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, 7 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 46d474e74aa4..b0d49e21b0b1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2354,6 +2354,13 @@ retry_root_backup:
         fs_info->generation = generation;
         fs_info->last_trans_committed = generation;
 
+        ret = btrfs_init_dev_stats(fs_info);
+        if (ret) {
+                printk(KERN_ERR "btrfs: failed to init dev_stats: %d\n",
+                       ret);
+                goto fail_block_groups;
+        }
+
         ret = btrfs_init_space_info(fs_info);
         if (ret) {
                 printk(KERN_ERR "Failed to initial space info: %d\n", ret);