linux-kernel - Re: [PATCH v5 2/2] lib/test-string_helpers.c: add string_get

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Date:	Wed, 21 Oct 2015 12:19:13 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	James Bottomley <JBottomley@...n.com>,
	linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: Re: [PATCH v5 2/2] lib/test-string_helpers.c: add string_get_size() tests

On Thu, Sep 17 2015, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:

> +
> +static __init void test_string_get_size(void)
> +{
> +	test_string_get_size_one(16384, 512, STRING_UNITS_2, "8.00 MiB");
> +	test_string_get_size_one(8192, 4096, STRING_UNITS_10, "32.7 MB");

This is a little late, but I just noticed that string_get_size with
STRING_UNITS_10, block size >= 1024 and sufficiently large size seems to
be broken. Yes, 32.7 MB is what it produces, but is it what it should
give? 8192*4096 = 33554432, so I'd expect "33.5 MB". It does give that
when we pass size=65536 and block_size=512; a combination with the same
product.

I think the problem is that the remainder coming out of the while
(blk_size >= divisor[units]) loop is dropped on the floor in the
subsequent size > exp case - but I'm too lazy right now to figure out how
to fix it.

Rasmus
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