[PATCH v7 13/13] block: Convert 'block_resize' to coroutine

[Kevin Wolf]

block_resize performs some I/O that could potentially take quite some
time, so use it as an example for the new 'coroutine': true annotation
in the QAPI schema.

bdrv_truncate() requires that we're already in the right AioContext for
the BlockDriverState if called in coroutine context. So instead of just
taking the AioContext lock, move the QMP handler coroutine to the
context.

Call blk_unref() only after switching back because blk_unref() may only
be called in the main thread.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qapi/block-core.json |  3 ++-
 blockdev.c           | 13 ++++++-------
 hmp-commands.hx      |  1 +
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 0345f6f2d2..d3e49c9419 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1302,7 +1302,8 @@
 { 'command': 'block_resize',
   'data': { '*device': 'str',
             '*node-name': 'str',
-            'size': 'int' } }
+            'size': 'int' },
+  'coroutine': true }
 
 ##
 # @NewImageMode:
diff --git a/blockdev.c b/blockdev.c
index 7f2561081e..064989fc2d 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -2439,14 +2439,14 @@ BlockDirtyBitmapSha256 
*qmp_x_debug_block_dirty_bitmap_sha256(const char *node,
     return ret;
 }
 
-void qmp_block_resize(bool has_device, const char *device,
-                      bool has_node_name, const char *node_name,
-                      int64_t size, Error **errp)
+void coroutine_fn qmp_block_resize(bool has_device, const char *device,
+                                   bool has_node_name, const char *node_name,
+                                   int64_t size, Error **errp)
 {
     Error *local_err = NULL;
     BlockBackend *blk = NULL;
     BlockDriverState *bs;
-    AioContext *aio_context;
+    AioContext *old_ctx;
 
     bs = bdrv_lookup_bs(has_device ? device : NULL,
                         has_node_name ? node_name : NULL,
@@ -2456,8 +2456,7 @@ void qmp_block_resize(bool has_device, const char *device,
         return;
     }
 
-    aio_context = bdrv_get_aio_context(bs);
-    aio_context_acquire(aio_context);
+    old_ctx = bdrv_co_move_to_aio_context(bs);
 
     if (size < 0) {
         error_setg(errp, QERR_INVALID_PARAMETER_VALUE, "size", "a >0 size");
@@ -2479,8 +2478,8 @@ void qmp_block_resize(bool has_device, const char *device,
     bdrv_drained_end(bs);
 
 out:
+    aio_co_reschedule_self(old_ctx);
     blk_unref(blk);
-    aio_context_release(aio_context);
 }
 
 void qmp_block_stream(bool has_job_id, const char *job_id, const char *device,
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 60f395c276..ac360b73f6 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -76,6 +76,7 @@ ERST
         .params     = "device size",
         .help       = "resize a block image",
         .cmd        = hmp_block_resize,
+        .coroutine  = true,
     },
 
 SRST
-- 
2.25.4