btrfs: add and use helper to get lowest sequence number for the tree mod log

[platform/kernel/linux-rpi.git] / fs / btrfs / tree-mod-log.c

diff --git a/fs/btrfs/tree-mod-log.c b/fs/btrfs/tree-mod-log.c
index b10170e..1e52584 100644 (file)
--- a/fs/btrfs/tree-mod-log.c
+++ b/fs/btrfs/tree-mod-log.c
@@ -884,3 +884,26 @@ int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
        return level;
 }
 
+/*
+ * Return the lowest sequence number in the tree modification log.
+ *
+ * Return the sequence number of the oldest tree modification log user, which
+ * corresponds to the lowest sequence number of all existing users. If there are
+ * no users it returns 0.
+ */
+u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info)
+{
+       u64 ret = 0;
+
+       read_lock(&fs_info->tree_mod_log_lock);
+       if (!list_empty(&fs_info->tree_mod_seq_list)) {
+               struct btrfs_seq_list *elem;
+
+               elem = list_first_entry(&fs_info->tree_mod_seq_list,
+                                       struct btrfs_seq_list, list);
+               ret = elem->seq;
+       }
+       read_unlock(&fs_info->tree_mod_log_lock);
+
+       return ret;
+}