linux-kernel - Re: [PATCH v3 2/2] lib/test-string_helpers.c: add string_get

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Message-ID: <87y4g8wtjo.fsf@rasmusvillemoes.dk>
Date:	Tue, 15 Sep 2015 00:00:11 +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 v3 2/2] lib/test-string_helpers.c: add string_get_size() tests

On Mon, Sep 14 2015, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:

> +static __init void test_string_get_size_one(u64 size, u64 blk_size,
> +					    const enum string_size_units units,
> +					    const char *exp_result)
> +{
> +	char buf[256];
> +
> +	string_get_size(size, blk_size, units, buf, sizeof(buf));
> +	if (!strncmp(buf, exp_result, min(sizeof(buf), strlen(exp_result))))
> +		return;

Nits: It probably makes sense to also test that string_get_size
'\0'-terminates the buffer, so I'd spell this

  if (!memcmp(buf, exp_result, min(sizeof(buf), strlen(exp_result)+1)))

With a generous stack buffer, that min() will always evaluate to the
strlen(exp_result)+1. On that note: Maybe 256 is a bit excessive. I
don't think this will run very deep in the kernel stack, but the code might
get copy-pasted somewhere else. 16 should be plenty.

> +	pr_warn("Test 'test_string_get_size_one' failed!\n");
> +	pr_warn("string_get_size(size = %llu, blk_size = %llu, units = %d\n",
> +		size, blk_size, units);

[There's probably no pretty way of getting from units to a text
representation, but it's slightly annoying to have to check the source
for the enum definition to figure out what units=0 or units=1 means.]

> +	pr_warn("expected: %s, got %s\n", exp_result, buf);

In case we failed to '\0'-terminate buf, we might want to print it with
"%.*s", (int)sizeof(buf), buf. But maybe I'm just overly paranoid.

Rasmus
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