Re: Instability issues with NetBSD-9, xen-4.11 and the xbdb backend driver

[Brian Buhrow <buhrow%nfbcal.org@localhost>]

	Hello.  The error handling patch I provided doesn't fix the underlying
problem, I agree, but it does bring the error handling code into alignment
across the file.  If you look at:
sys/arch/xen/xen/xbdback_xenbus.c:1491, you'll see that I simply made the
behavior the same in the two places where xbdback_io_error is called.
	The problem with error handling as it is now is that two requests with
the same data get passed to the domu, which is what causes the biodone2
panic in the domu's.   I've tested this patch and it seems to do the right
thing.

	If it's not correct, then we ought to at least be consistent  when
handling i/o errors.

-Brian

On Nov 15,  1:20pm, Manuel Bouyer wrote:
} Subject: Re: Instability issues with NetBSD-9, xen-4.11 and the xbdb backe
} On Thu, Nov 14, 2019 at 07:25:39PM -0800, Brian Buhrow wrote:
} > 	Hello.  Here is a simple patch that I think addresses the issue I'm
} > seeing with the dom0 causing domu's to panic with biodon2 already errors
} > when errors occur with the hypervisor granting process.  I think this is
} > the more correct way to deal with such errors.
} > this makes the error handling path match in the two places where error
} > handling is treated.
} > 
} > Thoughts?
} 
} I don't think it's the correct way to handle this in this case; I think it
} could leave dandling requests in the ring.
} 
} AFAIK xbdi->xbdi_cont_aux can point to xbdback_co_main_done2, 
} xbdback_co_cache_flush2 or xbdback_co_io_loop.
} 
} I guess the problematic case would be xbdback_co_io_loop(). But I can't
} see how it can be, as the xbdi->xbdi_io = NULL should force a
} request split.
} 
} -- 
} Manuel Bouyer <bouyer%antioche.eu.org@localhost>
}      NetBSD: 26 ans d'experience feront toujours la difference
} --
>-- End of excerpt from Manuel Bouyer