block: allow specifying name of block device for vmstate storage

Currently the vmstate will be stored in the first block device that
supports snapshots. Historically this would have usually been the
root device, but with UEFI it might be the variable store. There
needs to be a way to override the choice of block device to store
the state in.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20210204124834.774401-6-berrange@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

diff --git a/block/monitor/block-hmp-cmds.c b/block/monitor/block-hmp-cmds.c
index e15121be1fce104a0afe3abeeb03447192844af2..9cc5d4b51e3f25f57c6f8b65f34695b83d873886 100644 (file)
--- a/block/monitor/block-hmp-cmds.c
+++ b/block/monitor/block-hmp-cmds.c
@@ -902,7 +902,7 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     SnapshotEntry *snapshot_entry;
     Error *err = NULL;
 
-    bs = bdrv_all_find_vmstate_bs(false, NULL, &err);
+    bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, &err);
     if (!bs) {
         error_report_err(err);
         return;

diff --git a/block/snapshot.c b/block/snapshot.c
index 220173deaee09adab895392d96998d5306b79e83..0b129bee8fe5025f96e79046953a02a4fce19d36 100644 (file)
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -678,7 +678,9 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
     return 0;
 }
 
-BlockDriverState *bdrv_all_find_vmstate_bs(bool has_devices, strList *devices,
+
+BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
+                                           bool has_devices, strList *devices,
                                            Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
@@ -699,13 +701,31 @@ BlockDriverState *bdrv_all_find_vmstate_bs(bool has_devices, strList *devices,
             bdrv_can_snapshot(bs);
         aio_context_release(ctx);
 
-        if (found) {
+        if (vmstate_bs) {
+            if (g_str_equal(vmstate_bs,
+                            bdrv_get_node_name(bs))) {
+                if (found) {
+                    return bs;
+                } else {
+                    error_setg(errp,
+                               "vmstate block device '%s' does not support snapshots",
+                               vmstate_bs);
+                    return NULL;
+                }
+            }
+        } else if (found) {
             return bs;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
-    error_setg(errp, "No block device supports snapshots");
+    if (vmstate_bs) {
+        error_setg(errp,
+                   "vmstate block device '%s' does not exist", vmstate_bs);
+    } else {
+        error_setg(errp,
+                   "no block device can store vmstate for snapshot");
+    }
     return NULL;
 }

diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index 2569a903f2504f2737f494aa7f5946c67e9c7670..8a6a37240d0e7fd9ee94cc1cc50a296cd19f6cbe 100644 (file)
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -95,7 +95,8 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              strList *devices,
                              Error **errp);
 
-BlockDriverState *bdrv_all_find_vmstate_bs(bool has_devices, strList *devices,
+BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
+                                           bool has_devices, strList *devices,
                                            Error **errp);
 
 #endif

diff --git a/migration/savevm.c b/migration/savevm.c
index 0dbe8c16075a764f3443091ebdc3e88c00e1a12b..cdd201e7f889d255fec77d544d17fb9b26483ba9 100644 (file)
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2797,7 +2797,7 @@ bool save_snapshot(const char *name, Error **errp)
         }
     }
 
-    bs = bdrv_all_find_vmstate_bs(false, NULL, errp);
+    bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, errp);
     if (bs == NULL) {
         return false;
     }
@@ -2982,7 +2982,7 @@ bool load_snapshot(const char *name, Error **errp)
         return false;
     }
 
-    bs_vm_state = bdrv_all_find_vmstate_bs(false, NULL, errp);
+    bs_vm_state = bdrv_all_find_vmstate_bs(NULL, false, NULL, errp);
     if (!bs_vm_state) {
         return false;
     }

diff --git a/replay/replay-debugging.c b/replay/replay-debugging.c
index 67d8237077d018444937348e83f7e2d4ed3a4943..ca37cf4025394ec4026dbd87a87017a0e073502e 100644 (file)
--- a/replay/replay-debugging.c
+++ b/replay/replay-debugging.c
@@ -148,7 +148,7 @@ static char *replay_find_nearest_snapshot(int64_t icount,
 
     *snapshot_icount = -1;
 
-    bs = bdrv_all_find_vmstate_bs(false, NULL, NULL);
+    bs = bdrv_all_find_vmstate_bs(NULL, false, NULL, NULL);
     if (!bs) {
         goto fail;
     }

diff --git a/tests/qemu-iotests/267.out b/tests/qemu-iotests/267.out
index 6149029b25d9257c59dc822e86d7fa1af4ba6180..7176e376e1f98fd8de91cf526ef2171aadcc1e3a 100644 (file)
--- a/tests/qemu-iotests/267.out
+++ b/tests/qemu-iotests/267.out
@@ -6,11 +6,11 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
 Testing:
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
-Error: No block device supports snapshots
+Error: no block device can store vmstate for snapshot
 (qemu) info snapshots
-No block device supports snapshots
+no block device can store vmstate for snapshot
 (qemu) loadvm snap0
-Error: No block device supports snapshots
+Error: no block device can store vmstate for snapshot
 (qemu) quit
 
 
@@ -22,7 +22,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'none0' is writable but does not support snapshots
 (qemu) info snapshots
-No block device supports snapshots
+no block device can store vmstate for snapshot
 (qemu) loadvm snap0
 Error: Device 'none0' is writable but does not support snapshots
 (qemu) quit
@@ -58,7 +58,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'virtio0' is writable but does not support snapshots
 (qemu) info snapshots
-No block device supports snapshots
+no block device can store vmstate for snapshot
 (qemu) loadvm snap0
 Error: Device 'virtio0' is writable but does not support snapshots
 (qemu) quit
@@ -83,7 +83,7 @@ QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
 Error: Device 'file' is writable but does not support snapshots
 (qemu) info snapshots
-No block device supports snapshots
+no block device can store vmstate for snapshot
 (qemu) loadvm snap0
 Error: Device 'file' is writable but does not support snapshots
 (qemu) quit