linux-ext4 - Re: [PATCH] ext4: simplify 32bit calculation of lblk

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Message-ID: <CA+tQmHA_3_Oc-0AQ0a29DTwU4mkEqhOiAE6gXa4Ly4gZGpn5Vw@mail.gmail.com>
Date:   Wed, 5 Apr 2023 16:47:59 +0800
From:   chi wu <wuchi.zero@...il.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     tytso@....edu, adilger.kernel@...ger.ca, ojaswin@...ux.ibm.com,
        ritesh.list@...il.com, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ext4: simplify 32bit calculation of lblk

Christoph Hellwig <hch@...radead.org> 于2023年4月5日周三 13:40写道：
>
> On Mon, Apr 03, 2023 at 09:53:04PM +0800, wuchi wrote:
> > -                     if (block > ext_block)
> > -                             return ext_pblk + (block - ext_block);
> > -                     else
> > -                             return ext_pblk - (ext_block - block);
> > +                     return ext_pblk + ((signed long long)block - (signed long long)ext_block);
>
> And what exactly is the value add here, except for turning an easy
> to parse statement into a complex expression using casts?
>
Yes，it will be more complex. the original intention is to reduce the
conditional branch.

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