linux-ext4 - Re: [PATCH 1/2] ext4: reduce computation of overhead during resize

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Message-ID: <23CB6B29-F40D-4359-B7E3-85515217D45B@amazon.com>
Date:   Fri, 15 Jul 2022 23:52:32 +0000
From:   "Kiselev, Oleg" <okiselev@...zon.com>
To:     Jan Kara <jack@...e.cz>
CC:     "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
        Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 1/2] ext4: reduce computation of overhead during resize


> On Jul 15, 2022, at 2:27 AM, Jan Kara <jack@...e.cz> wrote:
> 
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
> 
> 
> 
> On Thu 14-07-22 19:53:38, Kiselev, Oleg wrote:
>>> 
>>>> +       sbi->s_overhead += overhead;
>>>> +       es->s_overhead_clusters = cpu_to_le32((unsigned long) sbi->s_overhead);
>>>                                               ^^^ the typecast looks
>>> bogus here...
>> 
>> This cast is the reverse of le32_to_cpu() cast done in fs/ext4/super.c:__ext4_fill_super():
>>        sbi->s_overhead = le32_to_cpu(es->s_overhead_clusters);
>> And follows the logic of casting done in fs/ext4/ioctl.c:set_overhead() and fs/ext4/ioctl.c:ext4_update_overhead().
> 
> I didn't mean the cpu_to_le32() call but rather the (unsigned long) part.
> That is pointless because sbi->s_overhead is already 'unsigned long' and
> even if it was not, I have hard time seeing a reason why would casting to
> unsigned long make any difference here.

Got it.  You are right.  The indent of your comment got mangled by mail, so it looked like it was directed to cpu_to_ie32()!  

> 
>                                                                        Honza
> --
> Jan Kara <jack@...e.com>
> SUSE Labs, CR