[PATCH 6.1 36/61] io_uring: backport io_should_terminate_tw()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jens Axboe <axboe@kernel.dk>

Parts of commit b6f58a3f4aa8dba424356c7a69388a81f4459300 upstream.

Backport io_should_terminate_tw() helper to judge whether task_work
should be run or terminated.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 io_uring/io_uring.c |    5 ++---
 io_uring/io_uring.h |   13 +++++++++++++
 io_uring/poll.c     |    3 +--
 io_uring/timeout.c  |    2 +-
 4 files changed, 17 insertions(+), 6 deletions(-)

--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1249,8 +1249,7 @@ static void io_req_task_cancel(struct io
 void io_req_task_submit(struct io_kiocb *req, bool *locked)
 {
 	io_tw_lock(req->ctx, locked);
-	/* req->task == current here, checking PF_EXITING is safe */
-	if (likely(!(req->task->flags & PF_EXITING)))
+	if (likely(!io_should_terminate_tw()))
 		io_queue_sqe(req);
 	else
 		io_req_complete_failed(req, -EFAULT);
@@ -1773,7 +1772,7 @@ static int io_issue_sqe(struct io_kiocb
 int io_poll_issue(struct io_kiocb *req, bool *locked)
 {
 	io_tw_lock(req->ctx, locked);
-	if (unlikely(req->task->flags & PF_EXITING))
+	if (unlikely(io_should_terminate_tw()))
 		return -EFAULT;
 	return io_issue_sqe(req, IO_URING_F_NONBLOCK|IO_URING_F_MULTISHOT);
 }
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -395,6 +395,19 @@ static inline bool io_allowed_run_tw(str
 		      ctx->submitter_task == current);
 }
 
+/*
+ * Terminate the request if either of these conditions are true:
+ *
+ * 1) It's being executed by the original task, but that task is marked
+ *    with PF_EXITING as it's exiting.
+ * 2) PF_KTHREAD is set, in which case the invoker of the task_work is
+ *    our fallback task_work.
+ */
+static inline bool io_should_terminate_tw(void)
+{
+	return current->flags & (PF_KTHREAD | PF_EXITING);
+}
+
 static inline void io_req_queue_tw_complete(struct io_kiocb *req, s32 res)
 {
 	io_req_set_res(req, res, 0);
--- a/io_uring/poll.c
+++ b/io_uring/poll.c
@@ -241,8 +241,7 @@ static int io_poll_check_events(struct i
 	struct io_ring_ctx *ctx = req->ctx;
 	int v;
 
-	/* req->task == current here, checking PF_EXITING is safe */
-	if (unlikely(req->task->flags & PF_EXITING))
+	if (unlikely(io_should_terminate_tw()))
 		return -ECANCELED;
 
 	do {
--- a/io_uring/timeout.c
+++ b/io_uring/timeout.c
@@ -275,7 +275,7 @@ static void io_req_task_link_timeout(str
 	int ret = -ENOENT;
 
 	if (prev) {
-		if (!(req->task->flags & PF_EXITING)) {
+		if (!io_should_terminate_tw()) {
 			struct io_cancel_data cd = {
 				.ctx		= req->ctx,
 				.data		= prev->cqe.user_data,