[Qemu-devel] [PATCH 7/8] migration, qmp: add optional argument to specify BDS to save VM state to

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

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Juan Quintela <quintela@redhat.com>
CC: Amit Shah <amit.shah@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Eric Blake <eblake@redhat.com>
---
 block/snapshot.c         | 40 ++++++++++++++++++++++++++++++++++++++--
 hmp.c                    |  2 +-
 include/block/snapshot.h |  2 +-
 migration/savevm.c       | 11 ++++++-----
 qapi-schema.json         |  3 ++-
 qmp-commands.hx          |  6 ++++--
 6 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/block/snapshot.c b/block/snapshot.c
index 77affbc..237a015 100644
--- a/block/snapshot.c
+++ b/block/snapshot.c
@@ -25,6 +25,7 @@
 #include "block/snapshot.h"
 #include "block/block_int.h"
 #include "qapi/qmp/qerror.h"
+#include "sysemu/block-backend.h"
 
 QemuOptsList internal_snapshot_opts = {
     .name = "snapshot",
@@ -475,18 +476,53 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
     return err;
 }
 
-BlockDriverState *bdrv_all_find_vmstate_bs(void)
+
+BlockDriverState *bdrv_all_find_vmstate_bs(const char *device, Error **errp)
 {
     bool not_found = true;
     BlockDriverState *bs = NULL;
+    AioContext *ctx;
+
+    if (device != NULL) {
+        BlockBackend *blk = blk_by_name(device);
+        bool can_snapshot;
+
+        if (blk == NULL) {
+            error_set(errp, ERROR_CLASS_DEVICE_NOT_FOUND,
+                      "Device '%s' not found", device);
+            return NULL;
+        }
+        bs = blk_bs(blk);
+        if (bs == NULL) {
+            error_setg(errp, "Device '%s' does not have block driver attached",
+                       device);
+            return NULL;
+        }
+
+        ctx = bdrv_get_aio_context(bs);
+
+        aio_context_acquire(ctx);
+        can_snapshot =  bdrv_can_snapshot(bs);
+        aio_context_release(ctx);
+
+        if (!can_snapshot) {
+            error_setg(errp, "Device '%s' does not support snapshots", device);
+            return NULL;
+        }
+        return bs;
+    }
 
     while (not_found && (bs = bdrv_next(bs))) {
-        AioContext *ctx = bdrv_get_aio_context(bs);
+        ctx = bdrv_get_aio_context(bs);
 
         aio_context_acquire(ctx);
         not_found = !bdrv_can_snapshot(bs);
         aio_context_release(ctx);
     }
+
+    if (bs == NULL) {
+        error_setg(errp, "No block device can accept snapshots");
+    }
     return bs;
 }
 
diff --git a/hmp.c b/hmp.c
index f65bbe7..2c6a9a0 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2405,7 +2405,7 @@ void hmp_savevm(Monitor *mon, const QDict *qdict)
         name = name_buf;
     }
 
-    qmp_savevm(name, &local_err);
+    qmp_savevm(name, false, NULL, &local_err);
 
     if (local_err != NULL) {
         error_report_err(local_err);
diff --git a/include/block/snapshot.h b/include/block/snapshot.h
index a8506e9..a2caca9 100644
--- a/include/block/snapshot.h
+++ b/include/block/snapshot.h
@@ -91,7 +91,7 @@ int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              uint64_t vm_state_size,
                              BlockDriverState **first_bad_bs);
 
-BlockDriverState *bdrv_all_find_vmstate_bs(void);
+BlockDriverState *bdrv_all_find_vmstate_bs(const char *device, Error **errp);
 BlockDriverState *bdrv_all_validate_snapshot(const char *name, Error **errp);
 
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index fed8664..16ff92a 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1905,7 +1905,8 @@ int qemu_loadvm_state(QEMUFile *f)
     return ret;
 }
 
-void qmp_savevm(const char *name, Error **errp)
+void qmp_savevm(const char *name, bool has_device, const char *device,
+                Error **errp)
 {
     BlockDriverState *bs, *bs1;
     QEMUSnapshotInfo sn1, *sn = &sn1, old_sn1, *old_sn = &old_sn1;
@@ -1932,9 +1933,8 @@ void qmp_savevm(const char *name, Error **errp)
         return;
     }
 
-    bs = bdrv_all_find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs(has_device ? device : NULL, errp);
     if (bs == NULL) {
-        error_setg(errp, "No block device can accept snapshots");
         return;
     }
     aio_context = bdrv_get_aio_context(bs);
@@ -2097,10 +2097,11 @@ void hmp_info_snapshots(Monitor *mon, const QDict *qdict)
     int total;
     int *available_snapshots;
     AioContext *aio_context;
+    Error *local_err = NULL;
 
-    bs = bdrv_all_find_vmstate_bs();
+    bs = bdrv_all_find_vmstate_bs(NULL, &local_err);
     if (!bs) {
-        monitor_printf(mon, "No available block device supports snapshots\n");
+        error_report_err(local_err);
         return;
     }
     aio_context = bdrv_get_aio_context(bs);
diff --git a/qapi-schema.json b/qapi-schema.json
index 7d48948..cd6d97f 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -4061,12 +4061,13 @@
 # Save a VM snapshot. Old snapshot with the same name will be deleted if exists.
 #
 # @name: identifier of a snapshot to be created
+# @device: #optional device name to save VM state to
 #
 # Returns: Nothing on success
 #
 # Since 2.6
 ##
-{ 'command': 'savevm', 'data': {'name': 'str'} }
+{ 'command': 'savevm', 'data': {'name': 'str', '*device': 'str'} }
 
 ##
 # @delvm
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 9cd1bfe..9133f2c 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -4807,17 +4807,19 @@ Save a VM snapshot. Old snapshot with the same name will be deleted if exists.
 Arguments:
 
 - "name": snapshot name
+- "device": block device name
 
 Example:
 
--> { "execute": "savevm", "arguments": { "name": "snapshot1" } }
+-> { "execute": "savevm",
+     "arguments": { "name": "snapshot1", "device": "ide1-hd0" } }
 <- { "return": {} }
 
 EQMP
 
     {
         .name       = "savevm",
-        .args_type  = "name:s",
+        .args_type  = "name:s,device:s?",
         .mhandler.cmd_new = qmp_marshal_savevm,
     },
 
-- 
2.5.0