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         sector_t this_end = this->sector + (this->size >> 9);
  83
  84         BUG_ON(!IS_ALIGNED(this->size, 512));
  85
  86         while (*new) {
  87                 struct drbd_interval *here =
  88                         rb_entry(*new, struct drbd_interval, rb);
  89
  90                 parent = *new;
  91                 if (here->end < this_end)
  92                         here->end = this_end;
  93                 if (this->sector < here->sector)
  94                         new = &(*new)->rb_left;
  95                 else if (this->sector > here->sector)
  96                         new = &(*new)->rb_right;
  97                 else if (this < here)
  98                         new = &(*new)->rb_left;
  99                 else if (this > here)
 100                         new = &(*new)->rb_right;
 101                 else
 102                         return false;
 103         }
 104
 105         this->end = this_end;
 106         rb_link_node(&this->rb, parent, new);
 107         rb_insert_augmented(&this->rb, root, &augment_callbacks);
 108         return true;
 109 }
 110
 111 /**
 112  * drbd_contains_interval  -  check if a tree contains a given interval
 113  * @sector:     start sector of @interval
 114  * @interval:   may not be a valid pointer
 115  *
 116  * Returns if the tree contains the node @interval with start sector @start.
 117  * Does not dereference @interval until @interval is known to be a valid object
 118  * in @tree.  Returns %false if @interval is in the tree but with a different
 119  * sector number.
 120  */
 121 bool
 122 drbd_contains_interval(struct rb_root *root, sector_t sector,
 123                        struct drbd_interval *interval)
 124 {
 125         struct rb_node *node = root->rb_node;
 126
 127         while (node) {
 128                 struct drbd_interval *here =
 129                         rb_entry(node, struct drbd_interval, rb);
 130
 131                 if (sector < here->sector)
 132                         node = node->rb_left;
 133                 else if (sector > here->sector)
 134                         node = node->rb_right;
 135                 else if (interval < here)
 136                         node = node->rb_left;
 137                 else if (interval > here)
 138                         node = node->rb_right;
 139                 else
 140                         return true;
 141         }
 142         return false;
 143 }
 144
 145 /**
 146  * drbd_remove_interval  -  remove an interval from a tree
 147  */
 148 void
 149 drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
 150 {
 151         rb_erase_augmented(&this->rb, root, &augment_callbacks);
 152 }
 153
 154 /**
 155  * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
 156  * @sector:     start sector
 157  * @size:       size, aligned to 512 bytes
 158  *
 159  * Returns an interval overlapping with [sector, sector + size), or NULL if
 160  * there is none.  When there is more than one overlapping interval in the
 161  * tree, the interval with the lowest start sector is returned, and all other
 162  * overlapping intervals will be on the right side of the tree, reachable with
 163  * rb_next().
 164  */
 165 struct drbd_interval *
 166 drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
 167 {
 168         struct rb_node *node = root->rb_node;
 169         struct drbd_interval *overlap = NULL;
 170         sector_t end = sector + (size >> 9);
 171
 172         BUG_ON(!IS_ALIGNED(size, 512));
 173
 174         while (node) {
 175                 struct drbd_interval *here =
 176                         rb_entry(node, struct drbd_interval, rb);
 177
 178                 if (node->rb_left &&
 179                     sector < interval_end(node->rb_left)) {
 180                         /* Overlap if any must be on left side */
 181                         node = node->rb_left;
 182                 } else if (here->sector < end &&
 183                            sector < here->sector + (here->size >> 9)) {
 184                         overlap = here;
 185                         break;
 186                 } else if (sector >= here->sector) {
 187                         /* Overlap if any must be on right side */
 188                         node = node->rb_right;
 189                 } else
 190                         break;
 191         }
 192         return overlap;
 193 }
 194
 195 struct drbd_interval *
 196 drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
 197 {
 198         sector_t end = sector + (size >> 9);
 199         struct rb_node *node;
 200
 201         for (;;) {
 202                 node = rb_next(&i->rb);
 203                 if (!node)
 204                         return NULL;
 205                 i = rb_entry(node, struct drbd_interval, rb);
 206                 if (i->sector >= end)
 207                         return NULL;
 208                 if (sector < i->sector + (i->size >> 9))
 209                         return i;
 210         }
 211 }