Re: [PATCH RFC] allow bio code to unmap sg io requests and have blk_execute_rq_nowait bounce bios

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

Jens Axboe wrote:
> On Fri, Jul 29 2005, Mike Christie wrote:
> 
>>Hey Jens and James,
>>
>>The inlined patch moves the bounce buffer handling to blk_execute_rq_nowait
>>so the scsi, sg io and cdrom code does not have to handle it. To accomplish
>>this I moved the bio_uncopy_user to a bi_end_io function and bio_unmap_user
>>to a work struct that is schedule from a bi_end_io functions. Did you say
>>you disliked the idea of calling bio_unmap_user from a work struct - don't
>>remember and I lost my emails when I moved? :(
> 
> 
> It's probably alright, it cleans up the code a lot. It will cost some
> extra context switches, but I'm naively hoping that for busy io we will
> have good batching of the processing anyways.
> 

Doh! I ported sg.c and noticed I messed up. copy_to_user must be called
from user context so my patch does not work for that path.