io_uring: add register/unregister napi function

This adds an api to register and unregister the napi for io-uring. If
the arg value is specified when unregistering, the current napi setting
for the busy poll timeout is copied into the user structure. If this is
not required, NULL can be passed as the arg value.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20230608163839.2891748-7-shr@devkernel.io
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index fb812f1b6bb5a8f96002b56dcd690a1c739492c1..7bd10201a02bc833a5f6334d45b03e50a17f0e1b 100644 (file)
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -571,6 +571,10 @@ enum {
        /* return status information for a buffer group */
        IORING_REGISTER_PBUF_STATUS             = 26,
 
+       /* set/clear busy poll settings */
+       IORING_REGISTER_NAPI                    = 27,
+       IORING_UNREGISTER_NAPI                  = 28,
+
        /* this goes last */
        IORING_REGISTER_LAST,
 
@@ -704,6 +708,14 @@ struct io_uring_buf_status {
        __u32   resv[8];
 };
 
+/* argument for IORING_(UN)REGISTER_NAPI */
+struct io_uring_napi {
+       __u32   busy_poll_to;
+       __u8    prefer_busy_poll;
+       __u8    pad[3];
+       __u64   resv;
+};
+
 /*
  * io_uring_restriction->opcode values
  */

diff --git a/io_uring/napi.c b/io_uring/napi.c
index 3e578df36cc510b0dee166ea126ca8991abae426..8ec016899539021cfa885375b63858447875dc87 100644 (file)
--- a/io_uring/napi.c
+++ b/io_uring/napi.c
@@ -207,6 +207,58 @@ void io_napi_free(struct io_ring_ctx *ctx)
        spin_unlock(&ctx->napi_lock);
 }
 
+/*
+ * io_napi_register() - Register napi with io-uring
+ * @ctx: pointer to io-uring context structure
+ * @arg: pointer to io_uring_napi structure
+ *
+ * Register napi in the io-uring context.
+ */
+int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
+{
+       const struct io_uring_napi curr = {
+               .busy_poll_to     = ctx->napi_busy_poll_to,
+               .prefer_busy_poll = ctx->napi_prefer_busy_poll
+       };
+       struct io_uring_napi napi;
+
+       if (copy_from_user(&napi, arg, sizeof(napi)))
+               return -EFAULT;
+       if (napi.pad[0] || napi.pad[1] || napi.pad[2] || napi.resv)
+               return -EINVAL;
+
+       WRITE_ONCE(ctx->napi_busy_poll_to, napi.busy_poll_to);
+       WRITE_ONCE(ctx->napi_prefer_busy_poll, !!napi.prefer_busy_poll);
+
+       if (copy_to_user(arg, &curr, sizeof(curr)))
+               return -EFAULT;
+
+       return 0;
+}
+
+/*
+ * io_napi_unregister() - Unregister napi with io-uring
+ * @ctx: pointer to io-uring context structure
+ * @arg: pointer to io_uring_napi structure
+ *
+ * Unregister napi. If arg has been specified copy the busy poll timeout and
+ * prefer busy poll setting to the passed in structure.
+ */
+int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
+{
+       const struct io_uring_napi curr = {
+               .busy_poll_to     = ctx->napi_busy_poll_to,
+               .prefer_busy_poll = ctx->napi_prefer_busy_poll
+       };
+
+       if (arg && copy_to_user(arg, &curr, sizeof(curr)))
+               return -EFAULT;
+
+       WRITE_ONCE(ctx->napi_busy_poll_to, 0);
+       WRITE_ONCE(ctx->napi_prefer_busy_poll, false);
+       return 0;
+}
+
 /*
  * __io_napi_adjust_timeout() - Add napi id to the busy poll list
  * @ctx: pointer to io-uring context structure

diff --git a/io_uring/napi.h b/io_uring/napi.h
index b6d6243fc7fe020495de4e895dd07cf5efa80dae..6fc0393d0dbef799fa6eded131876d6c5c29625b 100644 (file)
--- a/io_uring/napi.h
+++ b/io_uring/napi.h
@@ -12,6 +12,9 @@
 void io_napi_init(struct io_ring_ctx *ctx);
 void io_napi_free(struct io_ring_ctx *ctx);
 
+int io_register_napi(struct io_ring_ctx *ctx, void __user *arg);
+int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg);
+
 void __io_napi_add(struct io_ring_ctx *ctx, struct socket *sock);
 
 void __io_napi_adjust_timeout(struct io_ring_ctx *ctx,
@@ -68,6 +71,14 @@ static inline void io_napi_init(struct io_ring_ctx *ctx)
 static inline void io_napi_free(struct io_ring_ctx *ctx)
 {
 }
+static inline int io_register_napi(struct io_ring_ctx *ctx, void __user *arg)
+{
+       return -EOPNOTSUPP;
+}
+static inline int io_unregister_napi(struct io_ring_ctx *ctx, void __user *arg)
+{
+       return -EOPNOTSUPP;
+}
 static inline bool io_napi(struct io_ring_ctx *ctx)
 {
        return false;

diff --git a/io_uring/register.c b/io_uring/register.c
index 5e62c1208996542537c6aedf4d57506863165e10..99c37775f974c02a1c2f99d244af69a7c69c4ed3 100644 (file)
--- a/io_uring/register.c
+++ b/io_uring/register.c
@@ -26,6 +26,7 @@
 #include "register.h"
 #include "cancel.h"
 #include "kbuf.h"
+#include "napi.h"
 
 #define IORING_MAX_RESTRICTIONS        (IORING_RESTRICTION_LAST + \
                                 IORING_REGISTER_LAST + IORING_OP_LAST)
@@ -550,6 +551,18 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
                        break;
                ret = io_register_pbuf_status(ctx, arg);
                break;
+       case IORING_REGISTER_NAPI:
+               ret = -EINVAL;
+               if (!arg || nr_args != 1)
+                       break;
+               ret = io_register_napi(ctx, arg);
+               break;
+       case IORING_UNREGISTER_NAPI:
+               ret = -EINVAL;
+               if (nr_args != 1)
+                       break;
+               ret = io_unregister_napi(ctx, arg);
+               break;
        default:
                ret = -EINVAL;
                break;