linux-kernel - [PATCH v2] io_uring: fix overflowed reqs cancellation

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Date:   Sat, 30 May 2020 14:19:15 +0300
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] io_uring: fix overflowed reqs cancellation

Overflowed requests in io_uring_cancel_files() should be shed only of
inflight and overflowed refs. All other left references are owned by
someone else.

If refcount_sub_and_test() fails, it will go further and put put extra
ref, don't do that. Also, don't need to do io_wq_cancel_work()
for overflowed reqs, they will be let go shortly anyway.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---

v2: don't schedule() if requests is already freed

 fs/io_uring.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index bc5117ee6ce3..b1c30284efbf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7447,10 +7447,11 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,
 				finish_wait(&ctx->inflight_wait, &wait);
 				continue;
 			}
+		} else {
+			io_wq_cancel_work(ctx->io_wq, &cancel_req->work);
+			io_put_req(cancel_req);
 		}
 
-		io_wq_cancel_work(ctx->io_wq, &cancel_req->work);
-		io_put_req(cancel_req);
 		schedule();
 		finish_wait(&ctx->inflight_wait, &wait);
 	}
-- 
2.24.0