1 files changed, 334 insertions, 0 deletions
diff --git a/io_uring/futex.c b/io_uring/futex.c
new file mode 100644
index 000000000000..11bfff5a80df
--- /dev/null
+++ b/io_uring/futex.c
@@ -0,0 +1,334 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "../kernel/futex/futex.h"
+#include "io_uring.h"
+#include "alloc_cache.h"
+#include "futex.h"
+
+struct io_futex {
+	struct file	*file;
+	void __user	*uaddr;
+	unsigned long	futex_val;
+	unsigned long	futex_mask;
+	u32		futex_flags;
+	unsigned int	futex_nr;
+	bool		futexv_unqueued;
+};
+
+struct io_futex_data {
+	struct futex_q	q;
+	struct io_kiocb	*req;
+};
+
+struct io_futexv_data {
+	unsigned long		owned;
+	struct futex_vector	futexv[];
+};
+
+#define IO_FUTEX_ALLOC_CACHE_MAX	32
+
+bool io_futex_cache_init(struct io_ring_ctx *ctx)
+{
+	return io_alloc_cache_init(&ctx->futex_cache, IO_FUTEX_ALLOC_CACHE_MAX,
+				sizeof(struct io_futex_data), 0);
+}
+
+void io_futex_cache_free(struct io_ring_ctx *ctx)
+{
+	io_alloc_cache_free(&ctx->futex_cache, kfree);
+}
+
+static void __io_futex_complete(struct io_tw_req tw_req, io_tw_token_t tw)
+{
+	hlist_del_init(&tw_req.req->hash_node);
+	io_req_task_complete(tw_req, tw);
+}
+
+static void io_futex_complete(struct io_tw_req tw_req, io_tw_token_t tw)
+{
+	struct io_kiocb *req = tw_req.req;
+	struct io_ring_ctx *ctx = req->ctx;
+
+	io_tw_lock(ctx, tw);
+	io_cache_free(&ctx->futex_cache, req->async_data);
+	io_req_async_data_clear(req, 0);
+	__io_futex_complete(tw_req, tw);
+}
+
+static void io_futexv_complete(struct io_tw_req tw_req, io_tw_token_t tw)
+{
+	struct io_kiocb *req = tw_req.req;
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	struct io_futexv_data *ifd = req->async_data;
+
+	io_tw_lock(req->ctx, tw);
+
+	if (!iof->futexv_unqueued) {
+		int res;
+
+		res = futex_unqueue_multiple(ifd->futexv, iof->futex_nr);
+		if (res != -1)
+			io_req_set_res(req, res, 0);
+	}
+
+	io_req_async_data_free(req);
+	__io_futex_complete(tw_req, tw);
+}
+
+static bool io_futexv_claim(struct io_futexv_data *ifd)
+{
+	if (test_bit(0, &ifd->owned) || test_and_set_bit_lock(0, &ifd->owned))
+		return false;
+	return true;
+}
+
+static bool __io_futex_cancel(struct io_kiocb *req)
+{
+	/* futex wake already done or in progress */
+	if (req->opcode == IORING_OP_FUTEX_WAIT) {
+		struct io_futex_data *ifd = req->async_data;
+
+		if (!futex_unqueue(&ifd->q))
+			return false;
+		req->io_task_work.func = io_futex_complete;
+	} else {
+		struct io_futexv_data *ifd = req->async_data;
+
+		if (!io_futexv_claim(ifd))
+			return false;
+		req->io_task_work.func = io_futexv_complete;
+	}
+
+	hlist_del_init(&req->hash_node);
+	io_req_set_res(req, -ECANCELED, 0);
+	io_req_task_work_add(req);
+	return true;
+}
+
+int io_futex_cancel(struct io_ring_ctx *ctx, struct io_cancel_data *cd,
+		    unsigned int issue_flags)
+{
+	return io_cancel_remove(ctx, cd, issue_flags, &ctx->futex_list, __io_futex_cancel);
+}
+
+bool io_futex_remove_all(struct io_ring_ctx *ctx, struct io_uring_task *tctx,
+			 bool cancel_all)
+{
+	return io_cancel_remove_all(ctx, tctx, &ctx->futex_list, cancel_all, __io_futex_cancel);
+}
+
+int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	u32 flags;
+
+	if (unlikely(sqe->len || sqe->futex_flags || sqe->buf_index ||
+		     sqe->file_index))
+		return -EINVAL;
+
+	iof->uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	iof->futex_val = READ_ONCE(sqe->addr2);
+	iof->futex_mask = READ_ONCE(sqe->addr3);
+	flags = READ_ONCE(sqe->fd);
+
+	if (flags & ~FUTEX2_VALID_MASK)
+		return -EINVAL;
+
+	iof->futex_flags = futex2_to_flags(flags);
+	if (!futex_flags_valid(iof->futex_flags))
+		return -EINVAL;
+
+	if (!futex_validate_input(iof->futex_flags, iof->futex_val) ||
+	    !futex_validate_input(iof->futex_flags, iof->futex_mask))
+		return -EINVAL;
+
+	/* Mark as inflight, so file exit cancelation will find it */
+	io_req_track_inflight(req);
+	return 0;
+}
+
+static void io_futex_wakev_fn(struct wake_q_head *wake_q, struct futex_q *q)
+{
+	struct io_kiocb *req = q->wake_data;
+	struct io_futexv_data *ifd = req->async_data;
+
+	if (!io_futexv_claim(ifd))
+		return;
+	if (unlikely(!__futex_wake_mark(q)))
+		return;
+
+	io_req_set_res(req, 0, 0);
+	req->io_task_work.func = io_futexv_complete;
+	io_req_task_work_add(req);
+}
+
+int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	struct io_futexv_data *ifd;
+	int ret;
+
+	/* No flags or mask supported for waitv */
+	if (unlikely(sqe->fd || sqe->buf_index || sqe->file_index ||
+		     sqe->addr2 || sqe->futex_flags || sqe->addr3))
+		return -EINVAL;
+
+	iof->uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	iof->futex_nr = READ_ONCE(sqe->len);
+	if (!iof->futex_nr || iof->futex_nr > FUTEX_WAITV_MAX)
+		return -EINVAL;
+
+	ifd = kzalloc(struct_size_t(struct io_futexv_data, futexv, iof->futex_nr),
+			GFP_KERNEL);
+	if (!ifd)
+		return -ENOMEM;
+
+	ret = futex_parse_waitv(ifd->futexv, iof->uaddr, iof->futex_nr,
+				io_futex_wakev_fn, req);
+	if (ret) {
+		kfree(ifd);
+		return ret;
+	}
+
+	/* Mark as inflight, so file exit cancelation will find it */
+	io_req_track_inflight(req);
+	iof->futexv_unqueued = 0;
+	req->flags |= REQ_F_ASYNC_DATA;
+	req->async_data = ifd;
+	return 0;
+}
+
+static void io_futex_wake_fn(struct wake_q_head *wake_q, struct futex_q *q)
+{
+	struct io_futex_data *ifd = container_of(q, struct io_futex_data, q);
+	struct io_kiocb *req = ifd->req;
+
+	if (unlikely(!__futex_wake_mark(q)))
+		return;
+
+	io_req_set_res(req, 0, 0);
+	req->io_task_work.func = io_futex_complete;
+	io_req_task_work_add(req);
+}
+
+int io_futexv_wait(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	struct io_futexv_data *ifd = req->async_data;
+	struct io_ring_ctx *ctx = req->ctx;
+	int ret, woken = -1;
+
+	io_ring_submit_lock(ctx, issue_flags);
+
+	ret = futex_wait_multiple_setup(ifd->futexv, iof->futex_nr, &woken);
+
+	/*
+	 * Error case, ret is < 0. Mark the request as failed.
+	 */
+	if (unlikely(ret < 0)) {
+		io_ring_submit_unlock(ctx, issue_flags);
+		req_set_fail(req);
+		io_req_set_res(req, ret, 0);
+		io_req_async_data_free(req);
+		return IOU_COMPLETE;
+	}
+
+	/*
+	 * 0 return means that we successfully setup the waiters, and that
+	 * nobody triggered a wakeup while we were doing so. If the wakeup
+	 * happened post setup, the task_work will be run post this issue and
+	 * under the submission lock. 1 means We got woken while setting up,
+	 * let that side do the completion. Note that
+	 * futex_wait_multiple_setup() will have unqueued all the futexes in
+	 * this case. Mark us as having done that already, since this is
+	 * different from normal wakeup.
+	 */
+	if (!ret) {
+		/*
+		 * If futex_wait_multiple_setup() returns 0 for a
+		 * successful setup, then the task state will not be
+		 * runnable. This is fine for the sync syscall, as
+		 * it'll be blocking unless we already got one of the
+		 * futexes woken, but it obviously won't work for an
+		 * async invocation. Mark us runnable again.
+		 */
+		__set_current_state(TASK_RUNNING);
+		hlist_add_head(&req->hash_node, &ctx->futex_list);
+	} else {
+		iof->futexv_unqueued = 1;
+		if (woken != -1)
+			io_req_set_res(req, woken, 0);
+	}
+
+	io_ring_submit_unlock(ctx, issue_flags);
+	return IOU_ISSUE_SKIP_COMPLETE;
+}
+
+int io_futex_wait(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	struct io_ring_ctx *ctx = req->ctx;
+	struct io_futex_data *ifd = NULL;
+	int ret;
+
+	if (!iof->futex_mask) {
+		ret = -EINVAL;
+		goto done;
+	}
+
+	io_ring_submit_lock(ctx, issue_flags);
+	ifd = io_cache_alloc(&ctx->futex_cache, GFP_NOWAIT);
+	if (!ifd) {
+		ret = -ENOMEM;
+		goto done_unlock;
+	}
+
+	req->flags |= REQ_F_ASYNC_DATA;
+	req->async_data = ifd;
+	ifd->q = futex_q_init;
+	ifd->q.bitset = iof->futex_mask;
+	ifd->q.wake = io_futex_wake_fn;
+	ifd->req = req;
+
+	ret = futex_wait_setup(iof->uaddr, iof->futex_val, iof->futex_flags,
+			       &ifd->q, NULL, NULL);
+	if (!ret) {
+		hlist_add_head(&req->hash_node, &ctx->futex_list);
+		io_ring_submit_unlock(ctx, issue_flags);
+
+		return IOU_ISSUE_SKIP_COMPLETE;
+	}
+
+done_unlock:
+	io_ring_submit_unlock(ctx, issue_flags);
+done:
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	io_req_async_data_free(req);
+	return IOU_COMPLETE;
+}
+
+int io_futex_wake(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
+	int ret;
+
+	/*
+	 * Strict flags - ensure that waking 0 futexes yields a 0 result.
+	 * See commit 43adf8449510 ("futex: FLAGS_STRICT") for details.
+	 */
+	ret = futex_wake(iof->uaddr, FLAGS_STRICT | iof->futex_flags,
+			 iof->futex_val, iof->futex_mask);
+	if (ret < 0)
+		req_set_fail(req);
+	io_req_set_res(req, ret, 0);
+	return IOU_COMPLETE;
+}