From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001

From: Stefan Reiter <s.reiter@proxmox.com>

Date: Thu, 20 Aug 2020 14:31:59 +0200

Subject: [PATCH] PVE: Add sequential job transaction support

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

---

 include/qemu/job.h | 12 ++++++++++++

 job.c              | 31 +++++++++++++++++++++++++++++++

 2 files changed, 43 insertions(+)

diff --git a/include/qemu/job.h b/include/qemu/job.h

index 41162ed494..6662c63519 100644

--- a/include/qemu/job.h

+++ b/include/qemu/job.h

@@ -285,6 +285,18 @@ typedef enum JobCreateFlags {

  */

 JobTxn *job_txn_new(void);

+/**

+ * Create a new transaction and set it to sequential mode, i.e. run all jobs

+ * one after the other instead of at the same time.

+ */

+JobTxn *job_txn_new_seq(void);

+

+/**

+ * Helper method to start the first job in a sequential transaction to kick it

+ * off. Other jobs will be run after this one completes.

+ */

+void job_txn_start_seq(JobTxn *txn);

+

 /**

  * Release a reference that was previously acquired with job_txn_add_job or

  * job_txn_new. If it's the last reference to the object, it will be freed.

diff --git a/job.c b/job.c

index 44eec9a441..a0753ff2f1 100644

--- a/job.c

+++ b/job.c

@@ -72,6 +72,8 @@ struct JobTxn {

     /* Reference count */

     int refcnt;

+

+    bool sequential;

 };

 /* Right now, this mutex is only needed to synchronize accesses to job->busy

@@ -102,6 +104,25 @@ JobTxn *job_txn_new(void)

     return txn;

 }

+JobTxn *job_txn_new_seq(void)

+{

+    JobTxn *txn = job_txn_new();

+    txn->sequential = true;

+    return txn;

+}

+

+void job_txn_start_seq(JobTxn *txn)

+{

+    assert(txn->sequential);

+    assert(!txn->aborting);

+

+    Job *first = QLIST_FIRST(&txn->jobs);

+    assert(first);

+    assert(first->status == JOB_STATUS_CREATED);

+

+    job_start(first);

+}

+

 static void job_txn_ref(JobTxn *txn)

 {

     txn->refcnt++;

@@ -850,6 +871,9 @@ static void job_completed_txn_success(Job *job)

      */

     QLIST_FOREACH(other_job, &txn->jobs, txn_list) {

         if (!job_is_completed(other_job)) {

+            if (txn->sequential) {

+                job_start(other_job);

+            }

             return;

         }

         assert(other_job->ret == 0);

@@ -1020,6 +1044,13 @@ int job_finish_sync(Job *job, void (*finish)(Job *, Error **errp), Error **errp)

         return -EBUSY;

     }

+    /* in a sequential transaction jobs with status CREATED can appear at time

+     * of cancelling, these have not begun work so job_enter won't do anything,

+     * let's ensure they are marked as ABORTING if required */

+    if (job->status == JOB_STATUS_CREATED && job->txn->sequential) {

+        job_update_rc(job);

+    }

+

     AIO_WAIT_WHILE(job->aio_context,

                    (job_enter(job), !job_is_completed(job)));