Johannes Weiner 28ccddf795 mm: memcg: remove incorrect VM_BUG_ON for swap cache pages in uncharge ... Commit 0c59b89c81 ("mm: memcg: push down PageSwapCache check into uncharge entry functions") added a VM_BUG_ON() on PageSwapCache in the uncharge path after checking that page flag once, assuming that the state is stable in all paths, but this is not the case and the condition triggers in user environments. An uncharge after the last page table reference to the page goes away can race with reclaim adding the page to swap cache. Swap cache pages are usually uncharged when they are freed after swapout, from a path that also handles swap usage accounting and memcg lifetime management. However, since the last page table reference is gone and thus no references to the swap slot left, the swap slot will be freed shortly when reclaim attempts to write the page to disk. The whole swap accounting is not even necessary. So while the race condition for which this VM_BUG_ON was added is real and actually existed all along, there are no negative effects. Remove the VM_BUG_ON again. Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reported-by: Lingzhu Xiang <lxiang@redhat.com> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Hugh Dickins <hughd@google.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2013-05-24 16:22:51 -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
fremap.c
frontswap.c
highmem.c
huge_memory.c
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
maccess.c
madvise.c
Makefile
memblock.c
memcontrol.c	mm: memcg: remove incorrect VM_BUG_ON for swap cache pages in uncharge	2013-05-24 16:22:51 -07:00
memory_hotplug.c
memory-failure.c
memory.c
mempolicy.c
mempool.c
migrate.c
mincore.c
mlock.c
mm_init.c
mmap.c	shm: fix null pointer deref when userspace specifies invalid hugepage size	2013-05-09 14:22:47 -07:00
mmu_context.c
mmu_notifier.c	mm: mmu_notifier: re-fix freed page still mapped in secondary MMU	2013-05-24 16:22:51 -07:00
mmzone.c
mprotect.c
mremap.c
msync.c
nobootmem.c
nommu.c
oom_kill.c
page_alloc.c	mm: Fix virt_to_page() warning	2013-05-22 08:05:16 -07:00
page_cgroup.c
page_io.c
page_isolation.c
page-writeback.c
pagewalk.c
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
truncate.c
util.c
vmalloc.c
vmpressure.c
vmscan.c
vmstat.c