Btrfs: delay block group item insertion

So we have lots of places where we try to preallocate chunks in order to
make sure we have enough space as we make our allocations.  This has
historically meant that we're constantly tweaking when we should allocate a
new chunk, and historically we have gotten this horribly wrong so we way
over allocate either metadata or data.  To try and keep this from happening
we are going to make it so that the block group item insertion is done out
of band at the end of a transaction.  This will allow us to create chunks
even if we are trying to make an allocation for the extent tree.  With this
patch my enospc tests run faster (didn't expect this) and more efficiently
use the disk space (this is what I wanted).  Thanks,

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

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 305002b7bf3a..d66dc1c6a40d 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1137,6 +1137,9 @@ struct btrfs_block_group_cache {
 	 * Today it will only have one thing on it, but that may change
 	 */
 	struct list_head cluster_list;
+
+	/* For delayed block group creation */
+	struct list_head new_bg_list;
 };
 
 /* delayed seq elem */
@@ -2865,6 +2868,8 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
 			   u64 size);
 int btrfs_remove_block_group(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root, u64 group_start);
+void btrfs_create_pending_block_groups(struct btrfs_trans_handle *trans,
+				       struct btrfs_root *root);
 u64 btrfs_reduce_alloc_profile(struct btrfs_root *root, u64 flags);
 u64 btrfs_get_alloc_profile(struct btrfs_root *root, int data);
 void btrfs_clear_space_info_full(struct btrfs_fs_info *info);