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Date: Fri, 12 Jan 2024 15:49:59 +0300
From: Dan Carpenter <dan.carpenter@linaro.org>
To: David Laight <David.Laight@aculab.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	'Andy Shevchenko' <andriy.shevchenko@linux.intel.com>,
	'Andrew Morton' <akpm@linux-foundation.org>,
	"'Matthew Wilcox (Oracle)'" <willy@infradead.org>,
	'Christoph Hellwig' <hch@infradead.org>,
	"'Jason A. Donenfeld'" <Jason@zx2c4.com>
Subject: Re: [PATCH next v4 1/5] minmax: Add umin(a, b) and umax(a, b)
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 <41d93ca827a248698ec64bf57e0c05a5@AcuMS.aculab.com>
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On Mon, Sep 18, 2023 at 08:16:30AM +0000, David Laight wrote:
> +/**
> + * umin - return minimum of two non-negative values
> + *   Signed types are zero extended to match a larger unsigned type.
> + * @x: first value
> + * @y: second value
> + */
> +#define umin(x, y)	\
> +	__careful_cmp((x) + 0u + 0ul + 0ull, (y) + 0u + 0ul + 0ull, <)

Why do we match "a larger unsigned type" instead of ULL_MAX?  Presumably
it helps performance somehow...  I agree that it's probably fine but I
would be more comfortable if it skipped UINT_MAX and jumped directly to
ULONG_MAX.  These days 4 gigs is small potatoes.  The vmalloc() function
can allocate 4G so we've had integer overflow bugs with this before.

regards,
dan carpenter