[Qemu-devel] [PATCH COLO-Frame v8 17/34] COLO failover: Introduce state to record failover process

[zhanghailiang]

When handling failover, we do different things according to the different stage
of failover process, here we introduce a global atomic variable to record the
status of failover.

We add four failover status to indicate the different stage of failover process.
You should use the helpers to get and set the value.

Signed-off-by: zhanghailiang <address@hidden>
---
 include/migration/failover.h | 10 ++++++++++
 migration/colo-failover.c    | 29 +++++++++++++++++++++++++++++
 migration/colo.c             |  3 +++
 trace-events                 |  1 +
 4 files changed, 43 insertions(+)

diff --git a/include/migration/failover.h b/include/migration/failover.h
index 1785b52..882c625 100644
--- a/include/migration/failover.h
+++ b/include/migration/failover.h
@@ -15,6 +15,16 @@
 
 #include "qemu-common.h"
 
+typedef enum COLOFailoverStatus {
+    FAILOVER_STATUS_NONE = 0,
+    FAILOVER_STATUS_REQUEST = 1, /* Request but not handled */
+    FAILOVER_STATUS_HANDLING = 2, /* In the process of handling failover */
+    FAILOVER_STATUS_COMPLETED = 3, /* Finish the failover process */
+} COLOFailoverStatus;
+
+void failover_init_state(void);
+int failover_set_state(int old_state, int new_state);
+int failover_get_state(void);
 void failover_request_active(Error **errp);
 
 #endif
diff --git a/migration/colo-failover.c b/migration/colo-failover.c
index af068d3..94d047a 100644
--- a/migration/colo-failover.c
+++ b/migration/colo-failover.c
@@ -14,8 +14,11 @@
 #include "migration/failover.h"
 #include "qmp-commands.h"
 #include "qapi/qmp/qerror.h"
+#include "qemu/error-report.h"
+#include "trace.h"
 
 static QEMUBH *failover_bh;
+static COLOFailoverStatus failover_state;
 
 static void colo_failover_bh(void *opaque)
 {
@@ -26,10 +29,36 @@ static void colo_failover_bh(void *opaque)
 
 void failover_request_active(Error **errp)
 {
+   if (failover_set_state(FAILOVER_STATUS_NONE, FAILOVER_STATUS_REQUEST)
+         != FAILOVER_STATUS_NONE) {
+        error_setg(errp, "COLO failover is already actived");
+        return;
+    }
     failover_bh = qemu_bh_new(colo_failover_bh, NULL);
     qemu_bh_schedule(failover_bh);
 }
 
+void failover_init_state(void)
+{
+    failover_state = FAILOVER_STATUS_NONE;
+}
+
+int failover_set_state(int old_state, int new_state)
+{
+    int old;
+
+    old = atomic_cmpxchg(&failover_state, old_state, new_state);;
+    if (old == old_state) {
+        trace_colo_failover_set_state(new_state);
+    }
+    return old;
+}
+
+int failover_get_state(void)
+{
+    return atomic_read(&failover_state);
+}
+
 void qmp_colo_lost_heartbeat(Error **errp)
 {
     if (get_colo_mode() == COLO_MODE_UNKNOWN) {
diff --git a/migration/colo.c b/migration/colo.c
index 1a08fec..6f40a82 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -227,6 +227,8 @@ static void *colo_thread(void *opaque)
     QEMUFile *colo_control = NULL;
     int ret;
 
+    failover_init_state();
+
     colo_control = qemu_fopen_socket(qemu_get_fd(s->file), "rb");
     if (!colo_control) {
         error_report("Open colo_control failed!");
@@ -339,6 +341,7 @@ void *colo_process_incoming_checkpoints(void *opaque)
 
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_COLO);
+    failover_init_state();
 
     ctl = qemu_fopen_socket(fd, "wb");
     if (!ctl) {
diff --git a/trace-events b/trace-events
index 86d4c49..3df120b 100644
--- a/trace-events
+++ b/trace-events
@@ -1476,6 +1476,7 @@ 
rdma_start_outgoing_migration_after_rdma_source_init(void) ""
 colo_vm_state_change(const char *old, const char *new) "Change '%s' => '%s'"
 colo_ctl_put(const char *msg) "Send '%s'"
 colo_ctl_get(const char *msg) "Receive '%s'"
+colo_failover_set_state(int new_state) "new state %d"
 
 # kvm-all.c
 kvm_ioctl(int type, void *arg) "type 0x%x, arg %p"
-- 
1.8.3.1