Re: ext4 features (checksums)

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

Ar Maw, 2006-07-04 am 09:31 +1000, ysgrifennodd Neil Brown:
> It's been some years that I've felt that most 'logical volume
> management' really belongs in the filesystem.
> Why have a dm that chops devices up in to segments and assembles them to
> look like a big device, only to have that big device chopped up and
> presented as files.  Seems like double handling to me.

Because the interface model is wrong ?

Various people have long said the model actually should look rather more
like

fs to block:
	handle = alloc_extent(near_handle*, info)
	write_extent(handle, buffer, offset, length)
	read_extent(handle, buffer, offset, length)
	free_extent(handle)

(probably with resize_extent)

This makes LVM, remapping, checksumming and the like all naturally slip
out of the fs but not into the block layer.


[Many very good points snipped]
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