path: root/mm
diff options
authorDavid Rientjes <>2014-08-06 16:07:31 -0700
committerLinus Torvalds <>2014-08-06 18:01:21 -0700
commit9ef0a0ffa28edbf5c7cfa6be73b4ecb9896a3875 (patch)
tree6c0d71402e6c354b97eb04f4f62f00cee138ccb6 /mm
parent14a4e2141e24304fff2c697be6382ffb83888185 (diff)
mm, writeback: prevent race when calculating dirty limits
Setting vm_dirty_bytes and dirty_background_bytes is not protected by any serialization. Therefore, it's possible for either variable to change value after the test in global_dirty_limits() to determine whether available_memory needs to be initialized or not. Always ensure that available_memory is properly initialized. Signed-off-by: David Rientjes <> Acked-by: Johannes Weiner <> Acked-by: Michal Hocko <> Cc: Rik van Riel <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'mm')
1 files changed, 1 insertions, 4 deletions
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e0c943014eb7..91d73ef1744d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -261,14 +261,11 @@ static unsigned long global_dirtyable_memory(void)
void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty)
+ const unsigned long available_memory = global_dirtyable_memory();
unsigned long background;
unsigned long dirty;
- unsigned long uninitialized_var(available_memory);
struct task_struct *tsk;
- if (!vm_dirty_bytes || !dirty_background_bytes)
- available_memory = global_dirtyable_memory();
if (vm_dirty_bytes)
dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE);