[Qemu-devel] [PATCH 1/2] block: add the support for draining the throttled request queue

[zwu . kernel]

From: Zhi Yong Wu <address@hidden>

If one guest has multiple disks with enabling I/O throttling function 
separately, when draining activities are done, some requests maybe are in the 
throttled queue; So we need to restart them at first.

Moreover, when only one disk need to be drained such as hotplug out, if another 
disk still has some requests in its throttled queue, these request should not 
be effected.

Signed-off-by: Zhi Yong Wu <address@hidden>
---
 block.c     |   29 ++++++++++++++++++++++-------
 block_int.h |    1 +
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/block.c b/block.c
index ae297bb..f78df78 100644
--- a/block.c
+++ b/block.c
@@ -853,25 +853,40 @@ void bdrv_close_all(void)
     }
 }
 
-/*
- * Wait for pending requests to complete across all BlockDriverStates
- *
- * This function does not flush data to disk, use bdrv_flush_all() for that
- * after calling this function.
- */
-void bdrv_drain_all(void)
+void bdrv_drain_request(BlockDriverState *throttled_bs)
 {
     BlockDriverState *bs;
 
+    QTAILQ_FOREACH(bs, &bdrv_states, list) {
+        if (throttled_bs && throttled_bs != bs) {
+            continue;
+        }
+        qemu_co_queue_restart_all(&bs->throttled_reqs);
+    }
+
     qemu_aio_flush();
 
     /* If requests are still pending there is a bug somewhere */
     QTAILQ_FOREACH(bs, &bdrv_states, list) {
         assert(QLIST_EMPTY(&bs->tracked_requests));
+        if (throttled_bs && throttled_bs != bs) {
+            continue;
+        }
         assert(qemu_co_queue_empty(&bs->throttled_reqs));
     }
 }
 
+/*
+ * Wait for pending requests to complete across all BlockDriverStates
+ *
+ * This function does not flush data to disk, use bdrv_flush_all() for that
+ * after calling this function.
+ */
+void bdrv_drain_all(void)
+{
+    bdrv_drain_request(NULL);
+}
+
 /* make a BlockDriverState anonymous by removing from bdrv_state list.
    Also, NULL terminate the device_name to prevent double remove */
 void bdrv_make_anon(BlockDriverState *bs)
diff --git a/block_int.h b/block_int.h
index 7946cf6..1311288 100644
--- a/block_int.h
+++ b/block_int.h
@@ -323,6 +323,7 @@ void qemu_aio_release(void *p);
 
 void bdrv_set_io_limits(BlockDriverState *bs,
                         BlockIOLimit *io_limits);
+void bdrv_drain_request(BlockDriverState *bs);
 
 #ifdef _WIN32
 int is_windows_drive(const char *filename);
-- 
1.7.6