Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-bionic-kernel.git] / lib / radix-tree.c

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 348eaefbed74c38b7cc2554f4a7a111280f65f2e..a2f9da59c1970cfab2a55c94f43da8843551ef05 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1203,6 +1203,98 @@ radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
 }
 EXPORT_SYMBOL(radix_tree_gang_lookup_tag_slot);
 
+#if defined(CONFIG_SHMEM) && defined(CONFIG_SWAP)
+#include <linux/sched.h> /* for cond_resched() */
+
+/*
+ * This linear search is at present only useful to shmem_unuse_inode().
+ */
+static unsigned long __locate(struct radix_tree_node *slot, void *item,
+                             unsigned long index, unsigned long *found_index)
+{
+       unsigned int shift, height;
+       unsigned long i;
+
+       height = slot->height;
+       shift = (height-1) * RADIX_TREE_MAP_SHIFT;
+
+       for ( ; height > 1; height--) {
+               i = (index >> shift) & RADIX_TREE_MAP_MASK;
+               for (;;) {
+                       if (slot->slots[i] != NULL)
+                               break;
+                       index &= ~((1UL << shift) - 1);
+                       index += 1UL << shift;
+                       if (index == 0)
+                               goto out;       /* 32-bit wraparound */
+                       i++;
+                       if (i == RADIX_TREE_MAP_SIZE)
+                               goto out;
+               }
+
+               shift -= RADIX_TREE_MAP_SHIFT;
+               slot = rcu_dereference_raw(slot->slots[i]);
+               if (slot == NULL)
+                       goto out;
+       }
+
+       /* Bottom level: check items */
+       for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
+               if (slot->slots[i] == item) {
+                       *found_index = index + i;
+                       index = 0;
+                       goto out;
+               }
+       }
+       index += RADIX_TREE_MAP_SIZE;
+out:
+       return index;
+}
+
+/**
+ *     radix_tree_locate_item - search through radix tree for item
+ *     @root:          radix tree root
+ *     @item:          item to be found
+ *
+ *     Returns index where item was found, or -1 if not found.
+ *     Caller must hold no lock (since this time-consuming function needs
+ *     to be preemptible), and must check afterwards if item is still there.
+ */
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+       struct radix_tree_node *node;
+       unsigned long max_index;
+       unsigned long cur_index = 0;
+       unsigned long found_index = -1;
+
+       do {
+               rcu_read_lock();
+               node = rcu_dereference_raw(root->rnode);
+               if (!radix_tree_is_indirect_ptr(node)) {
+                       rcu_read_unlock();
+                       if (node == item)
+                               found_index = 0;
+                       break;
+               }
+
+               node = indirect_to_ptr(node);
+               max_index = radix_tree_maxindex(node->height);
+               if (cur_index > max_index)
+                       break;
+
+               cur_index = __locate(node, item, cur_index, &found_index);
+               rcu_read_unlock();
+               cond_resched();
+       } while (cur_index != 0 && cur_index <= max_index);
+
+       return found_index;
+}
+#else
+unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
+{
+       return -1;
+}
+#endif /* CONFIG_SHMEM && CONFIG_SWAP */
 
 /**
  *     radix_tree_shrink    -    shrink height of a radix tree to minimal