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 static void augment_propagate(struct rb_node *rb, struct rb_node *stop)
  41 {
  42         while (rb != stop) {
  43                 struct drbd_interval *node = rb_entry(rb, struct drbd_interval, rb);
  44                 sector_t subtree_last = compute_subtree_last(node);
  45                 if (node->end == subtree_last)
  46                         break;
  47                 node->end = subtree_last;
  48                 rb = rb_parent(&node->rb);
  49         }
  50 }
  51
  52 static void augment_copy(struct rb_node *rb_old, struct rb_node *rb_new)
  53 {
  54         struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb);
  55         struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb);
  56
  57         new->end = old->end;
  58 }
  59
  60 static void augment_rotate(struct rb_node *rb_old, struct rb_node *rb_new)
  61 {
  62         struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb);
  63         struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb);
  64
  65         new->end = old->end;
  66         old->end = compute_subtree_last(old);
  67 }
  68
  69 static const struct rb_augment_callbacks augment_callbacks = {
  70         augment_propagate,
  71         augment_copy,
  72         augment_rotate,
  73 };
  74
  75 /**
  76  * drbd_insert_interval  -  insert a new interval into a tree
  77  */
  78 bool
  79 drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
  80 {
  81         struct rb_node **new = &root->rb_node, *parent = NULL;
  82
  83         BUG_ON(!IS_ALIGNED(this->size, 512));
  84
  85         while (*new) {
  86                 struct drbd_interval *here =
  87                         rb_entry(*new, struct drbd_interval, rb);
  88
  89                 parent = *new;
  90                 if (this->sector < here->sector)
  91                         new = &(*new)->rb_left;
  92                 else if (this->sector > here->sector)
  93                         new = &(*new)->rb_right;
  94                 else if (this < here)
  95                         new = &(*new)->rb_left;
  96                 else if (this > here)
  97                         new = &(*new)->rb_right;
  98                 else
  99                         return false;
 100         }
 101
 102         rb_link_node(&this->rb, parent, new);
 103         rb_insert_augmented(&this->rb, root, &augment_callbacks);
 104         return true;
 105 }
 106
 107 /**
 108  * drbd_contains_interval  -  check if a tree contains a given interval
 109  * @sector:     start sector of @interval
 110  * @interval:   may not be a valid pointer
 111  *
 112  * Returns if the tree contains the node @interval with start sector @start.
 113  * Does not dereference @interval until @interval is known to be a valid object
 114  * in @tree.  Returns %false if @interval is in the tree but with a different
 115  * sector number.
 116  */
 117 bool
 118 drbd_contains_interval(struct rb_root *root, sector_t sector,
 119                        struct drbd_interval *interval)
 120 {
 121         struct rb_node *node = root->rb_node;
 122
 123         while (node) {
 124                 struct drbd_interval *here =
 125                         rb_entry(node, struct drbd_interval, rb);
 126
 127                 if (sector < here->sector)
 128                         node = node->rb_left;
 129                 else if (sector > here->sector)
 130                         node = node->rb_right;
 131                 else if (interval < here)
 132                         node = node->rb_left;
 133                 else if (interval > here)
 134                         node = node->rb_right;
 135                 else
 136                         return true;
 137         }
 138         return false;
 139 }
 140
 141 /**
 142  * drbd_remove_interval  -  remove an interval from a tree
 143  */
 144 void
 145 drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
 146 {
 147         rb_erase_augmented(&this->rb, root, &augment_callbacks);
 148 }
 149
 150 /**
 151  * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
 152  * @sector:     start sector
 153  * @size:       size, aligned to 512 bytes
 154  *
 155  * Returns an interval overlapping with [sector, sector + size), or NULL if
 156  * there is none.  When there is more than one overlapping interval in the
 157  * tree, the interval with the lowest start sector is returned, and all other
 158  * overlapping intervals will be on the right side of the tree, reachable with
 159  * rb_next().
 160  */
 161 struct drbd_interval *
 162 drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
 163 {
 164         struct rb_node *node = root->rb_node;
 165         struct drbd_interval *overlap = NULL;
 166         sector_t end = sector + (size >> 9);
 167
 168         BUG_ON(!IS_ALIGNED(size, 512));
 169
 170         while (node) {
 171                 struct drbd_interval *here =
 172                         rb_entry(node, struct drbd_interval, rb);
 173
 174                 if (node->rb_left &&
 175                     sector < interval_end(node->rb_left)) {
 176                         /* Overlap if any must be on left side */
 177                         node = node->rb_left;
 178                 } else if (here->sector < end &&
 179                            sector < here->sector + (here->size >> 9)) {
 180                         overlap = here;
 181                         break;
 182                 } else if (sector >= here->sector) {
 183                         /* Overlap if any must be on right side */
 184                         node = node->rb_right;
 185                 } else
 186                         break;
 187         }
 188         return overlap;
 189 }
 190
 191 struct drbd_interval *
 192 drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
 193 {
 194         sector_t end = sector + (size >> 9);
 195         struct rb_node *node;
 196
 197         for (;;) {
 198                 node = rb_next(&i->rb);
 199                 if (!node)
 200                         return NULL;
 201                 i = rb_entry(node, struct drbd_interval, rb);
 202                 if (i->sector >= end)
 203                         return NULL;
 204                 if (sector < i->sector + (i->size >> 9))
 205                         return i;
 206         }
 207 }