reproducible xfs/vmap oops

[Dave Chinner]

On Tue, Feb 03, 2009 at 04:04:23PM -0500, Christoph Hellwig wrote:
> [ 3138.799436] XFS mounting filesystem vde
> [ 3138.813184] va->va_start = 4290777088, va->va_end = 4096
> [ 3138.834754] tmp->va_start = 4195352576, tmp->va_end = 4196401152
> [ 3138.846352] ------------[ cut here ]------------
> [ 3138.850332] kernel BUG at mm/vmalloc.c:298!
> [ 3138.850332] invalid opcode: 0000 [#1] SMP 
> 
> The first va_end looks suspicious to me..

That is on i386, Christoph? If so, I'd suspect a 32 bit overflow
as 4290777088 = 0xFFC01000 and va_start/va_end are unsigned longs.
If we tried to map exactly 4MB the with va_start at 0xFFC01000 we'd
end up with va_end at 0x100001000 which would wrap to 0x1000 = 4096.

Nick - this one is probably yours ;)

Cheers,

Dave.
-- 
Dave Chinner
david at fromorbit.com