linux/mm
Mel Gorman 04fa5d6a65 mm: migrate: check page_count of THP before migrating
Hugh Dickins pointed out that migrate_misplaced_transhuge_page() does
not check page_count before migrating like base page migration and
khugepage.  He could not see why this was safe and he is right.

The potential impact of the bug is avoided due to the limitations of
NUMA balancing.  The page_mapcount() check ensures that only a single
address space is using this page and as THPs are typically private it
should not be possible for another address space to fault it in
parallel.  If the address space has one associated task then it's
difficult to have both a GUP pin and be referencing the page at the same
time.  If there are multiple tasks then a buggy scenario requires that
another thread be accessing the page while the direct IO is in flight.
This is dodgy behaviour as there is a possibility of corruption with or
without THP migration.  It would be

While we happen to be safe for the most part it is shoddy to depend on
such "safety" so this patch checks the page count similar to anonymous
pages.  Note that this does not mean that the page_mapcount() check can
go away.  If we were to remove the page_mapcount() check the the THP
would have to be unmapped from all referencing PTEs, replaced with
migration PTEs and restored properly afterwards.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reported-by: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2013-01-11 14:54:54 -08:00
..
backing-dev.c Revert "bdi: add a user-tunable cpu_list for the bdi flusher threads" 2012-12-17 11:29:09 -08:00
balloon_compaction.c mm: introduce a common interface for balloon pages mobility 2012-12-11 17:22:26 -08:00
bootmem.c mm/bootmem.c: remove unused wrapper function reserve_bootmem_generic() 2012-12-12 17:38:35 -08:00
bounce.c bounce: allow use of bounce pool via config option 2012-07-18 16:40:35 -04:00
cleancache.c ->encode_fh() API change 2012-05-29 23:28:33 -04:00
compaction.c compaction: fix build error in CMA && !COMPACTION 2012-12-20 17:40:18 -08:00
debug-pagealloc.c mm, x86: Remove debug_pagealloc_enabled 2011-12-06 09:24:07 +01:00
dmapool.c dmapool: make DMAPOOL_DEBUG detect corruption of free marker 2012-12-11 17:22:24 -08:00
fadvise.c switch simple cases of fget_light to fdget 2012-09-26 22:20:08 -04:00
failslab.c switch debugfs to umode_t 2012-01-03 22:54:56 -05:00
filemap_xip.c mm: move all mmu notifier invocations to be done outside the PT lock 2012-10-09 16:22:58 +09:00
filemap.c readahead: fault retry breaks mmap file read random detection 2012-10-09 16:22:47 +09:00
fremap.c remap_file_pages: correctly handle the case of a NULL vm_ops pointer 2012-10-19 13:37:57 -07:00
frontswap.c frontswap: support exclusive gets if tmem backend is capable 2012-09-21 10:38:12 -04:00
highmem.c Some nice cleanups, and even a patch my wife did as a "live" demo for 2012-12-20 08:37:05 -08:00
huge_memory.c mm: clean up transparent hugepage sysfs error messages 2012-12-20 17:40:20 -08:00
hugetlb_cgroup.c mm/hugetlb: create hugetlb cgroup file in hugetlb_init 2012-12-18 15:02:15 -08:00
hugetlb.c mm/hugetlb: create hugetlb cgroup file in hugetlb_init 2012-12-18 15:02:15 -08:00
hwpoison-inject.c memcg: rename config variables 2012-07-31 18:42:43 -07:00
init-mm.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
internal.h Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
interval_tree.c mm: add CONFIG_DEBUG_VM_RB build option 2012-10-09 16:22:42 +09:00
Kconfig memory-hotplug: document and enable CONFIG_MOVABLE_NODE 2012-12-18 15:02:12 -08:00
Kconfig.debug mm: more intensive memory corruption debugging 2012-01-10 16:30:42 -08:00
kmemcheck.c
kmemleak-test.c kmemleak: remove memset by using kzalloc 2011-01-27 18:31:51 +00:00
kmemleak.c mm/kmemleak.c: remove obsolete simple_strtoul 2012-12-18 15:02:15 -08:00
ksm.c ksm: make rmap walks more scalable 2012-12-20 07:06:56 -08:00
maccess.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
madvise.c mm: prepare VM_DONTDUMP for using in drivers 2012-10-09 16:22:18 +09:00
Makefile mm: introduce a common interface for balloon pages mobility 2012-12-11 17:22:26 -08:00
memblock.c x86, mm: Trim memory in memblock to be page aligned 2012-10-24 11:52:21 -07:00
memcontrol.c memcg: don't register hotcpu notifier from ->css_alloc() 2012-12-20 17:40:20 -08:00
memory_hotplug.c mm/memory_hotplug.c: improve comments 2012-12-18 15:02:15 -08:00
memory-failure.c Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
memory.c mm: reinstante dropped pmd_trans_splitting() check 2013-01-09 08:36:54 -08:00
mempolicy.c mm: mempolicy: Convert shared_policy mutex to spinlock 2013-01-02 17:32:13 -08:00
mempool.c mempool: add @gfp_mask to mempool_create_node() 2012-06-25 11:53:47 +02:00
migrate.c mm: migrate: check page_count of THP before migrating 2013-01-11 14:54:54 -08:00
mincore.c mm: thp: fix pmd_bad() triggering in code paths holding mmap_sem read mode 2012-03-21 17:54:54 -07:00
mlock.c mm, thp: fix mlock statistics 2012-10-09 16:23:03 +09:00
mm_init.c mm: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mmap.c Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
mmu_context.c mm, counters: remove task argument to sync_mm_rss() and __sync_task_rss_stat() 2012-03-21 17:54:59 -07:00
mmu_notifier.c mm/mmu_notifier: allocate mmu_notifier in advance 2012-10-25 14:37:53 -07:00
mmzone.c memcg: fix hotplugged memory zone oops 2012-11-16 14:33:04 -08:00
mprotect.c mm/mprotect.c: coding-style cleanups 2012-12-18 15:02:15 -08:00
mremap.c Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
msync.c
nobootmem.c mm: introduce new field "managed_pages" to struct zone 2012-12-12 17:38:34 -08:00
nommu.c mm: export a function to get vm committed memory 2012-11-15 15:41:22 -08:00
oom_kill.c mm, oom: remove redundant sleep in pagefault oom handler 2012-12-12 17:38:34 -08:00
page_alloc.c mm: fix zone_watermark_ok_safe() accounting of isolated pages 2013-01-04 16:11:46 -08:00
page_cgroup.c memcontrol: use N_MEMORY instead N_HIGH_MEMORY 2012-12-12 17:38:32 -08:00
page_io.c mm: add support for direct_IO to highmem pages 2012-07-31 18:42:47 -07:00
page_isolation.c mm: fix zone_watermark_ok_safe() accounting of isolated pages 2013-01-04 16:11:46 -08:00
page-writeback.c mm: fix calculation of dirtyable memory 2012-12-20 17:40:18 -08:00
pagewalk.c thp: change split_huge_page_pmd() interface 2012-12-12 17:38:31 -08:00
percpu-km.c percpu: clear memory allocated with the km allocator 2010-10-02 10:28:42 +03:00
percpu-vm.c mm: fix kernel-doc warnings 2012-06-20 14:39:36 -07:00
percpu.c mm, percpu: Make sure percpu_alloc early parameter has an argument 2012-12-02 06:23:04 -08:00
pgtable-generic.c mm: Only flush the TLB when clearing an accessible pte 2012-12-11 14:28:34 +00:00
process_vm_access.c aio/vfs: cleanup of rw_copy_check_uvector() and compat_rw_copy_check_uvector() 2012-05-31 17:49:32 -07:00
quicklist.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
readahead.c switch simple cases of fget_light to fdget 2012-09-26 22:20:08 -04:00
rmap.c Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00
shmem.c mempolicy: remove arg from mpol_parse_str, mpol_to_str 2013-01-02 09:27:10 -08:00
slab_common.c slab: propagate tunable values 2012-12-18 15:02:14 -08:00
slab.c memcg: add comments clarifying aspects of cache attribute propagation 2012-12-18 15:02:15 -08:00
slab.h slab: propagate tunable values 2012-12-18 15:02:14 -08:00
slob.c sl[au]b: always get the cache from its page in kmem_cache_free() 2012-12-18 15:02:14 -08:00
slub.c slub: drop mutex before deleting sysfs entry 2012-12-18 15:02:15 -08:00
sparse-vmemmap.c mm: delete various needless include <linux/module.h> 2011-10-31 09:20:11 -04:00
sparse.c memory-hotplug, mm/sparse.c: clear the memory to store struct page 2012-12-11 17:22:23 -08:00
swap_state.c mm: add support for a filesystem to activate swap files and use direct_IO for writing swap pages 2012-07-31 18:42:47 -07:00
swap.c mm: remove vma arg from page_evictable 2012-10-09 16:22:55 +09:00
swapfile.c mm, oom: fix race when specifying a thread as the oom origin 2012-12-11 17:22:27 -08:00
truncate.c mm: drop vmtruncate 2012-12-20 18:46:29 -05:00
util.c Merge branch 'master' into for-next 2012-10-28 19:29:19 +01:00
vmalloc.c mm: use IS_ENABLED(CONFIG_NUMA) instead of NUMA_BUILD 2012-12-11 17:22:22 -08:00
vmscan.c MM: vmscan: remove __devinit attribute. 2013-01-03 15:57:13 -08:00
vmstat.c Automatic NUMA Balancing V11 2012-12-16 15:18:08 -08:00