This patch allow to inject faults only for specific slabs.
In order to preserve default behavior cache filter is off by
default (all caches are faulty).

One may define specific set of slabs like this:
# mark skbuff_head_cache as faulty
echo 1 > /sys/kernel/slab/skbuff_head_cache/failslab
# Turn on cache filter (off by default)
echo 1 > /sys/kernel/debug/failslab/cache-filter
# Turn on fault injection
echo 1 > /sys/kernel/debug/failslab/times
echo 1 > /sys/kernel/debug/failslab/probability
Acked-by: NDavid Rientjes <rientjes@google.com>
Acked-by: NAkinobu Mita <akinobu.mita@gmail.com>
Acked-by: NChristoph Lameter <cl@linux-foundation.org>
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>

Impact: cleanup

mm/failslab.c depends on slab.h without including it:

    CC      mm/failslab.o
  mm/failslab.c: In function ‘should_failslab’:
  mm/failslab.c:16: error: ‘__GFP_NOFAIL’ undeclared (first use in this function)
  mm/failslab.c:16: error: (Each undeclared identifier is reported only once
  mm/failslab.c:16: error: for each function it appears in.)
  mm/failslab.c:19: error: ‘__GFP_WAIT’ undeclared (first use in this function)
  make[1]: *** [mm/failslab.o] Error 1
  make: *** [mm] Error 2

It gets included implicitly currently - but this will not be the
case with upcoming kmemtrace changes.
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
LKML-Reference: <1237888761.25315.69.camel@penberg-laptop>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Currently fault-injection capability for SLAB allocator is only
available to SLAB. This patch makes it available to SLUB, too.

[penberg@cs.helsinki.fi: unify slab and slub implementations]
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: NAkinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: NPekka Enberg <penberg@cs.helsinki.fi>