aio: kill ki_key

ki_key wasn't actually used for anything previously - it was always 0.
Drop it to trim struct kiocb a bit.

Signed-off-by: Kent Overstreet <[e-mail]>
Cc: Zach Brown <[e-mail]>
Cc: Felipe Balbi <[e-mail]>
Cc: Greg Kroah-Hartman <[e-mail]>
Cc: Mark Fasheh <[e-mail]>
Cc: Joel Becker <[e-mail]>
Cc: Rusty Russell <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Asai Thambi S P <[e-mail]>
Cc: Selvan Mani <[e-mail]>
Cc: Sam Bradshaw <[e-mail]>
Cc: Jeff Moyer <[e-mail]>
Cc: Al Viro <[e-mail]>
Cc: Benjamin LaHaise <[e-mail]>
Reviewed-by: "Theodore Ts'o" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/aio.c

···
 		}
 	}
 
-	ret = put_user(req->ki_key, &user_iocb->aio_key);
+	ret = put_user(KIOCB_KEY, &user_iocb->aio_key);
 	if (unlikely(ret)) {
 		pr_debug("EFAULT: aio_key\n");
 		goto out_put_req;
···
 
 	assert_spin_locked(&ctx->ctx_lock);
 
+	if (key != KIOCB_KEY)
+		return NULL;
+
 	/* TODO: use a hash or array, this sucks. */
 	list_for_each(pos, &ctx->active_reqs) {
 		struct kiocb *kiocb = list_kiocb(pos);
-		if (kiocb->ki_obj.user == iocb && kiocb->ki_key == key)
+		if (kiocb->ki_obj.user == iocb)
 			return kiocb;
 	}
 	return NULL;

include/linux/aio.h

···
 struct kioctx;
 struct kiocb;
 
-#define KIOCB_SYNC_KEY		(~0U)
+#define KIOCB_KEY		0
 
 /*
  * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either
···
  */
 struct kiocb {
 	atomic_t		ki_users;
-	unsigned		ki_key;		/* id of this request */
 
 	struct file		*ki_filp;
-	struct kioctx		*ki_ctx;	/* may be NULL for sync ops */
+	struct kioctx		*ki_ctx;	/* NULL for sync ops */
 	kiocb_cancel_fn		*ki_cancel;
 	ssize_t			(*ki_retry)(struct kiocb *);
 	void			(*ki_dtor)(struct kiocb *);
···
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
 {
-	return kiocb->ki_key == KIOCB_SYNC_KEY;
+	return kiocb->ki_ctx == NULL;
 }
 
 static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 {
 	*kiocb = (struct kiocb) {
 			.ki_users = ATOMIC_INIT(1),
-			.ki_key = KIOCB_SYNC_KEY,
+			.ki_ctx = NULL,
 			.ki_filp = filp,
 			.ki_obj.tsk = current,
 		};