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Re: [Qemu-devel] [PATCH v2 1/4] blockjob: Allow nested pause
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v2 1/4] blockjob: Allow nested pause |
Date: |
Fri, 03 Apr 2015 16:13:55 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 |
On 03/04/2015 16:05, Fam Zheng wrote:
> This patch changes block_job_pause to increase the pause counter and
> block_job_resume to decrease it.
>
> The counter will allow calling block_job_pause/block_job_resume
> unconditionally on a job when we need to suspend the IO temporarily.
>
> From now on, each block_job_resume must be paired with a block_job_pause
> to keep the counter balanced.
>
> The user pause from QMP or HMP will only trigger block_job_pause once
> until it's resumed, this is achieved by adding a user_paused flag in
> BlockJob.
>
> One occurrence of block_job_resume in mirror_complete is replaced with
> block_job_enter which does what is necessary.
>
> In block_job_cancel, the cancel flag is good enough to instruct
> coroutines to quit loop, so use block_job_enter to replace the unpaired
> block_job_resume.
>
> Upon block job IO error, user is notified about the entering to the
> pause state, so this pause belongs to user pause, set the flag
> accordingly and expect a matching QMP resume.
>
> Signed-off-by: Fam Zheng <address@hidden>
> ---
> block/mirror.c | 2 +-
> blockdev.c | 8 +++++---
> blockjob.c | 23 +++++++++++++++++------
> include/block/blockjob.h | 20 ++++++++++++++++----
> 4 files changed, 39 insertions(+), 14 deletions(-)
>
> diff --git a/block/mirror.c b/block/mirror.c
> index 4056164..65b1718 100644
> --- a/block/mirror.c
> +++ b/block/mirror.c
> @@ -634,7 +634,7 @@ static void mirror_complete(BlockJob *job, Error **errp)
> }
>
> s->should_complete = true;
> - block_job_resume(job);
> + block_job_enter(&s->common);
> }
>
> static const BlockJobDriver mirror_job_driver = {
> diff --git a/blockdev.c b/blockdev.c
> index fbb3a79..9132d69 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -2699,7 +2699,7 @@ void qmp_block_job_cancel(const char *device,
> force = false;
> }
>
> - if (job->paused && !force) {
> + if (job->user_paused && !force) {
> error_setg(errp, "The block job for device '%s' is currently paused",
> device);
> goto out;
> @@ -2716,10 +2716,11 @@ void qmp_block_job_pause(const char *device, Error
> **errp)
> AioContext *aio_context;
> BlockJob *job = find_block_job(device, &aio_context, errp);
>
> - if (!job) {
> + if (!job || job->user_paused) {
> return;
> }
>
> + job->user_paused = true;
> trace_qmp_block_job_pause(job);
> block_job_pause(job);
> aio_context_release(aio_context);
> @@ -2730,10 +2731,11 @@ void qmp_block_job_resume(const char *device, Error
> **errp)
> AioContext *aio_context;
> BlockJob *job = find_block_job(device, &aio_context, errp);
>
> - if (!job) {
> + if (!job || !job->user_paused) {
> return;
> }
>
> + job->user_paused = false;
> trace_qmp_block_job_resume(job);
> block_job_resume(job);
> aio_context_release(aio_context);
> diff --git a/blockjob.c b/blockjob.c
> index ba2255d..2755465 100644
> --- a/blockjob.c
> +++ b/blockjob.c
> @@ -107,7 +107,7 @@ void block_job_set_speed(BlockJob *job, int64_t speed,
> Error **errp)
>
> void block_job_complete(BlockJob *job, Error **errp)
> {
> - if (job->paused || job->cancelled || !job->driver->complete) {
> + if (job->pause_count || job->cancelled || !job->driver->complete) {
> error_set(errp, QERR_BLOCK_JOB_NOT_READY,
> bdrv_get_device_name(job->bs));
> return;
> @@ -118,17 +118,26 @@ void block_job_complete(BlockJob *job, Error **errp)
>
> void block_job_pause(BlockJob *job)
> {
> - job->paused = true;
> + job->pause_count++;
> }
>
> bool block_job_is_paused(BlockJob *job)
> {
> - return job->paused;
> + return job->pause_count > 0;
> }
>
> void block_job_resume(BlockJob *job)
> {
> - job->paused = false;
> + assert(job->pause_count > 0);
> + job->pause_count--;
> + if (job->pause_count) {
> + return;
> + }
> + block_job_enter(job);
> +}
> +
> +void block_job_enter(BlockJob *job)
> +{
> block_job_iostatus_reset(job);
> if (job->co && !job->busy) {
> qemu_coroutine_enter(job->co, NULL);
> @@ -138,7 +147,7 @@ void block_job_resume(BlockJob *job)
> void block_job_cancel(BlockJob *job)
> {
> job->cancelled = true;
> - block_job_resume(job);
> + block_job_enter(job);
> }
>
> bool block_job_is_cancelled(BlockJob *job)
> @@ -258,7 +267,7 @@ BlockJobInfo *block_job_query(BlockJob *job)
> info->device = g_strdup(bdrv_get_device_name(job->bs));
> info->len = job->len;
> info->busy = job->busy;
> - info->paused = job->paused;
> + info->paused = job->pause_count > 0;
> info->offset = job->offset;
> info->speed = job->speed;
> info->io_status = job->iostatus;
> @@ -335,6 +344,8 @@ BlockErrorAction block_job_error_action(BlockJob *job,
> BlockDriverState *bs,
> IO_OPERATION_TYPE_WRITE,
> action, &error_abort);
> if (action == BLOCK_ERROR_ACTION_STOP) {
> + /* make the pause user visible, which will be resumed from QMP. */
> + job->user_paused = true;
> block_job_pause(job);
> block_job_iostatus_set_err(job, error);
> if (bs != job->bs) {
> diff --git a/include/block/blockjob.h b/include/block/blockjob.h
> index b6d4ebb..9f4b20d 100644
> --- a/include/block/blockjob.h
> +++ b/include/block/blockjob.h
> @@ -79,10 +79,14 @@ struct BlockJob {
> bool cancelled;
>
> /**
> - * Set to true if the job is either paused, or will pause itself
> - * as soon as possible (if busy == true).
> + * Counter for pause request. If non-zero, the block job will pause.
Why not keep the more complete comment ("If non-zero, the block job is
either paused, or if busy == true will pause itself as soon as possible")?
> */
> - bool paused;
> + int pause_count;
> +
> + /**
> + * Set to true if the job is paused by user.
... and can be unpaused with the block-job-resume QMP command.
> + */
> + bool user_paused;
>
> /**
> * Set to false by the job while it is in a quiescent state, where
> @@ -225,11 +229,19 @@ void block_job_pause(BlockJob *job);
> * block_job_resume:
> * @job: The job to be resumed.
> *
> - * Resume the specified job.
> + * Resume the specified job. Must be paired with a preceding
> block_job_pause.
> */
> void block_job_resume(BlockJob *job);
>
> /**
> + * block_job_enter:
> + * @job: The job to enter.
> + *
> + * Continue the specified job by entering the coroutine.
> + */
> +void block_job_enter(BlockJob *job);
> +
> +/**
> * block_job_event_cancelled:
> * @job: The job whose information is requested.
> *
>
Apart from this,
Reviewed-by: Paolo Bonzini <address@hidden>