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Date: Wed, 29 Nov 2006 01:39:22 -0800
From: Andrew Morton <akpm@osdl.org>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Mingming Cao <cmm@us.ibm.com>, Hugh Dickins <hugh@veritas.com>,
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       "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Subject: Re: Boot failure with ext2 and initrds
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On Wed, 29 Nov 2006 09:20:24 +0000
Russell King <rmk+lkml@arm.linux.org.uk> wrote:

> What I'm looking for is confirmation of the semantics of
> find_next_zero_bit()

What are the existing semantics?  I see no documentation in any of the
architectures I've looked at.  That's my point.

>From a quick read of fs/ext2/balloc.c

	ext2_find_next_zero_bit(base, size, offset)

appears to expect that base is the start of the memory buffer, size is the
number of bits at *base and offset is the bit at which to start the search,
relative to base.  If a zero bit is found it will return the offset of that
bit relative to base.  It will return some number greater than `size' if no
zero-bit was found.  

Whether that's how all the implementors interpreted it is anyone's guess. 
Presumably the architectures all do roughly the same thing.

> <extremely frustrated>

Well likewise.  It appears that nobody (and about 20 people have
implemented these things) could be bothered getting off ass and documenting
the pathetic thing.

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