blockjob: Allow nested pause

Enterprise / Virtualization / QEMU - Fam Zheng [redhat.com] - 28 April 2015 08:36 UTC

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 .--Stefan]

751ebd7 blockjob: Allow nested pause
block/mirror.c | 2 +-
blockdev.c | 8 +++++---
blockjob.c | 23 +++++++++++++++++------
include/block/blockjob.h | 22 ++++++++++++++++++----
4 files changed, 41 insertions(+), 14 deletions(-)

Upstream: git.qemu.org

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