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>

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) {

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,
+int bdrv_all_has_snapshot(const char *name,
-                           bool has_devices, strList *devices,
+                          bool has_devices, strList *devices,
-                           Error **errp)
+                          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'",
+            if (ret == -ENOENT) {
-                       name, bdrv_get_device_or_node_name(bs));
+                return 0;
-            return -1;
+            } 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,

include/block/snapshot.h

@@ -85,9 +85,9 @@ 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,
+int bdrv_all_has_snapshot(const char *name,
-                           bool has_devices, strList *devices,
+                          bool has_devices, strList *devices,
-                           Error **errp);
+                          Error **errp);
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,

migration/savevm.c

@@ -2977,10 +2977,15 @@ bool load_snapshot(const char *name, Error **errp)
     if (!bdrv_all_can_snapshot(false, NULL, errp)) {
         return false;
     }
-    ret = bdrv_all_find_snapshot(name, false, NULL, errp);
+    ret = bdrv_all_has_snapshot(name, false, NULL, errp);
     if (ret < 0) {
         return false;
     }
+    if (ret == 0) {
+        error_setg(errp, "Snapshot '%s' does not exist in one or more devices",
+                   name);
+        return false;
+    }
 
     bs_vm_state = bdrv_all_find_vmstate_bs(NULL, false, NULL, errp);
     if (!bs_vm_state) {

replay/replay-debugging.c

@@ -143,6 +143,7 @@ static char *replay_find_nearest_snapshot(int64_t icount,
     QEMUSnapshotInfo *sn_tab;
     QEMUSnapshotInfo *nearest = NULL;
     char *ret = NULL;
+    int rv;
     int nb_sns, i;
     AioContext *aio_context;
 
@@ -159,7 +160,10 @@ static char *replay_find_nearest_snapshot(int64_t icount,
     aio_context_release(aio_context);
 
     for (i = 0; i < nb_sns; i++) {
-        if (bdrv_all_find_snapshot(sn_tab[i].name, false, NULL, NULL) == 0) {
+        rv = bdrv_all_has_snapshot(sn_tab[i].name, false, NULL, NULL);
+        if (rv < 0)
+            goto fail;
+        if (rv == 1) {
             if (sn_tab[i].icount != -1ULL
                 && sn_tab[i].icount <= icount
                 && (!nearest || nearest->icount < sn_tab[i].icount)) {