[V5,2/8] snapshot: distinguish id and name in snapshot delete

diff --git a/block/qcow2-snapshot.c b/block/qcow2-snapshot.c
index 0caac90..47db6ad 100644
--- a/block/qcow2-snapshot.c
+++ b/block/qcow2-snapshot.c
@@ -288,31 +288,47 @@  static void find_new_snapshot_id(BlockDriverState *bs,
     snprintf(id_str, id_str_size, "%d", id_max + 1);
 }
 
-static int find_snapshot_by_id(BlockDriverState *bs, const char *id_str)
+static int find_snapshot_by_id_and_name(BlockDriverState *bs,
+                                        const char *id,
+                                        const char *name)
 {
     BDRVQcowState *s = bs->opaque;
     int i;
 
-    for(i = 0; i < s->nb_snapshots; i++) {
-        if (!strcmp(s->snapshots[i].id_str, id_str))
-            return i;
+    if (id && name) {
+        for (i = 0; i < s->nb_snapshots; i++) {
+            if (!strcmp(s->snapshots[i].id_str, id) &&
+                !strcmp(s->snapshots[i].name, name)) {
+                return i;
+            }
+        }
+    } else if (id) {
+        for (i = 0; i < s->nb_snapshots; i++) {
+            if (!strcmp(s->snapshots[i].id_str, id)) {
+                return i;
+            }
+        }
+    } else if (name) {
+        for (i = 0; i < s->nb_snapshots; i++) {
+            if (!strcmp(s->snapshots[i].name, name)) {
+                return i;
+            }
+        }
     }
+
     return -1;
 }
 
-static int find_snapshot_by_id_or_name(BlockDriverState *bs, const char *name)
+static int find_snapshot_by_id_or_name(BlockDriverState *bs,
+                                       const char *id_or_name)
 {
-    BDRVQcowState *s = bs->opaque;
-    int i, ret;
+    int ret;
 
-    ret = find_snapshot_by_id(bs, name);
-    if (ret >= 0)
+    ret = find_snapshot_by_id_and_name(bs, id_or_name, NULL);
+    if (ret >= 0) {
         return ret;
-    for(i = 0; i < s->nb_snapshots; i++) {
-        if (!strcmp(s->snapshots[i].name, name))
-            return i;
     }
-    return -1;
+    return find_snapshot_by_id_and_name(bs, NULL, id_or_name);
 }
 
 /* if no id is provided, a new one is constructed */
@@ -334,7 +350,7 @@  int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
     }
 
     /* Check that the ID is unique */
-    if (find_snapshot_by_id(bs, sn_info->id_str) >= 0) {
+    if (find_snapshot_by_id_and_name(bs, sn_info->id_str, NULL) >= 0) {
         return -EEXIST;
     }
 
@@ -531,15 +547,23 @@  fail:
     return ret;
 }
 
-int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
+int qcow2_snapshot_delete(BlockDriverState *bs,
+                          const char *snapshot_id,
+                          const char *name,
+                          Error **errp)
 {
     BDRVQcowState *s = bs->opaque;
     QCowSnapshot sn;
     int snapshot_index, ret;
+    const char *device = bdrv_get_device_name(bs);
 
     /* Search the snapshot */
-    snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
+    snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name);
     if (snapshot_index < 0) {
+        error_setg(errp,
+                   "Can't find a snapshot with ID '%s' and name '%s' "
+                   "on device '%s'",
+                   STR_PRINT_CHAR(snapshot_id), STR_PRINT_CHAR(name), device);
         return -ENOENT;
     }
     sn = s->snapshots[snapshot_index];
@@ -551,6 +575,10 @@  int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
     s->nb_snapshots--;
     ret = qcow2_write_snapshots(bs);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed to remove snapshot with ID '%s' and name '%s' from "
+                   "the snapshot list on device '%s'",
+                   STR_PRINT_CHAR(snapshot_id), STR_PRINT_CHAR(name), device);
         return ret;
     }
 
@@ -568,6 +596,9 @@  int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
     ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset,
                                          sn.l1_size, -1);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed to free the cluster and L1 table on device '%s'",
+                   device);
         return ret;
     }
     qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t),
@@ -576,6 +607,9 @@  int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
     /* must update the copied flag on the current cluster offsets */
     ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
     if (ret < 0) {
+        error_setg(errp,
+                   "Failed to update snapshot status in disk on device '%s'",
+                   device);
         return ret;
     }
 
diff --git a/block/qcow2.h b/block/qcow2.h
index 3b2d5cd..2e6c471 100644
--- a/block/qcow2.h
+++ b/block/qcow2.h
@@ -411,7 +411,10 @@  int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors);
 /* qcow2-snapshot.c functions */
 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info);
 int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id);
-int qcow2_snapshot_delete(BlockDriverState *bs, const char *snapshot_id);
+int qcow2_snapshot_delete(BlockDriverState *bs,
+                          const char *snapshot_id,
+                          const char *name,
+                          Error **errp);
 int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab);
 int qcow2_snapshot_load_tmp(BlockDriverState *bs, const char *snapshot_name);
 
diff --git a/block/rbd.c b/block/rbd.c
index cb71751..688b571 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -903,12 +903,33 @@  static int qemu_rbd_snap_create(BlockDriverState *bs,
 }
 
 static int qemu_rbd_snap_remove(BlockDriverState *bs,
-                                const char *snapshot_name)
+                                const char *snapshot_id,
+                                const char *snapshot_name,
+                                Error **errp)
 {
     BDRVRBDState *s = bs->opaque;
     int r;
+    const char *device = bdrv_get_device_name(bs);
+
+    if (snapshot_id && snapshot_id[0] != '\0') {
+        error_setg(errp,
+                   "rbd do not support snapshot id on device '%s'", device);
+        return -EINVAL;
+    }
+    /* then snapshot_id == NULL or it contain an empty line, ignore it */
+
+    if (!snapshot_name) {
+        error_setg(errp,
+                   "rbd need a valid snapshot name on device '%s'", device);
+        return -EINVAL;
+    }
 
     r = rbd_snap_remove(s->image, snapshot_name);
+    if (r < 0) {
+        error_setg_errno(errp, -r,
+                         "Failed to remove snapshot '%s' on device '%s'",
+                         snapshot_name, device);
+    }
     return r;
 }
 
diff --git a/block/sheepdog.c b/block/sheepdog.c
index b397b5b..7fdae71 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2089,7 +2089,10 @@  out:
     return ret;
 }
 
-static int sd_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
+static int sd_snapshot_delete(BlockDriverState *bs,
+                              const char *snapshot_id,
+                              const char *name,
+                              Error **errp)
 {
     /* FIXME: Delete specified snapshot id.  */
     return 0;
diff --git a/block/snapshot.c b/block/snapshot.c
index 481a3ee..cf2f4ca 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -182,18 +182,48 @@  int bdrv_snapshot_goto(BlockDriverState *bs,
     return -ENOTSUP;
 }
 
-int bdrv_snapshot_delete(BlockDriverState *bs, const char *snapshot_id)
+/**
+ * Delete an internal snapshot by @snapshot_id and @name.
+ * @bs: block device used in the operation
+ * @snapshot_id: unique snapshot ID, or NULL
+ * @name: snapshot name, or NULL
+ * @errp: location to store error
+ *
+ * If both @snapshot_id and @name are specified, delete the first one with
+ * id @snapshot_id and name @name.
+ * If only @snapshot_id is specified, delete the first one with id
+ * @snapshot_id.
+ * If only @name is specified, delete the first one with name @name.
+ * if none is specified, return -ENINVAL.
+ *
+ * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
+ * -ENOMEDIUM. If can't find one matching @id and @name, return -ENOENT.
+ * If @bs did not support internal snapshot, return -ENOTSUP. If @bs do not
+ * support parameter @snapshot_id or @name, return -EINVAL.
+ */
+int bdrv_snapshot_delete(BlockDriverState *bs,
+                         const char *snapshot_id,
+                         const char *name,
+                         Error **errp)
 {
     BlockDriver *drv = bs->drv;
     if (!drv) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
         return -ENOMEDIUM;
     }
+    if (!snapshot_id && !name) {
+        error_setg(errp, "snapshot_id and name are both NULL");
+        return -EINVAL;
+    }
     if (drv->bdrv_snapshot_delete) {
-        return drv->bdrv_snapshot_delete(bs, snapshot_id);
+        return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
     }
     if (bs->file) {
-        return bdrv_snapshot_delete(bs->file, snapshot_id);
+        return bdrv_snapshot_delete(bs->file, snapshot_id, name, errp);
     }
+    error_set(errp, QERR_BLOCK_FORMAT_FEATURE_NOT_SUPPORTED,
+              drv->format_name, bdrv_get_device_name(bs),
+              "internal snapshot");
     return -ENOTSUP;
 }
 
diff --git a/include/block/block_int.h b/include/block/block_int.h
index c6ac871..4499b8b 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -166,7 +166,10 @@  struct BlockDriver {
                                 QEMUSnapshotInfo *sn_info);
     int (*bdrv_snapshot_goto)(BlockDriverState *bs,
                               const char *snapshot_id);
-    int (*bdrv_snapshot_delete)(BlockDriverState *bs, const char *snapshot_id);
+    int (*bdrv_snapshot_delete)(BlockDriverState *bs,
+                                const char *snapshot_id,
+                                const char *name,
+                                Error **errp);
     int (*bdrv_snapshot_list)(BlockDriverState *bs,
                               QEMUSnapshotInfo **psn_info);
     int (*bdrv_snapshot_load_tmp)(BlockDriverState *bs,
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 9d06dc1..e47e78d 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -51,7 +51,10 @@  int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info);
 int bdrv_snapshot_goto(BlockDriverState *bs,
                        const char *snapshot_id);
-int bdrv_snapshot_delete(BlockDriverState *bs, const char *snapshot_id);
+int bdrv_snapshot_delete(BlockDriverState *bs,
+                         const char *snapshot_id,
+                         const char *name,
+                         Error **errp);
 int bdrv_snapshot_list(BlockDriverState *bs,
                        QEMUSnapshotInfo **psn_info);
 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
diff --git a/include/qemu-common.h b/include/qemu-common.h
index f439738..06c777f 100644
--- a/include/qemu-common.h
+++ b/include/qemu-common.h
@@ -191,6 +191,9 @@  int64_t strtosz_suffix(const char *nptr, char **end, const char default_suffix);
 int64_t strtosz_suffix_unit(const char *nptr, char **end,
                             const char default_suffix, int64_t unit);
 
+/* used to print char* safely */
+#define STR_PRINT_CHAR(str) ((str) ? (str) : "null")
+
 /* path.c */
 void init_paths(const char *prefix);
 const char *path(const char *pathname);
diff --git a/qemu-img.c b/qemu-img.c
index f8c97d3..05564d3 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1883,7 +1883,10 @@  static int img_snapshot(int argc, char **argv)
         break;
 
     case SNAPSHOT_DELETE:
-        ret = bdrv_snapshot_delete(bs, snapshot_name);
+        ret = bdrv_snapshot_delete(bs, snapshot_name, NULL, NULL);
+        if (ret == -ENOENT || ret == -EINVAL) {
+            ret = bdrv_snapshot_delete(bs, NULL, snapshot_name, NULL);
+        }
         if (ret) {
             error_report("Could not delete snapshot '%s': %d (%s)",
                 snapshot_name, ret, strerror(-ret));
diff --git a/savevm.c b/savevm.c
index e0491e7..56afebb 100644
--- a/savevm.c
+++ b/savevm.c
@@ -2332,7 +2332,10 @@  static int del_existing_snapshots(Monitor *mon, const char *name)
         if (bdrv_can_snapshot(bs) &&
             bdrv_snapshot_find(bs, snapshot, name) >= 0)
         {
-            ret = bdrv_snapshot_delete(bs, name);
+            ret = bdrv_snapshot_delete(bs, name, NULL, NULL);
+            if (ret == -ENOENT || ret == -EINVAL) {
+                ret = bdrv_snapshot_delete(bs, NULL, name, NULL);
+            }
             if (ret < 0) {
                 monitor_printf(mon,
                                "Error while deleting snapshot on '%s'\n",
@@ -2562,7 +2565,10 @@  void do_delvm(Monitor *mon, const QDict *qdict)
     bs1 = NULL;
     while ((bs1 = bdrv_next(bs1))) {
         if (bdrv_can_snapshot(bs1)) {
-            ret = bdrv_snapshot_delete(bs1, name);
+            ret = bdrv_snapshot_delete(bs1, name, NULL, NULL);
+            if (ret == -ENOENT || ret == -EINVAL) {
+                ret = bdrv_snapshot_delete(bs, NULL, name, NULL);
+            }
             if (ret < 0) {
                 if (ret == -ENOTSUP)
                     monitor_printf(mon,