Re: [PATCH] advansys: fix overrun_buf aligned bug

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Fri, 2008-02-08 at 10:16 +0900, FUJITA Tomonori wrote:
> On Thu, 07 Feb 2008 19:01:55 -0600
> James Bottomley <James.Bottomley@HansenPartnership.com> wrote:
> 
> > 
> > On Fri, 2008-02-08 at 09:50 +0900, FUJITA Tomonori wrote:
> > > struct asc_dvc_var needs overrun buffer to be placed on an 8 byte
> > > boundary. advansys defines struct asc_dvc_var:
> > > 
> > > struct asc_dvc_var {
> > > 	...
> > > 	uchar overrun_buf[ASC_OVERRUN_BSIZE] __aligned(8);
> > > 
> > > The problem is that struct asc_dvc_var is placed on
> > > shost->hostdata. So if the hostdata is not on an 8 byte boundary, the
> > > advansys crashes. The hostdata is placed on a sizeof(unsigned long)
> > > boundary so the 8 byte boundary is not garanteed with x86_32.
> > > 
> > > With 2.6.23 and 2.6.24, the hostdata is on an 8 byte boundary by
> > > chance, but with the current git, it's not.
> > > 
> > > This patch removes overrun_buf static array and use kzalloc.
> > 
> > It's a bit of a waste of a kmallocs.  The usual way of fixing this type
> > of cockup is to float the structure until it becomes aligned, but I
> > suppose that involves changing all calls to shost_priv in the driver ...
> 
> Yeah, agreed. It's better but I'm not familiar with the driver so I
> use kmalloc. It's not so bad as a short-term solution, I think.
> 
> Any chance to push it to final SCSI updates for 2.6.24 merge window?
> Though we can push it any time since it's a bug fix.
> 
> Anyway, I'm fine with dropping it if Matthew will fix the driver in a
> better way. I'm happy unless people blame my IOMMU or sense buffer
> patch for this bug. :)

Sure, will do ...  I think it's an OK interim fix.

James