linux-ext4 - Re: Beginner questions about ext4

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Message-ID: <CACyNnZPnzEbcFj69+fGjm1rkLay51WTXFMqr25AOzY3vtvegpw@mail.gmail.com>
Date:	Mon, 15 Jul 2013 18:09:03 +0200
From:	Felipe Monteiro de Carvalho <felipemonteiro.carvalho@...il.com>
To:	"Theodore Ts'o" <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Beginner questions about ext4

Hello,

Thanks. Now I think that I am getting closer to something more concrete.

My superblock says:

superblock^.s_blocks_per_group = 32768
superblock^.s_inodes_per_group = 8080
superblock^.s_log_block_size = 2 -> so each block has 4k bytes

And when reading the root "/"  I obtain the following information for
the directory /bin/ : inode=8081

So I calculate that it should have:
groupnr=1 (because it is above 8080 inodes per group)
offset for groupnr 1 --> 4k * 32768 = 0x8000000

But I have utilized a hex editor (oh boy, it was hard to find one that
would read files over 4GB....) And the directory listing of /bin/ is
located in aprox. near 0x21B0000

As if each block group would have a size of 0x2000000 .... but this
size would be valid I would expect if
superblock^.s_blocks_per_group=8192 ...

Any idea what I missed here that the calculations went wrong?

thanks,
-- 
Felipe Monteiro de Carvalho
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