drivers/block/drbd/drbd_interval.c

   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  */
   8 static inline
   9 sector_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  */
  22 static inline sector_t
  23 compute_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
  40 RB_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  */
  46 bool
  47 drbd_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  */
  89 bool
  90 drbd_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  */
 116 void
 117 drbd_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  */
 133 struct drbd_interval *
 134 drbd_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
 163 struct drbd_interval *
 164 drbd_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 }