Greg Thelen 6920a1bd03 memcg: remove incorrect underflow check ... When a memcg is deleted mem_cgroup_reparent_charges() moves charged memory to the parent memcg. As of v3.11-9444-g3ea67d0 "memcg: add per cgroup writeback pages accounting" there's bad pointer read. The goal was to check for counter underflow. The counter is a per cpu counter and there are two problems with the code: (1) per cpu access function isn't used, instead a naked pointer is used which easily causes oops. (2) the check doesn't sum all cpus Test: $ cd /sys/fs/cgroup/memory $ mkdir x $ echo 3 > /proc/sys/vm/drop_caches $ (echo $BASHPID >> x/tasks && exec cat) & [1] 7154 $ grep ^mapped x/memory.stat mapped_file 53248 $ echo 7154 > tasks $ rmdir x <OOPS> The fix is to remove the check. It's currently dangerous and isn't worth fixing it to use something expensive, such as percpu_counter_sum(), for each reparented page. __this_cpu_read() isn't enough to fix this because there's no guarantees of the current cpus count. The only guarantees is that the sum of all per-cpu counter is >= nr_pages. Fixes: 3ea67d06e4 ("memcg: add per cgroup writeback pages accounting") Reported-and-tested-by: Flavio Leitner <fbl@redhat.com> Signed-off-by: Greg Thelen <gthelen@google.com> Reviewed-by: Sha Zhengju <handai.szj@taobao.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2013-11-01 12:22:28 -07:00
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backing-dev.c
balloon_compaction.c
bootmem.c
bounce.c
cleancache.c
compaction.c
debug-pagealloc.c
dmapool.c
fadvise.c
failslab.c
filemap_xip.c
filemap.c	mm: memcg: handle non-error OOM situations more gracefully	2013-10-16 21:35:53 -07:00
fremap.c
frontswap.c
highmem.c
huge_memory.c	mm: Close races between THP migration and PMD numa clearing	2013-10-29 11:38:05 +01:00
hugetlb_cgroup.c
hugetlb.c
hwpoison-inject.c
init-mm.c
internal.h
interval_tree.c
Kconfig
Kconfig.debug
kmemcheck.c
kmemleak-test.c
kmemleak.c
ksm.c
list_lru.c	mm: list_lru: fix almost infinite loop causing effective livelock	2013-10-30 12:57:46 -07:00
maccess.c
madvise.c
Makefile
memblock.c
memcontrol.c	memcg: remove incorrect underflow check	2013-11-01 12:22:28 -07:00
memory_hotplug.c
memory-failure.c
memory.c	mm: numa: Sanitize task_numa_fault() callsites	2013-10-29 11:37:52 +01:00
mempolicy.c
mempool.c
migrate.c	mm: Close races between THP migration and PMD numa clearing	2013-10-29 11:38:05 +01:00
mincore.c
mlock.c
mm_init.c
mmap.c
mmu_context.c
mmu_notifier.c
mmzone.c
mprotect.c	mm: Account for a THP NUMA hinting update as one PTE update	2013-10-29 11:38:17 +01:00
mremap.c	mm: revert mremap pud_free anti-fix	2013-10-16 21:35:53 -07:00
msync.c
nobootmem.c
nommu.c
oom_kill.c	mm: memcg: handle non-error OOM situations more gracefully	2013-10-16 21:35:53 -07:00
page_alloc.c
page_cgroup.c
page_io.c
page_isolation.c
page-writeback.c	writeback: fix negative bdi max pause	2013-10-16 21:35:53 -07:00
pagewalk.c	mm/pagewalk.c: fix walk_page_range() access of wrong PTEs	2013-10-30 14:27:03 -07:00
percpu-km.c
percpu-vm.c
percpu.c
pgtable-generic.c
process_vm_access.c
quicklist.c
readahead.c
rmap.c
shmem.c
slab_common.c
slab.c
slab.h
slob.c
slub.c
sparse-vmemmap.c
sparse.c
swap_state.c
swap.c
swapfile.c	swap: fix set_blocksize race during swapon/swapoff	2013-10-16 21:35:53 -07:00
truncate.c
util.c
vmalloc.c
vmpressure.c
vmscan.c
vmstat.c
zbud.c
zswap.c