dm btree: add dm_btree_find_lowest_key

dm_btree_find_lowest_key is the reciprocal of dm_btree_find_highest_key.
Factor out common code for dm_btree_find_{highest,lowest}_key.

dm_btree_find_lowest_key is needed for an upcoming DM target, as such it
is best to get this interface in place.

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

2 files changed, 34 insertions, 7 deletions

diff --git a/drivers/md/persistent-data/dm-btree.c b/drivers/md/persistent-data/dm-btree.c
index 468e371ee9b2..416060c25709 100644
--- a/drivers/md/persistent-data/dm-btree.c
+++ b/drivers/md/persistent-data/dm-btree.c
@@ -770,8 +770,8 @@ EXPORT_SYMBOL_GPL(dm_btree_insert_notify);
 
 /*----------------------------------------------------------------*/
 
-static int find_highest_key(struct ro_spine *s, dm_block_t block,
-                            uint64_t *result_key, dm_block_t *next_block)
+static int find_key(struct ro_spine *s, dm_block_t block, bool find_highest,
+                    uint64_t *result_key, dm_block_t *next_block)
 {
         int i, r;
         uint32_t flags;
@@ -788,7 +788,11 @@ static int find_highest_key(struct ro_spine *s, dm_block_t block,
                 else
                         i--;
 
-                *result_key = le64_to_cpu(ro_node(s)->keys[i]);
+                if (find_highest)
+                        *result_key = le64_to_cpu(ro_node(s)->keys[i]);
+                else
+                        *result_key = le64_to_cpu(ro_node(s)->keys[0]);
+
                 if (next_block || flags & INTERNAL_NODE)
                         block = value64(ro_node(s), i);
 
@@ -799,16 +803,16 @@ static int find_highest_key(struct ro_spine *s, dm_block_t block,
         return 0;
 }
 
-int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
-                              uint64_t *result_keys)
+static int dm_btree_find_key(struct dm_btree_info *info, dm_block_t root,
+                             bool find_highest, uint64_t *result_keys)
 {
         int r = 0, count = 0, level;
         struct ro_spine spine;
 
         init_ro_spine(&spine, info);
         for (level = 0; level < info->levels; level++) {
-                r = find_highest_key(&spine, root, result_keys + level,
-                                     level == info->levels - 1 ? NULL : &root);
+                r = find_key(&spine, root, find_highest, result_keys + level,
+                             level == info->levels - 1 ? NULL : &root);
                 if (r == -ENODATA) {
                         r = 0;
                         break;
@@ -822,8 +826,23 @@ int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
 
         return r ? r : count;
 }
+
+int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,
+                              uint64_t *result_keys)
+{
+        return dm_btree_find_key(info, root, true, result_keys);
+}
 EXPORT_SYMBOL_GPL(dm_btree_find_highest_key);
 
+int dm_btree_find_lowest_key(struct dm_btree_info *info, dm_block_t root,
+                             uint64_t *result_keys)
+{
+        return dm_btree_find_key(info, root, false, result_keys);
+}
+EXPORT_SYMBOL_GPL(dm_btree_find_lowest_key);
+
+/*----------------------------------------------------------------*/
+
 /*
  * FIXME: We shouldn't use a recursive algorithm when we have limited stack
  * space.  Also this only works for single level trees.
diff --git a/drivers/md/persistent-data/dm-btree.h b/drivers/md/persistent-data/dm-btree.h
index 8672d159e0b5..dacfc34180b4 100644
--- a/drivers/md/persistent-data/dm-btree.h
+++ b/drivers/md/persistent-data/dm-btree.h
@@ -137,6 +137,14 @@ int dm_btree_remove(struct dm_btree_info *info, dm_block_t root,
 /*
  * Returns < 0 on failure.  Otherwise the number of key entries that have
  * been filled out.  Remember trees can have zero entries, and as such have
+ * no lowest key.
+ */
+int dm_btree_find_lowest_key(struct dm_btree_info *info, dm_block_t root,
+                             uint64_t *result_keys);
+
+/*
+ * Returns < 0 on failure.  Otherwise the number of key entries that have
+ * been filled out.  Remember trees can have zero entries, and as such have
  * no highest key.
  */
 int dm_btree_find_highest_key(struct dm_btree_info *info, dm_block_t root,