Re: [PATCH 2/3] block: unexport blk_rq_append_bio

[FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>]

On Wed, 11 Feb 2009 17:41:35 +0200
Boaz Harrosh <bharrosh@panasas.com> wrote:

> FUJITA Tomonori wrote:
> > On Wed, 11 Feb 2009 17:07:16 +0200
> > Boaz Harrosh <bharrosh@panasas.com> wrote:
> > 
> >>>
> >>>
> >> Sure it can pass pages to ULD but then how ULD maks a request out of
> >> pages?
> > 
> > If you extend blk_rq_map_kern as James did, your ULD make a request
> > out of passed pages, that is, the block layer properly builds a
> > request with bio(s).
> 
> What? I don't understand?
> blk_rq_map_kern takes a kernel-pointer and length, how to pass array
> of page* ?

You can call it multiple times. But I guess that you need something
new since you need to handle user pages.


> > I think that another possible option is adding a new mapping function
> > that can handle multiple bios for kernel buffers (as Mike extended
> > blk_rq_map_user).
> > 
> 
> Yes adding a new mapping function can help. Please note I need to
> add (append) pages same as bio_add_pc_page() but on request level.

I think that what you need already exists.

See how st uses blk_rq_map_user() in scsi-misc (keywords: rq_map_data
and null_mapped). Please read it before saying something like 'we need
to handle kernel buffer'.


> And yet we had an entry that did exactly that, blk_rq_append_bio(), no?

Using blk_rq_append_bio in SCSI is unacceptable.


> >> And it gets more complicated then that (above multiple times)
> > 
> > I don't think so. If you don't have time to work on it, please let me
> > know. I'll fix OSD ULD.
> 
> I have all the time in the world, And yes what James did with blk_rq_map_kern
> will help with appending other osd segments on top of data.
> 
> If you propose the appropriate new API for block request level I can implement
> that in block, and also in OSD. What other entry you want to add/change that solve
> my need?

If you have time, how about making a proposal. ;)

But as I wrote above, I think that blk_rq_map_user() works for you.