[RFC 5.12] io-wq: cancel unbounded works on io-wq destroy

[Pavel Begunkov <asml.silence@gmail.com>]

[  491.222908] INFO: task thread-exit:2490 blocked for more than 122 seconds.
[  491.222957] Call Trace:
[  491.222967]  __schedule+0x36b/0x950
[  491.222985]  schedule+0x68/0xe0
[  491.222994]  schedule_timeout+0x209/0x2a0
[  491.223003]  ? tlb_flush_mmu+0x28/0x140
[  491.223013]  wait_for_completion+0x8b/0xf0
[  491.223023]  io_wq_destroy_manager+0x24/0x60
[  491.223037]  io_wq_put_and_exit+0x18/0x30
[  491.223045]  io_uring_clean_tctx+0x76/0xa0
[  491.223061]  __io_uring_files_cancel+0x1b9/0x2e0
[  491.223068]  ? blk_finish_plug+0x26/0x40
[  491.223085]  do_exit+0xc0/0xb40
[  491.223099]  ? syscall_trace_enter.isra.0+0x1a1/0x1e0
[  491.223109]  __x64_sys_exit+0x1b/0x20
[  491.223117]  do_syscall_64+0x38/0x50
[  491.223131]  entry_SYSCALL_64_after_hwframe+0x44/0xae
[  491.223177] INFO: task iou-mgr-2490:2491 blocked for more than 122 seconds.
[  491.223194] Call Trace:
[  491.223198]  __schedule+0x36b/0x950
[  491.223206]  ? pick_next_task_fair+0xcf/0x3e0
[  491.223218]  schedule+0x68/0xe0
[  491.223225]  schedule_timeout+0x209/0x2a0
[  491.223236]  wait_for_completion+0x8b/0xf0
[  491.223246]  io_wq_manager+0xf1/0x1d0
[  491.223255]  ? recalc_sigpending+0x1c/0x60
[  491.223265]  ? io_wq_cpu_online+0x40/0x40
[  491.223272]  ret_from_fork+0x22/0x30

Cancel all unbound works on exit, otherwise do_exit() ->
io_uring_files_cancel() may wait for io-wq destruction for long, e.g.
until somewhat sends a SIGKILL.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---

Not quite happy about it as it cancels pipes and sockets, but
is probably better than waiting.

 fs/io-wq.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 433c4d3c3c1c..e2ab569e47b9 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -702,6 +702,11 @@ static void io_wq_cancel_pending(struct io_wq *wq)
 		io_wqe_cancel_pending_work(wq->wqes[node], &match);
 }
 
+static bool io_wq_cancel_unbounded(struct io_wq_work *work, void *data)
+{
+	return work->flags & IO_WQ_WORK_UNBOUND;
+}
+
 /*
  * Manager thread. Tasked with creating new workers, if we need them.
  */
@@ -736,6 +741,8 @@ static int io_wq_manager(void *data)
 
 	if (atomic_dec_and_test(&wq->worker_refs))
 		complete(&wq->worker_done);
+
+	io_wq_cancel_cb(wq, io_wq_cancel_unbounded, NULL, true);
 	wait_for_completion(&wq->worker_done);
 
 	spin_lock_irq(&wq->hash->wait.lock);
-- 
2.24.0