---

yaml --- r: 230815 b: refs/heads/master c: 29c1f67 h: refs/heads/master i: 230813: 48a469b 230811: aa1a7fa 230807: 6d2bf2e 230799: 566a5d3 230783: 0bb77c6 v: v3
git-mirror · Jan 14, 2011 · 7f80343 · 7f80343
1 parent 51de921
commit 7f80343
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Showing 3 changed files with 19 additions and 3 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 22e5c47ee238abe636655c3862ed28d6eb084ad4
+refs/heads/master: 29c1f677d424e8c5683a837fc4f03fc9f19201d7
diff --git a/trunk/include/linux/radix-tree.h b/trunk/include/linux/radix-tree.h
@@ -145,6 +145,22 @@ static inline void *radix_tree_deref_slot(void **pslot)
 	return rcu_dereference(*pslot);
 }
 
+/**
+ * radix_tree_deref_slot_protected	- dereference a slot without RCU lock but with tree lock held
+ * @pslot:	pointer to slot, returned by radix_tree_lookup_slot
+ * Returns:	item that was stored in that slot with any direct pointer flag
+ *		removed.
+ *
+ * Similar to radix_tree_deref_slot but only used during migration when a pages
+ * mapping is being moved. The caller does not hold the RCU read lock but it
+ * must hold the tree lock to prevent parallel updates.
+ */
+static inline void *radix_tree_deref_slot_protected(void **pslot,
+							spinlock_t *treelock)
+{
+	return rcu_dereference_protected(*pslot, lockdep_is_held(treelock));
+}
+
 /**
  * radix_tree_deref_retry	- check radix_tree_deref_slot
  * @arg:	pointer returned by radix_tree_deref_slot

diff --git a/trunk/mm/migrate.c b/trunk/mm/migrate.c
@@ -248,7 +248,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 
 	expected_count = 2 + page_has_private(page);
 	if (page_count(page) != expected_count ||
-			(struct page *)radix_tree_deref_slot(pslot) != page) {
+		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return -EAGAIN;
 	}
@@ -320,7 +320,7 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
 
 	expected_count = 2 + page_has_private(page);
 	if (page_count(page) != expected_count ||
-	    (struct page *)radix_tree_deref_slot(pslot) != page) {
+		radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) {
 		spin_unlock_irq(&mapping->tree_lock);
 		return -EAGAIN;
 	}