btrfs_start_transaction: wait for commits in progress to finish

btrfs_commit_transaction has to loop waiting for any writers in the
transaction to finish before it can proceed.  btrfs_start_transaction
should be polite and not join a transaction that is in the process
of being finished off.

There are a few places that can't wait, basically the ones doing IO that
might be needed to finish the transaction.  For them, btrfs_join_transaction
is added.

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

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4ddc8a8f82cd..acbce542d291 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -513,6 +513,7 @@ struct btrfs_fs_info {
         u64 alloc_start;
         struct btrfs_transaction *running_transaction;
         wait_queue_head_t transaction_throttle;
+        wait_queue_head_t transaction_wait;
         struct btrfs_super_block super_copy;
         struct btrfs_super_block super_for_commit;
         struct block_device *__bdev;