X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=fs%2Fbtrfs%2Fvolumes.c;h=ecaad40e7ef499fedb7667659d9efd955a661eaa;hb=2b6ba629b5aac51e7099efbb43e2b403213aa7fb;hp=759d02486d7ccb2dcb2ff1b1334396cc219880ca;hpb=3b422e9c2c020a1137349c614da7f9c9761a0922;p=firefly-linux-kernel-4.4.55.git

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 759d02486d7c..ecaad40e7ef4 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -23,6 +23,7 @@
 #include <linux/random.h>
 #include <linux/iocontext.h>
 #include <linux/capability.h>
+#include <linux/ratelimit.h>
 #include <linux/kthread.h>
 #include <asm/div64.h>
 #include "compat.h"
@@ -34,11 +35,14 @@
 #include "volumes.h"
 #include "async-thread.h"
 #include "check-integrity.h"
+#include "rcu-string.h"
 
 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);
@@ -61,7 +65,7 @@ static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
 		device = list_entry(fs_devices->devices.next,
 				    struct btrfs_device, dev_list);
 		list_del(&device->dev_list);
-		kfree(device->name);
+		rcu_string_free(device->name);
 		kfree(device);
 	}
 	kfree(fs_devices);
@@ -331,8 +335,8 @@ static noinline int device_list_add(const char *path,
 {
 	struct btrfs_device *device;
 	struct btrfs_fs_devices *fs_devices;
+	struct rcu_string *name;
 	u64 found_transid = btrfs_super_generation(disk_super);
-	char *name;
 
 	fs_devices = find_fsid(disk_super->fsid);
 	if (!fs_devices) {
@@ -361,15 +365,18 @@ 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);
 		spin_lock_init(&device->io_lock);
-		device->name = kstrdup(path, GFP_NOFS);
-		if (!device->name) {
+
+		name = rcu_string_strdup(path, GFP_NOFS);
+		if (!name) {
 			kfree(device);
 			return -ENOMEM;
 		}
+		rcu_assign_pointer(device->name, name);
 		INIT_LIST_HEAD(&device->dev_alloc_list);
 
 		/* init readahead state */
@@ -386,12 +393,12 @@ static noinline int device_list_add(const char *path,
 
 		device->fs_devices = fs_devices;
 		fs_devices->num_devices++;
-	} else if (!device->name || strcmp(device->name, path)) {
-		name = kstrdup(path, GFP_NOFS);
+	} else if (!device->name || strcmp(device->name->str, path)) {
+		name = rcu_string_strdup(path, GFP_NOFS);
 		if (!name)
 			return -ENOMEM;
-		kfree(device->name);
-		device->name = name;
+		rcu_string_free(device->name);
+		rcu_assign_pointer(device->name, name);
 		if (device->missing) {
 			fs_devices->missing_devices--;
 			device->missing = 0;
@@ -426,15 +433,22 @@ static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
 
 	/* We have held the volume lock, it is safe to get the devices. */
 	list_for_each_entry(orig_dev, &orig->devices, dev_list) {
+		struct rcu_string *name;
+
 		device = kzalloc(sizeof(*device), GFP_NOFS);
 		if (!device)
 			goto error;
 
-		device->name = kstrdup(orig_dev->name, GFP_NOFS);
-		if (!device->name) {
+		/*
+		 * This is ok to do without rcu read locked because we hold the
+		 * uuid mutex so nothing we touch in here is going to disappear.
+		 */
+		name = rcu_string_strdup(orig_dev->name->str, GFP_NOFS);
+		if (!name) {
 			kfree(device);
 			goto error;
 		}
+		rcu_assign_pointer(device->name, name);
 
 		device->devid = orig_dev->devid;
 		device->work.func = pending_bios_fn;
@@ -487,7 +501,7 @@ again:
 		}
 		list_del_init(&device->dev_list);
 		fs_devices->num_devices--;
-		kfree(device->name);
+		rcu_string_free(device->name);
 		kfree(device);
 	}
 
@@ -512,7 +526,7 @@ static void __free_device(struct work_struct *work)
 	if (device->bdev)
 		blkdev_put(device->bdev, device->mode);
 
-	kfree(device->name);
+	rcu_string_free(device->name);
 	kfree(device);
 }
 
@@ -536,6 +550,7 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 	mutex_lock(&fs_devices->device_list_mutex);
 	list_for_each_entry(device, &fs_devices->devices, dev_list) {
 		struct btrfs_device *new_device;
+		struct rcu_string *name;
 
 		if (device->bdev)
 			fs_devices->open_devices--;
@@ -551,8 +566,11 @@ static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
 		new_device = kmalloc(sizeof(*new_device), GFP_NOFS);
 		BUG_ON(!new_device); /* -ENOMEM */
 		memcpy(new_device, device, sizeof(*new_device));
-		new_device->name = kstrdup(device->name, GFP_NOFS);
-		BUG_ON(device->name && !new_device->name); /* -ENOMEM */
+
+		/* Safe because we are under uuid_mutex */
+		name = rcu_string_strdup(device->name->str, GFP_NOFS);
+		BUG_ON(device->name && !name); /* -ENOMEM */
+		rcu_assign_pointer(new_device->name, name);
 		new_device->bdev = NULL;
 		new_device->writeable = 0;
 		new_device->in_fs_metadata = 0;
@@ -617,9 +635,9 @@ static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		if (!device->name)
 			continue;
 
-		bdev = blkdev_get_by_path(device->name, flags, holder);
+		bdev = blkdev_get_by_path(device->name->str, flags, holder);
 		if (IS_ERR(bdev)) {
-			printk(KERN_INFO "open %s failed\n", device->name);
+			printk(KERN_INFO "open %s failed\n", device->name->str);
 			goto error;
 		}
 		filemap_write_and_wait(bdev->bd_inode->i_mapping);
@@ -1628,12 +1646,13 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 	struct block_device *bdev;
 	struct list_head *devices;
 	struct super_block *sb = root->fs_info->sb;
+	struct rcu_string *name;
 	u64 total_bytes;
 	int seeding_dev = 0;
 	int ret = 0;
 
 	if ((sb->s_flags & MS_RDONLY) && !root->fs_info->fs_devices->seeding)
-		return -EINVAL;
+		return -EROFS;
 
 	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
 				  root->fs_info->bdev_holder);
@@ -1667,23 +1686,24 @@ int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
 		goto error;
 	}
 
-	device->name = kstrdup(device_path, GFP_NOFS);
-	if (!device->name) {
+	name = rcu_string_strdup(device_path, GFP_NOFS);
+	if (!name) {
 		kfree(device);
 		ret = -ENOMEM;
 		goto error;
 	}
+	rcu_assign_pointer(device->name, name);
 
 	ret = find_next_devid(root, &device->devid);
 	if (ret) {
-		kfree(device->name);
+		rcu_string_free(device->name);
 		kfree(device);
 		goto error;
 	}
 
 	trans = btrfs_start_transaction(root, 0);
 	if (IS_ERR(trans)) {
-		kfree(device->name);
+		rcu_string_free(device->name);
 		kfree(device);
 		ret = PTR_ERR(trans);
 		goto error;
@@ -1792,7 +1812,7 @@ error_trans:
 	unlock_chunks(root);
 	btrfs_abort_transaction(trans, root, ret);
 	btrfs_end_transaction(trans, root);
-	kfree(device->name);
+	rcu_string_free(device->name);
 	kfree(device);
 error:
 	blkdev_put(bdev, FMODE_EXCL);
@@ -2825,31 +2845,48 @@ out:
 
 static int balance_kthread(void *data)
 {
-	struct btrfs_balance_control *bctl =
-			(struct btrfs_balance_control *)data;
-	struct btrfs_fs_info *fs_info = bctl->fs_info;
+	struct btrfs_fs_info *fs_info = data;
 	int ret = 0;
 
 	mutex_lock(&fs_info->volume_mutex);
 	mutex_lock(&fs_info->balance_mutex);
 
-	set_balance_control(bctl);
-
-	if (btrfs_test_opt(fs_info->tree_root, SKIP_BALANCE)) {
-		printk(KERN_INFO "btrfs: force skipping balance\n");
-	} else {
+	if (fs_info->balance_ctl) {
 		printk(KERN_INFO "btrfs: continuing balance\n");
-		ret = btrfs_balance(bctl, NULL);
+		ret = btrfs_balance(fs_info->balance_ctl, NULL);
 	}
 
 	mutex_unlock(&fs_info->balance_mutex);
 	mutex_unlock(&fs_info->volume_mutex);
+
 	return ret;
 }
 
-int btrfs_recover_balance(struct btrfs_root *tree_root)
+int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
 {
 	struct task_struct *tsk;
+
+	spin_lock(&fs_info->balance_lock);
+	if (!fs_info->balance_ctl) {
+		spin_unlock(&fs_info->balance_lock);
+		return 0;
+	}
+	spin_unlock(&fs_info->balance_lock);
+
+	if (btrfs_test_opt(fs_info->tree_root, SKIP_BALANCE)) {
+		printk(KERN_INFO "btrfs: force skipping balance\n");
+		return 0;
+	}
+
+	tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
+	if (IS_ERR(tsk))
+		return PTR_ERR(tsk);
+
+	return 0;
+}
+
+int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
+{
 	struct btrfs_balance_control *bctl;
 	struct btrfs_balance_item *item;
 	struct btrfs_disk_balance_args disk_bargs;
@@ -2862,29 +2899,30 @@ int btrfs_recover_balance(struct btrfs_root *tree_root)
 	if (!path)
 		return -ENOMEM;
 
-	bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
-	if (!bctl) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
 	key.objectid = BTRFS_BALANCE_OBJECTID;
 	key.type = BTRFS_BALANCE_ITEM_KEY;
 	key.offset = 0;
 
-	ret = btrfs_search_slot(NULL, tree_root, &key, path, 0, 0);
+	ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
 	if (ret < 0)
-		goto out_bctl;
+		goto out;
 	if (ret > 0) { /* ret = -ENOENT; */
 		ret = 0;
-		goto out_bctl;
+		goto out;
+	}
+
+	bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
+	if (!bctl) {
+		ret = -ENOMEM;
+		goto out;
 	}
 
 	leaf = path->nodes[0];
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_balance_item);
 
-	bctl->fs_info = tree_root->fs_info;
-	bctl->flags = btrfs_balance_flags(leaf, item) | BTRFS_BALANCE_RESUME;
+	bctl->fs_info = fs_info;
+	bctl->flags = btrfs_balance_flags(leaf, item);
+	bctl->flags |= BTRFS_BALANCE_RESUME;
 
 	btrfs_balance_data(leaf, item, &disk_bargs);
 	btrfs_disk_balance_args_to_cpu(&bctl->data, &disk_bargs);
@@ -2893,14 +2931,13 @@ int btrfs_recover_balance(struct btrfs_root *tree_root)
 	btrfs_balance_sys(leaf, item, &disk_bargs);
 	btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
 
-	tsk = kthread_run(balance_kthread, bctl, "btrfs-balance");
-	if (IS_ERR(tsk))
-		ret = PTR_ERR(tsk);
-	else
-		goto out;
+	mutex_lock(&fs_info->volume_mutex);
+	mutex_lock(&fs_info->balance_mutex);
 
-out_bctl:
-	kfree(bctl);
+	set_balance_control(bctl);
+
+	mutex_unlock(&fs_info->balance_mutex);
+	mutex_unlock(&fs_info->volume_mutex);
 out:
 	btrfs_free_path(path);
 	return ret;
@@ -3324,12 +3361,14 @@ static int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
 	stripe_size = devices_info[ndevs-1].max_avail;
 	num_stripes = ndevs * dev_stripes;
 
-	if (stripe_size * num_stripes > max_chunk_size * ncopies) {
+	if (stripe_size * ndevs > max_chunk_size * ncopies) {
 		stripe_size = max_chunk_size * ncopies;
-		do_div(stripe_size, num_stripes);
+		do_div(stripe_size, ndevs);
 	}
 
 	do_div(stripe_size, dev_stripes);
+
+	/* align to BTRFS_STRIPE_LEN */
 	do_div(stripe_size, BTRFS_STRIPE_LEN);
 	stripe_size *= BTRFS_STRIPE_LEN;
 
@@ -3805,10 +3844,11 @@ static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
 		else if (mirror_num)
 			stripe_index += mirror_num - 1;
 		else {
+			int old_stripe_index = stripe_index;
 			stripe_index = find_live_mirror(map, stripe_index,
 					      map->sub_stripes, stripe_index +
 					      current->pid % map->sub_stripes);
-			mirror_num = stripe_index + 1;
+			mirror_num = stripe_index - old_stripe_index + 1;
 		}
 	} else {
 		/*
@@ -3998,13 +4038,60 @@ int btrfs_rmap_block(struct btrfs_mapping_tree *map_tree,
 	return 0;
 }
 
+static void *merge_stripe_index_into_bio_private(void *bi_private,
+						 unsigned int stripe_index)
+{
+	/*
+	 * with single, dup, RAID0, RAID1 and RAID10, stripe_index is
+	 * at most 1.
+	 * The alternative solution (instead of stealing bits from the
+	 * pointer) would be to allocate an intermediate structure
+	 * that contains the old private pointer plus the stripe_index.
+	 */
+	BUG_ON((((uintptr_t)bi_private) & 3) != 0);
+	BUG_ON(stripe_index > 3);
+	return (void *)(((uintptr_t)bi_private) | stripe_index);
+}
+
+static struct btrfs_bio *extract_bbio_from_bio_private(void *bi_private)
+{
+	return (struct btrfs_bio *)(((uintptr_t)bi_private) & ~((uintptr_t)3));
+}
+
+static unsigned int extract_stripe_index_from_bio_private(void *bi_private)
+{
+	return (unsigned int)((uintptr_t)bi_private) & 3;
+}
+
 static void btrfs_end_bio(struct bio *bio, int err)
 {
-	struct btrfs_bio *bbio = bio->bi_private;
+	struct btrfs_bio *bbio = extract_bbio_from_bio_private(bio->bi_private);
 	int is_orig_bio = 0;
 
-	if (err)
+	if (err) {
 		atomic_inc(&bbio->error);
+		if (err == -EIO || err == -EREMOTEIO) {
+			unsigned int stripe_index =
+				extract_stripe_index_from_bio_private(
+					bio->bi_private);
+			struct btrfs_device *dev;
+
+			BUG_ON(stripe_index >= bbio->num_stripes);
+			dev = bbio->stripes[stripe_index].dev;
+			if (dev->bdev) {
+				if (bio->bi_rw & WRITE)
+					btrfs_dev_stat_inc(dev,
+						BTRFS_DEV_STAT_WRITE_ERRS);
+				else
+					btrfs_dev_stat_inc(dev,
+						BTRFS_DEV_STAT_READ_ERRS);
+				if ((bio->bi_rw & WRITE_FLUSH) == WRITE_FLUSH)
+					btrfs_dev_stat_inc(dev,
+						BTRFS_DEV_STAT_FLUSH_ERRS);
+				btrfs_dev_stat_print_on_error(dev);
+			}
+		}
+	}
 
 	if (bio == bbio->orig_bio)
 		is_orig_bio = 1;
@@ -4146,14 +4233,23 @@ int btrfs_map_bio(struct btrfs_root *root, int rw, struct bio *bio,
 			bio = first_bio;
 		}
 		bio->bi_private = bbio;
+		bio->bi_private = merge_stripe_index_into_bio_private(
+				bio->bi_private, (unsigned int)dev_nr);
 		bio->bi_end_io = btrfs_end_bio;
 		bio->bi_sector = bbio->stripes[dev_nr].physical >> 9;
 		dev = bbio->stripes[dev_nr].dev;
 		if (dev && dev->bdev && (rw != WRITE || dev->writeable)) {
+#ifdef DEBUG
+			struct rcu_string *name;
+
+			rcu_read_lock();
+			name = rcu_dereference(dev->name);
 			pr_debug("btrfs_map_bio: rw %d, secor=%llu, dev=%lu "
 				 "(%s id %llu), size=%u\n", rw,
 				 (u64)bio->bi_sector, (u_long)dev->bdev->bd_dev,
-				 dev->name, dev->devid, bio->bi_size);
+				 name->str, dev->devid, bio->bi_size);
+			rcu_read_unlock();
+#endif
 			bio->bi_bdev = dev->bdev;
 			if (async_submit)
 				schedule_bio(root, dev, rw, bio);
@@ -4350,8 +4446,10 @@ static int open_seed_devices(struct btrfs_root *root, u8 *fsid)
 
 	ret = __btrfs_open_devices(fs_devices, FMODE_READ,
 				   root->fs_info->bdev_holder);
-	if (ret)
+	if (ret) {
+		free_fs_devices(fs_devices);
 		goto out;
+	}
 
 	if (!fs_devices->seeding) {
 		__btrfs_close_devices(fs_devices);
@@ -4504,6 +4602,28 @@ int btrfs_read_sys_array(struct btrfs_root *root)
 	return ret;
 }
 
+struct btrfs_device *btrfs_find_device_for_logical(struct btrfs_root *root,
+						   u64 logical, int mirror_num)
+{
+	struct btrfs_mapping_tree *map_tree = &root->fs_info->mapping_tree;
+	int ret;
+	u64 map_length = 0;
+	struct btrfs_bio *bbio = NULL;
+	struct btrfs_device *device;
+
+	BUG_ON(mirror_num == 0);
+	ret = btrfs_map_block(map_tree, WRITE, logical, &map_length, &bbio,
+			      mirror_num);
+	if (ret) {
+		BUG_ON(bbio != NULL);
+		return NULL;
+	}
+	BUG_ON(mirror_num != bbio->mirror_num);
+	device = bbio->stripes[mirror_num - 1].dev;
+	kfree(bbio);
+	return device;
+}
+
 int btrfs_read_chunk_tree(struct btrfs_root *root)
 {
 	struct btrfs_path *path;
@@ -4578,3 +4698,231 @@ error:
 	btrfs_free_path(path);
 	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_in_rcu(KERN_WARNING "btrfs: no dev_stats entry found for device %s (devid %llu) (OK on first mount after mkfs)\n",
+				      rcu_str_deref(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_in_rcu(KERN_WARNING "btrfs: error %d while searching for dev_stats item for device %s!\n",
+			      ret, rcu_str_deref(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_in_rcu(KERN_WARNING "btrfs: delete too small dev_stats item for device %s failed %d!\n",
+				      rcu_str_deref(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_in_rcu(KERN_WARNING "btrfs: insert dev_stats item for device %s failed %d!\n",
+				      rcu_str_deref(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);
+	btrfs_dev_stat_print_on_error(dev);
+}
+
+void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
+{
+	if (!dev->dev_stats_valid)
+		return;
+	printk_ratelimited_in_rcu(KERN_ERR
+			   "btrfs: bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
+			   rcu_str_deref(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));
+}
+
+static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
+{
+	printk_in_rcu(KERN_INFO "btrfs: bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u\n",
+	       rcu_str_deref(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)
+{
+	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 (!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)
+				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;
+}