io_uring: make IORING_OP_CANCEL_ASYNC deferrable

If we defer this command as part of a link, we have to make sure that
the SQE data has been read upfront. Integrate the async cancel op into
the prep handling to make it safe for SQE reuse.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index b041140..1d6a508 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -321,6 +321,11 @@ struct io_sync {
        int                             flags;
 };
 
+struct io_cancel {
+       struct file                     *file;
+       u64                             addr;
+};
+
 struct io_async_connect {
        struct sockaddr_storage         address;
 };
@@ -362,6 +367,7 @@ struct io_kiocb {
                struct io_poll_iocb     poll;
                struct io_accept        accept;
                struct io_sync          sync;
+               struct io_cancel        cancel;
        };
 
        const struct io_uring_sqe       *sqe;
@@ -3018,18 +3024,33 @@ done:
        io_put_req_find_next(req, nxt);
 }
 
-static int io_async_cancel(struct io_kiocb *req, struct io_kiocb **nxt)
+static int io_async_cancel_prep(struct io_kiocb *req)
 {
        const struct io_uring_sqe *sqe = req->sqe;
-       struct io_ring_ctx *ctx = req->ctx;
 
-       if (unlikely(ctx->flags & IORING_SETUP_IOPOLL))
+       if (req->flags & REQ_F_PREPPED)
+               return 0;
+       if (unlikely(req->ctx->flags & IORING_SETUP_IOPOLL))
                return -EINVAL;
        if (sqe->flags || sqe->ioprio || sqe->off || sqe->len ||
            sqe->cancel_flags)
                return -EINVAL;
 
-       io_async_find_and_cancel(ctx, req, READ_ONCE(sqe->addr), nxt, 0);
+       req->flags |= REQ_F_PREPPED;
+       req->cancel.addr = READ_ONCE(sqe->addr);
+       return 0;
+}
+
+static int io_async_cancel(struct io_kiocb *req, struct io_kiocb **nxt)
+{
+       struct io_ring_ctx *ctx = req->ctx;
+       int ret;
+
+       ret = io_async_cancel_prep(req);
+       if (ret)
+               return ret;
+
+       io_async_find_and_cancel(ctx, req, req->cancel.addr, nxt, 0);
        return 0;
 }
 
@@ -3087,6 +3108,9 @@ static int io_req_defer_prep(struct io_kiocb *req)
        case IORING_OP_TIMEOUT:
                ret = io_timeout_prep(req, io, false);
                break;
+       case IORING_OP_ASYNC_CANCEL:
+               ret = io_async_cancel_prep(req);
+               break;
        case IORING_OP_LINK_TIMEOUT:
                ret = io_timeout_prep(req, io, true);
                break;