hold task->mempolicy while numa_maps scans.
/proc/<pid>/numa_maps scans vma and show mempolicy under
mmap_sem. It sometimes accesses task->mempolicy which can
be freed without mmap_sem and numa_maps can show some
garbage while scanning.
This patch tries to take reference count of task->mempolicy at reading
numa_maps before calling get_vma_policy(). By this, task->mempolicy
will not be freed until numa_maps reaches its end.
V2->v3
- updated comments to be more verbose.
- removed task_lock() in numa_maps code.
V1->V2
- access task->mempolicy only once and remember it. Becase kernel/exit.c
can overwrite it.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/internal.h b/fs/proc/internal.h
index cceaab0..43973b0 100644
--- a/fs/proc/internal.h
+++ b/fs/proc/internal.h
@@ -12,6 +12,7 @@
#include <linux/sched.h>
#include <linux/proc_fs.h>
struct ctl_table_header;
+struct mempolicy;
extern struct proc_dir_entry proc_root;
#ifdef CONFIG_PROC_SYSCTL
@@ -74,6 +75,9 @@
#ifdef CONFIG_MMU
struct vm_area_struct *tail_vma;
#endif
+#ifdef CONFIG_NUMA
+ struct mempolicy *task_mempolicy;
+#endif
};
void proc_init_inodecache(void);