drive-backup: added support for data compression

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.

The patch adds a flag to the qmp/hmp drive-backup command which enables
block compression. Compression should be implemented in the format driver
to enable this feature.

There are some limitations of the format driver to allow compressed writes.
We can write data only once. Though for backup this is perfectly fine.
These limitations are maintained by the driver and the error will be
reported if we are doing something wrong.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.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>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/backup.c b/block/backup.c
index 2c0532314f5f796fe6b70897736647dc8da55683..bb3bb9a9eb0f7a52d70b5996becbc0ad38fc40fe 100644 (file)
--- a/block/backup.c
+++ b/block/backup.c
@@ -47,6 +47,7 @@ typedef struct BackupBlockJob {
     uint64_t sectors_read;
     unsigned long *done_bitmap;
     int64_t cluster_size;
+    bool compress;
     NotifierWithReturn before_write;
     QLIST_HEAD(, CowRequest) inflight_reqs;
 } BackupBlockJob;
@@ -154,7 +155,8 @@ static int coroutine_fn backup_do_cow(BackupBlockJob *job,
                                        bounce_qiov.size, BDRV_REQ_MAY_UNMAP);
         } else {
             ret = blk_co_pwritev(job->target, start * job->cluster_size,
-                                 bounce_qiov.size, &bounce_qiov, 0);
+                                 bounce_qiov.size, &bounce_qiov,
+                                 job->compress ? BDRV_REQ_WRITE_COMPRESSED : 0);
         }
         if (ret < 0) {
             trace_backup_do_cow_write_fail(job, start, ret);
@@ -477,6 +479,7 @@ static void coroutine_fn backup_run(void *opaque)
 void backup_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *target, int64_t speed,
                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
+                  bool compress,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   BlockCompletionFunc *cb, void *opaque,
@@ -507,6 +510,12 @@ void backup_start(const char *job_id, BlockDriverState *bs,
         return;
     }
 
+    if (compress && target->drv->bdrv_co_pwritev_compressed == NULL) {
+        error_setg(errp, "Compression is not supported for this drive %s",
+                   bdrv_get_device_name(target));
+        return;
+    }
+
     if (bdrv_op_is_blocked(bs, BLOCK_OP_TYPE_BACKUP_SOURCE, errp)) {
         return;
     }
@@ -555,6 +564,7 @@ void backup_start(const char *job_id, BlockDriverState *bs,
     job->sync_mode = sync_mode;
     job->sync_bitmap = sync_mode == MIRROR_SYNC_MODE_INCREMENTAL ?
                        sync_bitmap : NULL;
+    job->compress = compress;
 
     /* If there is no backing file on the target, we cannot rely on COW if our
      * backup cluster size is smaller than the target cluster size. Even for

diff --git a/blockdev.c b/blockdev.c
index 5f1b01518ddfcf3d9f8c3d43258c8d31c08b30ec..f5857d018740f169ea28a9c18a2460642fa45093 100644 (file)
--- a/blockdev.c
+++ b/blockdev.c
@@ -3132,6 +3132,9 @@ static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
     if (!backup->has_job_id) {
         backup->job_id = NULL;
     }
+    if (!backup->has_compress) {
+        backup->compress = false;
+    }
 
     bs = qmp_get_root_bs(backup->device, errp);
     if (!bs) {
@@ -3210,8 +3213,8 @@ static void do_drive_backup(DriveBackup *backup, BlockJobTxn *txn, Error **errp)
     }
 
     backup_start(backup->job_id, bs, target_bs, backup->speed, backup->sync,
-                 bmap, backup->on_source_error, backup->on_target_error,
-                 block_job_cb, bs, txn, &local_err);
+                 bmap, backup->compress, backup->on_source_error,
+                 backup->on_target_error, block_job_cb, bs, txn, &local_err);
     bdrv_unref(target_bs);
     if (local_err != NULL) {
         error_propagate(errp, local_err);
@@ -3277,7 +3280,7 @@ void do_blockdev_backup(BlockdevBackup *backup, BlockJobTxn *txn, Error **errp)
         }
     }
     backup_start(backup->job_id, bs, target_bs, backup->speed, backup->sync,
-                 NULL, backup->on_source_error, backup->on_target_error,
+                 NULL, false, backup->on_source_error, backup->on_target_error,
                  block_job_cb, bs, txn, &local_err);
     if (local_err != NULL) {
         error_propagate(errp, local_err);

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 848efee5d19610b06ccd4152db5f20778fb32b5f..74f32e515cdf3ab5a783702ad680dfa1a5f178ad 100644 (file)
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1182,8 +1182,8 @@ ETEXI
 
     {
         .name       = "drive_backup",
-        .args_type  = "reuse:-n,full:-f,device:B,target:s,format:s?",
-        .params     = "[-n] [-f] device target [format]",
+        .args_type  = "reuse:-n,full:-f,compress:-c,device:B,target:s,format:s?",
+        .params     = "[-n] [-f] [-c] device target [format]",
         .help       = "initiates a point-in-time\n\t\t\t"
                       "copy for a device. The device's contents are\n\t\t\t"
                       "copied to the new image file, excluding data that\n\t\t\t"
@@ -1191,7 +1191,9 @@ ETEXI
                       "The -n flag requests QEMU to reuse the image found\n\t\t\t"
                       "in new-image-file, instead of recreating it from scratch.\n\t\t\t"
                       "The -f flag requests QEMU to copy the whole disk,\n\t\t\t"
-                      "so that the result does not need a backing file.\n\t\t\t",
+                      "so that the result does not need a backing file.\n\t\t\t"
+                      "The -c flag requests QEMU to compress backup data\n\t\t\t"
+                      "(if the target format supports it).\n\t\t\t",
         .mhandler.cmd = hmp_drive_backup,
     },
 STEXI

diff --git a/hmp.c b/hmp.c
index 3c06200e4898feed7ccd56e0588522a088b90318..a7dfe6fa11d61b064a628ba02af33e957e50cda3 100644 (file)
--- a/hmp.c
+++ b/hmp.c
@@ -1109,6 +1109,7 @@ void hmp_drive_backup(Monitor *mon, const QDict *qdict)
     const char *format = qdict_get_try_str(qdict, "format");
     bool reuse = qdict_get_try_bool(qdict, "reuse", false);
     bool full = qdict_get_try_bool(qdict, "full", false);
+    bool compress = qdict_get_try_bool(qdict, "compress", false);
     Error *err = NULL;
     DriveBackup backup = {
         .device = (char *)device,
@@ -1118,6 +1119,8 @@ void hmp_drive_backup(Monitor *mon, const QDict *qdict)
         .sync = full ? MIRROR_SYNC_MODE_FULL : MIRROR_SYNC_MODE_TOP,
         .has_mode = true,
         .mode = reuse ? NEW_IMAGE_MODE_EXISTING : NEW_IMAGE_MODE_ABSOLUTE_PATHS,
+        .has_compress = !!compress,
+        .compress = compress,
     };
 
     if (!filename) {

diff --git a/include/block/block_int.h b/include/block/block_int.h
index 9c61f49f9404245faaa71c70799f766721ad8044..0ca6a78eb3b425041cbe158291fa0292f74cb0fa 100644 (file)
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -765,6 +765,7 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
 void backup_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *target, int64_t speed,
                   MirrorSyncMode sync_mode, BdrvDirtyBitmap *sync_bitmap,
+                  bool compress,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   BlockCompletionFunc *cb, void *opaque,

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 4c8cf057b542ee57152c7fd03ea48471ad16d457..300a68b63a9c7baca2fc63b3e8cceccc186eab35 100644 (file)
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -898,6 +898,9 @@
 #          Must be present if sync is "incremental", must NOT be present
 #          otherwise. (Since 2.4)
 #
+# @compress: #optional true to compress data, if the target format supports it.
+#            (default: false) (since 2.7)
+#
 # @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).
@@ -915,7 +918,7 @@
 { 'struct': 'DriveBackup',
   'data': { '*job-id': 'str', 'device': 'str', 'target': 'str',
             '*format': 'str', 'sync': 'MirrorSyncMode', '*mode': 'NewImageMode',
-            '*speed': 'int', '*bitmap': 'str',
+            '*speed': 'int', '*bitmap': 'str', '*compress': 'bool',
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError' } }
 

diff --git a/qmp-commands.hx b/qmp-commands.hx
index 956f1b0f477b2b09be437fac79969ecd957f7407..d1593c91ffb3bd1163ecffa16b833c0081130403 100644 (file)
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -1217,7 +1217,8 @@ EQMP
     {
         .name       = "drive-backup",
         .args_type  = "job-id:s?,sync:s,device:B,target:s,speed:i?,mode:s?,"
-                      "format:s?,bitmap:s?,on-source-error:s?,on-target-error:s?",
+                      "format:s?,bitmap:s?,compress:b?,"
+                      "on-source-error:s?,on-target-error:s?",
         .mhandler.cmd_new = qmp_marshal_drive_backup,
     },
 
@@ -1253,6 +1254,8 @@ Arguments:
 - "mode": whether and how QEMU should create a new image
           (NewImageMode, optional, default 'absolute-paths')
 - "speed": the maximum speed, in bytes per second (json-int, optional)
+- "compress": true to compress data, 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.