mm: use lockless radix-tree probe

Probing pages and radix_tree_tagged are lockless operations with the lockless
radix-tree.  Convert these users to RCU locking rather than using tree_lock.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 44720363374c..2adb89959885 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1022,17 +1022,15 @@ int test_set_page_writeback(struct page *page)
 EXPORT_SYMBOL(test_set_page_writeback);
 
 /*
- * Return true if any of the pages in the mapping are marged with the
+ * Return true if any of the pages in the mapping are marked with the
  * passed tag.
  */
 int mapping_tagged(struct address_space *mapping, int tag)
 {
-        unsigned long flags;
         int ret;
-
-        read_lock_irqsave(&mapping->tree_lock, flags);
+        rcu_read_lock();
         ret = radix_tree_tagged(&mapping->page_tree, tag);
-        read_unlock_irqrestore(&mapping->tree_lock, flags);
+        rcu_read_unlock();
         return ret;
 }
 EXPORT_SYMBOL(mapping_tagged);