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authorRik van Riel <riel@redhat.com>2010-08-09 17:18:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-08-09 20:44:55 -0700
commit76545066c8521f3e32c849744744842b4df25b79 (patch)
tree978b6b003f63e1e22618586b7d9c2dd8ef363614 /mm/migrate.c
parent012f18004da33ba672e3c60838cc4898126174d3 (diff)
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 <riel@redhat.com> Tested-by: Larry Woodman <lwoodman@redhat.com> Acked-by: Larry Woodman <lwoodman@redhat.com> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Mel Gorman <mel@csn.ul.ie> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Tested-by: Dave Young <hidave.darkstar@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/migrate.c')
-rw-r--r--mm/migrate.c10
1 files changed, 3 insertions, 7 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 5208fa1d971..38e7cad782f 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();