4.4-stable review patch. If anyone has any objections, please let me know.
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From: Konstantin Khlebnikov khlebnikov@yandex-team.ru
commit e4c5800a3991f0c6a766983535dfc10d51802cf6 upstream.
This check effectively catches anon vma hierarchy inconsistence and some vma corruptions. It was effective for catching corner cases in anon vma reusing logic. For now this code seems stable so check could be hidden under CONFIG_DEBUG_VM and replaced with WARN because it's not so fatal.
Signed-off-by: Konstantin Khlebnikov khlebnikov@yandex-team.ru Suggested-by: Vasily Averin vvs@virtuozzo.com Acked-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Arnd Bergmann arnd@arndb.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/rmap.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/rmap.c +++ b/mm/rmap.c @@ -408,7 +408,7 @@ void unlink_anon_vmas(struct vm_area_str list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { struct anon_vma *anon_vma = avc->anon_vma;
- BUG_ON(anon_vma->degree); + VM_WARN_ON(anon_vma->degree); put_anon_vma(anon_vma);
list_del(&avc->same_vma);