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, 34 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 2915521f44ee..a112b758822e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4673,3 +4673,37 @@ void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
                            btrfs_dev_stat_read(dev,
                                                BTRFS_DEV_STAT_GENERATION_ERRS));
 }
+
+int btrfs_get_dev_stats(struct btrfs_root *root,
+                        struct btrfs_ioctl_get_dev_stats *stats,
+                        int reset_after_read)
+{
+        struct btrfs_device *dev;
+        struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
+        int i;
+
+        mutex_lock(&fs_devices->device_list_mutex);
+        dev = btrfs_find_device(root, stats->devid, NULL, NULL);
+        mutex_unlock(&fs_devices->device_list_mutex);
+
+        if (!dev) {
+                printk(KERN_WARNING
+                       "btrfs: get dev_stats failed, device not found\n");
+                return -ENODEV;
+        } else if (reset_after_read) {
+                for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
+                        if (stats->nr_items > i)
+                                stats->values[i] =
+                                        btrfs_dev_stat_read_and_reset(dev, i);
+                        else
+                                btrfs_dev_stat_reset(dev, i);
+                }
+        } else {
+                for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+                        if (stats->nr_items > i)
+                                stats->values[i] = btrfs_dev_stat_read(dev, i);
+        }
+        if (stats->nr_items > BTRFS_DEV_STAT_VALUES_MAX)
+                stats->nr_items = BTRFS_DEV_STAT_VALUES_MAX;
+        return 0;
+}