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

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Message-ID: <20130222051048.GC13667@thunk.org>
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
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