TOMOYO: Use RCU primitives for list operation

Replace list operation with RCU primitives and replace
down_read()/up_read() with srcu_read_lock()/srcu_read_unlock().

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 21 insertions, 7 deletions

diff --git a/security/tomoyo/common.h b/security/tomoyo/common.h
index bd10f9fa3511..c6f13925472a 100644
--- a/security/tomoyo/common.h
+++ b/security/tomoyo/common.h
@@ -269,6 +269,8 @@ struct tomoyo_io_buffer {
         int (*write) (struct tomoyo_io_buffer *);
         /* Exclusive lock for this structure.   */
         struct mutex io_sem;
+        /* Index returned by tomoyo_read_lock(). */
+        int reader_idx;
         /* The position currently reading from. */
         struct list_head *read_var1;
         /* Extra variables for reading.         */
@@ -446,16 +448,28 @@ extern struct tomoyo_domain_info tomoyo_kernel_domain;
  * @cookie:     the &struct list_head to use as a cookie.
  * @head:       the head for your list.
  *
- * Same with list_for_each() except that this primitive uses @cookie
+ * Same with list_for_each_rcu() except that this primitive uses @cookie
  * so that we can continue iteration.
  * @cookie must be NULL when iteration starts, and @cookie will become
  * NULL when iteration finishes.
  */
-#define list_for_each_cookie(pos, cookie, head)                       \
-        for (({ if (!cookie)                                          \
-                                     cookie = head; }),               \
-             pos = (cookie)->next;                                    \
-             prefetch(pos->next), pos != (head) || ((cookie) = NULL); \
-             (cookie) = pos, pos = pos->next)
+#define list_for_each_cookie(pos, cookie, head)                         \
+        for (({ if (!cookie)                                            \
+                                     cookie = head; }),                 \
+                     pos = rcu_dereference((cookie)->next);             \
+             prefetch(pos->next), pos != (head) || ((cookie) = NULL);   \
+             (cookie) = pos, pos = rcu_dereference(pos->next))
+
+extern struct srcu_struct tomoyo_ss;
+
+static inline int tomoyo_read_lock(void)
+{
+        return srcu_read_lock(&tomoyo_ss);
+}
+
+static inline void tomoyo_read_unlock(int idx)
+{
+        srcu_read_unlock(&tomoyo_ss, idx);
+}
 
 #endif /* !defined(_SECURITY_TOMOYO_COMMON_H) */