[PATCH v5 05/10] block: rename and alter bdrv_all_find_snapshot semantics

["Daniel P. Berrangé" <berrange@redhat.com>]

Currently bdrv_all_find_snapshot() will return 0 if it finds
a snapshot, -1 if an error occurs, or if it fails to find a
snapshot. New callers to be added want to distinguish between
the error scenario and failing to find a snapshot.

Rename it to bdrv_all_has_snapshot and make it return -1 on
error, 0 if no snapshot is found and 1 if snapshot is found.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 block/monitor/block-hmp-cmds.c |  2 +-
 block/snapshot.c               | 19 ++++++++++++-------
 include/block/snapshot.h       |  6 +++---
 migration/savevm.c             |  7 ++++++-
 4 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index 4a1fc1d6b0..2b38a0013e 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -952,7 +952,7 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     total = 0;
     for (i = 0; i < nb_sns; i++) {
         SnapshotEntry *next_sn;
-        if (bdrv_all_find_snapshot(sn_tab[i].name, false, NULL, NULL) == 0) {
+        if (bdrv_all_has_snapshot(sn_tab[i].name, false, NULL, NULL) == 1) {
             global_snapshots[total] = i;
             total++;
             QTAILQ_FOREACH(image_entry, &image_list, next) {
diff --git a/block/snapshot.c b/block/snapshot.c
index 2c3edd9922..e1dc87e9da 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -603,9 +603,9 @@ int bdrv_all_goto_snapshot(const char *name,
     return 0;
 }
 
-int bdrv_all_find_snapshot(const char *name,
-                           bool has_devices, strList *devices,
-                           Error **errp)
+int bdrv_all_has_snapshot(const char *name,
+                          bool has_devices, strList *devices,
+                          Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
@@ -627,15 +627,20 @@ int bdrv_all_find_snapshot(const char *name,
         }
         aio_context_release(ctx);
         if (ret < 0) {
-            error_setg(errp, "Could not find snapshot '%s' on '%s'",
-                       name, bdrv_get_device_or_node_name(bs));
-            return -1;
+            if (ret == -ENOENT) {
+                return 0;
+            } else {
+                error_setg_errno(errp, errno,
+                                 "Could not check snapshot '%s' on '%s'",
+                                 name, bdrv_get_device_or_node_name(bs));
+                return -1;
+            }
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
-    return 0;
+    return 1;
 }
 
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 4d25f17728..ce0fcff8e3 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -84,9 +84,9 @@ int bdrv_all_delete_snapshot(const char *name,
 int bdrv_all_goto_snapshot(const char *name,
                            bool has_devices, strList *devices,
                            Error **errp);
-int bdrv_all_find_snapshot(const char *name,
-                           bool has_devices, strList *devices,
-                           Error **errp);
+int bdrv_all_has_snapshot(const char *name,
+                          bool has_devices, strList *devices,
+                          Error **errp);
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,
diff --git a/migration/savevm.c b/migration/savevm.c
index d89d8fe605..63578c461a 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2877,10 +2877,15 @@ int load_snapshot(const char *name, Error **errp)
     if (!bdrv_all_can_snapshot(false, NULL, errp)) {
         return -1;
     }
-    ret = bdrv_all_find_snapshot(name, false, NULL, errp);
+    ret = bdrv_all_has_snapshot(name, false, NULL, errp);
     if (ret < 0) {
         return -1;
     }
+    if (ret == 0) {
+        error_setg(errp, "Snapshot '%s' does not exist in one or more devices",
+                   name);
+        return -1;
+    }
 
     bs_vm_state = bdrv_all_find_vmstate_bs(NULL, false, NULL, errp);
     if (!bs_vm_state) {
-- 
2.26.2