --git a/include/block/block.h b/include/block/block.h
> > index 32d3676..f2b1799 100644
> > --- a/include/block/block.h
> > +++ b/include/block/block.h
> > @@ -309,7 +309,10 @@ typedef enum {
> >  
> >  int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix);
> >  
> > -int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts);
> > +typedef void BlockDriverAmendStatusCB(BlockDriverState *bs, int64_t offset,
> > +                                      int64_t total_work_size);
> > +int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts,
> > +                       BlockDriverAmendStatusCB *status_cb);
> >  
> >  /* external snapshots */
> >  bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
> > diff --git a/include/block/block_int.h b/include/block/block_int.h
> > index f6c3bef..5c5798d 100644
> > --- a/include/block/block_int.h
> > +++ b/include/block/block_int.h
> > @@ -228,7 +228,8 @@ struct BlockDriver {
> >      int (*bdrv_check)(BlockDriverState* bs, BdrvCheckResult *result,
> >          BdrvCheckMode fix);
> >  
> > -    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts);
> > +    int (*bdrv_amend_options)(BlockDriverState *bs, QemuOpts *opts,
> > +                              BlockDriverAmendStatusCB *status_cb);
> >  
> >      void (*bdrv_debug_event)(BlockDriverState *bs, BlkDebugEvent event);
> >  
> > diff --git a/qemu-img.c b/qemu-img.c
> > index ef74ae4..90d6b79 100644
> > --- a/qemu-img.c
> > +++ b/qemu-img.c
> > @@ -2827,7 +2827,7 @@ static int img_amend(int argc, char **argv)
> >          goto out;
> >      }
> >  
> > -    ret = bdrv_amend_options(bs, opts);
> > +    ret = bdrv_amend_options(bs, opts, NULL);
> >      if (ret < 0) {
> >          error_report("Error while amending options: %s", strerror(-ret));
> >          goto out;
> > -- 
> > 2.0.3
> > 
> > 
>