linux-ext4 - Re: [PATCH] e2fsprogs: Handle rec_len correctly for 64KB blocksize

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Message-ID: <20071112095245.GA1465@duck.suse.cz>
Date:	Mon, 12 Nov 2007 10:52:45 +0100
From:	Jan Kara <jack@...e.cz>
To:	Theodore Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] e2fsprogs: Handle rec_len correctly for 64KB blocksize

On Sat 10-11-07 19:37:03, Theodore Tso wrote:
> On Wed, Nov 07, 2007 at 05:09:39PM +0100, Jan Kara wrote:
> 
> > Subject: Support for 64KB blocksize in ext2-4 directories.
> > 
> > When block size is 64KB, we have to take care that rec_len does not overflow.
> > Kernel stores 0xffff in case 0x10000 should be stored - perform appropriate
> > conversion when reading from / writing to disk.
> 
> NACK.  You can't do the conversion in the reader/writer routines
> because the fundamentally rec_len is only a 16 bit field.  So when you
> read a directory block where the rec_len field is encoded as 0xFFFF,
> and you translate it to 0x10000, when you assign it to
> dirent->rec_len, the 0x10000 gets chopped off and rec_len gets a value
> of zero.  Did you test this patch before submitting it?
  Argh, stupid me. I've just tested that I didn't break anything for normal
block size and thought that I cannot make mistake in such a simple thing
;).

> The only way to do this is to find all of the places that reference
> rec_len, and do the check there.
  Yes.. Thanks for having look.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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