[PATCH] radix-tree: Remove unnecessary indirections and clean up code

- There is frequent use of indirections in the radix code. This patch
  removes those indirections, makes the code more readable and allows
  the compilers to generate better code.

- Removing indirections allows the removal of several casts.

- Removing indirections allows the reduction of the radix_tree_path
  size from 3 to 2 words.

- Use pathp-> consistently.

- Remove unnecessary tmp variable in radix_tree_insert

- Separate the upper layer processing from the lowest layer in __lookup()
  in order to make it easier to understand what is going on and allow
  compilers to generate better code for the loop.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: James Bottomley <James.Bottomley@steeleye.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 10bed1c8c3c3012b861a055eaaf095af7906e8e5..2e9bd54beba42e0a9a172cf5e315b17b41492b1d 100644 (file)
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -1,6 +1,7 @@
 /*
  * Copyright (C) 2001 Momchil Velikov
  * Portions Copyright (C) 2001 Christoph Hellwig
+ * Copyright (C) 2005 SGI, Christoph Lameter <clameter@sgi.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -51,7 +52,7 @@ struct radix_tree_node {
 };
 
 struct radix_tree_path {
-       struct radix_tree_node *node, **slot;
+       struct radix_tree_node *node;
        int offset;
 };
 
@@ -227,7 +228,7 @@ out:
 int radix_tree_insert(struct radix_tree_root *root,
                        unsigned long index, void *item)
 {
-       struct radix_tree_node *node = NULL, *tmp, **slot;
+       struct radix_tree_node *node = NULL, *slot;
        unsigned int height, shift;
        int offset;
        int error;
@@ -240,38 +241,42 @@ int radix_tree_insert(struct radix_tree_root *root,
                        return error;
        }
 
-       slot = &root->rnode;
+       slot = root->rnode;
        height = root->height;
        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
 
        offset = 0;                     /* uninitialised var warning */
        while (height > 0) {
-               if (*slot == NULL) {
+               if (slot == NULL) {
                        /* Have to add a child node.  */
-                       if (!(tmp = radix_tree_node_alloc(root)))
+                       if (!(slot = radix_tree_node_alloc(root)))
                                return -ENOMEM;
-                       *slot = tmp;
-                       if (node)
+                       if (node) {
+                               node->slots[offset] = slot;
                                node->count++;
+                       } else
+                               root->rnode = slot;
                }
 
                /* Go a level down */
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-               node = *slot;
-               slot = (struct radix_tree_node **)(node->slots + offset);
+               node = slot;
+               slot = node->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
 
-       if (*slot != NULL)
+       if (slot != NULL)
                return -EEXIST;
+
        if (node) {
                node->count++;
+               node->slots[offset] = item;
                BUG_ON(tag_get(node, 0, offset));
                BUG_ON(tag_get(node, 1, offset));
-       }
+       } else
+               root->rnode = item;
 
-       *slot = item;
        return 0;
 }
 EXPORT_SYMBOL(radix_tree_insert);
@@ -286,27 +291,25 @@ EXPORT_SYMBOL(radix_tree_insert);
 void *radix_tree_lookup(struct radix_tree_root *root, unsigned long index)
 {
        unsigned int height, shift;
-       struct radix_tree_node **slot;
+       struct radix_tree_node *slot;
 
        height = root->height;
        if (index > radix_tree_maxindex(height))
                return NULL;
 
        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
-       slot = &root->rnode;
+       slot = root->rnode;
 
        while (height > 0) {
-               if (*slot == NULL)
+               if (slot == NULL)
                        return NULL;
 
-               slot = (struct radix_tree_node **)
-                       ((*slot)->slots +
-                               ((index >> shift) & RADIX_TREE_MAP_MASK));
+               slot = slot->slots[(index >> shift) & RADIX_TREE_MAP_MASK];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
 
-       return *slot;
+       return slot;
 }
 EXPORT_SYMBOL(radix_tree_lookup);
 
@@ -326,27 +329,27 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
                        unsigned long index, int tag)
 {
        unsigned int height, shift;
-       struct radix_tree_node **slot;
+       struct radix_tree_node *slot;
 
        height = root->height;
        if (index > radix_tree_maxindex(height))
                return NULL;
 
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
-       slot = &root->rnode;
+       slot = root->rnode;
 
        while (height > 0) {
                int offset;
 
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
-               tag_set(*slot, tag, offset);
-               slot = (struct radix_tree_node **)((*slot)->slots + offset);
-               BUG_ON(*slot == NULL);
+               tag_set(slot, tag, offset);
+               slot = slot->slots[offset];
+               BUG_ON(slot == NULL);
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
 
-       return *slot;
+       return slot;
 }
 EXPORT_SYMBOL(radix_tree_tag_set);
 
@@ -367,6 +370,7 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
                        unsigned long index, int tag)
 {
        struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
+       struct radix_tree_node *slot;
        unsigned int height, shift;
        void *ret = NULL;
 
@@ -376,38 +380,37 @@ void *radix_tree_tag_clear(struct radix_tree_root *root,
 
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        pathp->node = NULL;
-       pathp->slot = &root->rnode;
+       slot = root->rnode;
 
        while (height > 0) {
                int offset;
 
-               if (*pathp->slot == NULL)
+               if (slot == NULL)
                        goto out;
 
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                pathp[1].offset = offset;
-               pathp[1].node = *pathp[0].slot;
-               pathp[1].slot = (struct radix_tree_node **)
-                               (pathp[1].node->slots + offset);
+               pathp[1].node = slot;
+               slot = slot->slots[offset];
                pathp++;
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
 
-       ret = *pathp[0].slot;
+       ret = slot;
        if (ret == NULL)
                goto out;
 
        do {
                int idx;
 
-               tag_clear(pathp[0].node, tag, pathp[0].offset);
+               tag_clear(pathp->node, tag, pathp->offset);
                for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
-                       if (pathp[0].node->tags[tag][idx])
+                       if (pathp->node->tags[tag][idx])
                                goto out;
                }
                pathp--;
-       } while (pathp[0].node);
+       } while (pathp->node);
 out:
        return ret;
 }
@@ -429,7 +432,7 @@ int radix_tree_tag_get(struct radix_tree_root *root,
                        unsigned long index, int tag)
 {
        unsigned int height, shift;
-       struct radix_tree_node **slot;
+       struct radix_tree_node *slot;
        int saw_unset_tag = 0;
 
        height = root->height;
@@ -437,12 +440,12 @@ int radix_tree_tag_get(struct radix_tree_root *root,
                return 0;
 
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
-       slot = &root->rnode;
+       slot = root->rnode;
 
        for ( ; ; ) {
                int offset;
 
-               if (*slot == NULL)
+               if (slot == NULL)
                        return 0;
 
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
@@ -451,15 +454,15 @@ int radix_tree_tag_get(struct radix_tree_root *root,
                 * This is just a debug check.  Later, we can bale as soon as
                 * we see an unset tag.
                 */
-               if (!tag_get(*slot, tag, offset))
+               if (!tag_get(slot, tag, offset))
                        saw_unset_tag = 1;
                if (height == 1) {
-                       int ret = tag_get(*slot, tag, offset);
+                       int ret = tag_get(slot, tag, offset);
 
                        BUG_ON(ret && saw_unset_tag);
                        return ret;
                }
-               slot = (struct radix_tree_node **)((*slot)->slots + offset);
+               slot = slot->slots[offset];
                shift -= RADIX_TREE_MAP_SHIFT;
                height--;
        }
@@ -472,17 +475,21 @@ __lookup(struct radix_tree_root *root, void **results, unsigned long index,
        unsigned int max_items, unsigned long *next_index)
 {
        unsigned int nr_found = 0;
-       unsigned int shift;
-       unsigned int height = root->height;
+       unsigned int shift, height;
        struct radix_tree_node *slot;
+       unsigned long i;
+
+       height = root->height;
+       if (height == 0)
+               goto out;
 
        shift = (height-1) * RADIX_TREE_MAP_SHIFT;
        slot = root->rnode;
 
-       while (height > 0) {
-               unsigned long i = (index >> shift) & RADIX_TREE_MAP_MASK;
+       for ( ; height > 1; height--) {
 
-               for ( ; i < RADIX_TREE_MAP_SIZE; i++) {
+               for (i = (index >> shift) & RADIX_TREE_MAP_MASK ;
+                               i < RADIX_TREE_MAP_SIZE; i++) {
                        if (slot->slots[i] != NULL)
                                break;
                        index &= ~((1UL << shift) - 1);
@@ -492,22 +499,20 @@ __lookup(struct radix_tree_root *root, void **results, unsigned long index,
                }
                if (i == RADIX_TREE_MAP_SIZE)
                        goto out;
-               height--;
-               if (height == 0) {      /* Bottom level: grab some items */
-                       unsigned long j = index & RADIX_TREE_MAP_MASK;
 
-                       for ( ; j < RADIX_TREE_MAP_SIZE; j++) {
-                               index++;
-                               if (slot->slots[j]) {
-                                       results[nr_found++] = slot->slots[j];
-                                       if (nr_found == max_items)
-                                               goto out;
-                               }
-                       }
-               }
                shift -= RADIX_TREE_MAP_SHIFT;
                slot = slot->slots[i];
        }
+
+       /* Bottom level: grab some items */
+       for (i = index & RADIX_TREE_MAP_MASK; i < RADIX_TREE_MAP_SIZE; i++) {
+               index++;
+               if (slot->slots[i]) {
+                       results[nr_found++] = slot->slots[i];
+                       if (nr_found == max_items)
+                               goto out;
+               }
+       }
 out:
        *next_index = index;
        return nr_found;
@@ -655,6 +660,7 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 {
        struct radix_tree_path path[RADIX_TREE_MAX_PATH], *pathp = path;
        struct radix_tree_path *orig_pathp;
+       struct radix_tree_node *slot;
        unsigned int height, shift;
        void *ret = NULL;
        char tags[RADIX_TREE_TAGS];
@@ -666,25 +672,23 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
 
        shift = (height - 1) * RADIX_TREE_MAP_SHIFT;
        pathp->node = NULL;
-       pathp->slot = &root->rnode;
+       slot = root->rnode;
 
-       while (height > 0) {
+       for ( ; height > 0; height--) {
                int offset;
 
-               if (*pathp->slot == NULL)
+               if (slot == NULL)
                        goto out;
 
                offset = (index >> shift) & RADIX_TREE_MAP_MASK;
                pathp[1].offset = offset;
-               pathp[1].node = *pathp[0].slot;
-               pathp[1].slot = (struct radix_tree_node **)
-                               (pathp[1].node->slots + offset);
+               pathp[1].node = slot;
+               slot = slot->slots[offset];
                pathp++;
                shift -= RADIX_TREE_MAP_SHIFT;
-               height--;
        }
 
-       ret = *pathp[0].slot;
+       ret = slot;
        if (ret == NULL)
                goto out;
 
@@ -704,10 +708,10 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
                        if (tags[tag])
                                continue;
 
-                       tag_clear(pathp[0].node, tag, pathp[0].offset);
+                       tag_clear(pathp->node, tag, pathp->offset);
 
                        for (idx = 0; idx < RADIX_TREE_TAG_LONGS; idx++) {
-                               if (pathp[0].node->tags[tag][idx]) {
+                               if (pathp->node->tags[tag][idx]) {
                                        tags[tag] = 1;
                                        nr_cleared_tags--;
                                        break;
@@ -715,18 +719,19 @@ void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)
                        }
                }
                pathp--;
-       } while (pathp[0].node && nr_cleared_tags);
+       } while (pathp->node && nr_cleared_tags);
 
-       pathp = orig_pathp;
-       *pathp[0].slot = NULL;
-       while (pathp[0].node && --pathp[0].node->count == 0) {
-               pathp--;
-               BUG_ON(*pathp[0].slot == NULL);
-               *pathp[0].slot = NULL;
-               radix_tree_node_free(pathp[1].node);
+       /* Now free the nodes we do not need anymore */
+       for (pathp = orig_pathp; pathp->node; pathp--) {
+               pathp->node->slots[pathp->offset] = NULL;
+               if (--pathp->node->count)
+                       goto out;
+
+               /* Node with zero slots in use so free it */
+               radix_tree_node_free(pathp->node);
        }
-       if (root->rnode == NULL)
-               root->height = 0;
+       root->rnode = NULL;
+       root->height = 0;
 out:
        return ret;
 }