Btrfs: read device stats on mount, write modified ones during commit

The device statistics are written into the device tree with each
transaction commit. Only modified statistics are written.
When a filesystem is mounted, the device statistics for each involved
device are read from the device tree and used to initialize the
counters.

Signed-off-by: Stefan Behrens <sbehrens@giantdisaster.de>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index f38e452486b8..5e23684887eb 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -294,6 +294,9 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
                                btrfs_dev_extent_chunk_offset(l, dev_extent),
                                (unsigned long long)
                                btrfs_dev_extent_length(l, dev_extent));
+                case BTRFS_DEV_STATS_KEY:
+                        printk(KERN_INFO "\t\tdevice stats\n");
+                        break;
                 };
         }
 }