The freeze rwsem is taken by sb_start_intwrite() and dropped during the
commit_ or end_transaction(). In the async case, that happens in a worker
thread. Tell lockdep the calling thread is releasing ownership of the
rwsem and the async thread is picking it up.
XFS plays the same trick in fs/xfs/xfs_aops.c.
Signed-off-by: Sage Weil <s...@inktank.com>
---
fs/btrfs/transaction.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 17be3de..efc41a5 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -1228,6 +1228,14 @@ static void do_async_commit(struct work_struct *work)
struct btrfs_async_commit *ac =
container_of(work, struct btrfs_async_commit, work.work);
+ /*
+ * We've got freeze protection passed with the transaction.
+ * Tell lockdep about it.
+ */
+ rwsem_acquire_read(
+ &ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+ 0, 1, _THIS_IP_);
+
btrfs_commit_transaction(ac->newtrans, ac->root);
kfree(ac);
}
@@ -1257,6 +1265,14 @@ int btrfs_commit_transaction_async(struct
btrfs_trans_handle *trans,
atomic_inc(&cur_trans->use_count);
btrfs_end_transaction(trans, root);
+
+ /*
+ * Tell lockdep we've released the freeze rwsem, since the
+ * async commit thread will be the one to unlock it.
+ */
+ rwsem_release(&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
+ 1, _THIS_IP_);
+
schedule_delayed_work(&ac->work, 0);
/* wait for transaction to start and unblock */
--
1.7.9.5
--
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