Re: [PATCH] Re: [bug] ata subsystem related crash with latest -git

[Jeff Garzik]

Ingo Molnar wrote:
> * Jeff Garzik <jeff@xxxxxxxxxx> wrote:
>
> > > Tomo and I agreed to kill sg_last() a few days ago anyways, so this 
> > > is perfectly fine with me.
> > Yep, the [attached] patch that kills ata_sg_is_last() is working here 
> > on both machines that were previously croaking.
> >
> > It would be nice to get pdc_adma, sata_sil24 and ipr it-works test 
> > done, but IMO the patch is pretty straightforward and should be OK.
>
> just a quick question: i have Jens's workarounds applied right now (see 
> patch below). Am i now crash/corruption-safe, or do i need your patch 
> too? And once your patch [and the other sg_*() patches] are upstream i 
> dont need the workaround anymore, correct?

You need my patch if and only if you use one of the drivers touched by 
the patch.  ata_sg_is_last() was a driver helper function, so my fix 
never really touched core code.

I never had to apply the changes you included, to fix problems here.

And looking at those changes...
> -	q->max_phys_segments = max_segments;
> +	q->max_phys_segments = max_segments - 1;
 ...
> -#define SCSI_MAX_SG_SEGMENTS	128
> +#define SCSI_MAX_SG_SEGMENTS	129

I wonder if libata should be doing

	blk_queue_max_phys_segments(q, q->max_phys_segments - 1)

to account for the pad entry that libata owns.

	Jeff



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