drivers/block/drbd/drbd_interval.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <asm/bug.h>
   3 #include <linux/rbtree_augmented.h>
   4 #include "drbd_interval.h"
   5
   6 /**
   7  * interval_end  -  return end of @node
   8  */
   9 static inline
  10 sector_t interval_end(struct rb_node *node)
  11 {
  12         struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
  13         return this->end;
  14 }
  15
  16 /**
  17  * compute_subtree_last  -  compute end of @node
  18  *
  19  * The end of an interval is the highest (start + (size >> 9)) value of this
  20  * node and of its children.  Called for @node and its parents whenever the end
  21  * may have changed.
  22  */
  23 static inline sector_t
  24 compute_subtree_last(struct drbd_interval *node)
  25 {
  26         sector_t max = node->sector + (node->size >> 9);
  27
  28         if (node->rb.rb_left) {
  29                 sector_t left = interval_end(node->rb.rb_left);
  30                 if (left > max)
  31                         max = left;
  32         }
  33         if (node->rb.rb_right) {
  34                 sector_t right = interval_end(node->rb.rb_right);
  35                 if (right > max)
  36                         max = right;
  37         }
  38         return max;
  39 }
  40
  41 RB_DECLARE_CALLBACKS(static, augment_callbacks, struct drbd_interval, rb,
  42                      sector_t, end, compute_subtree_last);
  43
  44 /**
  45  * drbd_insert_interval  -  insert a new interval into a tree
  46  */
  47 bool
  48 drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
  49 {
  50         struct rb_node **new = &root->rb_node, *parent = NULL;
  51         sector_t this_end = this->sector + (this->size >> 9);
  52
  53         BUG_ON(!IS_ALIGNED(this->size, 512));
  54
  55         while (*new) {
  56                 struct drbd_interval *here =
  57                         rb_entry(*new, struct drbd_interval, rb);
  58
  59                 parent = *new;
  60                 if (here->end < this_end)
  61                         here->end = this_end;
  62                 if (this->sector < here->sector)
  63                         new = &(*new)->rb_left;
  64                 else if (this->sector > here->sector)
  65                         new = &(*new)->rb_right;
  66                 else if (this < here)
  67                         new = &(*new)->rb_left;
  68                 else if (this > here)
  69                         new = &(*new)->rb_right;
  70                 else
  71                         return false;
  72         }
  73
  74         this->end = this_end;
  75         rb_link_node(&this->rb, parent, new);
  76         rb_insert_augmented(&this->rb, root, &augment_callbacks);
  77         return true;
  78 }
  79
  80 /**
  81  * drbd_contains_interval  -  check if a tree contains a given interval
  82  * @sector:     start sector of @interval
  83  * @interval:   may not be a valid pointer
  84  *
  85  * Returns if the tree contains the node @interval with start sector @start.
  86  * Does not dereference @interval until @interval is known to be a valid object
  87  * in @tree.  Returns %false if @interval is in the tree but with a different
  88  * sector number.
  89  */
  90 bool
  91 drbd_contains_interval(struct rb_root *root, sector_t sector,
  92                        struct drbd_interval *interval)
  93 {
  94         struct rb_node *node = root->rb_node;
  95
  96         while (node) {
  97                 struct drbd_interval *here =
  98                         rb_entry(node, struct drbd_interval, rb);
  99
 100                 if (sector < here->sector)
 101                         node = node->rb_left;
 102                 else if (sector > here->sector)
 103                         node = node->rb_right;
 104                 else if (interval < here)
 105                         node = node->rb_left;
 106                 else if (interval > here)
 107                         node = node->rb_right;
 108                 else
 109                         return true;
 110         }
 111         return false;
 112 }
 113
 114 /**
 115  * drbd_remove_interval  -  remove an interval from a tree
 116  */
 117 void
 118 drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
 119 {
 120         rb_erase_augmented(&this->rb, root, &augment_callbacks);
 121 }
 122
 123 /**
 124  * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
 125  * @sector:     start sector
 126  * @size:       size, aligned to 512 bytes
 127  *
 128  * Returns an interval overlapping with [sector, sector + size), or NULL if
 129  * there is none.  When there is more than one overlapping interval in the
 130  * tree, the interval with the lowest start sector is returned, and all other
 131  * overlapping intervals will be on the right side of the tree, reachable with
 132  * rb_next().
 133  */
 134 struct drbd_interval *
 135 drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
 136 {
 137         struct rb_node *node = root->rb_node;
 138         struct drbd_interval *overlap = NULL;
 139         sector_t end = sector + (size >> 9);
 140
 141         BUG_ON(!IS_ALIGNED(size, 512));
 142
 143         while (node) {
 144                 struct drbd_interval *here =
 145                         rb_entry(node, struct drbd_interval, rb);
 146
 147                 if (node->rb_left &&
 148                     sector < interval_end(node->rb_left)) {
 149                         /* Overlap if any must be on left side */
 150                         node = node->rb_left;
 151                 } else if (here->sector < end &&
 152                            sector < here->sector + (here->size >> 9)) {
 153                         overlap = here;
 154                         break;
 155                 } else if (sector >= here->sector) {
 156                         /* Overlap if any must be on right side */
 157                         node = node->rb_right;
 158                 } else
 159                         break;
 160         }
 161         return overlap;
 162 }
 163
 164 struct drbd_interval *
 165 drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
 166 {
 167         sector_t end = sector + (size >> 9);
 168         struct rb_node *node;
 169
 170         for (;;) {
 171                 node = rb_next(&i->rb);
 172                 if (!node)
 173                         return NULL;
 174                 i = rb_entry(node, struct drbd_interval, rb);
 175                 if (i->sector >= end)
 176                         return NULL;
 177                 if (sector < i->sector + (i->size >> 9))
 178                         return i;
 179         }
 180 }