Btrfs: recover balance on mount

On mount, if balance item is found, resume balance in a separate
kernel thread.

Try to be smart to continue roughly where previous balance (or convert)
was interrupted.  For chunk types that were being converted to some
profile we turn on soft convert, in case of a simple balance we turn on
usage filter and relocate only less-than-90%-full chunks of that type.
These are just heuristics but they help quite a bit, and can be improved
in future.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 190a1b24c902..eb7a11ac5b73 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2427,6 +2427,10 @@ retry_root_backup:
                 if (!err)
                         err = btrfs_orphan_cleanup(fs_info->tree_root);
                 up_read(&fs_info->cleanup_work_sem);
+
+                if (!err)
+                        err = btrfs_recover_balance(fs_info->tree_root);
+
                 if (err) {
                         close_ctree(tree_root);
                         return ERR_PTR(err);