Btrfs: avoid delayed metadata items during commits

Snapshot creation has two phases.  One is the initial snapshot setup,
and the second is done during commit, while nobody is allowed to modify
the root we are snapshotting.

The delayed metadata insertion code can break that rule, it does a
delayed inode update on the inode of the parent of the snapshot,
and delayed directory item insertion.

This makes sure to run the pending delayed operations before we
record the snapshot root, which avoids corruptions.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/delayed-inode.c b/fs/btrfs/delayed-inode.c
index fc515b787e8c..f1cbd028f7b3 100644
--- a/fs/btrfs/delayed-inode.c
+++ b/fs/btrfs/delayed-inode.c
@@ -1237,6 +1237,13 @@ again:
         return 0;
 }
 
+void btrfs_assert_delayed_root_empty(struct btrfs_root *root)
+{
+        struct btrfs_delayed_root *delayed_root;
+        delayed_root = btrfs_get_delayed_root(root);
+        WARN_ON(btrfs_first_delayed_node(delayed_root));
+}
+
 void btrfs_balance_delayed_items(struct btrfs_root *root)
 {
         struct btrfs_delayed_root *delayed_root;