radix-tree: delete radix_tree_range_tag_if_tagged()

This is an exceptionally complicated function with just one caller
(tag_pages_for_writeback).  We devote a large portion of the runtime of
the test suite to testing this one function which has one caller.  By
introducing the new function radix_tree_iter_tag_set(), we can eliminate
all of the complexity while keeping the performance.  The caller can now
use a fairly standard radix_tree_for_each() loop, and it doesn't need to
worry about tricksy things like 'start' wrapping.

The test suite continues to spend a large amount of time investigating
this function, but now it's testing the underlying primitives such as
radix_tree_iter_resume() and the radix_tree_for_each_tagged() iterator
which are also used by other parts of the kernel.

Link: http://lkml.kernel.org/r/1480369871-5271-57-git-send-email-mawilcox@linuxonhyperv.com
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Tested-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 37 insertions, 37 deletions

diff --git a/include/linux/radix-tree.h b/include/linux/radix-tree.h
index a13d3f7c6c65..7a8d2516c73a 100644
--- a/include/linux/radix-tree.h
+++ b/include/linux/radix-tree.h
@@ -121,6 +121,41 @@ static inline bool radix_tree_empty(struct radix_tree_root *root)
 }
 
 /**
+ * struct radix_tree_iter - radix tree iterator state
+ *
+ * @index:      index of current slot
+ * @next_index: one beyond the last index for this chunk
+ * @tags:       bit-mask for tag-iterating
+ * @node:       node that contains current slot
+ * @shift:      shift for the node that holds our slots
+ *
+ * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
+ * subinterval of slots contained within one radix tree leaf node.  It is
+ * described by a pointer to its first slot and a struct radix_tree_iter
+ * which holds the chunk's position in the tree and its size.  For tagged
+ * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
+ * radix tree tag.
+ */
+struct radix_tree_iter {
+        unsigned long   index;
+        unsigned long   next_index;
+        unsigned long   tags;
+        struct radix_tree_node *node;
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+        unsigned int    shift;
+#endif
+};
+
+static inline unsigned int iter_shift(const struct radix_tree_iter *iter)
+{
+#ifdef CONFIG_RADIX_TREE_MULTIORDER
+        return iter->shift;
+#else
+        return 0;
+#endif
+}
+
+/**
  * Radix-tree synchronization
  *
  * The radix-tree API requires that users provide all synchronisation (with
@@ -283,6 +318,8 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
                         unsigned long index, unsigned int tag);
 int radix_tree_tag_get(struct radix_tree_root *root,
                         unsigned long index, unsigned int tag);
+void radix_tree_iter_tag_set(struct radix_tree_root *root,
+                const struct radix_tree_iter *iter, unsigned int tag);
 unsigned int
 radix_tree_gang_lookup_tag(struct radix_tree_root *root, void **results,
                 unsigned long first_index, unsigned int max_items,
@@ -291,10 +328,6 @@ unsigned int
 radix_tree_gang_lookup_tag_slot(struct radix_tree_root *root, void ***results,
                 unsigned long first_index, unsigned int max_items,
                 unsigned int tag);
-unsigned long radix_tree_range_tag_if_tagged(struct radix_tree_root *root,
-                unsigned long *first_indexp, unsigned long last_index,
-                unsigned long nr_to_tag,
-                unsigned int fromtag, unsigned int totag);
 int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag);
 
 static inline void radix_tree_preload_end(void)
@@ -302,39 +335,6 @@ static inline void radix_tree_preload_end(void)
         preempt_enable();
 }
 
-/**
- * struct radix_tree_iter - radix tree iterator state
- *
- * @index:      index of current slot
- * @next_index: one beyond the last index for this chunk
- * @tags:       bit-mask for tag-iterating
- * @shift:      shift for the node that holds our slots
- *
- * This radix tree iterator works in terms of "chunks" of slots.  A chunk is a
- * subinterval of slots contained within one radix tree leaf node.  It is
- * described by a pointer to its first slot and a struct radix_tree_iter
- * which holds the chunk's position in the tree and its size.  For tagged
- * iteration radix_tree_iter also holds the slots' bit-mask for one chosen
- * radix tree tag.
- */
-struct radix_tree_iter {
-        unsigned long   index;
-        unsigned long   next_index;
-        unsigned long   tags;
-#ifdef CONFIG_RADIX_TREE_MULTIORDER
-        unsigned int    shift;
-#endif
-};
-
-static inline unsigned int iter_shift(struct radix_tree_iter *iter)
-{
-#ifdef CONFIG_RADIX_TREE_MULTIORDER
-        return iter->shift;
-#else
-        return 0;
-#endif
-}
-
 #define RADIX_TREE_ITER_TAG_MASK        0x00FF  /* tag index in lower byte */
 #define RADIX_TREE_ITER_TAGGED          0x0100  /* lookup tagged slots */
 #define RADIX_TREE_ITER_CONTIG          0x0200  /* stop at first hole */