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blockjob: Allow nested pause

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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.

[Extended doc comments as suggested by Paolo Bonzini
<pbonzini@redhat.com>.
--Stefan]

Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-id: 1428069921-2957-2-git-send-email-famz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fam Zheng 2015-04-03 22:05:18 +08:00 • committed by Kevin Wolf
parent 199667a8c8
commit 751ebd76e6
4 changed files with 41 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

8
blockdev.c
View file

@ -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);