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FAILED: patch "[PATCH] io_uring: fix work_exit sqpoll cancellations" failed to apply to 5.11-stable tree

PATCH [email protected] 1 participant 1 message May 10, 2021

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The patch below does not apply to the 5.11-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 28090c133869b461c5366195a856d73469ab87d9 Mon Sep 17 00:00:00 2001
From: Pavel Begunkov <[email protected]>
Date: Sun, 25 Apr 2021 23:34:45 +0100
Subject: [PATCH] io_uring: fix work_exit sqpoll cancellations

After closing an SQPOLL ring, io_ring_exit_work() kicks in and starts doing cancellations via io_uring_try_cancel_requests(). It will go through io_uring_try_cancel_iowq(), which uses ctx->tctx_list, but as SQPOLL task don't have a ctx note, its io-wq won't be reachable and so is left not cancelled.

It will eventually cancelled when one of the tasks dies, but if a thread group survives for long and changes rings, it will spawn lots of unreclaimed resources and live locked works.

Cancel SQPOLL task's io-wq separately in io_ring_exit_work().

Cc [email protected]
Signed-off-by Pavel Begunkov <[email protected]>
Link https://lore.kernel.org/r/a71a7fe345135d684025bb529d5cb1d8d6b46e10.1619389911.git.asml.silence@gmail.com open here
Signed-off-by Jens Axboe <[email protected]>
fs/io_uring.c +18 -7
index 577520445fa0..f20622bd963b 100644
@@ -8679,6 +8679,13 @@ static void io_tctx_exit_cb(struct callback_head *cb)
 	complete(&work->completion);
 }
 
+static bool io_cancel_ctx_cb(struct io_wq_work *work, void *data)
+{
+	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
+
+	return req->ctx == data;
+}
+
 static void io_ring_exit_work(struct work_struct *work)
 {
 	struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx, exit_work);

@@ -8695,6 +8702,17 @@ static void io_ring_exit_work(struct work_struct *work)
 	 */
 	do {
 		io_uring_try_cancel_requests(ctx, NULL, NULL);
+		if (ctx->sq_data) {
+			struct io_sq_data *sqd = ctx->sq_data;
+			struct task_struct *tsk;
+
+			io_sq_thread_park(sqd);
+			tsk = sqd->thread;
+			if (tsk && tsk->io_uring && tsk->io_uring->io_wq)
+				io_wq_cancel_cb(tsk->io_uring->io_wq,
+						io_cancel_ctx_cb, ctx, true);
+			io_sq_thread_unpark(sqd);
+		}
 
 		WARN_ON_ONCE(time_after(jiffies, timeout));
 	} while (!wait_for_completion_timeout(&ctx->ref_comp, HZ/20));

@@ -8844,13 +8862,6 @@ static bool io_cancel_defer_files(struct io_ring_ctx *ctx,
 	return true;
 }
 
-static bool io_cancel_ctx_cb(struct io_wq_work *work, void *data)
-{
-	struct io_kiocb *req = container_of(work, struct io_kiocb, work);
-
-	return req->ctx == data;
-}
-
 static bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
 {
 	struct io_tctx_node *node;