block/io_uring: revert "Use io_uring_register_ring_fd() to skip fd operations"

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1193

The commit "Use io_uring_register_ring_fd() to skip fd operations" broke
when booting a guest with iothread and io_uring. That is because the
io_uring_register_ring_fd() call is made from the main thread instead of
IOThread where io_uring_submit() is called. It can not be guaranteed
to register the ring fd in the correct thread or unregister the same ring
fd if the IOThread is disabled. This optimization is not critical so we
will revert previous commit.

This reverts commit e2848bc574fe2715c694bf8fe9a1ba7f78a1125a
and 77e3f038af1764983087e3551a0fde9951952c4d.

Cc: qemu-stable@nongnu.org
Signed-off-by: Sam Li <faithilikerun@gmail.com>
Message-Id: <20220924144815.5591-1-faithilikerun@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Tested-by: Dario Faggioli <dfaggioli@suse.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

diff --git a/block/io_uring.c b/block/io_uring.c
index a1760152e0581c279e22b1c3a8d06f91851419df..973e15d87693370dd3388f5119622ea2b525d30e 100644 (file)
--- a/block/io_uring.c
+++ b/block/io_uring.c
@@ -11,7 +11,6 @@
 #include "qemu/osdep.h"
 #include <liburing.h>
 #include "block/aio.h"
-#include "qemu/error-report.h"
 #include "qemu/queue.h"
 #include "block/block.h"
 #include "block/raw-aio.h"
@@ -19,7 +18,6 @@
 #include "qapi/error.h"
 #include "trace.h"
 
-
 /* io_uring ring size */
 #define MAX_ENTRIES 128
 
@@ -432,17 +430,8 @@ LuringState *luring_init(Error **errp)
     }
 
     ioq_init(&s->io_q);
-#ifdef CONFIG_LIBURING_REGISTER_RING_FD
-    if (io_uring_register_ring_fd(&s->ring) < 0) {
-        /*
-         * Only warn about this error: we will fallback to the non-optimized
-         * io_uring operations.
-         */
-        warn_report("failed to register linux io_uring ring file descriptor");
-    }
-#endif
-
     return s;
+
 }
 
 void luring_cleanup(LuringState *s)

diff --git a/meson.build b/meson.build
index b686dfef7567b0c691d1ba6a612b00ddda1d6ced..44c1f92697a21d803c13e2dae8da1025fd87e90f 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -1839,7 +1839,6 @@ config_host_data.set('CONFIG_LIBNFS', libnfs.found())
 config_host_data.set('CONFIG_LIBSSH', libssh.found())
 config_host_data.set('CONFIG_LINUX_AIO', libaio.found())
 config_host_data.set('CONFIG_LINUX_IO_URING', linux_io_uring.found())
-config_host_data.set('CONFIG_LIBURING_REGISTER_RING_FD', cc.has_function('io_uring_register_ring_fd', prefix: '#include <liburing.h>', dependencies:linux_io_uring))
 config_host_data.set('CONFIG_LIBPMEM', libpmem.found())
 config_host_data.set('CONFIG_NUMA', numa.found())
 config_host_data.set('CONFIG_OPENGL', opengl.found())