linux-kernel - Re: [PATCH 1/3] bitmap: generalize node

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Message-Id: <20250604143442.37635ce63e50a7425a390c2e@linux-foundation.org>
Date: Wed, 4 Jun 2025 14:34:42 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yury Norov <yury.norov@...il.com>
Cc: linux-kernel@...r.kernel.org, Rasmus Villemoes
 <linux@...musvillemoes.dk>, John Stultz <jstultz@...gle.com>, Thomas
 Gleixner <tglx@...utronix.de>, Stephen Boyd <sboyd@...nel.org>
Subject: Re: [PATCH 1/3] bitmap: generalize node_random()

On Wed,  4 Jun 2025 17:21:21 -0400 Yury Norov <yury.norov@...il.com> wrote:

> Generalize node_random and make it available to general bitmaps and
> cpumasks users.

Seems sensible.

> --- a/lib/find_bit.c
> +++ b/lib/find_bit.c
>  
> +unsigned long find_random_bit(const unsigned long *addr, unsigned long size)
> +{
> +	int w = bitmap_weight(addr, size);
> +
> +	switch (w) {
> +	case 0:
> +		return size;
> +	case 1:
> +		return find_first_bit(addr, size);

Is the `1' special case useful?  The `default' case should still work OK?

> +	default:
> +		return find_nth_bit(addr, size, get_random_u32_below(w));
> +	}
> +}
> +EXPORT_SYMBOL(find_random_bit);

Some kerneldoc, please?

Of course, the hard-coding of get_random_u32_below() might be
unsuitable for some future potential callers but we can deal with that
if it ever occurs.