hmp: show all of snapshot info on every block dev in output of 'info snapshots'

Currently, the output of 'info snapshots' shows fully available snapshots.
It's opaque, hides some snapshot information to users. It's not convenient
if users want to know more about all of snapshot information on every block
device via monitor.

Follow Kevin's and Max's proposals, The patch makes the output more detailed:
(qemu) info snapshots
List of snapshots present on all disks:
 ID        TAG                 VM SIZE                DATE       VM CLOCK
 --        checkpoint-1           165M 2016-05-22 16:58:07   00:02:06.813

List of partial (non-loadable) snapshots on 'drive_image1':
 ID        TAG                 VM SIZE                DATE       VM CLOCK
 1         snap1                     0 2016-05-22 16:57:31   00:01:30.567
Signed-off-by: NLin Ma <lma@suse.com>
Message-id: 1467869164-26688-3-git-send-email-lma@suse.com
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NMax Reitz <mreitz@redhat.com>

migration/savevm.c

@@ -2200,12 +2200,31 @@ void hmp_delvm(Monitor *mon, const QDict *qdict)
 void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
 {
     BlockDriverState *bs, *bs1;
+    BdrvNextIterator it1;
     QEMUSnapshotInfo *sn_tab, *sn;
+    bool no_snapshot = true;
     int nb_sns, i;
     int total;
-    int *available_snapshots;
+    int *global_snapshots;
     AioContext *aio_context;
 
+    typedef struct SnapshotEntry {
+        QEMUSnapshotInfo sn;
+        QTAILQ_ENTRY(SnapshotEntry) next;
+    } SnapshotEntry;
+
+    typedef struct ImageEntry {
+        const char *imagename;
+        QTAILQ_ENTRY(ImageEntry) next;
+        QTAILQ_HEAD(, SnapshotEntry) snapshots;
+    } ImageEntry;
+
+    QTAILQ_HEAD(, ImageEntry) image_list =
+        QTAILQ_HEAD_INITIALIZER(image_list);
+
+    ImageEntry *image_entry, *next_ie;
+    SnapshotEntry *snapshot_entry;
+
     bs = bdrv_all_find_vmstate_bs();
     if (!bs) {
         monitor_printf(mon, "No available block device supports snapshots\n");
@@ -2222,25 +2241,65 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    if (nb_sns == 0) {
+    for (bs1 = bdrv_first(&it1); bs1; bs1 = bdrv_next(&it1)) {
+        int bs1_nb_sns = 0;
+        ImageEntry *ie;
+        SnapshotEntry *se;
+        AioContext *ctx = bdrv_get_aio_context(bs1);
+
+        aio_context_acquire(ctx);
+        if (bdrv_can_snapshot(bs1)) {
+            sn = NULL;
+            bs1_nb_sns = bdrv_snapshot_list(bs1, &sn);
+            if (bs1_nb_sns > 0) {
+                no_snapshot = false;
+                ie = g_new0(ImageEntry, 1);
+                ie->imagename = bdrv_get_device_name(bs1);
+                QTAILQ_INIT(&ie->snapshots);
+                QTAILQ_INSERT_TAIL(&image_list, ie, next);
+                for (i = 0; i < bs1_nb_sns; i++) {
+                    se = g_new0(SnapshotEntry, 1);
+                    se->sn = sn[i];
+                    QTAILQ_INSERT_TAIL(&ie->snapshots, se, next);
+                }
+            }
+            g_free(sn);
+        }
+        aio_context_release(ctx);
+    }
+
+    if (no_snapshot) {
         monitor_printf(mon, "There is no snapshot available.\n");
         return;
     }
 
-    available_snapshots = g_new0(int, nb_sns);
+    global_snapshots = g_new0(int, nb_sns);
     total = 0;
     for (i = 0; i < nb_sns; i++) {
+        SnapshotEntry *next_sn;
         if (bdrv_all_find_snapshot(sn_tab[i].name, &bs1) == 0) {
-            available_snapshots[total] = i;
+            global_snapshots[total] = i;
             total++;
+            QTAILQ_FOREACH(image_entry, &image_list, next) {
+                QTAILQ_FOREACH_SAFE(snapshot_entry, &image_entry->snapshots,
+                                    next, next_sn) {
+                    if (!strcmp(sn_tab[i].name, snapshot_entry->sn.name)) {
+                        QTAILQ_REMOVE(&image_entry->snapshots, snapshot_entry,
+                                      next);
+                        g_free(snapshot_entry);
+                    }
+                }
+            }
         }
     }
 
+    monitor_printf(mon, "List of snapshots present on all disks:\n");
+
     if (total > 0) {
         bdrv_snapshot_dump((fprintf_function)monitor_printf, mon, NULL);
         monitor_printf(mon, "\n");
         for (i = 0; i < total; i++) {
-            sn = &sn_tab[available_snapshots[i]];
+            sn = &sn_tab[global_snapshots[i]];
             /* The ID is not guaranteed to be the same on all images, so
              * overwrite it.
              */
@@ -2249,11 +2308,35 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
             monitor_printf(mon, "\n");
         }
     } else {
-        monitor_printf(mon, "There is no suitable snapshot available\n");
+        monitor_printf(mon, "None\n");
     }
 
+    QTAILQ_FOREACH(image_entry, &image_list, next) {
+        if (QTAILQ_EMPTY(&image_entry->snapshots)) {
+            continue;
+        }
+        monitor_printf(mon,
+                       "\nList of partial (non-loadable) snapshots on '%s':\n",
+                       image_entry->imagename);
+        bdrv_snapshot_dump((fprintf_function)monitor_printf, mon, NULL);
+        monitor_printf(mon, "\n");
+        QTAILQ_FOREACH(snapshot_entry, &image_entry->snapshots, next) {
+            bdrv_snapshot_dump((fprintf_function)monitor_printf, mon,
+                               &snapshot_entry->sn);
+            monitor_printf(mon, "\n");
+        }
+    }
+
+    QTAILQ_FOREACH_SAFE(image_entry, &image_list, next, next_ie) {
+        SnapshotEntry *next_sn;
+        QTAILQ_FOREACH_SAFE(snapshot_entry, &image_entry->snapshots, next,
+                            next_sn) {
+            g_free(snapshot_entry);
+        }
+        g_free(image_entry);
+    }
     g_free(sn_tab);
-    g_free(available_snapshots);
+    g_free(global_snapshots);
 
 }