[23/25] block: add close notifiers

The first user of close notifiers will be the embedded NBD server.
It is possible to use them to do some of the ad hoc processing
(e.g. for block jobs and I/O limits) that is currently done by
bdrv_close.

Acked-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 Makefile.objs |  4 ++--
 block.c       | 19 ++++++++++++++-----
 block.h       |  1 +
 block_int.h   |  2 ++
 4 file modificati, 19 inserzioni(+), 7 rimozioni(-)

Paolo Bonzini <pbonzini@redhat.com> writes:

> The first user of close notifiers will be the embedded NBD server.
> It is possible to use them to do some of the ad hoc processing
> (e.g. for block jobs and I/O limits) that is currently done by
> bdrv_close.
>
> Acked-by: Kevin Wolf <kwolf@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  Makefile.objs |  4 ++--
>  block.c       | 19 ++++++++++++++-----
>  block.h       |  1 +
>  block_int.h   |  2 ++
>  4 file modificati, 19 inserzioni(+), 7 rimozioni(-)
>
> diff --git a/Makefile.objs b/Makefile.objs
> index 3f16d67..ca67885 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -43,7 +43,7 @@ coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
>  
>  block-obj-y = cutils.o iov.o cache-utils.o qemu-option.o module.o async.o
>  block-obj-y += nbd.o block.o blockjob.o aio.o aes.o qemu-config.o
> -block-obj-y += qemu-progress.o qemu-sockets.o uri.o
> +block-obj-y += qemu-progress.o qemu-sockets.o uri.o notify.o
>  block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
>  block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
>  block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
> @@ -94,7 +94,7 @@ common-obj-y += bt-host.o bt-vhci.o
>  common-obj-y += dma-helpers.o
>  common-obj-y += iov.o acl.o
>  common-obj-$(CONFIG_POSIX) += compatfd.o
> -common-obj-y += notify.o event_notifier.o
> +common-obj-y += event_notifier.o
>  common-obj-y += qemu-timer.o qemu-timer-common.o
>  common-obj-y += qtest.o
>  common-obj-y += vl.o
> diff --git a/block.c b/block.c
> index e95f613..56426a9 100644
> --- a/block.c
> +++ b/block.c
> @@ -30,6 +30,7 @@
>  #include "module.h"
>  #include "qjson.h"
>  #include "sysemu.h"
> +#include "notify.h"
>  #include "qemu-coroutine.h"
>  #include "qmp-commands.h"
>  #include "qemu-timer.h"
> @@ -312,9 +313,16 @@ BlockDriverState *bdrv_new(const char *device_name)
>          QTAILQ_INSERT_TAIL(&bdrv_states, bs, list);
>      }
>      bdrv_iostatus_disable(bs);
> +    notifier_list_init(&bs->close_notifiers);
> +
>      return bs;
>  }
>  
> +void bdrv_add_close_notifier(BlockDriverState *bs, Notifier *notify)
> +{
> +    notifier_list_add(&bs->close_notifiers, notify);
> +}
> +
>  BlockDriver *bdrv_find_format(const char *format_name)
>  {
>      BlockDriver *drv1;
> @@ -1098,12 +1106,13 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
>  void bdrv_close(BlockDriverState *bs)
>  {
>      bdrv_flush(bs);
> -    if (bs->drv) {
> -        if (bs->job) {
> -            block_job_cancel_sync(bs->job);
> -        }
> -        bdrv_drain_all();
> +    if (bs->job) {
> +        block_job_cancel_sync(bs->job);
> +    }
> +    bdrv_drain_all();

Dropping the bs->drv condition in a separate commit gives you a nice
place to explain why it's fine: the commit message.  I figure it is, but
it's not 100% obvious.

> +    notifier_list_notify(&bs->close_notifiers, bs);
>  
> +    if (bs->drv) {
>          if (bs == bs_snapshots) {
>              bs_snapshots = NULL;
>          }
[...]

Paolo Bonzini <pbonzini@redhat.com> writes:

> The first user of close notifiers will be the embedded NBD server.
> It is possible to use them to do some of the ad hoc processing
> (e.g. for block jobs and I/O limits) that is currently done by
> bdrv_close.

If the second sentence is an idea for future work, you could make that
clearer by wriging "It would be possible to use them".

[...]

> > @@ -1098,12 +1106,13 @@ void bdrv_reopen_abort(BDRVReopenState *reopen_state)
> >  void bdrv_close(BlockDriverState *bs)
> >  {
> >      bdrv_flush(bs);
> > -    if (bs->drv) {
> > -        if (bs->job) {
> > -            block_job_cancel_sync(bs->job);
> > -        }
> > -        bdrv_drain_all();
> > +    if (bs->job) {
> > +        block_job_cancel_sync(bs->job);
> > +    }
> > +    bdrv_drain_all();
> 
> Dropping the bs->drv condition in a separate commit gives you a nice
> place to explain why it's fine: the commit message.  I figure it is,
> but it's not 100% obvious.

Will do, thanks.

Paolo