aio: remove aio_context_use_g_source()

There is no need for aio_context_use_g_source() now that epoll(7) and
io_uring(7) file descriptor monitoring works with the glib event loop.
AioContext doesn't need to be notified that GSource is being used.

On hosts with io_uring support this now enables fdmon-io_uring.c by
default, replacing fdmon-poll.c and fdmon-epoll.c. In other words, the
event loop will use io_uring!

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20251104022933.618123-8-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/block/aio.h

@@ -728,9 +728,6 @@ void aio_context_setup(AioContext *ctx);
  */
 void aio_context_destroy(AioContext *ctx);
 
-/* Used internally, do not call outside AioContext code */
-void aio_context_use_g_source(AioContext *ctx);
-
 /**
  * aio_context_set_poll_params:
  * @ctx: the aio context

util/aio-posix.c

@@ -743,18 +743,6 @@ void aio_context_destroy(AioContext *ctx)
     aio_free_deleted_handlers(ctx);
 }
 
-void aio_context_use_g_source(AioContext *ctx)
-{
-    /*
-     * Disable io_uring when the glib main loop is used because it doesn't
-     * support mixed glib/aio_poll() usage. It relies on aio_poll() being
-     * called regularly so that changes to the monitored file descriptors are
-     * submitted, otherwise a list of pending fd handlers builds up.
-     */
-    fdmon_io_uring_destroy(ctx);
-    aio_free_deleted_handlers(ctx);
-}
-
 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
                                  int64_t grow, int64_t shrink, Error **errp)
 {

util/aio-win32.c

@@ -427,10 +427,6 @@ void aio_context_destroy(AioContext *ctx)
 {
 }
 
-void aio_context_use_g_source(AioContext *ctx)
-{
-}
-
 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
                                  int64_t grow, int64_t shrink, Error **errp)
 {

util/async.c

@@ -434,7 +434,6 @@ static GSourceFuncs aio_source_funcs = {
 
 GSource *aio_get_g_source(AioContext *ctx)
 {
-    aio_context_use_g_source(ctx);
     g_source_ref(&ctx->source);
     return &ctx->source;
 }