io_uring: fix unexpected placement on same size resizing

There might be many reasons why a user is resizing a ring, e.g. moving
to huge pages or for some memory compaction using IORING_SETUP_NO_MMAP.
Don't bypass resizing, the user will definitely be surprised seeing 0
while the rings weren't actually moved to a new place.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: isilence

io_uring/register.c

@@ -421,13 +421,6 @@ static int io_register_resize_rings(struct io_ring_ctx *ctx, void __user *arg)
 	if (unlikely(ret))
 		return ret;
 
-	/* nothing to do, but copy params back */
-	if (p.sq_entries == ctx->sq_entries && p.cq_entries == ctx->cq_entries) {
-		if (copy_to_user(arg, &p, sizeof(p)))
-			return -EFAULT;
-		return 0;
-	}
-
 	size = rings_size(p.flags, p.sq_entries, p.cq_entries,
 				&sq_array_offset);
 	if (size == SIZE_MAX)