[Qemu-devel] [PATCH 09/10] migration: implement bdrv_all_find_vmstate_bs helper

["Denis V. Lunev" <den@openvz.org>]

The patch also ensures proper locking for the operation.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Juan Quintela <quintela@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
---
 block/snapshot.c         | 15 +++++++++++++++
 include/block/snapshot.h |  2 ++
 migration/savevm.c       | 19 ++++---------------
 3 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/block/snapshot.c b/block/snapshot.c
index 4daf9d4..337ac8e 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -465,3 +465,18 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn, BlockDriverState **bad)
     *bad = bs;
     return err;
 }
+
+BlockDriverState *bdrv_all_find_vmstate_bs(void)
+{
+    bool not_found = true;
+    BlockDriverState *bs = NULL;
+
+    while (not_found && (bs = bdrv_next(bs))) {
+        AioContext *ctx = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(ctx);
+        not_found = !bdrv_can_snapshot(bs);
+        aio_context_release(ctx);
+    }
+    return bs;
+}
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index df443b2..543cbb3 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -88,4 +88,6 @@ int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bsd_bs);
 int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs);
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn, BlockDriverState **bad);
 
+BlockDriverState *bdrv_all_find_vmstate_bs(void);
+
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index b4a3930..6be30cb 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1237,17 +1237,6 @@ out:
     return ret;
 }
 
-static BlockDriverState *find_vmstate_bs(void)
-{
-    BlockDriverState *bs = NULL;
-    while ((bs = bdrv_next(bs))) {
-        if (bdrv_can_snapshot(bs)) {
-            return bs;
-        }
-    }
-    return NULL;
-}
-
 void hmp_savevm(Monitor *mon, const QDict *qdict)
 {
     BlockDriverState *bs, *bs1;
@@ -1275,8 +1264,8 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    bs = find_vmstate_bs();
-    if (!bs) {
+    bs = bdrv_all_find_vmstate_bs();
+    if (bs == NULL) {
         monitor_printf(mon, "No block device can accept snapshots\n");
         return;
     }
@@ -1385,7 +1374,7 @@ int load_vmstate(const char *name)
         return ret;
     }
 
-    bs_vm_state = find_vmstate_bs();
+    bs_vm_state = bdrv_all_find_vmstate_bs();
     if (!bs_vm_state) {
         error_report("No block device supports snapshots");
         return -ENOTSUP;
@@ -1454,7 +1443,7 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     int total;
     int *available_snapshots;
 
-    bs = find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs();
     if (!bs) {
         monitor_printf(mon, "No available block device supports snapshots\n");
         return;
-- 
2.5.0