LXR linux/drivers/block/drbd/drbd

   1#include <asm/bug.h>
   2#include <linux/rbtree_augmented.h>
   3#include "drbd_interval.h"
   4
   5/**
   6 * interval_end  -  return end of @node
   7 */
   8static inline
   9sector_t interval_end(struct rb_node *node)
  10{
  11        struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
  12        return this->end;
  13}
  14
  15/**
  16 * compute_subtree_last  -  compute end of @node
  17 *
  18 * The end of an interval is the highest (start + (size >> 9)) value of this
  19 * node and of its children.  Called for @node and its parents whenever the end
  20 * may have changed.
  21 */
  22static inline sector_t
  23compute_subtree_last(struct drbd_interval *node)
  24{
  25        sector_t max = node->sector + (node->size >> 9);
  26
  27        if (node->rb.rb_left) {
  28                sector_t left = interval_end(node->rb.rb_left);
  29                if (left > max)
  30                        max = left;
  31        }
  32        if (node->rb.rb_right) {
  33                sector_t right = interval_end(node->rb.rb_right);
  34                if (right > max)
  35                        max = right;
  36        }
  37        return max;
  38}
  39
  40RB_DECLARE_CALLBACKS(static, augment_callbacks, struct drbd_interval, rb,
  41                     sector_t, end, compute_subtree_last);
  42
  43/**
  44 * drbd_insert_interval  -  insert a new interval into a tree
  45 */
  46bool
  47drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
  48{
  49        struct rb_node **new = &root->rb_node, *parent = NULL;
  50        sector_t this_end = this->sector + (this->size >> 9);
  51
  52        BUG_ON(!IS_ALIGNED(this->size, 512));
  53
  54        while (*new) {
  55                struct drbd_interval *here =
  56                        rb_entry(*new, struct drbd_interval, rb);
  57
  58                parent = *new;
  59                if (here->end < this_end)
  60                        here->end = this_end;
  61                if (this->sector < here->sector)
  62                        new = &(*new)->rb_left;
  63                else if (this->sector > here->sector)
  64                        new = &(*new)->rb_right;
  65                else if (this < here)
  66                        new = &(*new)->rb_left;
  67                else if (this > here)
  68                        new = &(*new)->rb_right;
  69                else
  70                        return false;
  71        }
  72
  73        this->end = this_end;
  74        rb_link_node(&this->rb, parent, new);
  75        rb_insert_augmented(&this->rb, root, &augment_callbacks);
  76        return true;
  77}
  78
  79/**
  80 * drbd_contains_interval  -  check if a tree contains a given interval
  81 * @sector:     start sector of @interval
  82 * @interval:   may not be a valid pointer
  83 *
  84 * Returns if the tree contains the node @interval with start sector @start.
  85 * Does not dereference @interval until @interval is known to be a valid object
  86 * in @tree.  Returns %false if @interval is in the tree but with a different
  87 * sector number.
  88 */
  89bool
  90drbd_contains_interval(struct rb_root *root, sector_t sector,
  91                       struct drbd_interval *interval)
  92{
  93        struct rb_node *node = root->rb_node;
  94
  95        while (node) {
  96                struct drbd_interval *here =
  97                        rb_entry(node, struct drbd_interval, rb);
  98
  99                if (sector < here->sector)
 100                        node = node->rb_left;
 101                else if (sector > here->sector)
 102                        node = node->rb_right;
 103                else if (interval < here)
 104                        node = node->rb_left;
 105                else if (interval > here)
 106                        node = node->rb_right;
 107                else
 108                        return true;
 109        }
 110        return false;
 111}
 112
 113/**
 114 * drbd_remove_interval  -  remove an interval from a tree
 115 */
 116void
 117drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
 118{
 119        rb_erase_augmented(&this->rb, root, &augment_callbacks);
 120}
 121
 122/**
 123 * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
 124 * @sector:     start sector
 125 * @size:       size, aligned to 512 bytes
 126 *
 127 * Returns an interval overlapping with [sector, sector + size), or NULL if
 128 * there is none.  When there is more than one overlapping interval in the
 129 * tree, the interval with the lowest start sector is returned, and all other
 130 * overlapping intervals will be on the right side of the tree, reachable with
 131 * rb_next().
 132 */
 133struct drbd_interval *
 134drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
 135{
 136        struct rb_node *node = root->rb_node;
 137        struct drbd_interval *overlap = NULL;
 138        sector_t end = sector + (size >> 9);
 139
 140        BUG_ON(!IS_ALIGNED(size, 512));
 141
 142        while (node) {
 143                struct drbd_interval *here =
 144                        rb_entry(node, struct drbd_interval, rb);
 145
 146                if (node->rb_left &&
 147                    sector < interval_end(node->rb_left)) {
 148                        /* Overlap if any must be on left side */
 149                        node = node->rb_left;
 150                } else if (here->sector < end &&
 151                           sector < here->sector + (here->size >> 9)) {
 152                        overlap = here;
 153                        break;
 154                } else if (sector >= here->sector) {
 155                        /* Overlap if any must be on right side */
 156                        node = node->rb_right;
 157                } else
 158                        break;
 159        }
 160        return overlap;
 161}
 162
 163struct drbd_interval *
 164drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
 165{
 166        sector_t end = sector + (size >> 9);
 167        struct rb_node *node;
 168
 169        for (;;) {
 170                node = rb_next(&i->rb);
 171                if (!node)
 172                        return NULL;
 173                i = rb_entry(node, struct drbd_interval, rb);
 174                if (i->sector >= end)
 175                        return NULL;
 176                if (sector < i->sector + (i->size >> 9))
 177                        return i;
 178        }
 179}
 180