[PATCH 1/3] aio-posix: treat io_uring setup failure as fatal

[Stefan Hajnoczi <stefanha@redhat.com>]

In the early days of io_uring it was possible for io_uring_setup(2) to
fail due to exhausting RLIMIT_MEMLOCK. QEMU's solution was to fall back
to epoll(7) or ppoll(2) when io_uring could not be used in an
AioContext.

Nowadays io_uring memory is accounted differently so io_uring_setup(2)
won't fail. Treat failure as a fatal error. Keep it simple: io_uring is
available if and only if CONFIG_LINUX_IO_URING is defined.

Upcoming features that rely on io_uring won't need to handle the case
where a subset of AioContexts lacks io_uring. This will simplify the
aio_add_sqe() API introduced in the next commit.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 util/fdmon-io_uring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/util/fdmon-io_uring.c b/util/fdmon-io_uring.c
index 2092d08d24..18b33a0370 100644
--- a/util/fdmon-io_uring.c
+++ b/util/fdmon-io_uring.c
@@ -45,6 +45,7 @@
 
 #include "qemu/osdep.h"
 #include <poll.h>
+#include "qemu/error-report.h"
 #include "qemu/rcu_queue.h"
 #include "aio-posix.h"
 
@@ -369,7 +370,8 @@ bool fdmon_io_uring_setup(AioContext *ctx)
 
     ret = io_uring_queue_init(FDMON_IO_URING_ENTRIES, &ctx->fdmon_io_uring, 0);
     if (ret != 0) {
-        return false;
+        error_report("failed to initialize io_uring: %s", strerror(-ret));
+        exit(EXIT_FAILURE);
     }
 
     QSLIST_INIT(&ctx->submit_list);
-- 
2.49.0