linux-kernel - Re: [PATCH 01/32] cpumask: always use nr_cpu_ids in formatting and parsing functions

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Date:	Tue, 27 Jan 2015 10:12:20 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Tejun Heo <tj@...nel.org>, akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 01/32] cpumask: always use nr_cpu_ids in formatting and parsing functions

Tejun Heo <tj@...nel.org> writes:
> Currently, the formatting and parsing functions in cpumask.h use
> nr_cpumask_bits like other cpumask functions; however, nr_cpumask_bits
> is either NR_CPUS or nr_cpu_ids depending on CONFIG_CPUMASK_OFFSTACK.
> This leads to inconsistent behaviors.

Acked-by: Rusty Russell <rusty@...tcorp.com.au>

Thanks!
Rusty.


>
> With CONFIG_NR_CPUS=512 and !CONFIG_CPUMASK_OFFSTACK
>
>   # cat /sys/devices/virtual/net/lo/queues/rx-0/rps_cpus
>   00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000
>   # cat /proc/self/status | grep Cpus_allowed:
>   Cpus_allowed:   f
>
> With CONFIG_NR_CPUS=1024 and CONFIG_CPUMASK_OFFSTACK (fedora default)
>
>   # cat /sys/devices/virtual/net/lo/queues/rx-0/rps_cpus
>   0
>   # cat /proc/self/status | grep Cpus_allowed:
>   Cpus_allowed:   f
>
> Note that /proc/self/status is always using nr_cpu_ids regardless of
> config.  This is because seq cpumask formattings functions always use
> nr_cpu_ids.
>
> Given that the same output fields may switch between the two forms,
> converging on nr_cpu_ids always isn't too likely to surprise userland.
> This patch updates the formatting and parsing functions in cpumask.h
> to always use nr_cpu_ids.  There's no point in dealing with CPUs which
> aren't even possible on the machine.
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> ---
> Hello,
>
> Linus, this is the first of the three pre-requisite patches to convert
> the users of the dedicated bitmap formatting functions over to
> '%*pb[l]' formatting.
>
> If this approach is agreed upon, I think it'd be best to route these
> three patches through mainline soon so that subsystem conversion
> patches can pull these in and apply per-subsystem conversion patches.
>
> Thanks.
>
>  include/linux/cpumask.h | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
> index b950e9d..98939d1 100644
> --- a/include/linux/cpumask.h
> +++ b/include/linux/cpumask.h
> @@ -550,7 +550,7 @@ static inline void cpumask_copy(struct cpumask *dstp,
>  static inline int cpumask_scnprintf(char *buf, int len,
>  				    const struct cpumask *srcp)
>  {
> -	return bitmap_scnprintf(buf, len, cpumask_bits(srcp), nr_cpumask_bits);
> +	return bitmap_scnprintf(buf, len, cpumask_bits(srcp), nr_cpu_ids);
>  }
>  
>  /**
> @@ -564,7 +564,7 @@ static inline int cpumask_scnprintf(char *buf, int len,
>  static inline int cpumask_parse_user(const char __user *buf, int len,
>  				     struct cpumask *dstp)
>  {
> -	return bitmap_parse_user(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
> +	return bitmap_parse_user(buf, len, cpumask_bits(dstp), nr_cpu_ids);
>  }
>  
>  /**
> @@ -579,7 +579,7 @@ static inline int cpumask_parselist_user(const char __user *buf, int len,
>  				     struct cpumask *dstp)
>  {
>  	return bitmap_parselist_user(buf, len, cpumask_bits(dstp),
> -							nr_cpumask_bits);
> +				     nr_cpu_ids);
>  }
>  
>  /**
> @@ -595,7 +595,7 @@ static inline int cpulist_scnprintf(char *buf, int len,
>  				    const struct cpumask *srcp)
>  {
>  	return bitmap_scnlistprintf(buf, len, cpumask_bits(srcp),
> -				    nr_cpumask_bits);
> +				    nr_cpu_ids);
>  }
>  
>  /**
> @@ -610,7 +610,7 @@ static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
>  	char *nl = strchr(buf, '\n');
>  	unsigned int len = nl ? (unsigned int)(nl - buf) : strlen(buf);
>  
> -	return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpumask_bits);
> +	return bitmap_parse(buf, len, cpumask_bits(dstp), nr_cpu_ids);
>  }
>  
>  /**
> @@ -622,7 +622,7 @@ static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
>   */
>  static inline int cpulist_parse(const char *buf, struct cpumask *dstp)
>  {
> -	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
> +	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpu_ids);
>  }
>  
>  /**
> @@ -817,7 +817,7 @@ static inline ssize_t
>  cpumap_print_to_pagebuf(bool list, char *buf, const struct cpumask *mask)
>  {
>  	return bitmap_print_to_pagebuf(list, buf, cpumask_bits(mask),
> -				      nr_cpumask_bits);
> +				      nr_cpu_ids);
>  }
>  
>  /*
> -- 
> 2.1.0
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