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, 3 insertions, 0 deletions

diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 910350cd4cf0..11fbdeceb26c 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -27,6 +27,7 @@ struct btrfs_transaction {
         int in_commit;
         int use_count;
         int commit_done;
+        int blocked;
         struct list_head list;
         struct extent_io_tree dirty_pages;
         unsigned long start_time;
@@ -75,6 +76,8 @@ int btrfs_end_transaction(struct btrfs_trans_handle *trans,
                           struct btrfs_root *root);
 struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
                                                    int num_blocks);
+struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root,
+                                                   int num_blocks);
 int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans,
                                      struct btrfs_root *root);
 int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans,