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path: root/drivers/block/drbd/drbd_interval.c
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Diffstat (limited to 'drivers/block/drbd/drbd_interval.c')
-rw-r--r--drivers/block/drbd/drbd_interval.c179
1 files changed, 179 insertions, 0 deletions
diff --git a/drivers/block/drbd/drbd_interval.c b/drivers/block/drbd/drbd_interval.c
new file mode 100644
index 000000000..51b25ad85
--- /dev/null
+++ b/drivers/block/drbd/drbd_interval.c
@@ -0,0 +1,179 @@
+#include <asm/bug.h>
+#include <linux/rbtree_augmented.h>
+#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;
+}
+
+/**
+ * compute_subtree_last - compute 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 inline sector_t
+compute_subtree_last(struct drbd_interval *node)
+{
+ sector_t max = node->sector + (node->size >> 9);
+
+ if (node->rb.rb_left) {
+ sector_t left = interval_end(node->rb.rb_left);
+ if (left > max)
+ max = left;
+ }
+ if (node->rb.rb_right) {
+ sector_t right = interval_end(node->rb.rb_right);
+ if (right > max)
+ max = right;
+ }
+ return max;
+}
+
+RB_DECLARE_CALLBACKS(static, augment_callbacks, struct drbd_interval, rb,
+ sector_t, end, compute_subtree_last);
+
+/**
+ * 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;
+ sector_t this_end = this->sector + (this->size >> 9);
+
+ BUG_ON(!IS_ALIGNED(this->size, 512));
+
+ while (*new) {
+ struct drbd_interval *here =
+ rb_entry(*new, struct drbd_interval, rb);
+
+ parent = *new;
+ if (here->end < this_end)
+ here->end = this_end;
+ 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 > here)
+ new = &(*new)->rb_right;
+ else
+ return false;
+ }
+
+ this->end = this_end;
+ rb_link_node(&this->rb, parent, new);
+ rb_insert_augmented(&this->rb, root, &augment_callbacks);
+ 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 true;
+ }
+ return false;
+}
+
+/**
+ * drbd_remove_interval - remove an interval from a tree
+ */
+void
+drbd_remove_interval(struct rb_root *root, struct drbd_interval *this)
+{
+ rb_erase_augmented(&this->rb, root, &augment_callbacks);
+}
+
+/**
+ * drbd_find_overlap - search for an interval overlapping with [sector, sector + size)
+ * @sector: start sector
+ * @size: size, aligned to 512 bytes
+ *
+ * Returns an interval overlapping with [sector, sector + size), or NULL if
+ * there is none. When there is more than one overlapping interval in the
+ * tree, the interval with the lowest start sector is returned, and all other
+ * overlapping intervals will be on the right side of the tree, reachable with
+ * rb_next().
+ */
+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;
+}
+
+struct drbd_interval *
+drbd_next_overlap(struct drbd_interval *i, sector_t sector, unsigned int size)
+{
+ sector_t end = sector + (size >> 9);
+ struct rb_node *node;
+
+ for (;;) {
+ node = rb_next(&i->rb);
+ if (!node)
+ return NULL;
+ i = rb_entry(node, struct drbd_interval, rb);
+ if (i->sector >= end)
+ return NULL;
+ if (sector < i->sector + (i->size >> 9))
+ return i;
+ }
+}