[Qemu-devel] [PATCH 10/11] snapshot: create bdrv_all_create_snapshot helper

[Denis V. Lunev]

to create snapshot for all loaded block drivers.

The patch also ensures proper locking.

Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Juan Quintela <quint...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
CC: Kevin Wolf <kw...@redhat.com>
---
 block/snapshot.c         | 24 ++++++++++++++++++++++++
 include/block/snapshot.h |  1 +
 migration/savevm.c       | 22 ++++++----------------
 3 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/block/snapshot.c b/block/snapshot.c
index e196c9b..15d2b8a 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -456,6 +456,8 @@ BlockDriverState *bdrv_all_find_vmstate_bs(void)
 
         aio_context_acquire(ctx);
         if (bdrv_can_snapshot(bs)) {
+            /* Do not change logic here without tweaking
+             * bdrv_all_create_snapshot below */
             return bs;
         }
         aio_context_release(ctx);
@@ -467,3 +469,25 @@ void bdrv_unlock(BlockDriverState *bs)
 {
     aio_context_release(bdrv_get_aio_context(bs));
 }
+
+int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn, BlockDriverState **bad)
+{
+    int err = 0;
+    BlockDriverState *bs = NULL;
+
+    while ((bs = bdrv_next(bs)) && err == 0) {
+        AioContext *ctx = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(ctx);
+        if (bdrv_can_snapshot(bs)) {
+            err = bdrv_snapshot_create(bs, sn);
+            /* Tricky part here. First image contains VM state. The behavior
+             * is matched one in bdrv_all_find_vmstate_bs */
+            sn->vm_state_size = 0;
+        }
+        aio_context_release(ctx);
+    }
+
+    *bad = bs;
+    return err;
+}
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 1f45f51..0a29b2d 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -90,5 +90,6 @@ int bdrv_all_find_snapshot(const char *name, BlockDriverState 
**first_bad_bs);
 
 BlockDriverState *bdrv_all_find_vmstate_bs(void);
 void bdrv_unlock(BlockDriverState *bs);
+int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn, BlockDriverState **bad);
 
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index f8c727d..8db7895 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1251,12 +1251,11 @@ out:
 
 void hmp_savevm(Monitor *mon, const QDict *qdict)
 {
-    BlockDriverState *bs, *bs1;
+    BlockDriverState *bs;
     QEMUSnapshotInfo sn1, *sn = &sn1, old_sn1, *old_sn = &old_sn1;
     int ret;
     QEMUFile *f;
     int saved_vm_running;
-    uint64_t vm_state_size;
     qemu_timeval tv;
     struct tm tm;
     const char *name = qdict_get_try_str(qdict, "name");
@@ -1322,7 +1321,7 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
         goto the_end;
     }
     ret = qemu_savevm_state(f, &local_err);
-    vm_state_size = qemu_ftell(f);
+    sn->vm_state_size = qemu_ftell(f);
     qemu_fclose(f);
     if (ret < 0) {
         monitor_printf(mon, "%s\n", error_get_pretty(local_err));
@@ -1330,19 +1329,10 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
         goto the_end;
     }
 
-    /* create the snapshots */
-
-    bs1 = NULL;
-    while ((bs1 = bdrv_next(bs1))) {
-        if (bdrv_can_snapshot(bs1)) {
-            /* Write VM state size only to the image that contains the state */
-            sn->vm_state_size = (bs == bs1 ? vm_state_size : 0);
-            ret = bdrv_snapshot_create(bs1, sn);
-            if (ret < 0) {
-                monitor_printf(mon, "Error while creating snapshot on '%s'\n",
-                               bdrv_get_device_name(bs1));
-            }
-        }
+    ret = bdrv_all_create_snapshot(sn, &bs);
+    if (ret < 0) {
+        monitor_printf(mon, "Error while creating snapshot on '%s'\n",
+                       bdrv_get_device_name(bs));
     }
 
  the_end:
-- 
2.5.0