[PATCH 5.10 002/103] io_uring: synchronise IOPOLL on task_submit fail

[Greg Kroah-Hartman]

From: Pavel Begunkov <asml.silence@xxxxxxxxx>

commit 81b6d05ccad4f3d8a9dfb091fb46ad6978ee40e4 upstream

io_req_task_submit() might be called for IOPOLL, do the fail path under
uring_lock to comply with IOPOLL synchronisation based solely on it.

Cc: stable@xxxxxxxxxxxxxxx # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/io_uring.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1f798c5c4213e..3974b4f124b6a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2047,14 +2047,15 @@ static void io_req_task_cancel(struct callback_head *cb)
 static void __io_req_task_submit(struct io_kiocb *req)
 {
 	struct io_ring_ctx *ctx = req->ctx;
+	bool fail;
 
-	if (!__io_sq_thread_acquire_mm(ctx)) {
-		mutex_lock(&ctx->uring_lock);
+	fail = __io_sq_thread_acquire_mm(ctx);
+	mutex_lock(&ctx->uring_lock);
+	if (!fail)
 		__io_queue_sqe(req, NULL);
-		mutex_unlock(&ctx->uring_lock);
-	} else {
+	else
 		__io_req_task_cancel(req, -EFAULT);
-	}
+	mutex_unlock(&ctx->uring_lock);
 }
 
 static void io_req_task_submit(struct callback_head *cb)
-- 
2.27.0