io_uring: temporarily disable registered waits

Disable wait argument registration as it'll be replaced with a more
generic feature. We'll still need IORING_ENTER_EXT_ARG_REG parsing
in a few commits so leave it be.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/70b1d1d218c41ba77a76d1789c8641dab0b0563e.1731689588.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

include/linux/io_uring_types.h

@@ -330,14 +330,6 @@ struct io_ring_ctx {
 		atomic_t		cq_wait_nr;
 		atomic_t		cq_timeouts;
 		struct wait_queue_head	cq_wait;
-
-		/*
-		 * If registered with IORING_REGISTER_CQWAIT_REG, a single
-		 * page holds N entries, mapped in cq_wait_arg. cq_wait_index
-		 * is the maximum allowable index.
-		 */
-		struct io_uring_reg_wait	*cq_wait_arg;
-		unsigned char			cq_wait_index;
 	} ____cacheline_aligned_in_smp;
 
 	/* timeouts */
@@ -431,8 +423,6 @@ struct io_ring_ctx {
 	unsigned short			n_sqe_pages;
 	struct page			**ring_pages;
 	struct page			**sqe_pages;
-
-	struct page			**cq_wait_page;
 };
 
 struct io_tw_state {

include/uapi/linux/io_uring.h

@@ -627,9 +627,6 @@ enum io_uring_register_op {
 	/* resize CQ ring */
 	IORING_REGISTER_RESIZE_RINGS		= 33,
 
-	/* register fixed io_uring_reg_wait arguments */
-	IORING_REGISTER_CQWAIT_REG		= 34,
-
 	/* this goes last */
 	IORING_REGISTER_LAST,
 

io_uring/io_uring.c

@@ -2709,7 +2709,6 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	io_alloc_cache_free(&ctx->msg_cache, io_msg_cache_free);
 	io_futex_cache_free(ctx);
 	io_destroy_buffers(ctx);
-	io_unregister_cqwait_reg(ctx);
 	mutex_unlock(&ctx->uring_lock);
 	if (ctx->sq_creds)
 		put_cred(ctx->sq_creds);
@@ -3195,15 +3194,6 @@ void __io_uring_cancel(bool cancel_all)
 static struct io_uring_reg_wait *io_get_ext_arg_reg(struct io_ring_ctx *ctx,
 			const struct io_uring_getevents_arg __user *uarg)
 {
-	struct io_uring_reg_wait *arg = READ_ONCE(ctx->cq_wait_arg);
-
-	if (arg) {
-		unsigned int index = (unsigned int) (uintptr_t) uarg;
-
-		if (index <= ctx->cq_wait_index)
-			return arg + index;
-	}
-
 	return ERR_PTR(-EFAULT);
 }
 

io_uring/register.c

@@ -570,82 +570,6 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	return ret;
 }
 
-void io_unregister_cqwait_reg(struct io_ring_ctx *ctx)
-{
-	unsigned short npages = 1;
-
-	if (!ctx->cq_wait_page)
-		return;
-
-	io_pages_unmap(ctx->cq_wait_arg, &ctx->cq_wait_page, &npages, true);
-	ctx->cq_wait_arg = NULL;
-	if (ctx->user)
-		__io_unaccount_mem(ctx->user, 1);
-}
-
-/*
- * Register a page holding N entries of struct io_uring_reg_wait, which can
- * be used via io_uring_enter(2) if IORING_GETEVENTS_EXT_ARG_REG is set.
- * If that is set with IORING_GETEVENTS_EXT_ARG, then instead of passing
- * in a pointer for a struct io_uring_getevents_arg, an index into this
- * registered array is passed, avoiding two (arg + timeout) copies per
- * invocation.
- */
-static int io_register_cqwait_reg(struct io_ring_ctx *ctx, void __user *uarg)
-{
-	struct io_uring_cqwait_reg_arg arg;
-	struct io_uring_reg_wait *reg;
-	struct page **pages;
-	unsigned long len;
-	int nr_pages, poff;
-	int ret;
-
-	if (ctx->cq_wait_page || ctx->cq_wait_arg)
-		return -EBUSY;
-	if (copy_from_user(&arg, uarg, sizeof(arg)))
-		return -EFAULT;
-	if (!arg.nr_entries || arg.flags)
-		return -EINVAL;
-	if (arg.struct_size != sizeof(*reg))
-		return -EINVAL;
-	if (check_mul_overflow(arg.struct_size, arg.nr_entries, &len))
-		return -EOVERFLOW;
-	if (len > PAGE_SIZE)
-		return -EINVAL;
-	/* offset + len must fit within a page, and must be reg_wait aligned */
-	poff = arg.user_addr & ~PAGE_MASK;
-	if (len + poff > PAGE_SIZE)
-		return -EINVAL;
-	if (poff % arg.struct_size)
-		return -EINVAL;
-
-	pages = io_pin_pages(arg.user_addr, len, &nr_pages);
-	if (IS_ERR(pages))
-		return PTR_ERR(pages);
-	ret = -EINVAL;
-	if (nr_pages != 1)
-		goto out_free;
-	if (ctx->user) {
-		ret = __io_account_mem(ctx->user, 1);
-		if (ret)
-			goto out_free;
-	}
-
-	reg = vmap(pages, 1, VM_MAP, PAGE_KERNEL);
-	if (reg) {
-		ctx->cq_wait_index = arg.nr_entries - 1;
-		WRITE_ONCE(ctx->cq_wait_page, pages);
-		WRITE_ONCE(ctx->cq_wait_arg, (void *) reg + poff);
-		return 0;
-	}
-	ret = -ENOMEM;
-	if (ctx->user)
-		__io_unaccount_mem(ctx->user, 1);
-out_free:
-	io_pages_free(&pages, nr_pages);
-	return ret;
-}
-
 static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			       void __user *arg, unsigned nr_args)
 	__releases(ctx->uring_lock)
@@ -840,12 +764,6 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			break;
 		ret = io_register_resize_rings(ctx, arg);
 		break;
-	case IORING_REGISTER_CQWAIT_REG:
-		ret = -EINVAL;
-		if (!arg || nr_args != 1)
-			break;
-		ret = io_register_cqwait_reg(ctx, arg);
-		break;
 	default:
 		ret = -EINVAL;
 		break;

io_uring/register.h

@@ -5,6 +5,5 @@
 int io_eventfd_unregister(struct io_ring_ctx *ctx);
 int io_unregister_personality(struct io_ring_ctx *ctx, unsigned id);
 struct file *io_uring_register_get_file(unsigned int fd, bool registered);
-void io_unregister_cqwait_reg(struct io_ring_ctx *ctx);
 
 #endif