qed: convert to .bdrv_co_is_allocated()

The bdrv_qed_is_allocated() function is a synchronous wrapper around
qed_find_cluster(), which performs the cluster lookup.  In order to
convert the synchronous function to a coroutine function we yield
instead of using qemu_aio_wait().  Note that QED's cache is already safe
for parallel requests so no locking is needed.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qed.c

@@ -661,6 +661,7 @@ static int bdrv_qed_create(const char *filename, QEMUOptionParameter *options)
 }
 
 typedef struct {
+    Coroutine *co;
     int is_allocated;
     int *pnum;
 } QEDIsAllocatedCB;
@@ -670,9 +671,13 @@ static void qed_is_allocated_cb(void *opaque, int ret, uint64_t offset, size_t l
     QEDIsAllocatedCB *cb = opaque;
     *cb->pnum = len / BDRV_SECTOR_SIZE;
     cb->is_allocated = (ret == QED_CLUSTER_FOUND || ret == QED_CLUSTER_ZERO);
+    if (cb->co) {
+        qemu_coroutine_enter(cb->co, NULL);
+    }
 }
 
-static int bdrv_qed_is_allocated(BlockDriverState *bs, int64_t sector_num,
+static int coroutine_fn bdrv_qed_co_is_allocated(BlockDriverState *bs,
+                                                 int64_t sector_num,
                                                  int nb_sectors, int *pnum)
 {
     BDRVQEDState *s = bs->opaque;
@@ -686,8 +691,10 @@ static int bdrv_qed_is_allocated(BlockDriverState *bs, int64_t sector_num,
 
     qed_find_cluster(s, &request, pos, len, qed_is_allocated_cb, &cb);
 
+    /* Now sleep if the callback wasn't invoked immediately */
     while (cb.is_allocated == -1) {
-        qemu_aio_wait();
+        cb.co = qemu_coroutine_self();
+        qemu_coroutine_yield();
     }
 
     qed_unref_l2_cache_entry(request.l2_table);
@@ -1485,7 +1492,7 @@ static BlockDriver bdrv_qed = {
     .bdrv_open                = bdrv_qed_open,
     .bdrv_close               = bdrv_qed_close,
     .bdrv_create              = bdrv_qed_create,
-    .bdrv_is_allocated        = bdrv_qed_is_allocated,
+    .bdrv_co_is_allocated     = bdrv_qed_co_is_allocated,
     .bdrv_make_empty          = bdrv_qed_make_empty,
     .bdrv_aio_readv           = bdrv_qed_aio_readv,
     .bdrv_aio_writev          = bdrv_qed_aio_writev,