qmp: Add optional bool "unmap" to drive-mirror

If specified as "true", it allows discarding on target sectors where source is
not allocated.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/mirror.c

@@ -58,6 +58,7 @@ typedef struct MirrorBlockJob {
     int in_flight;
     int sectors_in_flight;
     int ret;
+    bool unmap;
 } MirrorBlockJob;
 
 typedef struct MirrorOp {
@@ -652,6 +653,7 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
                              int64_t buf_size,
                              BlockdevOnError on_source_error,
                              BlockdevOnError on_target_error,
+                             bool unmap,
                              BlockCompletionFunc *cb,
                              void *opaque, Error **errp,
                              const BlockJobDriver *driver,
@@ -686,6 +688,7 @@ static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
     s->base = base;
     s->granularity = granularity;
     s->buf_size = MAX(buf_size, granularity);
+    s->unmap = unmap;
 
     s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity, NULL, errp);
     if (!s->dirty_bitmap) {
@@ -704,6 +707,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
                   int64_t speed, uint32_t granularity, int64_t buf_size,
                   MirrorSyncMode mode, BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
+                  bool unmap,
                   BlockCompletionFunc *cb,
                   void *opaque, Error **errp)
 {
@@ -718,7 +722,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
     base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL;
     mirror_start_job(bs, target, replaces,
                      speed, granularity, buf_size,
-                     on_source_error, on_target_error, cb, opaque, errp,
+                     on_source_error, on_target_error, unmap, cb, opaque, errp,
                      &mirror_job_driver, is_none_mode, base);
 }
 
@@ -766,7 +770,7 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
 
     bdrv_ref(base);
     mirror_start_job(bs, base, NULL, speed, 0, 0,
-                     on_error, on_error, cb, opaque, &local_err,
+                     on_error, on_error, false, cb, opaque, &local_err,
                      &commit_active_job_driver, false, base);
     if (local_err) {
         error_propagate(errp, local_err);

blockdev.c

@@ -2655,6 +2655,7 @@ void qmp_drive_mirror(const char *device, const char *target,
                       bool has_buf_size, int64_t buf_size,
                       bool has_on_source_error, BlockdevOnError on_source_error,
                       bool has_on_target_error, BlockdevOnError on_target_error,
+                      bool has_unmap, bool unmap,
                       Error **errp)
 {
     BlockBackend *blk;
@@ -2686,6 +2687,9 @@ void qmp_drive_mirror(const char *device, const char *target,
     if (!has_buf_size) {
         buf_size = DEFAULT_MIRROR_BUF_SIZE;
     }
+    if (!has_unmap) {
+        unmap = true;
+    }
 
     if (granularity != 0 && (granularity < 512 || granularity > 1048576 * 64)) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "granularity",
@@ -2827,6 +2831,7 @@ void qmp_drive_mirror(const char *device, const char *target,
                  has_replaces ? replaces : NULL,
                  speed, granularity, buf_size, sync,
                  on_source_error, on_target_error,
+                 unmap,
                  block_job_cb, bs, &local_err);
     if (local_err != NULL) {
         bdrv_unref(target_bs);

hmp.c

@@ -1061,7 +1061,7 @@ void hmp_drive_mirror(Monitor *mon, const QDict *qdict)
                      false, NULL, false, NULL,
                      full ? MIRROR_SYNC_MODE_FULL : MIRROR_SYNC_MODE_TOP,
                      true, mode, false, 0, false, 0, false, 0,
-                     false, 0, false, 0, &err);
+                     false, 0, false, 0, false, true, &err);
     hmp_handle_error(mon, &err);
 }
 

include/block/block_int.h

@@ -612,6 +612,7 @@ void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
  * @mode: Whether to collapse all images in the chain to the target.
  * @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.
+ * @unmap: Whether to unmap target where source sectors only contain zeroes.
  * @cb: Completion function for the job.
  * @opaque: Opaque pointer value passed to @cb.
  * @errp: Error object.
@@ -626,6 +627,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState *target,
                   int64_t speed, uint32_t granularity, int64_t buf_size,
                   MirrorSyncMode mode, BlockdevOnError on_source_error,
                   BlockdevOnError on_target_error,
+                  bool unmap,
                   BlockCompletionFunc *cb,
                   void *opaque, Error **errp);
 

qapi/block-core.json

@@ -975,6 +975,11 @@
 # @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).
+# @unmap: #optional Whether to try to unmap target sectors where source has
+#         only zero. If true, and target unallocated sectors will read as zero,
+#         target image sectors will be unmapped; otherwise, zeroes will be
+#         written. Both will result in identical contents.
+#         Default is true. (Since 2.4)
 #
 # Returns: nothing on success
 #          If @device is not a valid block device, DeviceNotFound
@@ -987,7 +992,8 @@
             'sync': 'MirrorSyncMode', '*mode': 'NewImageMode',
             '*speed': 'int', '*granularity': 'uint32',
             '*buf-size': 'int', '*on-source-error': 'BlockdevOnError',
-            '*on-target-error': 'BlockdevOnError' } }
+            '*on-target-error': 'BlockdevOnError',
+            '*unmap': 'bool' } }
 
 ##
 # @BlockDirtyBitmap

qmp-commands.hx

@@ -1503,6 +1503,7 @@ EQMP
         .args_type  = "sync:s,device:B,target:s,speed:i?,mode:s?,format:s?,"
                       "node-name:s?,replaces:s?,"
                       "on-source-error:s?,on-target-error:s?,"
+                      "unmap:b?,"
                       "granularity:i?,buf-size:i?",
         .mhandler.cmd_new = qmp_marshal_input_drive_mirror,
     },
@@ -1542,6 +1543,8 @@ Arguments:
   (BlockdevOnError, default 'report')
 - "on-target-error": the action to take on an error on the target
   (BlockdevOnError, default 'report')
+- "unmap": whether the target sectors should be discarded where source has only
+  zeroes. (json-bool, optional, default true)
 
 The default value of the granularity is the image cluster size clamped
 between 4096 and 65536, if the image format defines one.  If the format