[Qemu-devel] [PATCH V6 05/14] block: add snapshot info query function bdrv_query_snapshot_infolist()

[Wenchao Xia]

  This patch add function bdrv_query_snapshot_infolist(), which will
return snapshot info of an image in qmp object format. The implementation
code are based on the code moved from qemu-img.c with modification to fit more
for qmp based block layer API.
  To help filter out snapshot info not needed, a call back function is
added in bdrv_query_snapshot_infolist().
  bdrv_can_read_snapshot() should be called before call this function,
to avoid got *errp set unexpectedly.

Signed-off-by: Wenchao Xia <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
 block.c               |   60 ++++++++++++++++++++++++++++++++++++++----------
 include/block/block.h |    8 +++++-
 qemu-img.c            |    8 +++++-
 3 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/block.c b/block.c
index 368b37c..8d0145a 100644
--- a/block.c
+++ b/block.c
@@ -2813,29 +2813,62 @@ int coroutine_fn 
bdrv_co_is_allocated_above(BlockDriverState *top,
     return 0;
 }
 
-void collect_snapshots(BlockDriverState *bs , ImageInfo *info)
+SnapshotInfoList *bdrv_query_snapshot_infolist(BlockDriverState *bs,
+                                               SnapshotFilterFunc filter,
+                                               void *opaque,
+                                               Error **errp)
 {
     int i, sn_count;
     QEMUSnapshotInfo *sn_tab = NULL;
-    SnapshotInfoList *info_list, *cur_item = NULL;
+    SnapshotInfoList *info_list, *cur_item = NULL, *head = NULL;
+    SnapshotInfo *info;
+
     sn_count = bdrv_snapshot_list(bs, &sn_tab);
+    if (sn_count < 0) {
+        /* Now bdrv_snapshot_list() use negative value to tip error, so a check
+         * of it was done here. In future errp can be set by that function
+         * itself, by changing the call back functions in c files in ./block.
+         */
+        const char *dev = bdrv_get_device_name(bs);
+        switch (sn_count) {
+        case -ENOMEDIUM:
+            error_setg(errp, "Device '%s' is not inserted.", dev);
+            break;
+        case -ENOTSUP:
+            error_setg(errp,
+                       "Device '%s' does not support internal snapshot.",
+                       dev);
+            break;
+        default:
+            error_setg(errp,
+                       "Device '%s' got '%d' for bdrv_snapshot_list(), "
+                       "message '%s'.",
+                       dev, sn_count, strerror(-sn_count));
+            break;
+        }
+        return NULL;
+    }
 
     for (i = 0; i < sn_count; i++) {
-        info->has_snapshots = true;
-        info_list = g_new0(SnapshotInfoList, 1);
+        if (filter && filter(&sn_tab[i], opaque) != 0) {
+            continue;
+        }
 
-        info_list->value                = g_new0(SnapshotInfo, 1);
-        info_list->value->id            = g_strdup(sn_tab[i].id_str);
-        info_list->value->name          = g_strdup(sn_tab[i].name);
-        info_list->value->vm_state_size = sn_tab[i].vm_state_size;
-        info_list->value->date_sec      = sn_tab[i].date_sec;
-        info_list->value->date_nsec     = sn_tab[i].date_nsec;
-        info_list->value->vm_clock_sec  = sn_tab[i].vm_clock_nsec / 1000000000;
-        info_list->value->vm_clock_nsec = sn_tab[i].vm_clock_nsec % 1000000000;
+        info = g_new0(SnapshotInfo, 1);
+        info->id            = g_strdup(sn_tab[i].id_str);
+        info->name          = g_strdup(sn_tab[i].name);
+        info->vm_state_size = sn_tab[i].vm_state_size;
+        info->date_sec      = sn_tab[i].date_sec;
+        info->date_nsec     = sn_tab[i].date_nsec;
+        info->vm_clock_sec  = sn_tab[i].vm_clock_nsec / 1000000000;
+        info->vm_clock_nsec = sn_tab[i].vm_clock_nsec % 1000000000;
+
+        info_list = g_new0(SnapshotInfoList, 1);
+        info_list->value = info;
 
         /* XXX: waiting for the qapi to support qemu-queue.h types */
         if (!cur_item) {
-            info->snapshots = cur_item = info_list;
+            head = cur_item = info_list;
         } else {
             cur_item->next = info_list;
             cur_item = info_list;
@@ -2844,6 +2877,7 @@ void collect_snapshots(BlockDriverState *bs , ImageInfo 
*info)
     }
 
     g_free(sn_tab);
+    return head;
 }
 
 void collect_image_info(BlockDriverState *bs,
diff --git a/include/block/block.h b/include/block/block.h
index e6d915c..51a14f2 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -319,6 +319,13 @@ void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
 void bdrv_get_full_backing_filename(BlockDriverState *bs,
                                     char *dest, size_t sz);
+
+typedef int (*SnapshotFilterFunc)(const QEMUSnapshotInfo *sn, void *opaque);
+/* assume bs is already opened, use qapi_free_* to free returned value. */
+SnapshotInfoList *bdrv_query_snapshot_infolist(BlockDriverState *bs,
+                                               SnapshotFilterFunc filter,
+                                               void *opaque,
+                                               Error **errp);
 BlockInfo *bdrv_query_info(BlockDriverState *s);
 BlockStats *bdrv_query_stats(const BlockDriverState *bs);
 bool bdrv_can_read_snapshot(BlockDriverState *bs);
@@ -450,7 +457,6 @@ int bdrv_debug_breakpoint(BlockDriverState *bs, const char 
*event,
 int bdrv_debug_resume(BlockDriverState *bs, const char *tag);
 bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag);
 
-void collect_snapshots(BlockDriverState *bs , ImageInfo *info);
 void collect_image_info(BlockDriverState *bs,
                         ImageInfo *info,
                         const char *filename);
diff --git a/qemu-img.c b/qemu-img.c
index b650d17..1034cc5 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1280,7 +1280,13 @@ static ImageInfoList *collect_image_info_list(const char 
*filename,
 
         info = g_new0(ImageInfo, 1);
         collect_image_info(bs, info, filename);
-        collect_snapshots(bs, info);
+        if (bdrv_can_read_snapshot(bs)) {
+            info->snapshots = bdrv_query_snapshot_infolist(bs, NULL,
+                                                           NULL, NULL);
+            if (info->snapshots) {
+                info->has_snapshots = true;
+            }
+        }
 
         elem = g_new0(ImageInfoList, 1);
         elem->value = info;
-- 
1.7.1