dm array: introduce cursor api

More efficient way to iterate an array due to prefetching (makes use of
the new dm_btree_cursor_* api).

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

1 files changed, 86 insertions, 0 deletions

diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c
index 155180954cdf..e83047cbb2da 100644
--- a/drivers/md/persistent-data/dm-array.c
+++ b/drivers/md/persistent-data/dm-array.c
@@ -899,3 +899,89 @@ int dm_array_walk(struct dm_array_info *info, dm_block_t root,
 EXPORT_SYMBOL_GPL(dm_array_walk);
 
 /*----------------------------------------------------------------*/
+
+static int load_ablock(struct dm_array_cursor *c)
+{
+        int r;
+        __le64 value_le;
+        uint64_t key;
+
+        if (c->block)
+                unlock_ablock(c->info, c->block);
+
+        c->block = NULL;
+        c->ab = NULL;
+        c->index = 0;
+
+        r = dm_btree_cursor_get_value(&c->cursor, &key, &value_le);
+        if (r) {
+                DMERR("dm_btree_cursor_get_value failed");
+                dm_btree_cursor_end(&c->cursor);
+
+        } else {
+                r = get_ablock(c->info, le64_to_cpu(value_le), &c->block, &c->ab);
+                if (r) {
+                        DMERR("get_ablock failed");
+                        dm_btree_cursor_end(&c->cursor);
+                }
+        }
+
+        return r;
+}
+
+int dm_array_cursor_begin(struct dm_array_info *info, dm_block_t root,
+                          struct dm_array_cursor *c)
+{
+        int r;
+
+        memset(c, 0, sizeof(*c));
+        c->info = info;
+        r = dm_btree_cursor_begin(&info->btree_info, root, true, &c->cursor);
+        if (r) {
+                DMERR("couldn't create btree cursor");
+                return r;
+        }
+
+        return load_ablock(c);
+}
+EXPORT_SYMBOL_GPL(dm_array_cursor_begin);
+
+void dm_array_cursor_end(struct dm_array_cursor *c)
+{
+        if (c->block) {
+                unlock_ablock(c->info, c->block);
+                dm_btree_cursor_end(&c->cursor);
+        }
+}
+EXPORT_SYMBOL_GPL(dm_array_cursor_end);
+
+int dm_array_cursor_next(struct dm_array_cursor *c)
+{
+        int r;
+
+        if (!c->block)
+                return -ENODATA;
+
+        c->index++;
+
+        if (c->index >= le32_to_cpu(c->ab->nr_entries)) {
+                r = dm_btree_cursor_next(&c->cursor);
+                if (r)
+                        return r;
+
+                r = load_ablock(c);
+                if (r)
+                        return r;
+        }
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(dm_array_cursor_next);
+
+void dm_array_cursor_get_value(struct dm_array_cursor *c, void **value_le)
+{
+        *value_le = element_at(c->info, c->ab, c->index);
+}
+EXPORT_SYMBOL_GPL(dm_array_cursor_get_value);
+
+/*----------------------------------------------------------------*/