Btrfs: do not needlessly restart the transaction for enospc

We will stop and restart a transaction every time we move to a different leaf
when truncating a file.  This is for enospc reasons, but really we could
probably get away with doing this a little better by actually working until we
hit an ENOSPC.  So add a ->failfast flag to the block_rsv and set it when we do
truncates which will fail as soon as the block rsv runs out of space, and then
at that point we can stop and restart the transaction and refill the block rsv
and carry on.  This will make rm'ing of a file with lots of extents a bit
faster.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4b81ea3fa1b..81c772b5dc8 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1034,6 +1034,7 @@ struct btrfs_block_rsv {
         struct btrfs_space_info *space_info;
         spinlock_t lock;
         unsigned int full;
+        unsigned int failfast;
 };
 
 /*