Revert "io_uring: Add support for napi_busy_poll"

This reverts commit adc8682.

There's some discussion on the API not being as good as it can be.
Rather than ship something and be stuck with it forever, let's revert
the NAPI support for now and work on getting something sorted out
for the next kernel release instead.

Link: https://lore.kernel.org/io-uring/b7bbc124-8502-0ee9-d4c8-7c41b4487264@kernel.dk/
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

fs/io_uring.c

@@ -63,7 +63,6 @@
 #include <net/sock.h>
 #include <net/af_unix.h>
 #include <net/scm.h>
-#include <net/busy_poll.h>
 #include <linux/anon_inodes.h>
 #include <linux/sched/mm.h>
 #include <linux/uaccess.h>
@@ -411,11 +410,6 @@ struct io_ring_ctx {
 	struct list_head	sqd_list;
 
 	unsigned long		check_cq_overflow;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	/* used to track busy poll napi_id */
-	struct list_head	napi_list;
-	spinlock_t		napi_lock;	/* napi_list lock */
-#endif
 
 	struct {
 		unsigned		cached_cq_tail;
@@ -1569,10 +1563,6 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	INIT_WQ_LIST(&ctx->locked_free_list);
 	INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
 	INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	INIT_LIST_HEAD(&ctx->napi_list);
-	spin_lock_init(&ctx->napi_lock);
-#endif
 	return ctx;
 err:
 	kfree(ctx->dummy_ubuf);
@@ -5730,108 +5720,6 @@ IO_NETOP_FN(send);
 IO_NETOP_FN(recv);
 #endif /* CONFIG_NET */
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-
-#define NAPI_TIMEOUT			(60 * SEC_CONVERSION)
-
-struct napi_entry {
-	struct list_head	list;
-	unsigned int		napi_id;
-	unsigned long		timeout;
-};
-
-/*
- * Add busy poll NAPI ID from sk.
- */
-static void io_add_napi(struct file *file, struct io_ring_ctx *ctx)
-{
-	unsigned int napi_id;
-	struct socket *sock;
-	struct sock *sk;
-	struct napi_entry *ne;
-
-	if (!net_busy_loop_on())
-		return;
-
-	sock = sock_from_file(file);
-	if (!sock)
-		return;
-
-	sk = sock->sk;
-	if (!sk)
-		return;
-
-	napi_id = READ_ONCE(sk->sk_napi_id);
-
-	/* Non-NAPI IDs can be rejected */
-	if (napi_id < MIN_NAPI_ID)
-		return;
-
-	spin_lock(&ctx->napi_lock);
-	list_for_each_entry(ne, &ctx->napi_list, list) {
-		if (ne->napi_id == napi_id) {
-			ne->timeout = jiffies + NAPI_TIMEOUT;
-			goto out;
-		}
-	}
-
-	ne = kmalloc(sizeof(*ne), GFP_NOWAIT);
-	if (!ne)
-		goto out;
-
-	ne->napi_id = napi_id;
-	ne->timeout = jiffies + NAPI_TIMEOUT;
-	list_add_tail(&ne->list, &ctx->napi_list);
-out:
-	spin_unlock(&ctx->napi_lock);
-}
-
-static inline void io_check_napi_entry_timeout(struct napi_entry *ne)
-{
-	if (time_after(jiffies, ne->timeout)) {
-		list_del(&ne->list);
-		kfree(ne);
-	}
-}
-
-/*
- * Busy poll if globally on and supporting sockets found
- */
-static bool io_napi_busy_loop(struct list_head *napi_list)
-{
-	struct napi_entry *ne, *n;
-
-	list_for_each_entry_safe(ne, n, napi_list, list) {
-		napi_busy_loop(ne->napi_id, NULL, NULL, true,
-			       BUSY_POLL_BUDGET);
-		io_check_napi_entry_timeout(ne);
-	}
-	return !list_empty(napi_list);
-}
-
-static void io_free_napi_list(struct io_ring_ctx *ctx)
-{
-	spin_lock(&ctx->napi_lock);
-	while (!list_empty(&ctx->napi_list)) {
-		struct napi_entry *ne =
-			list_first_entry(&ctx->napi_list, struct napi_entry,
-					 list);
-
-		list_del(&ne->list);
-		kfree(ne);
-	}
-	spin_unlock(&ctx->napi_lock);
-}
-#else
-static inline void io_add_napi(struct file *file, struct io_ring_ctx *ctx)
-{
-}
-
-static inline void io_free_napi_list(struct io_ring_ctx *ctx)
-{
-}
-#endif /* CONFIG_NET_RX_BUSY_POLL */
-
 struct io_poll_table {
 	struct poll_table_struct pt;
 	struct io_kiocb *req;
@@ -5986,7 +5874,6 @@ static int io_poll_check_events(struct io_kiocb *req, bool locked)
 			if (unlikely(!filled))
 				return -ECANCELED;
 			io_cqring_ev_posted(ctx);
-			io_add_napi(req->file, ctx);
 		} else if (req->result) {
 			return 0;
 		}
@@ -6237,7 +6124,6 @@ static int __io_arm_poll_handler(struct io_kiocb *req,
 		__io_poll_execute(req, mask, poll->events);
 		return 0;
 	}
-	io_add_napi(req->file, req->ctx);
 
 	/*
 	 * Release ownership. If someone tried to queue a tw while it was
@@ -8028,13 +7914,7 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
 		    !(ctx->flags & IORING_SETUP_R_DISABLED))
 			ret = io_submit_sqes(ctx, to_submit);
 		mutex_unlock(&ctx->uring_lock);
-#ifdef CONFIG_NET_RX_BUSY_POLL
-		spin_lock(&ctx->napi_lock);
-		if (!list_empty(&ctx->napi_list) &&
-		    io_napi_busy_loop(&ctx->napi_list))
-			++ret;
-		spin_unlock(&ctx->napi_lock);
-#endif
+
 		if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
 			wake_up(&ctx->sqo_sq_wait);
 		if (creds)
@@ -8172,9 +8052,6 @@ struct io_wait_queue {
 	struct io_ring_ctx *ctx;
 	unsigned cq_tail;
 	unsigned nr_timeouts;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	unsigned busy_poll_to;
-#endif
 };
 
 static inline bool io_should_wake(struct io_wait_queue *iowq)
@@ -8236,87 +8113,6 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx,
 	return 1;
 }
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-static void io_adjust_busy_loop_timeout(struct timespec64 *ts,
-					struct io_wait_queue *iowq)
-{
-	unsigned busy_poll_to = READ_ONCE(sysctl_net_busy_poll);
-	struct timespec64 pollto = ns_to_timespec64(1000 * (s64)busy_poll_to);
-
-	if (timespec64_compare(ts, &pollto) > 0) {
-		*ts = timespec64_sub(*ts, pollto);
-		iowq->busy_poll_to = busy_poll_to;
-	} else {
-		u64 to = timespec64_to_ns(ts);
-
-		do_div(to, 1000);
-		iowq->busy_poll_to = to;
-		ts->tv_sec = 0;
-		ts->tv_nsec = 0;
-	}
-}
-
-static inline bool io_busy_loop_timeout(unsigned long start_time,
-					unsigned long bp_usec)
-{
-	if (bp_usec) {
-		unsigned long end_time = start_time + bp_usec;
-		unsigned long now = busy_loop_current_time();
-
-		return time_after(now, end_time);
-	}
-	return true;
-}
-
-static bool io_busy_loop_end(void *p, unsigned long start_time)
-{
-	struct io_wait_queue *iowq = p;
-
-	return signal_pending(current) ||
-	       io_should_wake(iowq) ||
-	       io_busy_loop_timeout(start_time, iowq->busy_poll_to);
-}
-
-static void io_blocking_napi_busy_loop(struct list_head *napi_list,
-				       struct io_wait_queue *iowq)
-{
-	unsigned long start_time =
-		list_is_singular(napi_list) ? 0 :
-		busy_loop_current_time();
-
-	do {
-		if (list_is_singular(napi_list)) {
-			struct napi_entry *ne =
-				list_first_entry(napi_list,
-						 struct napi_entry, list);
-
-			napi_busy_loop(ne->napi_id, io_busy_loop_end, iowq,
-				       true, BUSY_POLL_BUDGET);
-			io_check_napi_entry_timeout(ne);
-			break;
-		}
-	} while (io_napi_busy_loop(napi_list) &&
-		 !io_busy_loop_end(iowq, start_time));
-}
-
-static void io_putback_napi_list(struct io_ring_ctx *ctx,
-				 struct list_head *napi_list)
-{
-	struct napi_entry *cne, *lne;
-
-	spin_lock(&ctx->napi_lock);
-	list_for_each_entry(cne, &ctx->napi_list, list)
-		list_for_each_entry(lne, napi_list, list)
-			if (cne->napi_id == lne->napi_id) {
-				list_del(&lne->list);
-				kfree(lne);
-				break;
-			}
-	list_splice(napi_list, &ctx->napi_list);
-	spin_unlock(&ctx->napi_lock);
-}
-#endif /* CONFIG_NET_RX_BUSY_POLL */
-
 /*
  * Wait until events become available, if we don't already have some. The
  * application must reap them itself, as they reside on the shared cq ring.
@@ -8329,9 +8125,6 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 	struct io_rings *rings = ctx->rings;
 	ktime_t timeout = KTIME_MAX;
 	int ret;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	LIST_HEAD(local_napi_list);
-#endif
 
 	do {
 		io_cqring_overflow_flush(ctx);
@@ -8354,29 +8147,13 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 			return ret;
 	}
 
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	iowq.busy_poll_to = 0;
-	if (!(ctx->flags & IORING_SETUP_SQPOLL)) {
-		spin_lock(&ctx->napi_lock);
-		list_splice_init(&ctx->napi_list, &local_napi_list);
-		spin_unlock(&ctx->napi_lock);
-	}
-#endif
 	if (uts) {
 		struct timespec64 ts;
 
 		if (get_timespec64(&ts, uts))
 			return -EFAULT;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-		if (!list_empty(&local_napi_list))
-			io_adjust_busy_loop_timeout(&ts, &iowq);
-#endif
 		timeout = ktime_add_ns(timespec64_to_ktime(ts), ktime_get_ns());
 	}
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	else if (!list_empty(&local_napi_list))
-		iowq.busy_poll_to = READ_ONCE(sysctl_net_busy_poll);
-#endif
 
 	init_waitqueue_func_entry(&iowq.wq, io_wake_function);
 	iowq.wq.private = current;
@@ -8386,12 +8163,6 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
 	iowq.cq_tail = READ_ONCE(ctx->rings->cq.head) + min_events;
 
 	trace_io_uring_cqring_wait(ctx, min_events);
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	if (iowq.busy_poll_to)
-		io_blocking_napi_busy_loop(&local_napi_list, &iowq);
-	if (!list_empty(&local_napi_list))
-		io_putback_napi_list(ctx, &local_napi_list);
-#endif
 	do {
 		/* if we can't even flush overflow, don't wait for more */
 		if (!io_cqring_overflow_flush(ctx)) {
@@ -10176,7 +9947,6 @@ static __cold void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	io_req_caches_free(ctx);
 	if (ctx->hash_map)
 		io_wq_put_hash(ctx->hash_map);
-	io_free_napi_list(ctx);
 	kfree(ctx->cancel_hash);
 	kfree(ctx->dummy_ubuf);
 	kfree(ctx->io_buffers);