[PATCH 16/19] io_uring: add io_kiocb ref count

[Jens Axboe]

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.

Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Jens Axboe <ax...@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 cd7ff2643292..dc5667c53c55 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -164,6 +164,7 @@ 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_FIXED_FILE       4       /* ctx owns file */
@@ -353,6 +354,7 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
 
        req->ctx = ctx;
        req->flags = 0;
+       refcount_set(&req->refs, 0);
        return req;
 out:
        io_ring_drop_ctx_refs(ctx, 1);
@@ -370,8 +372,10 @@ 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