io_uring: make reg buf init consistent

The default (i.e. empty) state of register buffer is dummy_ubuf, so set
it to dummy on init instead of NULL.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c5456aecf03d9627fbd6e65e100e2b5293a6151e.1655310733.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 8c40b20..214ff0d 100644 (file)
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -567,7 +567,7 @@ static int __io_sqe_buffers_update(struct io_ring_ctx *ctx,
                                io_buffer_unmap(ctx, &imu);
                                break;
                        }
-                       ctx->user_bufs[i] = NULL;
+                       ctx->user_bufs[i] = ctx->dummy_ubuf;
                        needs_switch = true;
                }
 
@@ -1203,14 +1203,11 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
        size_t size;
        int ret, nr_pages, i;
 
-       if (!iov->iov_base) {
-               *pimu = ctx->dummy_ubuf;
+       *pimu = ctx->dummy_ubuf;
+       if (!iov->iov_base)
                return 0;
-       }
 
-       *pimu = NULL;
        ret = -ENOMEM;
-
        pages = io_pin_pages((unsigned long) iov->iov_base, iov->iov_len,
                                &nr_pages);
        if (IS_ERR(pages)) {