fs/btrfs/volumes.c

/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */
#include <linux/sched.h>
#include <linux/bio.h>
#include <linux/slab.h>
#include <linux/buffer_head.h>
#include <linux/blkdev.h>
#include <linux/random.h>
#include <linux/iocontext.h>
#include <linux/capability.h>
#include <linux/kthread.h>
#include <asm/div64.h>
#include "compat.h"
#include "ctree.h"
#include "extent_map.h"
#include "disk-io.h"
#include "transaction.h"
#include "print-tree.h"
#include "volumes.h"
#include "async-thread.h"
#include "check-integrity.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 DEFINE_MUTEX(uuid_mutex);
static LIST_HEAD(fs_uuids);

static void lock_chunks(struct btrfs_root *root)
{
	mutex_lock(&root->fs_info->chunk_mutex);
}

static void unlock_chunks(struct btrfs_root *root)
{
	mutex_unlock(&root->fs_info->chunk_mutex);
}

static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
{
	struct btrfs_device *device;
	WARN_ON(fs_devices->opened);
	while (!list_empty(&fs_devices->devices)) {
		device = list_entry(fs_devices->devices.next,
				    struct btrfs_device, dev_list);
		list_del(&device->dev_list);
		kfree(device->name);
		kfree(device);
	}
	kfree(fs_devices);
}

int btrfs_cleanup_fs_uuids(void)
{
	struct btrfs_fs_devices *fs_devices;

	while (!list_empty(&fs_uuids)) {
		fs_devices = list_entry(fs_uuids.next,
					struct btrfs_fs_devices, list);
		list_del(&fs_devices->list);
		free_fs_devices(fs_devices);
	}
	return 0;
}

static noinline struct btrfs_device *__find_device(struct list_head *head,
						   u64 devid, u8 *uuid)
{
	struct btrfs_device *dev;

	list_for_each_entry(dev, head, dev_list) {
		if (dev->devid == devid &&
		    (!uuid || !memcmp(dev->uuid, uuid, BTRFS_UUID_SIZE))) {
			return dev;
		}
	}
	return NULL;
}

static noinline struct btrfs_fs_devices *find_fsid(u8 *fsid)
{
	struct btrfs_fs_devices *fs_devices;

	list_for_each_entry(fs_devices, &fs_uuids, list) {
		if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0)
			return fs_devices;
	}
	return NULL;
}

static void requeue_list(struct btrfs_pending_bios *pending_bios,
			struct bio *head, struct bio *tail)
{

	struct bio *old_head;

	old_head = pending_bios->head;
	pending_bios->head = head;
	if (pending_bios->tail)
		tail->bi_next = old_head;
	else
		pending_bios->tail = tail;
}

/*
 * we try to collect pending bios for a device so we don't get a large
 * number of procs sending bios down to the same device.  This greatly
 * improves the schedulers ability to collect and merge the bios.
 *
 * But, it also turns into a long list of bios to process and that is sure
 * to eventually make the worker thread block.  The solution here is to
 * make some progress and then put this work struct back at the end of
 * the list if the block device is congested.  This way, multiple devices
 * can make progress from a single worker thread.
 */
static noinline int run_scheduled_bios(struct btrfs_device *device)
{
	struct bio *pending;
	struct backing_dev_info *bdi;
	struct btrfs_fs_info *fs_info;
	struct btrfs_pending_bios *pending_bios;
	struct bio *tail;
	struct bio *cur;
	int again = 0;
	unsigned long num_run;
	unsigned long batch_run = 0;
	unsigned long limit;
	unsigned long last_waited = 0;
	int force_reg = 0;
	int sync_pending = 0;
	struct blk_plug plug;

	/*
	 * this function runs all the bios we've collected for
	 * a particular device.  We don't want to wander off to
	 * another device without first sending all of these down.
	 * So, setup a plug here and finish it off before we return
	 */
	blk_start_plug(&plug);

	bdi = blk_get_backing_dev_info(device->bdev);
	fs_info = device->dev_root->fs_info;
	limit = btrfs_async_submit_limit(fs_info);
	limit = limit * 2 / 3;

loop:
	spin_lock(&device->io_lock);

loop_lock:
	num_run = 0;

	/* take all the bios off the list at once and process them
	 * later on (without the lock held).  But, remember the
	 * tail and other pointers so the bios can be properly reinserted
	 * into the list if we hit congestion
	 */
	if (!force_reg && device->pending_sync_bios.head) {
		pending_bios = &device->pending_sync_bios;
		force_reg = 1;
	} else {
		pending_bios = &device->pending_bios;
		force_reg = 0;
	}

	pending = pending_bios->head;
	tail = pending_bios->tail;
	WARN_ON(pending && !tail);

	/*
	 * if pending was null this time around, no bios need processing
	 * at all and we can stop.  Otherwise it'll loop back up again
	 * and do an additional check so no bios are missed.
	 *
	 * device->running_pending is used to synchronize with the
	 * schedule_bio code.
	 */
	if (device->pending_sync_bios.head == NULL &&
	    device->pending_bios.head == NULL) {
		again = 0;
		device->running_pending = 0;
	} else {
		again = 1;
		device->running_pending = 1;
	}

	pending_bios->head = NULL;
	pending_bios->tail = NULL;

	spin_unlock(&device->io_lock);

	while (pending) {

		rmb();
		/* we want to work on both lists, but do more bios on the
		 * sync list than the regular list
		 */
		if ((num_run > 32 &&
		    pending_bios != &device->pending_sync_bios &&
		    device->pending_sync_bios.head) ||
		   (num_run > 64 && pending_bios == &device->pending_sync_bios &&
		    device->pending_bios.head)) {
			spin_lock(&device->io_lock);
			requeue_list(pending_bios, pending, tail);
			goto loop_lock;
		}

		cur = pending;
		pending = pending->bi_next;
		cur->bi_next = NULL;
		atomic_dec(&fs_info->nr_async_bios);

		if (atomic_read(&fs_info->nr_async_bios) < limit &&
		    waitqueue_active(&fs_info->async_submit_wait))
			wake_up(&fs_info->async_submit_wait);

		BUG_ON(atomic_read(&cur->bi_cnt) == 0);

		/*
		 * if we're doing the sync list, record that our
		 * plug has some sync requests on it
		 *
		 * If we're doing the regular list and there are
		 * sync requests sitting around, unplug before
		 * we add more
		 */
		if (pending_bios == &device->pending_sync_bios) {
			sync_pending = 1;
		} else if (sync_pending) {
			blk_finish_plug(&plug);
			blk_start_plug(&plug);
			sync_pending = 0;
		}

		btrfsic_submit_bio(cur->bi_rw, cur);
		num_run++;
		batch_run++;
		if (need_resched())
			cond_resched();

		/*
		 * we made progress, there is more work to do and the bdi
		 * is now congested.  Back off and let other work structs
		 * run instead
		 */
		if (pending && bdi_write_congested(bdi) && batch_run > 8 &&
		    fs_info->fs_devices->open_devices > 1) {
			struct io_context *ioc;

			ioc = current->io_context;

			/*
			 * the main goal here is that we don't want to
			 * block if we're going to be able to submit
			 * more requests without blocking.
			 *
			 * This code does two great things, it pokes into
			 * the elevator code from a filesystem _and_
			 * it makes assumptions about how batching works.
			 */
			if (ioc && ioc->nr_batch_requests > 0 &&
			    time_before(jiffies, ioc->last_waited + HZ/50UL) &&
			    (last_waited == 0 ||
			     ioc->last_waited == last_waited)) {
				/*
				 * we want to go through our batch of
				 * requests and stop.  So, we copy out
				 * the ioc->last_waited time and test
				 * against it before looping
				 */
				last_waited = ioc->last_waited;
				if (need_resched())
					cond_resched();
				continue;
			}
			spin_lock(&device->io_lock);
			requeue_list(pending_bios, pending, tail);
			device->running_pending = 1;

			spin_unlock(&device->io_lock);
			btrfs_requeue_work(&device->work);
			goto done;
		}
		/* unplug every 64 requests just for good measure */
		if (batch_run % 64 == 0) {
			blk_finish_plug(&plug);
			blk_start_plug(&plug);
			sync_pending = 0;
		}
	}

	cond_resched();
	if (again)
		goto loop;

	spin_lock(&device->io_lock);
	if (device->pending_bios.head || device->pending_sync_bios.head)
		goto loop_lock;
	spin_unlock(&device->io_lock);

done:
	blk_finish_plug(&plug);
	return 0;
}

static void pending_bios_fn(struct btrfs_work *work)
{
	struct btrfs_device *device;

	device = container_of(work, struct btrfs_device, work);
	run_scheduled_bios(device);
}

static noinline int device_list_add(const char *path,
			   struct btrfs_super_block *disk_super,
			   u64 devid, struct btrfs_fs_devices **fs_devices_ret)
{
	struct btrfs_device *device;
	struct btrfs_fs_devices *fs_devices;
	u64 found_transid = btrfs_super_generation(disk_super);
	char *name;

	fs_devices = find_fsid(disk_super->fsid);
	if (!fs_devices) {
		fs_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
		if (!fs_devices)
			return -ENOMEM;
		INIT_LIST_HEAD(&fs_devices->devices);
		INIT_LIST_HEAD(&fs_devices->alloc_list);
		list_add(&fs_devices->list, &fs_uuids);
		memcpy(fs_devices->fsid, disk_super->fsid, BTRFS_FSID_SIZE);
		fs_devices->latest_devid = devid;
		fs_devices->latest_trans = found_transid;
		mutex_init(&fs_devices->device_list_mutex);
		device = NULL;
	} else {
		device = __find_device(&fs_devices->devices, devid,
				       disk_super->dev_item.uuid);
	}
	if (!device) {
		if (fs_devices->opened)
			return -EBUSY;

		device = kzalloc(sizeof(*device), GFP_NOFS);
		if (!device) {
			/* we can safely leave the fs_devices entry around */
			return -ENOMEM;
		}
		device->devid = devid;
		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) {
			kfree(device);
			return -ENOMEM;
		}
		INIT_LIST_HEAD(&device->dev_alloc_list);

		/* init readahead state */
		spin_lock_init(&device->reada_lock);
		device->reada_curr_zone = NULL;
		atomic_set(&device->reada_in_flight, 0);
		device->reada_next = 0;
		INIT_RADIX_TREE(&device->reada_zones, GFP_NOFS & ~__GFP_WAIT);
		INIT_RADIX_TREE(&device->reada_extents, GFP_NOFS & ~__GFP_WAIT);

		mutex_lock(&fs_devices->device_list_mutex);
		list_add_rcu(&device->dev_list, &fs_devices->devices);
		mutex_unlock(&fs_devices->device_list_mutex);

		device->fs_devices = fs_devices;
		fs_devices->num_devices++;
	} else if (!device->name || strcmp(device->name, path)) {
		name = kstrdup(path, GFP_NOFS);
		if (!name)
			return -ENOMEM;
		kfree(device->name);
		device->name = name;
		if (device->missing) {
			fs_devices->missing_devices--;
			device->missing = 0;
		}
	}

	if (found_transid > fs_devices->latest_trans) {
		fs_devices->latest_devid = devid;
		fs_devices->latest_trans = found_transid;
	}
	*fs_devices_ret = fs_devices;
	return 0;
}

static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
{
	struct btrfs_fs_devices *fs_devices;
	struct btrfs_device *device;
	struct btrfs_device *orig_dev;

	fs_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
	if (!fs_devices)
		return ERR_PTR(-ENOMEM);

	INIT_LIST_HEAD(&fs_devices->devices);
	INIT_LIST_HEAD(&fs_devices->alloc_list);
	INIT_LIST_HEAD(&fs_devices->list);
	mutex_init(&fs_devices->device_list_mutex);
	fs_devices->latest_devid = orig->latest_devid;
	fs_devices->latest_trans = orig->latest_trans;
	memcpy(fs_devices->fsid, orig->fsid, sizeof(fs_devices->fsid));

	/* We have held the volume lock, it is safe to get the devices. */
	list_for_each_entry(orig_dev, &orig->devices, dev_list) {
		device = kzalloc(sizeof(*device), GFP_NOFS);
		if (!device)
			goto error;

		device->name = kstrdup(orig_dev->name, GFP_NOFS);
		if (!device->name) {
			kfree(device);
			goto error;
		}

		device->devid = orig_dev->devid;
		device->work.func = pending_bios_fn;
		memcpy(device->uuid, orig_dev->uuid, sizeof(device->uuid));
		spin_lock_init(&device->io_lock);
		INIT_LIST_HEAD(&device->dev_list);
		INIT_LIST_HEAD(&device->dev_alloc_list);

		list_add(&device->dev_list, &fs_devices->devices);
		device->fs_devices = fs_devices;
		fs_devices->num_devices++;
	}
	return fs_devices;
error:
	free_fs_devices(fs_devices);
	return ERR_PTR(-ENOMEM);
}

int btrfs_close_extra_devices(struct btrfs_fs_devices *fs_devices)
{
	struct btrfs_device *device, *next;

	struct block_device *latest_bdev = NULL;
	u64 latest_devid = 0;
	u64 latest_transid = 0;

	mutex_lock(&uuid_mutex);
again:
	/* This is the initialized path, it is safe to release the devices. */
	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
		if (device->in_fs_metadata) {
			if (!latest_transid ||
			    device->generation > latest_transid) {
				latest_devid = device->devid;
				latest_transid = device->generation;
				latest_bdev = device->bdev;
			}
			continue;
		}

		if (device->bdev) {
			blkdev_put(device->bdev, device->mode);
			device->bdev = NULL;
			fs_devices->open_devices--;
		}
		if (device->writeable) {
			list_del_init(&device->dev_alloc_list);
			device->writeable = 0;
			fs_devices->rw_devices--;
		}
		list_del_init(&device->dev_list);
		fs_devices->num_devices--;
		kfree(device->name);
		kfree(device);
	}

	if (fs_devices->seed) {
		fs_devices = fs_devices->seed;
		goto again;
	}

	fs_devices->latest_bdev = latest_bdev;
	fs_devices->latest_devid = latest_devid;
	fs_devices->latest_trans = latest_transid;

	mutex_unlock(&uuid_mutex);
	return 0;
}

static void __free_device(struct work_struct *work)
{
	struct btrfs_device *device;

	device = container_of(work, struct btrfs_device, rcu_work);

	if (device->bdev)
		blkdev_put(device->bdev, device->mode);

	kfree(device->name);
	kfree(device);
}

static void free_device(struct rcu_head *head)
{
	struct btrfs_device *device;

	device = container_of(head, struct btrfs_device, rcu);

	INIT_WORK(&device->rcu_work, __free_device);
	schedule_work(&device->rcu_work);
}

static int __btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
	struct btrfs_device *device;

	if (--fs_devices->opened > 0)
		return 0;

	mutex_lock(&fs_devices->device_list_mutex);
	list_for_each_entry(device, &fs_devices->devices, dev_list) {
		struct btrfs_device *new_device;

		if (device->bdev)
			fs_devices->open_devices--;

		if (device->writeable) {
			list_del_init(&device->dev_alloc_list);
			fs_devices->rw_devices--;
		}

		if (device->can_discard)
			fs_devices->num_can_discard--;

		new_device = kmalloc(sizeof(*new_device), GFP_NOFS);
		BUG_ON(!new_device);
		memcpy(new_device, device, sizeof(*new_device));
		new_device->name = kstrdup(device->name, GFP_NOFS);
		BUG_ON(device->name && !new_device->name);
		new_device->bdev = NULL;
		new_device->writeable = 0;
		new_device->in_fs_metadata = 0;
		new_device->can_discard = 0;
		list_replace_rcu(&device->dev_list, &new_device->dev_list);

		call_rcu(&device->rcu, free_device);
	}
	mutex_unlock(&fs_devices->device_list_mutex);

	WARN_ON(fs_devices->open_devices);
	WARN_ON(fs_devices->rw_devices);
	fs_devices->opened = 0;
	fs_devices->seeding = 0;

	return 0;
}

int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
	struct btrfs_fs_devices *seed_devices = NULL;
	int ret;

	mutex_lock(&uuid_mutex);
	ret = __btrfs_close_devices(fs_devices);
	if (!fs_devices->opened) {
		seed_devices = fs_devices->seed;
		fs_devices->seed = NULL;
	}
	mutex_unlock(&uuid_mutex);

	while (seed_devices) {
		fs_devices = seed_devices;
		seed_devices = fs_devices->seed;
		__btrfs_close_devices(fs_devices);
		free_fs_devices(fs_devices);
	}
	return ret;
}

static int __btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
				fmode_t flags, void *holder)
{
	struct request_queue *q;
	struct block_device *bdev;
	struct list_head *head = &fs_devices->devices;
	struct btrfs_device *device;
	struct block_device *latest_bdev = NULL;
	struct buffer_head *bh;
	struct btrfs_super_block *disk_super;
	u64 latest_devid = 0;
	u64 latest_transid = 0;
	u64 devid;
	int seeding = 1;
	int ret = 0;

	flags |= FMODE_EXCL;

	list_for_each_entry(device, head, dev_list) {
		if (device->bdev)
			continue;
		if (!device->name)
			continue;

		bdev = blkdev_get_by_path(device->name, flags, holder);
		if (IS_ERR(bdev)) {
			printk(KERN_INFO "open %s failed\n", device->name);
			goto error;
		}
		set_blocksize(bdev, 4096);

		bh = btrfs_read_dev_super(bdev);
		if (!bh)
			goto error_close;

		disk_super = (struct btrfs_super_block *)bh->b_data;
		devid = btrfs_stack_device_id(&disk_super->dev_item);
		if (devid != device->devid)
			goto error_brelse;

		if (memcmp(device->uuid, disk_super->dev_item.uuid,
			   BTRFS_UUID_SIZE))
			goto error_brelse;

		device->generation = btrfs_super_generation(disk_super);
		if (!latest_transid || device->generation > latest_transid) {
			latest_devid = devid;
			latest_transid = device->generation;
			latest_bdev = bdev;
		}

		if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
			device->writeable = 0;
		} else {
			device->writeable = !bdev_read_only(bdev);
			seeding = 0;
		}

		q = bdev_get_queue(bdev);
		if (blk_queue_discard(q)) {
			device->can_discard = 1;
			fs_devices->num_can_discard++;
		}

		device->bdev = bdev;
		device->in_fs_metadata = 0;
		device->mode = flags;

		if (!blk_queue_nonrot(bdev_get_queue(bdev)))
			fs_devices->rotating = 1;

		fs_devices->open_devices++;
		if (device->writeable) {
			fs_devices->rw_devices++;
			list_add(&device->dev_alloc_list,
				 &fs_devices->alloc_list);
		}
		brelse(bh);
		continue;

error_brelse:
		brelse(bh);
error_close:
		blkdev_put(bdev, flags);
error:
		continue;
	}
	if (fs_devices->open_devices == 0) {
		ret = -EINVAL;
		goto out;
	}
	fs_devices->seeding = seeding;
	fs_devices->opened = 1;
	fs_devices->latest_bdev = latest_bdev;
	fs_devices->latest_devid = latest_devid;
	fs_devices->latest_trans = latest_transid;
	fs_devices->total_rw_bytes = 0;
out:
	return ret;
}

int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
		       fmode_t flags, void *holder)
{
	int ret;

	mutex_lock(&uuid_mutex);
	if (fs_devices->opened) {
		fs_devices->opened++;
		ret = 0;
	} else {
		ret = __btrfs_open_devices(fs_devices, flags, holder);
	}
	mutex_unlock(&uuid_mutex);
	return ret;
}

int btrfs_scan_one_device(const char *path, fmode_t flags, void *holder,
			  struct btrfs_fs_devices **fs_devices_ret)
{
	struct btrfs_super_block *disk_super;
	struct block_device *bdev;
	struct buffer_head *bh;
	int ret;
	u64 devid;
	u64 transid;

	flags |= FMODE_EXCL;
	bdev = blkdev_get_by_path(path, flags, holder);

	if (IS_ERR(bdev)) {
		ret = PTR_ERR(bdev);
		goto error;
	}

	mutex_lock(&uuid_mutex);
	ret = set_blocksize(bdev, 4096);
	if (ret)
		goto error_close;
	bh = btrfs_read_dev_super(bdev);
	if (!bh) {
		ret = -EINVAL;
		goto error_close;
	}
	disk_super = (struct btrfs_super_block *)bh->b_data;
	devid = btrfs_stack_device_id(&disk_super->dev_item);
	transid = btrfs_super_generation(disk_super);
	if (disk_super->label[0])
		printk(KERN_INFO "device label %s ", disk_super->label);
	else
		printk(KERN_INFO "device fsid %pU ", disk_super->fsid);
	printk(KERN_CONT "devid %llu transid %llu %s\n",
	       (unsigned long long)devid, (unsigned long long)transid, path);
	ret = device_list_add(path, disk_super, devid, fs_devices_ret);

	brelse(bh);
error_close:
	mutex_unlock(&uuid_mutex);
	blkdev_put(bdev, flags);
error:
	return ret;
}

/* helper to account the used device space in the range */
int btrfs_account_dev_extents_size(struct btrfs_device *device, u64 start,
				   u64 end, u64 *length)
{
	struct btrfs_key key;
	struct btrfs_root *root = device->dev_root;
	struct btrfs_dev_extent *dev_extent;
	struct btrfs_path *path;
	u64 extent_end;
	int ret;
	int slot;
	struct extent_buffer *l;

	*length = 0;

	if (start >= device->total_bytes)
		return 0;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;
	path->reada = 2;

	key.objectid = device->devid;
	key.offset = start;
	key.type = BTRFS_DEV_EXTENT_KEY;

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
		goto out;
	if (ret > 0) {
		ret = btrfs_previous_item(root, path, key.objectid, key.type);
		if (ret < 0)
			goto out;
	}

	while (1) {
		l = path->nodes[0];
		slot = path->slots[0];
		if (slot >= btrfs_header_nritems(l)) {
			ret = btrfs_next_leaf(root, path);
			if (ret == 0)
				continue;
			if (ret < 0)
				goto out;

			break;
		}
		btrfs_item_key_to_cpu(l, &key, slot);

		if (key.objectid < device->devid)
			goto next;

		if (key.objectid > device->devid)
			break;

		if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY)
			goto next;

		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
		extent_end = key.offset + btrfs_dev_extent_length(l,
								  dev_extent);
		if (key.offset <= start && extent_end > end) {
			*length = end - start + 1;
			break;
		} else if (key.offset <= start && extent_end > start)
			*length += extent_end - start;
		else if (key.offset > start && extent_end <= end)
			*length += extent_end - key.offset;
		else if (key.offset > start && key.offset <= end) {
			*length += end - key.offset + 1;
			break;
		} else if (key.offset > end)
			break;

next:
		path->slots[0]++;
	}
	ret = 0;
out:
	btrfs_free_path(path);
	return ret;
}

/*
 * find_free_dev_extent - find free space in the specified device
 * @device:	the device which we search the free space in
 * @num_bytes:	the size of the free space that we need
 * @start:	store the start of the free space.
 * @len:	the size of the free space. that we find, or the size of the max
 * 		free space if we don't find suitable free space
 *
 * this uses a pretty simple search, the expectation is that it is
 * called very infrequently and that a given device has a small number
 * of extents
 *
 * @start is used to store the start of the free space if we find. But if we
 * don't find suitable free space, it will be used to store the start position
 * of the max free space.
 *
 * @len is used to store the size of the free space that we find.
 * But if we don't find suitable free space, it is used to store the size of
 * the max free space.
 */
int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
			 u64 *start, u64 *len)
{
	struct btrfs_key key;
	struct btrfs_root *root = device->dev_root;
	struct btrfs_dev_extent *dev_extent;
	struct btrfs_path *path;
	u64 hole_size;
	u64 max_hole_start;
	u64 max_hole_size;
	u64 extent_end;
	u64 search_start;
	u64 search_end = device->total_bytes;
	int ret;
	int slot;
	struct extent_buffer *l;

	/* FIXME use last free of some kind */

	/* we don't want to overwrite the superblock on the drive,
	 * so we make sure to start at an offset of at least 1MB
	 */
	search_start = max(root->fs_info->alloc_start, 1024ull * 1024);

	max_hole_start = search_start;
	max_hole_size = 0;
	hole_size = 0;

	if (search_start >= search_end) {
		ret = -ENOSPC;
		goto error;
	}

	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto error;
	}
	path->reada = 2;

	key.objectid = device->devid;
	key.offset = search_start;
	key.type = BTRFS_DEV_EXTENT_KEY;

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
		goto out;
	if (ret > 0) {
		ret = btrfs_previous_item(root, path, key.objectid, key.type);
		if (ret < 0)
			goto out;
	}

	while (1) {
		l = path->nodes[0];
		slot = path->slots[0];
		if (slot >= btrfs_header_nritems(l)) {
			ret = btrfs_next_leaf(root, path);
			if (ret == 0)
				continue;
			if (ret < 0)
				goto out;

			break;
		}
		btrfs_item_key_to_cpu(l, &key, slot);

		if (key.objectid < device->devid)
			goto next;

		if (key.objectid > device->devid)
			break;

		if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY)
			goto next;

		if (key.offset > search_start) {
			hole_size = key.offset - search_start;

			if (hole_size > max_hole_size) {
				max_hole_start = search_start;
				max_hole_size = hole_size;
			}

			/*
			 * If this free space is greater than which we need,
			 * it must be the max free space that we have found
			 * until now, so max_hole_start must point to the start
			 * of this free space and the length of this free space
			 * is stored in max_hole_size. Thus, we return
			 * max_hole_start and max_hole_size and go back to the
			 * caller.
			 */
			if (hole_size >= num_bytes) {
				ret = 0;
				goto out;
			}
		}

		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
		extent_end = key.offset + btrfs_dev_extent_length(l,
								  dev_extent);
		if (extent_end > search_start)
			search_start = extent_end;
next:
		path->slots[0]++;
		cond_resched();
	}

	/*
	 * At this point, search_start should be the end of
	 * allocated dev extents, and when shrinking the device,
	 * search_end may be smaller than search_start.
	 */
	if (search_end > search_start)
		hole_size = search_end - search_start;

	if (hole_size > max_hole_size) {
		max_hole_start = search_start;
		max_hole_size = hole_size;
	}

	/* See above. */
	if (hole_size < num_bytes)
		ret = -ENOSPC;
	else
		ret = 0;

out:
	btrfs_free_path(path);
error:
	*start = max_hole_start;
	if (len)
		*len = max_hole_size;
	return ret;
}

static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
			  struct btrfs_device *device,
			  u64 start)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_root *root = device->dev_root;
	struct btrfs_key key;
	struct btrfs_key found_key;
	struct extent_buffer *leaf = NULL;
	struct btrfs_dev_extent *extent = NULL;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = device->devid;
	key.offset = start;
	key.type = BTRFS_DEV_EXTENT_KEY;
again:
	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0) {
		ret = btrfs_previous_item(root, path, key.objectid,
					  BTRFS_DEV_EXTENT_KEY);
		if (ret)
			goto out;
		leaf = path->nodes[0];
		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
		extent = btrfs_item_ptr(leaf, path->slots[0],
					struct btrfs_dev_extent);
		BUG_ON(found_key.offset > start || found_key.offset +
		       btrfs_dev_extent_length(leaf, extent) < start);
		key = found_key;
		btrfs_release_path(path);
		goto again;
	} else if (ret == 0) {
		leaf = path->nodes[0];
		extent = btrfs_item_ptr(leaf, path->slots[0],
					struct btrfs_dev_extent);
	}
	BUG_ON(ret);

	if (device->bytes_used > 0) {
		u64 len = btrfs_dev_extent_length(leaf, extent);
		device->bytes_used -= len;
		spin_lock(&root->fs_info->free_chunk_lock);
		root->fs_info->free_chunk_space += len;
		spin_unlock(&root->fs_info->free_chunk_lock);
	}
	ret = btrfs_del_item(trans, root, path);

out:
	btrfs_free_path(path);
	return ret;
}

int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
			   struct btrfs_device *device,
			   u64 chunk_tree, u64 chunk_objectid,
			   u64 chunk_offset, u64 start, u64 num_bytes)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_root *root = device->dev_root;
	struct btrfs_dev_extent *extent;
	struct extent_buffer *leaf;
	struct btrfs_key key;

	WARN_ON(!device->in_fs_metadata);
	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = device->devid;
	key.offset = start;
	key.type = BTRFS_DEV_EXTENT_KEY;
	ret = btrfs_insert_empty_item(trans, root, path, &key,
				      sizeof(*extent));
	BUG_ON(ret);

	leaf = path->nodes[0];
	extent = btrfs_item_ptr(leaf, path->slots[0],
				struct btrfs_dev_extent);
	btrfs_set_dev_extent_chunk_tree(leaf, extent, chunk_tree);
	btrfs_set_dev_extent_chunk_objectid(leaf, extent, chunk_objectid);
	btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset);

	write_extent_buffer(leaf, root->fs_info->chunk_tree_uuid,
		    (unsigned long)btrfs_dev_extent_chunk_tree_uuid(extent),
		    BTRFS_UUID_SIZE);

	btrfs_set_dev_extent_length(leaf, extent, num_bytes);
	btrfs_mark_buffer_dirty(leaf);
	btrfs_free_path(path);
	return ret;
}

static noinline int find_next_chunk(struct btrfs_root *root,
				    u64 objectid, u64 *offset)
{
	struct btrfs_path *path;
	int ret;
	struct btrfs_key key;
	struct btrfs_chunk *chunk;
	struct btrfs_key found_key;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = objectid;
	key.offset = (u64)-1;
	key.type = BTRFS_CHUNK_ITEM_KEY;

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
		goto error;

	BUG_ON(ret == 0);

	ret = btrfs_previous_item(root, path, 0, BTRFS_CHUNK_ITEM_KEY);
	if (ret) {
		*offset = 0;
	} else {
		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
				      path->slots[0]);
		if (found_key.objectid != objectid)
			*offset = 0;
		else {
			chunk = btrfs_item_ptr(path->nodes[0], path->slots[0],
					       struct btrfs_chunk);
			*offset = found_key.offset +
				btrfs_chunk_length(path->nodes[0], chunk);
		}
	}
	ret = 0;
error:
	btrfs_free_path(path);
	return ret;
}

static noinline int find_next_devid(struct btrfs_root *root, u64 *objectid)
{
	int ret;
	struct btrfs_key key;
	struct btrfs_key found_key;
	struct btrfs_path *path;

	root = root->fs_info->chunk_root;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
	key.type = BTRFS_DEV_ITEM_KEY;
	key.offset = (u64)-1;

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
		goto error;

	BUG_ON(ret == 0);

	ret = btrfs_previous_item(root, path, BTRFS_DEV_ITEMS_OBJECTID,
				  BTRFS_DEV_ITEM_KEY);
	if (ret) {
		*objectid = 1;
	} else {
		btrfs_item_key_to_cpu(path->nodes[0], &found_key,
				      path->slots[0]);
		*objectid = found_key.offset + 1;
	}
	ret = 0;
error:
	btrfs_free_path(path);
	return ret;
}

/*
 * the device information is stored in the chunk root
 * the btrfs_device struct should be fully filled in
 */
int btrfs_add_device(struct btrfs_trans_handle *trans,
		     struct btrfs_root *root,
		     struct btrfs_device *device)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_dev_item *dev_item;
	struct extent_buffer *leaf;
	struct btrfs_key key;
	unsigned long ptr;

	root = root->fs_info->chunk_root;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
	key.type = BTRFS_DEV_ITEM_KEY;
	key.offset = device->devid;

	ret = btrfs_insert_empty_item(trans, root, path, &key,
				      sizeof(*dev_item));
	if (ret)
		goto out;

	leaf = path->nodes[0];
	dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);

	btrfs_set_device_id(leaf, dev_item, device->devid);
	btrfs_set_device_generation(leaf, dev_item, 0);
	btrfs_set_device_type(leaf, dev_item, device->type);
	btrfs_set_device_io_align(leaf, dev_item, device->io_align);
	btrfs_set_device_io_width(leaf, dev_item, device->io_width);
	btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
	btrfs_set_device_total_bytes(leaf, dev_item, device->total_bytes);
	btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
	btrfs_set_device_group(leaf, dev_item, 0);
	btrfs_set_device_seek_speed(leaf, dev_item, 0);
	btrfs_set_device_bandwidth(leaf, dev_item, 0);
	btrfs_set_device_start_offset(leaf, dev_item, 0);

	ptr = (unsigned long)btrfs_device_uuid(dev_item);
	write_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
	ptr = (unsigned long)btrfs_device_fsid(dev_item);
	write_extent_buffer(leaf, root->fs_info->fsid, ptr, BTRFS_UUID_SIZE);
	btrfs_mark_buffer_dirty(leaf);

	ret = 0;
out:
	btrfs_free_path(path);
	return ret;
}

static int btrfs_rm_dev_item(struct btrfs_root *root,
			     struct btrfs_device *device)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_key key;
	struct btrfs_trans_handle *trans;

	root = root->fs_info->chunk_root;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		btrfs_free_path(path);
		return PTR_ERR(trans);
	}
	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
	key.type = BTRFS_DEV_ITEM_KEY;
	key.offset = device->devid;
	lock_chunks(root);

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret < 0)
		goto out;

	if (ret > 0) {
		ret = -ENOENT;
		goto out;
	}

	ret = btrfs_del_item(trans, root, path);
	if (ret)
		goto out;
out:
	btrfs_free_path(path);
	unlock_chunks(root);
	btrfs_commit_transaction(trans, root);
	return ret;
}

int btrfs_rm_device(struct btrfs_root *root, char *device_path)
{
	struct btrfs_device *device;
	struct btrfs_device *next_device;
	struct block_device *bdev;
	struct buffer_head *bh = NULL;
	struct btrfs_super_block *disk_super;
	struct btrfs_fs_devices *cur_devices;
	u64 all_avail;
	u64 devid;
	u64 num_devices;
	u8 *dev_uuid;
	int ret = 0;
	bool clear_super = false;

	mutex_lock(&uuid_mutex);

	all_avail = root->fs_info->avail_data_alloc_bits |
		root->fs_info->avail_system_alloc_bits |
		root->fs_info->avail_metadata_alloc_bits;

	if ((all_avail & BTRFS_BLOCK_GROUP_RAID10) &&
	    root->fs_info->fs_devices->num_devices <= 4) {
		printk(KERN_ERR "btrfs: unable to go below four devices "
		       "on raid10\n");
		ret = -EINVAL;
		goto out;
	}

	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
	    root->fs_info->fs_devices->num_devices <= 2) {
		printk(KERN_ERR "btrfs: unable to go below two "
		       "devices on raid1\n");
		ret = -EINVAL;
		goto out;
	}

	if (strcmp(device_path, "missing") == 0) {
		struct list_head *devices;
		struct btrfs_device *tmp;

		device = NULL;
		devices = &root->fs_info->fs_devices->devices;
		/*
		 * It is safe to read the devices since the volume_mutex
		 * is held.
		 */
		list_for_each_entry(tmp, devices, dev_list) {
			if (tmp->in_fs_metadata && !tmp->bdev) {
				device = tmp;
				break;
			}
		}
		bdev = NULL;
		bh = NULL;
		disk_super = NULL;
		if (!device) {
			printk(KERN_ERR "btrfs: no missing devices found to "
			       "remove\n");
			goto out;
		}
	} else {
		bdev = blkdev_get_by_path(device_path, FMODE_READ | FMODE_EXCL,
					  root->fs_info->bdev_holder);
		if (IS_ERR(bdev)) {
			ret = PTR_ERR(bdev);
			goto out;
		}

		set_blocksize(bdev, 4096);
		bh = btrfs_read_dev_super(bdev);
		if (!bh) {
			ret = -EINVAL;
			goto error_close;
		}
		disk_super = (struct btrfs_super_block *)bh->b_data;
		devid = btrfs_stack_device_id(&disk_super->dev_item);
		dev_uuid = disk_super->dev_item.uuid;
		device = btrfs_find_device(root, devid, dev_uuid,
					   disk_super->fsid);
		if (!device) {
			ret = -ENOENT;
			goto error_brelse;
		}
	}

	if (device->writeable && root->fs_info->fs_devices->rw_devices == 1) {
		printk(KERN_ERR "btrfs: unable to remove the only writeable "
		       "device\n");
		ret = -EINVAL;
		goto error_brelse;
	}

	if (device->writeable) {
		lock_chunks(root);
		list_del_init(&device->dev_alloc_list);
		unlock_chunks(root);
		root->fs_info->fs_devices->rw_devices--;
		clear_super = true;
	}

	ret = btrfs_shrink_device(device, 0);
	if (ret)
		goto error_undo;

	ret = btrfs_rm_dev_item(root->fs_info->chunk_root, device);
	if (ret)
		goto error_undo;

	spin_lock(&root->fs_info->free_chunk_lock);
	root->fs_info->free_chunk_space = device->total_bytes -
		device->bytes_used;
	spin_unlock(&root->fs_info->free_chunk_lock);

	device->in_fs_metadata = 0;
	btrfs_scrub_cancel_dev(root, device);

	/*
	 * the device list mutex makes sure that we don't change
	 * the device list while someone else is writing out all
	 * the device supers.
	 */

	cur_devices = device->fs_devices;
	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
	list_del_rcu(&device->dev_list);

	device->fs_devices->num_devices--;

	if (device->missing)
		root->fs_info->fs_devices->missing_devices--;

	next_device = list_entry(root->fs_info->fs_devices->devices.next,
				 struct btrfs_device, dev_list);
	if (device->bdev == root->fs_info->sb->s_bdev)
		root->fs_info->sb->s_bdev = next_device->bdev;
	if (device->bdev == root->fs_info->fs_devices->latest_bdev)
		root->fs_info->fs_devices->latest_bdev = next_device->bdev;

	if (device->bdev)
		device->fs_devices->open_devices--;

	call_rcu(&device->rcu, free_device);
	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

	num_devices = btrfs_super_num_devices(root->fs_info->super_copy) - 1;
	btrfs_set_super_num_devices(root->fs_info->super_copy, num_devices);

	if (cur_devices->open_devices == 0) {
		struct btrfs_fs_devices *fs_devices;
		fs_devices = root->fs_info->fs_devices;
		while (fs_devices) {
			if (fs_devices->seed == cur_devices)
				break;
			fs_devices = fs_devices->seed;
		}
		fs_devices->seed = cur_devices->seed;
		cur_devices->seed = NULL;
		lock_chunks(root);
		__btrfs_close_devices(cur_devices);
		unlock_chunks(root);
		free_fs_devices(cur_devices);
	}

	/*
	 * at this point, the device is zero sized.  We want to
	 * remove it from the devices list and zero out the old super
	 */
	if (clear_super) {
		/* make sure this device isn't detected as part of
		 * the FS anymore
		 */
		memset(&disk_super->magic, 0, sizeof(disk_super->magic));
		set_buffer_dirty(bh);
		sync_dirty_buffer(bh);
	}

	ret = 0;

error_brelse:
	brelse(bh);
error_close:
	if (bdev)
		blkdev_put(bdev, FMODE_READ | FMODE_EXCL);
out:
	mutex_unlock(&uuid_mutex);
	return ret;
error_undo:
	if (device->writeable) {
		lock_chunks(root);
		list_add(&device->dev_alloc_list,
			 &root->fs_info->fs_devices->alloc_list);
		unlock_chunks(root);
		root->fs_info->fs_devices->rw_devices++;
	}
	goto error_brelse;
}

/*
 * does all the dirty work required for changing file system's UUID.
 */
static int btrfs_prepare_sprout(struct btrfs_root *root)
{
	struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
	struct btrfs_fs_devices *old_devices;
	struct btrfs_fs_devices *seed_devices;
	struct btrfs_super_block *disk_super = root->fs_info->super_copy;
	struct btrfs_device *device;
	u64 super_flags;

	BUG_ON(!mutex_is_locked(&uuid_mutex));
	if (!fs_devices->seeding)
		return -EINVAL;

	seed_devices = kzalloc(sizeof(*fs_devices), GFP_NOFS);
	if (!seed_devices)
		return -ENOMEM;

	old_devices = clone_fs_devices(fs_devices);
	if (IS_ERR(old_devices)) {
		kfree(seed_devices);
		return PTR_ERR(old_devices);
	}

	list_add(&old_devices->list, &fs_uuids);

	memcpy(seed_devices, fs_devices, sizeof(*seed_devices));
	seed_devices->opened = 1;
	INIT_LIST_HEAD(&seed_devices->devices);
	INIT_LIST_HEAD(&seed_devices->alloc_list);
	mutex_init(&seed_devices->device_list_mutex);

	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
	list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
			      synchronize_rcu);
	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

	list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
	list_for_each_entry(device, &seed_devices->devices, dev_list) {
		device->fs_devices = seed_devices;
	}

	fs_devices->seeding = 0;
	fs_devices->num_devices = 0;
	fs_devices->open_devices = 0;
	fs_devices->seed = seed_devices;

	generate_random_uuid(fs_devices->fsid);
	memcpy(root->fs_info->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
	memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
	super_flags = btrfs_super_flags(disk_super) &
		      ~BTRFS_SUPER_FLAG_SEEDING;
	btrfs_set_super_flags(disk_super, super_flags);

	return 0;
}

/*
 * strore the expected generation for seed devices in device items.
 */
static int btrfs_finish_sprout(struct btrfs_trans_handle *trans,
			       struct btrfs_root *root)
{
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_dev_item *dev_item;
	struct btrfs_device *device;
	struct btrfs_key key;
	u8 fs_uuid[BTRFS_UUID_SIZE];
	u8 dev_uuid[BTRFS_UUID_SIZE];
	u64 devid;
	int ret;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	root = root->fs_info->chunk_root;
	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
	key.offset = 0;
	key.type = BTRFS_DEV_ITEM_KEY;

	while (1) {
		ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
		if (ret < 0)
			goto error;

		leaf = path->nodes[0];
next_slot:
		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
			ret = btrfs_next_leaf(root, path);
			if (ret > 0)
				break;
			if (ret < 0)
				goto error;
			leaf = path->nodes[0];
			btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
			btrfs_release_path(path);
			continue;
		}

		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
		if (key.objectid != BTRFS_DEV_ITEMS_OBJECTID ||
		    key.type != BTRFS_DEV_ITEM_KEY)
			break;

		dev_item = btrfs_item_ptr(leaf, path->slots[0],
					  struct btrfs_dev_item);
		devid = btrfs_device_id(leaf, dev_item);
		read_extent_buffer(leaf, dev_uuid,
				   (unsigned long)btrfs_device_uuid(dev_item),
				   BTRFS_UUID_SIZE);
		read_extent_buffer(leaf, fs_uuid,
				   (unsigned long)btrfs_device_fsid(dev_item),
				   BTRFS_UUID_SIZE);
		device = btrfs_find_device(root, devid, dev_uuid, fs_uuid);
		BUG_ON(!device);

		if (device->fs_devices->seeding) {
			btrfs_set_device_generation(leaf, dev_item,
						    device->generation);
			btrfs_mark_buffer_dirty(leaf);
		}

		path->slots[0]++;
		goto next_slot;
	}
	ret = 0;
error:
	btrfs_free_path(path);
	return ret;
}

int btrfs_init_new_device(struct btrfs_root *root, char *device_path)
{
	struct request_queue *q;
	struct btrfs_trans_handle *trans;
	struct btrfs_device *device;
	struct block_device *bdev;
	struct list_head *devices;
	struct super_block *sb = root->fs_info->sb;
	u64 total_bytes;
	int seeding_dev = 0;
	int ret = 0;

	if ((sb->s_flags & MS_RDONLY) && !root->fs_info->fs_devices->seeding)
		return -EINVAL;

	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
				  root->fs_info->bdev_holder);
	if (IS_ERR(bdev))
		return PTR_ERR(bdev);

	if (root->fs_info->fs_devices->seeding) {
		seeding_dev = 1;
		down_write(&sb->s_umount);
		mutex_lock(&uuid_mutex);
	}

	filemap_write_and_wait(bdev->bd_inode->i_mapping);

	devices = &root->fs_info->fs_devices->devices;
	/*
	 * we have the volume lock, so we don't need the extra
	 * device list mutex while reading the list here.
	 */
	list_for_each_entry(device, devices, dev_list) {
		if (device->bdev == bdev) {
			ret = -EEXIST;
			goto error;
		}
	}

	device = kzalloc(sizeof(*device), GFP_NOFS);
	if (!device) {
		/* we can safely leave the fs_devices entry around */
		ret = -ENOMEM;
		goto error;
	}

	device->name = kstrdup(device_path, GFP_NOFS);
	if (!device->name) {
		kfree(device);
		ret = -ENOMEM;
		goto error;
	}

	ret = find_next_devid(root, &device->devid);
	if (ret) {
		kfree(device->name);
		kfree(device);
		goto error;
	}

	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		kfree(device->name);
		kfree(device);
		ret = PTR_ERR(trans);
		goto error;
	}

	lock_chunks(root);

	q = bdev_get_queue(bdev);
	if (blk_queue_discard(q))
		device->can_discard = 1;
	device->writeable = 1;
	device->work.func = pending_bios_fn;
	generate_random_uuid(device->uuid);
	spin_lock_init(&device->io_lock);
	device->generation = trans->transid;
	device->io_width = root->sectorsize;
	device->io_align = root->sectorsize;
	device->sector_size = root->sectorsize;
	device->total_bytes = i_size_read(bdev->bd_inode);
	device->disk_total_bytes = device->total_bytes;
	device->dev_root = root->fs_info->dev_root;
	device->bdev = bdev;
	device->in_fs_metadata = 1;
	device->mode = FMODE_EXCL;
	set_blocksize(device->bdev, 4096);

	if (seeding_dev) {
		sb->s_flags &= ~MS_RDONLY;
		ret = btrfs_prepare_sprout(root);
		BUG_ON(ret);
	}

	device->fs_devices = root->fs_info->fs_devices;

	/*
	 * we don't want write_supers to jump in here with our device
	 * half setup
	 */
	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
	list_add_rcu(&device->dev_list, &root->fs_info->fs_devices->devices);
	list_add(&device->dev_alloc_list,
		 &root->fs_info->fs_devices->alloc_list);
	root->fs_info->fs_devices->num_devices++;
	root->fs_info->fs_devices->open_devices++;
	root->fs_info->fs_devices->rw_devices++;
	if (device->can_discard)
		root->fs_info->fs_devices->num_can_discard++;
	root->fs_info->fs_devices->total_rw_bytes += device->total_bytes;

	spin_lock(&root->fs_info->free_chunk_lock);
	root->fs_info->free_chunk_space += device->total_bytes;
	spin_unlock(&root->fs_info->free_chunk_lock);

	if (!blk_queue_nonrot(bdev_get_queue(bdev)))
		root->fs_info->fs_devices->rotating = 1;

	total_bytes = btrfs_super_total_bytes(root->fs_info->super_copy);
	btrfs_set_super_total_bytes(root->fs_info->super_copy,
				    total_bytes + device->total_bytes);

	total_bytes = btrfs_super_num_devices(root->fs_info->super_copy);
	btrfs_set_super_num_devices(root->fs_info->super_copy,
				    total_bytes + 1);
	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);

	if (seeding_dev) {
		ret = init_first_rw_device(trans, root, device);
		BUG_ON(ret);
		ret = btrfs_finish_sprout(trans, root);
		BUG_ON(ret);
	} else {
		ret = btrfs_add_device(trans, root, device);
	}

	/*
	 * we've got more storage, clear any full flags on the space
	 * infos
	 */
	btrfs_clear_space_info_full(root->fs_info);

	unlock_chunks(root);
	btrfs_commit_transaction(trans, root);

	if (seeding_dev) {
		mutex_unlock(&uuid_mutex);
		up_write(&sb->s_umount);

		ret = btrfs_relocate_sys_chunks(root);
		BUG_ON(ret);
	}

	return ret;
error:
	blkdev_put(bdev, FMODE_EXCL);
	if (seeding_dev) {
		mutex_unlock(&uuid_mutex);
		up_write(&sb->s_umount);
	}
	return ret;
}

static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
					struct btrfs_device *device)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_root *root;
	struct btrfs_dev_item *dev_item;
	struct extent_buffer *leaf;
	struct btrfs_key key;

	root = device->dev_root->fs_info->chunk_root;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
	key.type = BTRFS_DEV_ITEM_KEY;
	key.offset = device->devid;

	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
	if (ret < 0)
		goto out;

	if (ret > 0) {
		ret = -ENOENT;
		goto out;
	}

	leaf = path->nodes[0];
	dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);

	btrfs_set_device_id(leaf, dev_item, device->devid);
	btrfs_set_device_type(leaf, dev_item, device->type);
	btrfs_set_device_io_align(leaf, dev_item, device->io_align);
	btrfs_set_device_io_width(leaf, dev_item, device->io_width);
	btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
	btrfs_set_device_total_bytes(leaf, dev_item, device->disk_total_bytes);
	btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used);
	btrfs_mark_buffer_dirty(leaf);

out:
	btrfs_free_path(path);
	return ret;
}

static int __btrfs_grow_device(struct btrfs_trans_handle *trans,
		      struct btrfs_device *device, u64 new_size)
{
	struct btrfs_super_block *super_copy =
		device->dev_root->fs_info->super_copy;
	u64 old_total = btrfs_super_total_bytes(super_copy);
	u64 diff = new_size - device->total_bytes;

	if (!device->writeable)
		return -EACCES;
	if (new_size <= device->total_bytes)
		return -EINVAL;

	btrfs_set_super_total_bytes(super_copy, old_total + diff);
	device->fs_devices->total_rw_bytes += diff;

	device->total_bytes = new_size;
	device->disk_total_bytes = new_size;
	btrfs_clear_space_info_full(device->dev_root->fs_info);

	return btrfs_update_device(trans, device);
}

int btrfs_grow_device(struct btrfs_trans_handle *trans,
		      struct btrfs_device *device, u64 new_size)
{
	int ret;
	lock_chunks(device->dev_root);
	ret = __btrfs_grow_device(trans, device, new_size);
	unlock_chunks(device->dev_root);
	return ret;
}

static int btrfs_free_chunk(struct btrfs_trans_handle *trans,
			    struct btrfs_root *root,
			    u64 chunk_tree, u64 chunk_objectid,
			    u64 chunk_offset)
{
	int ret;
	struct btrfs_path *path;
	struct btrfs_key key;

	root = root->fs_info->chunk_root;
	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	key.objectid = chunk_objectid;
	key.offset = chunk_offset;
	key.type = BTRFS_CHUNK_ITEM_KEY;

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	BUG_ON(ret);

	ret = btrfs_del_item(trans, root, path);

	btrfs_free_path(path);
	return ret;
}

static int btrfs_del_sys_chunk(struct btrfs_root *root, u64 chunk_objectid, u64
			chunk_offset)
{
	struct btrfs_super_block *super_copy = root->fs_info->super_copy;
	struct btrfs_disk_key *disk_key;
	struct btrfs_chunk *chunk;
	u8 *ptr;
	int ret = 0;
	u32 num_stripes;
	u32 array_size;
	u32 len = 0;
	u32 cur;
	struct btrfs_key key;

	array_size = btrfs_super_sys_array_size(super_copy);

	ptr = super_copy->sys_chunk_array;
	cur = 0;

	while (cur < array_size) {
		disk_key = (struct btrfs_disk_key *)ptr;
		btrfs_disk_key_to_cpu(&key, disk_key);

		len = sizeof(*disk_key);

		if (key.type == BTRFS_CHUNK_ITEM_KEY) {
			chunk = (struct btrfs_chunk *)(ptr + len);
			num_stripes = btrfs_stack_chunk_num_stripes(chunk);
			len += btrfs_chunk_item_size(num_stripes);
		} else {
			ret = -EIO;
			break;
		}
		if (key.objectid == chunk_objectid &&
		    key.offset == chunk_offset) {
			memmove(ptr, ptr + len, array_size - (cur + len));
			array_size -= len;
			btrfs_set_super_sys_array_size(super_copy, array_size);
		} else {
			ptr += len;
			cur += len;
		}
	}
	return ret;
}

static int btrfs_relocate_chunk(struct btrfs_root *root,
			 u64 chunk_tree, u64 chunk_objectid,
			 u64 chunk_offset)
{
	struct extent_map_tree *em_tree;
	struct btrfs_root *extent_root;
	struct btrfs_trans_handle *trans;
	struct extent_map *em;
	struct map_lookup *map;
	int ret;
	int i;

	root = root->fs_info->chunk_root;
	extent_root = root->fs_info->extent_root;
	em_tree = &root->fs_info->mapping_tree.map_tree;

	ret = btrfs_can_relocate(extent_root, chunk_offset);
	if (ret)
		return -ENOSPC;

	/* step one, relocate all the extents inside this chunk */
	ret = btrfs_relocate_block_group(extent_root, chunk_offset);
	if (ret)
		return ret;

	trans = btrfs_start_transaction(root, 0);
	BUG_ON(IS_ERR(trans));

	lock_chunks(root);

	/*
	 * step two, delete the device extents and the
	 * chunk tree entries
	 */
	read_lock(&em_tree->lock);
	em = lookup_extent_mapping(em_tree, chunk_offset, 1);
	read_unlock(&em_tree->lock);

	BUG_ON(!em || em->start > chunk_offset ||
	       em->start + em->len < chunk_offset);
	map = (struct map_lookup *)em->bdev;

	for (i = 0; i < map->num_stripes; i++) {
		ret = btrfs_free_dev_extent(trans, map->stripes[i].dev,
					    map->stripes[i].physical);
		BUG_ON(ret);

		if (map->stripes[i].dev) {
			ret = btrfs_update_device(trans, map->stripes[i].dev);
			BUG_ON(ret);
		}
	}
	ret = btrfs_free_chunk(trans, root, chunk_tree, chunk_objectid,
			       chunk_offset);

	BUG_ON(ret);

	trace_btrfs_chunk_free(root, map, chunk_offset, em->len);

	if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
		ret = btrfs_del_sys_chunk(root, chunk_objectid, chunk_offset);
		BUG_ON(ret);
	}

	ret = btrfs_remove_block_group(trans, extent_root, chunk_offset);
	BUG_ON(ret);

	write_lock(&em_tree->lock);
	remove_extent_mapping(em_tree, em);
	write_unlock(&em_tree->lock);

	kfree(map);
	em->bdev = NULL;

	/* once for the tree */
	free_extent_map(em);
	/* once for us */
	free_extent_map(em);

	unlock_chunks(root);
	btrfs_end_transaction(trans, root);
	return 0;
}

static int btrfs_relocate_sys_chunks(struct btrfs_root *root)
{
	struct btrfs_root *chunk_root = root->fs_info->chunk_root;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_chunk *chunk;
	struct btrfs_key key;
	struct btrfs_key found_key;
	u64 chunk_tree = chunk_root->root_key.objectid;
	u64 chunk_type;
	bool retried = false;
	int failed = 0;
	int ret;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

again:
	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
	key.offset = (u64)-1;
	key.type = BTRFS_CHUNK_ITEM_KEY;

	while (1) {
		ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
		if (ret < 0)
			goto error;
		BUG_ON(ret == 0);

		ret = btrfs_previous_item(chunk_root, path, key.objectid,
					  key.type);
		if (ret < 0)
			goto error;
		if (ret > 0)
			break;

		leaf = path->nodes[0];
		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);

		chunk = btrfs_item_ptr(leaf, path->slots[0],
				       struct btrfs_chunk);
		chunk_type = btrfs_chunk_type(leaf, chunk);
		btrfs_release_path(path);

		if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) {
			ret = btrfs_relocate_chunk(chunk_root, chunk_tree,
						   found_key.objectid,
						   found_key.offset);
			if (ret == -ENOSPC)
				failed++;
			else if (ret)
				BUG();
		}

		if (found_key.offset == 0)
			break;
		key.offset = found_key.offset - 1;
	}
	ret = 0;
	if (failed && !retried) {
		failed = 0;
		retried = true;
		goto again;
	} else if (failed && retried) {
		WARN_ON(1);
		ret = -ENOSPC;
	}
error:
	btrfs_free_path(path);
	return ret;
}

static int insert_balance_item(struct btrfs_root *root,
			       struct btrfs_balance_control *bctl)
{
	struct btrfs_trans_handle *trans;
	struct btrfs_balance_item *item;
	struct btrfs_disk_balance_args disk_bargs;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_key key;
	int ret, err;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		btrfs_free_path(path);
		return PTR_ERR(trans);
	}

	key.objectid = BTRFS_BALANCE_OBJECTID;
	key.type = BTRFS_BALANCE_ITEM_KEY;
	key.offset = 0;

	ret = btrfs_insert_empty_item(trans, root, path, &key,
				      sizeof(*item));
	if (ret)
		goto out;

	leaf = path->nodes[0];
	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_balance_item);

	memset_extent_buffer(leaf, 0, (unsigned long)item, sizeof(*item));

	btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->data);
	btrfs_set_balance_data(leaf, item, &disk_bargs);
	btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->meta);
	btrfs_set_balance_meta(leaf, item, &disk_bargs);
	btrfs_cpu_balance_args_to_disk(&disk_bargs, &bctl->sys);
	btrfs_set_balance_sys(leaf, item, &disk_bargs);

	btrfs_set_balance_flags(leaf, item, bctl->flags);

	btrfs_mark_buffer_dirty(leaf);
out:
	btrfs_free_path(path);
	err = btrfs_commit_transaction(trans, root);
	if (err && !ret)
		ret = err;
	return ret;
}

static int del_balance_item(struct btrfs_root *root)
{
	struct btrfs_trans_handle *trans;
	struct btrfs_path *path;
	struct btrfs_key key;
	int ret, err;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		btrfs_free_path(path);
		return PTR_ERR(trans);
	}

	key.objectid = BTRFS_BALANCE_OBJECTID;
	key.type = BTRFS_BALANCE_ITEM_KEY;
	key.offset = 0;

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret < 0)
		goto out;
	if (ret > 0) {
		ret = -ENOENT;
		goto out;
	}

	ret = btrfs_del_item(trans, root, path);
out:
	btrfs_free_path(path);
	err = btrfs_commit_transaction(trans, root);
	if (err && !ret)
		ret = err;
	return ret;
}

/*
 * This is a heuristic used to reduce the number of chunks balanced on
 * resume after balance was interrupted.
 */
static void update_balance_args(struct btrfs_balance_control *bctl)
{
	/*
	 * Turn on soft mode for chunk types that were being converted.
	 */
	if (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)
		bctl->data.flags |= BTRFS_BALANCE_ARGS_SOFT;
	if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)
		bctl->sys.flags |= BTRFS_BALANCE_ARGS_SOFT;
	if (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)
		bctl->meta.flags |= BTRFS_BALANCE_ARGS_SOFT;

	/*
	 * Turn on usage filter if is not already used.  The idea is
	 * that chunks that we have already balanced should be
	 * reasonably full.  Don't do it for chunks that are being
	 * converted - that will keep us from relocating unconverted
	 * (albeit full) chunks.
	 */
	if (!(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE) &&
	    !(bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
		bctl->data.flags |= BTRFS_BALANCE_ARGS_USAGE;
		bctl->data.usage = 90;
	}
	if (!(bctl->sys.flags & BTRFS_BALANCE_ARGS_USAGE) &&
	    !(bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
		bctl->sys.flags |= BTRFS_BALANCE_ARGS_USAGE;
		bctl->sys.usage = 90;
	}
	if (!(bctl->meta.flags & BTRFS_BALANCE_ARGS_USAGE) &&
	    !(bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
		bctl->meta.flags |= BTRFS_BALANCE_ARGS_USAGE;
		bctl->meta.usage = 90;
	}
}

/*
 * Should be called with both balance and volume mutexes held to
 * serialize other volume operations (add_dev/rm_dev/resize) with
 * restriper.  Same goes for unset_balance_control.
 */
static void set_balance_control(struct btrfs_balance_control *bctl)
{
	struct btrfs_fs_info *fs_info = bctl->fs_info;

	BUG_ON(fs_info->balance_ctl);

	spin_lock(&fs_info->balance_lock);
	fs_info->balance_ctl = bctl;
	spin_unlock(&fs_info->balance_lock);
}

static void unset_balance_control(struct btrfs_fs_info *fs_info)
{
	struct btrfs_balance_control *bctl = fs_info->balance_ctl;

	BUG_ON(!fs_info->balance_ctl);

	spin_lock(&fs_info->balance_lock);
	fs_info->balance_ctl = NULL;
	spin_unlock(&fs_info->balance_lock);

	kfree(bctl);
}

/*
 * Balance filters.  Return 1 if chunk should be filtered out
 * (should not be balanced).
 */
static int chunk_profiles_filter(u64 chunk_profile,
				 struct btrfs_balance_args *bargs)
{
	chunk_profile &= BTRFS_BLOCK_GROUP_PROFILE_MASK;

	if (chunk_profile == 0)
		chunk_profile = BTRFS_AVAIL_ALLOC_BIT_SINGLE;

	if (bargs->profiles & chunk_profile)
		return 0;

	return 1;
}

static u64 div_factor_fine(u64 num, int factor)
{
	if (factor <= 0)
		return 0;
	if (factor >= 100)
		return num;

	num *= factor;
	do_div(num, 100);
	return num;
}

static int chunk_usage_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
			      struct btrfs_balance_args *bargs)
{
	struct btrfs_block_group_cache *cache;
	u64 chunk_used, user_thresh;
	int ret = 1;

	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
	chunk_used = btrfs_block_group_used(&cache->item);

	user_thresh = div_factor_fine(cache->key.offset, bargs->usage);
	if (chunk_used < user_thresh)
		ret = 0;

	btrfs_put_block_group(cache);
	return ret;
}

static int chunk_devid_filter(struct extent_buffer *leaf,
			      struct btrfs_chunk *chunk,
			      struct btrfs_balance_args *bargs)
{
	struct btrfs_stripe *stripe;
	int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
	int i;

	for (i = 0; i < num_stripes; i++) {
		stripe = btrfs_stripe_nr(chunk, i);
		if (btrfs_stripe_devid(leaf, stripe) == bargs->devid)
			return 0;
	}

	return 1;
}

/* [pstart, pend) */
static int chunk_drange_filter(struct extent_buffer *leaf,
			       struct btrfs_chunk *chunk,
			       u64 chunk_offset,
			       struct btrfs_balance_args *bargs)
{
	struct btrfs_stripe *stripe;
	int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
	u64 stripe_offset;
	u64 stripe_length;
	int factor;
	int i;

	if (!(bargs->flags & BTRFS_BALANCE_ARGS_DEVID))
		return 0;

	if (btrfs_chunk_type(leaf, chunk) & (BTRFS_BLOCK_GROUP_DUP |
	     BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10))
		factor = 2;
	else
		factor = 1;
	factor = num_stripes / factor;

	for (i = 0; i < num_stripes; i++) {
		stripe = btrfs_stripe_nr(chunk, i);
		if (btrfs_stripe_devid(leaf, stripe) != bargs->devid)
			continue;

		stripe_offset = btrfs_stripe_offset(leaf, stripe);
		stripe_length = btrfs_chunk_length(leaf, chunk);
		do_div(stripe_length, factor);

		if (stripe_offset < bargs->pend &&
		    stripe_offset + stripe_length > bargs->pstart)
			return 0;
	}

	return 1;
}

/* [vstart, vend) */
static int chunk_vrange_filter(struct extent_buffer *leaf,
			       struct btrfs_chunk *chunk,
			       u64 chunk_offset,
			       struct btrfs_balance_args *bargs)
{
	if (chunk_offset < bargs->vend &&
	    chunk_offset + btrfs_chunk_length(leaf, chunk) > bargs->vstart)
		/* at least part of the chunk is inside this vrange */
		return 0;

	return 1;
}

static int chunk_soft_convert_filter(u64 chunk_profile,
				     struct btrfs_balance_args *bargs)
{
	if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
		return 0;

	chunk_profile &= BTRFS_BLOCK_GROUP_PROFILE_MASK;

	if (chunk_profile == 0)
		chunk_profile = BTRFS_AVAIL_ALLOC_BIT_SINGLE;

	if (bargs->target & chunk_profile)
		return 1;

	return 0;
}

static int should_balance_chunk(struct btrfs_root *root,
				struct extent_buffer *leaf,
				struct btrfs_chunk *chunk, u64 chunk_offset)
{
	struct btrfs_balance_control *bctl = root->fs_info->balance_ctl;
	struct btrfs_balance_args *bargs = NULL;
	u64 chunk_type = btrfs_chunk_type(leaf, chunk);

	/* type filter */
	if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) &
	      (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) {
		return 0;
	}

	if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
		bargs = &bctl->data;
	else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
		bargs = &bctl->sys;
	else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
		bargs = &bctl->meta;

	/* profiles filter */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_PROFILES) &&
	    chunk_profiles_filter(chunk_type, bargs)) {
		return 0;
	}

	/* usage filter */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE) &&
	    chunk_usage_filter(bctl->fs_info, chunk_offset, bargs)) {
		return 0;
	}

	/* devid filter */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_DEVID) &&
	    chunk_devid_filter(leaf, chunk, bargs)) {
		return 0;
	}

	/* drange filter, makes sense only with devid filter */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_DRANGE) &&
	    chunk_drange_filter(leaf, chunk, chunk_offset, bargs)) {
		return 0;
	}

	/* vrange filter */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_VRANGE) &&
	    chunk_vrange_filter(leaf, chunk, chunk_offset, bargs)) {
		return 0;
	}

	/* soft profile changing mode */
	if ((bargs->flags & BTRFS_BALANCE_ARGS_SOFT) &&
	    chunk_soft_convert_filter(chunk_type, bargs)) {
		return 0;
	}

	return 1;
}

static u64 div_factor(u64 num, int factor)
{
	if (factor == 10)
		return num;
	num *= factor;
	do_div(num, 10);
	return num;
}

static int __btrfs_balance(struct btrfs_fs_info *fs_info)
{
	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
	struct btrfs_root *chunk_root = fs_info->chunk_root;
	struct btrfs_root *dev_root = fs_info->dev_root;
	struct list_head *devices;
	struct btrfs_device *device;
	u64 old_size;
	u64 size_to_free;
	struct btrfs_chunk *chunk;
	struct btrfs_path *path;
	struct btrfs_key key;
	struct btrfs_key found_key;
	struct btrfs_trans_handle *trans;
	struct extent_buffer *leaf;
	int slot;
	int ret;
	int enospc_errors = 0;
	bool counting = true;

	/* step one make some room on all the devices */
	devices = &fs_info->fs_devices->devices;
	list_for_each_entry(device, devices, dev_list) {
		old_size = device->total_bytes;
		size_to_free = div_factor(old_size, 1);
		size_to_free = min(size_to_free, (u64)1 * 1024 * 1024);
		if (!device->writeable ||
		    device->total_bytes - device->bytes_used > size_to_free)
			continue;

		ret = btrfs_shrink_device(device, old_size - size_to_free);
		if (ret == -ENOSPC)
			break;
		BUG_ON(ret);

		trans = btrfs_start_transaction(dev_root, 0);
		BUG_ON(IS_ERR(trans));

		ret = btrfs_grow_device(trans, device, old_size);
		BUG_ON(ret);

		btrfs_end_transaction(trans, dev_root);
	}

	/* step two, relocate all the chunks */
	path = btrfs_alloc_path();
	if (!path) {
		ret = -ENOMEM;
		goto error;
	}

	/* zero out stat counters */
	spin_lock(&fs_info->balance_lock);
	memset(&bctl->stat, 0, sizeof(bctl->stat));
	spin_unlock(&fs_info->balance_lock);
again:
	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
	key.offset = (u64)-1;
	key.type = BTRFS_CHUNK_ITEM_KEY;

	while (1) {
		if ((!counting && atomic_read(&fs_info->balance_pause_req)) ||
		    atomic_read(&fs_info->balance_cancel_req)) {
			ret = -ECANCELED;
			goto error;
		}

		ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
		if (ret < 0)
			goto error;

		/*
		 * this shouldn't happen, it means the last relocate
		 * failed
		 */
		if (ret == 0)
			BUG(); /* FIXME break ? */

		ret = btrfs_previous_item(chunk_root, path, 0,
					  BTRFS_CHUNK_ITEM_KEY);
		if (ret) {
			ret = 0;
			break;
		}

		leaf = path->nodes[0];
		slot = path->slots[0];
		btrfs_item_key_to_cpu(leaf, &found_key, slot);

		if (found_key.objectid != key.objectid)
			break;

		/* chunk zero is special */
		if (found_key.offset == 0)
			break;

		chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);

		if (!counting) {
			spin_lock(&fs_info->balance_lock);
			bctl->stat.considered++;
			spin_unlock(&fs_info->balance_lock);
		}

		ret = should_balance_chunk(chunk_root, leaf, chunk,
					   found_key.offset);
		btrfs_release_path(path);
		if (!ret)
			goto loop;

		if (counting) {
			spin_lock(&fs_info->balance_lock);
			bctl->stat.expected++;
			spin_unlock(&fs_info->balance_lock);
			goto loop;
		}

		ret = btrfs_relocate_chunk(chunk_root,
					   chunk_root->root_key.objectid,
					   found_key.objectid,
					   found_key.offset);
		if (ret && ret != -ENOSPC)
			goto error;
		if (ret == -ENOSPC) {
			enospc_errors++;
		} else {
			spin_lock(&fs_info->balance_lock);
			bctl->stat.completed++;
			spin_unlock(&fs_info->balance_lock);
		}
loop:
		key.offset = found_key.offset - 1;
	}

	if (counting) {
		btrfs_release_path(path);
		counting = false;
		goto again;
	}
error:
	btrfs_free_path(path);
	if (enospc_errors) {
		printk(KERN_INFO "btrfs: %d enospc errors during balance\n",
		       enospc_errors);
		if (!ret)
			ret = -ENOSPC;
	}

	return ret;
}

static inline int balance_need_close(struct btrfs_fs_info *fs_info)
{
	/* cancel requested || normal exit path */
	return atomic_read(&fs_info->balance_cancel_req) ||
		(atomic_read(&fs_info->balance_pause_req) == 0 &&
		 atomic_read(&fs_info->balance_cancel_req) == 0);
}

static void __cancel_balance(struct btrfs_fs_info *fs_info)
{
	int ret;

	unset_balance_control(fs_info);
	ret = del_balance_item(fs_info->tree_root);
	BUG_ON(ret);
}

void update_ioctl_balance_args(struct btrfs_fs_info *fs_info, int lock,
			       struct btrfs_ioctl_balance_args *bargs);

/*
 * Should be called with both balance and volume mutexes held
 */
int btrfs_balance(struct btrfs_balance_control *bctl,
		  struct btrfs_ioctl_balance_args *bargs)
{
	struct btrfs_fs_info *fs_info = bctl->fs_info;
	u64 allowed;
	int ret;

	if (btrfs_fs_closing(fs_info) ||
	    atomic_read(&fs_info->balance_pause_req) ||
	    atomic_read(&fs_info->balance_cancel_req)) {
		ret = -EINVAL;
		goto out;
	}

	/*
	 * In case of mixed groups both data and meta should be picked,
	 * and identical options should be given for both of them.
	 */
	allowed = btrfs_super_incompat_flags(fs_info->super_copy);
	if ((allowed & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
	    (bctl->flags & (BTRFS_BALANCE_DATA | BTRFS_BALANCE_METADATA))) {
		if (!(bctl->flags & BTRFS_BALANCE_DATA) ||
		    !(bctl->flags & BTRFS_BALANCE_METADATA) ||
		    memcmp(&bctl->data, &bctl->meta, sizeof(bctl->data))) {
			printk(KERN_ERR "btrfs: with mixed groups data and "
			       "metadata balance options must be the same\n");
			ret = -EINVAL;
			goto out;
		}
	}

	/*
	 * Profile changing sanity checks.  Skip them if a simple
	 * balance is requested.
	 */
	if (!((bctl->data.flags | bctl->sys.flags | bctl->meta.flags) &
	      BTRFS_BALANCE_ARGS_CONVERT))
		goto do_balance;

	allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE;
	if (fs_info->fs_devices->num_devices == 1)
		allowed |= BTRFS_BLOCK_GROUP_DUP;
	else if (fs_info->fs_devices->num_devices < 4)
		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
	else
		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1 |
				BTRFS_BLOCK_GROUP_RAID10);

	if (!profile_is_valid(bctl->data.target, 1) ||
	    bctl->data.target & ~allowed) {
		printk(KERN_ERR "btrfs: unable to start balance with target "
		       "data profile %llu\n",
		       (unsigned long long)bctl->data.target);
		ret = -EINVAL;
		goto out;
	}
	if (!profile_is_valid(bctl->meta.target, 1) ||
	    bctl->meta.target & ~allowed) {
		printk(KERN_ERR "btrfs: unable to start balance with target "
		       "metadata profile %llu\n",
		       (unsigned long long)bctl->meta.target);
		ret = -EINVAL;
		goto out;
	}
	if (!profile_is_valid(bctl->sys.target, 1) ||
	    bctl->sys.target & ~allowed) {
		printk(KERN_ERR "btrfs: unable to start balance with target "
		       "system profile %llu\n",
		       (unsigned long long)bctl->sys.target);
		ret = -EINVAL;
		goto out;
	}

	if (bctl->data.target & BTRFS_BLOCK_GROUP_DUP) {
		printk(KERN_ERR "btrfs: dup for data is not allowed\n");
		ret = -EINVAL;
		goto out;
	}

	/* allow to reduce meta or sys integrity only if force set */
	allowed = BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
			BTRFS_BLOCK_GROUP_RAID10;
	if (((bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
	     (fs_info->avail_system_alloc_bits & allowed) &&
	     !(bctl->sys.target & allowed)) ||
	    ((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
	     (fs_info->avail_metadata_alloc_bits & allowed) &&
	     !(bctl->meta.target & allowed))) {
		if (bctl->flags & BTRFS_BALANCE_FORCE) {
			printk(KERN_INFO "btrfs: force reducing metadata "
			       "integrity\n");
		} else {
			printk(KERN_ERR "btrfs: balance will reduce metadata "
			       "integrity, use force if you want this\n");
			ret = -EINVAL;
			goto out;
		}
	}

do_balance:
	ret = insert_balance_item(fs_info->tree_root, bctl);
	if (ret && ret != -EEXIST)
		goto out;

	if (!(bctl->flags & BTRFS_BALANCE_RESUME)) {
		BUG_ON(ret == -EEXIST);
		set_balance_control(bctl);
	} else {
		BUG_ON(ret != -EEXIST);
		spin_lock(&fs_info->balance_lock);
		update_balance_args(bctl);
		spin_unlock(&fs_info->balance_lock);
	}

	atomic_inc(&fs_info->balance_running);
	mutex_unlock(&fs_info->balance_mutex);

	ret = __btrfs_balance(fs_info);

	mutex_lock(&fs_info->balance_mutex);
	atomic_dec(&fs_info->balance_running);

	if (bargs) {
		memset(bargs, 0, sizeof(*bargs));
		update_ioctl_balance_args(fs_info, 0, bargs);
	}

	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
	    balance_need_close(fs_info)) {
		__cancel_balance(fs_info);
	}

	wake_up(&fs_info->balance_wait_q);

	return ret;
out:
	if (bctl->flags & BTRFS_BALANCE_RESUME)
		__cancel_balance(fs_info);
	else
		kfree(bctl);
	return ret;
}

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;
	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 {
		printk(KERN_INFO "btrfs: continuing balance\n");
		ret = btrfs_balance(bctl, NULL);
	}

	mutex_unlock(&fs_info->balance_mutex);
	mutex_unlock(&fs_info->volume_mutex);
	return ret;
}

int btrfs_recover_balance(struct btrfs_root *tree_root)
{
	struct task_struct *tsk;
	struct btrfs_balance_control *bctl;
	struct btrfs_balance_item *item;
	struct btrfs_disk_balance_args disk_bargs;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_key key;
	int ret;

	path = btrfs_alloc_path();
	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);
	if (ret < 0)
		goto out_bctl;
	if (ret > 0) { /* ret = -ENOENT; */
		ret = 0;
		goto out_bctl;
	}

	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;

	btrfs_balance_data(leaf, item, &disk_bargs);
	btrfs_disk_balance_args_to_cpu(&bctl->data, &disk_bargs);
	btrfs_balance_meta(leaf, item, &disk_bargs);
	btrfs_disk_balance_args_to_cpu(&bctl->meta, &disk_bargs);
	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;

out_bctl:
	kfree(bctl);
out:
	btrfs_free_path(path);
	return ret;
}

int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
{
	int ret = 0;

	mutex_lock(&fs_info->balance_mutex);
	if (!fs_info->balance_ctl) {
		mutex_unlock(&fs_info->balance_mutex);
		return -ENOTCONN;
	}

	if (atomic_read(&fs_info->balance_running)) {
		atomic_inc(&fs_info->balance_pause_req);
		mutex_unlock(&fs_info->balance_mutex);

		wait_event(fs_info->balance_wait_q,
			   atomic_read(&fs_info->balance_running) == 0);

		mutex_lock(&fs_info->balance_mutex);
		/* we are good with balance_ctl ripped off from under us */
		BUG_ON(atomic_read(&fs_info->balance_running));
		atomic_dec(&fs_info->balance_pause_req);
	} else {
		ret = -ENOTCONN;
	}

	mutex_unlock(&fs_info->balance_mutex);
	return ret;
}

int btrfs_cancel_balance(struct btrfs_fs_info *fs_info)
{
	mutex_lock(&fs_info->balance_mutex);
	if (!fs_info->balance_ctl) {
		mutex_unlock(&fs_info->balance_mutex);
		return -ENOTCONN;
	}

	atomic_inc(&fs_info->balance_cancel_req);
	/*
	 * if we are running just wait and return, balance item is
	 * deleted in btrfs_balance in this case
	 */
	if (atomic_read(&fs_info->balance_running)) {
		mutex_unlock(&fs_info->balance_mutex);
		wait_event(fs_info->balance_wait_q,
			   atomic_read(&fs_info->balance_running) == 0);
		mutex_lock(&fs_info->balance_mutex);
	} else {
		/* __cancel_balance needs volume_mutex */
		mutex_unlock(&fs_info->balance_mutex);
		mutex_lock(&fs_info->volume_mutex);
		mutex_lock(&fs_info->balance_mutex);

		if (fs_info->balance_ctl)
			__cancel_balance(fs_info);

		mutex_unlock(&fs_info->volume_mutex);
	}

	BUG_ON(fs_info->balance_ctl || atomic_read(&fs_info->balance_running));
	atomic_dec(&fs_info->balance_cancel_req);
	mutex_unlock(&fs_info->balance_mutex);
	return 0;
}

/*
 * shrinking a device means finding all of the device extents past
 * the new size, and then following the back refs to the chunks.
 * The chunk relocation code actually frees the device extent
 */
int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
{
	struct btrfs_trans_handle *trans;
	struct btrfs_root *root = device->dev_root;
	struct btrfs_dev_extent *dev_extent = NULL;
	struct btrfs_path *path;
	u64 length;
	u64 chunk_tree;
	u64 chunk_objectid;
	u64 chunk_offset;
	int ret;
	int slot;
	int failed = 0;
	bool retried = false;
	struct extent_buffer *l;
	struct btrfs_key key;
	struct btrfs_super_block *super_copy = root->fs_info->super_copy;
	u64 old_total = btrfs_super_total_bytes(super_copy);
	u64 old_size = device->total_bytes;
	u64 diff = device->total_bytes - new_size;

	if (new_size >= device->total_bytes)
		return -EINVAL;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;

	path->reada = 2;

	lock_chunks(root);

	device->total_bytes = new_size;
	if (device->writeable) {
		device->fs_devices->total_rw_bytes -= diff;
		spin_lock(&root->fs_info->free_chunk_lock);
		root->fs_info->free_chunk_space -= diff;
		spin_unlock(&root->fs_info->free_chunk_lock);
	}
	unlock_chunks(root);

again:
	key.objectid = device->devid;
	key.offset = (u64)-1;
	key.type = BTRFS_DEV_EXTENT_KEY;

	while (1) {
		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
		if (ret < 0)
			goto done;

		ret = btrfs_previous_item(root, path, 0, key.type);
		if (ret < 0)
			goto done;
		if (ret) {
			ret = 0;
			btrfs_release_path(path);
			break;
		}

		l = path->nodes[0];
		slot = path->slots[0];
		btrfs_item_key_to_cpu(l, &key, path->slots[0]);

		if (key.objectid != device->devid) {
			btrfs_release_path(path);
			break;
		}

		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
		length = btrfs_dev_extent_length(l, dev_extent);

		if (key.offset + length <= new_size) {
			btrfs_release_path(path);
			break;
		}

		chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent);
		chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent);
		chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
		btrfs_release_path(path);

		ret = btrfs_relocate_chunk(root, chunk_tree, chunk_objectid,
					   chunk_offset);
		if (ret && ret != -ENOSPC)
			goto done;
		if (ret == -ENOSPC)
			failed++;
		key.offset -= 1;
	}

	if (failed && !retried) {
		failed = 0;
		retried = true;
		goto again;
	} else if (failed && retried) {
		ret = -ENOSPC;
		lock_chunks(root);

		device->total_bytes = old_size;
		if (device->writeable)
			device->fs_devices->total_rw_bytes += diff;
		spin_lock(&root->fs_info->free_chunk_lock);
		root->fs_info->free_chunk_space += diff;
		spin_unlock(&root->fs_info->free_chunk_lock);
		unlock_chunks(root);
		goto done;
	}

	/* Shrinking succeeded, else we would be at "done". */
	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		ret = PTR_ERR(trans);
		goto done;
	}

	lock_chunks(root);

	device->disk_total_bytes = new_size;
	/* Now btrfs_update_device() will change the on-disk size. */
	ret = btrfs_update_device(trans, device);
	if (ret) {
		unlock_chunks(root);
		btrfs_end_transaction(trans, root);
		goto done;
	}
	WARN_ON(diff > old_total);
	btrfs_set_super_total_bytes(super_copy, old_total - diff);
	unlock_chunks(root);
	btrfs_end_transaction(trans, root);
done:
	btrfs_free_path(path);
	return ret;
}

static int btrfs_add_system_chunk(struct btrfs_root *root,
			   struct btrfs_key *key,
			   struct btrfs_chunk *chunk, int item_size)
{
	struct btrfs_super_block *super_copy = root->fs_info->super_copy;
	struct btrfs_disk_key disk_key;
	u32 array_size;
	u8 *ptr;

	array_size = btrfs_super_sys_array_size(super_copy