From efdf518459b17e18a93c7c9cb622fd3051dabd0c Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Tue, 18 Jan 2022 19:22:32 -0700
Subject: [PATCH] io-wq: perform both unstarted and started work cancelations
 in one go
Git-commit: efdf518459b17e18a93c7c9cb622fd3051dabd0c
Patch-mainline: v5.17-rc1
References: bsc#1205205

Rather than split these into two separate lookups and matches, combine
them into one loop. This will become important when we can guarantee
that we don't have a window where a pending work item isn't discoverable
in either state.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/io-wq.c | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index a92fbdc8bea3..db150186ce94 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -1072,27 +1072,25 @@ enum io_wq_cancel io_wq_cancel_cb(struct io_wq *wq, work_cancel_fn *cancel,
 	 * First check pending list, if we're lucky we can just remove it
 	 * from there. CANCEL_OK means that the work is returned as-new,
 	 * no completion will be posted for it.
-	 */
-	for_each_node(node) {
-		struct io_wqe *wqe = wq->wqes[node];
-
-		raw_spin_lock(&wqe->lock);
-		io_wqe_cancel_pending_work(wqe, &match);
-		raw_spin_unlock(&wqe->lock);
-		if (match.nr_pending && !match.cancel_all)
-			return IO_WQ_CANCEL_OK;
-	}
-
-	/*
-	 * Now check if a free (going busy) or busy worker has the work
+	 *
+	 * Then check if a free (going busy) or busy worker has the work
 	 * currently running. If we find it there, we'll return CANCEL_RUNNING
 	 * as an indication that we attempt to signal cancellation. The
 	 * completion will run normally in this case.
+	 *
+	 * Do both of these while holding the wqe->lock, to ensure that
+	 * we'll find a work item regardless of state.
 	 */
 	for_each_node(node) {
 		struct io_wqe *wqe = wq->wqes[node];
 
 		raw_spin_lock(&wqe->lock);
+		io_wqe_cancel_pending_work(wqe, &match);
+		if (match.nr_pending && !match.cancel_all) {
+			raw_spin_unlock(&wqe->lock);
+			return IO_WQ_CANCEL_OK;
+		}
+
 		io_wqe_cancel_running_work(wqe, &match);
 		raw_spin_unlock(&wqe->lock);
 		if (match.nr_running && !match.cancel_all)
-- 
2.35.3