Re: [PATCH 1/4] seq_file: don't call bitmap_scnprintf_len()

From: Lai Jiangshan
Date: Tue Oct 14 2008 - 21:37:35 EST


Lai Jiangshan wrote:
> Alexey Dobriyan wrote:
>> On Sun, Oct 12, 2008 at 05:29:17PM +0800, Lai Jiangshan wrote:
>>> "m->count + len < m->size" is true commonly, so bitmap_scnprintf()
>>> is commonly called. this fix saves a call to bitmap_scnprintf_len().
>> This saves a call if seq buffer is already full which is not a common
>> situation, so you're optimising for rare situations and adding branch
>> for common ones.
>
> Hi Alexey
>
> I think this saves a call if seq buffer is _not_ full after called.
>
> since calling bitmap_scnprintf() is the common situation. so we use
> the return value of bitmap_scnprintf() instead of bitmap_scnprintf_len().
>
> In old code bitmap_scnprintf_len() and bitmap_scnprintf() must be called
> commonly.
>
> Thanks Lai.

Hi, Alexey,

Have noticed this comment? I hold my ground, ;-)
And seq_cpumask_list(), seq_nodemask_list() are needed for print mask
safely, Should I send independent patches for them if we can't
make an agreement about this fix.

Lai

>
>>> --- a/fs/seq_file.c
>>> +++ b/fs/seq_file.c
>>> @@ -452,17 +452,18 @@ int seq_dentry(struct seq_file *m, struct dentry *dentry, char *esc)
>>>
>>> int seq_bitmap(struct seq_file *m, unsigned long *bits, unsigned int nr_bits)
>>> {
>>> - size_t len = bitmap_scnprintf_len(nr_bits);
>>> -
>>> - if (m->count + len < m->size) {
>>> - bitmap_scnprintf(m->buf + m->count, m->size - m->count,
>>> - bits, nr_bits);
>>> - m->count += len;
>>> - return 0;
>>> + if (m->count < m->size) {
>>> + int len = bitmap_scnprintf(m->buf + m->count,
>>> + m->size - m->count, bits, nr_bits);
>>> + if (m->count + len < m->size) {
>>> + m->count += len;
>>> + return 0;
>>> + }
>>> }
>>> m->count = m->size;
>>> return -1;
>>> }
>>> +EXPORT_SYMBOL(seq_bitmap);
>> Modular users, where are they?
>>
>>
>>
>
>


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