Btrfs: add basic restriper infrastructure

Add basic restriper infrastructure: extended balancing ioctl and all
related ioctl data structures, add data structure for tracking
restriper's state to fs_info, etc.  The semantics of the old balancing
ioctl are fully preserved.

Explicitly disallow any volume operations when balance is in progress.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ce9d0fb3627d..190a1b24c902 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2002,6 +2002,10 @@ struct btrfs_root *open_ctree(struct super_block *sb,
         init_rwsem(&fs_info->scrub_super_lock);
         fs_info->scrub_workers_refcnt = 0;
 
+        spin_lock_init(&fs_info->balance_lock);
+        mutex_init(&fs_info->balance_mutex);
+        fs_info->balance_ctl = NULL;
+
         sb->s_blocksize = 4096;
         sb->s_blocksize_bits = blksize_bits(4096);
         sb->s_bdi = &fs_info->bdi;