[PATCH v2 11/20] qapi: backup: add x-max-chunk and x-max-workers parameters

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Add new parameters to configure future backup features. The patch
doesn't introduce aio backup requests (so we actually have only one
worker) neither requests larger than one cluster. Still, formally we
satisfy these maximums anyway, so add the parameters now, to facilitate
further patch which will really change backup job behavior.

Options are added with x- prefixes, as the only use for them are some
very conservative iotests which will be updated soon.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 qapi/block-core.json      |  9 ++++++++-
 include/block/block_int.h |  7 +++++++
 block/backup.c            | 21 +++++++++++++++++++++
 block/replication.c       |  2 +-
 blockdev.c                |  5 +++++
 5 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0c7600e4ec..f4abcde34e 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1407,6 +1407,12 @@
 #
 # @x-use-copy-range: use copy offloading if possible. Default true. (Since 5.1)
 #
+# @x-max-workers: maximum of parallel requests for static data backup. This
+#                 doesn't influence copy-before-write operations. (Since: 5.1)
+#
+# @x-max-chunk: maximum chunk length for static data backup. This doesn't
+#               influence copy-before-write operations. (Since: 5.1)
+#
 # Note: @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.
@@ -1421,7 +1427,8 @@
             '*on-source-error': 'BlockdevOnError',
             '*on-target-error': 'BlockdevOnError',
             '*auto-finalize': 'bool', '*auto-dismiss': 'bool',
-            '*filter-node-name': 'str', '*x-use-copy-range': 'bool'  } }
+            '*filter-node-name': 'str', '*x-use-copy-range': 'bool',
+            '*x-max-workers': 'int', '*x-max-chunk': 'int64' } }
 
 ##
 # @DriveBackup:
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 93b9b3bdc0..d93a170d37 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -1207,6 +1207,11 @@ void mirror_start(const char *job_id, BlockDriverState *bs,
  * @sync_mode: What parts of the disk image should be copied to the destination.
  * @sync_bitmap: The dirty bitmap if sync_mode is 'bitmap' or 'incremental'
  * @bitmap_mode: The bitmap synchronization policy to use.
+ * @max_workers: The limit for parallel requests for main backup loop.
+ *               Must be >= 1.
+ * @max_chunk: The limit for one IO operation length in main backup loop.
+ *             Must be not less than job cluster size or zero. Zero means no
+ *             specific limit.
  * @on_source_error: The action to take upon error reading from the source.
  * @on_target_error: The action to take upon error writing to the target.
  * @creation_flags: Flags that control the behavior of the Job lifetime.
@@ -1226,6 +1231,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                             bool compress,
                             const char *filter_node_name,
                             bool use_copy_range,
+                            int max_workers,
+                            int64_t max_chunk,
                             BlockdevOnError on_source_error,
                             BlockdevOnError on_target_error,
                             int creation_flags,
diff --git a/block/backup.c b/block/backup.c
index 76847b4daf..ec2676abc2 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -46,6 +46,8 @@ typedef struct BackupBlockJob {
     uint64_t len;
     uint64_t bytes_read;
     int64_t cluster_size;
+    int max_workers;
+    int64_t max_chunk;
 
     BlockCopyState *bcs;
 } BackupBlockJob;
@@ -335,6 +337,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
                   bool compress,
                   const char *filter_node_name,
                   bool use_copy_range,
+                  int max_workers,
+                  int64_t max_chunk,
                   BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
                   int creation_flags,
@@ -355,6 +359,16 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     assert(sync_mode != MIRROR_SYNC_MODE_INCREMENTAL);
     assert(sync_bitmap || sync_mode != MIRROR_SYNC_MODE_BITMAP);
 
+    if (max_workers < 1) {
+        error_setg(errp, "At least one worker needed");
+        return NULL;
+    }
+
+    if (max_chunk < 0) {
+        error_setg(errp, "max-chunk is negative");
+        return NULL;
+    }
+
     if (bs == target) {
         error_setg(errp, "Source and target cannot be the same");
         return NULL;
@@ -422,6 +436,11 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     if (cluster_size < 0) {
         goto error;
     }
+    if (max_chunk && max_chunk < cluster_size) {
+        error_setg(errp, "Required max-chunk (%" PRIi64") is less than backup "
+                   "cluster size (%" PRIi64 ")", max_chunk, cluster_size);
+        return NULL;
+    }
 
     /*
      * If source is in backing chain of target assume that target is going to be
@@ -465,6 +484,8 @@ BlockJob *backup_job_create(const char *job_id, BlockDriverState *bs,
     job->bcs = bcs;
     job->cluster_size = cluster_size;
     job->len = len;
+    job->max_workers = max_workers;
+    job->max_chunk = max_chunk;
 
     block_copy_set_progress_callback(bcs, backup_progress_bytes_callback, job);
     block_copy_set_progress_meter(bcs, &job->common.job.progress);
diff --git a/block/replication.c b/block/replication.c
index 25987eab0f..a9ee82db80 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -563,7 +563,7 @@ static void replication_start(ReplicationState *rs, ReplicationMode mode,
         s->backup_job = backup_job_create(
                                 NULL, s->secondary_disk->bs, s->hidden_disk->bs,
                                 0, MIRROR_SYNC_MODE_NONE, NULL, 0, false, NULL,
-                                true,
+                                true, 0, 0,
                                 BLOCKDEV_ON_ERROR_REPORT,
                                 BLOCKDEV_ON_ERROR_REPORT, JOB_INTERNAL,
                                 backup_job_completed, bs, NULL, &local_err);
diff --git a/blockdev.c b/blockdev.c
index 28145afe7d..cf068d20fa 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2743,6 +2743,9 @@ static BlockJob *do_backup_common(BackupCommon *backup,
     if (!backup->has_compress) {
         backup->compress = false;
     }
+    if (!backup->has_x_max_workers) {
+        backup->x_max_workers = 64;
+    }
 
     if ((backup->sync == MIRROR_SYNC_MODE_BITMAP) ||
         (backup->sync == MIRROR_SYNC_MODE_INCREMENTAL)) {
@@ -2822,6 +2825,8 @@ static BlockJob *do_backup_common(BackupCommon *backup,
                             backup->compress,
                             backup->filter_node_name,
                             backup->x_use_copy_range,
+                            backup->x_max_workers,
+                            backup->x_max_chunk,
                             backup->on_source_error,
                             backup->on_target_error,
                             job_flags, NULL, NULL, txn, errp);
-- 
2.21.0