lib: radix-tree: update callback for changing leaf nodes

Support handing __radix_tree_replace() a callback that gets invoked for
all leaf nodes that change or get freed as a result of the slot
replacement, to assist users tracking nodes with node->private_list.

This prepares for putting page cache shadow entries into the radix tree
root again and drastically simplifying the shadow tracking.

Link: http://lkml.kernel.org/r/20161117193134.GD23430@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/dax.c b/fs/dax.c
index 85930c2a2749fcc33c3d6cf3d60dabfc4cc07c07..6916ed37d4631846a7478cfa3e3dd14c8808d373 100644 (file)
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -649,7 +649,8 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
 
                ret = __radix_tree_lookup(page_tree, index, &node, &slot);
                WARN_ON_ONCE(ret != entry);
-               __radix_tree_replace(page_tree, node, slot, new_entry);
+               __radix_tree_replace(page_tree, node, slot,
+                                    new_entry, NULL, NULL);
        }
        if (vmf->flags & FAULT_FLAG_WRITE)
                radix_tree_tag_set(page_tree, index, PAGECACHE_TAG_DIRTY);

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index 2d1b9b8be983a4c6b6e98d19b4209cbc1d367ee8..15c972ea951003c7be4d1c035014ef3949bc6fda 100644 (file)
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -263,9 +263,11 @@ void *__radix_tree_lookup(struct radix_tree_root *root, unsigned long index,
                          struct radix_tree_node **nodep, void ***slotp);
 void *radix_tree_lookup(struct radix_tree_root *, unsigned long);
 void **radix_tree_lookup_slot(struct radix_tree_root *, unsigned long);
+typedef void (*radix_tree_update_node_t)(struct radix_tree_node *, void *);
 void __radix_tree_replace(struct radix_tree_root *root,
                          struct radix_tree_node *node,
-                         void **slot, void *item);
+                         void **slot, void *item,
+                         radix_tree_update_node_t update_node, void *private);
 void radix_tree_replace_slot(struct radix_tree_root *root,
                             void **slot, void *item);
 bool __radix_tree_delete_node(struct radix_tree_root *root,

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 5d8930f3b3d8678262ce7c4551d0c1ced49b41a1..df4ff18dd63c3b7f93b9b94bba0825ce593ede4f 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -325,7 +325,6 @@ static void radix_tree_node_rcu_free(struct rcu_head *head)
                tag_clear(node, i, 0);
 
        node->slots[0] = NULL;
-       node->count = 0;
 
        kmem_cache_free(radix_tree_node_cachep, node);
 }
@@ -542,7 +541,9 @@ out:
  *     radix_tree_shrink    -    shrink radix tree to minimum height
  *     @root           radix tree root
  */
-static inline bool radix_tree_shrink(struct radix_tree_root *root)
+static inline bool radix_tree_shrink(struct radix_tree_root *root,
+                                    radix_tree_update_node_t update_node,
+                                    void *private)
 {
        bool shrunk = false;
 
@@ -597,8 +598,12 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root)
                 * also results in a stale slot). So tag the slot as indirect
                 * to force callers to retry.
                 */
-               if (!radix_tree_is_internal_node(child))
+               node->count = 0;
+               if (!radix_tree_is_internal_node(child)) {
                        node->slots[0] = RADIX_TREE_RETRY;
+                       if (update_node)
+                               update_node(node, private);
+               }
 
                radix_tree_node_free(node);
                shrunk = true;
@@ -608,7 +613,8 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root)
 }
 
 static bool delete_node(struct radix_tree_root *root,
-                       struct radix_tree_node *node)
+                       struct radix_tree_node *node,
+                       radix_tree_update_node_t update_node, void *private)
 {
        bool deleted = false;
 
@@ -617,7 +623,8 @@ static bool delete_node(struct radix_tree_root *root,
 
                if (node->count) {
                        if (node == entry_to_node(root->rnode))
-                               deleted |= radix_tree_shrink(root);
+                               deleted |= radix_tree_shrink(root, update_node,
+                                                            private);
                        return deleted;
                }
 
@@ -880,17 +887,20 @@ static void replace_slot(struct radix_tree_root *root,
 
 /**
  * __radix_tree_replace                - replace item in a slot
- * @root:      radix tree root
- * @node:      pointer to tree node
- * @slot:      pointer to slot in @node
- * @item:      new item to store in the slot.
+ * @root:              radix tree root
+ * @node:              pointer to tree node
+ * @slot:              pointer to slot in @node
+ * @item:              new item to store in the slot.
+ * @update_node:       callback for changing leaf nodes
+ * @private:           private data to pass to @update_node
  *
  * For use with __radix_tree_lookup().  Caller must hold tree write locked
  * across slot lookup and replacement.
  */
 void __radix_tree_replace(struct radix_tree_root *root,
                          struct radix_tree_node *node,
-                         void **slot, void *item)
+                         void **slot, void *item,
+                         radix_tree_update_node_t update_node, void *private)
 {
        /*
         * This function supports replacing exceptional entries and
@@ -900,7 +910,13 @@ void __radix_tree_replace(struct radix_tree_root *root,
        replace_slot(root, node, slot, item,
                     !node && slot != (void **)&root->rnode);
 
-       delete_node(root, node);
+       if (!node)
+               return;
+
+       if (update_node)
+               update_node(node, private);
+
+       delete_node(root, node, update_node, private);
 }
 
 /**
@@ -1585,7 +1601,7 @@ unsigned long radix_tree_locate_item(struct radix_tree_root *root, void *item)
 bool __radix_tree_delete_node(struct radix_tree_root *root,
                              struct radix_tree_node *node)
 {
-       return delete_node(root, node);
+       return delete_node(root, node, NULL, NULL);
 }
 
 static inline void delete_sibling_entries(struct radix_tree_node *node,
@@ -1642,7 +1658,7 @@ void *radix_tree_delete_item(struct radix_tree_root *root,
                node_tag_clear(root, node, tag, offset);
 
        delete_sibling_entries(node, node_to_entry(slot), offset);
-       __radix_tree_replace(root, node, slot, NULL);
+       __radix_tree_replace(root, node, slot, NULL, NULL, NULL);
 
        return entry;
 }

diff --git a/mm/shmem.c b/mm/shmem.c
index 3149ddee8f557c8775941bfa11ba97f7c5d243f9..abd7403aba41f0001e6724c640f5e4095a63c142 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -311,7 +311,8 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
                return -ENOENT;
        if (item != expected)
                return -ENOENT;
-       __radix_tree_replace(&mapping->page_tree, node, pslot, replacement);
+       __radix_tree_replace(&mapping->page_tree, node, pslot,
+                            replacement, NULL, NULL);
        return 0;
 }