block: rename and alter bdrv_all_find_snapshot semantics

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.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210204124834.774401-7-berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

2 files changed, 13 insertions, 8 deletions

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index 9cc5d4b51e..75d7fa9510 100644
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -954,7 +954,7 @@ 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 0b129bee8f..e8ae9a28c1 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,