Merge tag 'for-linus-2019-10-26' of git://git.kernel.dk/linux-block

Pull block and io_uring fixes from Jens Axboe:
 "A bit bigger than usual at this point in time, mostly due to some good
  bug hunting work by Pavel that resulted in three io_uring fixes from
  him and two from me. Anyway, this pull request contains:

   - Revert of the submit-and-wait optimization for io_uring, it can't
     always be done safely. It depends on commands always making
     progress on their own, which isn't necessarily the case outside of
     strict file IO. (me)

   - Series of two patches from me and three from Pavel, fixing issues
     with shared data and sequencing for io_uring.

   - Lastly, two timeout sequence fixes for io_uring (zhangyi)

   - Two nbd patches fixing races (Josef)

   - libahci regulator_get_optional() fix (Mark)"

* tag 'for-linus-2019-10-26' of git://git.kernel.dk/linux-block:
  nbd: verify socket is supported during setup
  ata: libahci_platform: Fix regulator_get_optional() misuse
  nbd: handle racing with error'ed out commands
  nbd: protect cmd->status with cmd->lock
  io_uring: fix bad inflight accounting for SETUP_IOPOLL|SETUP_SQTHREAD
  io_uring: used cached copies of sq->dropped and cq->overflow
  io_uring: Fix race for sqes with userspace
  io_uring: Fix broken links with offloading
  io_uring: Fix corrupted user_data
  io_uring: correct timeout req sequence when inserting a new entry
  io_uring : correct timeout req sequence when waiting timeout
  io_uring: revert "io_uring: optimize submit_and_wait API"

1 files changed, 113 insertions, 94 deletions

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 67dbe0201e0d..a30c4f622cb3 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -197,6 +197,7 @@ struct io_ring_ctx {
 		unsigned		sq_entries;
 		unsigned		sq_mask;
 		unsigned		sq_thread_idle;
+		unsigned		cached_sq_dropped;
 		struct io_uring_sqe	*sq_sqes;
 
 		struct list_head	defer_list;
@@ -212,6 +213,7 @@ struct io_ring_ctx {
 
 	struct {
 		unsigned		cached_cq_tail;
+		atomic_t		cached_cq_overflow;
 		unsigned		cq_entries;
 		unsigned		cq_mask;
 		struct wait_queue_head	cq_wait;
@@ -420,7 +422,8 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 static inline bool __io_sequence_defer(struct io_ring_ctx *ctx,
 				       struct io_kiocb *req)
 {
-	return req->sequence != ctx->cached_cq_tail + ctx->rings->sq_dropped;
+	return req->sequence != ctx->cached_cq_tail + ctx->cached_sq_dropped
+					+ atomic_read(&ctx->cached_cq_overflow);
 }
 
 static inline bool io_sequence_defer(struct io_ring_ctx *ctx,
@@ -567,9 +570,8 @@ static void io_cqring_fill_event(struct io_ring_ctx *ctx, u64 ki_user_data,
 		WRITE_ONCE(cqe->res, res);
 		WRITE_ONCE(cqe->flags, 0);
 	} else {
-		unsigned overflow = READ_ONCE(ctx->rings->cq_overflow);
-
-		WRITE_ONCE(ctx->rings->cq_overflow, overflow + 1);
+		WRITE_ONCE(ctx->rings->cq_overflow,
+				atomic_inc_return(&ctx->cached_cq_overflow));
 	}
 }
 
@@ -735,6 +737,14 @@ static unsigned io_cqring_events(struct io_rings *rings)
 	return READ_ONCE(rings->cq.tail) - READ_ONCE(rings->cq.head);
 }
 
+static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
+{
+	struct io_rings *rings = ctx->rings;
+
+	/* make sure SQ entry isn't read before tail */
+	return smp_load_acquire(&rings->sq.tail) - ctx->cached_sq_head;
+}
+
 /*
  * Find and free completed poll iocbs
  */
@@ -864,19 +874,11 @@ static void io_iopoll_reap_events(struct io_ring_ctx *ctx)
 	mutex_unlock(&ctx->uring_lock);
 }
 
-static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
-			   long min)
+static int __io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
+			    long min)
 {
-	int iters, ret = 0;
-
-	/*
-	 * We disallow the app entering submit/complete with polling, but we
-	 * still need to lock the ring to prevent racing with polled issue
-	 * that got punted to a workqueue.
-	 */
-	mutex_lock(&ctx->uring_lock);
+	int iters = 0, ret = 0;
 
-	iters = 0;
 	do {
 		int tmin = 0;
 
@@ -912,6 +914,21 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
 		ret = 0;
 	} while (min && !*nr_events && !need_resched());
 
+	return ret;
+}
+
+static int io_iopoll_check(struct io_ring_ctx *ctx, unsigned *nr_events,
+			   long min)
+{
+	int ret;
+
+	/*
+	 * We disallow the app entering submit/complete with polling, but we
+	 * still need to lock the ring to prevent racing with polled issue
+	 * that got punted to a workqueue.
+	 */
+	mutex_lock(&ctx->uring_lock);
+	ret = __io_iopoll_check(ctx, nr_events, min);
 	mutex_unlock(&ctx->uring_lock);
 	return ret;
 }
@@ -1877,7 +1894,7 @@ static int io_poll_add(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
 {
 	struct io_ring_ctx *ctx;
-	struct io_kiocb *req;
+	struct io_kiocb *req, *prev;
 	unsigned long flags;
 
 	req = container_of(timer, struct io_kiocb, timeout.timer);
@@ -1885,6 +1902,15 @@ static enum hrtimer_restart io_timeout_fn(struct hrtimer *timer)
 	atomic_inc(&ctx->cq_timeouts);
 
 	spin_lock_irqsave(&ctx->completion_lock, flags);
+	/*
+	 * Adjust the reqs sequence before the current one because it
+	 * will consume a slot in the cq_ring and the the cq_tail pointer
+	 * will be increased, otherwise other timeout reqs may return in
+	 * advance without waiting for enough wait_nr.
+	 */
+	prev = req;
+	list_for_each_entry_continue_reverse(prev, &ctx->timeout_list, list)
+		prev->sequence++;
 	list_del(&req->list);
 
 	io_cqring_fill_event(ctx, req->user_data, -ETIME);
@@ -1903,6 +1929,7 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 	struct io_ring_ctx *ctx = req->ctx;
 	struct list_head *entry;
 	struct timespec64 ts;
+	unsigned span = 0;
 
 	if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
 		return -EINVAL;
@@ -1951,9 +1978,17 @@ static int io_timeout(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 		if (ctx->cached_sq_head < nxt_sq_head)
 			tmp += UINT_MAX;
 
-		if (tmp >= tmp_nxt)
+		if (tmp > tmp_nxt)
 			break;
+
+		/*
+		 * Sequence of reqs after the insert one and itself should
+		 * be adjusted because each timeout req consumes a slot.
+		 */
+		span++;
+		nxt->sequence++;
 	}
+	req->sequence -= span;
 	list_add(&req->list, entry);
 	spin_unlock_irq(&ctx->completion_lock);
 
@@ -2292,11 +2327,11 @@ static int io_req_set_file(struct io_ring_ctx *ctx, const struct sqe_submit *s,
 }
 
 static int __io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
-			struct sqe_submit *s, bool force_nonblock)
+			struct sqe_submit *s)
 {
 	int ret;
 
-	ret = __io_submit_sqe(ctx, req, s, force_nonblock);
+	ret = __io_submit_sqe(ctx, req, s, true);
 
 	/*
 	 * We async punt it if the file wasn't marked NOWAIT, or if the file
@@ -2343,7 +2378,7 @@ static int __io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
 }
 
 static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
-			struct sqe_submit *s, bool force_nonblock)
+			struct sqe_submit *s)
 {
 	int ret;
 
@@ -2356,18 +2391,17 @@ static int io_queue_sqe(struct io_ring_ctx *ctx, struct io_kiocb *req,
 		return 0;
 	}
 
-	return __io_queue_sqe(ctx, req, s, force_nonblock);
+	return __io_queue_sqe(ctx, req, s);
 }
 
 static int io_queue_link_head(struct io_ring_ctx *ctx, struct io_kiocb *req,
-			      struct sqe_submit *s, struct io_kiocb *shadow,
-			      bool force_nonblock)
+			      struct sqe_submit *s, struct io_kiocb *shadow)
 {
 	int ret;
 	int need_submit = false;
 
 	if (!shadow)
-		return io_queue_sqe(ctx, req, s, force_nonblock);
+		return io_queue_sqe(ctx, req, s);
 
 	/*
 	 * Mark the first IO in link list as DRAIN, let all the following
@@ -2396,7 +2430,7 @@ static int io_queue_link_head(struct io_ring_ctx *ctx, struct io_kiocb *req,
 	spin_unlock_irq(&ctx->completion_lock);
 
 	if (need_submit)
-		return __io_queue_sqe(ctx, req, s, force_nonblock);
+		return __io_queue_sqe(ctx, req, s);
 
 	return 0;
 }
@@ -2404,8 +2438,7 @@ static int io_queue_link_head(struct io_ring_ctx *ctx, struct io_kiocb *req,
 #define SQE_VALID_FLAGS	(IOSQE_FIXED_FILE|IOSQE_IO_DRAIN|IOSQE_IO_LINK)
 
 static void io_submit_sqe(struct io_ring_ctx *ctx, struct sqe_submit *s,
-			  struct io_submit_state *state, struct io_kiocb **link,
-			  bool force_nonblock)
+			  struct io_submit_state *state, struct io_kiocb **link)
 {
 	struct io_uring_sqe *sqe_copy;
 	struct io_kiocb *req;
@@ -2432,6 +2465,8 @@ err:
 		return;
 	}
 
+	req->user_data = s->sqe->user_data;
+
 	/*
 	 * If we already have a head request, queue this one for async
 	 * submittal once the head completes. If we don't have a head but
@@ -2458,7 +2493,7 @@ err:
 		INIT_LIST_HEAD(&req->link_list);
 		*link = req;
 	} else {
-		io_queue_sqe(ctx, req, s, force_nonblock);
+		io_queue_sqe(ctx, req, s);
 	}
 }
 
@@ -2538,12 +2573,13 @@ static bool io_get_sqring(struct io_ring_ctx *ctx, struct sqe_submit *s)
 
 	/* drop invalid entries */
 	ctx->cached_sq_head++;
-	rings->sq_dropped++;
+	ctx->cached_sq_dropped++;
+	WRITE_ONCE(rings->sq_dropped, ctx->cached_sq_dropped);
 	return false;
 }
 
-static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
-			  unsigned int nr, bool has_user, bool mm_fault)
+static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr,
+			  bool has_user, bool mm_fault)
 {
 	struct io_submit_state state, *statep = NULL;
 	struct io_kiocb *link = NULL;
@@ -2557,19 +2593,23 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
 	}
 
 	for (i = 0; i < nr; i++) {
+		struct sqe_submit s;
+
+		if (!io_get_sqring(ctx, &s))
+			break;
+
 		/*
 		 * If previous wasn't linked and we have a linked command,
 		 * that's the end of the chain. Submit the previous link.
 		 */
 		if (!prev_was_link && link) {
-			io_queue_link_head(ctx, link, &link->submit, shadow_req,
-						true);
+			io_queue_link_head(ctx, link, &link->submit, shadow_req);
 			link = NULL;
 			shadow_req = NULL;
 		}
-		prev_was_link = (sqes[i].sqe->flags & IOSQE_IO_LINK) != 0;
+		prev_was_link = (s.sqe->flags & IOSQE_IO_LINK) != 0;
 
-		if (link && (sqes[i].sqe->flags & IOSQE_IO_DRAIN)) {
+		if (link && (s.sqe->flags & IOSQE_IO_DRAIN)) {
 			if (!shadow_req) {
 				shadow_req = io_get_req(ctx, NULL);
 				if (unlikely(!shadow_req))
@@ -2577,24 +2617,24 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, struct sqe_submit *sqes,
 				shadow_req->flags |= (REQ_F_IO_DRAIN | REQ_F_SHADOW_DRAIN);
 				refcount_dec(&shadow_req->refs);
 			}
-			shadow_req->sequence = sqes[i].sequence;
+			shadow_req->sequence = s.sequence;
 		}
 
 out:
 		if (unlikely(mm_fault)) {
-			io_cqring_add_event(ctx, sqes[i].sqe->user_data,
+			io_cqring_add_event(ctx, s.sqe->user_data,
 						-EFAULT);
 		} else {
-			sqes[i].has_user = has_user;
-			sqes[i].needs_lock = true;
-			sqes[i].needs_fixed_file = true;
-			io_submit_sqe(ctx, &sqes[i], statep, &link, true);
+			s.has_user = has_user;
+			s.needs_lock = true;
+			s.needs_fixed_file = true;
+			io_submit_sqe(ctx, &s, statep, &link);
 			submitted++;
 		}
 	}
 
 	if (link)
-		io_queue_link_head(ctx, link, &link->submit, shadow_req, true);
+		io_queue_link_head(ctx, link, &link->submit, shadow_req);
 	if (statep)
 		io_submit_state_end(&state);
 
@@ -2603,7 +2643,6 @@ out:
 
 static int io_sq_thread(void *data)
 {
-	struct sqe_submit sqes[IO_IOPOLL_BATCH];
 	struct io_ring_ctx *ctx = data;
 	struct mm_struct *cur_mm = NULL;
 	mm_segment_t old_fs;
@@ -2618,14 +2657,27 @@ static int io_sq_thread(void *data)
 
 	timeout = inflight = 0;
 	while (!kthread_should_park()) {
-		bool all_fixed, mm_fault = false;
-		int i;
+		bool mm_fault = false;
+		unsigned int to_submit;
 
 		if (inflight) {
 			unsigned nr_events = 0;
 
 			if (ctx->flags & IORING_SETUP_IOPOLL) {
-				io_iopoll_check(ctx, &nr_events, 0);
+				/*
+				 * inflight is the count of the maximum possible
+				 * entries we submitted, but it can be smaller
+				 * if we dropped some of them. If we don't have
+				 * poll entries available, then we know that we
+				 * have nothing left to poll for. Reset the
+				 * inflight count to zero in that case.
+				 */
+				mutex_lock(&ctx->uring_lock);
+				if (!list_empty(&ctx->poll_list))
+					__io_iopoll_check(ctx, &nr_events, 0);
+				else
+					inflight = 0;
+				mutex_unlock(&ctx->uring_lock);
 			} else {
 				/*
 				 * Normal IO, just pretend everything completed.
@@ -2639,7 +2691,8 @@ static int io_sq_thread(void *data)
 				timeout = jiffies + ctx->sq_thread_idle;
 		}
 
-		if (!io_get_sqring(ctx, &sqes[0])) {
+		to_submit = io_sqring_entries(ctx);
+		if (!to_submit) {
 			/*
 			 * We're polling. If we're within the defined idle
 			 * period, then let us spin without work before going
@@ -2670,7 +2723,8 @@ static int io_sq_thread(void *data)
 			/* make sure to read SQ tail after writing flags */
 			smp_mb();
 
-			if (!io_get_sqring(ctx, &sqes[0])) {
+			to_submit = io_sqring_entries(ctx);
+			if (!to_submit) {
 				if (kthread_should_park()) {
 					finish_wait(&ctx->sqo_wait, &wait);
 					break;
@@ -2688,19 +2742,8 @@ static int io_sq_thread(void *data)
 			ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP;
 		}
 
-		i = 0;
-		all_fixed = true;
-		do {
-			if (all_fixed && io_sqe_needs_user(sqes[i].sqe))
-				all_fixed = false;
-
-			i++;
-			if (i == ARRAY_SIZE(sqes))
-				break;
-		} while (io_get_sqring(ctx, &sqes[i]));
-
 		/* Unless all new commands are FIXED regions, grab mm */
-		if (!all_fixed && !cur_mm) {
+		if (!cur_mm) {
 			mm_fault = !mmget_not_zero(ctx->sqo_mm);
 			if (!mm_fault) {
 				use_mm(ctx->sqo_mm);
@@ -2708,8 +2751,9 @@ static int io_sq_thread(void *data)
 			}
 		}
 
-		inflight += io_submit_sqes(ctx, sqes, i, cur_mm != NULL,
-						mm_fault);
+		to_submit = min(to_submit, ctx->sq_entries);
+		inflight += io_submit_sqes(ctx, to_submit, cur_mm != NULL,
+					   mm_fault);
 
 		/* Commit SQ ring head once we've consumed all SQEs */
 		io_commit_sqring(ctx);
@@ -2726,8 +2770,7 @@ static int io_sq_thread(void *data)
 	return 0;
 }
 
-static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
-			  bool block_for_last)
+static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit)
 {
 	struct io_submit_state state, *statep = NULL;
 	struct io_kiocb *link = NULL;
@@ -2741,7 +2784,6 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
 	}
 
 	for (i = 0; i < to_submit; i++) {
-		bool force_nonblock = true;
 		struct sqe_submit s;
 
 		if (!io_get_sqring(ctx, &s))
@@ -2752,8 +2794,7 @@ static int io_ring_submit(struct io_ring_ctx *ctx, unsigned int to_submit,
 		 * that's the end of the chain. Submit the previous link.
 		 */
 		if (!prev_was_link && link) {
-			io_queue_link_head(ctx, link, &link->submit, shadow_req,
-						force_nonblock);
+			io_queue_link_head(ctx, link, &link->submit, shadow_req);
 			link = NULL;
 			shadow_req = NULL;
 		}
@@ -2775,27 +2816,16 @@ out:
 		s.needs_lock = false;
 		s.needs_fixed_file = false;
 		submit++;
-
-		/*
-		 * The caller will block for events after submit, submit the
-		 * last IO non-blocking. This is either the only IO it's
-		 * submitting, or it already submitted the previous ones. This
-		 * improves performance by avoiding an async punt that we don't
-		 * need to do.
-		 */
-		if (block_for_last && submit == to_submit)
-			force_nonblock = false;
-
-		io_submit_sqe(ctx, &s, statep, &link, force_nonblock);
+		io_submit_sqe(ctx, &s, statep, &link);
 	}
-	io_commit_sqring(ctx);
 
 	if (link)
-		io_queue_link_head(ctx, link, &link->submit, shadow_req,
-					!block_for_last);
+		io_queue_link_head(ctx, link, &link->submit, shadow_req);
 	if (statep)
 		io_submit_state_end(statep);
 
+	io_commit_sqring(ctx);
+
 	return submit;
 }
 
@@ -3636,21 +3666,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
 			wake_up(&ctx->sqo_wait);
 		submitted = to_submit;
 	} else if (to_submit) {
-		bool block_for_last = false;
-
 		to_submit = min(to_submit, ctx->sq_entries);
 
-		/*
-		 * Allow last submission to block in a series, IFF the caller
-		 * asked to wait for events and we don't currently have
-		 * enough. This potentially avoids an async punt.
-		 */
-		if (to_submit == min_complete &&
-		    io_cqring_events(ctx->rings) < min_complete)
-			block_for_last = true;
-
 		mutex_lock(&ctx->uring_lock);
-		submitted = io_ring_submit(ctx, to_submit, block_for_last);
+		submitted = io_ring_submit(ctx, to_submit);
 		mutex_unlock(&ctx->uring_lock);
 	}
 	if (flags & IORING_ENTER_GETEVENTS) {