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>

diff --git a/drivers/md/persistent-data/dm-array.c b/drivers/md/persistent-data/dm-array.c
index 155180954cdfb308c6b7e0227c2543a326e06080..e83047cbb2daaa8cf4bdbe8e8c52512c4df8ad9f 100644 (file)
--- 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);
+
+/*----------------------------------------------------------------*/

diff --git a/drivers/md/persistent-data/dm-array.h b/drivers/md/persistent-data/dm-array.h
index 45ea3f6e1ded3f1895abd6f761a50f3ab956c54f..27ee49a5547317af5275ad2a3c4820736b330322 100644 (file)
--- a/drivers/md/persistent-data/dm-array.h
+++ b/drivers/md/persistent-data/dm-array.h
@@ -182,4 +182,37 @@ int dm_array_walk(struct dm_array_info *info, dm_block_t root,
 
 /*----------------------------------------------------------------*/
 
+/*
+ * Cursor api.
+ *
+ * This lets you iterate through all the entries in an array efficiently
+ * (it will preload metadata).
+ *
+ * I'm using a cursor, rather than a walk function with a callback because
+ * the cache target needs to iterate both the mapping and hint arrays in
+ * unison.
+ */
+struct dm_array_cursor {
+       struct dm_array_info *info;
+       struct dm_btree_cursor cursor;
+
+       struct dm_block *block;
+       struct array_block *ab;
+       unsigned index;
+};
+
+int dm_array_cursor_begin(struct dm_array_info *info,
+                         dm_block_t root, struct dm_array_cursor *c);
+void dm_array_cursor_end(struct dm_array_cursor *c);
+
+uint32_t dm_array_cursor_index(struct dm_array_cursor *c);
+int dm_array_cursor_next(struct dm_array_cursor *c);
+
+/*
+ * value_le is only valid while the cursor points at the current value.
+ */
+void dm_array_cursor_get_value(struct dm_array_cursor *c, void **value_le);
+
+/*----------------------------------------------------------------*/
+
 #endif /* _LINUX_DM_ARRAY_H */