Re: [PATCH 2/2] convert sg to blk_rq map functions

[Mike Christie <michaelc@cs.wisc.edu>]

Mike Christie wrote:
> 
> Block layer defines the max segment size as 65536. We need
> new block layer helpers to do the mapping. Although one late night
> I thought I could use a modified blk_rq_map_kern some how. If sg or
> st allocate the reserve buffers then we could make a

oops, I meant sg or st would allocate the reserves or huge
buffers/pages/segments using some block layer helper becuase the
block layer knows the segment and size limits a little better. But
the sg or st driver would pass in the reserves to the block layer
mapping function similar to how we can pass in bio_sets to the bio code.

> blk_rq_map_kern_iovec function that worked similar to its
> user cousin but of course operated on a iovec of kernel buffers.
> But then I am not sure if at that point we should just be
> interacting with the bio code directly instead of adding a
> extra iovec abstraction. I would guess for SCSI drivers at least
> it is nicer to not worry about bio internals though. James
> and Jens would konw best though.
> 
>