Make state snapshots compatible with SD cards.

This patch introduces a check such that only drives exporting a
snapshot creation function are considered for storing snapshots.
SD cards are mounted with a raw file system, which does not
support snapshots. Since the SD card is now skipped, the actual
snapshot image can be safely mounted on hdb rather than hda.

The contents of the SD card itself are included in the snapshot
however, since they are accessed with the NAND driver (which
saves the contents of the underlying files).

Change-Id: I4816b6e54e227aca356389c15ce9f5c1282d2464

3 files changed, 16 insertions, 22 deletions

diff --git a/block.c b/block.c
index 6d05a58..852cb3e 100644
--- a/block.c
+++ b/block.c
@@ -1181,6 +1181,15 @@ int bdrv_get_buffer(BlockDriverState *bs, uint8_t *buf, int64_t pos, int size)
 /**************************************************************/
 /* handling of snapshots */
 
+int bdrv_can_snapshot(BlockDriverState *bs)
+{
+    return ( bs &&
+             !bdrv_is_removable(bs) &&
+             !bdrv_is_read_only(bs) &&
+             bs->drv &&
+             bs->drv->bdrv_snapshot_create );
+}
+
 int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info)
 {
diff --git a/block.h b/block.h
index 71e87fc..b392021 100644
--- a/block.h
+++ b/block.h
@@ -145,6 +145,7 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
 void bdrv_get_backing_filename(BlockDriverState *bs,
                                char *filename, int filename_size);
+int bdrv_can_snapshot(BlockDriverState *bs);
 int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info);
 int bdrv_snapshot_goto(BlockDriverState *bs,
diff --git a/savevm.c b/savevm.c
index 8f0d8f1..ee90805 100644
--- a/savevm.c
+++ b/savevm.c
@@ -907,8 +907,8 @@ int qemu_savevm_state_complete(QEMUFile *f)
     for(se = first_se; se != NULL; se = se->next) {
         int len;
 
-	if (se->save_state == NULL)
-	    continue;
+        if (se->save_state == NULL)
+            continue;
 
         /* Section type */
         qemu_put_byte(f, QEMU_VM_SECTION_FULL);
@@ -1122,22 +1122,6 @@ out:
     return ret;
 }
 
-/* device can contain snapshots */
-static int bdrv_can_snapshot(BlockDriverState *bs)
-{
-    return (bs &&
-            !bdrv_is_removable(bs) &&
-            !bdrv_is_read_only(bs));
-}
-
-/* device must be snapshots in order to have a reliable snapshot */
-static int bdrv_has_snapshot(BlockDriverState *bs)
-{
-    return (bs &&
-            !bdrv_is_removable(bs) &&
-            !bdrv_is_read_only(bs));
-}
-
 static BlockDriverState *get_bs_snapshots(void)
 {
     BlockDriverState *bs;
@@ -1257,7 +1241,7 @@ void do_savevm(Monitor *mon, const char *name)
 
     for(i = 0; i < nb_drives; i++) {
         bs1 = drives_table[i].bdrv;
-        if (bdrv_has_snapshot(bs1)) {
+        if (bdrv_can_snapshot(bs1)) {
             if (must_delete) {
                 ret = bdrv_snapshot_delete(bs1, old_sn->id_str);
                 if (ret < 0) {
@@ -1304,7 +1288,7 @@ void do_loadvm(Monitor *mon, const char *name)
 
     for(i = 0; i <= nb_drives; i++) {
         bs1 = drives_table[i].bdrv;
-        if (bdrv_has_snapshot(bs1)) {
+        if (bdrv_can_snapshot(bs1)) {
             ret = bdrv_snapshot_goto(bs1, name);
             if (ret < 0) {
                 if (bs != bs1)
@@ -1372,7 +1356,7 @@ void do_delvm(Monitor *mon, const char *name)
 
     for(i = 0; i <= nb_drives; i++) {
         bs1 = drives_table[i].bdrv;
-        if (bdrv_has_snapshot(bs1)) {
+        if (bdrv_can_snapshot(bs1)) {
             ret = bdrv_snapshot_delete(bs1, name);
             if (ret < 0) {
                 if (ret == -ENOTSUP)
@@ -1402,7 +1386,7 @@ void do_info_snapshots(Monitor *mon)
     monitor_printf(mon, "Snapshot devices:");
     for(i = 0; i <= nb_drives; i++) {
         bs1 = drives_table[i].bdrv;
-        if (bdrv_has_snapshot(bs1)) {
+        if (bdrv_can_snapshot(bs1)) {
             if (bs == bs1)
                 monitor_printf(mon, " %s", bdrv_get_device_name(bs1));
         }