4 files changed, 77 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;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 5bf05e28b829..497c530724cf 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -285,6 +285,16 @@ enum btrfs_dev_stat_values {
         BTRFS_DEV_STAT_VALUES_MAX
 };
 
+struct btrfs_ioctl_get_dev_stats {
+        __u64 devid;                            /* in */
+        __u64 nr_items;                         /* in/out */
+
+        /* out values: */
+        __u64 values[BTRFS_DEV_STAT_VALUES_MAX];
+
+        __u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX]; /* pad to 1k */
+};
+
 #define BTRFS_IOC_SNAP_CREATE _IOW(BTRFS_IOCTL_MAGIC, 1, \
                                    struct btrfs_ioctl_vol_args)
 #define BTRFS_IOC_DEFRAG _IOW(BTRFS_IOCTL_MAGIC, 2, \
@@ -349,5 +359,9 @@ enum btrfs_dev_stat_values {
                                         struct btrfs_ioctl_ino_path_args)
 #define BTRFS_IOC_LOGICAL_INO _IOWR(BTRFS_IOCTL_MAGIC, 36, \
                                         struct btrfs_ioctl_ino_path_args)
+#define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
+                                      struct btrfs_ioctl_get_dev_stats)
+#define BTRFS_IOC_GET_AND_RESET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 53, \
+                                        struct btrfs_ioctl_get_dev_stats)
 
 #endif
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;
+}
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)