Add retry_request_cb in BlockDevOps to do device specific retry action.
Backend's timer would be registered only when the backend is set 'retry'
on errors and the device supports retry action.

Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Signed-off-by: Ying Fang <fangying1@huawei.com>
---
 block/block-backend.c          | 8 ++++++++
 include/sysemu/block-backend.h | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/block/block-backend.c b/block/block-backend.c
index fe775ea298..bca7c581ee 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -995,6 +995,14 @@ void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
     blk->dev_ops = ops;
     blk->dev_opaque = opaque;
 
+    if ((blk->on_read_error == BLOCKDEV_ON_ERROR_RETRY ||
+         blk->on_write_error == BLOCKDEV_ON_ERROR_RETRY) &&
+        ops->retry_request_cb) {
+        blk->retry_timer = aio_timer_new(blk->ctx, QEMU_CLOCK_REALTIME,
+                                         SCALE_MS, ops->retry_request_cb,
+                                         opaque);
+    }
+
     /* Are we currently quiesced? Should we enforce this right now? */
     if (blk->quiesce_counter && ops->drained_begin) {
         ops->drained_begin(opaque);
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 8203d7f6f9..b31144aca9 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -66,6 +66,10 @@ typedef struct BlockDevOps {
      * Runs when the backend's last drain request ends.
      */
     void (*drained_end)(void *opaque);
+    /*
+     * Runs when retrying failed requests.
+     */
+    void (*retry_request_cb)(void *opaque);
 } BlockDevOps;
 
 /* This struct is embedded in (the private) BlockBackend struct and contains
-- 
2.28.0