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Date: Thu, 17 Jun 2021 12:47:20 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Barry Song <song.bao.hua@...ilicon.com>
Cc: andriy.shevchenko@...ux.intel.com, linux-kernel@...r.kernel.org,
linux@...musvillemoes.dk, rafael@...nel.org,
akpm@...ux-foundation.org, rdunlap@...radead.org,
agordeev@...ux.ibm.com, sbrivio@...hat.com, jianpeng.ma@...el.com,
yury.norov@...il.com, valentin.schneider@....com,
peterz@...radead.org, bristot@...hat.com, guodong.xu@...aro.org,
tangchengchang@...wei.com, prime.zeng@...ilicon.com,
yangyicong@...wei.com, tim.c.chen@...ux.intel.com,
tiantao6@...ilicon.com, Jonathan.Cameron@...wei.com,
linuxarm@...wei.com
Subject: Re: [PATCH v4 1/4] lib: bitmap: introduce bitmap_print_to_buf
On Thu, Jun 17, 2021 at 10:19:07PM +1200, Barry Song wrote:
> From: Tian Tao <tiantao6@...ilicon.com>
>
> New API bitmap_print_to_buf() with bin_attribute to avoid maskp
> exceeding PAGE_SIZE.
I can not parse this sentance at all, sorry.
What does a "bin_attribute" mean to this change? What does PAGE_SIZE
have to do with anything at all here?
> bitmap_print_to_pagebuf() is a special case
> of bitmap_print_to_buf(), so in bitmap_print_to_pagebuf() call
> bitmap_print_to_buf().
Again, I can not parse this, sorry. Can you please try writing this in
a different way to be more descriptive?
>
> Signed-off-by: Tian Tao <tiantao6@...ilicon.com>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@...wei.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Cc: Randy Dunlap <rdunlap@...radead.org>
> Cc: Stefano Brivio <sbrivio@...hat.com>
> Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
> Cc: "Ma, Jianpeng" <jianpeng.ma@...el.com>
> Cc: Yury Norov <yury.norov@...il.com>
> Cc: Valentin Schneider <valentin.schneider@....com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
> ---
> include/linux/bitmap.h | 2 ++
> include/linux/cpumask.h | 21 +++++++++++++++++++++
> lib/bitmap.c | 37 +++++++++++++++++++++++++++++++++++--
> 3 files changed, 58 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index a36cfcec4e77..0de6effa2797 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -226,6 +226,8 @@ void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int n
> unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, unsigned int nbits);
> int bitmap_print_to_pagebuf(bool list, char *buf,
> const unsigned long *maskp, int nmaskbits);
> +int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> + int nmaskbits, loff_t off, size_t count);
>
> #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
> #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index bfc4690de4f4..1bef69e4b950 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -983,6 +983,27 @@ cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask)
> nr_cpu_ids);
> }
>
> +/**
> + * cpumap_print_to_buf - copies the cpumask into the buffer either
> + * as comma-separated list of cpus or hex values of cpumask
How do you choose between a comma or a hex value?
> + * @list: indicates whether the cpumap must be list
Should this be the thing that determines a comma or not? If true does
that mean a comma? Or if false? Can you please document this?
> + * @mask: the cpumask to copy
> + * @buf: the buffer to copy into
> + * @off: in the string from which we are copying, We copy to @buf + off
> + * @count: the maximum number of bytes to print
> + *
> + * The role of cpumap_print_to_buf() and cpumap_print_to_pagebuf() is
> + * the same, the difference is that buf of bitmap_print_to_buf()
> + * can be more than one pagesize.
> + */
> +static inline ssize_t
> +cpumap_print_to_buf(bool list, char *buf, const struct cpumask *mask,
> + loff_t off, size_t count)
> +{
> + return bitmap_print_to_buf(list, buf, cpumask_bits(mask),
> + nr_cpu_ids, off, count);
> +}
> +
> #if NR_CPUS <= BITS_PER_LONG
> #define CPU_MASK_ALL \
> (cpumask_t) { { \
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 74ceb02f45e3..ed7ef6e2edca 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -461,6 +461,40 @@ int bitmap_parse_user(const char __user *ubuf,
> }
> EXPORT_SYMBOL(bitmap_parse_user);
>
> +/**
> + * 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.
"pagesize" does not make sense here.
Why does PAGE_SIZE have anything to do with this function at all?
> + */
> +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);
I do not understand this check, can you please comment why you are doing
it this way?
thanks,
greg k-h
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