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Andrea Arcangeli 3ddb5b56f0 mm: thp: fix BUG on mm->nr_ptes 
commit 1c641e8471 upstream.

Dave Jones reports a few Fedora users hitting the BUG_ON(mm->nr_ptes...)
in exit_mmap() recently.

Quoting Hugh's discovery and explanation of the SMP race condition:

  "mm->nr_ptes had unusual locking: down_read mmap_sem plus
   page_table_lock when incrementing, down_write mmap_sem (or mm_users
   0) when decrementing; whereas THP is careful to increment and
   decrement it under page_table_lock.

   Now most of those paths in THP also hold mmap_sem for read or write
   (with appropriate checks on mm_users), but two do not: when
   split_huge_page() is called by hwpoison_user_mappings(), and when
   called by add_to_swap().

   It's conceivable that the latter case is responsible for the
   exit_mmap() BUG_ON mm->nr_ptes that has been reported on Fedora."

The simplest way to fix it without having to alter the locking is to make
split_huge_page() a noop in nr_ptes terms, so by counting the preallocated
pagetables that exists for every mapped hugepage.  It was an arbitrary
choice not to count them and either way is not wrong or right, because
they are not used but they're still allocated.

Reported-by: Dave Jones <davej@redhat.com>
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-03-12 10:32:56 -07:00
..
backing-dev.c backing-dev: ensure wakeup_timer is deleted 2011-11-21 14:31:25 -08:00
bootmem.c crash_dump: export is_kdump_kernel to modules, consolidate elfcorehdr_addr, setup_elfcorehdr and saved_max_pfn 2011-03-23 19:47:19 -07:00
bounce.c bounce: call flush_dcache_page() after bounce_copy_vec() 2010-09-09 18:57:25 -07:00
cleancache.c mm: cleancache core ops functions and config 2011-05-26 10:01:36 -06:00
compaction.c mm: compaction: check for overlapping nodes during isolation for migration 2012-02-13 11:06:11 -08:00
debug-pagealloc.c
dmapool.c mm/dmapool.c: use TASK_UNINTERRUPTIBLE in dma_pool_alloc() 2011-01-13 17:32:48 -08:00
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 readahead: fix pipeline break caused by block plug 2012-02-13 11:06:04 -08:00
filemap_xip.c mm/filemap_xip.c: fix race condition in xip_file_fault() 2012-02-13 11:06:07 -08:00
fremap.c mm: don't access vm_flags as 'int' 2011-05-26 09:20:31 -07:00
highmem.c mm,x86: fix kmap_atomic_push vs ioremap_32.c 2010-10-27 18:03:05 -07:00
huge_memory.c mm: thp: fix BUG on mm->nr_ptes 2012-03-12 10:32:56 -07:00
hugetlb.c mm: hugetlb: fix non-atomic enqueue of huge page 2012-01-06 14:14:00 -08:00
hwpoison-inject.c Fix common misspellings 2011-03-31 11:26:23 -03:00
init-mm.c mm: convert mm->cpu_vm_cpumask into cpumask_var_t 2011-05-25 08:39:21 -07:00
internal.h mm: thp: tail page refcounting fix 2011-11-11 09:36:29 -08:00
Kconfig mm: cleancache core ops functions and config 2011-05-26 10:01:36 -06:00
Kconfig.debug mm: debug-pagealloc: fix kconfig dependency warning 2011-03-22 17:44:02 -07:00
kmemcheck.c kmemcheck: Fix build errors due to missing slab.h 2010-03-30 22:02:32 +09:00
kmemleak-test.c kmemleak: remove memset by using kzalloc 2011-01-27 18:31:51 +00:00
kmemleak.c kmemleak: Do not return a pointer to an object that kmemleak did not get 2011-05-19 17:35:28 +01:00
ksm.c ksm: fix NULL pointer dereference in scan_get_next_rmap_item() 2011-06-15 20:04:02 -07:00
maccess.c maccess,probe_kernel: Make write/read src const void * 2011-05-25 19:56:23 -04:00
madvise.c thp: khugepaged: make khugepaged aware about madvise 2011-01-13 17:32:47 -08:00
Makefile mm: cleancache core ops functions and config 2011-05-26 10:01:36 -06:00
memblock.c mm/memblock: properly handle overlaps and fix error path 2011-03-22 17:44:09 -07:00
memcontrol.c mm: memcg: Correct unregistring of events attached to the same eventfd 2012-03-12 10:32:55 -07:00
memory-failure.c mm/memory-failure.c: fix spinlock vs mutex order 2011-06-27 18:00:13 -07:00
memory.c mm: thp: tail page refcounting fix 2011-11-11 09:36:29 -08:00
memory_hotplug.c mm, hotplug: protect zonelist building with zonelists_mutex 2011-06-22 21:06:48 -07:00
mempolicy.c mm: proc: move show_numa_map() to fs/proc/task_mmu.c 2011-05-25 08:39:34 -07:00
mempool.c mm: remove broken 'kzalloc' mempool 2009-09-22 07:17:35 -07:00
migrate.c mm: fix race between mremap and removing migration entry 2011-10-25 07:10:17 +02:00
mincore.c thp: mincore transparent hugepage support 2011-01-13 17:32:44 -08:00
mlock.c mm: don't access vm_flags as 'int' 2011-05-26 09:20:31 -07:00
mm_init.c
mmap.c mm: get rid of the most spurious find_vma_prev() users 2011-06-16 00:35:09 -07:00
mmu_context.c exit: fix oops in sync_mm_rss 2010-03-24 16:31:21 -07:00
mmu_notifier.c thp: mmu_notifier_test_young 2011-01-13 17:32:46 -08:00
mmzone.c mm: page allocator: adjust the per-cpu counter threshold when memory is low 2011-01-13 17:32:31 -08:00
mprotect.c thp: mprotect: transparent huge page support 2011-01-13 17:32:44 -08:00
mremap.c mm: Convert i_mmap_lock to a mutex 2011-05-25 08:39:18 -07:00
msync.c sanitize vfs_fsync calling conventions 2010-05-21 18:31:21 -04:00
nobootmem.c memblock/nobootmem: remove unneeded code from alloc_bootmem_node_high() 2011-05-25 08:39:31 -07:00
nommu.c NOMMU: Don't need to clear vm_mm when deleting a VMA 2012-03-12 10:32:56 -07:00
oom_kill.c oom: fix integer overflow of points in oom_badness 2012-01-06 14:13:51 -08:00
page-writeback.c writeback: introduce .tagged_writepages for the WB_SYNC_NONE sync stage 2011-10-03 11:40:43 -07:00
page_alloc.c mm: fix NULL ptr dereference in __count_immobile_pages 2012-01-25 17:25:05 -08:00
page_cgroup.c memcg: fix init_page_cgroup nid with sparsemem 2011-06-15 20:04:01 -07:00
page_io.c block: kill off REQ_UNPLUG 2011-03-10 08:52:27 +01:00
page_isolation.c mm: page_isolation: codeclean fix comment and rm unneeded val init 2010-10-26 16:52:11 -07:00
pagewalk.c pagewalk: only split huge pages when necessary 2011-03-22 17:44:04 -07:00
percpu-km.c percpu: clear memory allocated with the km allocator 2010-10-02 10:28:42 +03:00
percpu-vm.c percpu: fix chunk range calculation 2011-12-21 12:57:37 -08:00
percpu.c percpu: fix per_cpu_ptr_to_phys() handling of non-page-aligned addresses 2012-01-06 14:13:50 -08:00
pgtable-generic.c mm/pgtable-generic.c: fix CONFIG_SWAP=n build 2011-01-26 10:49:58 +10:00
prio_tree.c sanitize <linux/prefetch.h> usage 2011-05-20 12:50:29 -07:00
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: readahead page allocations are OK to fail 2011-05-25 08:39:25 -07:00
rmap.c mm/memory-failure.c: fix spinlock vs mutex order 2011-06-27 18:00:13 -07:00
shmem.c tmpfs: add shmem_read_mapping_page_gfp 2011-06-27 18:00:12 -07:00
slab.c SLAB: Record actual last user of freed objects. 2011-06-03 19:33:50 +03:00
slob.c mm: Remove support for kmem_cache_name() 2011-01-23 21:00:05 +02:00
slub.c slub: fix a possible memleak in __slab_alloc() 2012-02-20 12:48:14 -08:00
sparse-vmemmap.c tree-wide: fix comment/printk typos 2010-11-01 15:38:34 -04:00
sparse.c Fix common misspellings 2011-03-31 11:26:23 -03:00
swap.c mm: fix UP THP spin_is_locked BUGs 2012-02-13 11:06:11 -08:00
swap_state.c block: remove per-queue plugging 2011-03-10 08:52:07 +01:00
swapfile.c mm: move shmem prototypes to shmem_fs.h 2011-06-27 18:00:12 -07:00
thrash.c vmscan: implement swap token priority aging 2011-06-15 20:03:59 -07:00
truncate.c mm: fix assertion mapping->nrpages == 0 in end_writeback() 2011-06-27 18:00:13 -07:00
util.c mm: nommu: sort mm->mmap list properly 2011-05-25 08:39:05 -07:00
vmalloc.c mm: vmalloc: check for page allocation failure before vmlist insertion 2011-12-21 12:57:36 -08:00
vmscan.c memcg: fix vmscan count in small memcgs 2011-10-03 11:41:08 -07:00
vmstat.c mm, mem-hotplug: update pcp->stat_threshold when memory hotplug occur 2011-05-25 08:39:09 -07:00