Date: Wed, 1 Mar 2006 17:51:48 -0800
From: Andrew Morton <akpm@osdl.org>
To: Badari Pulavarty <pbadari@us.ibm.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/4] change buffer_head.b_size to size_t
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Badari Pulavarty <pbadari@us.ibm.com> wrote:
>
> + * Historically, a buffer_head was used to map a single block
> + * within a page, and of course as the unit of I/O through the
> + * filesystem and block layers.  Nowadays the basic I/O unit
> + * is the bio, and buffer_heads are used for extracting block
> + * mappings (via a get_block_t call), for tracking state within
> + * a page (via a page_mapping) and for wrapping bio submission
> + * for backward compatibility reasons (e.g. submit_bh).

Well kinda.  A buffer_head remains the kernel's basic abstraction for a
"disk block".  We cannot replace that with `struct page' (size isn't
flexible) nor of course with `struct bio'.

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