[PATCH v13 12/15] block/io: refactor wait_serialising_requests

[Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>]

Split out do_wait_serialising_requests with additional possibility to
not actually wait but just check, that there is something to wait for.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
---
 block/io.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/block/io.c b/block/io.c
index f8c3596131..f5f7b7357c 100644
--- a/block/io.c
+++ b/block/io.c
@@ -786,12 +786,13 @@ void bdrv_dec_in_flight(BlockDriverState *bs)
     bdrv_wakeup(bs);
 }
 
-static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
+static bool coroutine_fn do_wait_serialising_requests(BdrvTrackedRequest *self,
+                                                      bool wait)
 {
     BlockDriverState *bs = self->bs;
     BdrvTrackedRequest *req;
     bool retry;
-    bool waited = false;
+    bool found = false;
 
     if (!atomic_read(&bs->serialising_in_flight)) {
         return false;
@@ -817,11 +818,13 @@ static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
                  * will wait for us as soon as it wakes up, then just go on
                  * (instead of producing a deadlock in the former case). */
                 if (!req->waiting_for) {
-                    self->waiting_for = req;
-                    qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
-                    self->waiting_for = NULL;
-                    retry = true;
-                    waited = true;
+                    found = true;
+                    if (wait) {
+                        self->waiting_for = req;
+                        qemu_co_queue_wait(&req->wait_queue, &bs->reqs_lock);
+                        self->waiting_for = NULL;
+                        retry = true;
+                    }
                     break;
                 }
             }
@@ -829,7 +832,12 @@ static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
         qemu_co_mutex_unlock(&bs->reqs_lock);
     } while (retry);
 
-    return waited;
+    return found;
+}
+
+static bool coroutine_fn wait_serialising_requests(BdrvTrackedRequest *self)
+{
+    return do_wait_serialising_requests(self, true);
 }
 
 static int bdrv_check_byte_request(BlockDriverState *bs, int64_t offset,
-- 
2.21.0