[pve-devel] [RFC/PATCH v2 qemu 1/3] PVE-Backup: create jobs: correctly cancel in error scenario

[Fabian Ebner <f.ebner@proxmox.com>]

The first call to job_cancel_sync() will cancel and free all jobs in
the transaction, so ensure that it's called only once and get rid of
the job_unref() that would operate on freed memory.

It's also necessary to NULL backup_state.pbs in the error scenario,
because a subsequent backup_cancel QMP call (as happens in PVE when
the backup QMP command fails) would try to call proxmox_backup_abort()
and run into a segfault.

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
---

All patches are intended to be ordered after
0038-PVE-Backup-Don-t-block-on-finishing-and-cleanup-crea.patch
or could also be squashed into that (while lifting the commit message
to the main repo). Of course I can also send that directly if this is
ACKed.

Would be glad if someone could confirm that the cleanup for PBS is
correct like this. I didn't have the time to look into all the details
there yet.

New in v2.

 pve-backup.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/pve-backup.c b/pve-backup.c
index 6f05796fad..dfaf4c93f8 100644
--- a/pve-backup.c
+++ b/pve-backup.c
@@ -509,6 +509,11 @@ static void create_backup_jobs_bh(void *opaque) {
     }
 
     if (*errp) {
+        /*
+         * It's enough to cancel one job in the transaction, the rest will
+         * follow automatically.
+         */
+        bool canceled = false;
         l = backup_state.di_list;
         while (l) {
             PVEBackupDevInfo *di = (PVEBackupDevInfo *)l->data;
@@ -519,12 +524,12 @@ static void create_backup_jobs_bh(void *opaque) {
                 di->target = NULL;
             }
 
-            if (di->job) {
+            if (!canceled && di->job) {
                 AioContext *ctx = di->job->job.aio_context;
                 aio_context_acquire(ctx);
                 job_cancel_sync(&di->job->job, true);
-                job_unref(&di->job->job);
                 aio_context_release(ctx);
+                canceled = true;
             }
         }
     }
@@ -974,6 +979,7 @@ err:
 
     if (pbs) {
         proxmox_backup_disconnect(pbs);
+        backup_state.pbs = NULL;
     }
 
     if (backup_dir) {
-- 
2.30.2