linux-kernel - Re: [PATCH v3 1/3] lib: bitmap: introduce bitmap_print_to

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Date:   Thu, 3 Jun 2021 12:50:41 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Tian Tao <tiantao6@...ilicon.com>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        jonathan.cameron@...wei.com, song.bao.hua@...ilicon.com,
        Randy Dunlap <rdunlap@...radead.org>,
        Stefano Brivio <sbrivio@...hat.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        "Ma, Jianpeng" <jianpeng.ma@...el.com>,
        Yury Norov <yury.norov@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH v3 1/3] lib: bitmap: introduce bitmap_print_to_buf

On Thu, Jun 03, 2021 at 05:22:40PM +0800, Tian Tao wrote:
> New API bitmap_print_to_buf() with bin_attribute to avoid maskp
> exceeding PAGE_SIZE. bitmap_print_to_pagebuf() is a special case
> of bitmap_print_to_buf(), so in bitmap_print_to_pagebuf() call
> bitmap_print_to_buf().

...

>  /**
> + * bitmap_print_to_buf - convert bitmap to list or hex format ASCII string
> + * @list: indicates whether the bitmap must be list
> + * @buf: the kernel space buffer to read to
> + * @maskp: pointer to bitmap to convert
> + * @nmaskbits: size of bitmap, in bits
> + * @off: offset in data buffer below
> + * @count: the maximum number of bytes to print
> + *
> + * The role of bitmap_print_to_buf() and bitmap_print_to_pagebuf() is
> + * the same, the difference is that buf of bitmap_print_to_buf()
> + * can be more than one pagesize.
> + */
> +int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> +			int nmaskbits, loff_t off, size_t count)
> +{
> +	const char *fmt = list ? "%*pbl\n" : "%*pb\n";
> +	ssize_t size;
> +	void *data;
> +
> +	if (off == LLONG_MAX && count == PAGE_SIZE - offset_in_page(buf))
> +		return scnprintf(buf, count, fmt, nmaskbits, maskp);
> +
> +	data = kasprintf(GFP_KERNEL, fmt, nmaskbits, maskp);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	size = memory_read_from_buffer(buf, count, &off, data, strlen(data) + 1);

Are you sure you have put parameters in the correct order?

> +	kfree(data);
> +
> +	return size;
> +}

I guess you have to provide the test case(s).

-- 
With Best Regards,
Andy Shevchenko