diff options
Diffstat (limited to 'drivers/block/drbd/drbd_interval.c')
| -rw-r--r-- | drivers/block/drbd/drbd_interval.c | 207 |
1 files changed, 207 insertions, 0 deletions
diff --git a/drivers/block/drbd/drbd_interval.c b/drivers/block/drbd/drbd_interval.c new file mode 100644 index 00000000000..89c497c630b --- /dev/null +++ b/drivers/block/drbd/drbd_interval.c @@ -0,0 +1,207 @@ +#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; +} + +static void augment_propagate(struct rb_node *rb, struct rb_node *stop) +{ + while (rb != stop) { + struct drbd_interval *node = rb_entry(rb, struct drbd_interval, rb); + sector_t subtree_last = compute_subtree_last(node); + if (node->end == subtree_last) + break; + node->end = subtree_last; + rb = rb_parent(&node->rb); + } +} + +static void augment_copy(struct rb_node *rb_old, struct rb_node *rb_new) +{ + struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb); + struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb); + + new->end = old->end; +} + +static void augment_rotate(struct rb_node *rb_old, struct rb_node *rb_new) +{ + struct drbd_interval *old = rb_entry(rb_old, struct drbd_interval, rb); + struct drbd_interval *new = rb_entry(rb_new, struct drbd_interval, rb); + + new->end = old->end; + old->end = compute_subtree_last(old); +} + +static const struct rb_augment_callbacks augment_callbacks = { + augment_propagate, + augment_copy, + augment_rotate, +}; + +/** + * 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 > here) + new = &(*new)->rb_right; + else + return false; + } + + 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; + } +} |