[Qemu-devel] [PATCH v4 1/6] block-commit: Expose granularity

[Max Reitz]

Allow QMP users to manipulate the granularity used in the block-commit
command.

Signed-off-by: Max Reitz <address@hidden>
Reviewed-by: Eric Blake <address@hidden>
---
 block/commit.c            | 16 +++++++++++++---
 block/mirror.c            |  4 ++--
 blockdev.c                | 22 ++++++++++++++++------
 include/block/block_int.h | 10 ++++++----
 qapi-schema.json          |  6 +++++-
 5 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/block/commit.c b/block/commit.c
index acec4ac..cf0e500 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -37,6 +37,7 @@ typedef struct CommitBlockJob {
     BlockdevOnError on_error;
     int base_flags;
     int orig_overlay_flags;
+    int64_t granularity;
 } CommitBlockJob;
 
 static int coroutine_fn commit_populate(BlockDriverState *bs,
@@ -93,7 +94,7 @@ static void coroutine_fn commit_run(void *opaque)
     }
 
     end = s->common.len >> BDRV_SECTOR_BITS;
-    buf = qemu_blockalign(top, COMMIT_BUFFER_SIZE);
+    buf = qemu_blockalign(top, s->granularity);
 
     for (sector_num = 0; sector_num < end; sector_num += n) {
         uint64_t delay_ns = 0;
@@ -109,7 +110,7 @@ wait:
         }
         /* Copy if allocated above the base */
         ret = bdrv_is_allocated_above(top, base, sector_num,
-                                      COMMIT_BUFFER_SIZE / BDRV_SECTOR_SIZE,
+                                      s->granularity / BDRV_SECTOR_SIZE,
                                       &n);
         copy = (ret == 1);
         trace_commit_one_iteration(s, sector_num, n, ret);
@@ -180,7 +181,7 @@ static const BlockJobDriver commit_job_driver = {
 };
 
 void commit_start(BlockDriverState *bs, BlockDriverState *base,
-                  BlockDriverState *top, int64_t speed,
+                  BlockDriverState *top, int64_t speed, int64_t granularity,
                   BlockdevOnError on_error, BlockDriverCompletionFunc *cb,
                   void *opaque, Error **errp)
 {
@@ -214,6 +215,13 @@ void commit_start(BlockDriverState *bs, BlockDriverState 
*base,
     orig_base_flags    = bdrv_get_flags(base);
     orig_overlay_flags = bdrv_get_flags(overlay_bs);
 
+    if (!granularity) {
+        granularity = COMMIT_BUFFER_SIZE;
+    }
+
+    assert(granularity >= BDRV_SECTOR_SIZE);
+    assert(is_power_of_2(granularity));
+
     /* convert base & overlay_bs to r/w, if necessary */
     if (!(orig_base_flags & BDRV_O_RDWR)) {
         reopen_queue = bdrv_reopen_queue(reopen_queue, base,
@@ -244,6 +252,8 @@ void commit_start(BlockDriverState *bs, BlockDriverState 
*base,
     s->base_flags          = orig_base_flags;
     s->orig_overlay_flags  = orig_overlay_flags;
 
+    s->granularity = granularity;
+
     s->on_error = on_error;
     s->common.co = qemu_coroutine_create(commit_run);
 
diff --git a/block/mirror.c b/block/mirror.c
index 0ef41f9..5b1ebb2 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -632,7 +632,7 @@ void mirror_start(BlockDriverState *bs, BlockDriverState 
*target,
 }
 
 void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
-                         int64_t speed,
+                         int64_t speed, int64_t granularity,
                          BlockdevOnError on_error,
                          BlockDriverCompletionFunc *cb,
                          void *opaque, Error **errp)
@@ -674,7 +674,7 @@ void commit_active_start(BlockDriverState *bs, 
BlockDriverState *base,
     }
 
     bdrv_ref(base);
-    mirror_start_job(bs, base, speed, 0, 0,
+    mirror_start_job(bs, base, speed, granularity, 0,
                      on_error, on_error, cb, opaque, &local_err,
                      &commit_active_job_driver, false, base);
     if (error_is_set(&local_err)) {
diff --git a/blockdev.c b/blockdev.c
index 5dd01ea..9d7bd04 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1865,8 +1865,8 @@ void qmp_block_stream(const char *device, bool has_base,
 
 void qmp_block_commit(const char *device,
                       bool has_base, const char *base, const char *top,
-                      bool has_speed, int64_t speed,
-                      Error **errp)
+                      bool has_speed, int64_t speed, bool has_granularity,
+                      int64_t granularity, Error **errp)
 {
     BlockDriverState *bs;
     BlockDriverState *base_bs, *top_bs;
@@ -1879,6 +1879,16 @@ void qmp_block_commit(const char *device,
     if (!has_speed) {
         speed = 0;
     }
+    if (!has_granularity) {
+        granularity = 0;
+    }
+
+    if (granularity &&
+        (granularity < BDRV_SECTOR_SIZE || !is_power_of_2(granularity)))
+    {
+        error_set(errp, QERR_INVALID_PARAMETER, "granularity");
+        return;
+    }
 
     /* drain all i/o before commits */
     bdrv_drain_all();
@@ -1915,11 +1925,11 @@ void qmp_block_commit(const char *device,
     }
 
     if (top_bs == bs) {
-        commit_active_start(bs, base_bs, speed, on_error, block_job_cb,
-                            bs, &local_err);
+        commit_active_start(bs, base_bs, speed, granularity, on_error,
+                            block_job_cb, bs, &local_err);
     } else {
-        commit_start(bs, base_bs, top_bs, speed, on_error, block_job_cb, bs,
-                    &local_err);
+        commit_start(bs, base_bs, top_bs, speed, granularity, on_error,
+                     block_job_cb, bs, &local_err);
     }
     if (local_err != NULL) {
         error_propagate(errp, local_err);
diff --git a/include/block/block_int.h b/include/block/block_int.h
index cd5bc73..c01b4aa 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -426,6 +426,7 @@ void stream_start(BlockDriverState *bs, BlockDriverState 
*base,
  * @top: Top block device to be committed.
  * @base: Block device that will be written into, and become the new top.
  * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
+ * @granularity: The granularity, in bytes, or 0 for a default value.
  * @on_error: The action to take upon error.
  * @cb: Completion function for the job.
  * @opaque: Opaque pointer value passed to @cb.
@@ -433,14 +434,15 @@ void stream_start(BlockDriverState *bs, BlockDriverState 
*base,
  *
  */
 void commit_start(BlockDriverState *bs, BlockDriverState *base,
-                 BlockDriverState *top, int64_t speed,
-                 BlockdevOnError on_error, BlockDriverCompletionFunc *cb,
-                 void *opaque, Error **errp);
+                  BlockDriverState *top, int64_t speed, int64_t granularity,
+                  BlockdevOnError on_error, BlockDriverCompletionFunc *cb,
+                  void *opaque, Error **errp);
 /**
  * commit_active_start:
  * @bs: Active block device to be committed.
  * @base: Block device that will be written into, and become the new top.
  * @speed: The maximum speed, in bytes per second, or 0 for unlimited.
+ * @granularity: The granularity, in bytes, or 0 for cluster size.
  * @on_error: The action to take upon error.
  * @cb: Completion function for the job.
  * @opaque: Opaque pointer value passed to @cb.
@@ -448,7 +450,7 @@ void commit_start(BlockDriverState *bs, BlockDriverState 
*base,
  *
  */
 void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
-                         int64_t speed,
+                         int64_t speed, int64_t granularity,
                          BlockdevOnError on_error,
                          BlockDriverCompletionFunc *cb,
                          void *opaque, Error **errp);
diff --git a/qapi-schema.json b/qapi-schema.json
index 391356f..151fad3 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -2112,6 +2112,10 @@
 #
 # @speed:  #optional the maximum speed, in bytes per second
 #
+# @granularity: #optional the granularity to be used for the operation, in
+#               bytes; has to be a power of two and at least 512, or 0 for the
+#               default value (since 2.1)
+#
 # Returns: Nothing on success
 #          If commit or stream is already active on this device, DeviceInUse
 #          If @device does not exist, DeviceNotFound
@@ -2124,7 +2128,7 @@
 ##
 { 'command': 'block-commit',
   'data': { 'device': 'str', '*base': 'str', 'top': 'str',
-            '*speed': 'int' } }
+            '*speed': 'int', '*granularity': 'int' } }
 
 ##
 # @drive-backup
-- 
1.9.2