FAILED: patch "[PATCH] io_uring: fix no lock protection for ctx->cq_extra" 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]>.

thanks,

greg k-h

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

From e302f1046f4c209291b07ff7bc4d15ca26891f16 Mon Sep 17 00:00:00 2001
From: Hao Xu <[email protected]>
Date: Thu, 25 Nov 2021 17:21:02 +0800
Subject: [PATCH] io_uring: fix no lock protection for ctx->cq_extra

ctx->cq_extra should be protected by completion lock so that the req_need_defer() does the right check.

index f666a0e7f5e8..ae9534382b26 100644
@@ -6537,12 +6537,15 @@ static __cold void io_drain_req(struct io_kiocb *req)
 	u32 seq = io_get_sequence(req);
 
 	/* Still need defer if there is pending req in defer list. */
+	spin_lock(&ctx->completion_lock);
 	if (!req_need_defer(req, seq) && list_empty_careful(&ctx->defer_list)) {
+		spin_unlock(&ctx->completion_lock);
 queue:
 		ctx->drain_active = false;
 		io_req_task_queue(req);
 		return;
 	}
+	spin_unlock(&ctx->completion_lock);
 
 	ret = io_req_prep_async(req);
 	if (ret) {