linux-ext4 - Re: [RFC][PATCH] Set JBD2_FEATURE_INCOMPAT_64BIT on filesystems larger than 32-bit blocks (take 2).

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Date:	Tue, 05 Jun 2007 18:07:30 +0200
From:	Laurent Vivier <Laurent.Vivier@...l.net>
To:	"Jose R. Santos" <jrs@...ibm.com>
Cc:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>, cmm@...ibm.com,
	Andreas Dilger <adilger@...sterfs.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [RFC][PATCH] Set JBD2_FEATURE_INCOMPAT_64BIT on filesystems larger
 than 32-bit blocks (take 2).

Jose R. Santos wrote:
> On Tue, 05 Jun 2007 16:03:44 +0200
> Laurent Vivier <Laurent.Vivier@...l.net> wrote:
>> Jose R. Santos wrote:
>>> Hi Laurent,
>>>
>>> In this particular case though, the value of s_blocks_count_hi should not be
>>> uses on its own.  The correct way would be to use ext4_blocks_count() which
>>> already does the endian conversion.  If you think the code could confuse
>>> people as to how to access the data in s_blocks_count_hi, wouldn't hiding it
>>> through the use of a macro make more sense than doing an unnecessary endian
>>> conversion?
>>>
>> Yes, I think the code could confuse people, but I don't think defining "Yet
>> Another Macro" is a good choice (IMHO).
>>
>> I think we can resolve this (non-)issue by two ways:
>> - using le32_to_cpu() (but I agree it does an unnecessary endian conversion on
>> big-endian systems)
> 
> I just think that adding extra instructions for the sake of slightly
> better code readability is wrong, especially when the value
> s_blocks_count_hi should not be used on its own.
> 
>> - put a comment on the line (but are we allowed to put comments in kernel source
>> code... ;-) )
> 
> One advantage of a macro here is that we would make the code more
> explicit and should be able to eliminate the need for those 4 lines of
> comments that this patch adds.

IMHO, you should do as _you_ think it is better... but as Mingming did the first
comment perhaps she can explain what she thought.

Regards,
Laurent
-- 
------------- Laurent.Vivier@...l.net  --------------
       "Any sufficiently advanced technology is
  indistinguishable from magic." - Arthur C. Clarke


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