Re: [PATCH v2 4/5] progressmeter: protect with a mutex

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

18.05.2021 12:40, Emanuele Giuseppe Esposito wrote:
> Progressmeter is protected by the AioContext mutex, which
> is taken by the block jobs and their caller (like blockdev).
> 
> We would like to remove the dependency of block layer code on the
> AioContext mutex, since most drivers and the core I/O code are already
> not relying on it.
> 
> Create a new C file to implement the ProgressMeter API, but keep the
> struct as public, to avoid forcing allocation on the heap.
> 
> Also add a mutex to be able to provide an accurate snapshot of the
> progress values to the caller.
> 
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

patch changed a lot, so you can't keep Stefan's r-b. r-b should be kept if patch is unchanged.


> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
>   block/meson.build             |  1 +
>   block/progress_meter.c        | 64 +++++++++++++++++++++++++++++++++++
>   blockjob.c                    | 33 +++++++++++++-----
>   include/qemu/progress_meter.h | 34 +++++++++++--------
>   job-qmp.c                     |  8 +++--
>   job.c                         |  3 ++
>   qemu-img.c                    |  9 +++--
>   7 files changed, 124 insertions(+), 28 deletions(-)
>   create mode 100644 block/progress_meter.c
> 
> diff --git a/block/meson.build b/block/meson.build
> index d21990ec95..90efd21ecf 100644
> --- a/block/meson.build
> +++ b/block/meson.build
> @@ -13,6 +13,7 @@ block_ss.add(files(
>     'commit.c',
>     'copy-on-read.c',
>     'preallocate.c',
> +  'progress_meter.c',
>     'create.c',
>     'crypto.c',
>     'dirty-bitmap.c',
> diff --git a/block/progress_meter.c b/block/progress_meter.c
> new file mode 100644
> index 0000000000..aa2e60248c
> --- /dev/null
> +++ b/block/progress_meter.c
> @@ -0,0 +1,64 @@
> +/*
> + * Helper functionality for some process progress tracking.
> + *
> + * Copyright (c) 2011 IBM Corp.
> + * Copyright (c) 2012, 2018 Red Hat, Inc.
> + * Copyright (c) 2020 Virtuozzo International GmbH
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a copy
> + * of this software and associated documentation files (the "Software"), to deal
> + * in the Software without restriction, including without limitation the rights
> + * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
> + * copies of the Software, and to permit persons to whom the Software is
> + * furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
> + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
> + * THE SOFTWARE.
> + */
> +#include "qemu/osdep.h"
> +#include "qemu/progress_meter.h"
> +
> +void progress_init(ProgressMeter *pm)
> +{
> +    qemu_mutex_init(&pm->lock);
> +}
> +
> +void progress_destroy(ProgressMeter *pm)
> +{
> +    qemu_mutex_destroy(&pm->lock);
> +}
> +
> +void progress_get_snapshot(ProgressMeter *pm, uint64_t *current,
> +                           uint64_t *total)
> +{
> +    QEMU_LOCK_GUARD(&pm->lock);
> +
> +    *current = pm->current;
> +    *total = pm->total;
> +}
> +
> +void progress_work_done(ProgressMeter *pm, uint64_t done)
> +{
> +    QEMU_LOCK_GUARD(&pm->lock);
> +    pm->current += done;
> +}
> +
> +void progress_set_remaining(ProgressMeter *pm, uint64_t remaining)
> +{
> +    QEMU_LOCK_GUARD(&pm->lock);
> +    pm->total = pm->current + remaining;
> +}
> +
> +void progress_increase_remaining(ProgressMeter *pm, uint64_t delta)
> +{
> +    QEMU_LOCK_GUARD(&pm->lock);
> +    pm->total += delta;
> +}

That's not what I meant. If we move only function to c file, this doesn't make real sense. If we want encapsulation, we should move the structure definition itself to the c file too. Than, you'll need _new / _free functions instead of _init / _destroy, because we'll move to heap allocation for progress meter. Also, if we go this way, please make at least two patches:

1. move progress meter (functions and structure) to own c file, modify meson.build

2. add thread-safety





-- 
Best regards,
Vladimir