Re: [PATCH] qemu: blockjob: Transition into 'ready' state only from expected states

In certain rare occasions qemu can transition a block job which was already 'ready' into 'standby' and then back. If this happens in the following order libvirt will get confused about the actual job state: 1) the block copy job is 'ready' (job->state == QEMU_BLOCKJOB_STATE_READY) 2) user calls qemuDomainBlockJobAbort with VIR_DOMAIN_BLOCK_JOB_ABORT_PIVOT flag but without VIR_DOMAIN_BLOCK_JOB_ABORT_ASYNC 3) the block job is switched to synchronous event handling 4) the block job blips to 'standby' and back to 'ready', the event is not processed since the blockjob is in sync mode for now 5) qemuDomainBlockJobPivot is called: 5.1) 'job-complete' QMP command is issued 5.2) job->state is set to QEMU_BLOCKJOB_STATE_PIVOTING 6) code for synchronous-wait for the job completion in qemuDomainBlockJobAbort is invoked 7) the waiting loop calls qemuBlockJobUpdate: 7.1) job->newstate is QEMU_BLOCKJOB_STATE_READY due to 4) 7.2) qemuBlockJobEventProcess is called 7.3) the handler for QEMU_BLOCKJOB_STATE_READY overwrites job->state from QEMU_BLOCKJOB_STATE_PIVOTING to QEMU_BLOCKJOB_STATE_READY 8) qemuDomainBlockJobAbort is looking for a finished job, so waits again 9) qemu finishes the blockjob and transitions it into 'concluded' state 10) qemuBlockJobUpdate is triggered again, this time finalizing the job. 10.1) job->newstate is = QEMU_BLOCKJOB_STATE_CONCLUDED job->state is = QEMU_BLOCKJOB_STATE_READY 10.2) qemuBlockJobEventProcessConcluded is called, the function checks whether there was an error with the blockjob. Since there was no error job->newstate becomes QEMU_BLOCKJOB_STATE_COMPLETED. 10.3) qemuBlockJobEventProcessConcludedTransition selects the action for the appropriate block job type where we have: case QEMU_BLOCKJOB_TYPE_COPY: if (job->state == QEMU_BLOCKJOB_STATE_PIVOTING && success) qemuBlockJobProcessEventConcludedCopyPivot(driver, vm, job, asyncJob); else qemuBlockJobProcessEventConcludedCopyAbort(driver, vm, job, asyncJob); break;

Since job->state is QEMU_BLOCKJOB_STATE_READY, qemuBlockJobProcessEventConcludedCopyAbort is called. This patch forbids transitions to QEMU_BLOCKJOB_STATE_READY if the previous job state isn't QEMU_BLOCKJOB_STATE_RUNNING or QEMU_BLOCKJOB_STATE_NEW. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1951507 Signed-off-by: Peter Krempa <pkrempa(a)redhat.com&gt; --- src/qemu/qemu_blockjob.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/src/qemu/qemu_blockjob.c b/src/qemu/qemu_blockjob.c index 21fcc29ddb..9ae4500f4d 100644 --- a/src/qemu/qemu_blockjob.c +++ b/src/qemu/qemu_blockjob.c @@ -1697,14 +1697,21 @@ qemuBlockJobEventProcess(virQEMUDriver *driver, break; case QEMU_BLOCKJOB_STATE_READY: - /* mirror may be NULL for copy job corresponding to migration */ - if (job->disk) { - job->disk->mirrorState = VIR_DOMAIN_DISK_MIRROR_STATE_READY; - qemuBlockJobEmitEvents(driver, vm, job->disk, job->type, job->newstate); + /* in certain cases qemu can blip out and back into 'ready' state for + * a blockjob. In cases when we already are past RUNNING the job such + * as when pivoting/aborting this could reset the internally set job + * state, thus we ignore it if the job isn't in expected state */ + if (job->state == QEMU_BLOCKJOB_STATE_NEW || + job->state == QEMU_BLOCKJOB_STATE_RUNNING) { + /* mirror may be NULL for copy job corresponding to migration */ + if (job->disk) { + job->disk->mirrorState = VIR_DOMAIN_DISK_MIRROR_STATE_READY; + qemuBlockJobEmitEvents(driver, vm, job->disk, job->type, job->newstate); + } + job->state = job->newstate; + qemuDomainSaveStatus(vm); } - job->state = job->newstate; job->newstate = -1; - qemuDomainSaveStatus(vm); break; case QEMU_BLOCKJOB_STATE_NEW: -- 2.30.2