linux-ext4 - Re: [PATCH] ext4: fix free clusters calculation in bigalloc filesystem

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Date:	Fri, 22 Feb 2013 08:57:47 +0100 (CET)
From:	Lukáš Czerner <lczerner@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
cc:	Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH] ext4: fix free clusters calculation in bigalloc
 filesystem

On Fri, 22 Feb 2013, Theodore Ts'o wrote:

> Date: Fri, 22 Feb 2013 00:10:48 -0500
> From: Theodore Ts'o <tytso@....edu>
> To: Lukas Czerner <lczerner@...hat.com>
> Cc: linux-ext4@...r.kernel.org
> Subject: Re: [PATCH] ext4: fix free clusters calculation in bigalloc
>     filesystem
> 
> On Thu, Feb 21, 2013 at 09:01:05AM +0100, Lukas Czerner wrote:
> > 
> > Moreover when calculating number of root clusters we should be using
> > macro EXT4_NUM_B2C() instead of EXT4_C2B() otherwise the result will
> > usually be off by one.
> 
> That should be "instead of EXT4_B2C()", and I don't think this is
> true, since the number of blocks should always be a multiple of the
> cluster ratio.  So the use of EXT4_B2C() is a bit of an optimization
> (it avoids an add and mask operation), but it's probably not a
> measurable optimizatoin in practice.
> 
> 							- Ted

Oh right it was EXT4_B2C(), I'll update the description. Even though
it should always be a multiple of cluster ratio it's really bad
precedence for the use of EXT4_B2C() since it is confusing enough
as it is with blocks/clusters.

I'll resend.

-Lukas
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