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, 26 insertions, 0 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 15baf9456300..0f8c354c4c76 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3046,6 +3046,28 @@ static long btrfs_ioctl_scrub_progress(struct btrfs_root *root,
         return ret;
 }
 
+static long btrfs_ioctl_get_dev_stats(struct btrfs_root *root,
+                                      void __user *arg, int reset_after_read)
+{
+        struct btrfs_ioctl_get_dev_stats *sa;
+        int ret;
+
+        if (reset_after_read && !capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        sa = memdup_user(arg, sizeof(*sa));
+        if (IS_ERR(sa))
+                return PTR_ERR(sa);
+
+        ret = btrfs_get_dev_stats(root, sa, reset_after_read);
+
+        if (copy_to_user(arg, sa, sizeof(*sa)))
+                ret = -EFAULT;
+
+        kfree(sa);
+        return ret;
+}
+
 static long btrfs_ioctl_ino_to_path(struct btrfs_root *root, void __user *arg)
 {
         int ret = 0;
@@ -3434,6 +3456,10 @@ long btrfs_ioctl(struct file *file, unsigned int
                 return btrfs_ioctl_balance_ctl(root, arg);
         case BTRFS_IOC_BALANCE_PROGRESS:
                 return btrfs_ioctl_balance_progress(root, argp);
+        case BTRFS_IOC_GET_DEV_STATS:
+                return btrfs_ioctl_get_dev_stats(root, argp, 0);
+        case BTRFS_IOC_GET_AND_RESET_DEV_STATS:
+                return btrfs_ioctl_get_dev_stats(root, argp, 1);
         }
 
         return -ENOTTY;