Btrfs: Metadata ENOSPC handling for balance

This patch adds metadata ENOSPC handling for the balance code.
It is consisted by following major changes:

1. Avoid COW tree leave in the phrase of merging tree.

2. Handle interaction with snapshot creation.

3. make the backref cache can live across transactions.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index cfe7f588ef05..c346d320173a 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -853,6 +853,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
                 goto fail;
         }
 
+        btrfs_reloc_pre_snapshot(trans, pending, &to_reserve);
         btrfs_orphan_pre_snapshot(trans, pending, &to_reserve);
 
         if (to_reserve > 0) {
@@ -924,6 +925,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         pending->snap = btrfs_read_fs_root_no_name(root->fs_info, &key);
         BUG_ON(IS_ERR(pending->snap));
 
+        btrfs_reloc_post_snapshot(trans, pending);
         btrfs_orphan_post_snapshot(trans, pending);
 fail:
         kfree(new_root_item);
@@ -1213,9 +1215,9 @@ int btrfs_clean_old_snapshots(struct btrfs_root *root)
 
                 if (btrfs_header_backref_rev(root->node) <
                     BTRFS_MIXED_BACKREF_REV)
-                        btrfs_drop_snapshot(root, 0);
+                        btrfs_drop_snapshot(root, NULL, 0);
                 else
-                        btrfs_drop_snapshot(root, 1);
+                        btrfs_drop_snapshot(root, NULL, 1);
         }
         return 0;
 }