Re: [linux-next-20130422] Bug in SLAB?

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 2 Jul 2013 06:45:27 +0900 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:

> 
> > I've read through the thread trying to work out what the end-user
> > impact of that fix is, but it's all clear as mud.  It's possible that
> > the end-user effect is `kernel locks up after printing "Booting the
> > kernel"'.  Or maybe not.
> > 
> > And if the above patch does indeed fix something significant, we might
> > need a -stable backport.
> > 
> 
> Somebody needs this patch when debugging with CONFIG_LOCKDEP=y on
> architectures with PAGE_SHIFT + MAX_ORDER > 26 .

Well *why* do they need it?  What happens without the patch?  How would
a person determine whether their kernel needs this patch?

When this patch crosses Greg's desk for -stable inclusion he's going to
wonder "why do users of -stable kernels need this", and you guys
haven't told him!

Grumble.  Why is it so hard to get a simple and decent changelog for
this patch?


Look, I'll make this easier:

: Subject: slab: fix init_lock_keys
: 
: In 3.10 kernels with CONFIG_LOCKDEP=y on architectures with
: PAGE_SHIFT + MAX_ORDER > 26 such as [architecture goes here], the kernel does
: [x] when the user does [y].
:
: init_lock_keys() goes too far in initializing values in kmalloc_caches
: because it assumed that the size of the kmalloc array goes up to
: MAX_ORDER.  However, the size of the kmalloc array for SLAB may be
: restricted due to increased page sizes or CONFIG_FORCE_MAX_ZONEORDER.
:
: Fix this by [z].


Please fill in the text within [].