[PATCH v3 11/26] migration: Add Error** argument to qemu_savevm_state_setup()

Cédric Le Goater posted 26 patches 8 months, 3 weeks ago
Maintainers: Stefano Stabellini <sstabellini@kernel.org>, Anthony Perard <anthony.perard@citrix.com>, Paul Durrant <paul@xen.org>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <richard.henderson@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Nicholas Piggin <npiggin@gmail.com>, Daniel Henrique Barboza <danielhb413@gmail.com>, "Cédric Le Goater" <clg@kaod.org>, David Gibson <david@gibson.dropbear.id.au>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Halil Pasic <pasic@linux.ibm.com>, Christian Borntraeger <borntraeger@linux.ibm.com>, Eric Farman <farman@linux.ibm.com>, Thomas Huth <thuth@redhat.com>, David Hildenbrand <david@redhat.com>, Ilya Leoshkevich <iii@linux.ibm.com>, Alex Williamson <alex.williamson@redhat.com>, Peter Xu <peterx@redhat.com>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Fabiano Rosas <farosas@suse.de>, Stefan Hajnoczi <stefanha@redhat.com>, Fam Zheng <fam@euphon.net>, Eric Blake <eblake@redhat.com>, Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>, John Snow <jsnow@redhat.com>, Hyman Huang <yong.huang@smartx.com>
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[PATCH v3 11/26] migration: Add Error** argument to qemu_savevm_state_setup()
Posted by Cédric Le Goater 8 months, 3 weeks ago
This prepares ground for the changes coming next which add an Error**
argument to the .save_setup() handler. Callers of qemu_savevm_state_setup()
now handle the error and fail earlier setting the migration state from
MIGRATION_STATUS_SETUP to MIGRATION_STATUS_FAILED.

Since the previous behavior was to ignore errors at this step of
migration, this change should be examined closely to check that
cleanups are still correctly done.

Signed-off-by: Cédric Le Goater <clg@redhat.com>
---

 Changes in v3:
 
 - Set migration state to MIGRATION_STATUS_FAILED 
 - Fixed error handling to be done under lock in bg_migration_thread()
 - Made sure an error is always set in case of failure in
   qemu_savevm_state_setup()
   
 migration/savevm.h    |  2 +-
 migration/migration.c | 27 ++++++++++++++++++++++++---
 migration/savevm.c    | 24 ++++++++++++++----------
 3 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/migration/savevm.h b/migration/savevm.h
index 74669733dd63a080b765866c703234a5c4939223..9ec96a995c93a42aad621595f0ed58596c532328 100644
--- a/migration/savevm.h
+++ b/migration/savevm.h
@@ -32,7 +32,7 @@
 bool qemu_savevm_state_blocked(Error **errp);
 void qemu_savevm_non_migratable_list(strList **reasons);
 int qemu_savevm_state_prepare(Error **errp);
-void qemu_savevm_state_setup(QEMUFile *f);
+int qemu_savevm_state_setup(QEMUFile *f, Error **errp);
 bool qemu_savevm_state_guest_unplug_pending(void);
 int qemu_savevm_state_resume_prepare(MigrationState *s);
 void qemu_savevm_state_header(QEMUFile *f);
diff --git a/migration/migration.c b/migration/migration.c
index bab68bcbef33edc9a78c2f4ebeccee690f4b1786..ff2d4bf9d153444d58d21f761071fe811034ea86 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -3360,6 +3360,8 @@ static void *migration_thread(void *opaque)
     int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
     MigThrError thr_error;
     bool urgent = false;
+    Error *local_err = NULL;
+    int ret;
 
     thread = migration_threads_add("live_migration", qemu_get_thread_id());
 
@@ -3403,9 +3405,17 @@ static void *migration_thread(void *opaque)
     }
 
     bql_lock();
-    qemu_savevm_state_setup(s->to_dst_file);
+    ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
     bql_unlock();
 
+    if (ret) {
+        migrate_set_error(s, local_err);
+        error_free(local_err);
+        migrate_set_state(&s->state, MIGRATION_STATUS_SETUP,
+                          MIGRATION_STATUS_FAILED);
+        goto out;
+     }
+
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
@@ -3482,6 +3492,9 @@ static void *bg_migration_thread(void *opaque)
     MigThrError thr_error;
     QEMUFile *fb;
     bool early_fail = true;
+    bool setup_fail = true;
+    Error *local_err = NULL;
+    int ret;
 
     rcu_register_thread();
     object_ref(OBJECT(s));
@@ -3515,9 +3528,16 @@ static void *bg_migration_thread(void *opaque)
 
     bql_lock();
     qemu_savevm_state_header(s->to_dst_file);
-    qemu_savevm_state_setup(s->to_dst_file);
+    ret = qemu_savevm_state_setup(s->to_dst_file, &local_err);
+    if (ret) {
+        migrate_set_error(s, local_err);
+        error_free(local_err);
+        goto fail;
+    }
     bql_unlock();
 
+    setup_fail = false;
+
     qemu_savevm_wait_unplug(s, MIGRATION_STATUS_SETUP,
                                MIGRATION_STATUS_ACTIVE);
 
@@ -3584,7 +3604,8 @@ static void *bg_migration_thread(void *opaque)
 
 fail:
     if (early_fail) {
-        migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
+        migrate_set_state(&s->state,
+                setup_fail ? MIGRATION_STATUS_SETUP : MIGRATION_STATUS_ACTIVE,
                 MIGRATION_STATUS_FAILED);
         bql_unlock();
     }
diff --git a/migration/savevm.c b/migration/savevm.c
index e400706e61e06d2d1d03a11aed14f30a243833f2..3ae4328b95d554cb4855f96989f8685daf4b8407 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1309,11 +1309,11 @@ int qemu_savevm_state_prepare(Error **errp)
     return 0;
 }
 
-void qemu_savevm_state_setup(QEMUFile *f)
+int qemu_savevm_state_setup(QEMUFile *f, Error **errp)
 {
+    ERRP_GUARD();
     MigrationState *ms = migrate_get_current();
     SaveStateEntry *se;
-    Error *local_err = NULL;
     int ret = 0;
 
     json_writer_int64(ms->vmdesc, "page_size", qemu_target_page_size());
@@ -1322,10 +1322,9 @@ void qemu_savevm_state_setup(QEMUFile *f)
     trace_savevm_state_setup();
     QTAILQ_FOREACH(se, &savevm_state.handlers, entry) {
         if (se->vmsd && se->vmsd->early_setup) {
-            ret = vmstate_save(f, se, ms->vmdesc, &local_err);
+            ret = vmstate_save(f, se, ms->vmdesc, errp);
             if (ret) {
-                migrate_set_error(ms, local_err);
-                error_report_err(local_err);
+                migrate_set_error(ms, *errp);
                 qemu_file_set_error(f, ret);
                 break;
             }
@@ -1345,18 +1344,19 @@ void qemu_savevm_state_setup(QEMUFile *f)
         ret = se->ops->save_setup(f, se->opaque);
         save_section_footer(f, se);
         if (ret < 0) {
+            error_setg(errp, "failed to setup SaveStateEntry with id(name): "
+                       "%d(%s): %d", se->section_id, se->idstr, ret);
             qemu_file_set_error(f, ret);
             break;
         }
     }
 
     if (ret) {
-        return;
+        return ret;
     }
 
-    if (precopy_notify(PRECOPY_NOTIFY_SETUP, &local_err)) {
-        error_report_err(local_err);
-    }
+    /* TODO: Should we check that errp is set in case of failure ? */
+    return precopy_notify(PRECOPY_NOTIFY_SETUP, errp);
 }
 
 int qemu_savevm_state_resume_prepare(MigrationState *s)
@@ -1727,7 +1727,10 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     ms->to_dst_file = f;
 
     qemu_savevm_state_header(f);
-    qemu_savevm_state_setup(f);
+    ret = qemu_savevm_state_setup(f, errp);
+    if (ret) {
+        goto cleanup;
+    }
 
     while (qemu_file_get_error(f) == 0) {
         if (qemu_savevm_state_iterate(f, false) > 0) {
@@ -1743,6 +1746,7 @@ static int qemu_savevm_state(QEMUFile *f, Error **errp)
     if (ret != 0) {
         error_setg_errno(errp, -ret, "Error while writing VM state");
     }
+cleanup:
     qemu_savevm_state_cleanup();
 
     if (ret != 0) {
-- 
2.44.0