FAILED: patch "[PATCH] io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Possible dependencies:

46a525e199e4 ("io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL") c0e0d6ba25f1 ("io_uring: add IORING_SETUP_DEFER_TASKRUN") b4c98d59a787 ("io_uring: introduce io_has_work")
78a861b94959 ("io_uring: add sync cancelation API through io_uring_register()") c34398a8c018 ("io_uring: remove __io_req_task_work_add") ed5ccb3beeba ("io_uring: remove priority tw list optimisation") 625d38b3fd34 ("io_uring: improve io_run_task_work()")
4a0fef62788b ("io_uring: optimize io_uring_task layout") 253993210bd8 ("io_uring: introduce locking helpers for CQE posting") 305bef988708 ("io_uring: hide eventfd assumptions in eventfd paths") affa87db9010 ("io_uring: fix multi ctx cancellation")
d9dee4302a7c ("io_uring: remove ->flush_cqes optimisation") a830ffd28780 ("io_uring: move io_eventfd_signal()")
9046c6415be6 ("io_uring: reshuffle io_uring/io_uring.h") d142c3ec8d16 ("io_uring: remove extra io_commit_cqring()") 68494a65d0e2 ("io_uring: introduce io_req_cqe_overflow()") faf88dde060f ("io_uring: don't inline __io_get_cqe()") d245bca6375b ("io_uring: don't expose io_fill_cqe_aux()") 9ca9fb24d5fe ("io_uring: mutex locked poll hashing")
e6f89be61410 ("io_uring: introduce a struct for hash table")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 46a525e199e4037516f7e498c18f065b09df32ac Mon Sep 17 00:00:00 2001
From: Jens Axboe <[email protected]>
Date: Thu, 29 Sep 2022 15:29:13 -0600
Subject: [PATCH] io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL

This isn't a reliable mechanism to tell if we have task_work pending, we really should be looking at whether we have any items queued. This is problematic if forward progress is gated on running said task_work. One such example is reading from a pipe, where the write side has been closed right before the read is started. The fput() of the file queues TWA_RESUME task_work, and we need that task_work to be run before ->release() is called for the pipe. If ->release() isn't called, then the read will sit forever waiting on data that will never arise.

Fix this by io_run_task_work() so it checks if we have task_work pending rather than rely on TIF_NOTIFY_SIGNAL for that. The latter obviously doesn't work for task_work that is queued without TWA_SIGNAL.

index 177bd55357d7..48ce2348c8c1 100644
@@ -231,11 +231,11 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
 
 static inline int io_run_task_work(void)
 {
-	if (test_thread_flag(TIF_NOTIFY_SIGNAL)) {
+	if (task_work_pending(current)) {
+		if (test_thread_flag(TIF_NOTIFY_SIGNAL))
+			clear_notify_signal();
 		__set_current_state(TASK_RUNNING);
-		clear_notify_signal();
-		if (task_work_pending(current))
-			task_work_run();
+		task_work_run();
 		return 1;
 	}