The commit is pushed to "branch-rh7-3.10.0-229.7.2.vz7.9.x-ovz" and will appear
at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-229.7.2.vz7.9.16
------>
commit ccf0ec9df7867d02df90be751a8e8cc49721df70
Author: Vladimir Davydov <[email protected]>
Date: Mon Dec 14 10:05:01 2015 +0400
ms/rmap: rmap_walk: move VM_BUG_ON to rmap_walk_file
After the patches generalizing rmap_walk pulled from upstream recently,
it is safe to call rmap_walk on anonymous pages, but the stale VM_BUG_ON
is still there. It was moved out to rmap_walk_file in the scope of
mainstream commit 9f32624be9435 ("mm/rmap: use rmap_walk() in
page_referenced()"), but I don't want to pull it, because it's quite
intrusive. Instead, let's just pull the bits needed to fix the issue.
https://jira.sw.ru/browse/PSBM-42214
Signed-off-by: Vladimir Davydov <[email protected]>
---
mm/rmap.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/mm/rmap.c b/mm/rmap.c
index 3eda1ed..c97b42d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1810,6 +1810,14 @@ static int rmap_walk_file(struct page *page, struct
rmap_walk_control *rwc)
struct vm_area_struct *vma;
int ret = SWAP_AGAIN;
+ /*
+ * The page lock not only makes sure that page->mapping cannot
+ * suddenly be NULLified by truncation, it makes sure that the
+ * structure at mapping cannot be freed and reused yet,
+ * so we can safely take mapping->i_mmap_mutex.
+ */
+ VM_BUG_ON(!PageLocked(page));
+
if (!mapping)
return ret;
mutex_lock(&mapping->i_mmap_mutex);
@@ -1841,8 +1849,6 @@ done:
int rmap_walk(struct page *page, struct rmap_walk_control *rwc)
{
- VM_BUG_ON(!PageLocked(page));
-
if (unlikely(PageKsm(page)))
return rmap_walk_ksm(page, rwc);
else if (PageAnon(page))
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