block: Decouple savevm from DriveInfo

We find snapshots by iterating over the list of drives defined with
drive_init().  This misses host block devices defined by other means.
Such means don't exist now, but will be introduced later in this
series.

Iterate over all host block devices instead, with bdrv_next().
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

savevm.c

@@ -1578,12 +1578,13 @@ out:
 static BlockDriverState *get_bs_snapshots(void)
 {
     BlockDriverState *bs;
-    DriveInfo *dinfo;
 
     if (bs_snapshots)
         return bs_snapshots;
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs = dinfo->bdrv;
+    /* FIXME what if bs_snapshots gets hot-unplugged? */
+
+    bs = NULL;
+    while ((bs = bdrv_next(bs))) {
         if (bdrv_can_snapshot(bs)) {
             goto ok;
         }
@@ -1622,12 +1623,11 @@ static int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
 static int del_existing_snapshots(Monitor *mon, const char *name)
 {
     BlockDriverState *bs;
-    DriveInfo *dinfo;
     QEMUSnapshotInfo sn1, *snapshot = &sn1;
     int ret;
 
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs = dinfo->bdrv;
+    bs = NULL;
+    while ((bs = bdrv_next(bs))) {
         if (bdrv_can_snapshot(bs) &&
             bdrv_snapshot_find(bs, snapshot, name) >= 0)
         {
@@ -1646,7 +1646,6 @@ static int del_existing_snapshots(Monitor *mon, const char *name)
 
 void do_savevm(Monitor *mon, const QDict *qdict)
 {
-    DriveInfo *dinfo;
     BlockDriverState *bs, *bs1;
     QEMUSnapshotInfo sn1, *sn = &sn1, old_sn1, *old_sn = &old_sn1;
     int ret;
@@ -1661,8 +1660,8 @@ void do_savevm(Monitor *mon, const QDict *qdict)
     const char *name = qdict_get_try_str(qdict, "name");
 
     /* Verify if there is a device that doesn't support snapshots and is writable */
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs = dinfo->bdrv;
+    bs = NULL;
+    while ((bs = bdrv_next(bs))) {
 
         if (bdrv_is_removable(bs) || bdrv_is_read_only(bs)) {
             continue;
@@ -1730,8 +1729,8 @@ void do_savevm(Monitor *mon, const QDict *qdict)
 
     /* create the snapshots */
 
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs1 = dinfo->bdrv;
+    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);
@@ -1750,15 +1749,14 @@ void do_savevm(Monitor *mon, const QDict *qdict)
 
 int load_vmstate(const char *name)
 {
-    DriveInfo *dinfo;
     BlockDriverState *bs, *bs1;
     QEMUSnapshotInfo sn;
     QEMUFile *f;
     int ret;
 
     /* Verify if there is a device that doesn't support snapshots and is writable */
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs = dinfo->bdrv;
+    bs = NULL;
+    while ((bs = bdrv_next(bs))) {
 
         if (bdrv_is_removable(bs) || bdrv_is_read_only(bs)) {
             continue;
@@ -1780,8 +1778,8 @@ int load_vmstate(const char *name)
     /* Flush all IO requests so they don't interfere with the new state.  */
     qemu_aio_flush();
 
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs1 = dinfo->bdrv;
+    bs1 = NULL;
+    while ((bs1 = bdrv_next(bs1))) {
         if (bdrv_can_snapshot(bs1)) {
             ret = bdrv_snapshot_goto(bs1, name);
             if (ret < 0) {
@@ -1831,7 +1829,6 @@ int load_vmstate(const char *name)
 
 void do_delvm(Monitor *mon, const QDict *qdict)
 {
-    DriveInfo *dinfo;
     BlockDriverState *bs, *bs1;
     int ret;
     const char *name = qdict_get_str(qdict, "name");
@@ -1842,8 +1839,8 @@ void do_delvm(Monitor *mon, const QDict *qdict)
         return;
     }
 
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs1 = dinfo->bdrv;
+    bs1 = NULL;
+    while ((bs1 = bdrv_next(bs1))) {
         if (bdrv_can_snapshot(bs1)) {
             ret = bdrv_snapshot_delete(bs1, name);
             if (ret < 0) {
@@ -1861,7 +1858,6 @@ void do_delvm(Monitor *mon, const QDict *qdict)
 
 void do_info_snapshots(Monitor *mon)
 {
-    DriveInfo *dinfo;
     BlockDriverState *bs, *bs1;
     QEMUSnapshotInfo *sn_tab, *sn;
     int nb_sns, i;
@@ -1873,8 +1869,8 @@ void do_info_snapshots(Monitor *mon)
         return;
     }
     monitor_printf(mon, "Snapshot devices:");
-    QTAILQ_FOREACH(dinfo, &drives, next) {
-        bs1 = dinfo->bdrv;
+    bs1 = NULL;
+    while ((bs1 = bdrv_next(bs1))) {
         if (bdrv_can_snapshot(bs1)) {
             if (bs == bs1)
                 monitor_printf(mon, " %s", bdrv_get_device_name(bs1));