linux-kernel - [PATCH 5.8 197/255] io-wq: fix hang after cancelling pending hashed work

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Message-Id: <20200901151010.126562760@linuxfoundation.org>
Date:   Tue,  1 Sep 2020 17:10:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Shulyak <yashulyak@...il.com>,
        Pavel Begunkov <asml.silence@...il.com>,
        Jens Axboe <axboe@...nel.dk>
Subject: [PATCH 5.8 197/255] io-wq: fix hang after cancelling pending hashed work

From: Pavel Begunkov <asml.silence@...il.com>

commit 204361a77f4018627addd4a06877448f088ddfc0 upstream.

Don't forget to update wqe->hash_tail after cancelling a pending work
item, if it was hashed.

Cc: stable@...r.kernel.org # 5.7+
Reported-by: Dmitry Shulyak <yashulyak@...il.com>
Fixes: 86f3cd1b589a1 ("io-wq: handle hashed writes in chains")
Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/io-wq.c |   21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -929,6 +929,24 @@ static bool io_wq_worker_cancel(struct i
 	return match->nr_running && !match->cancel_all;
 }
 
+static inline void io_wqe_remove_pending(struct io_wqe *wqe,
+					 struct io_wq_work *work,
+					 struct io_wq_work_node *prev)
+{
+	unsigned int hash = io_get_work_hash(work);
+	struct io_wq_work *prev_work = NULL;
+
+	if (io_wq_is_hashed(work) && work == wqe->hash_tail[hash]) {
+		if (prev)
+			prev_work = container_of(prev, struct io_wq_work, list);
+		if (prev_work && io_get_work_hash(prev_work) == hash)
+			wqe->hash_tail[hash] = prev_work;
+		else
+			wqe->hash_tail[hash] = NULL;
+	}
+	wq_list_del(&wqe->work_list, &work->list, prev);
+}
+
 static void io_wqe_cancel_pending_work(struct io_wqe *wqe,
 				       struct io_cb_cancel_data *match)
 {
@@ -942,8 +960,7 @@ retry:
 		work = container_of(node, struct io_wq_work, list);
 		if (!match->fn(work, match->data))
 			continue;
-
-		wq_list_del(&wqe->work_list, node, prev);
+		io_wqe_remove_pending(wqe, work, prev);
 		spin_unlock_irqrestore(&wqe->lock, flags);
 		io_run_cancel(work, wqe);
 		match->nr_pending++;