[PATCH 5.4 06/85] io_uring: Fix missing smp_mb() in io_cancel_async_work()

[PATCH 5.4 06/85] io_uring: Fix missing smp_mb() in io_cancel_async_work()

[Greg Kroah-Hartman]

From: Muchun Song <songmuchun@bytedance.com>

The store to req->flags and load req->work_task should not be
reordering in io_cancel_async_work(). We should make sure that
either we store REQ_F_CANCE flag to req->flags or we see the
req->work_task setted in io_sq_wq_submit_work().

Fixes: 1c4404efcf2c ("io_uring: make sure async workqueue is canceled on exit")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/io_uring.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2247,6 +2247,12 @@ restart:
 
 		if (!ret) {
 			req->work_task = current;
+
+			/*
+			 * Pairs with the smp_store_mb() (B) in
+			 * io_cancel_async_work().
+			 */
+			smp_mb(); /* A */
 			if (req->flags & REQ_F_CANCEL) {
 				ret = -ECANCELED;
 				goto end_req;
@@ -3725,7 +3731,15 @@ static void io_cancel_async_work(struct
 
 		req = list_first_entry(&ctx->task_list, struct io_kiocb, task_list);
 		list_del_init(&req->task_list);
-		req->flags |= REQ_F_CANCEL;
+
+		/*
+		 * The below executes an smp_mb(), which matches with the
+		 * smp_mb() (A) in io_sq_wq_submit_work() such that either
+		 * we store REQ_F_CANCEL flag to req->flags or we see the
+		 * req->work_task setted in io_sq_wq_submit_work().
+		 */
+		smp_store_mb(req->flags, req->flags | REQ_F_CANCEL); /* B */
+
 		if (req->work_task && (!files || req->files == files))
 			send_sig(SIGINT, req->work_task, 1);
 	}

[PATCH 5.4 07/85] io_uring: Fix remove irrelevant req from the task_list

[Greg Kroah-Hartman]

From: Muchun Song <songmuchun@bytedance.com>

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@bytedance.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/io_uring.c |   21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2272,13 +2272,11 @@ restart:
 					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);
@@ -3722,15 +3720,16 @@ static int io_uring_fasync(int fd, struc
 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
@@ -3740,7 +3739,7 @@ static void io_cancel_async_work(struct
 		 */
 		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);