[Qemu-devel] [PATCH 09/11] blockdev-backup: added support for data compression

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

From: Pavel Butsykin <pbutsykin@virtuozzo.com>

The idea is simple - backup is "written-once" data. It is written block
by block and it is large enough. It would be nice to save storage
space and compress it.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Jeff Cody <jcody@redhat.com>
CC: Markus Armbruster <armbru@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: John Snow <jsnow@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
---
 blockdev.c           | 10 +++++++++-
 qapi/block-core.json |  4 ++++
 qmp-commands.hx      |  4 +++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/blockdev.c b/blockdev.c
index b24f508..e72dddf 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1924,6 +1924,7 @@ typedef struct BlockdevBackupState {
 static void do_blockdev_backup(const char *device, const char *target,
                                enum MirrorSyncMode sync,
                                bool has_speed, int64_t speed,
+                               bool has_compress, bool compress,
                                bool has_on_source_error,
                                BlockdevOnError on_source_error,
                                bool has_on_target_error,
@@ -1971,6 +1972,7 @@ static void blockdev_backup_prepare(BlkActionState *common, Error **errp)
     do_blockdev_backup(backup->device, backup->target,
                        backup->sync,
                        backup->has_speed, backup->speed,
+                       backup->has_compress, backup->compress,
                        backup->has_on_source_error, backup->on_source_error,
                        backup->has_on_target_error, backup->on_target_error,
                        common->block_job_txn, &local_err);
@@ -3337,6 +3339,7 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
 void do_blockdev_backup(const char *device, const char *target,
                          enum MirrorSyncMode sync,
                          bool has_speed, int64_t speed,
+                         bool has_compress, bool compress,
                          bool has_on_source_error,
                          BlockdevOnError on_source_error,
                          bool has_on_target_error,
@@ -3358,6 +3361,9 @@ void do_blockdev_backup(const char *device, const char *target,
     if (!has_on_target_error) {
         on_target_error = BLOCKDEV_ON_ERROR_REPORT;
     }
+    if (!has_compress) {
+        compress = false;
+    }
 
     blk = blk_by_name(device);
     if (!blk) {
@@ -3387,7 +3393,7 @@ void do_blockdev_backup(const char *device, const char *target,
     target_bs = blk_bs(target_blk);
 
     bdrv_set_aio_context(target_bs, aio_context);
-    backup_start(bs, target_bs, speed, sync, NULL, false, on_source_error,
+    backup_start(bs, target_bs, speed, sync, NULL, compress, on_source_error,
                  on_target_error, block_job_cb, bs, txn, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
@@ -3399,6 +3405,7 @@ out:
 void qmp_blockdev_backup(const char *device, const char *target,
                          enum MirrorSyncMode sync,
                          bool has_speed, int64_t speed,
+                         bool has_compress, bool compress,
                          bool has_on_source_error,
                          BlockdevOnError on_source_error,
                          bool has_on_target_error,
@@ -3406,6 +3413,7 @@ void qmp_blockdev_backup(const char *device, const char *target,
                          Error **errp)
 {
     do_blockdev_backup(device, target, sync, has_speed, speed,
+                       has_compress, compress,
                        has_on_source_error, on_source_error,
                        has_on_target_error, on_target_error,
                        NULL, errp);
diff --git a/qapi/block-core.json b/qapi/block-core.json
index e54ceb2..f6a971c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -926,6 +926,9 @@
 # @speed: #optional the maximum speed, in bytes per second. The default is 0,
 #         for unlimited.
 #
+# @compress: #optional the compression data blocks (if the target format
+#            supports it; default: false).
+#
 # @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).
@@ -944,6 +947,7 @@
   'data': { 'device': 'str', 'target': 'str',
             'sync': 'MirrorSyncMode',
             '*speed': 'int',
+            '*compress': 'bool',
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError' } }
 
diff --git a/qmp-commands.hx b/qmp-commands.hx
index ff927ae..19a0427 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1242,7 +1242,7 @@ EQMP
 
     {
         .name       = "blockdev-backup",
-        .args_type  = "sync:s,device:B,target:B,speed:i?,"
+        .args_type  = "sync:s,device:B,target:B,speed:i?,compress:b?,"
                       "on-source-error:s?,on-target-error:s?",
         .mhandler.cmd_new = qmp_marshal_blockdev_backup,
     },
@@ -1264,6 +1264,8 @@ Arguments:
           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)
+- "compress": the compression data blocks (if the target format supports it).
+              (json-bool, optional, default false)
 - "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.
-- 
2.1.4