block/io: Check for replay-enabled in bdrv_drain_all_begin()

In commit da0bd74434 we refactored bdrv_drain_all_begin() to pull out
the non-polling part into bdrv_drain_all_begin_nopoll().  This change
broke record-and-replay, because the "return early if replay enabled"
check is now in the sub-function bdrv_drain_all_begin_nopoll(), and
so it only causes us to return from that function, and not from the
calling bdrv_drain_all_begin().

Fix the regression by checking whether replay is enabled in both
functions.

The breakage and fix can be tested via 'make check-avocado': the
tests/avocado/reverse_debugging.py:ReverseDebugging_X86_64.test_x86_64_pc
tests/avocado/reverse_debugging.py:ReverseDebugging_AArch64.test_aarch64_virt
tests were both broken by this.

Fixes: da0bd74434 ("block: Factor out bdrv_drain_all_begin_nopoll()")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Fabiano Rosas <farosas@suse.de>
Message-id: 20221220174638.2156308-1-peter.maydell@linaro.org

block/io.c

@@ -506,6 +506,15 @@ void bdrv_drain_all_begin(void)
         return;
     }
 
+    /*
+     * bdrv queue is managed by record/replay,
+     * waiting for finishing the I/O requests may
+     * be infinite
+     */
+    if (replay_events_enabled()) {
+        return;
+    }
+
     bdrv_drain_all_begin_nopoll();
 
     /* Now poll the in-flight requests */