btrfs-progs: balance filter: add limit of processed chunks

Add more control to the balance behaviour.

Usage filter may not be finegrained enough and can lead to moving too
many chunks at once. Another example use is in connection with
drange+devid or vrange filters that allow to work with a specific chunk
or even with a chunk on a given device.

The limit filter applies last, the value of 0 means no limiting.

CC: Ilya Dryomov <idryomov@gmail.com>
CC: Hugo Mills <hugo@carfax.org.uk>
Signed-off-by: David Sterba <dsterba@suse.cz>

1 files changed, 3 insertions, 1 deletions

diff --git a/ioctl.h b/ioctl.h
index 9627e8d1..f0fc0608 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -194,7 +194,9 @@ struct btrfs_balance_args {
 
 	__u64 flags;
 
-	__u64 unused[8];
+	__u64 limit;
+
+	__u64 unused[7];
 } __attribute__ ((__packed__));
 
 struct btrfs_balance_progress {