Btrfs: read device stats on mount, write modified ones during commit

The device statistics are written into the device tree with each
transaction commit. Only modified statistics are written.
When a filesystem is mounted, the device statistics for each involved
device are read from the device tree and used to initialize the
counters.

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

6 files changed, 232 insertions, 0 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index aad2600718a3..e176f8c551f7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -823,6 +823,14 @@ struct btrfs_csum_item {
         u8 csum;
 } __attribute__ ((__packed__));
 
+struct btrfs_dev_stats_item {
+        /*
+         * grow this item struct at the end for future enhancements and keep
+         * the existing values unchanged
+         */
+        __le64 values[BTRFS_DEV_STAT_VALUES_MAX];
+} __attribute__ ((__packed__));
+
 /* different types of block groups (and chunks) */
 #define BTRFS_BLOCK_GROUP_DATA          (1ULL << 0)
 #define BTRFS_BLOCK_GROUP_SYSTEM        (1ULL << 1)
@@ -1508,6 +1516,12 @@ struct btrfs_ioctl_defrag_range_args {
 #define BTRFS_BALANCE_ITEM_KEY  248
 
 /*
+ * Persistantly stores the io stats in the device tree.
+ * One key for all stats, (0, BTRFS_DEV_STATS_KEY, devid).
+ */
+#define BTRFS_DEV_STATS_KEY     249
+
+/*
  * string items are for debugging.  They just store a short string of
  * data in the FS
  */
@@ -2415,6 +2429,30 @@ static inline u32 btrfs_file_extent_inline_item_len(struct extent_buffer *eb,
         return btrfs_item_size(eb, e) - offset;
 }
 
+/* btrfs_dev_stats_item */
+static inline u64 btrfs_dev_stats_value(struct extent_buffer *eb,
+                                        struct btrfs_dev_stats_item *ptr,
+                                        int index)
+{
+        u64 val;
+
+        read_extent_buffer(eb, &val,
+                           offsetof(struct btrfs_dev_stats_item, values) +
+                            ((unsigned long)ptr) + (index * sizeof(u64)),
+                           sizeof(val));
+        return val;
+}
+
+static inline void btrfs_set_dev_stats_value(struct extent_buffer *eb,
+                                             struct btrfs_dev_stats_item *ptr,
+                                             int index, u64 val)
+{
+        write_extent_buffer(eb, &val,
+                            offsetof(struct btrfs_dev_stats_item, values) +
+                             ((unsigned long)ptr) + (index * sizeof(u64)),
+                            sizeof(val));
+}
+
 static inline struct btrfs_fs_info *btrfs_sb(struct super_block *sb)
 {
         return sb->s_fs_info;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 46d474e74aa4..b0d49e21b0b1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2354,6 +2354,13 @@ retry_root_backup:
         fs_info->generation = generation;
         fs_info->last_trans_committed = generation;
 
+        ret = btrfs_init_dev_stats(fs_info);
+        if (ret) {
+                printk(KERN_ERR "btrfs: failed to init dev_stats: %d\n",
+                       ret);
+                goto fail_block_groups;
+        }
+
         ret = btrfs_init_space_info(fs_info);
         if (ret) {
                 printk(KERN_ERR "Failed to initial space info: %d\n", ret);
diff --git a/fs/btrfs/print-tree.c b/fs/btrfs/print-tree.c
index f38e452486b8..5e23684887eb 100644
--- a/fs/btrfs/print-tree.c
+++ b/fs/btrfs/print-tree.c
@@ -294,6 +294,9 @@ void btrfs_print_leaf(struct btrfs_root *root, struct extent_buffer *l)
                                btrfs_dev_extent_chunk_offset(l, dev_extent),
                                (unsigned long long)
                                btrfs_dev_extent_length(l, dev_extent));
+                case BTRFS_DEV_STATS_KEY:
+                        printk(KERN_INFO "\t\tdevice stats\n");
+                        break;
                 };
         }
 }
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 36422254ef67..82b03afcbd92 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -28,6 +28,7 @@
 #include "locking.h"
 #include "tree-log.h"
 #include "inode-map.h"
+#include "volumes.h"
 
 #define BTRFS_ROOT_TRANS_TAG 0
 
@@ -758,6 +759,9 @@ static noinline int commit_cowonly_roots(struct btrfs_trans_handle *trans,
         if (ret)
                 return ret;
 
+        ret = btrfs_run_dev_stats(trans, root->fs_info);
+        BUG_ON(ret);
+
         while (!list_empty(&fs_info->dirty_cowonly_roots)) {
                 next = fs_info->dirty_cowonly_roots.next;
                 list_del_init(next);
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index a112b758822e..7782020996fe 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -40,6 +40,8 @@ static int init_first_rw_device(struct btrfs_trans_handle *trans,
                                 struct btrfs_root *root,
                                 struct btrfs_device *device);
 static int btrfs_relocate_sys_chunks(struct btrfs_root *root);
+static void __btrfs_reset_dev_stats(struct btrfs_device *dev);
+static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
 
 static DEFINE_MUTEX(uuid_mutex);
 static LIST_HEAD(fs_uuids);
@@ -362,6 +364,7 @@ static noinline int device_list_add(const char *path,
                         return -ENOMEM;
                 }
                 device->devid = devid;
+                device->dev_stats_valid = 0;
                 device->work.func = pending_bios_fn;
                 memcpy(device->uuid, disk_super->dev_item.uuid,
                        BTRFS_UUID_SIZE);
@@ -4654,6 +4657,162 @@ error:
         return ret;
 }
 
+static void __btrfs_reset_dev_stats(struct btrfs_device *dev)
+{
+        int i;
+
+        for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+                btrfs_dev_stat_reset(dev, i);
+}
+
+int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_key key;
+        struct btrfs_key found_key;
+        struct btrfs_root *dev_root = fs_info->dev_root;
+        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+        struct extent_buffer *eb;
+        int slot;
+        int ret = 0;
+        struct btrfs_device *device;
+        struct btrfs_path *path = NULL;
+        int i;
+
+        path = btrfs_alloc_path();
+        if (!path) {
+                ret = -ENOMEM;
+                goto out;
+        }
+
+        mutex_lock(&fs_devices->device_list_mutex);
+        list_for_each_entry(device, &fs_devices->devices, dev_list) {
+                int item_size;
+                struct btrfs_dev_stats_item *ptr;
+
+                key.objectid = 0;
+                key.type = BTRFS_DEV_STATS_KEY;
+                key.offset = device->devid;
+                ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
+                if (ret) {
+                        printk(KERN_WARNING "btrfs: no dev_stats entry found for device %s (devid %llu) (OK on first mount after mkfs)\n",
+                               device->name, (unsigned long long)device->devid);
+                        __btrfs_reset_dev_stats(device);
+                        device->dev_stats_valid = 1;
+                        btrfs_release_path(path);
+                        continue;
+                }
+                slot = path->slots[0];
+                eb = path->nodes[0];
+                btrfs_item_key_to_cpu(eb, &found_key, slot);
+                item_size = btrfs_item_size_nr(eb, slot);
+
+                ptr = btrfs_item_ptr(eb, slot,
+                                     struct btrfs_dev_stats_item);
+
+                for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
+                        if (item_size >= (1 + i) * sizeof(__le64))
+                                btrfs_dev_stat_set(device, i,
+                                        btrfs_dev_stats_value(eb, ptr, i));
+                        else
+                                btrfs_dev_stat_reset(device, i);
+                }
+
+                device->dev_stats_valid = 1;
+                btrfs_dev_stat_print_on_load(device);
+                btrfs_release_path(path);
+        }
+        mutex_unlock(&fs_devices->device_list_mutex);
+
+out:
+        btrfs_free_path(path);
+        return ret < 0 ? ret : 0;
+}
+
+static int update_dev_stat_item(struct btrfs_trans_handle *trans,
+                                struct btrfs_root *dev_root,
+                                struct btrfs_device *device)
+{
+        struct btrfs_path *path;
+        struct btrfs_key key;
+        struct extent_buffer *eb;
+        struct btrfs_dev_stats_item *ptr;
+        int ret;
+        int i;
+
+        key.objectid = 0;
+        key.type = BTRFS_DEV_STATS_KEY;
+        key.offset = device->devid;
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
+        if (ret < 0) {
+                printk(KERN_WARNING "btrfs: error %d while searching for dev_stats item for device %s!\n",
+                       ret, device->name);
+                goto out;
+        }
+
+        if (ret == 0 &&
+            btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
+                /* need to delete old one and insert a new one */
+                ret = btrfs_del_item(trans, dev_root, path);
+                if (ret != 0) {
+                        printk(KERN_WARNING "btrfs: delete too small dev_stats item for device %s failed %d!\n",
+                               device->name, ret);
+                        goto out;
+                }
+                ret = 1;
+        }
+
+        if (ret == 1) {
+                /* need to insert a new item */
+                btrfs_release_path(path);
+                ret = btrfs_insert_empty_item(trans, dev_root, path,
+                                              &key, sizeof(*ptr));
+                if (ret < 0) {
+                        printk(KERN_WARNING "btrfs: insert dev_stats item for device %s failed %d!\n",
+                               device->name, ret);
+                        goto out;
+                }
+        }
+
+        eb = path->nodes[0];
+        ptr = btrfs_item_ptr(eb, path->slots[0], struct btrfs_dev_stats_item);
+        for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+                btrfs_set_dev_stats_value(eb, ptr, i,
+                                          btrfs_dev_stat_read(device, i));
+        btrfs_mark_buffer_dirty(eb);
+
+out:
+        btrfs_free_path(path);
+        return ret;
+}
+
+/*
+ * called from commit_transaction. Writes all changed device stats to disk.
+ */
+int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *dev_root = fs_info->dev_root;
+        struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+        struct btrfs_device *device;
+        int ret = 0;
+
+        mutex_lock(&fs_devices->device_list_mutex);
+        list_for_each_entry(device, &fs_devices->devices, dev_list) {
+                if (!device->dev_stats_valid || !device->dev_stats_dirty)
+                        continue;
+
+                ret = update_dev_stat_item(trans, dev_root, device);
+                if (!ret)
+                        device->dev_stats_dirty = 0;
+        }
+        mutex_unlock(&fs_devices->device_list_mutex);
+
+        return ret;
+}
+
 void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index)
 {
         btrfs_dev_stat_inc(dev, index);
@@ -4662,6 +4821,8 @@ void btrfs_dev_stat_inc_and_print(struct btrfs_device *dev, int index)
 
 void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
 {
+        if (!dev->dev_stats_valid)
+                return;
         printk_ratelimited(KERN_ERR
                            "btrfs: bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
                            dev->name,
@@ -4674,6 +4835,17 @@ void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
                                                BTRFS_DEV_STAT_GENERATION_ERRS));
 }
 
+static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
+{
+        printk(KERN_INFO "btrfs: bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
+               dev->name,
+               btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
+               btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
+               btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
+               btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS),
+               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)
@@ -4690,6 +4862,10 @@ int btrfs_get_dev_stats(struct btrfs_root *root,
                 printk(KERN_WARNING
                        "btrfs: get dev_stats failed, device not found\n");
                 return -ENODEV;
+        } else if (!dev->dev_stats_valid) {
+                printk(KERN_WARNING
+                       "btrfs: get dev_stats failed, not yet valid\n");
+                return -ENODEV;
         } else if (reset_after_read) {
                 for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
                         if (stats->nr_items > i)
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 6798f8674b13..3406a88ca83e 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -109,6 +109,7 @@ struct btrfs_device {
 
         /* disk I/O failure stats. For detailed description refer to
          * enum btrfs_dev_stat_values in ioctl.h */
+        int dev_stats_valid;
         int dev_stats_dirty; /* counters need to be written to disk */
         atomic_t dev_stat_values[BTRFS_DEV_STAT_VALUES_MAX];
 };
@@ -293,6 +294,9 @@ 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);
+int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info);
+int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
+                        struct btrfs_fs_info *fs_info);
 
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
                                       int index)