path: root/mm/ksm.c
diff options
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/ksm.c
parentmm: always lock the root (oldest) anon_vma (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 '')
1 files changed, 6 insertions, 11 deletions
diff --git a/mm/ksm.c b/mm/ksm.c
index da6037c261f1..9f2acc998a37 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -318,19 +318,14 @@ static void hold_anon_vma(struct rmap_item *rmap_item,
struct anon_vma *anon_vma)
rmap_item->anon_vma = anon_vma;
- atomic_inc(&anon_vma->external_refcount);
+ get_anon_vma(anon_vma);
-static void drop_anon_vma(struct rmap_item *rmap_item)
+static void ksm_drop_anon_vma(struct rmap_item *rmap_item)
struct anon_vma *anon_vma = rmap_item->anon_vma;
- if (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);
- }
+ drop_anon_vma(anon_vma);
@@ -415,7 +410,7 @@ static void break_cow(struct rmap_item *rmap_item)
* It is not an accident that whenever we want to break COW
* to undo, we also need to drop a reference to the anon_vma.
- drop_anon_vma(rmap_item);
+ ksm_drop_anon_vma(rmap_item);
if (ksm_test_exit(mm))
@@ -470,7 +465,7 @@ static void remove_node_from_stable_tree(struct stable_node *stable_node)
- drop_anon_vma(rmap_item);
+ ksm_drop_anon_vma(rmap_item);
rmap_item->address &= PAGE_MASK;
@@ -558,7 +553,7 @@ static void remove_rmap_item_from_tree(struct rmap_item *rmap_item)
- drop_anon_vma(rmap_item);
+ ksm_drop_anon_vma(rmap_item);
rmap_item->address &= PAGE_MASK;
} else if (rmap_item->address & UNSTABLE_FLAG) {