linux-aio: Handle io_submit() failure gracefully

It is generally not expected that io_submit() fails other than with
-EAGAIN, but corner cases like SELinux refusing I/O when permissions are
revoked are still possible. In this case, we shouldn't abort, but just
return an I/O error for the request.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1470741619-23231-1-git-send-email-kwolf@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block/linux-aio.c

@@ -221,7 +221,13 @@ static void ioq_submit(LinuxAioState *s)
             break;
         }
         if (ret < 0) {
-            abort();
+            /* Fail the first request, retry the rest */
+            aiocb = QSIMPLEQ_FIRST(&s->io_q.pending);
+            QSIMPLEQ_REMOVE_HEAD(&s->io_q.pending, next);
+            s->io_q.in_queue--;
+            aiocb->ret = ret;
+            qemu_laio_process_completion(aiocb);
+            continue;
         }
 
         s->io_q.in_flight += ret;