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>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 15baf94..0f8c354 100644 (file)
--- 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 5bf05e2..497c530 100644 (file)
--- 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 2915521..a112b75 100644 (file)
--- 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 193b283..6798f86 100644 (file)
--- 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)