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 <koverstreet@google.com>
Cc: Zach Brown <zab@redhat.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Asai Thambi S P <asamymuthupa@micron.com>
Cc: Selvan Mani <smani@micron.com>
Cc: Sam Bradshaw <sbradshaw@micron.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/aio.c b/fs/aio.c
index 986ff30..5d7dad3 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1159,7 +1159,7 @@
 		}
 	}
 
-	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;
@@ -1281,10 +1281,13 @@
 
 	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;