Merge tag 'io_uring-5.14-2021-08-13' of git://git.kernel.dk/linux-block

Pull io_uring fixes from Jens Axboe:
 "A bit bigger than the previous weeks, but mostly just a few stable
  bound fixes. In detail:

   - Followup fixes to patches from last week for io-wq, turns out they
     weren't complete (Hao)

   - Two lockdep reported fixes out of the RT camp (me)

   - Sync the io_uring-cp example with liburing, as a few bug fixes
     never made it to the kernel carried version (me)

   - SQPOLL related TIF_NOTIFY_SIGNAL fix (Nadav)

   - Use WRITE_ONCE() when writing sq flags (Nadav)

   - io_rsrc_put_work() deadlock fix (Pavel)"

* tag 'io_uring-5.14-2021-08-13' of git://git.kernel.dk/linux-block:
  tools/io_uring/io_uring-cp: sync with liburing example
  io_uring: fix ctx-exit io_rsrc_put_work() deadlock
  io_uring: drop ctx->uring_lock before flushing work item
  io-wq: fix IO_WORKER_F_FIXED issue in create_io_worker()
  io-wq: fix bug of creating io-wokers unconditionally
  io_uring: rsrc ref lock needs to be IRQ safe
  io_uring: Use WRITE_ONCE() when writing to sq_flags
  io_uring: clear TIF_NOTIFY_SIGNAL when running task work

2 files changed, 48 insertions, 36 deletions

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 12fc19353bb0..7d2ed8c7dd31 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -129,7 +129,7 @@ struct io_cb_cancel_data {
 	bool cancel_all;
 };
 
-static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index);
+static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index, bool first);
 static void io_wqe_dec_running(struct io_worker *worker);
 
 static bool io_worker_get(struct io_worker *worker)
@@ -248,18 +248,20 @@ static void io_wqe_wake_worker(struct io_wqe *wqe, struct io_wqe_acct *acct)
 	rcu_read_unlock();
 
 	if (!ret) {
-		bool do_create = false;
+		bool do_create = false, first = false;
 
 		raw_spin_lock_irq(&wqe->lock);
 		if (acct->nr_workers < acct->max_workers) {
 			atomic_inc(&acct->nr_running);
 			atomic_inc(&wqe->wq->worker_refs);
+			if (!acct->nr_workers)
+				first = true;
 			acct->nr_workers++;
 			do_create = true;
 		}
 		raw_spin_unlock_irq(&wqe->lock);
 		if (do_create)
-			create_io_worker(wqe->wq, wqe, acct->index);
+			create_io_worker(wqe->wq, wqe, acct->index, first);
 	}
 }
 
@@ -282,16 +284,26 @@ static void create_worker_cb(struct callback_head *cb)
 	struct io_wq *wq;
 	struct io_wqe *wqe;
 	struct io_wqe_acct *acct;
+	bool do_create = false, first = false;
 
 	cwd = container_of(cb, struct create_worker_data, work);
 	wqe = cwd->wqe;
 	wq = wqe->wq;
 	acct = &wqe->acct[cwd->index];
 	raw_spin_lock_irq(&wqe->lock);
-	if (acct->nr_workers < acct->max_workers)
+	if (acct->nr_workers < acct->max_workers) {
+		if (!acct->nr_workers)
+			first = true;
 		acct->nr_workers++;
+		do_create = true;
+	}
 	raw_spin_unlock_irq(&wqe->lock);
-	create_io_worker(wq, cwd->wqe, cwd->index);
+	if (do_create) {
+		create_io_worker(wq, wqe, cwd->index, first);
+	} else {
+		atomic_dec(&acct->nr_running);
+		io_worker_ref_put(wq);
+	}
 	kfree(cwd);
 }
 
@@ -629,7 +641,7 @@ void io_wq_worker_sleeping(struct task_struct *tsk)
 	raw_spin_unlock_irq(&worker->wqe->lock);
 }
 
-static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index)
+static void create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index, bool first)
 {
 	struct io_wqe_acct *acct = &wqe->acct[index];
 	struct io_worker *worker;
@@ -670,7 +682,7 @@ fail:
 	worker->flags |= IO_WORKER_F_FREE;
 	if (index == IO_WQ_ACCT_BOUND)
 		worker->flags |= IO_WORKER_F_BOUND;
-	if ((acct->nr_workers == 1) && (worker->flags & IO_WORKER_F_BOUND))
+	if (first && (worker->flags & IO_WORKER_F_BOUND))
 		worker->flags |= IO_WORKER_F_FIXED;
 	raw_spin_unlock_irq(&wqe->lock);
 	wake_up_new_task(tsk);
diff --git a/fs/io_uring.c b/fs/io_uring.c
index bf548af0426c..04c6d059ea94 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -78,6 +78,7 @@
 #include <linux/task_work.h>
 #include <linux/pagemap.h>
 #include <linux/io_uring.h>
+#include <linux/tracehook.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/io_uring.h>
@@ -1499,7 +1500,8 @@ static bool __io_cqring_overflow_flush(struct io_ring_ctx *ctx, bool force)
 	all_flushed = list_empty(&ctx->cq_overflow_list);
 	if (all_flushed) {
 		clear_bit(0, &ctx->check_cq_overflow);
-		ctx->rings->sq_flags &= ~IORING_SQ_CQ_OVERFLOW;
+		WRITE_ONCE(ctx->rings->sq_flags,
+			   ctx->rings->sq_flags & ~IORING_SQ_CQ_OVERFLOW);
 	}
 
 	if (posted)
@@ -1578,7 +1580,9 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
 	}
 	if (list_empty(&ctx->cq_overflow_list)) {
 		set_bit(0, &ctx->check_cq_overflow);
-		ctx->rings->sq_flags |= IORING_SQ_CQ_OVERFLOW;
+		WRITE_ONCE(ctx->rings->sq_flags,
+			   ctx->rings->sq_flags | IORING_SQ_CQ_OVERFLOW);
+
 	}
 	ocqe->cqe.user_data = user_data;
 	ocqe->cqe.res = res;
@@ -2222,9 +2226,9 @@ static inline unsigned int io_put_rw_kbuf(struct io_kiocb *req)
 
 static inline bool io_run_task_work(void)
 {
-	if (current->task_works) {
+	if (test_thread_flag(TIF_NOTIFY_SIGNAL) || current->task_works) {
 		__set_current_state(TASK_RUNNING);
-		task_work_run();
+		tracehook_notify_signal();
 		return true;
 	}
 
@@ -6803,14 +6807,16 @@ static inline void io_ring_set_wakeup_flag(struct io_ring_ctx *ctx)
 {
 	/* Tell userspace we may need a wakeup call */
 	spin_lock_irq(&ctx->completion_lock);
-	ctx->rings->sq_flags |= IORING_SQ_NEED_WAKEUP;
+	WRITE_ONCE(ctx->rings->sq_flags,
+		   ctx->rings->sq_flags | IORING_SQ_NEED_WAKEUP);
 	spin_unlock_irq(&ctx->completion_lock);
 }
 
 static inline void io_ring_clear_wakeup_flag(struct io_ring_ctx *ctx)
 {
 	spin_lock_irq(&ctx->completion_lock);
-	ctx->rings->sq_flags &= ~IORING_SQ_NEED_WAKEUP;
+	WRITE_ONCE(ctx->rings->sq_flags,
+		   ctx->rings->sq_flags & ~IORING_SQ_NEED_WAKEUP);
 	spin_unlock_irq(&ctx->completion_lock);
 }
 
@@ -7132,16 +7138,6 @@ static void **io_alloc_page_table(size_t size)
 	return table;
 }
 
-static inline void io_rsrc_ref_lock(struct io_ring_ctx *ctx)
-{
-	spin_lock_bh(&ctx->rsrc_ref_lock);
-}
-
-static inline void io_rsrc_ref_unlock(struct io_ring_ctx *ctx)
-{
-	spin_unlock_bh(&ctx->rsrc_ref_lock);
-}
-
 static void io_rsrc_node_destroy(struct io_rsrc_node *ref_node)
 {
 	percpu_ref_exit(&ref_node->refs);
@@ -7158,9 +7154,9 @@ static void io_rsrc_node_switch(struct io_ring_ctx *ctx,
 		struct io_rsrc_node *rsrc_node = ctx->rsrc_node;
 
 		rsrc_node->rsrc_data = data_to_kill;
-		io_rsrc_ref_lock(ctx);
+		spin_lock_irq(&ctx->rsrc_ref_lock);
 		list_add_tail(&rsrc_node->node, &ctx->rsrc_ref_list);
-		io_rsrc_ref_unlock(ctx);
+		spin_unlock_irq(&ctx->rsrc_ref_lock);
 
 		atomic_inc(&data_to_kill->refs);
 		percpu_ref_kill(&rsrc_node->refs);
@@ -7199,17 +7195,19 @@ static int io_rsrc_ref_quiesce(struct io_rsrc_data *data, struct io_ring_ctx *ct
 		/* kill initial ref, already quiesced if zero */
 		if (atomic_dec_and_test(&data->refs))
 			break;
+		mutex_unlock(&ctx->uring_lock);
 		flush_delayed_work(&ctx->rsrc_put_work);
 		ret = wait_for_completion_interruptible(&data->done);
-		if (!ret)
+		if (!ret) {
+			mutex_lock(&ctx->uring_lock);
 			break;
+		}
 
 		atomic_inc(&data->refs);
 		/* wait for all works potentially completing data->done */
 		flush_delayed_work(&ctx->rsrc_put_work);
 		reinit_completion(&data->done);
 
-		mutex_unlock(&ctx->uring_lock);
 		ret = io_run_task_work_sig();
 		mutex_lock(&ctx->uring_lock);
 	} while (ret >= 0);
@@ -7668,9 +7666,10 @@ static void io_rsrc_node_ref_zero(struct percpu_ref *ref)
 {
 	struct io_rsrc_node *node = container_of(ref, struct io_rsrc_node, refs);
 	struct io_ring_ctx *ctx = node->rsrc_data->ctx;
+	unsigned long flags;
 	bool first_add = false;
 
-	io_rsrc_ref_lock(ctx);
+	spin_lock_irqsave(&ctx->rsrc_ref_lock, flags);
 	node->done = true;
 
 	while (!list_empty(&ctx->rsrc_ref_list)) {
@@ -7682,7 +7681,7 @@ static void io_rsrc_node_ref_zero(struct percpu_ref *ref)
 		list_del(&node->node);
 		first_add |= llist_add(&node->llist, &ctx->rsrc_put_llist);
 	}
-	io_rsrc_ref_unlock(ctx);
+	spin_unlock_irqrestore(&ctx->rsrc_ref_lock, flags);
 
 	if (first_add)
 		mod_delayed_work(system_wq, &ctx->rsrc_put_work, HZ);
@@ -8653,13 +8652,10 @@ static void io_req_caches_free(struct io_ring_ctx *ctx)
 	mutex_unlock(&ctx->uring_lock);
 }
 
-static bool io_wait_rsrc_data(struct io_rsrc_data *data)
+static void io_wait_rsrc_data(struct io_rsrc_data *data)
 {
-	if (!data)
-		return false;
-	if (!atomic_dec_and_test(&data->refs))
+	if (data && !atomic_dec_and_test(&data->refs))
 		wait_for_completion(&data->done);
-	return true;
 }
 
 static void io_ring_ctx_free(struct io_ring_ctx *ctx)
@@ -8671,10 +8667,14 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 		ctx->mm_account = NULL;
 	}
 
+	/* __io_rsrc_put_work() may need uring_lock to progress, wait w/o it */
+	io_wait_rsrc_data(ctx->buf_data);
+	io_wait_rsrc_data(ctx->file_data);
+
 	mutex_lock(&ctx->uring_lock);
-	if (io_wait_rsrc_data(ctx->buf_data))
+	if (ctx->buf_data)
 		__io_sqe_buffers_unregister(ctx);
-	if (io_wait_rsrc_data(ctx->file_data))
+	if (ctx->file_data)
 		__io_sqe_files_unregister(ctx);
 	if (ctx->rings)
 		__io_cqring_overflow_flush(ctx, true);