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List:       evms-devel
Subject:    Re: [Evms-devel] Use of eio Vs bio->private
From:       Kevin Corry <corryk () us ! ibm ! com>
Date:       2002-01-30 15:54:20
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On Wednesday 30 January 2002 09:33, Jim McDonald wrote:
> Hi,
>    I've been playing about with migrating the 2.5-compliant md code to
> EVMS, and was wondering what the reason is for using the eio structure
> rather than using the bio->private to hold the required additional
> information?  Using normal bios would seem to make the migration process
> a lot easier, and look a lot more like the kernel's 2.5 native
> structures.
>
> Cheers,
> Jim.

The eio structure is a "wrapper" for either buffer_head or bio, depending on 
if you are using 2.4 or 2.5. This structure allowed us to completely reuse 
some of the plugins, without any necessary porting from 2.4 to 2.5.

Obviously, however, some of the plugins could not get away with not having 
direct access to the buffer_head structure in 2.4 (md being one example). 
These plugins have to be ported to work with the bio's in 2.5. The bio's 
should be an improvement over buffer_heads, and as you pointed out, might 
have extra fields that these EVMS plugins can make use of.

-Kevin

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