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

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Date:   Thu, 3 Jun 2021 13:37:09 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "tiantao (H)" <tiantao6@...wei.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Tian Tao <tiantao6@...ilicon.com>, 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 07:21:30PM +0800, tiantao (H) wrote:
> 
> 在 2021/6/3 18:49, Greg KH 写道:
> > On Thu, Jun 03, 2021 at 06:33:25PM +0800, tiantao (H) wrote:
> > > 在 2021/6/3 17:50, Andy Shevchenko 写道:
> > > > 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?
> > > yes, I already test it.
> > Great, can you add the test to the patch series as well so that we can
> > make sure it does not break in the future?
> How do I do this?  Do I need to provide a kselftest ?

That would be wonderful, great idea!

thanks,

greg k-h