Re: [PATCH 1/4] change buffer_head.b_size to size_t

From: Andrew Morton
Date: Wed Mar 01 2006 - 20:47:20 EST


Badari Pulavarty <pbadari@xxxxxxxxxx> 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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