[PATCH 15/17] io_uring: add io_kiocb ref count

[Jens Axboe <axboe@kernel.dk>]

We'll use this for the POLL implementation. Regular requests will
NOT be using references, so initialize it to 0. Any real use of
the io_kiocb ref will initialize it to at least 2.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index cdd9873edfe3..4f13b3371156 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -141,6 +141,7 @@ struct io_kiocb {
 	struct io_ring_ctx	*ctx;
 	struct list_head	list;
 	unsigned int		flags;
+	refcount_t		refs;
 #define REQ_F_FORCE_NONBLOCK	1	/* inline submission attempt */
 #define REQ_F_IOPOLL_COMPLETED	2	/* polled IO has completed */
 #define REQ_F_IOPOLL_EAGAIN	4	/* submission got EAGAIN */
@@ -322,6 +323,7 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 	if (req) {
 		req->ctx = ctx;
 		req->flags = 0;
+		refcount_set(&req->refs, 0);
 		return req;
 	}
 
@@ -341,8 +343,10 @@ static void io_free_req_many(struct io_ring_ctx *ctx, void **reqs, int *nr)
 
 static void io_free_req(struct io_kiocb *req)
 {
-	io_ring_drop_ctx_refs(req->ctx, 1);
-	kmem_cache_free(req_cachep, req);
+	if (!refcount_read(&req->refs) || refcount_dec_and_test(&req->refs)) {
+		io_ring_drop_ctx_refs(req->ctx, 1);
+		kmem_cache_free(req_cachep, req);
+	}
 }
 
 /*
-- 
2.17.1