On Fri, Apr 03, 2015 at 04:13:55PM +0200, Paolo Bonzini wrote:
>
>
> 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 <f...@redhat.com>
> > ---
> > 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.I squashed in your suggestions.
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