[Qemu-devel] [PATCH v13 10/14] qmp: Add command 'blockdev-backup'

[Fam Zheng]

Similar to drive-backup, but this command uses a device id as target
instead of creating/opening an image file.

Also add blocker on target bs, since the target is also a named device
now.

Add check and report error for bs == target which became possible but is
an illegal case with introduction of blockdev-backup.

Signed-off-by: Fam Zheng <address@hidden>
---
 block/backup.c   | 26 ++++++++++++++++++++++++++
 blockdev.c       | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 qapi-schema.json | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 qmp-commands.hx  | 44 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 166 insertions(+)

diff --git a/block/backup.c b/block/backup.c
index 15a2e55..ea46340 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -344,6 +344,7 @@ static void coroutine_fn backup_run(void *opaque)
     hbitmap_free(job->bitmap);
 
     bdrv_iostatus_disable(target);
+    bdrv_op_unblock_all(target, job->common.blocker);
     bdrv_unref(target);
 
     block_job_completed(&job->common, ret);
@@ -362,6 +363,11 @@ void backup_start(BlockDriverState *bs, BlockDriverState 
*target,
     assert(target);
     assert(cb);
 
+    if (bs == target) {
+        error_setg(errp, "Source and target cannot be the same");
+        return;
+    }
+
     if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
          on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
         !bdrv_iostatus_is_enabled(bs)) {
@@ -369,6 +375,24 @@ void backup_start(BlockDriverState *bs, BlockDriverState 
*target,
         return;
     }
 
+    if (!bdrv_is_inserted(bs)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, bs->device_name);
+        return;
+    }
+
+    if (!bdrv_is_inserted(target)) {
+        error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, target->device_name);
+        return;
+    }
+
+    if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
+        return;
+    }
+
+    if (bdrv_op_is_blocked(target, BLOCK_OP_TYPE_BACKUP_TARGET, errp)) {
+        return;
+    }
+
     len = bdrv_getlength(bs);
     if (len < 0) {
         error_setg_errno(errp, -len, "unable to get length for '%s'",
@@ -382,6 +406,8 @@ void backup_start(BlockDriverState *bs, BlockDriverState 
*target,
         return;
     }
 
+    bdrv_op_block_all(target, job->common.blocker);
+
     job->on_source_error = on_source_error;
     job->on_target_error = on_target_error;
     job->target = target;
diff --git a/blockdev.c b/blockdev.c
index ffaa6a9..b346cc1 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1940,6 +1940,8 @@ void qmp_drive_backup(const char *device, const char 
*target,
         return;
     }
 
+    /* Although backup_run has this check too, we need to use bs->drv below, so
+     * do an early check redundantly. */
     if (!bdrv_is_inserted(bs)) {
         error_set(errp, QERR_DEVICE_HAS_NO_MEDIUM, device);
         return;
@@ -1956,6 +1958,7 @@ void qmp_drive_backup(const char *device, const char 
*target,
         }
     }
 
+    /* Early check to avoid creating target */
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
         return;
     }
@@ -2019,6 +2022,50 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(Error 
**errp)
     return bdrv_named_nodes_list();
 }
 
+void qmp_blockdev_backup(const char *device, const char *target,
+                         enum MirrorSyncMode sync,
+                         bool has_speed, int64_t speed,
+                         bool has_on_source_error,
+                         BlockdevOnError on_source_error,
+                         bool has_on_target_error,
+                         BlockdevOnError on_target_error,
+                         Error **errp)
+{
+    BlockDriverState *bs;
+    BlockDriverState *target_bs;
+    Error *local_err = NULL;
+
+    if (!has_speed) {
+        speed = 0;
+    }
+    if (!has_on_source_error) {
+        on_source_error = BLOCKDEV_ON_ERROR_REPORT;
+    }
+    if (!has_on_target_error) {
+        on_target_error = BLOCKDEV_ON_ERROR_REPORT;
+    }
+
+    bs = bdrv_find(device);
+    if (!bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, device);
+        return;
+    }
+
+    target_bs = bdrv_find(target);
+    if (!target_bs) {
+        error_set(errp, QERR_DEVICE_NOT_FOUND, target);
+        return;
+    }
+
+    bdrv_ref(target_bs);
+    backup_start(bs, target_bs, speed, sync, on_source_error, on_target_error,
+                 block_job_cb, bs, &local_err);
+    if (local_err != NULL) {
+        bdrv_unref(target_bs);
+        error_propagate(errp, local_err);
+    }
+}
+
 #define DEFAULT_MIRROR_BUF_SIZE   (10 << 20)
 
 void qmp_drive_mirror(const char *device, const char *target,
diff --git a/qapi-schema.json b/qapi-schema.json
index 05ced9d..a92e1be 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -1840,6 +1840,40 @@
             '*on-target-error': 'BlockdevOnError' } }
 
 ##
+# @BlockdevBackup
+#
+# @device: the name of the device which should be copied.
+#
+# @target: the name of the backup target device.
+#
+# @sync: what parts of the disk image should be copied to the destination
+#        (all the disk, only the sectors allocated in the topmost image, or
+#        only new I/O).
+#
+# @speed: #optional the maximum speed, in bytes per second.
+#
+# @on-source-error: #optional the action to take on an error on the source,
+#                   default 'report'.  'stop' and 'enospc' can only be used
+#                   if the block device supports io-status (see BlockInfo).
+#
+# @on-target-error: #optional the action to take on an error on the target,
+#                   default 'report' (no limitations, since this applies to
+#                   a different block device than @device).
+#
+# Note that @on-source-error and @on-target-error only affect background I/O.
+# If an error occurs during a guest write request, the device's rerror/werror
+# actions will be used.
+#
+# Since: 2.0
+##
+{ 'type': 'BlockdevBackup',
+  'data': { 'device': 'str', 'target': 'str',
+            'sync': 'MirrorSyncMode',
+            '*speed': 'int',
+            '*on-source-error': 'BlockdevOnError',
+            '*on-target-error': 'BlockdevOnError' } }
+
+##
 # @Abort
 #
 # This action can be used to test transaction failure.
@@ -2048,6 +2082,21 @@
 { 'command': 'query-named-block-nodes', 'returns': [ 'BlockDeviceInfo' ] }
 
 ##
+# @blockdev-backup
+#
+# Block device version for drive-backup command. Use existing device as target
+# of backup.
+#
+# For the arguments, see the documentation of BlockdevBackup.
+#
+# Returns: Nothing on success.
+#          If @device or @target is not a valid block device, DeviceNotFound.
+#
+# Since 2.0
+##
+{ 'command': 'blockdev-backup', 'data': 'BlockdevBackup' }
+
+##
 # @drive-mirror
 #
 # Start mirroring a block device's writes to a new destination.
diff --git a/qmp-commands.hx b/qmp-commands.hx
index cce6b81..c3ee46a 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1054,6 +1054,50 @@ Example:
                                                "sync": "full",
                                                "target": "backup.img" } }
 <- { "return": {} }
+
+EQMP
+
+    {
+        .name       = "blockdev-backup",
+        .args_type  = "sync:s,device:B,target:B,speed:i?,"
+                      "on-source-error:s?,on-target-error:s?",
+        .mhandler.cmd_new = qmp_marshal_input_blockdev_backup,
+    },
+
+SQMP
+blockdev-backup
+------------
+
+The device version of drive-backup: this command takes a existing named device
+as backup target.
+
+Arguments:
+
+- "device": the name of the device which should be copied.
+            (json-string)
+- "target": the target of the new image. If the file exists, or if it is a
+            device, the existing file/device will be used as the new
+            destination.  If it does not exist, a new file will be created.
+            (json-string)
+- "sync": what parts of the disk image should be copied to the destination;
+          possibilities include "full" for all the disk, "top" for only the
+          sectors allocated in the topmost image, or "none" to only replicate
+          new I/O (MirrorSyncMode).
+- "speed": the maximum speed, in bytes per second (json-int, optional)
+- "on-source-error": the action to take on an error on the source, default
+                     'report'.  'stop' and 'enospc' can only be used
+                     if the block device supports io-status.
+                     (BlockdevOnError, optional)
+- "on-target-error": the action to take on an error on the target, default
+                     'report' (no limitations, since this applies to
+                     a different block device than device).
+                     (BlockdevOnError, optional)
+
+Example:
+-> { "execute": "blockdev-backup", "arguments": { "device": "src-id",
+                                                  "target": "tgt-id" } }
+<- { "return": {} }
+
 EQMP
 
     {
-- 
1.8.5.3