linux-kernel - [PATCH v3 3/4] io_uring: Fix remove irrelevant req from the task

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Date:   Wed,  7 Oct 2020 11:16:34 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     axboe@...nel.dk, viro@...iv.linux.org.uk
Cc:     linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, zhuyinyin@...edance.com,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH v3 3/4] io_uring: Fix remove irrelevant req from the task_list

If the process 0 has been initialized io_uring is complete, and
then fork process 1. If process 1 exits and it leads to delete
all reqs from the task_list. If we kill process 0. We will not
send SIGINT signal to the kworker. So we can not remove the req
from the task_list. The io_sq_wq_submit_work() can do that for
us.

Fixes: 1c4404efcf2c ("io_uring: make sure async workqueue is canceled on exit")
Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 fs/io_uring.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 5d9583e3d0d25..c65f78f395655 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2277,13 +2277,11 @@ static void io_sq_wq_submit_work(struct work_struct *work)
 					break;
 				cond_resched();
 			} while (1);
-end_req:
-			if (!list_empty(&req->task_list)) {
-				spin_lock_irq(&ctx->task_lock);
-				list_del_init(&req->task_list);
-				spin_unlock_irq(&ctx->task_lock);
-			}
 		}
+end_req:
+		spin_lock_irq(&ctx->task_lock);
+		list_del_init(&req->task_list);
+		spin_unlock_irq(&ctx->task_lock);
 
 		/* drop submission reference */
 		io_put_req(req);
@@ -3727,15 +3725,16 @@ static int io_uring_fasync(int fd, struct file *file, int on)
 static void io_cancel_async_work(struct io_ring_ctx *ctx,
 				 struct files_struct *files)
 {
+	struct io_kiocb *req;
+
 	if (list_empty(&ctx->task_list))
 		return;
 
 	spin_lock_irq(&ctx->task_lock);
-	while (!list_empty(&ctx->task_list)) {
-		struct io_kiocb *req;
 
-		req = list_first_entry(&ctx->task_list, struct io_kiocb, task_list);
-		list_del_init(&req->task_list);
+	list_for_each_entry(req, &ctx->task_list, task_list) {
+		if (files && req->files != files)
+			continue;
 
 		/*
 		 * The below executes an smp_mb(), which matches with the
@@ -3745,7 +3744,7 @@ static void io_cancel_async_work(struct io_ring_ctx *ctx,
 		 */
 		smp_store_mb(req->flags, req->flags | REQ_F_CANCEL); /* B */
 
-		if (req->work_task && (!files || req->files == files))
+		if (req->work_task)
 			send_sig(SIGINT, req->work_task, 1);
 	}
 	spin_unlock_irq(&ctx->task_lock);
-- 
2.11.0