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Hugh Dickins 4e31635c36 ksm: fix bad user data when swapping 
Building under memory pressure, with KSM on 2.6.36-rc5, collapsed with
an internal compiler error: typically indicating an error in swapping.

Perhaps there's a timing issue which makes it now more likely, perhaps
it's just a long time since I tried for so long: this bug goes back to
KSM swapping in 2.6.33.

Notice how reuse_swap_page() allows an exclusive page to be reused, but
only does SetPageDirty if it can delete it from swap cache right then -
if it's currently under Writeback, it has to be left in cache and we
don't SetPageDirty, but the page can be reused.  Fine, the dirty bit
will get set in the pte; but notice how zap_pte_range() does not bother
to transfer pte_dirty to page_dirty when unmapping a PageAnon.

If KSM chooses to share such a page, it will look like a clean copy of
swapcache, and not be written out to swap when its memory is needed;
then stale data read back from swap when it's needed again.

We could fix this in reuse_swap_page() (or even refuse to reuse a
page under writeback), but it's more honest to fix my oversight in
KSM's write_protect_page().  Several days of testing on three machines
confirms that this fixes the issue they showed.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
 		2010-10-04 11:09:53 -07:00
..
Kconfig mm: avoid warning when COMPACTION is selected 2010-09-09 18:57:24 -07:00
Kconfig.debug trivial: improve help text for mm debug config options 2009-09-21 15:14:57 +02:00
Makefile lmb: rename to memblock 2010-07-14 17:14:00 +10:00
backing-dev.c bdi: Initialize noop_backing_dev_info properly 2010-09-22 09:48:47 +02:00
bootmem.c x86,nobootmem: make alloc_bootmem_node fall back to other node when 32bit numa is used 2010-07-20 16:25:40 -07:00
bounce.c bounce: call flush_dcache_page() after bounce_copy_vec() 2010-09-09 18:57:25 -07:00
compaction.c mm: compaction: handle active and inactive fairly in too_many_isolated 2010-09-09 18:57:24 -07:00
debug-pagealloc.c generic debug pagealloc 2009-04-01 08:59:13 -07:00
dmapool.c dmapools: protect page_list walk in show_pools() 2009-06-30 18:56:00 -07:00
fadvise.c readahead: introduce FMODE_RANDOM for POSIX_FADV_RANDOM 2010-03-06 11:26:25 -08:00
failslab.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
filemap.c gcc-4.6: mm: fix unused but set warnings 2010-08-09 20:44:58 -07:00
filemap_xip.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
fremap.c Avoid pgoff overflow in remap_file_pages 2010-09-25 09:34:58 -07:00
highmem.c mm,kdb,kgdb: Add a debug reference for the kdb kmap usage 2010-08-05 09:22:24 -05:00
hugetlb.c hugetlb, rmap: fix confusing page locking in hugetlb_cow() 2010-09-23 17:29:18 -07:00
hwpoison-inject.c HWPOISON, hugetlb: support hwpoison injection for hugepage 2010-08-11 09:23:11 +02:00
init-mm.c mm: provide init_mm mm_context initializer 2010-08-09 20:44:54 -07:00
internal.h HWPOISON: add an interface to switch off/on all the page filters 2009-12-16 12:19:59 +01:00
kmemcheck.c kmemcheck: Fix build errors due to missing slab.h 2010-03-30 22:02:32 +09:00
kmemleak-test.c percpu: clean up percpu variable definitions 2009-06-24 15:13:48 +09:00
kmemleak.c kmemleak: Fix typo in the comment 2010-08-08 21:57:23 +01:00
ksm.c ksm: fix bad user data when swapping 2010-10-04 11:09:53 -07:00
maccess.c maccess,probe_kernel: Allow arch specific override probe_kernel_(read|write) 2010-01-07 11:58:36 -06:00
madvise.c HWPOISON: Add a madvise() injector for soft page offlining 2009-12-16 12:20:00 +01:00
memblock.c memblock: Fix memblock_is_region_reserved() to return a boolean 2010-08-09 11:21:38 +10:00
memcontrol.c memcg: convert to use zone_to_nid() from bare zone->zone_pgdat->node_id 2010-08-11 08:59:19 -07:00
memory-failure.c Merge branch 'hwpoison' of git://git.kernel.org/pub/scm/linux/kernel/git/ak/linux-mce-2.6 2010-08-12 10:15:10 -07:00
memory.c mm: further fix swapin race condition 2010-09-20 10:44:37 -07:00
memory_hotplug.c memory hotplug: fix next block calculation in is_removable 2010-09-09 18:57:24 -07:00
mempolicy.c mempolicy: reduce stack size of migrate_pages() 2010-08-09 20:44:58 -07:00
mempool.c mm: remove broken 'kzalloc' mempool 2009-09-22 07:17:35 -07:00
migrate.c mm: extend KSM refcounts to the anon_vma root 2010-08-09 20:44:55 -07:00
mincore.c mincore: do nested page table walks 2010-05-25 08:06:58 -07:00
mlock.c mm: Move vma_stack_continue into mm.h 2010-09-09 09:05:06 -07:00
mm_init.c
…
mmap.c mmap: call unlink_anon_vmas() in __split_vma() in case of error 2010-09-22 17:22:40 -07:00
mmu_context.c exit: fix oops in sync_mm_rss 2010-03-24 16:31:21 -07:00
mmu_notifier.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mmzone.c mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake 2010-09-09 18:57:25 -07:00
mprotect.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
mremap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nommu.c mm: make the vma list be doubly linked 2010-08-21 08:49:21 -07:00
oom_kill.c oom: filter unkillable tasks from tasklist dump 2010-09-22 17:22:39 -07:00
page-writeback.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2010-08-28 14:07:20 -07:00
page_alloc.c mm: page allocator: drain per-cpu lists after direct reclaim allocation fails 2010-09-09 18:57:25 -07:00
page_cgroup.c kmemleak: Annotate false positive in init_section_page_cgroup() 2010-07-19 11:54:14 +01:00
page_io.c block: unify flags for struct bio and struct request 2010-08-07 18:20:39 +02:00
page_isolation.c
…
pagewalk.c pagemap: fix pfn calculation for hugepage 2010-04-07 08:38:04 -07:00
percpu-km.c percpu: implement kernel memory based chunk allocation 2010-05-01 08:30:50 +02:00
percpu-vm.c percpu: move vmalloc based chunk management into percpu-vm.c 2010-05-01 08:30:50 +02:00
percpu.c percpu: fix pcpu_last_unit_cpu 2010-09-21 08:12:25 +02:00
percpu_up.c percpu: add __percpu notations to UP allocator 2010-08-07 14:20:53 +02:00
prio_tree.c
…
quicklist.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
readahead.c readahead.c: fix comment 2010-05-25 08:07:00 -07:00
rmap.c ksm: fix page_address_in_vma anon_vma oops 2010-10-04 11:09:53 -07:00
shmem.c shmem: put_super must percpu_counter_destroy 2010-08-17 18:33:11 -07:00
slab.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6 2010-08-22 10:08:52 -07:00
slob.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6 2010-08-06 11:44:08 -07:00
slub.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6 2010-08-06 11:44:08 -07:00
sparse-vmemmap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sparse.c sparsemem: on no vmemmap path put mem_map on node high too 2010-05-25 08:06:56 -07:00
swap.c mm: export lru_cache_add_*() to modules 2010-05-25 15:06:06 +02:00
swap_state.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
swapfile.c swap: discard while swapping only if SWAP_FLAG_DISCARD 2010-09-09 18:57:25 -07:00
thrash.c mm: pass mm to grab_swap_token 2009-06-23 12:50:05 -07:00
truncate.c check ATTR_SIZE contraints in inode_change_ok 2010-08-09 16:47:39 -04:00
util.c mm: use memdup_user 2010-08-09 20:44:54 -07:00
vmalloc.c Merge branch 'stable/xen-swiotlb-0.8.6' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen 2010-08-12 09:09:41 -07:00
vmscan.c vmscan: check all_unreclaimable in direct reclaim path 2010-09-22 17:22:39 -07:00
vmstat.c mm: page allocator: calculate a better estimate of NR_FREE_PAGES when memory is low and kswapd is awake 2010-09-09 18:57:25 -07:00