Btrfs: add ioctl to get and reset the device stats

An ioctl interface is added to get the device statistic counters.
A second ioctl is added to atomically get and reset these counters.

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

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 193b2835e6ae..6798f8674b13 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -290,6 +290,9 @@ struct btrfs_device *btrfs_find_device_for_logical(struct btrfs_root *root,
                                                    u64 logical, int mirror_num);
 void btrfs_dev_stat_print_on_error(struct btrfs_device *device);
 void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index);
+int btrfs_get_dev_stats(struct btrfs_root *root,
+                        struct btrfs_ioctl_get_dev_stats *stats,
+                        int reset_after_read);
 
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
                                       int index)