linux-ext4 - Re: [PATCH] mke2fs: Disallow bigalloc with with bs

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Message-ID: <20130403143554.GA13668@thunk.org>
Date:	Wed, 3 Apr 2013 10:35:54 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Lukas Czerner <lczerner@...hat.com>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] mke2fs: Disallow bigalloc with with bs < 4096

On Wed, Apr 03, 2013 at 03:51:39PM +0200, Lukas Czerner wrote:
> Currently there is nothing preventing user to create file system with
> bigalloc feature enabled and block size smaller than 4096 Bytes. However
> such combination does not make much sense at all because the whole point
> of bigalloc is to have bigger allocation units.
> 
> This patch disallow such combination.

This makes sense by default but I do see a point in allowing it for
testing purposes --- specifically, it allows us to verify that
bigalloc works on architectures such as PowerPC and Itanium where page
size is greater than the 4k block size.  So maybe a developer mode set
via mke2fs.conf?

Another option would be to enforce that we only support bigalloc file
systems where the blocksize == pagesize, but that means we wouldn't be
able to mount 4k bigalloc file systems on architectures with a 8k or
16k page size.

						- Ted
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