Re: [PATCH v3 06/11] scatterlist: support "page-less" (__pfn_t only) entries

[Dan Williams]

On Sat, May 23, 2015 at 7:12 AM, hch@xxxxxx <hch@xxxxxx> wrote:
> On Wed, May 13, 2015 at 06:35:55PM +0000, Williams, Dan J wrote:
>> Jens, I'm wondering if you want to take this series(.) as patches or
>> prepare a git branch to pull?
>
> Honestly I don't think it should go anyway.  It makes a big mess of
> a structure without providing a real user for it.  Given how we are
> using the bio_vec for in-kernel page based I/O these days it seems
> like a very dangerous idea.

There's nothing dangerous about the __pfn_t conversion of the block
layer in the !CONFIG_DEV_PFN case a __pfn_t based bio_vec is
bit-for-bit identical to a struct page based bio_vec.  However, you're
right, I can't make the same claim about a scatterlist before and
after the change.

Hmm, we're missing a pfn-only block I/O user and we're missing the
second half of the implementation that provides __pfn_t_to_page() for
persistent memory.  I'm looking to have a solution __pfn_t_to_page()
shortly, maybe that will allow the scatterlist changes to be
skipped...  we'll see.
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