[PATCH 2/5] io_uring: replace find_next() out param with ret

Pavel Begunkov
2020-06-29T21:03:26Z

Generally, it's better to return a value directly than having out
parameter. It's cleaner and saves from some kinds of ugly bugs.
May also be faster.

Return next request from io_req_find_next() and friends directly
instead of passing out parameter.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 36 ++++++++++++++++++------------------
1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4cd6d24276c3..52e5c8730dd5 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1578,7 +1578,7 @@ static void io_kill_linked_timeout(struct io_kiocb *req)
io_cqring_ev_posted(ctx);
}

-static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
+static struct io_kiocb *io_req_link_next(struct io_kiocb *req)
{
struct io_kiocb *nxt;

@@ -1588,13 +1588,13 @@ static void io_req_link_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
* safe side.
*/
if (unlikely(list_empty(&req->link_list)))
- return;
+ return NULL;

nxt = list_first_entry(&req->link_list, struct io_kiocb, link_list);
list_del_init(&req->link_list);
if (!list_empty(&nxt->link_list))
nxt->flags |= REQ_F_LINK_HEAD;
- *nxtptr = nxt;
+ return nxt;
}

/*
@@ -1620,10 +1620,10 @@ static void io_fail_links(struct io_kiocb *req)
io_cqring_ev_posted(ctx);
}

-static void io_req_find_next(struct io_kiocb *req, struct io_kiocb **nxt)
+static struct io_kiocb *io_req_find_next(struct io_kiocb *req)
{
if (likely(!(req->flags & REQ_F_LINK_HEAD)))
- return;
+ return NULL;
req->flags &= ~REQ_F_LINK_HEAD;

if (req->flags & REQ_F_LINK_TIMEOUT)
@@ -1635,10 +1635,10 @@ static void io_req_find_next(struct io_kiocb *req, struct io_kiocb **nxt)
* dependencies to the next request. In case of failure, fail the rest
* of the chain.
*/
- if (req->flags & REQ_F_FAIL_LINK)
- io_fail_links(req);
- else
- io_req_link_next(req, nxt);
+ if (likely(!(req->flags & REQ_F_FAIL_LINK)))
+ return io_req_link_next(req);
+ io_fail_links(req);
+ return NULL;
}

static void __io_req_task_cancel(struct io_kiocb *req, int error)
@@ -1701,9 +1701,8 @@ static void io_req_task_queue(struct io_kiocb *req)

static void io_queue_next(struct io_kiocb *req)
{
- struct io_kiocb *nxt = NULL;
+ struct io_kiocb *nxt = io_req_find_next(req);

- io_req_find_next(req, &nxt);
if (nxt)
io_req_task_queue(nxt);
}
@@ -1753,13 +1752,15 @@ static void io_req_free_batch(struct req_batch *rb, struct io_kiocb *req)
* Drop reference to request, return next in chain (if there is one) if this
* was the last reference to this request.
*/
-__attribute__((nonnull))
-static void io_put_req_find_next(struct io_kiocb *req, struct io_kiocb **nxtptr)
+static struct io_kiocb *io_put_req_find_next(struct io_kiocb *req)
{
+ struct io_kiocb *nxt = NULL;
+
if (refcount_dec_and_test(&req->refs)) {
- io_req_find_next(req, nxtptr);
+ nxt = io_req_find_next(req);
__io_free_req(req);
}
+ return nxt;
}

static void io_put_req(struct io_kiocb *req)
@@ -1780,7 +1781,7 @@ static struct io_wq_work *io_steal_work(struct io_kiocb *req)
if (refcount_read(&req->refs) != 1)
return NULL;

- io_req_find_next(req, &nxt);
+ nxt = io_req_find_next(req);
if (!nxt)
return NULL;

@@ -4465,7 +4466,7 @@ static void io_poll_task_handler(struct io_kiocb *req, struct io_kiocb **nxt)
hash_del(&req->hash_node);
io_poll_complete(req, req->result, 0);
req->flags |= REQ_F_COMP_LOCKED;
- io_put_req_find_next(req, nxt);
+ *nxt = io_put_req_find_next(req);
spin_unlock_irq(&ctx->completion_lock);

io_cqring_ev_posted(ctx);
@@ -5915,9 +5916,8 @@ static void __io_queue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
}

err:
- nxt = NULL;
/* drop submission reference */
- io_put_req_find_next(req, &nxt);
+ nxt = io_put_req_find_next(req);

if (linked_timeout) {
if (!ret)
--
2.24.0