Re: [PATCH-RFC] Promise TX4 implement hw-bug workaround

[Alexander Sabourenkov <screwdriver@lxnt.info>]

Jeff Garzik wrote:
> 
> Alan's point was that the existing code will give you up to
> LIBATA_MAX_PRD entries.  After the post-virtual-merge splitting code in
> ata_fill_sg() executes, the worst case result is ATA_MAX_PRD entries.
> 
> Thus, since your code has the potential to increase the number of s/g
> entries above that, it can potentially corrupt memory, lock up the
> machine, all the wonderful things that can happen when you run off the
> end of the s/g list.
> 
> The fix is to decrease .sg_tablesize (LIBATA_MAX_PRD - 2 perhaps?) so
> that you guarantee this worst case never occurs, by guaranteeing that
> the system never sends you enough s/g entries to cause your code to go
> out of bounds.
> 

Ah, now I understand. Thanks for the explanation.

I take it something guarantees that s/g entry size can not exceed 128K.


-- 

./lxnt