Re: [RFD] blk_rq_map_pages new API

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

On Thu, 12 Feb 2009 11:19:09 +0200
Boaz Harrosh <bharrosh@panasas.com> wrote:

> Boaz Harrosh wrote:
> > /**
> >  * blk_rq_map_pages - Receives an array of pages and appends them to a request structure 
> >  *
> >  * @rq:  The request to map
> >  * @pages_info: A structure that specifies the array of pages, offset and more that need to be
> >  *              map to the request. the @pages_info->null_mapped is assumed to be 1 and is ignored.
> >  * @length: Total bytes to map. Array of pages can be larger, stop mapping after @length bytes mapped.
> >  * @max_pages: When allocating the internal bio use @max_pages as an hint that says the amount of anticipated
> >  *             pages that will be mapped. This member is optional and can be zero.
> >  * 
> >  * blk_rq_map_pages can be called multiple times so the user does not need to allocate a contiguous array
> >  * of struct page pointers but can call this routine multiple times. In that case max_pages can be set
> >  * so no bio re-allocation occurs.
> >  * There is no unmap function for this mapping, the request is completed in the regular way.
> >  */
> > 
> > int blk_rq_map_pages(struct request rq, struct *rq_map_data pages_info, unsigned length, unsigned max_pages);
> > 
> > 
> > Implementation comments:
> > - Then when this member is available many places that call blk_rq_map_user() rq_map_data and null_mapped set,
> >   and buff == NULL, can be converted to this member.
> > 
> > - Internal block implementation is refactored to not duplicate any code with blk_rq_map_user().
> > 
> > Thanks for any comments
> > Boaz
> > 
> > --
> 
> FUJITA Tomonori wrote:
> > Please send a patch to implement the proposal.
> > 
> 
> Is the above API accepted by you? Is it accepted by Jens?
> Should I also attempt first comment above.
>
> If its OK I will implement it ASAP.

Sorry, I'm not sure until I see the actual code. You always find
tricky things when you actually write the code.

The patch should be small. It's not difficult at all to write a patch
to see how it works.