[PATCH] io-wq: fix hang after cancelling pending work

[PATCH] io-wq: fix hang after cancelling pending work

[Pavel Begunkov]

Don't forget to update wqe->hash_tail after cancelling a pending work.

Cc: stable@vger.kernel.org # 5.7+
Reported-by: Dmitry Shulyak <yashulyak@gmail.com>
Fixes: 86f3cd1b589a1 ("io-wq: handle hashed writes in chains")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io-wq.c | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index e92c4724480c..414beb543883 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -925,6 +925,24 @@ static bool io_wq_worker_cancel(struct io_worker *worker, void *data)
 	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)
 {
@@ -938,8 +956,7 @@ static void io_wqe_cancel_pending_work(struct io_wqe *wqe,
 		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++;
-- 
2.24.0

Re: [PATCH] io-wq: fix hang after cancelling pending work

[Jens Axboe]

On 8/23/20 11:33 AM, Pavel Begunkov wrote:
> Don't forget to update wqe->hash_tail after cancelling a pending work.

Yep that fixes it, figured it was something related to hash work
cancelations. Applied!

-- 
Jens Axboe