io_uring: fix io_sq_offload_create error handling

Don't set IO_SQ_THREAD_SHOULD_STOP when io_sq_offload_create() has
failed on io_uring_alloc_task_context() but leave everything to
io_sq_thread_finish(), because currently io_sq_thread_finish()
hangs on trying to park it. That's great it stalls there, because
otherwise the following io_sq_thread_stop() would be skipped on
IO_SQ_THREAD_SHOULD_STOP check and the sqo would race for sqd with
freeing ctx.

A simple error injection gives something like this.

[  245.463955] INFO: task sqpoll-test-hang:523 blocked for more than 122 seconds.
[  245.463983] Call Trace:
[  245.463990]  __schedule+0x36b/0x950
[  245.464005]  schedule+0x68/0xe0
[  245.464013]  schedule_timeout+0x209/0x2a0
[  245.464032]  wait_for_completion+0x8b/0xf0
[  245.464043]  io_sq_thread_finish+0x44/0x1a0
[  245.464049]  io_uring_setup+0x9ea/0xc80
[  245.464058]  __x64_sys_io_uring_setup+0x16/0x20
[  245.464064]  do_syscall_64+0x38/0x50
[  245.464073]  entry_SYSCALL_64_after_hwframe+0x44/0xae

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

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 84eb499368a4bc985eb6580dcea845cb5b439812..3299807894ec0091f226473c7fad549759606ad6 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7856,10 +7856,9 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
                        ret = PTR_ERR(tsk);
                        goto err;
                }
-               ret = io_uring_alloc_task_context(tsk, ctx);
-               if (ret)
-                       set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
+
                sqd->thread = tsk;
+               ret = io_uring_alloc_task_context(tsk, ctx);
                wake_up_new_task(tsk);
                if (ret)
                        goto err;