io_uring: add io_kiocb ref count

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: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0a4caedf82c1e476c4dc00e4ddbc898259cdb3b2..d2a3a1bc85cc053a687fd7760f78038cb88c4f87 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -184,6 +184,7 @@ 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 */
@@ -377,6 +378,7 @@ 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);
@@ -394,8 +396,10 @@ 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);
+       }
 }
 
 /*