Re: direct-to-BIO for O_DIRECT

[Andi Kleen <ak@suse.de>]

Andrew Morton <akpm@zip.com.au> writes:

> 	drivers/md/lvm-snap.c
> 	drivers/media/video/video-buf.c
> 	drivers/mtd/devices/blkmtd.c
> 	drivers/scsi/sg.c
> 
> the video and mtd drivers seems to be fairly easy to de-kiobufize.
> I'm aware of one proprietary driver which uses kiobufs.  XFS uses
> kiobufs a little bit - just to map the pages.

lkcd uses it too for its kernel crash dump. I suspect it wouldn't be that
hard to change.

> So with a bit of effort and maintainer-irritation, we can extract
> the kiobuf layer from the kernel.
> 
> Do we want to do that?

I think yes - keeping two kinds of iovectors for IO (kiovecs and BIOs) seems 
to be redundant.
kiovecs never fulfilled their original promise of a universal zero copy
container (e.g. they were too heavy weight for networking) so it's probably
best to remove them as a failed experiment.

-Andi