drbd: Add interval tree data structure

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

diff --git a/drivers/block/drbd/Makefile b/drivers/block/drbd/Makefile
index 0d3f337..cacbb04 100644 (file)
--- a/drivers/block/drbd/Makefile
+++ b/drivers/block/drbd/Makefile
@@ -1,5 +1,6 @@
 drbd-y := drbd_bitmap.o drbd_proc.o
 drbd-y += drbd_worker.o drbd_receiver.o drbd_req.o drbd_actlog.o
 drbd-y += drbd_main.o drbd_strings.o drbd_nl.o
+drbd-y += drbd_interval.o
 
 obj-$(CONFIG_BLK_DEV_DRBD)     += drbd.o

diff --git a/drivers/block/drbd/drbd_interval.c b/drivers/block/drbd/drbd_interval.c
new file mode 100644 (file)
index 0000000..2511dd9
--- /dev/null
+++ b/drivers/block/drbd/drbd_interval.c
@@ -0,0 +1,156 @@
+#include "drbd_interval.h"
+
+/**
+ * interval_end  -  return end of @node
+ */
+static inline
+sector_t interval_end(struct rb_node *node)
+{
+       struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
+       return this->end;
+}
+
+/**
+ * update_interval_end  -  recompute end of @node
+ *
+ * The end of an interval is the highest (start + (size >> 9)) value of this
+ * node and of its children.  Called for @node and its parents whenever the end
+ * may have changed.
+ */
+static void
+update_interval_end(struct rb_node *node, void *__unused)
+{
+       struct drbd_interval *this = rb_entry(node, struct drbd_interval, rb);
+       sector_t end;
+
+       end = this->sector + (this->size >> 9);
+       if (node->rb_left) {
+               sector_t left = interval_end(node->rb_left);
+               if (left > end)
+                       end = left;
+       }
+       if (node->rb_right) {
+               sector_t right = interval_end(node->rb_right);
+               if (right > end)
+                       end = right;
+       }
+       this->end = end;
+}
+
+/**
+ * drbd_insert_interval  -  insert a new interval into a tree
+ */
+bool
+drbd_insert_interval(struct rb_root *root, struct drbd_interval *this)
+{
+       struct rb_node **new = &root->rb_node, *parent = NULL;
+
+       BUG_ON(!IS_ALIGNED(this->size, 512));
+
+       while (*new) {
+               struct drbd_interval *here =
+                       rb_entry(*new, struct drbd_interval, rb);
+
+               parent = *new;
+               if (this->sector < here->sector)
+                       new = &(*new)->rb_left;
+               else if (this->sector > here->sector)
+                       new = &(*new)->rb_right;
+               else if (this < here)
+                       new = &(*new)->rb_left;
+               else if (this->sector > here->sector)
+                       new = &(*new)->rb_right;
+                       return false;
+       }
+
+       rb_link_node(&this->rb, parent, new);
+       rb_insert_color(&this->rb, root);
+       rb_augment_insert(&this->rb, update_interval_end, NULL);
+       return true;
+}
+
+/**
+ * drbd_contains_interval  -  check if a tree contains a given interval
+ * @sector:    start sector of @interval
+ * @interval:  may not be a valid pointer
+ *
+ * Returns if the tree contains the node @interval with start sector @start.
+ * Does not dereference @interval until @interval is known to be a valid object
+ * in @tree.  Returns %false if @interval is in the tree but with a different
+ * sector number.
+ */
+bool
+drbd_contains_interval(struct rb_root *root, sector_t sector,
+                      struct drbd_interval *interval)
+{
+       struct rb_node *node = root->rb_node;
+
+       while (node) {
+               struct drbd_interval *here =
+                       rb_entry(node, struct drbd_interval, rb);
+
+               if (sector < here->sector)
+                       node = node->rb_left;
+               else if (sector > here->sector)
+                       node = node->rb_right;
+               else if (interval < here)
+                       node = node->rb_left;
+               else if (interval > here)
+                       node = node->rb_right;
+               else
+                       return interval->sector == sector;
+       }
+       return false;
+}
+
+/**
+ * drbd_remove_interval  -  remove an interval from a tree
+ */
+void
+drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
+{
+       struct rb_node *deepest;
+
+       deepest = rb_augment_erase_begin(&this->rb);
+       rb_erase(&this->rb, root);
+       rb_augment_erase_end(deepest, update_interval_end, NULL);
+}
+
+/**
+ * drbd_find_overlap  - search for an interval overlapping with [sector, sector + size)
+ * @sector:    start sector
+ * @size:      size, aligned to 512 bytes
+ *
+ * Returns the interval overlapping with [sector, sector + size), or NULL.
+ * When there is more than one overlapping interval in the tree, the interval
+ * with the lowest start sector is returned.
+ */
+struct drbd_interval *
+drbd_find_overlap(struct rb_root *root, sector_t sector, unsigned int size)
+{
+       struct rb_node *node = root->rb_node;
+       struct drbd_interval *overlap = NULL;
+       sector_t end = sector + (size >> 9);
+
+       BUG_ON(!IS_ALIGNED(size, 512));
+
+       while (node) {
+               struct drbd_interval *here =
+                       rb_entry(node, struct drbd_interval, rb);
+
+               if (node->rb_left &&
+                   sector < interval_end(node->rb_left)) {
+                       /* Overlap if any must be on left side */
+                       node = node->rb_left;
+               } else if (here->sector < end &&
+                          sector < here->sector + (here->size >> 9)) {
+                       overlap = here;
+                       break;
+               } else if (sector >= here->sector) {
+                       /* Overlap if any must be on right side */
+                       node = node->rb_right;
+               } else
+                       break;
+       }
+       return overlap;
+}

diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
new file mode 100644 (file)
index 0000000..bf8dcf7
--- /dev/null
+++ b/drivers/block/drbd/drbd_interval.h
@@ -0,0 +1,31 @@
+#ifndef __DRBD_INTERVAL_H
+#define __DRBD_INTERVAL_H
+
+#include <linux/types.h>
+#include <linux/rbtree.h>
+
+struct drbd_interval {
+       struct rb_node rb;
+       sector_t sector;        /* start sector of the interval */
+       unsigned int size;      /* size in bytes */
+       sector_t end;           /* highest interval end in subtree */
+};
+
+static inline void drbd_clear_interval(struct drbd_interval *i)
+{
+       RB_CLEAR_NODE(&i->rb);
+}
+
+static inline bool drbd_interval_empty(struct drbd_interval *i)
+{
+       return RB_EMPTY_NODE(&i->rb);
+}
+
+bool drbd_insert_interval(struct rb_root *, struct drbd_interval *);
+struct drbd_interval *drbd_find_interval(struct rb_root *, sector_t,
+                                        struct drbd_interval *);
+void drbd_remove_interval(struct rb_root *, struct drbd_interval *);
+struct drbd_interval *drbd_find_overlap(struct rb_root *, sector_t,
+                                       unsigned int);
+
+#endif  /* __DRBD_INTERVAL_H */