Btrfs: tree mod log sanity checks in join_transaction
When a fresh transaction begins, the tree mod log must be clean. Users of
the tree modification log must ensure they never span across transaction
boundaries.
We reset the sequence to 0 in this safe situation to make absolutely sure
overflow can't happen.
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index eb2bd82..667735f 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -122,6 +122,24 @@
cur_trans->delayed_refs.flushing = 0;
cur_trans->delayed_refs.run_delayed_start = 0;
cur_trans->delayed_refs.seq = 1;
+
+ /*
+ * although the tree mod log is per file system and not per transaction,
+ * the log must never go across transaction boundaries.
+ */
+ smp_mb();
+ if (!list_empty(&fs_info->tree_mod_seq_list)) {
+ printk(KERN_ERR "btrfs: tree_mod_seq_list not empty when "
+ "creating a fresh transaction\n");
+ WARN_ON(1);
+ }
+ if (!RB_EMPTY_ROOT(&fs_info->tree_mod_log)) {
+ printk(KERN_ERR "btrfs: tree_mod_log rb tree not empty when "
+ "creating a fresh transaction\n");
+ WARN_ON(1);
+ }
+ atomic_set(&fs_info->tree_mod_seq, 0);
+
init_waitqueue_head(&cur_trans->delayed_refs.seq_wait);
spin_lock_init(&cur_trans->commit_lock);
spin_lock_init(&cur_trans->delayed_refs.lock);