[PATCH 2/2] io_uring/cancel: complete single futex or waitid cancel with 0

[agxr]

A cancel of one request completes with 0, as io_uring_prep_cancel(3)
documents and as poll, io-wq and timeouts do. For a futex wait or a
waitid it completes with 1. io_futex_cancel() and io_waitid_cancel()
return the number canceled, and __io_async_cancel() hands it on, for
IORING_OP_ASYNC_CANCEL and IORING_REGISTER_SYNC_CANCEL alike.

Turn that count into 0, as io_req_task_link_timeout() does since commit
c74193430feb ("io_uring/timeout: don't end a linked timeout with 1").

liburing's futex and waitid tests expect the 1, and a liburing change
makes them accept 0 as well.

Fixes: 194bb58c6090 ("io_uring: add support for futex wake and wait")
Fixes: f31ecf671ddc ("io_uring: add IORING_OP_WAITID support")
Signed-off-by: agxr <agxr@xxxxxxxxxxx>
---
 io_uring/cancel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index e4b27b79b05c..20df4e3538f3 100644
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -197,7 +197,7 @@ static int __io_async_cancel(struct io_cancel_data *cd,
 		if (ret == -ENOENT)
 			break;
 		if (!all)
-			return ret;
+			return ret > 0 ? 0 : ret;
 		nr += ret > 0 ? ret : 1;
 	} while (1);
 
-- 
2.56.0