Btrfs: kill BTRFS_I(inode)->block_group

Originally this was going to be used as a way to give hints to the allocator,
but frankly we can get much better hints elsewhere and it's not even used at all
for anything usefull.  In addition to be completely useless, when we initialize
an inode we try and find a freeish block group to set as the inodes block group,
and with a completely full 40gb fs this takes _forever_, so I imagine with say
1tb fs this is just unbearable.  So just axe the thing altoghether, we don't
need it and it saves us 8 bytes in the inode and saves us 500 microseconds per
inode lookup in my testcase.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index a578620e06a8..8e90ccf4b76a 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -413,8 +413,7 @@ static noinline int create_subvol(struct btrfs_root *root,
 
         btrfs_record_root_in_trans(trans, new_root);
 
-        ret = btrfs_create_subvol_root(trans, new_root, new_dirid,
-                                       BTRFS_I(dir)->block_group);
+        ret = btrfs_create_subvol_root(trans, new_root, new_dirid);
         /*
          * insert the directory item
          */