Re: [PATCH 1/9] mm: add a "struct subpage" type containing a page, offset and length

[Ian Campbell <Ian.Campbell@citrix.com>]

On Mon, 2011-10-10 at 16:55 +0100, Christoph Hellwig wrote:
> On Mon, Oct 10, 2011 at 12:11:33PM +0100, Ian Campbell wrote:
> > A few network drivers currently use skb_frag_struct for this purpose but I have
> > patches which add additional fields and semantics there which these other uses
> > do not want.
> > 
> > A structure for reference sub-page regions seems like a generally useful thing
> > so do so instead of adding a network subsystem specific structure.
> 
> Subpage seems like a fairly bad name.  page_frag would fit into the
> scheme used in a few other places.

ok.

> The brings back the discussion of unifying the various incarnations we
> have of this (biovec, skb frag and there were a few more at times),
> but IIRC one of the sticking points back then was that one offset
> insistet in 32-bit offset/len and the other on 16-bit.

This version sizes the fields according to page size, was there
somewhere which wanted to use an offset > PAGE_SIZE (or size > PAGE_SIZE
for that matter). That would be pretty odd and/or not really a candidate
for using this datastructure?

Ian.

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