[Qemu-devel] [] [PATCH] Show all of snapshot info on every block device in output of 'info snapshots'

[Lin Ma <lma@suse.com>]

Currently, the output of 'info snapshots' shows fully available snapshots.

In my opinion there are 2 disadvantages:
1. 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.
2. It uses snapshot id to determine whether a snapshot is 'fully available',
It causes incorrect output in some scenario.

For instance:
(qemu) info block
drive_image1 (#block113): /opt/vms/SLES12-SP1-JeOS-x86_64-GM/disk0.qcow2
(qcow2)
    Cache mode:       writeback

drive_image2 (#block349): /opt/vms/SLES12-SP1-JeOS-x86_64-GM/disk1.qcow2
(qcow2)
    Cache mode:       writeback
(qemu)
(qemu) info snapshots
There is no snapshot available.
(qemu)
(qemu) snapshot_blkdev_internal drive_image1 snap1
(qemu)
(qemu) info snapshots
There is no suitable snapshot available
(qemu)
(qemu) savevm checkpoint-1
(qemu)
(qemu) info snapshots
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         snap1                     0 2016-05-22 16:57:31   00:01:30.567
(qemu)

$ qemu-img snapshot -l disk0.qcow2
Snapshot list:
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         snap1                     0 2016-05-22 16:57:31   00:01:30.567
2         checkpoint-1           165M 2016-05-22 16:58:07   00:02:06.813

$ qemu-img snapshot -l disk1.qcow2
Snapshot list:
ID        TAG                 VM SIZE                DATE       VM CLOCK
1         checkpoint-1              0 2016-05-22 16:58:07   00:02:06.813

The patch uses snapshot name instead of snapshot id to determine whether a
snapshot is 'fully available', and follow Kevin's suggestion, Make the output
more detailed/accurate:
(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: Lin Ma <lma@suse.com>
---
 migration/savevm.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 74 insertions(+), 3 deletions(-)

diff --git a/migration/savevm.c b/migration/savevm.c
index 6c21231..8444c62 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2153,12 +2153,28 @@ 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;
-    int nb_sns, i;
+    bool no_snapshot = true;
+    int nb_sns, nb_sns_tmp, i;
     int total;
     int *available_snapshots;
     AioContext *aio_context;
 
+    typedef struct SnapshotEntry {
+        QEMUSnapshotInfo *sn;
+        QTAILQ_ENTRY(SnapshotEntry) next;
+    } SnapshotEntry;
+
+    typedef struct ImageEntry {
+        char *imagename;
+        QTAILQ_ENTRY(ImageEntry) next;
+        QTAILQ_HEAD(, SnapshotEntry) snapshots;
+    } ImageEntry;
+
+    ImageEntry *image_entry;
+    SnapshotEntry *snapshot_entry;
+
     bs = bdrv_all_find_vmstate_bs();
     if (!bs) {
         monitor_printf(mon, "No available block device supports snapshots\n");
@@ -2175,7 +2191,34 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    if (nb_sns == 0) {
+    QTAILQ_HEAD(image_list, ImageEntry) image_list =
+        QTAILQ_HEAD_INITIALIZER(image_list);
+
+    for (bs1 = bdrv_first(&it1); bs1; bs1 = bdrv_next(&it1)) {
+        AioContext *ctx = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(ctx);
+        nb_sns_tmp = 0;
+        if (bdrv_can_snapshot(bs1)) {
+            nb_sns_tmp = bdrv_snapshot_list(bs1, &sn);
+            if (nb_sns_tmp > 0) {
+                no_snapshot = false;
+                ImageEntry *ie = g_malloc0(sizeof(*ie));
+                ie->imagename = g_strdup(bdrv_get_device_name(bs1));
+                QTAILQ_INIT(&ie->snapshots);
+                QTAILQ_INSERT_TAIL(&image_list, ie, next);
+                int x;
+                for (x = 0; x < nb_sns_tmp; x++) {
+                    SnapshotEntry *se = g_malloc0(sizeof(*se));
+                    se->sn = &sn[x];
+                    QTAILQ_INSERT_TAIL(&ie->snapshots, se, next);
+                }
+            }
+        }
+        aio_context_release(ctx);
+    }
+
+    if (no_snapshot) {
         monitor_printf(mon, "There is no snapshot available.\n");
         return;
     }
@@ -2183,17 +2226,28 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     available_snapshots = g_new0(int, nb_sns);
     total = 0;
     for (i = 0; i < nb_sns; i++) {
-        if (bdrv_all_find_snapshot(sn_tab[i].id_str, &bs1) == 0) {
+        if (bdrv_all_find_snapshot(sn_tab[i].name, &bs1) == 0) {
             available_snapshots[total] = i;
             total++;
         }
     }
 
+    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]];
+            QTAILQ_FOREACH(image_entry, &image_list, next) {
+                QTAILQ_FOREACH(snapshot_entry, &image_entry->snapshots, next) {
+                    if (!strcmp(sn->name, snapshot_entry->sn->name)) {
+                        QTAILQ_REMOVE(&image_entry->snapshots, snapshot_entry,
+                                      next);
+                    }
+                }
+            }
+            pstrcpy(sn->id_str, sizeof(sn->id_str), "--");
             bdrv_snapshot_dump((fprintf_function)monitor_printf, mon, sn);
             monitor_printf(mon, "\n");
         }
@@ -2201,6 +2255,23 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
         monitor_printf(mon, "There is no suitable snapshot available\n");
     }
 
+    monitor_printf(mon, "\n");
+    QTAILQ_FOREACH(image_entry, &image_list, next) {
+        if (QTAILQ_EMPTY(&image_entry->snapshots)) {
+            continue;
+        }
+        monitor_printf(mon, "List of partial (non-loadable) snapshots on '%s':",
+                       image_entry->imagename);
+        monitor_printf(mon, "\n");
+        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");
+        }
+    }
+
     g_free(sn_tab);
     g_free(available_snapshots);
 
-- 
2.8.1