dm persistent data: add btree_walk

Add dm_btree_walk to iterate through the contents of a btree.
This will be used by the dm cache target.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

4 files changed, 69 insertions, 0 deletions

diff --git a/drivers/md/persistent-data/dm-btree-internal.h b/drivers/md/persistent-data/dm-btree-internal.h
index accbb05f17b6..37d367bb9aa8 100644
--- a/drivers/md/persistent-data/dm-btree-internal.h
+++ b/drivers/md/persistent-data/dm-btree-internal.h
@@ -64,6 +64,7 @@ struct ro_spine {
 void init_ro_spine(struct ro_spine *s, struct dm_btree_info *info);
 int exit_ro_spine(struct ro_spine *s);
 int ro_step(struct ro_spine *s, dm_block_t new_child);
+void ro_pop(struct ro_spine *s);
 struct btree_node *ro_node(struct ro_spine *s);
 
 struct shadow_spine {
diff --git a/drivers/md/persistent-data/dm-btree-spine.c b/drivers/md/persistent-data/dm-btree-spine.c
index f199a0c4ed04..cf9fd676ae44 100644
--- a/drivers/md/persistent-data/dm-btree-spine.c
+++ b/drivers/md/persistent-data/dm-btree-spine.c
@@ -164,6 +164,13 @@ int ro_step(struct ro_spine *s, dm_block_t new_child)
         return r;
 }
 
+void ro_pop(struct ro_spine *s)
+{
+        BUG_ON(!s->count);
+        --s->count;
+        unlock_block(s->info, s->nodes[s->count]);
+}
+
 struct btree_node *ro_node(struct ro_spine *s)
 {
         struct dm_block *block;
diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index 4caf66918cdb..35865425e4b4 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -807,3 +807,55 @@ int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
         return r ? r : count;
 }
 EXPORT_SYMBOL_GPL(dm_btree_find_highest_key);
+
+/*
+ * FIXME: We shouldn't use a recursive algorithm when we have limited stack
+ * space.  Also this only works for single level trees.
+ */
+static int walk_node(struct ro_spine *s, dm_block_t block,
+                     int (*fn)(void *context, uint64_t *keys, void *leaf),
+                     void *context)
+{
+        int r;
+        unsigned i, nr;
+        struct btree_node *n;
+        uint64_t keys;
+
+        r = ro_step(s, block);
+        n = ro_node(s);
+
+        nr = le32_to_cpu(n->header.nr_entries);
+        for (i = 0; i < nr; i++) {
+                if (le32_to_cpu(n->header.flags) & INTERNAL_NODE) {
+                        r = walk_node(s, value64(n, i), fn, context);
+                        if (r)
+                                goto out;
+                } else {
+                        keys = le64_to_cpu(*key_ptr(n, i));
+                        r = fn(context, &keys, value_ptr(n, i));
+                        if (r)
+                                goto out;
+                }
+        }
+
+out:
+        ro_pop(s);
+        return r;
+}
+
+int dm_btree_walk(struct dm_btree_info *info, dm_block_t root,
+                  int (*fn)(void *context, uint64_t *keys, void *leaf),
+                  void *context)
+{
+        int r;
+        struct ro_spine spine;
+
+        BUG_ON(info->levels > 1);
+
+        init_ro_spine(&spine, info);
+        r = walk_node(&spine, root, fn, context);
+        exit_ro_spine(&spine);
+
+        return r;
+}
+EXPORT_SYMBOL_GPL(dm_btree_walk);
diff --git a/drivers/md/persistent-data/dm-btree.h b/drivers/md/persistent-data/dm-btree.h
index fced8316bca2..8672d159e0b5 100644
--- a/drivers/md/persistent-data/dm-btree.h
+++ b/drivers/md/persistent-data/dm-btree.h
@@ -142,4 +142,13 @@ int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
 int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
                               uint64_t *result_keys);
 
+/*
+ * Iterate through the a btree, calling fn() on each entry.
+ * It only works for single level trees and is internally recursive, so
+ * monitor stack usage carefully.
+ */
+int dm_btree_walk(struct dm_btree_info *info, dm_block_t root,
+                  int (*fn)(void *context, uint64_t *keys, void *leaf),
+                  void *context);
+
 #endif  /* _LINUX_DM_BTREE_H */