Regression in kernel 4.12-rc1 for Powerpc 32 - bisected to commit 3448890c32c3

[Al Viro]

On Sat, Jun 24, 2017 at 12:29:23PM -0500, Larry Finger wrote:

> I made a break through. If I turn off inline copy to/from users for 32-bit
> ppc with the following patch, then the system boots:

OK...  So it's 4.6.3 miscompiling something - it is hardware-independent,
reproduced in qemu.  I'd like to get more self-contained example of
miscompile, though; should be done by tonight...