io_uring/sqpoll: fix io-wq affinity when IORING_SETUP_SQPOLL is used

If we setup the ring with SQPOLL, then that polling thread has its
own io-wq setup. This means that if the application uses
IORING_REGISTER_IOWQ_AFF to set the io-wq affinity, we should not be
setting it for the invoking task, but rather the sqpoll task.

Add an sqpoll helper that parks the thread and updates the affinity,
and use that one if we're using SQPOLL.

Fixes: fe76421d1da1 ("io_uring: allow user configurable IO thread CPU affinity")
Cc: stable@vger.kernel.org # 5.10+
Link: https://github.com/axboe/liburing/discussions/884
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 15 insertions, 0 deletions

diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
index 5e329e3cd470..ee2d2c687fda 100644
--- a/io_uring/sqpoll.c
+++ b/io_uring/sqpoll.c
@@ -421,3 +421,18 @@ err:
 	io_sq_thread_finish(ctx);
 	return ret;
 }
+
+__cold int io_sqpoll_wq_cpu_affinity(struct io_ring_ctx *ctx,
+				     cpumask_var_t mask)
+{
+	struct io_sq_data *sqd = ctx->sq_data;
+	int ret = -EINVAL;
+
+	if (sqd) {
+		io_sq_thread_park(sqd);
+		ret = io_wq_cpu_affinity(sqd->thread->io_uring, mask);
+		io_sq_thread_unpark(sqd);
+	}
+
+	return ret;
+}