bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info,
					struct btrfs_device *failing_dev)
{
	struct extent_map_tree *map_tree = &fs_info->mapping_tree;
	struct extent_map *em;
	u64 next_start = 0;
	bool ret = true;

	read_lock(&map_tree->lock);
	em = lookup_extent_mapping(map_tree, 0, (u64)-1);
	read_unlock(&map_tree->lock);
	/* No chunk at all? Return false anyway */
	if (!em) {
		ret = false;
		goto out;
	}
	while (em) {
		struct map_lookup *map;
		int missing = 0;
		int max_tolerated;
		int i;

		map = em->map_lookup;
		max_tolerated =
			btrfs_get_num_tolerated_disk_barrier_failures(
					map->type);
		for (i = 0; i < map->num_stripes; i++) {
			struct btrfs_device *dev = map->stripes[i].dev;

			if (!dev || !dev->bdev ||
			    test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state) ||
			    dev->last_flush_error)
				missing++;
			else if (failing_dev && failing_dev == dev)
				missing++;
		}
		if (missing > max_tolerated) {
			if (!failing_dev)
				btrfs_warn(fs_info,
	"chunk %llu missing %d devices, max tolerance is %d for writable mount",
				   em->start, missing, max_tolerated);
			free_extent_map(em);
			ret = false;
			goto out;
		}
		next_start = extent_map_end(em);
		free_extent_map(em);

		read_lock(&map_tree->lock);
		em = lookup_extent_mapping(map_tree, next_start,
					   (u64)(-1) - next_start);
		read_unlock(&map_tree->lock);
	}
out:
	return ret;
}


static struct btrfs_fs_devices *find_fsid_reverted_metadata(
				struct btrfs_super_block *disk_super)
{
	struct btrfs_fs_devices *fs_devices;

	/*
	 * Handle the case where the scanned device is part of an fs whose last
	 * metadata UUID change reverted it to the original FSID. At the same
	 * time * fs_devices was first created by another constitutent device
	 * which didn't fully observe the operation. This results in an
	 * btrfs_fs_devices created with metadata/fsid different AND
	 * btrfs_fs_devices::fsid_change set AND the metadata_uuid of the
	 * fs_devices equal to the FSID of the disk.
	 */
	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
		if (memcmp(fs_devices->fsid, fs_devices->metadata_uuid,
			   BTRFS_FSID_SIZE) != 0 &&
		    memcmp(fs_devices->metadata_uuid, disk_super->fsid,
			   BTRFS_FSID_SIZE) == 0 &&
		    fs_devices->fsid_change)
			return fs_devices;
	}

	return NULL;
}

btrfs: fix NULL pointer dereference when deleting device by invalid id

[BUG]
It's easy to trigger NULL pointer dereference, just by removing a
non-existing device id:

 # mkfs.btrfs -f -m single -d single /dev/test/scratch1 \
				     /dev/test/scratch2
 # mount /dev/test/scratch1 /mnt/btrfs
 # btrfs device remove 3 /mnt/btrfs

Then we have the following kernel NULL pointer dereference:

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor read access in kernel mode
 #PF: error_code(0x0000) - not-present page
 PGD 0 P4D 0
 Oops: 0000 [#1] PREEMPT SMP NOPTI
 CPU: 9 PID: 649 Comm: btrfs Not tainted 5.14.0-rc3-custom+ #35
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
 RIP: 0010:btrfs_rm_device+0x4de/0x6b0 [btrfs]
  btrfs_ioctl+0x18bb/0x3190 [btrfs]
  ? lock_is_held_type+0xa5/0x120
  ? find_held_lock.constprop.0+0x2b/0x80
  ? do_user_addr_fault+0x201/0x6a0
  ? lock_release+0xd2/0x2d0
  ? __x64_sys_ioctl+0x83/0xb0
  __x64_sys_ioctl+0x83/0xb0
  do_syscall_64+0x3b/0x90
  entry_SYSCALL_64_after_hwframe+0x44/0xae

[CAUSE]
Commit a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return
btrfs_device directly") moves the "missing" device path check into
btrfs_rm_device().

But btrfs_rm_device() itself can have case where it only receives
@devid, with NULL as @device_path.

In that case, calling strcmp() on NULL will trigger the NULL pointer
dereference.

Before that commit, we handle the "missing" case inside
btrfs_find_device_by_devspec(), which will not check @device_path at all
if @devid is provided, thus no way to trigger the bug.

[FIX]
Before calling strcmp(), also make sure @device_path is not NULL.

Fixes: a27a94c2b0c7 ("btrfs: Make btrfs_find_device_by_devspec return btrfs_device directly")
CC: stable@vger.kernel.org # 5.4+
Reported-by: butt3rflyh4ck <butterflyhuangxx@gmail.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>


static void init_alloc_chunk_ctl_policy_zoned(
				      struct btrfs_fs_devices *fs_devices,
				      struct alloc_chunk_ctl *ctl)
{
	u64 zone_size = fs_devices->fs_info->zone_size;
	u64 limit;
	int min_num_stripes = ctl->devs_min * ctl->dev_stripes;
	int min_data_stripes = (min_num_stripes - ctl->nparity) / ctl->ncopies;
	u64 min_chunk_size = min_data_stripes * zone_size;
	u64 type = ctl->type;

	ctl->max_stripe_size = zone_size;
	if (type & BTRFS_BLOCK_GROUP_DATA) {
		ctl->max_chunk_size = round_down(BTRFS_MAX_DATA_CHUNK_SIZE,
						 zone_size);
	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
		ctl->max_chunk_size = ctl->max_stripe_size;
	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
		ctl->max_chunk_size = 2 * ctl->max_stripe_size;
		ctl->devs_max = min_t(int, ctl->devs_max,
				      BTRFS_MAX_DEVS_SYS_CHUNK);
	} else {
		BUG();
	}

	/* We don't want a chunk larger than 10% of writable space */
	limit = max(round_down(div_factor(fs_devices->total_rw_bytes, 1),
			       zone_size),
		    min_chunk_size);
	ctl->max_chunk_size = min(limit, ctl->max_chunk_size);
	ctl->dev_extent_min = zone_size * ctl->dev_stripes;
}


static int decide_stripe_size(struct btrfs_fs_devices *fs_devices,
			      struct alloc_chunk_ctl *ctl,
			      struct btrfs_device_info *devices_info)
{
	struct btrfs_fs_info *info = fs_devices->fs_info;

	/*
	 * Round down to number of usable stripes, devs_increment can be any
	 * number so we can't use round_down() that requires power of 2, while
	 * rounddown is safe.
	 */
	ctl->ndevs = rounddown(ctl->ndevs, ctl->devs_increment);

	if (ctl->ndevs < ctl->devs_min) {
		if (btrfs_test_opt(info, ENOSPC_DEBUG)) {
			btrfs_debug(info,
	"%s: not enough devices with free space: have=%d minimum required=%d",
				    __func__, ctl->ndevs, ctl->devs_min);
		}
		return -ENOSPC;
	}

	ctl->ndevs = min(ctl->ndevs, ctl->devs_max);

	switch (fs_devices->chunk_alloc_policy) {
	case BTRFS_CHUNK_ALLOC_REGULAR:
		return decide_stripe_size_regular(ctl, devices_info);
	case BTRFS_CHUNK_ALLOC_ZONED:
		return decide_stripe_size_zoned(ctl, devices_info);
	default:
		BUG();
	}
}


static int get_extra_mirror_from_replace(struct btrfs_fs_info *fs_info,
					 u64 logical, u64 length,
					 u64 srcdev_devid, int *mirror_num,
					 u64 *physical)
{
	struct btrfs_bio *bbio = NULL;
	int num_stripes;
	int index_srcdev = 0;
	int found = 0;
	u64 physical_of_found = 0;
	int i;
	int ret = 0;

	ret = __btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS,
				logical, &length, &bbio, 0, 0);
	if (ret) {
		ASSERT(bbio == NULL);
		return ret;
	}

	num_stripes = bbio->num_stripes;
	if (*mirror_num > num_stripes) {
		/*
		 * BTRFS_MAP_GET_READ_MIRRORS does not contain this mirror,
		 * that means that the requested area is not left of the left
		 * cursor
		 */
		btrfs_put_bbio(bbio);
		return -EIO;
	}

	/*
	 * process the rest of the function using the mirror_num of the source
	 * drive. Therefore look it up first.  At the end, patch the device
	 * pointer to the one of the target drive.
	 */
	for (i = 0; i < num_stripes; i++) {
		if (bbio->stripes[i].dev->devid != srcdev_devid)
			continue;

		/*
		 * In case of DUP, in order to keep it simple, only add the
		 * mirror with the lowest physical address
		 */
		if (found &&
		    physical_of_found <= bbio->stripes[i].physical)
			continue;

		index_srcdev = i;
		found = 1;
		physical_of_found = bbio->stripes[i].physical;
	}

	btrfs_put_bbio(bbio);

	ASSERT(found);
	if (!found)
		return -EIO;

	*mirror_num = index_srcdev + 1;
	*physical = physical_of_found;
	return ret;
}


static void warn_32bit_meta_chunk(struct btrfs_fs_info *fs_info,
				  u64 logical, u64 length, u64 type)
{
	if (!(type & BTRFS_BLOCK_GROUP_METADATA))
		return;

	if (logical + length < BTRFS_32BIT_EARLY_WARN_THRESHOLD)
		return;

	btrfs_warn_32bit_limit(fs_info);
}


static void readahead_tree_node_children(struct extent_buffer *node)
{
	int i;
	const int nr_items = btrfs_header_nritems(node);

	for (i = 0; i < nr_items; i++)
		btrfs_readahead_node_child(node, i);
}


static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
				fmode_t flags, void *holder)
{
	struct btrfs_device *device;
	struct btrfs_device *latest_dev = NULL;
	struct btrfs_device *tmp_device;

	flags |= FMODE_EXCL;

	list_for_each_entry_safe(device, tmp_device, &fs_devices->devices,
				 dev_list) {
		int ret;

		ret = btrfs_open_one_device(fs_devices, device, flags, holder);
		if (ret == 0 &&
		    (!latest_dev || device->generation > latest_dev->generation)) {
			latest_dev = device;
		} else if (ret == -ENODATA) {
			fs_devices->num_devices--;
			list_del(&device->dev_list);
			btrfs_free_device(device);
		}
	}
	if (fs_devices->open_devices == 0)
		return -EINVAL;

	fs_devices->opened = 1;
	fs_devices->latest_bdev = latest_dev->bdev;
	fs_devices->total_rw_bytes = 0;
	fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_REGULAR;
	fs_devices->read_policy = BTRFS_READ_POLICY_PID;

	return 0;
}


static int find_free_dev_extent_start(struct btrfs_device *device,
				u64 num_bytes, u64 search_start, u64 *start,
				u64 *len)
{
	struct btrfs_fs_info *fs_info = device->fs_info;
	struct btrfs_root *root = fs_info->dev_root;
	struct btrfs_key key;
	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_end = device->total_bytes;
	int ret;
	int slot;
	struct extent_buffer *l;

	search_start = dev_extent_search_start(device, search_start);

	WARN_ON(device->zone_info &&
		!IS_ALIGNED(num_bytes, device->zone_info->zone_size));

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

	max_hole_start = search_start;
	max_hole_size = 0;

again:
	if (search_start >= search_end ||
		test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
		ret = -ENOSPC;
		goto out;
	}

	path->reada = READA_FORWARD;
	path->search_commit_root = 1;
	path->skip_locking = 1;

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

	ret = btrfs_search_backwards(root, &key, path);
	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 (key.type != BTRFS_DEV_EXTENT_KEY)
			goto next;

		if (key.offset > search_start) {
			hole_size = key.offset - search_start;
			dev_extent_hole_check(device, &search_start, &hole_size,
					      num_bytes);

			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 (dev_extent_hole_check(device, &search_start, &hole_size,
					  num_bytes)) {
			btrfs_release_path(path);
			goto again;
		}

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

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

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


void btrfs_rm_dev_replace_free_srcdev(struct btrfs_device *srcdev)
{
	struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;

	mutex_lock(&uuid_mutex);

	btrfs_close_bdev(srcdev);
	synchronize_rcu();
	btrfs_free_device(srcdev);

	/* if this is no devs we rather delete the fs_devices */
	if (!fs_devices->num_devices) {
		/*
		 * On a mounted FS, num_devices can't be zero unless it's a
		 * seed. In case of a seed device being replaced, the replace
		 * target added to the sprout FS, so there will be no more
		 * device left under the seed FS.
		 */
		ASSERT(fs_devices->seeding);

		list_del_init(&fs_devices->seed_list);
		close_fs_devices(fs_devices);
		free_fs_devices(fs_devices);
	}
	mutex_unlock(&uuid_mutex);
}


static struct btrfs_fs_devices *find_fsid_changed(
					struct btrfs_super_block *disk_super)
{
	struct btrfs_fs_devices *fs_devices;

	/*
	 * Handles the case where scanned device is part of an fs that had
	 * multiple successful changes of FSID but currently device didn't
	 * observe it. Meaning our fsid will be different than theirs. We need
	 * to handle two subcases :
	 *  1 - The fs still continues to have different METADATA/FSID uuids.
	 *  2 - The fs is switched back to its original FSID (METADATA/FSID
	 *  are equal).
	 */
	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
		/* Changed UUIDs */
		if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
			   BTRFS_FSID_SIZE) != 0 &&
		    memcmp(fs_devices->metadata_uuid, disk_super->metadata_uuid,
			   BTRFS_FSID_SIZE) == 0 &&
		    memcmp(fs_devices->fsid, disk_super->fsid,
			   BTRFS_FSID_SIZE) != 0)
			return fs_devices;

		/* Unchanged UUIDs */
		if (memcmp(fs_devices->metadata_uuid, fs_devices->fsid,
			   BTRFS_FSID_SIZE) == 0 &&
		    memcmp(fs_devices->fsid, disk_super->metadata_uuid,
			   BTRFS_FSID_SIZE) == 0)
			return fs_devices;
	}

	return NULL;
}


void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
{
	struct btrfs_fs_devices *fs_devices = tgtdev->fs_info->fs_devices;

	mutex_lock(&fs_devices->device_list_mutex);

	btrfs_sysfs_remove_device(tgtdev);

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

	fs_devices->num_devices--;

	btrfs_assign_next_active_device(tgtdev, NULL);

	list_del_rcu(&tgtdev->dev_list);

	mutex_unlock(&fs_devices->device_list_mutex);

	/*
	 * The update_dev_time() with in btrfs_scratch_superblocks()
	 * may lead to a call to btrfs_show_devname() which will try
	 * to hold device_list_mutex. And here this device
	 * is already out of device list, so we don't have to hold
	 * the device_list_mutex lock.
	 */
	btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev,
				  tgtdev->name->str);

	btrfs_close_bdev(tgtdev);
	synchronize_rcu();
	btrfs_free_device(tgtdev);
}


struct btrfs_device *btrfs_find_device(struct btrfs_fs_devices *fs_devices,
				       u64 devid, u8 *uuid, u8 *fsid)
{
	struct btrfs_device *device;
	struct btrfs_fs_devices *seed_devs;

	if (!fsid || !memcmp(fs_devices->metadata_uuid, fsid, BTRFS_FSID_SIZE)) {
		list_for_each_entry(device, &fs_devices->devices, dev_list) {
			if (device->devid == devid &&
			    (!uuid || memcmp(device->uuid, uuid,
					     BTRFS_UUID_SIZE) == 0))
				return device;
		}
	}

	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
		if (!fsid ||
		    !memcmp(seed_devs->metadata_uuid, fsid, BTRFS_FSID_SIZE)) {
			list_for_each_entry(device, &seed_devs->devices,
					    dev_list) {
				if (device->devid == devid &&
				    (!uuid || memcmp(device->uuid, uuid,
						     BTRFS_UUID_SIZE) == 0))
					return device;
			}
		}
	}

	return NULL;
}


static u64 find_next_chunk(struct btrfs_fs_info *fs_info)
{
	struct extent_map_tree *em_tree;
	struct extent_map *em;
	struct rb_node *n;
	u64 ret = 0;

	em_tree = &fs_info->mapping_tree;
	read_lock(&em_tree->lock);
	n = rb_last(&em_tree->map.rb_root);
	if (n) {
		em = rb_entry(n, struct extent_map, rb_node);
		ret = em->start + em->len;
	}
	read_unlock(&em_tree->lock);

	return ret;
}


static noinline int init_first_rw_device(struct btrfs_trans_handle *trans)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	u64 alloc_profile;
	struct btrfs_block_group *meta_bg;
	struct btrfs_block_group *sys_bg;

	/*
	 * When adding a new device for sprouting, the seed device is read-only
	 * so we must first allocate a metadata and a system chunk. But before
	 * adding the block group items to the extent, device and chunk btrees,
	 * we must first:
	 *
	 * 1) Create both chunks without doing any changes to the btrees, as
	 *    otherwise we would get -ENOSPC since the block groups from the
	 *    seed device are read-only;
	 *
	 * 2) Add the device item for the new sprout device - finishing the setup
	 *    of a new block group requires updating the device item in the chunk
	 *    btree, so it must exist when we attempt to do it. The previous step
	 *    ensures this does not fail with -ENOSPC.
	 *
	 * After that we can add the block group items to their btrees:
	 * update existing device item in the chunk btree, add a new block group
	 * item to the extent btree, add a new chunk item to the chunk btree and
	 * finally add the new device extent items to the devices btree.
	 */

	alloc_profile = btrfs_metadata_alloc_profile(fs_info);
	meta_bg = btrfs_alloc_chunk(trans, alloc_profile);
	if (IS_ERR(meta_bg))
		return PTR_ERR(meta_bg);

	alloc_profile = btrfs_system_alloc_profile(fs_info);
	sys_bg = btrfs_alloc_chunk(trans, alloc_profile);
	if (IS_ERR(sys_bg))
		return PTR_ERR(sys_bg);

	return 0;
}


void btrfs_release_disk_super(struct btrfs_super_block *super)
{
	struct page *page = virt_to_page(super);

	put_page(page);
}


static void handle_ops_on_dev_replace(enum btrfs_map_op op,
				      struct btrfs_bio **bbio_ret,
				      struct btrfs_dev_replace *dev_replace,
				      u64 logical,
				      int *num_stripes_ret, int *max_errors_ret)
{
	struct btrfs_bio *bbio = *bbio_ret;
	u64 srcdev_devid = dev_replace->srcdev->devid;
	int tgtdev_indexes = 0;
	int num_stripes = *num_stripes_ret;
	int max_errors = *max_errors_ret;
	int i;

	if (op == BTRFS_MAP_WRITE) {
		int index_where_to_add;

		/*
		 * A block group which have "to_copy" set will eventually
		 * copied by dev-replace process. We can avoid cloning IO here.
		 */
		if (is_block_group_to_copy(dev_replace->srcdev->fs_info, logical))
			return;

		/*
		 * duplicate the write operations while the dev replace
		 * procedure is running. Since the copying of the old disk to
		 * the new disk takes place at run time while the filesystem is
		 * mounted writable, the regular write operations to the old
		 * disk have to be duplicated to go to the new disk as well.
		 *
		 * Note that device->missing is handled by the caller, and that
		 * the write to the old disk is already set up in the stripes
		 * array.
		 */
		index_where_to_add = num_stripes;
		for (i = 0; i < num_stripes; i++) {
			if (bbio->stripes[i].dev->devid == srcdev_devid) {
				/* write to new disk, too */
				struct btrfs_bio_stripe *new =
					bbio->stripes + index_where_to_add;
				struct btrfs_bio_stripe *old =
					bbio->stripes + i;

				new->physical = old->physical;
				new->length = old->length;
				new->dev = dev_replace->tgtdev;
				bbio->tgtdev_map[i] = index_where_to_add;
				index_where_to_add++;
				max_errors++;
				tgtdev_indexes++;
			}
		}
		num_stripes = index_where_to_add;
	} else if (op == BTRFS_MAP_GET_READ_MIRRORS) {
		int index_srcdev = 0;
		int found = 0;
		u64 physical_of_found = 0;

		/*
		 * During the dev-replace procedure, the target drive can also
		 * be used to read data in case it is needed to repair a corrupt
		 * block elsewhere. This is possible if the requested area is
		 * left of the left cursor. In this area, the target drive is a
		 * full copy of the source drive.
		 */
		for (i = 0; i < num_stripes; i++) {
			if (bbio->stripes[i].dev->devid == srcdev_devid) {
				/*
				 * In case of DUP, in order to keep it simple,
				 * only add the mirror with the lowest physical
				 * address
				 */
				if (found &&
				    physical_of_found <=
				     bbio->stripes[i].physical)
					continue;
				index_srcdev = i;
				found = 1;
				physical_of_found = bbio->stripes[i].physical;
			}
		}
		if (found) {
			struct btrfs_bio_stripe *tgtdev_stripe =
				bbio->stripes + num_stripes;

			tgtdev_stripe->physical = physical_of_found;
			tgtdev_stripe->length =
				bbio->stripes[index_srcdev].length;
			tgtdev_stripe->dev = dev_replace->tgtdev;
			bbio->tgtdev_map[index_srcdev] = num_stripes;

			tgtdev_indexes++;
			num_stripes++;
		}
	}

	*num_stripes_ret = num_stripes;
	*max_errors_ret = max_errors;
	bbio->num_tgtdevs = tgtdev_indexes;
	*bbio_ret = bbio;
}


static int check_32bit_meta_chunk(struct btrfs_fs_info *fs_info,
				  u64 logical, u64 length, u64 type)
{
	if (!(type & BTRFS_BLOCK_GROUP_METADATA))
		return 0;

	if (logical + length < MAX_LFS_FILESIZE)
		return 0;

	btrfs_err_32bit_limit(fs_info);
	return -EOVERFLOW;
}


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;
	u64 chunk_type;
	struct btrfs_chunk *chunk;
	struct btrfs_path *path = NULL;
	struct btrfs_key key;
	struct btrfs_key found_key;
	struct extent_buffer *leaf;
	int slot;
	int ret;
	int enospc_errors = 0;
	bool counting = true;
	/* The single value limit and min/max limits use the same bytes in the */
	u64 limit_data = bctl->data.limit;
	u64 limit_meta = bctl->meta.limit;
	u64 limit_sys = bctl->sys.limit;
	u32 count_data = 0;
	u32 count_meta = 0;
	u32 count_sys = 0;
	int chunk_reserved = 0;

	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:
	if (!counting) {
		/*
		 * The single value limit and min/max limits use the same bytes
		 * in the
		 */
		bctl->data.limit = limit_data;
		bctl->meta.limit = limit_meta;
		bctl->sys.limit = limit_sys;
	}
	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;
		}

		mutex_lock(&fs_info->reclaim_bgs_lock);
		ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
		if (ret < 0) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			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) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			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) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			break;
		}

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

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

		ret = should_balance_chunk(leaf, chunk, found_key.offset);

		btrfs_release_path(path);
		if (!ret) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			goto loop;
		}

		if (counting) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			spin_lock(&fs_info->balance_lock);
			bctl->stat.expected++;
			spin_unlock(&fs_info->balance_lock);

			if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
				count_data++;
			else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
				count_sys++;
			else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
				count_meta++;

			goto loop;
		}

		/*
		 * Apply limit_min filter, no need to check if the LIMITS
		 * filter is used, limit_min is 0 by default
		 */
		if (((chunk_type & BTRFS_BLOCK_GROUP_DATA) &&
					count_data < bctl->data.limit_min)
				|| ((chunk_type & BTRFS_BLOCK_GROUP_METADATA) &&
					count_meta < bctl->meta.limit_min)
				|| ((chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) &&
					count_sys < bctl->sys.limit_min)) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			goto loop;
		}

		if (!chunk_reserved) {
			/*
			 * We may be relocating the only data chunk we have,
			 * which could potentially end up with losing data's
			 * raid profile, so lets allocate an empty one in
			 * advance.
			 */
			ret = btrfs_may_alloc_data_chunk(fs_info,
							 found_key.offset);
			if (ret < 0) {
				mutex_unlock(&fs_info->reclaim_bgs_lock);
				goto error;
			} else if (ret == 1) {
				chunk_reserved = 1;
			}
		}

		ret = btrfs_relocate_chunk(fs_info, found_key.offset);
		mutex_unlock(&fs_info->reclaim_bgs_lock);
		if (ret == -ENOSPC) {
			enospc_errors++;
		} else if (ret == -ETXTBSY) {
			btrfs_info(fs_info,
	   "skipping relocation of block group %llu due to active swapfile",
				   found_key.offset);
			ret = 0;
		} else if (ret) {
			goto error;
		} else {
			spin_lock(&fs_info->balance_lock);
			bctl->stat.completed++;
			spin_unlock(&fs_info->balance_lock);
		}
loop:
		if (found_key.offset == 0)
			break;
		key.offset = found_key.offset - 1;
	}

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

	return ret;
}


static int remove_chunk_item(struct btrfs_trans_handle *trans,
			     struct map_lookup *map, u64 chunk_offset)
{
	int i;

	/*
	 * Removing chunk items and updating the device items in the chunks btree
	 * requires holding the chunk_mutex.
	 * See the comment at btrfs_chunk_alloc() for the details.
	 */
	lockdep_assert_held(&trans->fs_info->chunk_mutex);

	for (i = 0; i < map->num_stripes; i++) {
		int ret;

		ret = btrfs_update_device(trans, map->stripes[i].dev);
		if (ret)
			return ret;
	}

	return btrfs_free_chunk(trans, chunk_offset);
}


static bool is_block_group_to_copy(struct btrfs_fs_info *fs_info, u64 logical)
{
	struct btrfs_block_group *cache;
	bool ret;

	/* Non zoned filesystem does not use "to_copy" flag */
	if (!btrfs_is_zoned(fs_info))
		return false;

	cache = btrfs_lookup_block_group(fs_info, logical);

	spin_lock(&cache->lock);
	ret = cache->to_copy;
	spin_unlock(&cache->lock);

	btrfs_put_block_group(cache);
	return ret;
}


static int btrfs_del_sys_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
{
	struct btrfs_super_block *super_copy = 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;

	lockdep_assert_held(&fs_info->chunk_mutex);
	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 == BTRFS_FIRST_CHUNK_TREE_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;
}


int btrfs_read_sys_array(struct btrfs_fs_info *fs_info)
{
	struct btrfs_root *root = fs_info->tree_root;
	struct btrfs_super_block *super_copy = fs_info->super_copy;
	struct extent_buffer *sb;
	struct btrfs_disk_key *disk_key;
	struct btrfs_chunk *chunk;
	u8 *array_ptr;
	unsigned long sb_array_offset;
	int ret = 0;
	u32 num_stripes;
	u32 array_size;
	u32 len = 0;
	u32 cur_offset;
	u64 type;
	struct btrfs_key key;

	ASSERT(BTRFS_SUPER_INFO_SIZE <= fs_info->nodesize);
	/*
	 * This will create extent buffer of nodesize, superblock size is
	 * fixed to BTRFS_SUPER_INFO_SIZE. If nodesize > sb size, this will
	 * overallocate but we can keep it as-is, only the first page is used.
	 */
	sb = btrfs_find_create_tree_block(fs_info, BTRFS_SUPER_INFO_OFFSET,
					  root->root_key.objectid, 0);
	if (IS_ERR(sb))
		return PTR_ERR(sb);
	set_extent_buffer_uptodate(sb);
	/*
	 * The sb extent buffer is artificial and just used to read the system array.
	 * set_extent_buffer_uptodate() call does not properly mark all it's
	 * pages up-to-date when the page is larger: extent does not cover the
	 * whole page and consequently check_page_uptodate does not find all
	 * the page's extents up-to-date (the hole beyond sb),
	 * write_extent_buffer then triggers a WARN_ON.
	 *
	 * Regular short extents go through mark_extent_buffer_dirty/writeback cycle,
	 * but sb spans only this function. Add an explicit SetPageUptodate call
	 * to silence the warning eg. on PowerPC 64.
	 */
	if (PAGE_SIZE > BTRFS_SUPER_INFO_SIZE)
		SetPageUptodate(sb->pages[0]);

	write_extent_buffer(sb, super_copy, 0, BTRFS_SUPER_INFO_SIZE);
	array_size = btrfs_super_sys_array_size(super_copy);

	array_ptr = super_copy->sys_chunk_array;
	sb_array_offset = offsetof(struct btrfs_super_block, sys_chunk_array);
	cur_offset = 0;

	while (cur_offset < array_size) {
		disk_key = (struct btrfs_disk_key *)array_ptr;
		len = sizeof(*disk_key);
		if (cur_offset + len > array_size)
			goto out_short_read;

		btrfs_disk_key_to_cpu(&key, disk_key);

		array_ptr += len;
		sb_array_offset += len;
		cur_offset += len;

		if (key.type != BTRFS_CHUNK_ITEM_KEY) {
			btrfs_err(fs_info,
			    "unexpected item type %u in sys_array at offset %u",
				  (u32)key.type, cur_offset);
			ret = -EIO;
			break;
		}

		chunk = (struct btrfs_chunk *)sb_array_offset;
		/*
		 * At least one btrfs_chunk with one stripe must be present,
		 * exact stripe count check comes afterwards
		 */
		len = btrfs_chunk_item_size(1);
		if (cur_offset + len > array_size)
			goto out_short_read;

		num_stripes = btrfs_chunk_num_stripes(sb, chunk);
		if (!num_stripes) {
			btrfs_err(fs_info,
			"invalid number of stripes %u in sys_array at offset %u",
				  num_stripes, cur_offset);
			ret = -EIO;
			break;
		}

		type = btrfs_chunk_type(sb, chunk);
		if ((type & BTRFS_BLOCK_GROUP_SYSTEM) == 0) {
			btrfs_err(fs_info,
			"invalid chunk type %llu in sys_array at offset %u",
				  type, cur_offset);
			ret = -EIO;
			break;
		}

		len = btrfs_chunk_item_size(num_stripes);
		if (cur_offset + len > array_size)
			goto out_short_read;

		ret = read_one_chunk(&key, sb, chunk);
		if (ret)
			break;

		array_ptr += len;
		sb_array_offset += len;
		cur_offset += len;
	}
	clear_extent_buffer_uptodate(sb);
	free_extent_buffer_stale(sb);
	return ret;

out_short_read:
	btrfs_err(fs_info, "sys_array too short to read %u bytes at offset %u",
			len, cur_offset);
	clear_extent_buffer_uptodate(sb);
	free_extent_buffer_stale(sb);
	return -EIO;
}


static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
			struct btrfs_device *device, fmode_t flags,
			void *holder)
{
	struct request_queue *q;
	struct block_device *bdev;
	struct btrfs_super_block *disk_super;
	u64 devid;
	int ret;

	if (device->bdev)
		return -EINVAL;
	if (!device->name)
		return -EINVAL;

	ret = btrfs_get_bdev_and_sb(device->name->str, flags, holder, 1,
				    &bdev, &disk_super);
	if (ret)
		return ret;

	devid = btrfs_stack_device_id(&disk_super->dev_item);
	if (devid != device->devid)
		goto error_free_page;

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

	device->generation = btrfs_super_generation(disk_super);

	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
		if (btrfs_super_incompat_flags(disk_super) &
		    BTRFS_FEATURE_INCOMPAT_METADATA_UUID) {
			pr_err(
		"BTRFS: Invalid seeding and uuid-changed device detected\n");
			goto error_free_page;
		}

		clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
		fs_devices->seeding = true;
	} else {
		if (bdev_read_only(bdev))
			clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
		else
			set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
	}

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

	device->bdev = bdev;
	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
	device->mode = flags;

	fs_devices->open_devices++;
	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
		fs_devices->rw_devices++;
		list_add_tail(&device->dev_alloc_list, &fs_devices->alloc_list);
	}
	btrfs_release_disk_super(disk_super);

	return 0;

error_free_page:
	btrfs_release_disk_super(disk_super);
	blkdev_put(bdev, flags);

	return -EINVAL;
}


static void close_fs_devices(struct btrfs_fs_devices *fs_devices)
{
	struct btrfs_device *device, *tmp;

	lockdep_assert_held(&uuid_mutex);

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

	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list)
		btrfs_close_one_device(device);

	WARN_ON(fs_devices->open_devices);
	WARN_ON(fs_devices->rw_devices);
	fs_devices->opened = 0;
	fs_devices->seeding = false;
	fs_devices->fs_info = NULL;
}


static int chunk_profiles_filter(u64 chunk_type,
				 struct btrfs_balance_args *bargs)
{
	chunk_type = chunk_to_extended(chunk_type) &
				BTRFS_EXTENDED_PROFILE_MASK;

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

	return 1;
}


static int btrfs_add_dev_item(struct btrfs_trans_handle *trans,
			    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;

	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, trans->fs_info->chunk_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,
				     btrfs_device_get_disk_total_bytes(device));
	btrfs_set_device_bytes_used(leaf, dev_item,
				    btrfs_device_get_bytes_used(device));
	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 = btrfs_device_uuid(dev_item);
	write_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
	ptr = btrfs_device_fsid(dev_item);
	write_extent_buffer(leaf, trans->fs_info->fs_devices->metadata_uuid,
			    ptr, BTRFS_FSID_SIZE);
	btrfs_mark_buffer_dirty(leaf);

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


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 btrfs_free_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_root *root = fs_info->chunk_root;
	int ret;
	struct btrfs_path *path;
	struct btrfs_key key;

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

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

	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret < 0)
		goto out;
	else if (ret > 0) { /* Logic error or corruption */
		btrfs_handle_fs_error(fs_info, -ENOENT,
				      "Failed lookup while freeing chunk.");
		ret = -ENOENT;
		goto out;
	}

	ret = btrfs_del_item(trans, root, path);
	if (ret < 0)
		btrfs_handle_fs_error(fs_info, ret,
				      "Failed to delete chunk item.");
out:
	btrfs_free_path(path);
	return ret;
}


static bool device_path_matched(const char *path, struct btrfs_device *device)
{
	int found;

	rcu_read_lock();
	found = strcmp(rcu_str_deref(device->name), path);
	rcu_read_unlock();

	return found == 0;
}


static void btrfs_close_bdev(struct btrfs_device *device)
{
	if (!device->bdev)
		return;

	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
		sync_blockdev(device->bdev);
		invalidate_bdev(device->bdev);
	}

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


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;
	}

	/*
	 * A paused balance with the item stored on disk can be resumed at
	 * mount time if the mount is read-write. Otherwise it's still paused
	 * and we must not allow cancelling as it deletes the item.
	 */
	if (sb_rdonly(fs_info->sb)) {
		mutex_unlock(&fs_info->balance_mutex);
		return -EROFS;
	}

	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 (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
		mutex_unlock(&fs_info->balance_mutex);
		wait_event(fs_info->balance_wait_q,
			   !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
		mutex_lock(&fs_info->balance_mutex);
	} else {
		mutex_unlock(&fs_info->balance_mutex);
		/*
		 * Lock released to allow other waiters to continue, we'll
		 * reexamine the status again.
		 */
		mutex_lock(&fs_info->balance_mutex);

		if (fs_info->balance_ctl) {
			reset_balance_state(fs_info);
			btrfs_exclop_finish(fs_info);
			btrfs_info(fs_info, "balance: canceled");
		}
	}

	BUG_ON(fs_info->balance_ctl ||
		test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
	atomic_dec(&fs_info->balance_cancel_req);
	mutex_unlock(&fs_info->balance_mutex);
	return 0;
}


static u64 dev_extent_search_start(struct btrfs_device *device, u64 start)
{
	switch (device->fs_devices->chunk_alloc_policy) {
	case BTRFS_CHUNK_ALLOC_REGULAR:
		/*
		 * We don't want to overwrite the superblock on the drive nor
		 * any area used by the boot loader (grub for example), so we
		 * make sure to start at an offset of at least 1MB.
		 */
		return max_t(u64, start, SZ_1M);
	case BTRFS_CHUNK_ALLOC_ZONED:
		/*
		 * We don't care about the starting region like regular
		 * allocator, because we anyway use/reserve the first two zones
		 * for superblock logging.
		 */
		return ALIGN(start, device->zone_info->zone_size);
	default:
		BUG();
	}
}


struct list_head * __attribute_const__ btrfs_get_fs_uuids(void)
{
	return &fs_uuids;
}


static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
					 u64 logical, u64 *length_ret,
					 struct btrfs_bio **bbio_ret)
{
	struct extent_map *em;
	struct map_lookup *map;
	struct btrfs_bio *bbio;
	u64 length = *length_ret;
	u64 offset;
	u64 stripe_nr;
	u64 stripe_nr_end;
	u64 stripe_end_offset;
	u64 stripe_cnt;
	u64 stripe_len;
	u64 stripe_offset;
	u64 num_stripes;
	u32 stripe_index;
	u32 factor = 0;
	u32 sub_stripes = 0;
	u64 stripes_per_dev = 0;
	u32 remaining_stripes = 0;
	u32 last_stripe = 0;
	int ret = 0;
	int i;

	/* discard always return a bbio */
	ASSERT(bbio_ret);

	em = btrfs_get_chunk_map(fs_info, logical, length);
	if (IS_ERR(em))
		return PTR_ERR(em);

	map = em->map_lookup;
	/* we don't discard raid56 yet */
	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
		ret = -EOPNOTSUPP;
		goto out;
	}

	offset = logical - em->start;
	length = min_t(u64, em->start + em->len - logical, length);
	*length_ret = length;

	stripe_len = map->stripe_len;
	/*
	 * stripe_nr counts the total number of stripes we have to stride
	 * to get to this block
	 */
	stripe_nr = div64_u64(offset, stripe_len);

	/* stripe_offset is the offset of this block in its stripe */
	stripe_offset = offset - stripe_nr * stripe_len;

	stripe_nr_end = round_up(offset + length, map->stripe_len);
	stripe_nr_end = div64_u64(stripe_nr_end, map->stripe_len);
	stripe_cnt = stripe_nr_end - stripe_nr;
	stripe_end_offset = stripe_nr_end * map->stripe_len -
			    (offset + length);
	/*
	 * after this, stripe_nr is the number of stripes on this
	 * device we have to walk to find the data, and stripe_index is
	 * the number of our device in the stripe array
	 */
	num_stripes = 1;
	stripe_index = 0;
	if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
			 BTRFS_BLOCK_GROUP_RAID10)) {
		if (map->type & BTRFS_BLOCK_GROUP_RAID0)
			sub_stripes = 1;
		else
			sub_stripes = map->sub_stripes;

		factor = map->num_stripes / sub_stripes;
		num_stripes = min_t(u64, map->num_stripes,
				    sub_stripes * stripe_cnt);
		stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
		stripe_index *= sub_stripes;
		stripes_per_dev = div_u64_rem(stripe_cnt, factor,
					      &remaining_stripes);
		div_u64_rem(stripe_nr_end - 1, factor, &last_stripe);
		last_stripe *= sub_stripes;
	} else if (map->type & (BTRFS_BLOCK_GROUP_RAID1_MASK |
				BTRFS_BLOCK_GROUP_DUP)) {
		num_stripes = map->num_stripes;
	} else {
		stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
					&stripe_index);
	}

	bbio = alloc_btrfs_bio(num_stripes, 0);
	if (!bbio) {
		ret = -ENOMEM;
		goto out;
	}

	for (i = 0; i < num_stripes; i++) {
		bbio->stripes[i].physical =
			map->stripes[stripe_index].physical +
			stripe_offset + stripe_nr * map->stripe_len;
		bbio->stripes[i].dev = map->stripes[stripe_index].dev;

		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
				 BTRFS_BLOCK_GROUP_RAID10)) {
			bbio->stripes[i].length = stripes_per_dev *
				map->stripe_len;

			if (i / sub_stripes < remaining_stripes)
				bbio->stripes[i].length +=
					map->stripe_len;

			/*
			 * Special for the first stripe and
			 * the last stripe:
			 *
			 * |-------|...|-------|
			 *     |----------|
			 *    off     end_off
			 */
			if (i < sub_stripes)
				bbio->stripes[i].length -=
					stripe_offset;

			if (stripe_index >= last_stripe &&
			    stripe_index <= (last_stripe +
					     sub_stripes - 1))
				bbio->stripes[i].length -=
					stripe_end_offset;

			if (i == sub_stripes - 1)
				stripe_offset = 0;
		} else {
			bbio->stripes[i].length = length;
		}

		stripe_index++;
		if (stripe_index == map->num_stripes) {
			stripe_index = 0;
			stripe_nr++;
		}
	}

	*bbio_ret = bbio;
	bbio->map_type = map->type;
	bbio->num_stripes = num_stripes;
out:
	free_extent_map(em);
	return ret;
}


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

	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
	chunk_used = cache->used;

	if (bargs->usage_min == 0)
		user_thresh = 1;
	else if (bargs->usage > 100)
		user_thresh = cache->length;
	else
		user_thresh = div_factor_fine(cache->length, bargs->usage);

	if (chunk_used < user_thresh)
		ret = 0;

	btrfs_put_block_group(cache);
	return ret;
}


int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path)
{
	struct btrfs_root *root = fs_info->dev_root;
	struct request_queue *q;
	struct btrfs_trans_handle *trans;
	struct btrfs_device *device;
	struct block_device *bdev;
	struct super_block *sb = fs_info->sb;
	struct rcu_string *name;
	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
	u64 orig_super_total_bytes;
	u64 orig_super_num_devices;
	int seeding_dev = 0;
	int ret = 0;
	bool locked = false;

	if (sb_rdonly(sb) && !fs_devices->seeding)
		return -EROFS;

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

	if (!btrfs_check_device_zone_type(fs_info, bdev)) {
		ret = -EINVAL;
		goto error;
	}

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

	sync_blockdev(bdev);

	rcu_read_lock();
	list_for_each_entry_rcu(device, &fs_devices->devices, dev_list) {
		if (device->bdev == bdev) {
			ret = -EEXIST;
			rcu_read_unlock();
			goto error;
		}
	}
	rcu_read_unlock();

	device = btrfs_alloc_device(fs_info, NULL, NULL);
	if (IS_ERR(device)) {
		/* we can safely leave the fs_devices entry around */
		ret = PTR_ERR(device);
		goto error;
	}

	name = rcu_string_strdup(device_path, GFP_KERNEL);
	if (!name) {
		ret = -ENOMEM;
		goto error_free_device;
	}
	rcu_assign_pointer(device->name, name);

	device->fs_info = fs_info;
	device->bdev = bdev;

	ret = btrfs_get_dev_zone_info(device);
	if (ret)
		goto error_free_device;

	trans = btrfs_start_transaction(root, 0);
	if (IS_ERR(trans)) {
		ret = PTR_ERR(trans);
		goto error_free_zone;
	}

	q = bdev_get_queue(bdev);
	set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
	device->generation = trans->transid;
	device->io_width = fs_info->sectorsize;
	device->io_align = fs_info->sectorsize;
	device->sector_size = fs_info->sectorsize;
	device->total_bytes = round_down(i_size_read(bdev->bd_inode),
					 fs_info->sectorsize);
	device->disk_total_bytes = device->total_bytes;
	device->commit_total_bytes = device->total_bytes;
	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
	device->mode = FMODE_EXCL;
	device->dev_stats_valid = 1;
	set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);

	if (seeding_dev) {
		btrfs_clear_sb_rdonly(sb);
		ret = btrfs_prepare_sprout(fs_info);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto error_trans;
		}
	}

	device->fs_devices = fs_devices;

	mutex_lock(&fs_devices->device_list_mutex);
	mutex_lock(&fs_info->chunk_mutex);
	list_add_rcu(&device->dev_list, &fs_devices->devices);
	list_add(&device->dev_alloc_list, &fs_devices->alloc_list);
	fs_devices->num_devices++;
	fs_devices->open_devices++;
	fs_devices->rw_devices++;
	fs_devices->total_devices++;
	fs_devices->total_rw_bytes += device->total_bytes;

	atomic64_add(device->total_bytes, &fs_info->free_chunk_space);

	if (!blk_queue_nonrot(q))
		fs_devices->rotating = true;

	orig_super_total_bytes = btrfs_super_total_bytes(fs_info->super_copy);
	btrfs_set_super_total_bytes(fs_info->super_copy,
		round_down(orig_super_total_bytes + device->total_bytes,
			   fs_info->sectorsize));

	orig_super_num_devices = btrfs_super_num_devices(fs_info->super_copy);
	btrfs_set_super_num_devices(fs_info->super_copy,
				    orig_super_num_devices + 1);

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

	mutex_unlock(&fs_info->chunk_mutex);

	/* Add sysfs device entry */
	btrfs_sysfs_add_device(device);

	mutex_unlock(&fs_devices->device_list_mutex);

	if (seeding_dev) {
		mutex_lock(&fs_info->chunk_mutex);
		ret = init_first_rw_device(trans);
		mutex_unlock(&fs_info->chunk_mutex);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto error_sysfs;
		}
	}

	ret = btrfs_add_dev_item(trans, device);
	if (ret) {
		btrfs_abort_transaction(trans, ret);
		goto error_sysfs;
	}

	if (seeding_dev) {
		ret = btrfs_finish_sprout(trans);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto error_sysfs;
		}

		/*
		 * fs_devices now represents the newly sprouted filesystem and
		 * its fsid has been changed by btrfs_prepare_sprout
		 */
		btrfs_sysfs_update_sprout_fsid(fs_devices);
	}

	ret = btrfs_commit_transaction(trans);

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

		if (ret) /* transaction commit */
			return ret;

		ret = btrfs_relocate_sys_chunks(fs_info);
		if (ret < 0)
			btrfs_handle_fs_error(fs_info, ret,
				    "Failed to relocate sys chunks after device initialization. This can be fixed using the \"btrfs balance\" command.");
		trans = btrfs_attach_transaction(root);
		if (IS_ERR(trans)) {
			if (PTR_ERR(trans) == -ENOENT)
				return 0;
			ret = PTR_ERR(trans);
			trans = NULL;
			goto error_sysfs;
		}
		ret = btrfs_commit_transaction(trans);
	}

	/*
	 * Now that we have written a new super block to this device, check all
	 * other fs_devices list if device_path alienates any other scanned
	 * device.
	 * We can ignore the return value as it typically returns -EINVAL and
	 * only succeeds if the device was an alien.
	 */
	btrfs_forget_devices(device_path);

	/* Update ctime/mtime for blkid or udev */
	update_dev_time(device_path);

	return ret;

error_sysfs:
	btrfs_sysfs_remove_device(device);
	mutex_lock(&fs_info->fs_devices->device_list_mutex);
	mutex_lock(&fs_info->chunk_mutex);
	list_del_rcu(&device->dev_list);
	list_del(&device->dev_alloc_list);
	fs_info->fs_devices->num_devices--;
	fs_info->fs_devices->open_devices--;
	fs_info->fs_devices->rw_devices--;
	fs_info->fs_devices->total_devices--;
	fs_info->fs_devices->total_rw_bytes -= device->total_bytes;
	atomic64_sub(device->total_bytes, &fs_info->free_chunk_space);
	btrfs_set_super_total_bytes(fs_info->super_copy,
				    orig_super_total_bytes);
	btrfs_set_super_num_devices(fs_info->super_copy,
				    orig_super_num_devices);
	mutex_unlock(&fs_info->chunk_mutex);
	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
error_trans:
	if (seeding_dev)
		btrfs_set_sb_rdonly(sb);
	if (trans)
		btrfs_end_transaction(trans);
error_free_zone:
	btrfs_destroy_dev_zone_info(device);
error_free_device:
	btrfs_free_device(device);
error:
	blkdev_put(bdev, FMODE_EXCL);
	if (locked) {
		mutex_unlock(&uuid_mutex);
		up_write(&sb->s_umount);
	}
	return ret;
}


static bool contains_pending_extent(struct btrfs_device *device, u64 *start,
				    u64 len)
{
	u64 physical_start, physical_end;

	lockdep_assert_held(&device->fs_info->chunk_mutex);

	if (!find_first_extent_bit(&device->alloc_state, *start,
				   &physical_start, &physical_end,
				   CHUNK_ALLOCATED, NULL)) {

		if (in_range(physical_start, *start, len) ||
		    in_range(*start, physical_start,
			     physical_end - physical_start)) {
			*start = physical_end + 1;
			return true;
		}
	}
	return false;
}


static void __btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices,
				      struct btrfs_device **latest_dev)
{
	struct btrfs_device *device, *next;

	/* 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 (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state)) {
			if (!test_bit(BTRFS_DEV_STATE_REPLACE_TGT,
				      &device->dev_state) &&
			    !test_bit(BTRFS_DEV_STATE_MISSING,
				      &device->dev_state) &&
			    (!*latest_dev ||
			     device->generation > (*latest_dev)->generation)) {
				*latest_dev = device;
			}
			continue;
		}

		/*
		 * We have already validated the presence of BTRFS_DEV_REPLACE_DEVID,
		 * in btrfs_init_dev_replace() so just continue.
		 */
		if (device->devid == BTRFS_DEV_REPLACE_DEVID)
			continue;

		if (device->bdev) {
			blkdev_put(device->bdev, device->mode);
			device->bdev = NULL;
			fs_devices->open_devices--;
		}
		if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
			list_del_init(&device->dev_alloc_list);
			clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
			fs_devices->rw_devices--;
		}
		list_del_init(&device->dev_list);
		fs_devices->num_devices--;
		btrfs_free_device(device);
	}

}


int btrfs_run_dev_stats(struct btrfs_trans_handle *trans)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
	struct btrfs_device *device;
	int stats_cnt;
	int ret = 0;

	mutex_lock(&fs_devices->device_list_mutex);
	list_for_each_entry(device, &fs_devices->devices, dev_list) {
		stats_cnt = atomic_read(&device->dev_stats_ccnt);
		if (!device->dev_stats_valid || stats_cnt == 0)
			continue;

		/*
		 * There is a LOAD-LOAD control dependency between the value of
		 * dev_stats_ccnt and updating the on-disk values which requires
		 * reading the in-memory counters. Such control dependencies
		 * require explicit read memory barriers.
		 *
		 * This memory barriers pairs with smp_mb__before_atomic in
		 * btrfs_dev_stat_inc/btrfs_dev_stat_set and with the full
		 * barrier implied by atomic_xchg in
		 * btrfs_dev_stats_read_and_reset
		 */
		smp_rmb();

		ret = update_dev_stat_item(trans, device);
		if (!ret)
			atomic_sub(stats_cnt, &device->dev_stats_ccnt);
	}
	mutex_unlock(&fs_devices->device_list_mutex);

	return ret;
}


int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
{
	struct btrfs_fs_info *fs_info = device->fs_info;
	struct btrfs_root *root = fs_info->dev_root;
	struct btrfs_trans_handle *trans;
	struct btrfs_dev_extent *dev_extent = NULL;
	struct btrfs_path *path;
	u64 length;
	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 = fs_info->super_copy;
	u64 old_total = btrfs_super_total_bytes(super_copy);
	u64 old_size = btrfs_device_get_total_bytes(device);
	u64 diff;
	u64 start;

	new_size = round_down(new_size, fs_info->sectorsize);
	start = new_size;
	diff = round_down(old_size - new_size, fs_info->sectorsize);

	if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
		return -EINVAL;

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

	path->reada = READA_BACK;

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

	mutex_lock(&fs_info->chunk_mutex);

	btrfs_device_set_total_bytes(device, new_size);
	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
		device->fs_devices->total_rw_bytes -= diff;
		atomic64_sub(diff, &fs_info->free_chunk_space);
	}

	/*
	 * Once the device's size has been set to the new size, ensure all
	 * in-memory chunks are synced to disk so that the loop below sees them
	 * and relocates them accordingly.
	 */
	if (contains_pending_extent(device, &start, diff)) {
		mutex_unlock(&fs_info->chunk_mutex);
		ret = btrfs_commit_transaction(trans);
		if (ret)
			goto done;
	} else {
		mutex_unlock(&fs_info->chunk_mutex);
		btrfs_end_transaction(trans);
	}

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

	do {
		mutex_lock(&fs_info->reclaim_bgs_lock);
		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
		if (ret < 0) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			goto done;
		}

		ret = btrfs_previous_item(root, path, 0, key.type);
		if (ret) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			if (ret < 0)
				goto done;
			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) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			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) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			btrfs_release_path(path);
			break;
		}

		chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
		btrfs_release_path(path);

		/*
		 * We may be relocating the only data chunk we have,
		 * which could potentially end up with losing data's
		 * raid profile, so lets allocate an empty one in
		 * advance.
		 */
		ret = btrfs_may_alloc_data_chunk(fs_info, chunk_offset);
		if (ret < 0) {
			mutex_unlock(&fs_info->reclaim_bgs_lock);
			goto done;
		}

		ret = btrfs_relocate_chunk(fs_info, chunk_offset);
		mutex_unlock(&fs_info->reclaim_bgs_lock);
		if (ret == -ENOSPC) {
			failed++;
		} else if (ret) {
			if (ret == -ETXTBSY) {
				btrfs_warn(fs_info,
		   "could not shrink block group %llu due to active swapfile",
					   chunk_offset);
			}
			goto done;
		}
	} while (key.offset-- > 0);

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

	mutex_lock(&fs_info->chunk_mutex);
	/* Clear all state bits beyond the shrunk device size */
	clear_extent_bits(&device->alloc_state, new_size, (u64)-1,
			  CHUNK_STATE_MASK);

	btrfs_device_set_disk_total_bytes(device, new_size);
	if (list_empty(&device->post_commit_list))
		list_add_tail(&device->post_commit_list,
			      &trans->transaction->dev_update_list);

	WARN_ON(diff > old_total);
	btrfs_set_super_total_bytes(super_copy,
			round_down(old_total - diff, fs_info->sectorsize));
	mutex_unlock(&fs_info->chunk_mutex);

	/* Now btrfs_update_device() will change the on-disk size. */
	ret = btrfs_update_device(trans, device);
	if (ret < 0) {
		btrfs_abort_transaction(trans, ret);
		btrfs_end_transaction(trans);
	} else {
		ret = btrfs_commit_transaction(trans);
	}
done:
	btrfs_free_path(path);
	if (ret) {
		mutex_lock(&fs_info->chunk_mutex);
		btrfs_device_set_total_bytes(device, old_size);
		if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
			device->fs_devices->total_rw_bytes += diff;
		atomic64_add(diff, &fs_info->free_chunk_space);
		mutex_unlock(&fs_info->chunk_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);
}


int btrfs_chunk_readonly(struct btrfs_fs_info *fs_info, u64 chunk_offset)
{
	struct extent_map *em;
	struct map_lookup *map;
	int readonly = 0;
	int miss_ndevs = 0;
	int i;

	em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
	if (IS_ERR(em))
		return 1;

	map = em->map_lookup;
	for (i = 0; i < map->num_stripes; i++) {
		if (test_bit(BTRFS_DEV_STATE_MISSING,
					&map->stripes[i].dev->dev_state)) {
			miss_ndevs++;
			continue;
		}
		if (!test_bit(BTRFS_DEV_STATE_WRITEABLE,
					&map->stripes[i].dev->dev_state)) {
			readonly = 1;
			goto end;
		}
	}

	/*
	 * If the number of missing devices is larger than max errors,
	 * we can not write the data into that chunk successfully, so
	 * set it readonly.
	 */
	if (miss_ndevs > btrfs_chunk_max_errors(map))
		readonly = 1;
end:
	free_extent_map(em);
	return readonly;
}


void btrfs_put_bbio(struct btrfs_bio *bbio)
{
	if (!bbio)
		return;
	if (refcount_dec_and_test(&bbio->refs))
		kfree(bbio);
}


int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
{
	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices, *seed_devs;
	struct btrfs_device *device;
	struct btrfs_path *path = NULL;
	int ret = 0;

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

	mutex_lock(&fs_devices->device_list_mutex);
	list_for_each_entry(device, &fs_devices->devices, dev_list) {
		ret = btrfs_device_init_dev_stats(device, path);
		if (ret)
			goto out;
	}
	list_for_each_entry(seed_devs, &fs_devices->seed_list, seed_list) {
		list_for_each_entry(device, &seed_devs->devices, dev_list) {
			ret = btrfs_device_init_dev_stats(device, path);
			if (ret)
				goto out;
		}
	}
out:
	mutex_unlock(&fs_devices->device_list_mutex);

	btrfs_free_path(path);
	return ret;
}


static int btrfs_finish_sprout(struct btrfs_trans_handle *trans)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_root *root = fs_info->chunk_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_FSID_SIZE];
	u8 dev_uuid[BTRFS_UUID_SIZE];
	u64 devid;
	int ret;

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

	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, btrfs_device_uuid(dev_item),
				   BTRFS_UUID_SIZE);
		read_extent_buffer(leaf, fs_uuid, btrfs_device_fsid(dev_item),
				   BTRFS_FSID_SIZE);
		device = btrfs_find_device(fs_info->fs_devices, devid, dev_uuid,
					   fs_uuid);
		BUG_ON(!device); /* Logic error */

		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;
}


static int btrfs_check_raid_min_devices(struct btrfs_fs_info *fs_info,
		u64 num_devices)
{
	u64 all_avail;
	unsigned seq;
	int i;

	do {
		seq = read_seqbegin(&fs_info->profiles_lock);

		all_avail = fs_info->avail_data_alloc_bits |
			    fs_info->avail_system_alloc_bits |
			    fs_info->avail_metadata_alloc_bits;
	} while (read_seqretry(&fs_info->profiles_lock, seq));

	for (i = 0; i < BTRFS_NR_RAID_TYPES; i++) {
		if (!(all_avail & btrfs_raid_array[i].bg_flag))
			continue;

		if (num_devices < btrfs_raid_array[i].devs_min)
			return btrfs_raid_array[i].mindev_error;
	}

	return 0;
}


void btrfs_describe_block_groups(u64 bg_flags, char *buf, u32 size_buf)
{
	int i;
	int ret;
	char *bp = buf;
	u64 flags = bg_flags;
	u32 size_bp = size_buf;

	if (!flags) {
		strcpy(bp, "NONE");
		return;
	}

#define DESCRIBE_FLAG(flag, desc)						\
	do {								\
		if (flags & (flag)) {					\
			ret = snprintf(bp, size_bp, "%s|", (desc));	\
			if (ret < 0 || ret >= size_bp)			\
				goto out_overflow;			\
			size_bp -= ret;					\
			bp += ret;					\
			flags &= ~(flag);				\
		}							\
	} while (0)

	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_DATA, "data");
	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_SYSTEM, "system");
	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_METADATA, "metadata");

	DESCRIBE_FLAG(BTRFS_AVAIL_ALLOC_BIT_SINGLE, "single");
	for (i = 0; i < BTRFS_NR_RAID_TYPES; i++)
		DESCRIBE_FLAG(btrfs_raid_array[i].bg_flag,
			      btrfs_raid_array[i].raid_name);
#undef DESCRIBE_FLAG

	if (flags) {
		ret = snprintf(bp, size_bp, "0x%llx|", flags);
		size_bp -= ret;
	}

	if (size_bp < size_buf)
		buf[size_buf - size_bp - 1] = '\0'; /* remove last | */

	/*
	 * The text is trimmed, it's up to the caller to provide sufficiently
	 * large buffer
	 */
out_overflow:;
}


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;
}


static void init_alloc_chunk_ctl_policy_regular(
				struct btrfs_fs_devices *fs_devices,
				struct alloc_chunk_ctl *ctl)
{
	u64 type = ctl->type;

	if (type & BTRFS_BLOCK_GROUP_DATA) {
		ctl->max_stripe_size = SZ_1G;
		ctl->max_chunk_size = BTRFS_MAX_DATA_CHUNK_SIZE;
	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
		/* For larger filesystems, use larger metadata chunks */
		if (fs_devices->total_rw_bytes > 50ULL * SZ_1G)
			ctl->max_stripe_size = SZ_1G;
		else
			ctl->max_stripe_size = SZ_256M;
		ctl->max_chunk_size = ctl->max_stripe_size;
	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
		ctl->max_stripe_size = SZ_32M;
		ctl->max_chunk_size = 2 * ctl->max_stripe_size;
		ctl->devs_max = min_t(int, ctl->devs_max,
				      BTRFS_MAX_DEVS_SYS_CHUNK);
	} else {
		BUG();
	}

	/* We don't want a chunk larger than 10% of writable space */
	ctl->max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
				  ctl->max_chunk_size);
	ctl->dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
}


void btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
{
	LIST_HEAD(list);
	struct btrfs_fs_devices *tmp;

	mutex_lock(&uuid_mutex);
	close_fs_devices(fs_devices);
	if (!fs_devices->opened)
		list_splice_init(&fs_devices->seed_list, &list);

	list_for_each_entry_safe(fs_devices, tmp, &list, seed_list) {
		close_fs_devices(fs_devices);
		list_del(&fs_devices->seed_list);
		free_fs_devices(fs_devices);
	}
	mutex_unlock(&uuid_mutex);
}


int btrfs_grow_device(struct btrfs_trans_handle *trans,
		      struct btrfs_device *device, u64 new_size)
{
	struct btrfs_fs_info *fs_info = device->fs_info;
	struct btrfs_super_block *super_copy = fs_info->super_copy;
	u64 old_total;
	u64 diff;

	if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
		return -EACCES;

	new_size = round_down(new_size, fs_info->sectorsize);

	mutex_lock(&fs_info->chunk_mutex);
	old_total = btrfs_super_total_bytes(super_copy);
	diff = round_down(new_size - device->total_bytes, fs_info->sectorsize);

	if (new_size <= device->total_bytes ||
	    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
		mutex_unlock(&fs_info->chunk_mutex);
		return -EINVAL;
	}

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

	btrfs_device_set_total_bytes(device, new_size);
	btrfs_device_set_disk_total_bytes(device, new_size);
	btrfs_clear_space_info_full(device->fs_info);
	if (list_empty(&device->post_commit_list))
		list_add_tail(&device->post_commit_list,
			      &trans->transaction->dev_update_list);
	mutex_unlock(&fs_info->chunk_mutex);

	return btrfs_update_device(trans, device);
}


static int btrfs_free_dev_extent(struct btrfs_trans_handle *trans,
			  struct btrfs_device *device,
			  u64 start, u64 *dev_extent_len)
{
	struct btrfs_fs_info *fs_info = device->fs_info;
	struct btrfs_root *root = fs_info->dev_root;
	int ret;
	struct btrfs_path *path;
	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);
	} else {
		goto out;
	}

	*dev_extent_len = btrfs_dev_extent_length(leaf, extent);

	ret = btrfs_del_item(trans, root, path);
	if (ret == 0)
		set_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags);
out:
	btrfs_free_path(path);
	return ret;
}


static int insert_balance_item(struct btrfs_fs_info *fs_info,
			       struct btrfs_balance_control *bctl)
{
	struct btrfs_root *root = fs_info->tree_root;
	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_TEMPORARY_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);

	memzero_extent_buffer(leaf, (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);
	if (err && !ret)
		ret = err;
	return ret;
}


static struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,
						       u64 bytenr, u64 bytenr_orig)
{
	struct btrfs_super_block *disk_super;
	struct page *page;
	void *p;
	pgoff_t index;

	/* make sure our super fits in the device */
	if (bytenr + PAGE_SIZE >= i_size_read(bdev->bd_inode))
		return ERR_PTR(-EINVAL);

	/* make sure our super fits in the page */
	if (sizeof(*disk_super) > PAGE_SIZE)
		return ERR_PTR(-EINVAL);

	/* make sure our super doesn't straddle pages on disk */
	index = bytenr >> PAGE_SHIFT;
	if ((bytenr + sizeof(*disk_super) - 1) >> PAGE_SHIFT != index)
		return ERR_PTR(-EINVAL);

	/* pull in the page with our super */
	page = read_cache_page_gfp(bdev->bd_inode->i_mapping, index, GFP_KERNEL);

	if (IS_ERR(page))
		return ERR_CAST(page);

	p = page_address(page);

	/* align our pointer to the offset of the super block */
	disk_super = p + offset_in_page(bytenr);

	if (btrfs_super_bytenr(disk_super) != bytenr_orig ||
	    btrfs_super_magic(disk_super) != BTRFS_MAGIC) {
		btrfs_release_disk_super(p);
		return ERR_PTR(-EINVAL);
	}

	if (disk_super->label[0] && disk_super->label[BTRFS_LABEL_SIZE - 1])
		disk_super->label[BTRFS_LABEL_SIZE - 1] = 0;

	return disk_super;
}


struct btrfs_block_group *btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
					    u64 type)
{
	struct btrfs_fs_info *info = trans->fs_info;
	struct btrfs_fs_devices *fs_devices = info->fs_devices;
	struct btrfs_device_info *devices_info = NULL;
	struct alloc_chunk_ctl ctl;
	struct btrfs_block_group *block_group;
	int ret;

	lockdep_assert_held(&info->chunk_mutex);

	if (!alloc_profile_is_valid(type, 0)) {
		ASSERT(0);
		return ERR_PTR(-EINVAL);
	}

	if (list_empty(&fs_devices->alloc_list)) {
		if (btrfs_test_opt(info, ENOSPC_DEBUG))
			btrfs_debug(info, "%s: no writable device", __func__);
		return ERR_PTR(-ENOSPC);
	}

	if (!(type & BTRFS_BLOCK_GROUP_TYPE_MASK)) {
		btrfs_err(info, "invalid chunk type 0x%llx requested", type);
		ASSERT(0);
		return ERR_PTR(-EINVAL);
	}

	ctl.start = find_next_chunk(info);
	ctl.type = type;
	init_alloc_chunk_ctl(fs_devices, &ctl);

	devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
			       GFP_NOFS);
	if (!devices_info)
		return ERR_PTR(-ENOMEM);

	ret = gather_device_info(fs_devices, &ctl, devices_info);
	if (ret < 0) {
		block_group = ERR_PTR(ret);
		goto out;
	}

	ret = decide_stripe_size(fs_devices, &ctl, devices_info);
	if (ret < 0) {
		block_group = ERR_PTR(ret);
		goto out;
	}

	block_group = create_chunk(trans, &ctl, devices_info);

out:
	kfree(devices_info);
	return block_group;
}


struct btrfs_device *btrfs_scan_one_device(const char *path, fmode_t flags,
					   void *holder)
{
	struct btrfs_super_block *disk_super;
	bool new_device_added = false;
	struct btrfs_device *device = NULL;
	struct block_device *bdev;
	u64 bytenr, bytenr_orig;
	int ret;

	lockdep_assert_held(&uuid_mutex);

	/*
	 * we would like to check all the supers, but that would make
	 * a btrfs mount succeed after a mkfs from a different FS.
	 * So, we need to add a special mount option to scan for
	 * later supers, using BTRFS_SUPER_MIRROR_MAX instead
	 */
	flags |= FMODE_EXCL;

	bdev = blkdev_get_by_path(path, flags, holder);
	if (IS_ERR(bdev))
		return ERR_CAST(bdev);

	bytenr_orig = btrfs_sb_offset(0);
	ret = btrfs_sb_log_location_bdev(bdev, 0, READ, &bytenr);
	if (ret)
		return ERR_PTR(ret);

	disk_super = btrfs_read_disk_super(bdev, bytenr, bytenr_orig);
	if (IS_ERR(disk_super)) {
		device = ERR_CAST(disk_super);
		goto error_bdev_put;
	}

	device = device_list_add(path, disk_super, &new_device_added);
	if (!IS_ERR(device)) {
		if (new_device_added)
			btrfs_free_stale_devices(path, device);
	}

	btrfs_release_disk_super(disk_super);

error_bdev_put:
	blkdev_put(bdev, flags);

	return device;
}


static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,
				  u64 *hole_size, u64 num_bytes)
{
	bool changed = false;
	u64 hole_end = *hole_start + *hole_size;

	for (;;) {
		/*
		 * Check before we set max_hole_start, otherwise we could end up
		 * sending back this offset anyway.
		 */
		if (contains_pending_extent(device, hole_start, *hole_size)) {
			if (hole_end >= *hole_start)
				*hole_size = hole_end - *hole_start;
			else
				*hole_size = 0;
			changed = true;
		}

		switch (device->fs_devices->chunk_alloc_policy) {
		case BTRFS_CHUNK_ALLOC_REGULAR:
			/* No extra check */
			break;
		case BTRFS_CHUNK_ALLOC_ZONED:
			if (dev_extent_hole_check_zoned(device, hole_start,
							hole_size, num_bytes)) {
				changed = true;
				/*
				 * The changed hole can contain pending extent.
				 * Loop again to check that.
				 */
				continue;
			}
			break;
		default:
			BUG();
		}

		break;
	}

	return changed;
}


int find_free_dev_extent(struct btrfs_device *device, u64 num_bytes,
			 u64 *start, u64 *len)
{
	/* FIXME use last free of some kind */
	return find_free_dev_extent_start(device, num_bytes, 0, start, len);
}


int btrfs_remove_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct extent_map *em;
	struct map_lookup *map;
	u64 dev_extent_len = 0;
	int i, ret = 0;
	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;

	em = btrfs_get_chunk_map(fs_info, chunk_offset, 1);
	if (IS_ERR(em)) {
		/*
		 * This is a logic error, but we don't want to just rely on the
		 * user having built with ASSERT enabled, so if ASSERT doesn't
		 * do anything we still error out.
		 */
		ASSERT(0);
		return PTR_ERR(em);
	}
	map = em->map_lookup;

	/*
	 * First delete the device extent items from the devices btree.
	 * We take the device_list_mutex to avoid racing with the finishing phase
	 * of a device replace operation. See the comment below before acquiring
	 * fs_info->chunk_mutex. Note that here we do not acquire the chunk_mutex
	 * because that can result in a deadlock when deleting the device extent
	 * items from the devices btree - COWing an extent buffer from the btree
	 * may result in allocating a new metadata chunk, which would attempt to
	 * lock again fs_info->chunk_mutex.
	 */
	mutex_lock(&fs_devices->device_list_mutex);
	for (i = 0; i < map->num_stripes; i++) {
		struct btrfs_device *device = map->stripes[i].dev;
		ret = btrfs_free_dev_extent(trans, device,
					    map->stripes[i].physical,
					    &dev_extent_len);
		if (ret) {
			mutex_unlock(&fs_devices->device_list_mutex);
			btrfs_abort_transaction(trans, ret);
			goto out;
		}

		if (device->bytes_used > 0) {
			mutex_lock(&fs_info->chunk_mutex);
			btrfs_device_set_bytes_used(device,
					device->bytes_used - dev_extent_len);
			atomic64_add(dev_extent_len, &fs_info->free_chunk_space);
			btrfs_clear_space_info_full(fs_info);
			mutex_unlock(&fs_info->chunk_mutex);
		}
	}
	mutex_unlock(&fs_devices->device_list_mutex);

	/*
	 * We acquire fs_info->chunk_mutex for 2 reasons:
	 *
	 * 1) Just like with the first phase of the chunk allocation, we must
	 *    reserve system space, do all chunk btree updates and deletions, and
	 *    update the system chunk array in the superblock while holding this
	 *    mutex. This is for similar reasons as explained on the comment at
	 *    the top of btrfs_chunk_alloc();
	 *
	 * 2) Prevent races with the final phase of a device replace operation
	 *    that replaces the device object associated with the map's stripes,
	 *    because the device object's id can change at any time during that
	 *    final phase of the device replace operation
	 *    (dev-replace.c:btrfs_dev_replace_finishing()), so we could grab the
	 *    replaced device and then see it with an ID of
	 *    BTRFS_DEV_REPLACE_DEVID, which would cause a failure when updating
	 *    the device item, which does not exists on the chunk btree.
	 *    The finishing phase of device replace acquires both the
	 *    device_list_mutex and the chunk_mutex, in that order, so we are
	 *    safe by just acquiring the chunk_mutex.
	 */
	trans->removing_chunk = true;
	mutex_lock(&fs_info->chunk_mutex);

	check_system_chunk(trans, map->type);

	ret = remove_chunk_item(trans, map, chunk_offset);
	/*
	 * Normally we should not get -ENOSPC since we reserved space before
	 * through the call to check_system_chunk().
	 *
	 * Despite our system space_info having enough free space, we may not
	 * be able to allocate extents from its block groups, because all have
	 * an incompatible profile, which will force us to allocate a new system
	 * block group with the right profile, or right after we called
	 * check_system_space() above, a scrub turned the only system block group
	 * with enough free space into RO mode.
	 * This is explained with more detail at do_chunk_alloc().
	 *
	 * So if we get -ENOSPC, allocate a new system chunk and retry once.
	 */
	if (ret == -ENOSPC) {
		const u64 sys_flags = btrfs_system_alloc_profile(fs_info);
		struct btrfs_block_group *sys_bg;

		sys_bg = btrfs_alloc_chunk(trans, sys_flags);
		if (IS_ERR(sys_bg)) {
			ret = PTR_ERR(sys_bg);
			btrfs_abort_transaction(trans, ret);
			goto out;
		}

		ret = btrfs_chunk_alloc_add_chunk_item(trans, sys_bg);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto out;
		}

		ret = remove_chunk_item(trans, map, chunk_offset);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto out;
		}
	} else if (ret) {
		btrfs_abort_transaction(trans, ret);
		goto out;
	}

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

	if (map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
		ret = btrfs_del_sys_chunk(fs_info, chunk_offset);
		if (ret) {
			btrfs_abort_transaction(trans, ret);
			goto out;
		}
	}

	mutex_unlock(&fs_info->chunk_mutex);
	trans->removing_chunk = false;

	/*
	 * We are done with chunk btree updates and deletions, so release the
	 * system space we previously reserved (with check_system_chunk()).
	 */
	btrfs_trans_release_chunk_metadata(trans);

	ret = btrfs_remove_block_group(trans, chunk_offset, em);
	if (ret) {
		btrfs_abort_transaction(trans, ret);
		goto out;
	}

out:
	if (trans->removing_chunk) {
		mutex_unlock(&fs_info->chunk_mutex);
		trans->removing_chunk = false;
	}
	/* once for us */
	free_extent_map(em);
	return ret;
}


static int read_one_dev(struct extent_buffer *leaf,
			struct btrfs_dev_item *dev_item)
{
	struct btrfs_fs_info *fs_info = leaf->fs_info;
	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
	struct btrfs_device *device;
	u64 devid;
	int ret;
	u8 fs_uuid[BTRFS_FSID_SIZE];
	u8 dev_uuid[BTRFS_UUID_SIZE];

	devid = btrfs_device_id(leaf, dev_item);
	read_extent_buffer(leaf, dev_uuid, btrfs_device_uuid(dev_item),
			   BTRFS_UUID_SIZE);
	read_extent_buffer(leaf, fs_uuid, btrfs_device_fsid(dev_item),
			   BTRFS_FSID_SIZE);

	if (memcmp(fs_uuid, fs_devices->metadata_uuid, BTRFS_FSID_SIZE)) {
		fs_devices = open_seed_devices(fs_info, fs_uuid);
		if (IS_ERR(fs_devices))
			return PTR_ERR(fs_devices);
	}

	device = btrfs_find_device(fs_info->fs_devices, devid, dev_uuid,
				   fs_uuid);
	if (!device) {
		if (!btrfs_test_opt(fs_info, DEGRADED)) {
			btrfs_report_missing_device(fs_info, devid,
							dev_uuid, true);
			return -ENOENT;
		}

		device = add_missing_dev(fs_devices, devid, dev_uuid);
		if (IS_ERR(device)) {
			btrfs_err(fs_info,
				"failed to add missing dev %llu: %ld",
				devid, PTR_ERR(device));
			return PTR_ERR(device);
		}
		btrfs_report_missing_device(fs_info, devid, dev_uuid, false);
	} else {
		if (!device->bdev) {
			if (!btrfs_test_opt(fs_info, DEGRADED)) {
				btrfs_report_missing_device(fs_info,
						devid, dev_uuid, true);
				return -ENOENT;
			}
			btrfs_report_missing_device(fs_info, devid,
							dev_uuid, false);
		}

		if (!device->bdev &&
		    !test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
			/*
			 * this happens when a device that was properly setup
			 * in the device info lists suddenly goes bad.
			 * device->bdev is NULL, and so we have to set
			 * device->missing to one here
			 */
			device->fs_devices->missing_devices++;
			set_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
		}

		/* Move the device to its own fs_devices */
		if (device->fs_devices != fs_devices) {
			ASSERT(test_bit(BTRFS_DEV_STATE_MISSING,
							&device->dev_state));

			list_move(&device->dev_list, &fs_devices->devices);
			device->fs_devices->num_devices--;
			fs_devices->num_devices++;

			device->fs_devices->missing_devices--;
			fs_devices->missing_devices++;

			device->fs_devices = fs_devices;
		}
	}

	if (device->fs_devices != fs_info->fs_devices) {
		BUG_ON(test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state));
		if (device->generation !=
		    btrfs_device_generation(leaf, dev_item))
			return -EINVAL;
	}

	fill_device_from_item(leaf, dev_item, device);
	if (device->bdev) {
		u64 max_total_bytes = i_size_read(device->bdev->bd_inode);

		if (device->total_bytes > max_total_bytes) {
			btrfs_err(fs_info,
			"device total_bytes should be at most %llu but found %llu",
				  max_total_bytes, device->total_bytes);
			return -EINVAL;
		}
	}
	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
	   !test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
		device->fs_devices->total_rw_bytes += device->total_bytes;
		atomic64_add(device->total_bytes - device->bytes_used,
				&fs_info->free_chunk_space);
	}
	ret = 0;
	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 (test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags)) {
		atomic_inc(&fs_info->balance_pause_req);
		mutex_unlock(&fs_info->balance_mutex);

		wait_event(fs_info->balance_wait_q,
			   !test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));

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

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


static noinline int find_next_devid(struct btrfs_fs_info *fs_info,
				    u64 *devid_ret)
{
	int ret;
	struct btrfs_key key;
	struct btrfs_key found_key;
	struct btrfs_path *path;

	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, fs_info->chunk_root, &key, path, 0, 0);
	if (ret < 0)
		goto error;

	if (ret == 0) {
		/* Corruption */
		btrfs_err(fs_info, "corrupted chunk tree devid -1 matched");
		ret = -EUCLEAN;
		goto error;
	}

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


static noinline struct btrfs_device *device_list_add(const char *path,
			   struct btrfs_super_block *disk_super,
			   bool *new_device_added)
{
	struct btrfs_device *device;
	struct btrfs_fs_devices *fs_devices = NULL;
	struct rcu_string *name;
	u64 found_transid = btrfs_super_generation(disk_super);
	u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
	bool has_metadata_uuid = (btrfs_super_incompat_flags(disk_super) &
		BTRFS_FEATURE_INCOMPAT_METADATA_UUID);
	bool fsid_change_in_progress = (btrfs_super_flags(disk_super) &
					BTRFS_SUPER_FLAG_CHANGING_FSID_V2);

	if (fsid_change_in_progress) {
		if (!has_metadata_uuid)
			fs_devices = find_fsid_inprogress(disk_super);
		else
			fs_devices = find_fsid_changed(disk_super);
	} else if (has_metadata_uuid) {
		fs_devices = find_fsid_with_metadata_uuid(disk_super);
	} else {
		fs_devices = find_fsid_reverted_metadata(disk_super);
		if (!fs_devices)
			fs_devices = find_fsid(disk_super->fsid, NULL);
	}

	if (!fs_devices) {
		if (has_metadata_uuid)
			fs_devices = alloc_fs_devices(disk_super->fsid,
						      disk_super->metadata_uuid);
		else
			fs_devices = alloc_fs_devices(disk_super->fsid, NULL);

		if (IS_ERR(fs_devices))
			return ERR_CAST(fs_devices);

		fs_devices->fsid_change = fsid_change_in_progress;

		mutex_lock(&fs_devices->device_list_mutex);
		list_add(&fs_devices->fs_list, &fs_uuids);

		device = NULL;
	} else {
		mutex_lock(&fs_devices->device_list_mutex);
		device = btrfs_find_device(fs_devices, devid,
				disk_super->dev_item.uuid, NULL);

		/*
		 * If this disk has been pulled into an fs devices created by
		 * a device which had the CHANGING_FSID_V2 flag then replace the
		 * metadata_uuid/fsid values of the fs_devices.
		 */
		if (fs_devices->fsid_change &&
		    found_transid > fs_devices->latest_generation) {
			memcpy(fs_devices->fsid, disk_super->fsid,
					BTRFS_FSID_SIZE);

			if (has_metadata_uuid)
				memcpy(fs_devices->metadata_uuid,
				       disk_super->metadata_uuid,
				       BTRFS_FSID_SIZE);
			else
				memcpy(fs_devices->metadata_uuid,
				       disk_super->fsid, BTRFS_FSID_SIZE);

			fs_devices->fsid_change = false;
		}
	}

	if (!device) {
		if (fs_devices->opened) {
			mutex_unlock(&fs_devices->device_list_mutex);
			return ERR_PTR(-EBUSY);
		}

		device = btrfs_alloc_device(NULL, &devid,
					    disk_super->dev_item.uuid);
		if (IS_ERR(device)) {
			mutex_unlock(&fs_devices->device_list_mutex);
			/* we can safely leave the fs_devices entry around */
			return device;
		}

		name = rcu_string_strdup(path, GFP_NOFS);
		if (!name) {
			btrfs_free_device(device);
			mutex_unlock(&fs_devices->device_list_mutex);
			return ERR_PTR(-ENOMEM);
		}
		rcu_assign_pointer(device->name, name);

		list_add_rcu(&device->dev_list, &fs_devices->devices);
		fs_devices->num_devices++;

		device->fs_devices = fs_devices;
		*new_device_added = true;

		if (disk_super->label[0])
			pr_info(
	"BTRFS: device label %s devid %llu transid %llu %s scanned by %s (%d)\n",
				disk_super->label, devid, found_transid, path,
				current->comm, task_pid_nr(current));
		else
			pr_info(
	"BTRFS: device fsid %pU devid %llu transid %llu %s scanned by %s (%d)\n",
				disk_super->fsid, devid, found_transid, path,
				current->comm, task_pid_nr(current));

	} else if (!device->name || strcmp(device->name->str, path)) {
		/*
		 * When FS is already mounted.
		 * 1. If you are here and if the device->name is NULL that
		 *    means this device was missing at time of FS mount.
		 * 2. If you are here and if the device->name is different
		 *    from 'path' that means either
		 *      a. The same device disappeared and reappeared with
		 *         different name. or
		 *      b. The missing-disk-which-was-replaced, has
		 *         reappeared now.
		 *
		 * We must allow 1 and 2a above. But 2b would be a spurious
		 * and unintentional.
		 *
		 * Further in case of 1 and 2a above, the disk at 'path'
		 * would have missed some transaction when it was away and
		 * in case of 2a the stale bdev has to be updated as well.
		 * 2b must not be allowed at all time.
		 */

		/*
		 * For now, we do allow update to btrfs_fs_device through the
		 * btrfs dev scan cli after FS has been mounted.  We're still
		 * tracking a problem where systems fail mount by subvolume id
		 * when we reject replacement on a mounted FS.
		 */
		if (!fs_devices->opened && found_transid < device->generation) {
			/*
			 * That is if the FS is _not_ mounted and if you
			 * are here, that means there is more than one
			 * disk with same uuid and devid.We keep the one
			 * with larger generation number or the last-in if
			 * generation are equal.
			 */
			mutex_unlock(&fs_devices->device_list_mutex);
			return ERR_PTR(-EEXIST);
		}

		/*
		 * We are going to replace the device path for a given devid,
		 * make sure it's the same device if the device is mounted
		 */
		if (device->bdev) {
			int error;
			dev_t path_dev;

			error = lookup_bdev(path, &path_dev);
			if (error) {
				mutex_unlock(&fs_devices->device_list_mutex);
				return ERR_PTR(error);
			}

			if (device->bdev->bd_dev != path_dev) {
				mutex_unlock(&fs_devices->device_list_mutex);
				/*
				 * device->fs_info may not be reliable here, so
				 * pass in a NULL instead. This avoids a
				 * possible use-after-free when the fs_info and
				 * fs_info->sb are already torn down.
				 */
				btrfs_warn_in_rcu(NULL,
	"duplicate device %s devid %llu generation %llu scanned by %s (%d)",
						  path, devid, found_transid,
						  current->comm,
						  task_pid_nr(current));
				return ERR_PTR(-EEXIST);
			}
			btrfs_info_in_rcu(device->fs_info,
	"devid %llu device path %s changed to %s scanned by %s (%d)",
					  devid, rcu_str_deref(device->name),
					  path, current->comm,
					  task_pid_nr(current));
		}

		name = rcu_string_strdup(path, GFP_NOFS);
		if (!name) {
			mutex_unlock(&fs_devices->device_list_mutex);
			return ERR_PTR(-ENOMEM);
		}
		rcu_string_free(device->name);
		rcu_assign_pointer(device->name, name);
		if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
			fs_devices->missing_devices--;
			clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
		}
	}

	/*
	 * Unmount does not free the btrfs_device struct but would zero
	 * generation along with most of the other members. So just update
	 * it back. We need it to pick the disk with largest generation
	 * (as above).
	 */
	if (!fs_devices->opened) {
		device->generation = found_transid;
		fs_devices->latest_generation = max_t(u64, found_transid,
						fs_devices->latest_generation);
	}

	fs_devices->total_devices = btrfs_super_num_devices(disk_super);

	mutex_unlock(&fs_devices->device_list_mutex);
	return device;
}


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_USAGE_RANGE) &&
	    !(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_USAGE_RANGE) &&
	    !(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_USAGE_RANGE) &&
	    !(bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)) {
		bctl->meta.flags |= BTRFS_BALANCE_ARGS_USAGE;
		bctl->meta.usage = 90;
	}
}


static void check_raid56_incompat_flag(struct btrfs_fs_info *info, u64 type)
{
	if (!(type & BTRFS_BLOCK_GROUP_RAID56_MASK))
		return;

	btrfs_set_fs_incompat(info, RAID56);
}


static bool need_full_stripe(enum btrfs_map_op op)
{
	return (op == BTRFS_MAP_WRITE || op == BTRFS_MAP_GET_READ_MIRRORS);
}


int btrfs_bg_type_to_factor(u64 flags)
{
	const int index = btrfs_bg_flags_to_raid_index(flags);

	return btrfs_raid_array[index].ncopies;
}


static inline int btrfs_chunk_max_errors(struct map_lookup *map)
{
	const int index = btrfs_bg_flags_to_raid_index(map->type);

	return btrfs_raid_array[index].tolerated_failures;
}


static int update_dev_stat_item(struct btrfs_trans_handle *trans,
				struct btrfs_device *device)
{
	struct btrfs_fs_info *fs_info = trans->fs_info;
	struct btrfs_root *dev_root = fs_info->dev_root;
	struct btrfs_path *path;
	struct btrfs_key key;
	struct extent_buffer *eb;
	struct btrfs_dev_stats_item *ptr;
	int ret;
	int i;

	key.objectid = BTRFS_DEV_STATS_OBJECTID;
	key.type = BTRFS_PERSISTENT_ITEM_KEY;
	key.offset = device->devid;

	path = btrfs_alloc_path();
	if (!path)
		return -ENOMEM;
	ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
	if (ret < 0) {
		btrfs_warn_in_rcu(fs_info,
			"error %d while searching for dev_stats item for device %s",
			      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) {
			btrfs_warn_in_rcu(fs_info,
				"delete too small dev_stats item for device %s failed %d",
				      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) {
			btrfs_warn_in_rcu(fs_info,
				"insert dev_stats item for device %s failed %d",
				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;
}


static void btrfs_report_missing_device(struct btrfs_fs_info *fs_info,
					u64 devid, u8 *uuid, bool error)
{
	if (error)
		btrfs_err_rl(fs_info, "devid %llu uuid %pU is missing",
			      devid, uuid);
	else
		btrfs_warn_rl(fs_info, "devid %llu uuid %pU is missing",
			      devid, uuid);
}


static inline int validate_convert_profile(struct btrfs_fs_info *fs_info,
		const struct btrfs_balance_args *bargs,
		u64 allowed, const char *type)
{
	if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
		return true;

	if (fs_info->sectorsize < PAGE_SIZE &&
		bargs->target & BTRFS_BLOCK_GROUP_RAID56_MASK) {
		btrfs_err(fs_info,
		"RAID56 is not yet supported for sectorsize %u with page size %lu",
			  fs_info->sectorsize, PAGE_SIZE);
		return false;
	}
	/* Profile is valid and does not have bits outside of the allowed set */
	if (alloc_profile_is_valid(bargs->target, 1) &&
	    (bargs->target & ~allowed) == 0)
		return true;

	btrfs_err(fs_info, "balance: invalid convert %s profile %s",
			type, btrfs_bg_type_to_raid_name(bargs->target));
	return false;
}


static struct btrfs_device * btrfs_find_next_active_device(
		struct btrfs_fs_devices *fs_devs, struct btrfs_device *device)
{
	struct btrfs_device *next_device;

	list_for_each_entry(next_device, &fs_devs->devices, dev_list) {
		if (next_device != device &&
		    !test_bit(BTRFS_DEV_STATE_MISSING, &next_device->dev_state)
		    && next_device->bdev)
			return next_device;
	}

	return NULL;
}


static struct btrfs_device *add_missing_dev(struct btrfs_fs_devices *fs_devices,
					    u64 devid, u8 *dev_uuid)
{
	struct btrfs_device *device;
	unsigned int nofs_flag;

	/*
	 * We call this under the chunk_mutex, so we want to use NOFS for this
	 * allocation, however we don't want to change btrfs_alloc_device() to
	 * always do NOFS because we use it in a lot of other GFP_KERNEL safe
	 * places.
	 */
	nofs_flag = memalloc_nofs_save();
	device = btrfs_alloc_device(NULL, &devid, dev_uuid);
	memalloc_nofs_restore(nofs_flag);
	if (IS_ERR(device))
		return device;

	list_add(&device->dev_list, &fs_devices->devices);
	device->fs_devices = fs_devices;
	fs_devices->num_devices++;

	set_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
	fs_devices->missing_devices++;

	return device;
}


static struct btrfs_device *btrfs_find_device_by_path(
		struct btrfs_fs_info *fs_info, const char *device_path)
{
	int ret = 0;
	struct btrfs_super_block *disk_super;
	u64 devid;
	u8 *dev_uuid;
	struct block_device *bdev;
	struct btrfs_device *device;

	ret = btrfs_get_bdev_and_sb(device_path, FMODE_READ,
				    fs_info->bdev_holder, 0, &bdev, &disk_super);
	if (ret)
		return ERR_PTR(ret);

	devid = btrfs_stack_device_id(&disk_super->dev_item);
	dev_uuid = disk_super->dev_item.uuid;
	if (btrfs_fs_incompat(fs_info, METADATA_UUID))
		device = btrfs_find_device(fs_info->fs_devices, devid, dev_uuid,
					   disk_super->metadata_uuid);
	else
		device = btrfs_find_device(fs_info->fs_devices, devid, dev_uuid,
					   disk_super->fsid);

	btrfs_release_disk_super(disk_super);
	if (!device)
		device = ERR_PTR(-ENOENT);
	blkdev_put(bdev, FMODE_READ);
	return device;
}


static void btrfs_close_one_device(struct btrfs_device *device)
{
	struct btrfs_fs_devices *fs_devices = device->fs_devices;

	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
		list_del_init(&device->dev_alloc_list);
		fs_devices->rw_devices--;
	}

	if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
		fs_devices->missing_devices--;

	btrfs_close_bdev(device);
	if (device->bdev) {
		fs_devices->open_devices--;
		device->bdev = NULL;
	}
	clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
	btrfs_destroy_dev_zone_info(device);

	device->fs_info = NULL;
	atomic_set(&device->dev_stats_ccnt, 0);
	extent_io_tree_release(&device->alloc_state);

	/* Verify the device is back in a pristine state  */
	ASSERT(!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state));
	ASSERT(!test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
	ASSERT(list_empty(&device->dev_alloc_list));
	ASSERT(list_empty(&device->post_commit_list));
	ASSERT(atomic_read(&device->reada_in_flight) == 0);
}