drivers/block/drbd/drbd_interval.c

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