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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
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22
include/block/blockjob.h
View file

@ -79,10 +79,16 @@ 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 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. 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
@ -225,10 +231,18 @@ 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.