Re: [PATCH 0/7] sg_ring: a ring of scatterlist arrays

[Rusty Russell <rusty@rustcorp.com.au>]

On Monday 07 January 2008 17:37:41 Tejun Heo wrote:
> Rusty Russell wrote:
> > Hi Tejun,
> >
> >    Nice try!  Even ignoring the ugliness of undoing such an operation if
> > the caller doesn't expect you to mangle their chains, consider a
> > one-element sg array. :(
>
> Heh heh, that can be dealt with by skipping the first chain if the first
> chain is empty after chaining.  Please take a look at
> ata_sg_setup_extra() in the following.
>
> http://git.kernel.org/?p=linux/kernel/git/tj/libata-dev.git;a=blob;f=driver
>s/ata/libata-core.c;h=32dde5bbc75ed53e89ac17040da2cd0621a37161;hb=c8847e473a
>4a2844244784226eb362be10d52ce9
>
> That said, yeah, it's seriously ugly.  Restoring the original sg is ugly
> too.  I definitely agree that we need some improvements here.

Erk, that's beyond ugly, into actual evil.

To make this general you need to find the last N 1-element chains (but SCSI 
doesn't do this of course).  Oh the horror...

I'd be remiss if I didn't mention that the sg_ring ata patches were 
straightforward, and indescribably beautiful if compared to this!

Thanks,
Rusty.