[Trusty/Utopic/Vivid][SRU][PATCH] LP#1456952 -- mm/slab_common: support the slub_debug boot option on specific object size

[Gavin Guo]

BugLink: http://bugs.launchpad.net/bugs/1456952

[Impact]

slub_debug cannot work for specific kmem_cache size.

e.g. slub_debug=PU,kmalloc-1024

The slub_debug is used to enable the debugging of use-after-free, poison
overwritten, double free. And it also increases the up time of the server
when the above mentioned errors happen instead of crashing immediately.

However, currently, there exists bug that the slub_debug cannot be applied
for the specific object size. This is not helpful to enable the whole
system slub_debug because the performance loss will be up to 20%~30%
according to the customer's measurement. The patch here to limit the
slub_debug only on the specific object size to alleviate the performance
loss.

[Fix]

The slub_debug=PU,kmalloc-xx cannot work because in the
create_kmalloc_caches() the s->name is created after the
create_kmalloc_cache() is called.  The name is NULL in the
create_kmalloc_cache() so the kmem_cache_flags() would not set the
slub_debug flags to the s->flags.  The fix here set up a kmalloc_names
string array for the initialization purpose and delete the dynamic name
creation of kmalloc_caches.

The patch generated from git format-patch from Trusty/Utopic/Vivid/Upstream
can't be used for each other. So, I prepared 3 patches for each release.

[Test case]

Install the patched kernel.
sudo reboot

sudo vim /etc/default/grub
append "slub_debug=FPZU,kmalloc-1024" to GRUB_CMDLINE_LINUX_DEFAULT
sudo update-grub
sudo reboot

# Check if the kmalloc-1024 debug options are enabled
sudo cat /sys/kernel/slab/kmalloc-1024/sanity_checks
# shoulb be 1
sudo cat /sys/kernel/slab/kmalloc-1024/red_zone
# shoulb be 1
sudo cat /sys/kernel/slab/kmalloc-1024/poison
# shoulb be 1

# Check other object size
sudo cat /sys/kernel/slab/kmalloc-8/sanity_checks
# shoulb be 0
sudo cat /sys/kernel/slab/kmalloc-8/red_zone
# shoulb be 0
sudo cat /sys/kernel/slab/kmalloc-8/poison
# shoulb be 0

Gavin Guo (1):
  mm/slab_common: support the slub_debug boot option on specific object
    size

 include/linux/slab.h | 22 +++++++++++++++++++
 mm/slab_common.c     | 62 +++++++++++++++++++++++++++++++++-------------------
 2 files changed, 61 insertions(+), 23 deletions(-)

-- 
2.0.0