io_uring: add support for eventfd notifications

Allow registration of an eventfd, which will trigger an event every
time a completion event happens for this io_uring instance.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 468f9da..2a46de5 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -241,6 +241,7 @@ struct io_ring_ctx {
                unsigned                cq_mask;
                struct wait_queue_head  cq_wait;
                struct fasync_struct    *cq_fasync;
+               struct eventfd_ctx      *cq_ev_fd;
        } ____cacheline_aligned_in_smp;
 
        /*
@@ -516,6 +517,8 @@ static void io_cqring_ev_posted(struct io_ring_ctx *ctx)
                wake_up(&ctx->wait);
        if (waitqueue_active(&ctx->sqo_wait))
                wake_up(&ctx->sqo_wait);
+       if (ctx->cq_ev_fd)
+               eventfd_signal(ctx->cq_ev_fd, 1);
 }
 
 static void io_cqring_add_event(struct io_ring_ctx *ctx, u64 user_data,
@@ -2757,6 +2760,38 @@ err:
        return ret;
 }
 
+static int io_eventfd_register(struct io_ring_ctx *ctx, void __user *arg)
+{
+       __s32 __user *fds = arg;
+       int fd;
+
+       if (ctx->cq_ev_fd)
+               return -EBUSY;
+
+       if (copy_from_user(&fd, fds, sizeof(*fds)))
+               return -EFAULT;
+
+       ctx->cq_ev_fd = eventfd_ctx_fdget(fd);
+       if (IS_ERR(ctx->cq_ev_fd)) {
+               int ret = PTR_ERR(ctx->cq_ev_fd);
+               ctx->cq_ev_fd = NULL;
+               return ret;
+       }
+
+       return 0;
+}
+
+static int io_eventfd_unregister(struct io_ring_ctx *ctx)
+{
+       if (ctx->cq_ev_fd) {
+               eventfd_ctx_put(ctx->cq_ev_fd);
+               ctx->cq_ev_fd = NULL;
+               return 0;
+       }
+
+       return -ENXIO;
+}
+
 static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 {
        io_finish_async(ctx);
@@ -2766,6 +2801,7 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
        io_iopoll_reap_events(ctx);
        io_sqe_buffer_unregister(ctx);
        io_sqe_files_unregister(ctx);
+       io_eventfd_unregister(ctx);
 
 #if defined(CONFIG_UNIX)
        if (ctx->ring_sock)
@@ -3179,6 +3215,18 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                        break;
                ret = io_sqe_files_unregister(ctx);
                break;
+       case IORING_REGISTER_EVENTFD:
+               ret = -EINVAL;
+               if (nr_args != 1)
+                       break;
+               ret = io_eventfd_register(ctx, arg);
+               break;
+       case IORING_UNREGISTER_EVENTFD:
+               ret = -EINVAL;
+               if (arg || nr_args)
+                       break;
+               ret = io_eventfd_unregister(ctx);
+               break;
        default:
                ret = -EINVAL;
                break;

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index e707a17..a0c4600 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -136,5 +136,7 @@ struct io_uring_params {
 #define IORING_UNREGISTER_BUFFERS      1
 #define IORING_REGISTER_FILES          2
 #define IORING_UNREGISTER_FILES                3
+#define IORING_REGISTER_EVENTFD                4
+#define IORING_UNREGISTER_EVENTFD      5
 
 #endif