From 76545066c8521f3e32c849744744842b4df25b79 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 9 Aug 2010 17:18:41 -0700 Subject: mm: extend KSM refcounts to the anon_vma root KSM reference counts can cause an anon_vma to exist after the processe it belongs to have already exited. Because the anon_vma lock now lives in the root anon_vma, we need to ensure that the root anon_vma stays around until after all the "child" anon_vmas have been freed. The obvious way to do this is to have a "child" anon_vma take a reference to the root in anon_vma_fork. When the anon_vma is freed at munmap or process exit, we drop the refcount in anon_vma_unlink and possibly free the root anon_vma. The KSM anon_vma reference count function also needs to be modified to deal with the possibility of freeing 2 levels of anon_vma. The easiest way to do this is to break out the KSM magic and make it generic. When compiling without CONFIG_KSM, this code is compiled out. Signed-off-by: Rik van Riel Tested-by: Larry Woodman Acked-by: Larry Woodman Reviewed-by: Minchan Kim Cc: KAMEZAWA Hiroyuki Acked-by: Mel Gorman Acked-by: Linus Torvalds Tested-by: Dave Young Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/migrate.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) (limited to 'mm/migrate.c') diff --git a/mm/migrate.c b/mm/migrate.c index 5208fa1d9712..38e7cad782f4 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -639,7 +639,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, * exist when the page is remapped later */ anon_vma = page_anon_vma(page); - atomic_inc(&anon_vma->external_refcount); + get_anon_vma(anon_vma); } } @@ -682,12 +682,8 @@ skip_unmap: rcu_unlock: /* Drop an anon_vma reference if we took one */ - if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->root->lock)) { - int empty = list_empty(&anon_vma->head); - anon_vma_unlock(anon_vma); - if (empty) - anon_vma_free(anon_vma); - } + if (anon_vma) + drop_anon_vma(anon_vma); if (rcu_locked) rcu_read_unlock(); -- cgit v1.2.3-55-g7522