linux-kernel - Re: [TOMOYO #12 (2.6.28-rc2-mm1) 05/11] Memory and pathname management functions.

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Message-ID: <4919277F.9050206@nttdata.co.jp>
Date:	Tue, 11 Nov 2008 15:34:39 +0900
From:	Kentaro Takeda <takedakn@...data.co.jp>
To:	akpm@...ux-foundation.org
CC:	haradats@...data.co.jp, linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, penguin-kernel@...ove.SAKURA.ne.jp
Subject: Re: [TOMOYO #12 (2.6.28-rc2-mm1) 05/11] Memory and pathname management
 functions.

Andrew Morton wrote:
>>> Note that I said "kmalloc", not "kzalloc".  This function zeroes
>>> everything all the time, and surely that is not necessary.  It's just a
>>> waste of CPU time.
>>>
>> Callers of tmy_alloc assume that allocated memory is zeroed.
> 
> That isn't the point.  For programmer convenience we could make
> __alloc_pages() and kmalloc() zero all the memory too.  But we don't
> because it is slow.
Are you saying "make the callers of tmy_alloc() tolerable with
uninitialized memory"?

>>>> +/**
>>>> + * tmy_read_memory_counter - Check for memory usage.
>>>> + *
>>>> + * @head: Pointer to "struct tmy_io_buffer".
>>>> + *
>>>> + * Returns memory usage.
>>> In what units?  Megabytes?
>>>
>> In bytes.
> 
> Let me rephrase:
> 
> The comment over tmy_read_memory_counter() fails to tell the reader
> what units are used for the return value.  It should do so.
I see. Replaced "Check for memory usage." by "Check for memory usage in bytes".
Thanks.

>> Creating pseudo files for each variables is fine, though I don't see
>> advantage by changing from
>> "echo Shared: 16777216 > /sys/kernel/security/tomoyo/meminfo" to
>> "echo 16777216 > /sys/kernel/security/tomoyo/quota/shared_memory".
> 
> Well for starters, the existing interface is ugly as sin and will make
> kernel developers unhappy.
> 
> There is a pretty strict one-value-per-file rule in sysfs files, and
> "multiple tagged values in one file" violates that a lot.
/sys/kernel/security/ is not sysfs but securityfs.
Does "one-value-per-file rule" also apply to securityfs?

Regards,


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