Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 7553 insertions, 0 deletions

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
new file mode 100644
index 000000000..2b4d33b58
--- /dev/null
+++ b/fs/btrfs/volumes.c
@@ -0,0 +1,7553 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ */
+
+#include <linux/sched.h>
+#include <linux/sched/mm.h>
+#include <linux/bio.h>
+#include <linux/slab.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/ratelimit.h>
+#include <linux/kthread.h>
+#include <linux/raid/pq.h>
+#include <linux/semaphore.h>
+#include <linux/uuid.h>
+#include <linux/list_sort.h>
+#include "ctree.h"
+#include "extent_map.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "print-tree.h"
+#include "volumes.h"
+#include "raid56.h"
+#include "async-thread.h"
+#include "check-integrity.h"
+#include "rcu-string.h"
+#include "math.h"
+#include "dev-replace.h"
+#include "sysfs.h"
+#include "tree-checker.h"
+
+const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
+	[BTRFS_RAID_RAID10] = {
+		.sub_stripes	= 2,
+		.dev_stripes	= 1,
+		.devs_max	= 0,	/* 0 == as many as possible */
+		.devs_min	= 4,
+		.tolerated_failures = 1,
+		.devs_increment	= 2,
+		.ncopies	= 2,
+		.raid_name	= "raid10",
+		.bg_flag	= BTRFS_BLOCK_GROUP_RAID10,
+		.mindev_error	= BTRFS_ERROR_DEV_RAID10_MIN_NOT_MET,
+	},
+	[BTRFS_RAID_RAID1] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 2,
+		.devs_min	= 2,
+		.tolerated_failures = 1,
+		.devs_increment	= 2,
+		.ncopies	= 2,
+		.raid_name	= "raid1",
+		.bg_flag	= BTRFS_BLOCK_GROUP_RAID1,
+		.mindev_error	= BTRFS_ERROR_DEV_RAID1_MIN_NOT_MET,
+	},
+	[BTRFS_RAID_DUP] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 2,
+		.devs_max	= 1,
+		.devs_min	= 1,
+		.tolerated_failures = 0,
+		.devs_increment	= 1,
+		.ncopies	= 2,
+		.raid_name	= "dup",
+		.bg_flag	= BTRFS_BLOCK_GROUP_DUP,
+		.mindev_error	= 0,
+	},
+	[BTRFS_RAID_RAID0] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 0,
+		.devs_min	= 2,
+		.tolerated_failures = 0,
+		.devs_increment	= 1,
+		.ncopies	= 1,
+		.raid_name	= "raid0",
+		.bg_flag	= BTRFS_BLOCK_GROUP_RAID0,
+		.mindev_error	= 0,
+	},
+	[BTRFS_RAID_SINGLE] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 1,
+		.devs_min	= 1,
+		.tolerated_failures = 0,
+		.devs_increment	= 1,
+		.ncopies	= 1,
+		.raid_name	= "single",
+		.bg_flag	= 0,
+		.mindev_error	= 0,
+	},
+	[BTRFS_RAID_RAID5] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 0,
+		.devs_min	= 2,
+		.tolerated_failures = 1,
+		.devs_increment	= 1,
+		.ncopies	= 1,
+		.raid_name	= "raid5",
+		.bg_flag	= BTRFS_BLOCK_GROUP_RAID5,
+		.mindev_error	= BTRFS_ERROR_DEV_RAID5_MIN_NOT_MET,
+	},
+	[BTRFS_RAID_RAID6] = {
+		.sub_stripes	= 1,
+		.dev_stripes	= 1,
+		.devs_max	= 0,
+		.devs_min	= 3,
+		.tolerated_failures = 2,
+		.devs_increment	= 1,
+		.ncopies	= 1,
+		.raid_name	= "raid6",
+		.bg_flag	= BTRFS_BLOCK_GROUP_RAID6,
+		.mindev_error	= BTRFS_ERROR_DEV_RAID6_MIN_NOT_MET,
+	},
+};
+
+const char *get_raid_name(enum btrfs_raid_types type)
+{
+	if (type >= BTRFS_NR_RAID_TYPES)
+		return NULL;
+
+	return btrfs_raid_array[type].raid_name;
+}
+
+static int init_first_rw_device(struct btrfs_trans_handle *trans,
+				struct btrfs_fs_info *fs_info);
+static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info);
+static void __btrfs_reset_dev_stats(struct btrfs_device *dev);
+static void btrfs_dev_stat_print_on_error(struct btrfs_device *dev);
+static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);
+static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
+			     enum btrfs_map_op op,
+			     u64 logical, u64 *length,
+			     struct btrfs_bio **bbio_ret,
+			     int mirror_num, int need_raid_map);
+
+/*
+ * Device locking
+ * ==============
+ *
+ * There are several mutexes that protect manipulation of devices and low-level
+ * structures like chunks but not block groups, extents or files
+ *
+ * uuid_mutex (global lock)
+ * ------------------------
+ * protects the fs_uuids list that tracks all per-fs fs_devices, resulting from
+ * the SCAN_DEV ioctl registration or from mount either implicitly (the first
+ * device) or requested by the device= mount option
+ *
+ * the mutex can be very coarse and can cover long-running operations
+ *
+ * protects: updates to fs_devices counters like missing devices, rw devices,
+ * seeding, structure cloning, openning/closing devices at mount/umount time
+ *
+ * global::fs_devs - add, remove, updates to the global list
+ *
+ * does not protect: manipulation of the fs_devices::devices list in general
+ * but in mount context it could be used to exclude list modifications by eg.
+ * scan ioctl
+ *
+ * btrfs_device::name - renames (write side), read is RCU
+ *
+ * fs_devices::device_list_mutex (per-fs, with RCU)
+ * ------------------------------------------------
+ * protects updates to fs_devices::devices, ie. adding and deleting
+ *
+ * simple list traversal with read-only actions can be done with RCU protection
+ *
+ * may be used to exclude some operations from running concurrently without any
+ * modifications to the list (see write_all_supers)
+ *
+ * Is not required at mount and close times, because our device list is
+ * protected by the uuid_mutex at that point.
+ *
+ * balance_mutex
+ * -------------
+ * protects balance structures (status, state) and context accessed from
+ * several places (internally, ioctl)
+ *
+ * chunk_mutex
+ * -----------
+ * protects chunks, adding or removing during allocation, trim or when a new
+ * device is added/removed
+ *
+ * cleaner_mutex
+ * -------------
+ * a big lock that is held by the cleaner thread and prevents running subvolume
+ * cleaning together with relocation or delayed iputs
+ *
+ *
+ * Lock nesting
+ * ============
+ *
+ * uuid_mutex
+ *   volume_mutex
+ *     device_list_mutex
+ *       chunk_mutex
+ *     balance_mutex
+ *
+ *
+ * Exclusive operations, BTRFS_FS_EXCL_OP
+ * ======================================
+ *
+ * Maintains the exclusivity of the following operations that apply to the
+ * whole filesystem and cannot run in parallel.
+ *
+ * - Balance (*)
+ * - Device add
+ * - Device remove
+ * - Device replace (*)
+ * - Resize
+ *
+ * The device operations (as above) can be in one of the following states:
+ *
+ * - Running state
+ * - Paused state
+ * - Completed state
+ *
+ * Only device operations marked with (*) can go into the Paused state for the
+ * following reasons:
+ *
+ * - ioctl (only Balance can be Paused through ioctl)
+ * - filesystem remounted as read-only
+ * - filesystem unmounted and mounted as read-only
+ * - system power-cycle and filesystem mounted as read-only
+ * - filesystem or device errors leading to forced read-only
+ *
+ * BTRFS_FS_EXCL_OP flag is set and cleared using atomic operations.
+ * During the course of Paused state, the BTRFS_FS_EXCL_OP remains set.
+ * A device operation in Paused or Running state can be canceled or resumed
+ * either by ioctl (Balance only) or when remounted as read-write.
+ * BTRFS_FS_EXCL_OP flag is cleared when the device operation is canceled or
+ * completed.
+ */
+
+DEFINE_MUTEX(uuid_mutex);
+static LIST_HEAD(fs_uuids);
+struct list_head *btrfs_get_fs_uuids(void)
+{
+	return &fs_uuids;
+}
+
+/*
+ * alloc_fs_devices - allocate struct btrfs_fs_devices
+ * @fsid:	if not NULL, copy the uuid to fs_devices::fsid
+ *
+ * Return a pointer to a new struct btrfs_fs_devices on success, or ERR_PTR().
+ * The returned struct is not linked onto any lists and can be destroyed with
+ * kfree() right away.
+ */
+static struct btrfs_fs_devices *alloc_fs_devices(const u8 *fsid)
+{
+	struct btrfs_fs_devices *fs_devs;
+
+	fs_devs = kzalloc(sizeof(*fs_devs), GFP_KERNEL);
+	if (!fs_devs)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&fs_devs->device_list_mutex);
+
+	INIT_LIST_HEAD(&fs_devs->devices);
+	INIT_LIST_HEAD(&fs_devs->resized_devices);
+	INIT_LIST_HEAD(&fs_devs->alloc_list);
+	INIT_LIST_HEAD(&fs_devs->fs_list);
+	if (fsid)
+		memcpy(fs_devs->fsid, fsid, BTRFS_FSID_SIZE);
+
+	return fs_devs;
+}
+
+void btrfs_free_device(struct btrfs_device *device)
+{
+	rcu_string_free(device->name);
+	bio_put(device->flush_bio);
+	kfree(device);
+}
+
+static void free_fs_devices(struct btrfs_fs_devices *fs_devices)
+{
+	struct btrfs_device *device;
+	WARN_ON(fs_devices->opened);
+	while (!list_empty(&fs_devices->devices)) {
+		device = list_entry(fs_devices->devices.next,
+				    struct btrfs_device, dev_list);
+		list_del(&device->dev_list);
+		btrfs_free_device(device);
+	}
+	kfree(fs_devices);
+}
+
+static void btrfs_kobject_uevent(struct block_device *bdev,
+				 enum kobject_action action)
+{
+	int ret;
+
+	ret = kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, action);
+	if (ret)
+		pr_warn("BTRFS: Sending event '%d' to kobject: '%s' (%p): failed\n",
+			action,
+			kobject_name(&disk_to_dev(bdev->bd_disk)->kobj),
+			&disk_to_dev(bdev->bd_disk)->kobj);
+}
+
+void __exit btrfs_cleanup_fs_uuids(void)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	while (!list_empty(&fs_uuids)) {
+		fs_devices = list_entry(fs_uuids.next,
+					struct btrfs_fs_devices, fs_list);
+		list_del(&fs_devices->fs_list);
+		free_fs_devices(fs_devices);
+	}
+}
+
+/*
+ * Returns a pointer to a new btrfs_device on success; ERR_PTR() on error.
+ * Returned struct is not linked onto any lists and must be destroyed using
+ * btrfs_free_device.
+ */
+static struct btrfs_device *__alloc_device(void)
+{
+	struct btrfs_device *dev;
+
+	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+	if (!dev)
+		return ERR_PTR(-ENOMEM);
+
+	/*
+	 * Preallocate a bio that's always going to be used for flushing device
+	 * barriers and matches the device lifespan
+	 */
+	dev->flush_bio = bio_alloc_bioset(GFP_KERNEL, 0, NULL);
+	if (!dev->flush_bio) {
+		kfree(dev);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	INIT_LIST_HEAD(&dev->dev_list);
+	INIT_LIST_HEAD(&dev->dev_alloc_list);
+	INIT_LIST_HEAD(&dev->resized_list);
+
+	spin_lock_init(&dev->io_lock);
+
+	atomic_set(&dev->reada_in_flight, 0);
+	atomic_set(&dev->dev_stats_ccnt, 0);
+	btrfs_device_data_ordered_init(dev);
+	INIT_RADIX_TREE(&dev->reada_zones, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+	INIT_RADIX_TREE(&dev->reada_extents, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+
+	return dev;
+}
+
+static noinline struct btrfs_fs_devices *find_fsid(u8 *fsid)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	list_for_each_entry(fs_devices, &fs_uuids, fs_list) {
+		if (memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE) == 0)
+			return fs_devices;
+	}
+	return NULL;
+}
+
+static int
+btrfs_get_bdev_and_sb(const char *device_path, fmode_t flags, void *holder,
+		      int flush, struct block_device **bdev,
+		      struct buffer_head **bh)
+{
+	int ret;
+
+	*bdev = blkdev_get_by_path(device_path, flags, holder);
+
+	if (IS_ERR(*bdev)) {
+		ret = PTR_ERR(*bdev);
+		goto error;
+	}
+
+	if (flush)
+		filemap_write_and_wait((*bdev)->bd_inode->i_mapping);
+	ret = set_blocksize(*bdev, BTRFS_BDEV_BLOCKSIZE);
+	if (ret) {
+		blkdev_put(*bdev, flags);
+		goto error;
+	}
+	invalidate_bdev(*bdev);
+	*bh = btrfs_read_dev_super(*bdev);
+	if (IS_ERR(*bh)) {
+		ret = PTR_ERR(*bh);
+		blkdev_put(*bdev, flags);
+		goto error;
+	}
+
+	return 0;
+
+error:
+	*bdev = NULL;
+	*bh = NULL;
+	return ret;
+}
+
+static void requeue_list(struct btrfs_pending_bios *pending_bios,
+			struct bio *head, struct bio *tail)
+{
+
+	struct bio *old_head;
+
+	old_head = pending_bios->head;
+	pending_bios->head = head;
+	if (pending_bios->tail)
+		tail->bi_next = old_head;
+	else
+		pending_bios->tail = tail;
+}
+
+/*
+ * we try to collect pending bios for a device so we don't get a large
+ * number of procs sending bios down to the same device.  This greatly
+ * improves the schedulers ability to collect and merge the bios.
+ *
+ * But, it also turns into a long list of bios to process and that is sure
+ * to eventually make the worker thread block.  The solution here is to
+ * make some progress and then put this work struct back at the end of
+ * the list if the block device is congested.  This way, multiple devices
+ * can make progress from a single worker thread.
+ */
+static noinline void run_scheduled_bios(struct btrfs_device *device)
+{
+	struct btrfs_fs_info *fs_info = device->fs_info;
+	struct bio *pending;
+	struct backing_dev_info *bdi;
+	struct btrfs_pending_bios *pending_bios;
+	struct bio *tail;
+	struct bio *cur;
+	int again = 0;
+	unsigned long num_run;
+	unsigned long batch_run = 0;
+	unsigned long last_waited = 0;
+	int force_reg = 0;
+	int sync_pending = 0;
+	struct blk_plug plug;
+
+	/*
+	 * this function runs all the bios we've collected for
+	 * a particular device.  We don't want to wander off to
+	 * another device without first sending all of these down.
+	 * So, setup a plug here and finish it off before we return
+	 */
+	blk_start_plug(&plug);
+
+	bdi = device->bdev->bd_bdi;
+
+loop:
+	spin_lock(&device->io_lock);
+
+loop_lock:
+	num_run = 0;
+
+	/* take all the bios off the list at once and process them
+	 * later on (without the lock held).  But, remember the
+	 * tail and other pointers so the bios can be properly reinserted
+	 * into the list if we hit congestion
+	 */
+	if (!force_reg && device->pending_sync_bios.head) {
+		pending_bios = &device->pending_sync_bios;
+		force_reg = 1;
+	} else {
+		pending_bios = &device->pending_bios;
+		force_reg = 0;
+	}
+
+	pending = pending_bios->head;
+	tail = pending_bios->tail;
+	WARN_ON(pending && !tail);
+
+	/*
+	 * if pending was null this time around, no bios need processing
+	 * at all and we can stop.  Otherwise it'll loop back up again
+	 * and do an additional check so no bios are missed.
+	 *
+	 * device->running_pending is used to synchronize with the
+	 * schedule_bio code.
+	 */
+	if (device->pending_sync_bios.head == NULL &&
+	    device->pending_bios.head == NULL) {
+		again = 0;
+		device->running_pending = 0;
+	} else {
+		again = 1;
+		device->running_pending = 1;
+	}
+
+	pending_bios->head = NULL;
+	pending_bios->tail = NULL;
+
+	spin_unlock(&device->io_lock);
+
+	while (pending) {
+
+		rmb();
+		/* we want to work on both lists, but do more bios on the
+		 * sync list than the regular list
+		 */
+		if ((num_run > 32 &&
+		    pending_bios != &device->pending_sync_bios &&
+		    device->pending_sync_bios.head) ||
+		   (num_run > 64 && pending_bios == &device->pending_sync_bios &&
+		    device->pending_bios.head)) {
+			spin_lock(&device->io_lock);
+			requeue_list(pending_bios, pending, tail);
+			goto loop_lock;
+		}
+
+		cur = pending;
+		pending = pending->bi_next;
+		cur->bi_next = NULL;
+
+		BUG_ON(atomic_read(&cur->__bi_cnt) == 0);
+
+		/*
+		 * if we're doing the sync list, record that our
+		 * plug has some sync requests on it
+		 *
+		 * If we're doing the regular list and there are
+		 * sync requests sitting around, unplug before
+		 * we add more
+		 */
+		if (pending_bios == &device->pending_sync_bios) {
+			sync_pending = 1;
+		} else if (sync_pending) {
+			blk_finish_plug(&plug);
+			blk_start_plug(&plug);
+			sync_pending = 0;
+		}
+
+		btrfsic_submit_bio(cur);
+		num_run++;
+		batch_run++;
+
+		cond_resched();
+
+		/*
+		 * we made progress, there is more work to do and the bdi
+		 * is now congested.  Back off and let other work structs
+		 * run instead
+		 */
+		if (pending && bdi_write_congested(bdi) && batch_run > 8 &&
+		    fs_info->fs_devices->open_devices > 1) {
+			struct io_context *ioc;
+
+			ioc = current->io_context;
+
+			/*
+			 * the main goal here is that we don't want to
+			 * block if we're going to be able to submit
+			 * more requests without blocking.
+			 *
+			 * This code does two great things, it pokes into
+			 * the elevator code from a filesystem _and_
+			 * it makes assumptions about how batching works.
+			 */
+			if (ioc && ioc->nr_batch_requests > 0 &&
+			    time_before(jiffies, ioc->last_waited + HZ/50UL) &&
+			    (last_waited == 0 ||
+			     ioc->last_waited == last_waited)) {
+				/*
+				 * we want to go through our batch of
+				 * requests and stop.  So, we copy out
+				 * the ioc->last_waited time and test
+				 * against it before looping
+				 */
+				last_waited = ioc->last_waited;
+				cond_resched();
+				continue;
+			}
+			spin_lock(&device->io_lock);
+			requeue_list(pending_bios, pending, tail);
+			device->running_pending = 1;
+
+			spin_unlock(&device->io_lock);
+			btrfs_queue_work(fs_info->submit_workers,
+					 &device->work);
+			goto done;
+		}
+	}
+
+	cond_resched();
+	if (again)
+		goto loop;
+
+	spin_lock(&device->io_lock);
+	if (device->pending_bios.head || device->pending_sync_bios.head)
+		goto loop_lock;
+	spin_unlock(&device->io_lock);
+
+done:
+	blk_finish_plug(&plug);
+}
+
+static void pending_bios_fn(struct btrfs_work *work)
+{
+	struct btrfs_device *device;
+
+	device = container_of(work, struct btrfs_device, work);
+	run_scheduled_bios(device);
+}
+
+/*
+ *  Search and remove all stale (devices which are not mounted) devices.
+ *  When both inputs are NULL, it will search and release all stale devices.
+ *  path:	Optional. When provided will it release all unmounted devices
+ *		matching this path only.
+ *  skip_dev:	Optional. Will skip this device when searching for the stale
+ *		devices.
+ */
+static void btrfs_free_stale_devices(const char *path,
+				     struct btrfs_device *skip_device)
+{
+	struct btrfs_fs_devices *fs_devices, *tmp_fs_devices;
+	struct btrfs_device *device, *tmp_device;
+
+	list_for_each_entry_safe(fs_devices, tmp_fs_devices, &fs_uuids, fs_list) {
+		mutex_lock(&fs_devices->device_list_mutex);
+		if (fs_devices->opened) {
+			mutex_unlock(&fs_devices->device_list_mutex);
+			continue;
+		}
+
+		list_for_each_entry_safe(device, tmp_device,
+					 &fs_devices->devices, dev_list) {
+			int not_found = 0;
+
+			if (skip_device && skip_device == device)
+				continue;
+			if (path && !device->name)
+				continue;
+
+			rcu_read_lock();
+			if (path)
+				not_found = strcmp(rcu_str_deref(device->name),
+						   path);
+			rcu_read_unlock();
+			if (not_found)
+				continue;
+
+			/* delete the stale device */
+			fs_devices->num_devices--;
+			list_del(&device->dev_list);
+			btrfs_free_device(device);
+
+			if (fs_devices->num_devices == 0)
+				break;
+		}
+		mutex_unlock(&fs_devices->device_list_mutex);
+		if (fs_devices->num_devices == 0) {
+			btrfs_sysfs_remove_fsid(fs_devices);
+			list_del(&fs_devices->fs_list);
+			free_fs_devices(fs_devices);
+		}
+	}
+}
+
+/*
+ * This is only used on mount, and we are protected from competing things
+ * messing with our fs_devices by the uuid_mutex, thus we do not need the
+ * fs_devices->device_list_mutex here.
+ */
+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 buffer_head *bh;
+	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, &bh);
+	if (ret)
+		return ret;
+
+	disk_super = (struct btrfs_super_block *)bh->b_data;
+	devid = btrfs_stack_device_id(&disk_super->dev_item);
+	if (devid != device->devid)
+		goto error_brelse;
+
+	if (memcmp(device->uuid, disk_super->dev_item.uuid, BTRFS_UUID_SIZE))
+		goto error_brelse;
+
+	device->generation = btrfs_super_generation(disk_super);
+
+	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_SEEDING) {
+		clear_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
+		fs_devices->seeding = 1;
+	} 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 = 1;
+
+	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);
+	}
+	brelse(bh);
+
+	return 0;
+
+error_brelse:
+	brelse(bh);
+	blkdev_put(bdev, flags);
+
+	return -EINVAL;
+}
+
+/*
+ * Add new device to list of registered devices
+ *
+ * Returns:
+ * device pointer which was just added or updated when successful
+ * error pointer when failed
+ */
+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;
+	struct rcu_string *name;
+	u64 found_transid = btrfs_super_generation(disk_super);
+	u64 devid = btrfs_stack_device_id(&disk_super->dev_item);
+
+	fs_devices = find_fsid(disk_super->fsid);
+	if (!fs_devices) {
+		fs_devices = alloc_fs_devices(disk_super->fsid);
+		if (IS_ERR(fs_devices))
+			return ERR_CAST(fs_devices);
+
+		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, 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\n",
+				disk_super->label, devid, found_transid, path);
+		else
+			pr_info("BTRFS: device fsid %pU devid %llu transid %llu %s\n",
+				disk_super->fsid, devid, found_transid, path);
+
+	} 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) {
+			struct block_device *path_bdev;
+
+			path_bdev = lookup_bdev(path);
+			if (IS_ERR(path_bdev)) {
+				mutex_unlock(&fs_devices->device_list_mutex);
+				return ERR_CAST(path_bdev);
+			}
+
+			if (device->bdev != path_bdev) {
+				bdput(path_bdev);
+				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);
+			}
+			bdput(path_bdev);
+			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->total_devices = btrfs_super_num_devices(disk_super);
+
+	mutex_unlock(&fs_devices->device_list_mutex);
+	return device;
+}
+
+static struct btrfs_fs_devices *clone_fs_devices(struct btrfs_fs_devices *orig)
+{
+	struct btrfs_fs_devices *fs_devices;
+	struct btrfs_device *device;
+	struct btrfs_device *orig_dev;
+
+	fs_devices = alloc_fs_devices(orig->fsid);
+	if (IS_ERR(fs_devices))
+		return fs_devices;
+
+	mutex_lock(&orig->device_list_mutex);
+	fs_devices->total_devices = orig->total_devices;
+
+	/* We have held the volume lock, it is safe to get the devices. */
+	list_for_each_entry(orig_dev, &orig->devices, dev_list) {
+		struct rcu_string *name;
+
+		device = btrfs_alloc_device(NULL, &orig_dev->devid,
+					    orig_dev->uuid);
+		if (IS_ERR(device))
+			goto error;
+
+		/*
+		 * This is ok to do without rcu read locked because we hold the
+		 * uuid mutex so nothing we touch in here is going to disappear.
+		 */
+		if (orig_dev->name) {
+			name = rcu_string_strdup(orig_dev->name->str,
+					GFP_KERNEL);
+			if (!name) {
+				btrfs_free_device(device);
+				goto error;
+			}
+			rcu_assign_pointer(device->name, name);
+		}
+
+		list_add(&device->dev_list, &fs_devices->devices);
+		device->fs_devices = fs_devices;
+		fs_devices->num_devices++;
+	}
+	mutex_unlock(&orig->device_list_mutex);
+	return fs_devices;
+error:
+	mutex_unlock(&orig->device_list_mutex);
+	free_fs_devices(fs_devices);
+	return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * After we have read the system tree and know devids belonging to
+ * this filesystem, remove the device which does not belong there.
+ */
+void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices, int step)
+{
+	struct btrfs_device *device, *next;
+	struct btrfs_device *latest_dev = NULL;
+
+	mutex_lock(&uuid_mutex);
+again:
+	/* This is the initialized path, it is safe to release the devices. */
+	list_for_each_entry_safe(device, next, &fs_devices->devices, dev_list) {
+		if (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);
+	}
+
+	if (fs_devices->seed) {
+		fs_devices = fs_devices->seed;
+		goto again;
+	}
+
+	fs_devices->latest_bdev = latest_dev->bdev;
+
+	mutex_unlock(&uuid_mutex);
+}
+
+static void free_device_rcu(struct rcu_head *head)
+{
+	struct btrfs_device *device;
+
+	device = container_of(head, struct btrfs_device, rcu);
+	btrfs_free_device(device);
+}
+
+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);
+}
+
+static void btrfs_close_one_device(struct btrfs_device *device)
+{
+	struct btrfs_fs_devices *fs_devices = device->fs_devices;
+	struct btrfs_device *new_device;
+	struct rcu_string *name;
+
+	if (device->bdev)
+		fs_devices->open_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 (device->devid == BTRFS_DEV_REPLACE_DEVID)
+		clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
+
+	if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state)) {
+		clear_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state);
+		fs_devices->missing_devices--;
+	}
+
+	btrfs_close_bdev(device);
+
+	new_device = btrfs_alloc_device(NULL, &device->devid,
+					device->uuid);
+	BUG_ON(IS_ERR(new_device)); /* -ENOMEM */
+
+	/* Safe because we are under uuid_mutex */
+	if (device->name) {
+		name = rcu_string_strdup(device->name->str, GFP_NOFS);
+		BUG_ON(!name); /* -ENOMEM */
+		rcu_assign_pointer(new_device->name, name);
+	}
+
+	list_replace_rcu(&device->dev_list, &new_device->dev_list);
+	new_device->fs_devices = device->fs_devices;
+
+	call_rcu(&device->rcu, free_device_rcu);
+}
+
+static int close_fs_devices(struct btrfs_fs_devices *fs_devices)
+{
+	struct btrfs_device *device, *tmp;
+
+	if (--fs_devices->opened > 0)
+		return 0;
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_for_each_entry_safe(device, tmp, &fs_devices->devices, dev_list) {
+		btrfs_close_one_device(device);
+	}
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	WARN_ON(fs_devices->open_devices);
+	WARN_ON(fs_devices->rw_devices);
+	fs_devices->opened = 0;
+	fs_devices->seeding = 0;
+
+	return 0;
+}
+
+int btrfs_close_devices(struct btrfs_fs_devices *fs_devices)
+{
+	struct btrfs_fs_devices *seed_devices = NULL;
+	int ret;
+
+	mutex_lock(&uuid_mutex);
+	ret = close_fs_devices(fs_devices);
+	if (!fs_devices->opened) {
+		seed_devices = fs_devices->seed;
+		fs_devices->seed = NULL;
+	}
+	mutex_unlock(&uuid_mutex);
+
+	while (seed_devices) {
+		fs_devices = seed_devices;
+		seed_devices = fs_devices->seed;
+		close_fs_devices(fs_devices);
+		free_fs_devices(fs_devices);
+	}
+	return ret;
+}
+
+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;
+	int ret = 0;
+
+	flags |= FMODE_EXCL;
+
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		/* Just open everything we can; ignore failures here */
+		if (btrfs_open_one_device(fs_devices, device, flags, holder))
+			continue;
+
+		if (!latest_dev ||
+		    device->generation > latest_dev->generation)
+			latest_dev = device;
+	}
+	if (fs_devices->open_devices == 0) {
+		ret = -EINVAL;
+		goto out;
+	}
+	fs_devices->opened = 1;
+	fs_devices->latest_bdev = latest_dev->bdev;
+	fs_devices->total_rw_bytes = 0;
+out:
+	return ret;
+}
+
+static int devid_cmp(void *priv, struct list_head *a, struct list_head *b)
+{
+	struct btrfs_device *dev1, *dev2;
+
+	dev1 = list_entry(a, struct btrfs_device, dev_list);
+	dev2 = list_entry(b, struct btrfs_device, dev_list);
+
+	if (dev1->devid < dev2->devid)
+		return -1;
+	else if (dev1->devid > dev2->devid)
+		return 1;
+	return 0;
+}
+
+int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
+		       fmode_t flags, void *holder)
+{
+	int ret;
+
+	lockdep_assert_held(&uuid_mutex);
+	/*
+	 * The device_list_mutex cannot be taken here in case opening the
+	 * underlying device takes further locks like bd_mutex.
+	 *
+	 * We also don't need the lock here as this is called during mount and
+	 * exclusion is provided by uuid_mutex
+	 */
+
+	if (fs_devices->opened) {
+		fs_devices->opened++;
+		ret = 0;
+	} else {
+		list_sort(NULL, &fs_devices->devices, devid_cmp);
+		ret = open_fs_devices(fs_devices, flags, holder);
+	}
+
+	return ret;
+}
+
+static void btrfs_release_disk_super(struct page *page)
+{
+	kunmap(page);
+	put_page(page);
+}
+
+static int btrfs_read_disk_super(struct block_device *bdev, u64 bytenr,
+				 struct page **page,
+				 struct btrfs_super_block **disk_super)
+{
+	void *p;
+	pgoff_t index;
+
+	/* make sure our super fits in the device */
+	if (bytenr + PAGE_SIZE >= i_size_read(bdev->bd_inode))
+		return 1;
+
+	/* make sure our super fits in the page */
+	if (sizeof(**disk_super) > PAGE_SIZE)
+		return 1;
+
+	/* make sure our super doesn't straddle pages on disk */
+	index = bytenr >> PAGE_SHIFT;
+	if ((bytenr + sizeof(**disk_super) - 1) >> PAGE_SHIFT != index)
+		return 1;
+
+	/* pull in the page with our super */
+	*page = read_cache_page_gfp(bdev->bd_inode->i_mapping,
+				   index, GFP_KERNEL);
+
+	if (IS_ERR_OR_NULL(*page))
+		return 1;
+
+	p = kmap(*page);
+
+	/* align our pointer to the offset of the super block */
+	*disk_super = p + (bytenr & ~PAGE_MASK);
+
+	if (btrfs_super_bytenr(*disk_super) != bytenr ||
+	    btrfs_super_magic(*disk_super) != BTRFS_MAGIC) {
+		btrfs_release_disk_super(*page);
+		return 1;
+	}
+
+	if ((*disk_super)->label[0] &&
+		(*disk_super)->label[BTRFS_LABEL_SIZE - 1])
+		(*disk_super)->label[BTRFS_LABEL_SIZE - 1] = '\0';
+
+	return 0;
+}
+
+/*
+ * Look for a btrfs signature on a device. This may be called out of the mount path
+ * and we are not allowed to call set_blocksize during the scan. The superblock
+ * is read via pagecache
+ */
+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;
+	struct page *page;
+	u64 bytenr;
+
+	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
+	 */
+	bytenr = btrfs_sb_offset(0);
+	flags |= FMODE_EXCL;
+
+	bdev = blkdev_get_by_path(path, flags, holder);
+	if (IS_ERR(bdev))
+		return ERR_CAST(bdev);
+
+	if (btrfs_read_disk_super(bdev, bytenr, &page, &disk_super)) {
+		device = ERR_PTR(-EINVAL);
+		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(page);
+
+error_bdev_put:
+	blkdev_put(bdev, flags);
+
+	return device;
+}
+
+static int contains_pending_extent(struct btrfs_transaction *transaction,
+				   struct btrfs_device *device,
+				   u64 *start, u64 len)
+{
+	struct btrfs_fs_info *fs_info = device->fs_info;
+	struct extent_map *em;
+	struct list_head *search_list = &fs_info->pinned_chunks;
+	int ret = 0;
+	u64 physical_start = *start;
+
+	if (transaction)
+		search_list = &transaction->pending_chunks;
+again:
+	list_for_each_entry(em, search_list, list) {
+		struct map_lookup *map;
+		int i;
+
+		map = em->map_lookup;
+		for (i = 0; i < map->num_stripes; i++) {
+			u64 end;
+
+			if (map->stripes[i].dev != device)
+				continue;
+			if (map->stripes[i].physical >= physical_start + len ||
+			    map->stripes[i].physical + em->orig_block_len <=
+			    physical_start)
+				continue;
+			/*
+			 * Make sure that while processing the pinned list we do
+			 * not override our *start with a lower value, because
+			 * we can have pinned chunks that fall within this
+			 * device hole and that have lower physical addresses
+			 * than the pending chunks we processed before. If we
+			 * do not take this special care we can end up getting
+			 * 2 pending chunks that start at the same physical
+			 * device offsets because the end offset of a pinned
+			 * chunk can be equal to the start offset of some
+			 * pending chunk.
+			 */
+			end = map->stripes[i].physical + em->orig_block_len;
+			if (end > *start) {
+				*start = end;
+				ret = 1;
+			}
+		}
+	}
+	if (search_list != &fs_info->pinned_chunks) {
+		search_list = &fs_info->pinned_chunks;
+		goto again;
+	}
+
+	return ret;
+}
+
+
+/*
+ * find_free_dev_extent_start - find free space in the specified device
+ * @device:	  the device which we search the free space in
+ * @num_bytes:	  the size of the free space that we need
+ * @search_start: the position from which to begin the search
+ * @start:	  store the start of the free space.
+ * @len:	  the size of the free space. that we find, or the size
+ *		  of the max free space if we don't find suitable free space
+ *
+ * this uses a pretty simple search, the expectation is that it is
+ * called very infrequently and that a given device has a small number
+ * of extents
+ *
+ * @start is used to store the start of the free space if we find. But if we
+ * don't find suitable free space, it will be used to store the start position
+ * of the max free space.
+ *
+ * @len is used to store the size of the free space that we find.
+ * But if we don't find suitable free space, it is used to store the size of
+ * the max free space.
+ */
+int find_free_dev_extent_start(struct btrfs_transaction *transaction,
+			       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;
+
+	/*
+	 * 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.
+	 */
+	search_start = max_t(u64, search_start, SZ_1M);
+
+	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_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) {
+		ret = btrfs_previous_item(root, path, key.objectid, key.type);
+		if (ret < 0)
+			goto out;
+	}
+
+	while (1) {
+		l = path->nodes[0];
+		slot = path->slots[0];
+		if (slot >= btrfs_header_nritems(l)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret == 0)
+				continue;
+			if (ret < 0)
+				goto out;
+
+			break;
+		}
+		btrfs_item_key_to_cpu(l, &key, slot);
+
+		if (key.objectid < device->devid)
+			goto next;
+
+		if (key.objectid > device->devid)
+			break;
+
+		if (key.type != BTRFS_DEV_EXTENT_KEY)
+			goto next;
+
+		if (key.offset > search_start) {
+			hole_size = key.offset - search_start;
+
+			/*
+			 * Have to check before we set max_hole_start, otherwise
+			 * we could end up sending back this offset anyway.
+			 */
+			if (contains_pending_extent(transaction, device,
+						    &search_start,
+						    hole_size)) {
+				if (key.offset >= search_start) {
+					hole_size = key.offset - search_start;
+				} else {
+					WARN_ON_ONCE(1);
+					hole_size = 0;
+				}
+			}
+
+			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 (contains_pending_extent(transaction, device, &search_start,
+					    hole_size)) {
+			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;
+}
+
+int find_free_dev_extent(struct btrfs_trans_handle *trans,
+			 struct btrfs_device *device, u64 num_bytes,
+			 u64 *start, u64 *len)
+{
+	/* FIXME use last free of some kind */
+	return find_free_dev_extent_start(trans->transaction, device,
+					  num_bytes, 0, start, len);
+}
+
+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 {
+		btrfs_handle_fs_error(fs_info, ret, "Slot search failed");
+		goto out;
+	}
+
+	*dev_extent_len = btrfs_dev_extent_length(leaf, extent);
+
+	ret = btrfs_del_item(trans, root, path);
+	if (ret) {
+		btrfs_handle_fs_error(fs_info, ret,
+				      "Failed to remove dev extent item");
+	} else {
+		set_bit(BTRFS_TRANS_HAVE_FREE_BGS, &trans->transaction->flags);
+	}
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+static int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
+				  struct btrfs_device *device,
+				  u64 chunk_offset, u64 start, u64 num_bytes)
+{
+	int ret;
+	struct btrfs_path *path;
+	struct btrfs_fs_info *fs_info = device->fs_info;
+	struct btrfs_root *root = fs_info->dev_root;
+	struct btrfs_dev_extent *extent;
+	struct extent_buffer *leaf;
+	struct btrfs_key key;
+
+	WARN_ON(!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state));
+	WARN_ON(test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state));
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = device->devid;
+	key.offset = start;
+	key.type = BTRFS_DEV_EXTENT_KEY;
+	ret = btrfs_insert_empty_item(trans, root, path, &key,
+				      sizeof(*extent));
+	if (ret)
+		goto out;
+
+	leaf = path->nodes[0];
+	extent = btrfs_item_ptr(leaf, path->slots[0],
+				struct btrfs_dev_extent);
+	btrfs_set_dev_extent_chunk_tree(leaf, extent,
+					BTRFS_CHUNK_TREE_OBJECTID);
+	btrfs_set_dev_extent_chunk_objectid(leaf, extent,
+					    BTRFS_FIRST_CHUNK_TREE_OBJECTID);
+	btrfs_set_dev_extent_chunk_offset(leaf, extent, chunk_offset);
+
+	btrfs_set_dev_extent_length(leaf, extent, num_bytes);
+	btrfs_mark_buffer_dirty(leaf);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+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.map_tree;
+	read_lock(&em_tree->lock);
+	n = rb_last(&em_tree->map);
+	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 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;
+
+	BUG_ON(ret == 0); /* Corruption */
+
+	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;
+}
+
+/*
+ * the device information is stored in the chunk root
+ * the btrfs_device struct should be fully filled in
+ */
+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->fsid, ptr, BTRFS_FSID_SIZE);
+	btrfs_mark_buffer_dirty(leaf);
+
+	ret = 0;
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * Function to update ctime/mtime for a given device path.
+ * Mainly used for ctime/mtime based probe like libblkid.
+ */
+static void update_dev_time(const char *path_name)
+{
+	struct file *filp;
+
+	filp = filp_open(path_name, O_RDWR, 0);
+	if (IS_ERR(filp))
+		return;
+	file_update_time(filp);
+	filp_close(filp, NULL);
+}
+
+static int btrfs_rm_dev_item(struct btrfs_fs_info *fs_info,
+			     struct btrfs_device *device)
+{
+	struct btrfs_root *root = fs_info->chunk_root;
+	int ret;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	struct btrfs_trans_handle *trans;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		btrfs_free_path(path);
+		return PTR_ERR(trans);
+	}
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.type = BTRFS_DEV_ITEM_KEY;
+	key.offset = device->devid;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret) {
+		if (ret > 0)
+			ret = -ENOENT;
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		goto out;
+	}
+
+	ret = btrfs_del_item(trans, root, path);
+	if (ret) {
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+	}
+
+out:
+	btrfs_free_path(path);
+	if (!ret)
+		ret = btrfs_commit_transaction(trans);
+	return ret;
+}
+
+/*
+ * Verify that @num_devices satisfies the RAID profile constraints in the whole
+ * filesystem. It's up to the caller to adjust that number regarding eg. device
+ * replace.
+ */
+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) {
+			int ret = btrfs_raid_array[i].mindev_error;
+
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
+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;
+}
+
+/*
+ * Helper function to check if the given device is part of s_bdev / latest_bdev
+ * and replace it with the provided or the next active device, in the context
+ * where this function called, there should be always be another device (or
+ * this_dev) which is active.
+ */
+void btrfs_assign_next_active_device(struct btrfs_device *device,
+				     struct btrfs_device *this_dev)
+{
+	struct btrfs_fs_info *fs_info = device->fs_info;
+	struct btrfs_device *next_device;
+
+	if (this_dev)
+		next_device = this_dev;
+	else
+		next_device = btrfs_find_next_active_device(fs_info->fs_devices,
+								device);
+	ASSERT(next_device);
+
+	if (fs_info->sb->s_bdev &&
+			(fs_info->sb->s_bdev == device->bdev))
+		fs_info->sb->s_bdev = next_device->bdev;
+
+	if (fs_info->fs_devices->latest_bdev == device->bdev)
+		fs_info->fs_devices->latest_bdev = next_device->bdev;
+}
+
+int btrfs_rm_device(struct btrfs_fs_info *fs_info, const char *device_path,
+		u64 devid)
+{
+	struct btrfs_device *device;
+	struct btrfs_fs_devices *cur_devices;
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	u64 num_devices;
+	int ret = 0;
+
+	mutex_lock(&uuid_mutex);
+
+	num_devices = fs_devices->num_devices;
+	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+		WARN_ON(num_devices < 1);
+		num_devices--;
+	}
+	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+
+	ret = btrfs_check_raid_min_devices(fs_info, num_devices - 1);
+	if (ret)
+		goto out;
+
+	ret = btrfs_find_device_by_devspec(fs_info, devid, device_path,
+					   &device);
+	if (ret)
+		goto out;
+
+	if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) {
+		ret = BTRFS_ERROR_DEV_TGT_REPLACE;
+		goto out;
+	}
+
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
+	    fs_info->fs_devices->rw_devices == 1) {
+		ret = BTRFS_ERROR_DEV_ONLY_WRITABLE;
+		goto out;
+	}
+
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
+		mutex_lock(&fs_info->chunk_mutex);
+		list_del_init(&device->dev_alloc_list);
+		device->fs_devices->rw_devices--;
+		mutex_unlock(&fs_info->chunk_mutex);
+	}
+
+	mutex_unlock(&uuid_mutex);
+	ret = btrfs_shrink_device(device, 0);
+	mutex_lock(&uuid_mutex);
+	if (ret)
+		goto error_undo;
+
+	/*
+	 * TODO: the superblock still includes this device in its num_devices
+	 * counter although write_all_supers() is not locked out. This
+	 * could give a filesystem state which requires a degraded mount.
+	 */
+	ret = btrfs_rm_dev_item(fs_info, device);
+	if (ret)
+		goto error_undo;
+
+	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
+	btrfs_scrub_cancel_dev(fs_info, device);
+
+	/*
+	 * the device list mutex makes sure that we don't change
+	 * the device list while someone else is writing out all
+	 * the device supers. Whoever is writing all supers, should
+	 * lock the device list mutex before getting the number of
+	 * devices in the super block (super_copy). Conversely,
+	 * whoever updates the number of devices in the super block
+	 * (super_copy) should hold the device list mutex.
+	 */
+
+	/*
+	 * In normal cases the cur_devices == fs_devices. But in case
+	 * of deleting a seed device, the cur_devices should point to
+	 * its own fs_devices listed under the fs_devices->seed.
+	 */
+	cur_devices = device->fs_devices;
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_del_rcu(&device->dev_list);
+
+	cur_devices->num_devices--;
+	cur_devices->total_devices--;
+	/* Update total_devices of the parent fs_devices if it's seed */
+	if (cur_devices != fs_devices)
+		fs_devices->total_devices--;
+
+	if (test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
+		cur_devices->missing_devices--;
+
+	btrfs_assign_next_active_device(device, NULL);
+
+	if (device->bdev) {
+		cur_devices->open_devices--;
+		/* remove sysfs entry */
+		btrfs_sysfs_rm_device_link(fs_devices, device);
+	}
+
+	num_devices = btrfs_super_num_devices(fs_info->super_copy) - 1;
+	btrfs_set_super_num_devices(fs_info->super_copy, num_devices);
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	/*
+	 * at this point, the device is zero sized and detached from
+	 * the devices list.  All that's left is to zero out the old
+	 * supers and free the device.
+	 */
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state))
+		btrfs_scratch_superblocks(device->bdev, device->name->str);
+
+	btrfs_close_bdev(device);
+	call_rcu(&device->rcu, free_device_rcu);
+
+	if (cur_devices->open_devices == 0) {
+		while (fs_devices) {
+			if (fs_devices->seed == cur_devices) {
+				fs_devices->seed = cur_devices->seed;
+				break;
+			}
+			fs_devices = fs_devices->seed;
+		}
+		cur_devices->seed = NULL;
+		close_fs_devices(cur_devices);
+		free_fs_devices(cur_devices);
+	}
+
+out:
+	mutex_unlock(&uuid_mutex);
+	return ret;
+
+error_undo:
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
+		mutex_lock(&fs_info->chunk_mutex);
+		list_add(&device->dev_alloc_list,
+			 &fs_devices->alloc_list);
+		device->fs_devices->rw_devices++;
+		mutex_unlock(&fs_info->chunk_mutex);
+	}
+	goto out;
+}
+
+void btrfs_rm_dev_replace_remove_srcdev(struct btrfs_device *srcdev)
+{
+	struct btrfs_fs_devices *fs_devices;
+
+	lockdep_assert_held(&srcdev->fs_info->fs_devices->device_list_mutex);
+
+	/*
+	 * in case of fs with no seed, srcdev->fs_devices will point
+	 * to fs_devices of fs_info. However when the dev being replaced is
+	 * a seed dev it will point to the seed's local fs_devices. In short
+	 * srcdev will have its correct fs_devices in both the cases.
+	 */
+	fs_devices = srcdev->fs_devices;
+
+	list_del_rcu(&srcdev->dev_list);
+	list_del(&srcdev->dev_alloc_list);
+	fs_devices->num_devices--;
+	if (test_bit(BTRFS_DEV_STATE_MISSING, &srcdev->dev_state))
+		fs_devices->missing_devices--;
+
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &srcdev->dev_state))
+		fs_devices->rw_devices--;
+
+	if (srcdev->bdev)
+		fs_devices->open_devices--;
+}
+
+void btrfs_rm_dev_replace_free_srcdev(struct btrfs_fs_info *fs_info,
+				      struct btrfs_device *srcdev)
+{
+	struct btrfs_fs_devices *fs_devices = srcdev->fs_devices;
+
+	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &srcdev->dev_state)) {
+		/* zero out the old super if it is writable */
+		btrfs_scratch_superblocks(srcdev->bdev, srcdev->name->str);
+	}
+
+	btrfs_close_bdev(srcdev);
+	call_rcu(&srcdev->rcu, free_device_rcu);
+
+	/* if this is no devs we rather delete the fs_devices */
+	if (!fs_devices->num_devices) {
+		struct btrfs_fs_devices *tmp_fs_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);
+
+		tmp_fs_devices = fs_info->fs_devices;
+		while (tmp_fs_devices) {
+			if (tmp_fs_devices->seed == fs_devices) {
+				tmp_fs_devices->seed = fs_devices->seed;
+				break;
+			}
+			tmp_fs_devices = tmp_fs_devices->seed;
+		}
+		fs_devices->seed = NULL;
+		close_fs_devices(fs_devices);
+		free_fs_devices(fs_devices);
+	}
+}
+
+void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
+{
+	struct btrfs_fs_devices *fs_devices = tgtdev->fs_info->fs_devices;
+
+	WARN_ON(!tgtdev);
+	mutex_lock(&fs_devices->device_list_mutex);
+
+	btrfs_sysfs_rm_device_link(fs_devices, 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->bdev, tgtdev->name->str);
+
+	btrfs_close_bdev(tgtdev);
+	call_rcu(&tgtdev->rcu, free_device_rcu);
+}
+
+static int btrfs_find_device_by_path(struct btrfs_fs_info *fs_info,
+				     const char *device_path,
+				     struct btrfs_device **device)
+{
+	int ret = 0;
+	struct btrfs_super_block *disk_super;
+	u64 devid;
+	u8 *dev_uuid;
+	struct block_device *bdev;
+	struct buffer_head *bh;
+
+	*device = NULL;
+	ret = btrfs_get_bdev_and_sb(device_path, FMODE_READ,
+				    fs_info->bdev_holder, 0, &bdev, &bh);
+	if (ret)
+		return ret;
+	disk_super = (struct btrfs_super_block *)bh->b_data;
+	devid = btrfs_stack_device_id(&disk_super->dev_item);
+	dev_uuid = disk_super->dev_item.uuid;
+	*device = btrfs_find_device(fs_info->fs_devices, devid, dev_uuid,
+				    disk_super->fsid, true);
+	brelse(bh);
+	if (!*device)
+		ret = -ENOENT;
+	blkdev_put(bdev, FMODE_READ);
+	return ret;
+}
+
+int btrfs_find_device_missing_or_by_path(struct btrfs_fs_info *fs_info,
+					 const char *device_path,
+					 struct btrfs_device **device)
+{
+	*device = NULL;
+	if (strcmp(device_path, "missing") == 0) {
+		struct list_head *devices;
+		struct btrfs_device *tmp;
+
+		devices = &fs_info->fs_devices->devices;
+		list_for_each_entry(tmp, devices, dev_list) {
+			if (test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
+					&tmp->dev_state) && !tmp->bdev) {
+				*device = tmp;
+				break;
+			}
+		}
+
+		if (!*device)
+			return BTRFS_ERROR_DEV_MISSING_NOT_FOUND;
+
+		return 0;
+	} else {
+		return btrfs_find_device_by_path(fs_info, device_path, device);
+	}
+}
+
+/*
+ * Lookup a device given by device id, or the path if the id is 0.
+ */
+int btrfs_find_device_by_devspec(struct btrfs_fs_info *fs_info, u64 devid,
+				 const char *devpath,
+				 struct btrfs_device **device)
+{
+	int ret;
+
+	if (devid) {
+		ret = 0;
+		*device = btrfs_find_device(fs_info->fs_devices, devid,
+					    NULL, NULL, true);
+		if (!*device)
+			ret = -ENOENT;
+	} else {
+		if (!devpath || !devpath[0])
+			return -EINVAL;
+
+		ret = btrfs_find_device_missing_or_by_path(fs_info, devpath,
+							   device);
+	}
+	return ret;
+}
+
+/*
+ * does all the dirty work required for changing file system's UUID.
+ */
+static int btrfs_prepare_sprout(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_fs_devices *old_devices;
+	struct btrfs_fs_devices *seed_devices;
+	struct btrfs_super_block *disk_super = fs_info->super_copy;
+	struct btrfs_device *device;
+	u64 super_flags;
+
+	lockdep_assert_held(&uuid_mutex);
+	if (!fs_devices->seeding)
+		return -EINVAL;
+
+	seed_devices = alloc_fs_devices(NULL);
+	if (IS_ERR(seed_devices))
+		return PTR_ERR(seed_devices);
+
+	old_devices = clone_fs_devices(fs_devices);
+	if (IS_ERR(old_devices)) {
+		kfree(seed_devices);
+		return PTR_ERR(old_devices);
+	}
+
+	list_add(&old_devices->fs_list, &fs_uuids);
+
+	memcpy(seed_devices, fs_devices, sizeof(*seed_devices));
+	seed_devices->opened = 1;
+	INIT_LIST_HEAD(&seed_devices->devices);
+	INIT_LIST_HEAD(&seed_devices->alloc_list);
+	mutex_init(&seed_devices->device_list_mutex);
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_splice_init_rcu(&fs_devices->devices, &seed_devices->devices,
+			      synchronize_rcu);
+	list_for_each_entry(device, &seed_devices->devices, dev_list)
+		device->fs_devices = seed_devices;
+
+	mutex_lock(&fs_info->chunk_mutex);
+	list_splice_init(&fs_devices->alloc_list, &seed_devices->alloc_list);
+	mutex_unlock(&fs_info->chunk_mutex);
+
+	fs_devices->seeding = 0;
+	fs_devices->num_devices = 0;
+	fs_devices->open_devices = 0;
+	fs_devices->missing_devices = 0;
+	fs_devices->rotating = 0;
+	fs_devices->seed = seed_devices;
+
+	generate_random_uuid(fs_devices->fsid);
+	memcpy(fs_info->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
+	memcpy(disk_super->fsid, fs_devices->fsid, BTRFS_FSID_SIZE);
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	super_flags = btrfs_super_flags(disk_super) &
+		      ~BTRFS_SUPER_FLAG_SEEDING;
+	btrfs_set_super_flags(disk_super, super_flags);
+
+	return 0;
+}
+
+/*
+ * Store the expected generation for seed devices in device items.
+ */
+static int btrfs_finish_sprout(struct btrfs_trans_handle *trans,
+			       struct btrfs_fs_info *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, true);
+		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;
+}
+
+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 unlocked = 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 (fs_devices->seeding) {
+		seeding_dev = 1;
+		down_write(&sb->s_umount);
+		mutex_lock(&uuid_mutex);
+	}
+
+	filemap_write_and_wait(bdev->bd_inode->i_mapping);
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		if (device->bdev == bdev) {
+			ret = -EEXIST;
+			mutex_unlock(
+				&fs_devices->device_list_mutex);
+			goto error;
+		}
+	}
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	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);
+
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto error_free_device;
+	}
+
+	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;
+	device->fs_info = fs_info;
+	device->bdev = bdev;
+	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) {
+		sb->s_flags &= ~SB_RDONLY;
+		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 = 1;
+
+	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_link(fs_devices, device);
+
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	if (seeding_dev) {
+		mutex_lock(&fs_info->chunk_mutex);
+		ret = init_first_rw_device(trans, fs_info);
+		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) {
+		char fsid_buf[BTRFS_UUID_UNPARSED_SIZE];
+
+		ret = btrfs_finish_sprout(trans, fs_info);
+		if (ret) {
+			btrfs_abort_transaction(trans, ret);
+			goto error_sysfs;
+		}
+
+		/* Sprouting would change fsid of the mounted root,
+		 * so rename the fsid on the sysfs
+		 */
+		snprintf(fsid_buf, BTRFS_UUID_UNPARSED_SIZE, "%pU",
+						fs_info->fsid);
+		if (kobject_rename(&fs_devices->fsid_kobj, fsid_buf))
+			btrfs_warn(fs_info,
+				   "sysfs: failed to create fsid for sprout");
+	}
+
+	ret = btrfs_commit_transaction(trans);
+
+	if (seeding_dev) {
+		mutex_unlock(&uuid_mutex);
+		up_write(&sb->s_umount);
+		unlocked = true;
+
+		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);
+	}
+
+	/* Update ctime/mtime for libblkid */
+	update_dev_time(device_path);
+	return ret;
+
+error_sysfs:
+	btrfs_sysfs_rm_device_link(fs_devices, 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)
+		sb->s_flags |= SB_RDONLY;
+	if (trans)
+		btrfs_end_transaction(trans);
+error_free_device:
+	btrfs_free_device(device);
+error:
+	blkdev_put(bdev, FMODE_EXCL);
+	if (seeding_dev && !unlocked) {
+		mutex_unlock(&uuid_mutex);
+		up_write(&sb->s_umount);
+	}
+	return ret;
+}
+
+static noinline int btrfs_update_device(struct btrfs_trans_handle *trans,
+					struct btrfs_device *device)
+{
+	int ret;
+	struct btrfs_path *path;
+	struct btrfs_root *root = device->fs_info->chunk_root;
+	struct btrfs_dev_item *dev_item;
+	struct extent_buffer *leaf;
+	struct btrfs_key key;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.type = BTRFS_DEV_ITEM_KEY;
+	key.offset = device->devid;
+
+	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
+	if (ret < 0)
+		goto out;
+
+	if (ret > 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	dev_item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_dev_item);
+
+	btrfs_set_device_id(leaf, dev_item, device->devid);
+	btrfs_set_device_type(leaf, dev_item, device->type);
+	btrfs_set_device_io_align(leaf, dev_item, device->io_align);
+	btrfs_set_device_io_width(leaf, dev_item, device->io_width);
+	btrfs_set_device_sector_size(leaf, dev_item, device->sector_size);
+	btrfs_set_device_total_bytes(leaf, dev_item,
+				     btrfs_device_get_disk_total_bytes(device));
+	btrfs_set_device_bytes_used(leaf, dev_item,
+				    btrfs_device_get_bytes_used(device));
+	btrfs_mark_buffer_dirty(leaf);
+
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+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;
+	struct btrfs_fs_devices *fs_devices;
+	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;
+	}
+
+	fs_devices = fs_info->fs_devices;
+
+	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->resized_list))
+		list_add_tail(&device->resized_list,
+			      &fs_devices->resized_devices);
+	mutex_unlock(&fs_info->chunk_mutex);
+
+	return btrfs_update_device(trans, device);
+}
+
+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 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;
+
+	mutex_lock(&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;
+		}
+	}
+	mutex_unlock(&fs_info->chunk_mutex);
+	return ret;
+}
+
+static struct extent_map *get_chunk_map(struct btrfs_fs_info *fs_info,
+					u64 logical, u64 length)
+{
+	struct extent_map_tree *em_tree;
+	struct extent_map *em;
+
+	em_tree = &fs_info->mapping_tree.map_tree;
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, logical, length);
+	read_unlock(&em_tree->lock);
+
+	if (!em) {
+		btrfs_crit(fs_info, "unable to find logical %llu length %llu",
+			   logical, length);
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (em->start > logical || em->start + em->len < logical) {
+		btrfs_crit(fs_info,
+			   "found a bad mapping, wanted %llu-%llu, found %llu-%llu",
+			   logical, length, em->start, em->start + em->len);
+		free_extent_map(em);
+		return ERR_PTR(-EINVAL);
+	}
+
+	/* callers are responsible for dropping em's ref. */
+	return em;
+}
+
+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 = 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;
+	mutex_lock(&fs_info->chunk_mutex);
+	check_system_chunk(trans, map->type);
+	mutex_unlock(&fs_info->chunk_mutex);
+
+	/*
+	 * Take the device list mutex to prevent races with the final phase of
+	 * a device replace operation that replaces the device object associated
+	 * with map stripes (dev-replace.c:btrfs_dev_replace_finishing()).
+	 */
+	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);
+		}
+
+		if (map->stripes[i].dev) {
+			ret = btrfs_update_device(trans, map->stripes[i].dev);
+			if (ret) {
+				mutex_unlock(&fs_devices->device_list_mutex);
+				btrfs_abort_transaction(trans, ret);
+				goto out;
+			}
+		}
+	}
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	ret = btrfs_free_chunk(trans, chunk_offset);
+	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;
+		}
+	}
+
+	ret = btrfs_remove_block_group(trans, chunk_offset, em);
+	if (ret) {
+		btrfs_abort_transaction(trans, ret);
+		goto out;
+	}
+
+out:
+	/* once for us */
+	free_extent_map(em);
+	return ret;
+}
+
+static int btrfs_relocate_chunk(struct btrfs_fs_info *fs_info, u64 chunk_offset)
+{
+	struct btrfs_root *root = fs_info->chunk_root;
+	struct btrfs_trans_handle *trans;
+	int ret;
+
+	/*
+	 * Prevent races with automatic removal of unused block groups.
+	 * After we relocate and before we remove the chunk with offset
+	 * chunk_offset, automatic removal of the block group can kick in,
+	 * resulting in a failure when calling btrfs_remove_chunk() below.
+	 *
+	 * Make sure to acquire this mutex before doing a tree search (dev
+	 * or chunk trees) to find chunks. Otherwise the cleaner kthread might
+	 * call btrfs_remove_chunk() (through btrfs_delete_unused_bgs()) after
+	 * we release the path used to search the chunk/dev tree and before
+	 * the current task acquires this mutex and calls us.
+	 */
+	lockdep_assert_held(&fs_info->delete_unused_bgs_mutex);
+
+	ret = btrfs_can_relocate(fs_info, chunk_offset);
+	if (ret)
+		return -ENOSPC;
+
+	/* step one, relocate all the extents inside this chunk */
+	btrfs_scrub_pause(fs_info);
+	ret = btrfs_relocate_block_group(fs_info, chunk_offset);
+	btrfs_scrub_continue(fs_info);
+	if (ret)
+		return ret;
+
+	/*
+	 * We add the kobjects here (and after forcing data chunk creation)
+	 * since relocation is the only place we'll create chunks of a new
+	 * type at runtime.  The only place where we'll remove the last
+	 * chunk of a type is the call immediately below this one.  Even
+	 * so, we're protected against races with the cleaner thread since
+	 * we're covered by the delete_unused_bgs_mutex.
+	 */
+	btrfs_add_raid_kobjects(fs_info);
+
+	trans = btrfs_start_trans_remove_block_group(root->fs_info,
+						     chunk_offset);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		btrfs_handle_fs_error(root->fs_info, ret, NULL);
+		return ret;
+	}
+
+	/*
+	 * step two, delete the device extents and the
+	 * chunk tree entries
+	 */
+	ret = btrfs_remove_chunk(trans, chunk_offset);
+	btrfs_end_transaction(trans);
+	return ret;
+}
+
+static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *chunk_root = fs_info->chunk_root;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_chunk *chunk;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	u64 chunk_type;
+	bool retried = false;
+	int failed = 0;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+again:
+	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+	key.offset = (u64)-1;
+	key.type = BTRFS_CHUNK_ITEM_KEY;
+
+	while (1) {
+		mutex_lock(&fs_info->delete_unused_bgs_mutex);
+		ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
+		if (ret < 0) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			goto error;
+		}
+		BUG_ON(ret == 0); /* Corruption */
+
+		ret = btrfs_previous_item(chunk_root, path, key.objectid,
+					  key.type);
+		if (ret)
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+		if (ret < 0)
+			goto error;
+		if (ret > 0)
+			break;
+
+		leaf = path->nodes[0];
+		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
+
+		chunk = btrfs_item_ptr(leaf, path->slots[0],
+				       struct btrfs_chunk);
+		chunk_type = btrfs_chunk_type(leaf, chunk);
+		btrfs_release_path(path);
+
+		if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM) {
+			ret = btrfs_relocate_chunk(fs_info, found_key.offset);
+			if (ret == -ENOSPC)
+				failed++;
+			else
+				BUG_ON(ret);
+		}
+		mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+
+		if (found_key.offset == 0)
+			break;
+		key.offset = found_key.offset - 1;
+	}
+	ret = 0;
+	if (failed && !retried) {
+		failed = 0;
+		retried = true;
+		goto again;
+	} else if (WARN_ON(failed && retried)) {
+		ret = -ENOSPC;
+	}
+error:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * return 1 : allocate a data chunk successfully,
+ * return <0: errors during allocating a data chunk,
+ * return 0 : no need to allocate a data chunk.
+ */
+static int btrfs_may_alloc_data_chunk(struct btrfs_fs_info *fs_info,
+				      u64 chunk_offset)
+{
+	struct btrfs_block_group_cache *cache;
+	u64 bytes_used;
+	u64 chunk_type;
+
+	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+	ASSERT(cache);
+	chunk_type = cache->flags;
+	btrfs_put_block_group(cache);
+
+	if (chunk_type & BTRFS_BLOCK_GROUP_DATA) {
+		spin_lock(&fs_info->data_sinfo->lock);
+		bytes_used = fs_info->data_sinfo->bytes_used;
+		spin_unlock(&fs_info->data_sinfo->lock);
+
+		if (!bytes_used) {
+			struct btrfs_trans_handle *trans;
+			int ret;
+
+			trans =	btrfs_join_transaction(fs_info->tree_root);
+			if (IS_ERR(trans))
+				return PTR_ERR(trans);
+
+			ret = btrfs_force_chunk_alloc(trans,
+						      BTRFS_BLOCK_GROUP_DATA);
+			btrfs_end_transaction(trans);
+			if (ret < 0)
+				return ret;
+
+			btrfs_add_raid_kobjects(fs_info);
+
+			return 1;
+		}
+	}
+	return 0;
+}
+
+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 int del_balance_item(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	int ret, err;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	trans = btrfs_start_transaction(root, 0);
+	if (IS_ERR(trans)) {
+		btrfs_free_path(path);
+		return PTR_ERR(trans);
+	}
+
+	key.objectid = BTRFS_BALANCE_OBJECTID;
+	key.type = BTRFS_TEMPORARY_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	ret = btrfs_del_item(trans, root, path);
+out:
+	btrfs_free_path(path);
+	err = btrfs_commit_transaction(trans);
+	if (err && !ret)
+		ret = err;
+	return ret;
+}
+
+/*
+ * This is a heuristic used to reduce the number of chunks balanced on
+ * resume after balance was interrupted.
+ */
+static void update_balance_args(struct btrfs_balance_control *bctl)
+{
+	/*
+	 * Turn on soft mode for chunk types that were being converted.
+	 */
+	if (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT)
+		bctl->data.flags |= BTRFS_BALANCE_ARGS_SOFT;
+	if (bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT)
+		bctl->sys.flags |= BTRFS_BALANCE_ARGS_SOFT;
+	if (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT)
+		bctl->meta.flags |= BTRFS_BALANCE_ARGS_SOFT;
+
+	/*
+	 * Turn on usage filter if is not already used.  The idea is
+	 * that chunks that we have already balanced should be
+	 * reasonably full.  Don't do it for chunks that are being
+	 * converted - that will keep us from relocating unconverted
+	 * (albeit full) chunks.
+	 */
+	if (!(bctl->data.flags & BTRFS_BALANCE_ARGS_USAGE) &&
+	    !(bctl->data.flags & BTRFS_BALANCE_ARGS_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;
+	}
+}
+
+/*
+ * Clear the balance status in fs_info and delete the balance item from disk.
+ */
+static void reset_balance_state(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
+	int ret;
+
+	BUG_ON(!fs_info->balance_ctl);
+
+	spin_lock(&fs_info->balance_lock);
+	fs_info->balance_ctl = NULL;
+	spin_unlock(&fs_info->balance_lock);
+
+	kfree(bctl);
+	ret = del_balance_item(fs_info);
+	if (ret)
+		btrfs_handle_fs_error(fs_info, ret, NULL);
+}
+
+/*
+ * Balance filters.  Return 1 if chunk should be filtered out
+ * (should not be balanced).
+ */
+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 chunk_usage_range_filter(struct btrfs_fs_info *fs_info, u64 chunk_offset,
+			      struct btrfs_balance_args *bargs)
+{
+	struct btrfs_block_group_cache *cache;
+	u64 chunk_used;
+	u64 user_thresh_min;
+	u64 user_thresh_max;
+	int ret = 1;
+
+	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+	chunk_used = btrfs_block_group_used(&cache->item);
+
+	if (bargs->usage_min == 0)
+		user_thresh_min = 0;
+	else
+		user_thresh_min = div_factor_fine(cache->key.offset,
+					bargs->usage_min);
+
+	if (bargs->usage_max == 0)
+		user_thresh_max = 1;
+	else if (bargs->usage_max > 100)
+		user_thresh_max = cache->key.offset;
+	else
+		user_thresh_max = div_factor_fine(cache->key.offset,
+					bargs->usage_max);
+
+	if (user_thresh_min <= chunk_used && chunk_used < user_thresh_max)
+		ret = 0;
+
+	btrfs_put_block_group(cache);
+	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 *cache;
+	u64 chunk_used, user_thresh;
+	int ret = 1;
+
+	cache = btrfs_lookup_block_group(fs_info, chunk_offset);
+	chunk_used = btrfs_block_group_used(&cache->item);
+
+	if (bargs->usage_min == 0)
+		user_thresh = 1;
+	else if (bargs->usage > 100)
+		user_thresh = cache->key.offset;
+	else
+		user_thresh = div_factor_fine(cache->key.offset,
+					      bargs->usage);
+
+	if (chunk_used < user_thresh)
+		ret = 0;
+
+	btrfs_put_block_group(cache);
+	return ret;
+}
+
+static int chunk_devid_filter(struct extent_buffer *leaf,
+			      struct btrfs_chunk *chunk,
+			      struct btrfs_balance_args *bargs)
+{
+	struct btrfs_stripe *stripe;
+	int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+	int i;
+
+	for (i = 0; i < num_stripes; i++) {
+		stripe = btrfs_stripe_nr(chunk, i);
+		if (btrfs_stripe_devid(leaf, stripe) == bargs->devid)
+			return 0;
+	}
+
+	return 1;
+}
+
+/* [pstart, pend) */
+static int chunk_drange_filter(struct extent_buffer *leaf,
+			       struct btrfs_chunk *chunk,
+			       struct btrfs_balance_args *bargs)
+{
+	struct btrfs_stripe *stripe;
+	int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+	u64 stripe_offset;
+	u64 stripe_length;
+	int factor;
+	int i;
+
+	if (!(bargs->flags & BTRFS_BALANCE_ARGS_DEVID))
+		return 0;
+
+	if (btrfs_chunk_type(leaf, chunk) & (BTRFS_BLOCK_GROUP_DUP |
+	     BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10)) {
+		factor = num_stripes / 2;
+	} else if (btrfs_chunk_type(leaf, chunk) & BTRFS_BLOCK_GROUP_RAID5) {
+		factor = num_stripes - 1;
+	} else if (btrfs_chunk_type(leaf, chunk) & BTRFS_BLOCK_GROUP_RAID6) {
+		factor = num_stripes - 2;
+	} else {
+		factor = num_stripes;
+	}
+
+	for (i = 0; i < num_stripes; i++) {
+		stripe = btrfs_stripe_nr(chunk, i);
+		if (btrfs_stripe_devid(leaf, stripe) != bargs->devid)
+			continue;
+
+		stripe_offset = btrfs_stripe_offset(leaf, stripe);
+		stripe_length = btrfs_chunk_length(leaf, chunk);
+		stripe_length = div_u64(stripe_length, factor);
+
+		if (stripe_offset < bargs->pend &&
+		    stripe_offset + stripe_length > bargs->pstart)
+			return 0;
+	}
+
+	return 1;
+}
+
+/* [vstart, vend) */
+static int chunk_vrange_filter(struct extent_buffer *leaf,
+			       struct btrfs_chunk *chunk,
+			       u64 chunk_offset,
+			       struct btrfs_balance_args *bargs)
+{
+	if (chunk_offset < bargs->vend &&
+	    chunk_offset + btrfs_chunk_length(leaf, chunk) > bargs->vstart)
+		/* at least part of the chunk is inside this vrange */
+		return 0;
+
+	return 1;
+}
+
+static int chunk_stripes_range_filter(struct extent_buffer *leaf,
+			       struct btrfs_chunk *chunk,
+			       struct btrfs_balance_args *bargs)
+{
+	int num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+
+	if (bargs->stripes_min <= num_stripes
+			&& num_stripes <= bargs->stripes_max)
+		return 0;
+
+	return 1;
+}
+
+static int chunk_soft_convert_filter(u64 chunk_type,
+				     struct btrfs_balance_args *bargs)
+{
+	if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
+		return 0;
+
+	chunk_type = chunk_to_extended(chunk_type) &
+				BTRFS_EXTENDED_PROFILE_MASK;
+
+	if (bargs->target == chunk_type)
+		return 1;
+
+	return 0;
+}
+
+static int should_balance_chunk(struct btrfs_fs_info *fs_info,
+				struct extent_buffer *leaf,
+				struct btrfs_chunk *chunk, u64 chunk_offset)
+{
+	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
+	struct btrfs_balance_args *bargs = NULL;
+	u64 chunk_type = btrfs_chunk_type(leaf, chunk);
+
+	/* type filter */
+	if (!((chunk_type & BTRFS_BLOCK_GROUP_TYPE_MASK) &
+	      (bctl->flags & BTRFS_BALANCE_TYPE_MASK))) {
+		return 0;
+	}
+
+	if (chunk_type & BTRFS_BLOCK_GROUP_DATA)
+		bargs = &bctl->data;
+	else if (chunk_type & BTRFS_BLOCK_GROUP_SYSTEM)
+		bargs = &bctl->sys;
+	else if (chunk_type & BTRFS_BLOCK_GROUP_METADATA)
+		bargs = &bctl->meta;
+
+	/* profiles filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_PROFILES) &&
+	    chunk_profiles_filter(chunk_type, bargs)) {
+		return 0;
+	}
+
+	/* usage filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE) &&
+	    chunk_usage_filter(fs_info, chunk_offset, bargs)) {
+		return 0;
+	} else if ((bargs->flags & BTRFS_BALANCE_ARGS_USAGE_RANGE) &&
+	    chunk_usage_range_filter(fs_info, chunk_offset, bargs)) {
+		return 0;
+	}
+
+	/* devid filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_DEVID) &&
+	    chunk_devid_filter(leaf, chunk, bargs)) {
+		return 0;
+	}
+
+	/* drange filter, makes sense only with devid filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_DRANGE) &&
+	    chunk_drange_filter(leaf, chunk, bargs)) {
+		return 0;
+	}
+
+	/* vrange filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_VRANGE) &&
+	    chunk_vrange_filter(leaf, chunk, chunk_offset, bargs)) {
+		return 0;
+	}
+
+	/* stripes filter */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_STRIPES_RANGE) &&
+	    chunk_stripes_range_filter(leaf, chunk, bargs)) {
+		return 0;
+	}
+
+	/* soft profile changing mode */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_SOFT) &&
+	    chunk_soft_convert_filter(chunk_type, bargs)) {
+		return 0;
+	}
+
+	/*
+	 * limited by count, must be the last filter
+	 */
+	if ((bargs->flags & BTRFS_BALANCE_ARGS_LIMIT)) {
+		if (bargs->limit == 0)
+			return 0;
+		else
+			bargs->limit--;
+	} else if ((bargs->flags & BTRFS_BALANCE_ARGS_LIMIT_RANGE)) {
+		/*
+		 * Same logic as the 'limit' filter; the minimum cannot be
+		 * determined here because we do not have the global information
+		 * about the count of all chunks that satisfy the filters.
+		 */
+		if (bargs->limit_max == 0)
+			return 0;
+		else
+			bargs->limit_max--;
+	}
+
+	return 1;
+}
+
+static int __btrfs_balance(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_balance_control *bctl = fs_info->balance_ctl;
+	struct btrfs_root *chunk_root = fs_info->chunk_root;
+	struct btrfs_root *dev_root = fs_info->dev_root;
+	struct list_head *devices;
+	struct btrfs_device *device;
+	u64 old_size;
+	u64 size_to_free;
+	u64 chunk_type;
+	struct btrfs_chunk *chunk;
+	struct btrfs_path *path = NULL;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_trans_handle *trans;
+	struct extent_buffer *leaf;
+	int slot;
+	int ret;
+	int enospc_errors = 0;
+	bool counting = true;
+	/* 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;
+
+	/* step one make some room on all the devices */
+	devices = &fs_info->fs_devices->devices;
+	list_for_each_entry(device, devices, dev_list) {
+		old_size = btrfs_device_get_total_bytes(device);
+		size_to_free = div_factor(old_size, 1);
+		size_to_free = min_t(u64, size_to_free, SZ_1M);
+		if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) ||
+		    btrfs_device_get_total_bytes(device) -
+		    btrfs_device_get_bytes_used(device) > size_to_free ||
+		    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
+			continue;
+
+		ret = btrfs_shrink_device(device, old_size - size_to_free);
+		if (ret == -ENOSPC)
+			break;
+		if (ret) {
+			/* btrfs_shrink_device never returns ret > 0 */
+			WARN_ON(ret > 0);
+			goto error;
+		}
+
+		trans = btrfs_start_transaction(dev_root, 0);
+		if (IS_ERR(trans)) {
+			ret = PTR_ERR(trans);
+			btrfs_info_in_rcu(fs_info,
+		 "resize: unable to start transaction after shrinking device %s (error %d), old size %llu, new size %llu",
+					  rcu_str_deref(device->name), ret,
+					  old_size, old_size - size_to_free);
+			goto error;
+		}
+
+		ret = btrfs_grow_device(trans, device, old_size);
+		if (ret) {
+			btrfs_end_transaction(trans);
+			/* btrfs_grow_device never returns ret > 0 */
+			WARN_ON(ret > 0);
+			btrfs_info_in_rcu(fs_info,
+		 "resize: unable to grow device after shrinking device %s (error %d), old size %llu, new size %llu",
+					  rcu_str_deref(device->name), ret,
+					  old_size, old_size - size_to_free);
+			goto error;
+		}
+
+		btrfs_end_transaction(trans);
+	}
+
+	/* step two, relocate all the chunks */
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	/* zero out stat counters */
+	spin_lock(&fs_info->balance_lock);
+	memset(&bctl->stat, 0, sizeof(bctl->stat));
+	spin_unlock(&fs_info->balance_lock);
+again:
+	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->delete_unused_bgs_mutex);
+		ret = btrfs_search_slot(NULL, chunk_root, &key, path, 0, 0);
+		if (ret < 0) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+			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(fs_info, leaf, chunk,
+					   found_key.offset);
+
+		btrfs_release_path(path);
+		if (!ret) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			goto loop;
+		}
+
+		if (counting) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+				goto error;
+			} else if (ret == 1) {
+				chunk_reserved = 1;
+			}
+		}
+
+		ret = btrfs_relocate_chunk(fs_info, found_key.offset);
+		mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+		if (ret && ret != -ENOSPC)
+			goto error;
+		if (ret == -ENOSPC) {
+			enospc_errors++;
+		} else {
+			spin_lock(&fs_info->balance_lock);
+			bctl->stat.completed++;
+			spin_unlock(&fs_info->balance_lock);
+		}
+loop:
+		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;
+}
+
+/**
+ * alloc_profile_is_valid - see if a given profile is valid and reduced
+ * @flags: profile to validate
+ * @extended: if true @flags is treated as an extended profile
+ */
+static int alloc_profile_is_valid(u64 flags, int extended)
+{
+	u64 mask = (extended ? BTRFS_EXTENDED_PROFILE_MASK :
+			       BTRFS_BLOCK_GROUP_PROFILE_MASK);
+
+	flags &= ~BTRFS_BLOCK_GROUP_TYPE_MASK;
+
+	/* 1) check that all other bits are zeroed */
+	if (flags & ~mask)
+		return 0;
+
+	/* 2) see if profile is reduced */
+	if (flags == 0)
+		return !extended; /* "0" is valid for usual profiles */
+
+	/* true if exactly one bit set */
+	return (flags & (flags - 1)) == 0;
+}
+
+static inline int balance_need_close(struct btrfs_fs_info *fs_info)
+{
+	/* cancel requested || normal exit path */
+	return atomic_read(&fs_info->balance_cancel_req) ||
+		(atomic_read(&fs_info->balance_pause_req) == 0 &&
+		 atomic_read(&fs_info->balance_cancel_req) == 0);
+}
+
+/* Non-zero return value signifies invalidity */
+static inline int validate_convert_profile(struct btrfs_balance_args *bctl_arg,
+		u64 allowed)
+{
+	return ((bctl_arg->flags & BTRFS_BALANCE_ARGS_CONVERT) &&
+		(!alloc_profile_is_valid(bctl_arg->target, 1) ||
+		 (bctl_arg->target & ~allowed)));
+}
+
+/*
+ * Should be called with balance mutexe held
+ */
+int btrfs_balance(struct btrfs_fs_info *fs_info,
+		  struct btrfs_balance_control *bctl,
+		  struct btrfs_ioctl_balance_args *bargs)
+{
+	u64 meta_target, data_target;
+	u64 allowed;
+	int mixed = 0;
+	int ret;
+	u64 num_devices;
+	unsigned seq;
+	bool reducing_integrity;
+
+	if (btrfs_fs_closing(fs_info) ||
+	    atomic_read(&fs_info->balance_pause_req) ||
+	    atomic_read(&fs_info->balance_cancel_req)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	allowed = btrfs_super_incompat_flags(fs_info->super_copy);
+	if (allowed & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS)
+		mixed = 1;
+
+	/*
+	 * In case of mixed groups both data and meta should be picked,
+	 * and identical options should be given for both of them.
+	 */
+	allowed = BTRFS_BALANCE_DATA | BTRFS_BALANCE_METADATA;
+	if (mixed && (bctl->flags & allowed)) {
+		if (!(bctl->flags & BTRFS_BALANCE_DATA) ||
+		    !(bctl->flags & BTRFS_BALANCE_METADATA) ||
+		    memcmp(&bctl->data, &bctl->meta, sizeof(bctl->data))) {
+			btrfs_err(fs_info,
+	  "balance: mixed groups data and metadata options must be the same");
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	num_devices = fs_info->fs_devices->num_devices;
+	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace)) {
+		BUG_ON(num_devices < 1);
+		num_devices--;
+	}
+	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+	allowed = BTRFS_AVAIL_ALLOC_BIT_SINGLE | BTRFS_BLOCK_GROUP_DUP;
+	if (num_devices > 1)
+		allowed |= (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID1);
+	if (num_devices > 2)
+		allowed |= BTRFS_BLOCK_GROUP_RAID5;
+	if (num_devices > 3)
+		allowed |= (BTRFS_BLOCK_GROUP_RAID10 |
+			    BTRFS_BLOCK_GROUP_RAID6);
+	if (validate_convert_profile(&bctl->data, allowed)) {
+		int index = btrfs_bg_flags_to_raid_index(bctl->data.target);
+
+		btrfs_err(fs_info,
+			  "balance: invalid convert data profile %s",
+			  get_raid_name(index));
+		ret = -EINVAL;
+		goto out;
+	}
+	if (validate_convert_profile(&bctl->meta, allowed)) {
+		int index = btrfs_bg_flags_to_raid_index(bctl->meta.target);
+
+		btrfs_err(fs_info,
+			  "balance: invalid convert metadata profile %s",
+			  get_raid_name(index));
+		ret = -EINVAL;
+		goto out;
+	}
+	if (validate_convert_profile(&bctl->sys, allowed)) {
+		int index = btrfs_bg_flags_to_raid_index(bctl->sys.target);
+
+		btrfs_err(fs_info,
+			  "balance: invalid convert system profile %s",
+			  get_raid_name(index));
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* allow to reduce meta or sys integrity only if force set */
+	allowed = BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
+			BTRFS_BLOCK_GROUP_RAID10 |
+			BTRFS_BLOCK_GROUP_RAID5 |
+			BTRFS_BLOCK_GROUP_RAID6;
+	do {
+		seq = read_seqbegin(&fs_info->profiles_lock);
+
+		if (((bctl->sys.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
+		     (fs_info->avail_system_alloc_bits & allowed) &&
+		     !(bctl->sys.target & allowed)) ||
+		    ((bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) &&
+		     (fs_info->avail_metadata_alloc_bits & allowed) &&
+		     !(bctl->meta.target & allowed)))
+			reducing_integrity = true;
+		else
+			reducing_integrity = false;
+
+		/* if we're not converting, the target field is uninitialized */
+		meta_target = (bctl->meta.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
+			bctl->meta.target : fs_info->avail_metadata_alloc_bits;
+		data_target = (bctl->data.flags & BTRFS_BALANCE_ARGS_CONVERT) ?
+			bctl->data.target : fs_info->avail_data_alloc_bits;
+	} while (read_seqretry(&fs_info->profiles_lock, seq));
+
+	if (reducing_integrity) {
+		if (bctl->flags & BTRFS_BALANCE_FORCE) {
+			btrfs_info(fs_info,
+				   "balance: force reducing metadata integrity");
+		} else {
+			btrfs_err(fs_info,
+	  "balance: reduces metadata integrity, use --force if you want this");
+			ret = -EINVAL;
+			goto out;
+		}
+	}
+
+	if (btrfs_get_num_tolerated_disk_barrier_failures(meta_target) <
+		btrfs_get_num_tolerated_disk_barrier_failures(data_target)) {
+		int meta_index = btrfs_bg_flags_to_raid_index(meta_target);
+		int data_index = btrfs_bg_flags_to_raid_index(data_target);
+
+		btrfs_warn(fs_info,
+	"balance: metadata profile %s has lower redundancy than data profile %s",
+			   get_raid_name(meta_index), get_raid_name(data_index));
+	}
+
+	ret = insert_balance_item(fs_info, bctl);
+	if (ret && ret != -EEXIST)
+		goto out;
+
+	if (!(bctl->flags & BTRFS_BALANCE_RESUME)) {
+		BUG_ON(ret == -EEXIST);
+		BUG_ON(fs_info->balance_ctl);
+		spin_lock(&fs_info->balance_lock);
+		fs_info->balance_ctl = bctl;
+		spin_unlock(&fs_info->balance_lock);
+	} else {
+		BUG_ON(ret != -EEXIST);
+		spin_lock(&fs_info->balance_lock);
+		update_balance_args(bctl);
+		spin_unlock(&fs_info->balance_lock);
+	}
+
+	ASSERT(!test_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags));
+	set_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
+	mutex_unlock(&fs_info->balance_mutex);
+
+	ret = __btrfs_balance(fs_info);
+
+	mutex_lock(&fs_info->balance_mutex);
+	clear_bit(BTRFS_FS_BALANCE_RUNNING, &fs_info->flags);
+
+	if (bargs) {
+		memset(bargs, 0, sizeof(*bargs));
+		btrfs_update_ioctl_balance_args(fs_info, bargs);
+	}
+
+	if ((ret && ret != -ECANCELED && ret != -ENOSPC) ||
+	    balance_need_close(fs_info)) {
+		reset_balance_state(fs_info);
+		clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+	}
+
+	wake_up(&fs_info->balance_wait_q);
+
+	return ret;
+out:
+	if (bctl->flags & BTRFS_BALANCE_RESUME)
+		reset_balance_state(fs_info);
+	else
+		kfree(bctl);
+	clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+
+	return ret;
+}
+
+static int balance_kthread(void *data)
+{
+	struct btrfs_fs_info *fs_info = data;
+	int ret = 0;
+
+	mutex_lock(&fs_info->balance_mutex);
+	if (fs_info->balance_ctl) {
+		btrfs_info(fs_info, "balance: resuming");
+		ret = btrfs_balance(fs_info, fs_info->balance_ctl, NULL);
+	}
+	mutex_unlock(&fs_info->balance_mutex);
+
+	return ret;
+}
+
+int btrfs_resume_balance_async(struct btrfs_fs_info *fs_info)
+{
+	struct task_struct *tsk;
+
+	mutex_lock(&fs_info->balance_mutex);
+	if (!fs_info->balance_ctl) {
+		mutex_unlock(&fs_info->balance_mutex);
+		return 0;
+	}
+	mutex_unlock(&fs_info->balance_mutex);
+
+	if (btrfs_test_opt(fs_info, SKIP_BALANCE)) {
+		btrfs_info(fs_info, "balance: resume skipped");
+		return 0;
+	}
+
+	/*
+	 * A ro->rw remount sequence should continue with the paused balance
+	 * regardless of who pauses it, system or the user as of now, so set
+	 * the resume flag.
+	 */
+	spin_lock(&fs_info->balance_lock);
+	fs_info->balance_ctl->flags |= BTRFS_BALANCE_RESUME;
+	spin_unlock(&fs_info->balance_lock);
+
+	tsk = kthread_run(balance_kthread, fs_info, "btrfs-balance");
+	return PTR_ERR_OR_ZERO(tsk);
+}
+
+int btrfs_recover_balance(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_balance_control *bctl;
+	struct btrfs_balance_item *item;
+	struct btrfs_disk_balance_args disk_bargs;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_key key;
+	int ret;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	key.objectid = BTRFS_BALANCE_OBJECTID;
+	key.type = BTRFS_TEMPORARY_ITEM_KEY;
+	key.offset = 0;
+
+	ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) { /* ret = -ENOENT; */
+		ret = 0;
+		goto out;
+	}
+
+	bctl = kzalloc(sizeof(*bctl), GFP_NOFS);
+	if (!bctl) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	leaf = path->nodes[0];
+	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_balance_item);
+
+	bctl->flags = btrfs_balance_flags(leaf, item);
+	bctl->flags |= BTRFS_BALANCE_RESUME;
+
+	btrfs_balance_data(leaf, item, &disk_bargs);
+	btrfs_disk_balance_args_to_cpu(&bctl->data, &disk_bargs);
+	btrfs_balance_meta(leaf, item, &disk_bargs);
+	btrfs_disk_balance_args_to_cpu(&bctl->meta, &disk_bargs);
+	btrfs_balance_sys(leaf, item, &disk_bargs);
+	btrfs_disk_balance_args_to_cpu(&bctl->sys, &disk_bargs);
+
+	/*
+	 * This should never happen, as the paused balance state is recovered
+	 * during mount without any chance of other exclusive ops to collide.
+	 *
+	 * This gives the exclusive op status to balance and keeps in paused
+	 * state until user intervention (cancel or umount). If the ownership
+	 * cannot be assigned, show a message but do not fail. The balance
+	 * is in a paused state and must have fs_info::balance_ctl properly
+	 * set up.
+	 */
+	if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags))
+		btrfs_warn(fs_info,
+	"balance: cannot set exclusive op status, resume manually");
+
+	btrfs_release_path(path);
+
+	mutex_lock(&fs_info->balance_mutex);
+	BUG_ON(fs_info->balance_ctl);
+	spin_lock(&fs_info->balance_lock);
+	fs_info->balance_ctl = bctl;
+	spin_unlock(&fs_info->balance_lock);
+	mutex_unlock(&fs_info->balance_mutex);
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+int btrfs_pause_balance(struct btrfs_fs_info *fs_info)
+{
+	int ret = 0;
+
+	mutex_lock(&fs_info->balance_mutex);
+	if (!fs_info->balance_ctl) {
+		mutex_unlock(&fs_info->balance_mutex);
+		return -ENOTCONN;
+	}
+
+	if (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;
+}
+
+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);
+			clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
+			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 int btrfs_uuid_scan_kthread(void *data)
+{
+	struct btrfs_fs_info *fs_info = data;
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_key key;
+	struct btrfs_path *path = NULL;
+	int ret = 0;
+	struct extent_buffer *eb;
+	int slot;
+	struct btrfs_root_item root_item;
+	u32 item_size;
+	struct btrfs_trans_handle *trans = NULL;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key.objectid = 0;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = 0;
+
+	while (1) {
+		ret = btrfs_search_forward(root, &key, path,
+				BTRFS_OLDEST_GENERATION);
+		if (ret) {
+			if (ret > 0)
+				ret = 0;
+			break;
+		}
+
+		if (key.type != BTRFS_ROOT_ITEM_KEY ||
+		    (key.objectid < BTRFS_FIRST_FREE_OBJECTID &&
+		     key.objectid != BTRFS_FS_TREE_OBJECTID) ||
+		    key.objectid > BTRFS_LAST_FREE_OBJECTID)
+			goto skip;
+
+		eb = path->nodes[0];
+		slot = path->slots[0];
+		item_size = btrfs_item_size_nr(eb, slot);
+		if (item_size < sizeof(root_item))
+			goto skip;
+
+		read_extent_buffer(eb, &root_item,
+				   btrfs_item_ptr_offset(eb, slot),
+				   (int)sizeof(root_item));
+		if (btrfs_root_refs(&root_item) == 0)
+			goto skip;
+
+		if (!btrfs_is_empty_uuid(root_item.uuid) ||
+		    !btrfs_is_empty_uuid(root_item.received_uuid)) {
+			if (trans)
+				goto update_tree;
+
+			btrfs_release_path(path);
+			/*
+			 * 1 - subvol uuid item
+			 * 1 - received_subvol uuid item
+			 */
+			trans = btrfs_start_transaction(fs_info->uuid_root, 2);
+			if (IS_ERR(trans)) {
+				ret = PTR_ERR(trans);
+				break;
+			}
+			continue;
+		} else {
+			goto skip;
+		}
+update_tree:
+		btrfs_release_path(path);
+		if (!btrfs_is_empty_uuid(root_item.uuid)) {
+			ret = btrfs_uuid_tree_add(trans, root_item.uuid,
+						  BTRFS_UUID_KEY_SUBVOL,
+						  key.objectid);
+			if (ret < 0) {
+				btrfs_warn(fs_info, "uuid_tree_add failed %d",
+					ret);
+				break;
+			}
+		}
+
+		if (!btrfs_is_empty_uuid(root_item.received_uuid)) {
+			ret = btrfs_uuid_tree_add(trans,
+						  root_item.received_uuid,
+						 BTRFS_UUID_KEY_RECEIVED_SUBVOL,
+						  key.objectid);
+			if (ret < 0) {
+				btrfs_warn(fs_info, "uuid_tree_add failed %d",
+					ret);
+				break;
+			}
+		}
+
+skip:
+		btrfs_release_path(path);
+		if (trans) {
+			ret = btrfs_end_transaction(trans);
+			trans = NULL;
+			if (ret)
+				break;
+		}
+
+		if (key.offset < (u64)-1) {
+			key.offset++;
+		} else if (key.type < BTRFS_ROOT_ITEM_KEY) {
+			key.offset = 0;
+			key.type = BTRFS_ROOT_ITEM_KEY;
+		} else if (key.objectid < (u64)-1) {
+			key.offset = 0;
+			key.type = BTRFS_ROOT_ITEM_KEY;
+			key.objectid++;
+		} else {
+			break;
+		}
+		cond_resched();
+	}
+
+out:
+	btrfs_free_path(path);
+	if (trans && !IS_ERR(trans))
+		btrfs_end_transaction(trans);
+	if (ret)
+		btrfs_warn(fs_info, "btrfs_uuid_scan_kthread failed %d", ret);
+	else
+		set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
+	up(&fs_info->uuid_tree_rescan_sem);
+	return 0;
+}
+
+/*
+ * Callback for btrfs_uuid_tree_iterate().
+ * returns:
+ * 0	check succeeded, the entry is not outdated.
+ * < 0	if an error occurred.
+ * > 0	if the check failed, which means the caller shall remove the entry.
+ */
+static int btrfs_check_uuid_tree_entry(struct btrfs_fs_info *fs_info,
+				       u8 *uuid, u8 type, u64 subid)
+{
+	struct btrfs_key key;
+	int ret = 0;
+	struct btrfs_root *subvol_root;
+
+	if (type != BTRFS_UUID_KEY_SUBVOL &&
+	    type != BTRFS_UUID_KEY_RECEIVED_SUBVOL)
+		goto out;
+
+	key.objectid = subid;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = (u64)-1;
+	subvol_root = btrfs_read_fs_root_no_name(fs_info, &key);
+	if (IS_ERR(subvol_root)) {
+		ret = PTR_ERR(subvol_root);
+		if (ret == -ENOENT)
+			ret = 1;
+		goto out;
+	}
+
+	switch (type) {
+	case BTRFS_UUID_KEY_SUBVOL:
+		if (memcmp(uuid, subvol_root->root_item.uuid, BTRFS_UUID_SIZE))
+			ret = 1;
+		break;
+	case BTRFS_UUID_KEY_RECEIVED_SUBVOL:
+		if (memcmp(uuid, subvol_root->root_item.received_uuid,
+			   BTRFS_UUID_SIZE))
+			ret = 1;
+		break;
+	}
+
+out:
+	return ret;
+}
+
+static int btrfs_uuid_rescan_kthread(void *data)
+{
+	struct btrfs_fs_info *fs_info = (struct btrfs_fs_info *)data;
+	int ret;
+
+	/*
+	 * 1st step is to iterate through the existing UUID tree and
+	 * to delete all entries that contain outdated data.
+	 * 2nd step is to add all missing entries to the UUID tree.
+	 */
+	ret = btrfs_uuid_tree_iterate(fs_info, btrfs_check_uuid_tree_entry);
+	if (ret < 0) {
+		btrfs_warn(fs_info, "iterating uuid_tree failed %d", ret);
+		up(&fs_info->uuid_tree_rescan_sem);
+		return ret;
+	}
+	return btrfs_uuid_scan_kthread(data);
+}
+
+int btrfs_create_uuid_tree(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *tree_root = fs_info->tree_root;
+	struct btrfs_root *uuid_root;
+	struct task_struct *task;
+	int ret;
+
+	/*
+	 * 1 - root node
+	 * 1 - root item
+	 */
+	trans = btrfs_start_transaction(tree_root, 2);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	uuid_root = btrfs_create_tree(trans, fs_info,
+				      BTRFS_UUID_TREE_OBJECTID);
+	if (IS_ERR(uuid_root)) {
+		ret = PTR_ERR(uuid_root);
+		btrfs_abort_transaction(trans, ret);
+		btrfs_end_transaction(trans);
+		return ret;
+	}
+
+	fs_info->uuid_root = uuid_root;
+
+	ret = btrfs_commit_transaction(trans);
+	if (ret)
+		return ret;
+
+	down(&fs_info->uuid_tree_rescan_sem);
+	task = kthread_run(btrfs_uuid_scan_kthread, fs_info, "btrfs-uuid");
+	if (IS_ERR(task)) {
+		/* fs_info->update_uuid_tree_gen remains 0 in all error case */
+		btrfs_warn(fs_info, "failed to start uuid_scan task");
+		up(&fs_info->uuid_tree_rescan_sem);
+		return PTR_ERR(task);
+	}
+
+	return 0;
+}
+
+int btrfs_check_uuid_tree(struct btrfs_fs_info *fs_info)
+{
+	struct task_struct *task;
+
+	down(&fs_info->uuid_tree_rescan_sem);
+	task = kthread_run(btrfs_uuid_rescan_kthread, fs_info, "btrfs-uuid");
+	if (IS_ERR(task)) {
+		/* fs_info->update_uuid_tree_gen remains 0 in all error case */
+		btrfs_warn(fs_info, "failed to start uuid_rescan task");
+		up(&fs_info->uuid_tree_rescan_sem);
+		return PTR_ERR(task);
+	}
+
+	return 0;
+}
+
+/*
+ * shrinking a device means finding all of the device extents past
+ * the new size, and then following the back refs to the chunks.
+ * The chunk relocation code actually frees the device extent
+ */
+int btrfs_shrink_device(struct btrfs_device *device, u64 new_size)
+{
+	struct btrfs_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;
+	bool checked_pending_chunks = 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;
+
+	new_size = round_down(new_size, fs_info->sectorsize);
+	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;
+
+	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);
+	}
+	mutex_unlock(&fs_info->chunk_mutex);
+
+again:
+	key.objectid = device->devid;
+	key.offset = (u64)-1;
+	key.type = BTRFS_DEV_EXTENT_KEY;
+
+	do {
+		mutex_lock(&fs_info->delete_unused_bgs_mutex);
+		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+		if (ret < 0) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			goto done;
+		}
+
+		ret = btrfs_previous_item(root, path, 0, key.type);
+		if (ret)
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+		if (ret < 0)
+			goto done;
+		if (ret) {
+			ret = 0;
+			btrfs_release_path(path);
+			break;
+		}
+
+		l = path->nodes[0];
+		slot = path->slots[0];
+		btrfs_item_key_to_cpu(l, &key, path->slots[0]);
+
+		if (key.objectid != device->devid) {
+			mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+			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->delete_unused_bgs_mutex);
+			goto done;
+		}
+
+		ret = btrfs_relocate_chunk(fs_info, chunk_offset);
+		mutex_unlock(&fs_info->delete_unused_bgs_mutex);
+		if (ret && ret != -ENOSPC)
+			goto done;
+		if (ret == -ENOSPC)
+			failed++;
+	} 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);
+
+	/*
+	 * We checked in the above loop all device extents that were already in
+	 * the device tree. However before we have updated the device's
+	 * total_bytes to the new size, we might have had chunk allocations that
+	 * have not complete yet (new block groups attached to transaction
+	 * handles), and therefore their device extents were not yet in the
+	 * device tree and we missed them in the loop above. So if we have any
+	 * pending chunk using a device extent that overlaps the device range
+	 * that we can not use anymore, commit the current transaction and
+	 * repeat the search on the device tree - this way we guarantee we will
+	 * not have chunks using device extents that end beyond 'new_size'.
+	 */
+	if (!checked_pending_chunks) {
+		u64 start = new_size;
+		u64 len = old_size - new_size;
+
+		if (contains_pending_extent(trans->transaction, device,
+					    &start, len)) {
+			mutex_unlock(&fs_info->chunk_mutex);
+			checked_pending_chunks = true;
+			failed = 0;
+			retried = false;
+			ret = btrfs_commit_transaction(trans);
+			if (ret)
+				goto done;
+			goto again;
+		}
+	}
+
+	btrfs_device_set_disk_total_bytes(device, new_size);
+	if (list_empty(&device->resized_list))
+		list_add_tail(&device->resized_list,
+			      &fs_info->fs_devices->resized_devices);
+
+	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;
+}
+
+static int btrfs_add_system_chunk(struct btrfs_fs_info *fs_info,
+			   struct btrfs_key *key,
+			   struct btrfs_chunk *chunk, int item_size)
+{
+	struct btrfs_super_block *super_copy = fs_info->super_copy;
+	struct btrfs_disk_key disk_key;
+	u32 array_size;
+	u8 *ptr;
+
+	mutex_lock(&fs_info->chunk_mutex);
+	array_size = btrfs_super_sys_array_size(super_copy);
+	if (array_size + item_size + sizeof(disk_key)
+			> BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
+		mutex_unlock(&fs_info->chunk_mutex);
+		return -EFBIG;
+	}
+
+	ptr = super_copy->sys_chunk_array + array_size;
+	btrfs_cpu_key_to_disk(&disk_key, key);
+	memcpy(ptr, &disk_key, sizeof(disk_key));
+	ptr += sizeof(disk_key);
+	memcpy(ptr, chunk, item_size);
+	item_size += sizeof(disk_key);
+	btrfs_set_super_sys_array_size(super_copy, array_size + item_size);
+	mutex_unlock(&fs_info->chunk_mutex);
+
+	return 0;
+}
+
+/*
+ * sort the devices in descending order by max_avail, total_avail
+ */
+static int btrfs_cmp_device_info(const void *a, const void *b)
+{
+	const struct btrfs_device_info *di_a = a;
+	const struct btrfs_device_info *di_b = b;
+
+	if (di_a->max_avail > di_b->max_avail)
+		return -1;
+	if (di_a->max_avail < di_b->max_avail)
+		return 1;
+	if (di_a->total_avail > di_b->total_avail)
+		return -1;
+	if (di_a->total_avail < di_b->total_avail)
+		return 1;
+	return 0;
+}
+
+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 int __btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
+			       u64 start, u64 type)
+{
+	struct btrfs_fs_info *info = trans->fs_info;
+	struct btrfs_fs_devices *fs_devices = info->fs_devices;
+	struct btrfs_device *device;
+	struct map_lookup *map = NULL;
+	struct extent_map_tree *em_tree;
+	struct extent_map *em;
+	struct btrfs_device_info *devices_info = NULL;
+	u64 total_avail;
+	int num_stripes;	/* total number of stripes to allocate */
+	int data_stripes;	/* number of stripes that count for
+				   block group size */
+	int sub_stripes;	/* sub_stripes info for map */
+	int dev_stripes;	/* stripes per dev */
+	int devs_max;		/* max devs to use */
+	int devs_min;		/* min devs needed */
+	int devs_increment;	/* ndevs has to be a multiple of this */
+	int ncopies;		/* how many copies to data has */
+	int ret;
+	u64 max_stripe_size;
+	u64 max_chunk_size;
+	u64 stripe_size;
+	u64 num_bytes;
+	int ndevs;
+	int i;
+	int j;
+	int index;
+
+	BUG_ON(!alloc_profile_is_valid(type, 0));
+
+	if (list_empty(&fs_devices->alloc_list)) {
+		if (btrfs_test_opt(info, ENOSPC_DEBUG))
+			btrfs_debug(info, "%s: no writable device", __func__);
+		return -ENOSPC;
+	}
+
+	index = btrfs_bg_flags_to_raid_index(type);
+
+	sub_stripes = btrfs_raid_array[index].sub_stripes;
+	dev_stripes = btrfs_raid_array[index].dev_stripes;
+	devs_max = btrfs_raid_array[index].devs_max;
+	devs_min = btrfs_raid_array[index].devs_min;
+	devs_increment = btrfs_raid_array[index].devs_increment;
+	ncopies = btrfs_raid_array[index].ncopies;
+
+	if (type & BTRFS_BLOCK_GROUP_DATA) {
+		max_stripe_size = SZ_1G;
+		max_chunk_size = BTRFS_MAX_DATA_CHUNK_SIZE;
+		if (!devs_max)
+			devs_max = BTRFS_MAX_DEVS(info);
+	} else if (type & BTRFS_BLOCK_GROUP_METADATA) {
+		/* for larger filesystems, use larger metadata chunks */
+		if (fs_devices->total_rw_bytes > 50ULL * SZ_1G)
+			max_stripe_size = SZ_1G;
+		else
+			max_stripe_size = SZ_256M;
+		max_chunk_size = max_stripe_size;
+		if (!devs_max)
+			devs_max = BTRFS_MAX_DEVS(info);
+	} else if (type & BTRFS_BLOCK_GROUP_SYSTEM) {
+		max_stripe_size = SZ_32M;
+		max_chunk_size = 2 * max_stripe_size;
+		if (!devs_max)
+			devs_max = BTRFS_MAX_DEVS_SYS_CHUNK;
+	} else {
+		btrfs_err(info, "invalid chunk type 0x%llx requested",
+		       type);
+		BUG_ON(1);
+	}
+
+	/* we don't want a chunk larger than 10% of writeable space */
+	max_chunk_size = min(div_factor(fs_devices->total_rw_bytes, 1),
+			     max_chunk_size);
+
+	devices_info = kcalloc(fs_devices->rw_devices, sizeof(*devices_info),
+			       GFP_NOFS);
+	if (!devices_info)
+		return -ENOMEM;
+
+	/*
+	 * in the first pass through the devices list, we gather information
+	 * about the available holes on each device.
+	 */
+	ndevs = 0;
+	list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
+		u64 max_avail;
+		u64 dev_offset;
+
+		if (!test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state)) {
+			WARN(1, KERN_ERR
+			       "BTRFS: read-only device in alloc_list\n");
+			continue;
+		}
+
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
+					&device->dev_state) ||
+		    test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state))
+			continue;
+
+		if (device->total_bytes > device->bytes_used)
+			total_avail = device->total_bytes - device->bytes_used;
+		else
+			total_avail = 0;
+
+		/* If there is no space on this device, skip it. */
+		if (total_avail == 0)
+			continue;
+
+		ret = find_free_dev_extent(trans, device,
+					   max_stripe_size * dev_stripes,
+					   &dev_offset, &max_avail);
+		if (ret && ret != -ENOSPC)
+			goto error;
+
+		if (ret == 0)
+			max_avail = max_stripe_size * dev_stripes;
+
+		if (max_avail < BTRFS_STRIPE_LEN * dev_stripes) {
+			if (btrfs_test_opt(info, ENOSPC_DEBUG))
+				btrfs_debug(info,
+			"%s: devid %llu has no free space, have=%llu want=%u",
+					    __func__, device->devid, max_avail,
+					    BTRFS_STRIPE_LEN * dev_stripes);
+			continue;
+		}
+
+		if (ndevs == fs_devices->rw_devices) {
+			WARN(1, "%s: found more than %llu devices\n",
+			     __func__, fs_devices->rw_devices);
+			break;
+		}
+		devices_info[ndevs].dev_offset = dev_offset;
+		devices_info[ndevs].max_avail = max_avail;
+		devices_info[ndevs].total_avail = total_avail;
+		devices_info[ndevs].dev = device;
+		++ndevs;
+	}
+
+	/*
+	 * now sort the devices by hole size / available space
+	 */
+	sort(devices_info, ndevs, sizeof(struct btrfs_device_info),
+	     btrfs_cmp_device_info, NULL);
+
+	/* round down to number of usable stripes */
+	ndevs = round_down(ndevs, devs_increment);
+
+	if (ndevs < devs_min) {
+		ret = -ENOSPC;
+		if (btrfs_test_opt(info, ENOSPC_DEBUG)) {
+			btrfs_debug(info,
+	"%s: not enough devices with free space: have=%d minimum required=%d",
+				    __func__, ndevs, devs_min);
+		}
+		goto error;
+	}
+
+	ndevs = min(ndevs, devs_max);
+
+	/*
+	 * The primary goal is to maximize the number of stripes, so use as
+	 * many devices as possible, even if the stripes are not maximum sized.
+	 *
+	 * The DUP profile stores more than one stripe per device, the
+	 * max_avail is the total size so we have to adjust.
+	 */
+	stripe_size = div_u64(devices_info[ndevs - 1].max_avail, dev_stripes);
+	num_stripes = ndevs * dev_stripes;
+
+	/*
+	 * this will have to be fixed for RAID1 and RAID10 over
+	 * more drives
+	 */
+	data_stripes = num_stripes / ncopies;
+
+	if (type & BTRFS_BLOCK_GROUP_RAID5)
+		data_stripes = num_stripes - 1;
+
+	if (type & BTRFS_BLOCK_GROUP_RAID6)
+		data_stripes = num_stripes - 2;
+
+	/*
+	 * Use the number of data stripes to figure out how big this chunk
+	 * is really going to be in terms of logical address space,
+	 * and compare that answer with the max chunk size. If it's higher,
+	 * we try to reduce stripe_size.
+	 */
+	if (stripe_size * data_stripes > max_chunk_size) {
+		/*
+		 * Reduce stripe_size, round it up to a 16MB boundary again and
+		 * then use it, unless it ends up being even bigger than the
+		 * previous value we had already.
+		 */
+		stripe_size = min(round_up(div_u64(max_chunk_size,
+						   data_stripes), SZ_16M),
+				  stripe_size);
+	}
+
+	/* align to BTRFS_STRIPE_LEN */
+	stripe_size = round_down(stripe_size, BTRFS_STRIPE_LEN);
+
+	map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
+	if (!map) {
+		ret = -ENOMEM;
+		goto error;
+	}
+	map->num_stripes = num_stripes;
+
+	for (i = 0; i < ndevs; ++i) {
+		for (j = 0; j < dev_stripes; ++j) {
+			int s = i * dev_stripes + j;
+			map->stripes[s].dev = devices_info[i].dev;
+			map->stripes[s].physical = devices_info[i].dev_offset +
+						   j * stripe_size;
+		}
+	}
+	map->stripe_len = BTRFS_STRIPE_LEN;
+	map->io_align = BTRFS_STRIPE_LEN;
+	map->io_width = BTRFS_STRIPE_LEN;
+	map->type = type;
+	map->sub_stripes = sub_stripes;
+
+	num_bytes = stripe_size * data_stripes;
+
+	trace_btrfs_chunk_alloc(info, map, start, num_bytes);
+
+	em = alloc_extent_map();
+	if (!em) {
+		kfree(map);
+		ret = -ENOMEM;
+		goto error;
+	}
+	set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags);
+	em->map_lookup = map;
+	em->start = start;
+	em->len = num_bytes;
+	em->block_start = 0;
+	em->block_len = em->len;
+	em->orig_block_len = stripe_size;
+
+	em_tree = &info->mapping_tree.map_tree;
+	write_lock(&em_tree->lock);
+	ret = add_extent_mapping(em_tree, em, 0);
+	if (ret) {
+		write_unlock(&em_tree->lock);
+		free_extent_map(em);
+		goto error;
+	}
+
+	list_add_tail(&em->list, &trans->transaction->pending_chunks);
+	refcount_inc(&em->refs);
+	write_unlock(&em_tree->lock);
+
+	ret = btrfs_make_block_group(trans, 0, type, start, num_bytes);
+	if (ret)
+		goto error_del_extent;
+
+	for (i = 0; i < map->num_stripes; i++) {
+		num_bytes = map->stripes[i].dev->bytes_used + stripe_size;
+		btrfs_device_set_bytes_used(map->stripes[i].dev, num_bytes);
+		map->stripes[i].dev->has_pending_chunks = true;
+	}
+
+	atomic64_sub(stripe_size * map->num_stripes, &info->free_chunk_space);
+
+	free_extent_map(em);
+	check_raid56_incompat_flag(info, type);
+
+	kfree(devices_info);
+	return 0;
+
+error_del_extent:
+	write_lock(&em_tree->lock);
+	remove_extent_mapping(em_tree, em);
+	write_unlock(&em_tree->lock);
+
+	/* One for our allocation */
+	free_extent_map(em);
+	/* One for the tree reference */
+	free_extent_map(em);
+	/* One for the pending_chunks list reference */
+	free_extent_map(em);
+error:
+	kfree(devices_info);
+	return ret;
+}
+
+int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
+			     u64 chunk_offset, u64 chunk_size)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct btrfs_root *extent_root = fs_info->extent_root;
+	struct btrfs_root *chunk_root = fs_info->chunk_root;
+	struct btrfs_key key;
+	struct btrfs_device *device;
+	struct btrfs_chunk *chunk;
+	struct btrfs_stripe *stripe;
+	struct extent_map *em;
+	struct map_lookup *map;
+	size_t item_size;
+	u64 dev_offset;
+	u64 stripe_size;
+	int i = 0;
+	int ret = 0;
+
+	em = get_chunk_map(fs_info, chunk_offset, chunk_size);
+	if (IS_ERR(em))
+		return PTR_ERR(em);
+
+	map = em->map_lookup;
+	item_size = btrfs_chunk_item_size(map->num_stripes);
+	stripe_size = em->orig_block_len;
+
+	chunk = kzalloc(item_size, GFP_NOFS);
+	if (!chunk) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Take the device list mutex to 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()).
+	 */
+	mutex_lock(&fs_info->fs_devices->device_list_mutex);
+	for (i = 0; i < map->num_stripes; i++) {
+		device = map->stripes[i].dev;
+		dev_offset = map->stripes[i].physical;
+
+		ret = btrfs_update_device(trans, device);
+		if (ret)
+			break;
+		ret = btrfs_alloc_dev_extent(trans, device, chunk_offset,
+					     dev_offset, stripe_size);
+		if (ret)
+			break;
+	}
+	if (ret) {
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+		goto out;
+	}
+
+	stripe = &chunk->stripe;
+	for (i = 0; i < map->num_stripes; i++) {
+		device = map->stripes[i].dev;
+		dev_offset = map->stripes[i].physical;
+
+		btrfs_set_stack_stripe_devid(stripe, device->devid);
+		btrfs_set_stack_stripe_offset(stripe, dev_offset);
+		memcpy(stripe->dev_uuid, device->uuid, BTRFS_UUID_SIZE);
+		stripe++;
+	}
+	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+
+	btrfs_set_stack_chunk_length(chunk, chunk_size);
+	btrfs_set_stack_chunk_owner(chunk, extent_root->root_key.objectid);
+	btrfs_set_stack_chunk_stripe_len(chunk, map->stripe_len);
+	btrfs_set_stack_chunk_type(chunk, map->type);
+	btrfs_set_stack_chunk_num_stripes(chunk, map->num_stripes);
+	btrfs_set_stack_chunk_io_align(chunk, map->stripe_len);
+	btrfs_set_stack_chunk_io_width(chunk, map->stripe_len);
+	btrfs_set_stack_chunk_sector_size(chunk, fs_info->sectorsize);
+	btrfs_set_stack_chunk_sub_stripes(chunk, map->sub_stripes);
+
+	key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+	key.type = BTRFS_CHUNK_ITEM_KEY;
+	key.offset = chunk_offset;
+
+	ret = btrfs_insert_item(trans, chunk_root, &key, chunk, item_size);
+	if (ret == 0 && map->type & BTRFS_BLOCK_GROUP_SYSTEM) {
+		/*
+		 * TODO: Cleanup of inserted chunk root in case of
+		 * failure.
+		 */
+		ret = btrfs_add_system_chunk(fs_info, &key, chunk, item_size);
+	}
+
+out:
+	kfree(chunk);
+	free_extent_map(em);
+	return ret;
+}
+
+/*
+ * Chunk allocation falls into two parts. The first part does works
+ * that make the new allocated chunk useable, but not do any operation
+ * that modifies the chunk tree. The second part does the works that
+ * require modifying the chunk tree. This division is important for the
+ * bootstrap process of adding storage to a seed btrfs.
+ */
+int btrfs_alloc_chunk(struct btrfs_trans_handle *trans, u64 type)
+{
+	u64 chunk_offset;
+
+	lockdep_assert_held(&trans->fs_info->chunk_mutex);
+	chunk_offset = find_next_chunk(trans->fs_info);
+	return __btrfs_alloc_chunk(trans, chunk_offset, type);
+}
+
+static noinline int init_first_rw_device(struct btrfs_trans_handle *trans,
+					 struct btrfs_fs_info *fs_info)
+{
+	u64 chunk_offset;
+	u64 sys_chunk_offset;
+	u64 alloc_profile;
+	int ret;
+
+	chunk_offset = find_next_chunk(fs_info);
+	alloc_profile = btrfs_metadata_alloc_profile(fs_info);
+	ret = __btrfs_alloc_chunk(trans, chunk_offset, alloc_profile);
+	if (ret)
+		return ret;
+
+	sys_chunk_offset = find_next_chunk(fs_info);
+	alloc_profile = btrfs_system_alloc_profile(fs_info);
+	ret = __btrfs_alloc_chunk(trans, sys_chunk_offset, alloc_profile);
+	return ret;
+}
+
+static inline int btrfs_chunk_max_errors(struct map_lookup *map)
+{
+	int max_errors;
+
+	if (map->type & (BTRFS_BLOCK_GROUP_RAID1 |
+			 BTRFS_BLOCK_GROUP_RAID10 |
+			 BTRFS_BLOCK_GROUP_RAID5)) {
+		max_errors = 1;
+	} else if (map->type & BTRFS_BLOCK_GROUP_RAID6) {
+		max_errors = 2;
+	} else {
+		max_errors = 0;
+	}
+
+	return max_errors;
+}
+
+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 = 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_mapping_init(struct btrfs_mapping_tree *tree)
+{
+	extent_map_tree_init(&tree->map_tree);
+}
+
+void btrfs_mapping_tree_free(struct btrfs_mapping_tree *tree)
+{
+	struct extent_map *em;
+
+	while (1) {
+		write_lock(&tree->map_tree.lock);
+		em = lookup_extent_mapping(&tree->map_tree, 0, (u64)-1);
+		if (em)
+			remove_extent_mapping(&tree->map_tree, em);
+		write_unlock(&tree->map_tree.lock);
+		if (!em)
+			break;
+		/* once for us */
+		free_extent_map(em);
+		/* once for the tree */
+		free_extent_map(em);
+	}
+}
+
+int btrfs_num_copies(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	int ret;
+
+	em = get_chunk_map(fs_info, logical, len);
+	if (IS_ERR(em))
+		/*
+		 * We could return errors for these cases, but that could get
+		 * ugly and we'd probably do the same thing which is just not do
+		 * anything else and exit, so return 1 so the callers don't try
+		 * to use other copies.
+		 */
+		return 1;
+
+	map = em->map_lookup;
+	if (map->type & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1))
+		ret = map->num_stripes;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID10)
+		ret = map->sub_stripes;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID5)
+		ret = 2;
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+		/*
+		 * There could be two corrupted data stripes, we need
+		 * to loop retry in order to rebuild the correct data.
+		 *
+		 * Fail a stripe at a time on every retry except the
+		 * stripe under reconstruction.
+		 */
+		ret = map->num_stripes;
+	else
+		ret = 1;
+	free_extent_map(em);
+
+	btrfs_dev_replace_read_lock(&fs_info->dev_replace);
+	if (btrfs_dev_replace_is_ongoing(&fs_info->dev_replace) &&
+	    fs_info->dev_replace.tgtdev)
+		ret++;
+	btrfs_dev_replace_read_unlock(&fs_info->dev_replace);
+
+	return ret;
+}
+
+unsigned long btrfs_full_stripe_len(struct btrfs_fs_info *fs_info,
+				    u64 logical)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	unsigned long len = fs_info->sectorsize;
+
+	em = get_chunk_map(fs_info, logical, len);
+
+	if (!WARN_ON(IS_ERR(em))) {
+		map = em->map_lookup;
+		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
+			len = map->stripe_len * nr_data_stripes(map);
+		free_extent_map(em);
+	}
+	return len;
+}
+
+int btrfs_is_parity_mirror(struct btrfs_fs_info *fs_info, u64 logical, u64 len)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	int ret = 0;
+
+	em = get_chunk_map(fs_info, logical, len);
+
+	if(!WARN_ON(IS_ERR(em))) {
+		map = em->map_lookup;
+		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
+			ret = 1;
+		free_extent_map(em);
+	}
+	return ret;
+}
+
+static int find_live_mirror(struct btrfs_fs_info *fs_info,
+			    struct map_lookup *map, int first,
+			    int dev_replace_is_ongoing)
+{
+	int i;
+	int num_stripes;
+	int preferred_mirror;
+	int tolerance;
+	struct btrfs_device *srcdev;
+
+	ASSERT((map->type &
+		 (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10)));
+
+	if (map->type & BTRFS_BLOCK_GROUP_RAID10)
+		num_stripes = map->sub_stripes;
+	else
+		num_stripes = map->num_stripes;
+
+	preferred_mirror = first + current->pid % num_stripes;
+
+	if (dev_replace_is_ongoing &&
+	    fs_info->dev_replace.cont_reading_from_srcdev_mode ==
+	     BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID)
+		srcdev = fs_info->dev_replace.srcdev;
+	else
+		srcdev = NULL;
+
+	/*
+	 * try to avoid the drive that is the source drive for a
+	 * dev-replace procedure, only choose it if no other non-missing
+	 * mirror is available
+	 */
+	for (tolerance = 0; tolerance < 2; tolerance++) {
+		if (map->stripes[preferred_mirror].dev->bdev &&
+		    (tolerance || map->stripes[preferred_mirror].dev != srcdev))
+			return preferred_mirror;
+		for (i = first; i < first + num_stripes; i++) {
+			if (map->stripes[i].dev->bdev &&
+			    (tolerance || map->stripes[i].dev != srcdev))
+				return i;
+		}
+	}
+
+	/* we couldn't find one that doesn't fail.  Just return something
+	 * and the io error handling code will clean up eventually
+	 */
+	return preferred_mirror;
+}
+
+static inline int parity_smaller(u64 a, u64 b)
+{
+	return a > b;
+}
+
+/* Bubble-sort the stripe set to put the parity/syndrome stripes last */
+static void sort_parity_stripes(struct btrfs_bio *bbio, int num_stripes)
+{
+	struct btrfs_bio_stripe s;
+	int i;
+	u64 l;
+	int again = 1;
+
+	while (again) {
+		again = 0;
+		for (i = 0; i < num_stripes - 1; i++) {
+			if (parity_smaller(bbio->raid_map[i],
+					   bbio->raid_map[i+1])) {
+				s = bbio->stripes[i];
+				l = bbio->raid_map[i];
+				bbio->stripes[i] = bbio->stripes[i+1];
+				bbio->raid_map[i] = bbio->raid_map[i+1];
+				bbio->stripes[i+1] = s;
+				bbio->raid_map[i+1] = l;
+
+				again = 1;
+			}
+		}
+	}
+}
+
+static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
+{
+	struct btrfs_bio *bbio = kzalloc(
+		 /* the size of the btrfs_bio */
+		sizeof(struct btrfs_bio) +
+		/* plus the variable array for the stripes */
+		sizeof(struct btrfs_bio_stripe) * (total_stripes) +
+		/* plus the variable array for the tgt dev */
+		sizeof(int) * (real_stripes) +
+		/*
+		 * plus the raid_map, which includes both the tgt dev
+		 * and the stripes
+		 */
+		sizeof(u64) * (total_stripes),
+		GFP_NOFS|__GFP_NOFAIL);
+
+	atomic_set(&bbio->error, 0);
+	refcount_set(&bbio->refs, 1);
+
+	return bbio;
+}
+
+void btrfs_get_bbio(struct btrfs_bio *bbio)
+{
+	WARN_ON(!refcount_read(&bbio->refs));
+	refcount_inc(&bbio->refs);
+}
+
+void btrfs_put_bbio(struct btrfs_bio *bbio)
+{
+	if (!bbio)
+		return;
+	if (refcount_dec_and_test(&bbio->refs))
+		kfree(bbio);
+}
+
+/* can REQ_OP_DISCARD be sent with other REQ like REQ_OP_WRITE? */
+/*
+ * Please note that, discard won't be sent to target device of device
+ * replace.
+ */
+static int __btrfs_map_block_for_discard(struct btrfs_fs_info *fs_info,
+					 u64 logical, u64 length,
+					 struct btrfs_bio **bbio_ret)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct btrfs_bio *bbio;
+	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 = 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->len - offset, 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 |
+				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;
+}
+
+/*
+ * In dev-replace case, for repair case (that's the only case where the mirror
+ * is selected explicitly when calling btrfs_map_block), blocks left of the
+ * left cursor can also be read from the target drive.
+ *
+ * For REQ_GET_READ_MIRRORS, the target drive is added as the last one to the
+ * array of stripes.
+ * For READ, it also needs to be supported using the same mirror number.
+ *
+ * If the requested block is not left of the left cursor, EIO is returned. This
+ * can happen because btrfs_num_copies() returns one more in the dev-replace
+ * case.
+ */
+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 handle_ops_on_dev_replace(enum btrfs_map_op op,
+				      struct btrfs_bio **bbio_ret,
+				      struct btrfs_dev_replace *dev_replace,
+				      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;
+
+		/*
+		 * 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 bool need_full_stripe(enum btrfs_map_op op)
+{
+	return (op == BTRFS_MAP_WRITE || op == BTRFS_MAP_GET_READ_MIRRORS);
+}
+
+static int __btrfs_map_block(struct btrfs_fs_info *fs_info,
+			     enum btrfs_map_op op,
+			     u64 logical, u64 *length,
+			     struct btrfs_bio **bbio_ret,
+			     int mirror_num, int need_raid_map)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	u64 offset;
+	u64 stripe_offset;
+	u64 stripe_nr;
+	u64 stripe_len;
+	u32 stripe_index;
+	int i;
+	int ret = 0;
+	int num_stripes;
+	int max_errors = 0;
+	int tgtdev_indexes = 0;
+	struct btrfs_bio *bbio = NULL;
+	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
+	int dev_replace_is_ongoing = 0;
+	int num_alloc_stripes;
+	int patch_the_first_stripe_for_dev_replace = 0;
+	u64 physical_to_patch_in_first_stripe = 0;
+	u64 raid56_full_stripe_start = (u64)-1;
+
+	if (op == BTRFS_MAP_DISCARD)
+		return __btrfs_map_block_for_discard(fs_info, logical,
+						     *length, bbio_ret);
+
+	em = get_chunk_map(fs_info, logical, *length);
+	if (IS_ERR(em))
+		return PTR_ERR(em);
+
+	map = em->map_lookup;
+	offset = logical - em->start;
+
+	stripe_len = map->stripe_len;
+	stripe_nr = offset;
+	/*
+	 * stripe_nr counts the total number of stripes we have to stride
+	 * to get to this block
+	 */
+	stripe_nr = div64_u64(stripe_nr, stripe_len);
+
+	stripe_offset = stripe_nr * stripe_len;
+	if (offset < stripe_offset) {
+		btrfs_crit(fs_info,
+			   "stripe math has gone wrong, stripe_offset=%llu, offset=%llu, start=%llu, logical=%llu, stripe_len=%llu",
+			   stripe_offset, offset, em->start, logical,
+			   stripe_len);
+		free_extent_map(em);
+		return -EINVAL;
+	}
+
+	/* stripe_offset is the offset of this block in its stripe*/
+	stripe_offset = offset - stripe_offset;
+
+	/* if we're here for raid56, we need to know the stripe aligned start */
+	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		unsigned long full_stripe_len = stripe_len * nr_data_stripes(map);
+		raid56_full_stripe_start = offset;
+
+		/* allow a write of a full stripe, but make sure we don't
+		 * allow straddling of stripes
+		 */
+		raid56_full_stripe_start = div64_u64(raid56_full_stripe_start,
+				full_stripe_len);
+		raid56_full_stripe_start *= full_stripe_len;
+	}
+
+	if (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
+		u64 max_len;
+		/* For writes to RAID[56], allow a full stripeset across all disks.
+		   For other RAID types and for RAID[56] reads, just allow a single
+		   stripe (on a single disk). */
+		if ((map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) &&
+		    (op == BTRFS_MAP_WRITE)) {
+			max_len = stripe_len * nr_data_stripes(map) -
+				(offset - raid56_full_stripe_start);
+		} else {
+			/* we limit the length of each bio to what fits in a stripe */
+			max_len = stripe_len - stripe_offset;
+		}
+		*length = min_t(u64, em->len - offset, max_len);
+	} else {
+		*length = em->len - offset;
+	}
+
+	/* This is for when we're called from btrfs_merge_bio_hook() and all
+	   it cares about is the length */
+	if (!bbio_ret)
+		goto out;
+
+	btrfs_dev_replace_read_lock(dev_replace);
+	dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace);
+	if (!dev_replace_is_ongoing)
+		btrfs_dev_replace_read_unlock(dev_replace);
+	else
+		btrfs_dev_replace_set_lock_blocking(dev_replace);
+
+	if (dev_replace_is_ongoing && mirror_num == map->num_stripes + 1 &&
+	    !need_full_stripe(op) && dev_replace->tgtdev != NULL) {
+		ret = get_extra_mirror_from_replace(fs_info, logical, *length,
+						    dev_replace->srcdev->devid,
+						    &mirror_num,
+					    &physical_to_patch_in_first_stripe);
+		if (ret)
+			goto out;
+		else
+			patch_the_first_stripe_for_dev_replace = 1;
+	} else if (mirror_num > map->num_stripes) {
+		mirror_num = 0;
+	}
+
+	num_stripes = 1;
+	stripe_index = 0;
+	if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
+		stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
+				&stripe_index);
+		if (!need_full_stripe(op))
+			mirror_num = 1;
+	} else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
+		if (need_full_stripe(op))
+			num_stripes = map->num_stripes;
+		else if (mirror_num)
+			stripe_index = mirror_num - 1;
+		else {
+			stripe_index = find_live_mirror(fs_info, map, 0,
+					    dev_replace_is_ongoing);
+			mirror_num = stripe_index + 1;
+		}
+
+	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
+		if (need_full_stripe(op)) {
+			num_stripes = map->num_stripes;
+		} else if (mirror_num) {
+			stripe_index = mirror_num - 1;
+		} else {
+			mirror_num = 1;
+		}
+
+	} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
+		u32 factor = map->num_stripes / map->sub_stripes;
+
+		stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
+		stripe_index *= map->sub_stripes;
+
+		if (need_full_stripe(op))
+			num_stripes = map->sub_stripes;
+		else if (mirror_num)
+			stripe_index += mirror_num - 1;
+		else {
+			int old_stripe_index = stripe_index;
+			stripe_index = find_live_mirror(fs_info, map,
+					      stripe_index,
+					      dev_replace_is_ongoing);
+			mirror_num = stripe_index - old_stripe_index + 1;
+		}
+
+	} else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		if (need_raid_map && (need_full_stripe(op) || mirror_num > 1)) {
+			/* push stripe_nr back to the start of the full stripe */
+			stripe_nr = div64_u64(raid56_full_stripe_start,
+					stripe_len * nr_data_stripes(map));
+
+			/* RAID[56] write or recovery. Return all stripes */
+			num_stripes = map->num_stripes;
+			max_errors = nr_parity_stripes(map);
+
+			*length = map->stripe_len;
+			stripe_index = 0;
+			stripe_offset = 0;
+		} else {
+			/*
+			 * Mirror #0 or #1 means the original data block.
+			 * Mirror #2 is RAID5 parity block.
+			 * Mirror #3 is RAID6 Q block.
+			 */
+			stripe_nr = div_u64_rem(stripe_nr,
+					nr_data_stripes(map), &stripe_index);
+			if (mirror_num > 1)
+				stripe_index = nr_data_stripes(map) +
+						mirror_num - 2;
+
+			/* We distribute the parity blocks across stripes */
+			div_u64_rem(stripe_nr + stripe_index, map->num_stripes,
+					&stripe_index);
+			if (!need_full_stripe(op) && mirror_num <= 1)
+				mirror_num = 1;
+		}
+	} else {
+		/*
+		 * 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
+		 */
+		stripe_nr = div_u64_rem(stripe_nr, map->num_stripes,
+				&stripe_index);
+		mirror_num = stripe_index + 1;
+	}
+	if (stripe_index >= map->num_stripes) {
+		btrfs_crit(fs_info,
+			   "stripe index math went horribly wrong, got stripe_index=%u, num_stripes=%u",
+			   stripe_index, map->num_stripes);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	num_alloc_stripes = num_stripes;
+	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL) {
+		if (op == BTRFS_MAP_WRITE)
+			num_alloc_stripes <<= 1;
+		if (op == BTRFS_MAP_GET_READ_MIRRORS)
+			num_alloc_stripes++;
+		tgtdev_indexes = num_stripes;
+	}
+
+	bbio = alloc_btrfs_bio(num_alloc_stripes, tgtdev_indexes);
+	if (!bbio) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL)
+		bbio->tgtdev_map = (int *)(bbio->stripes + num_alloc_stripes);
+
+	/* build raid_map */
+	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map &&
+	    (need_full_stripe(op) || mirror_num > 1)) {
+		u64 tmp;
+		unsigned rot;
+
+		bbio->raid_map = (u64 *)((void *)bbio->stripes +
+				 sizeof(struct btrfs_bio_stripe) *
+				 num_alloc_stripes +
+				 sizeof(int) * tgtdev_indexes);
+
+		/* Work out the disk rotation on this stripe-set */
+		div_u64_rem(stripe_nr, num_stripes, &rot);
+
+		/* Fill in the logical address of each stripe */
+		tmp = stripe_nr * nr_data_stripes(map);
+		for (i = 0; i < nr_data_stripes(map); i++)
+			bbio->raid_map[(i+rot) % num_stripes] =
+				em->start + (tmp + i) * map->stripe_len;
+
+		bbio->raid_map[(i+rot) % map->num_stripes] = RAID5_P_STRIPE;
+		if (map->type & BTRFS_BLOCK_GROUP_RAID6)
+			bbio->raid_map[(i+rot+1) % num_stripes] =
+				RAID6_Q_STRIPE;
+	}
+
+
+	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;
+		stripe_index++;
+	}
+
+	if (need_full_stripe(op))
+		max_errors = btrfs_chunk_max_errors(map);
+
+	if (bbio->raid_map)
+		sort_parity_stripes(bbio, num_stripes);
+
+	if (dev_replace_is_ongoing && dev_replace->tgtdev != NULL &&
+	    need_full_stripe(op)) {
+		handle_ops_on_dev_replace(op, &bbio, dev_replace, &num_stripes,
+					  &max_errors);
+	}
+
+	*bbio_ret = bbio;
+	bbio->map_type = map->type;
+	bbio->num_stripes = num_stripes;
+	bbio->max_errors = max_errors;
+	bbio->mirror_num = mirror_num;
+
+	/*
+	 * this is the case that REQ_READ && dev_replace_is_ongoing &&
+	 * mirror_num == num_stripes + 1 && dev_replace target drive is
+	 * available as a mirror
+	 */
+	if (patch_the_first_stripe_for_dev_replace && num_stripes > 0) {
+		WARN_ON(num_stripes > 1);
+		bbio->stripes[0].dev = dev_replace->tgtdev;
+		bbio->stripes[0].physical = physical_to_patch_in_first_stripe;
+		bbio->mirror_num = map->num_stripes + 1;
+	}
+out:
+	if (dev_replace_is_ongoing) {
+		btrfs_dev_replace_clear_lock_blocking(dev_replace);
+		btrfs_dev_replace_read_unlock(dev_replace);
+	}
+	free_extent_map(em);
+	return ret;
+}
+
+int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
+		      u64 logical, u64 *length,
+		      struct btrfs_bio **bbio_ret, int mirror_num)
+{
+	return __btrfs_map_block(fs_info, op, logical, length, bbio_ret,
+				 mirror_num, 0);
+}
+
+/* For Scrub/replace */
+int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
+		     u64 logical, u64 *length,
+		     struct btrfs_bio **bbio_ret)
+{
+	return __btrfs_map_block(fs_info, op, logical, length, bbio_ret, 0, 1);
+}
+
+int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
+		     u64 physical, u64 **logical, int *naddrs, int *stripe_len)
+{
+	struct extent_map *em;
+	struct map_lookup *map;
+	u64 *buf;
+	u64 bytenr;
+	u64 length;
+	u64 stripe_nr;
+	u64 rmap_len;
+	int i, j, nr = 0;
+
+	em = get_chunk_map(fs_info, chunk_start, 1);
+	if (IS_ERR(em))
+		return -EIO;
+
+	map = em->map_lookup;
+	length = em->len;
+	rmap_len = map->stripe_len;
+
+	if (map->type & BTRFS_BLOCK_GROUP_RAID10)
+		length = div_u64(length, map->num_stripes / map->sub_stripes);
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID0)
+		length = div_u64(length, map->num_stripes);
+	else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		length = div_u64(length, nr_data_stripes(map));
+		rmap_len = map->stripe_len * nr_data_stripes(map);
+	}
+
+	buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
+	BUG_ON(!buf); /* -ENOMEM */
+
+	for (i = 0; i < map->num_stripes; i++) {
+		if (map->stripes[i].physical > physical ||
+		    map->stripes[i].physical + length <= physical)
+			continue;
+
+		stripe_nr = physical - map->stripes[i].physical;
+		stripe_nr = div64_u64(stripe_nr, map->stripe_len);
+
+		if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
+			stripe_nr = stripe_nr * map->num_stripes + i;
+			stripe_nr = div_u64(stripe_nr, map->sub_stripes);
+		} else if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
+			stripe_nr = stripe_nr * map->num_stripes + i;
+		} /* else if RAID[56], multiply by nr_data_stripes().
+		   * Alternatively, just use rmap_len below instead of
+		   * map->stripe_len */
+
+		bytenr = chunk_start + stripe_nr * rmap_len;
+		WARN_ON(nr >= map->num_stripes);
+		for (j = 0; j < nr; j++) {
+			if (buf[j] == bytenr)
+				break;
+		}
+		if (j == nr) {
+			WARN_ON(nr >= map->num_stripes);
+			buf[nr++] = bytenr;
+		}
+	}
+
+	*logical = buf;
+	*naddrs = nr;
+	*stripe_len = rmap_len;
+
+	free_extent_map(em);
+	return 0;
+}
+
+static inline void btrfs_end_bbio(struct btrfs_bio *bbio, struct bio *bio)
+{
+	bio->bi_private = bbio->private;
+	bio->bi_end_io = bbio->end_io;
+	bio_endio(bio);
+
+	btrfs_put_bbio(bbio);
+}
+
+static void btrfs_end_bio(struct bio *bio)
+{
+	struct btrfs_bio *bbio = bio->bi_private;
+	int is_orig_bio = 0;
+
+	if (bio->bi_status) {
+		atomic_inc(&bbio->error);
+		if (bio->bi_status == BLK_STS_IOERR ||
+		    bio->bi_status == BLK_STS_TARGET) {
+			unsigned int stripe_index =
+				btrfs_io_bio(bio)->stripe_index;
+			struct btrfs_device *dev;
+
+			BUG_ON(stripe_index >= bbio->num_stripes);
+			dev = bbio->stripes[stripe_index].dev;
+			if (dev->bdev) {
+				if (bio_op(bio) == REQ_OP_WRITE)
+					btrfs_dev_stat_inc_and_print(dev,
+						BTRFS_DEV_STAT_WRITE_ERRS);
+				else if (!(bio->bi_opf & REQ_RAHEAD))
+					btrfs_dev_stat_inc_and_print(dev,
+						BTRFS_DEV_STAT_READ_ERRS);
+				if (bio->bi_opf & REQ_PREFLUSH)
+					btrfs_dev_stat_inc_and_print(dev,
+						BTRFS_DEV_STAT_FLUSH_ERRS);
+			}
+		}
+	}
+
+	if (bio == bbio->orig_bio)
+		is_orig_bio = 1;
+
+	btrfs_bio_counter_dec(bbio->fs_info);
+
+	if (atomic_dec_and_test(&bbio->stripes_pending)) {
+		if (!is_orig_bio) {
+			bio_put(bio);
+			bio = bbio->orig_bio;
+		}
+
+		btrfs_io_bio(bio)->mirror_num = bbio->mirror_num;
+		/* only send an error to the higher layers if it is
+		 * beyond the tolerance of the btrfs bio
+		 */
+		if (atomic_read(&bbio->error) > bbio->max_errors) {
+			bio->bi_status = BLK_STS_IOERR;
+		} else {
+			/*
+			 * this bio is actually up to date, we didn't
+			 * go over the max number of errors
+			 */
+			bio->bi_status = BLK_STS_OK;
+		}
+
+		btrfs_end_bbio(bbio, bio);
+	} else if (!is_orig_bio) {
+		bio_put(bio);
+	}
+}
+
+/*
+ * see run_scheduled_bios for a description of why bios are collected for
+ * async submit.
+ *
+ * This will add one bio to the pending list for a device and make sure
+ * the work struct is scheduled.
+ */
+static noinline void btrfs_schedule_bio(struct btrfs_device *device,
+					struct bio *bio)
+{
+	struct btrfs_fs_info *fs_info = device->fs_info;
+	int should_queue = 1;
+	struct btrfs_pending_bios *pending_bios;
+
+	/* don't bother with additional async steps for reads, right now */
+	if (bio_op(bio) == REQ_OP_READ) {
+		btrfsic_submit_bio(bio);
+		return;
+	}
+
+	WARN_ON(bio->bi_next);
+	bio->bi_next = NULL;
+
+	spin_lock(&device->io_lock);
+	if (op_is_sync(bio->bi_opf))
+		pending_bios = &device->pending_sync_bios;
+	else
+		pending_bios = &device->pending_bios;
+
+	if (pending_bios->tail)
+		pending_bios->tail->bi_next = bio;
+
+	pending_bios->tail = bio;
+	if (!pending_bios->head)
+		pending_bios->head = bio;
+	if (device->running_pending)
+		should_queue = 0;
+
+	spin_unlock(&device->io_lock);
+
+	if (should_queue)
+		btrfs_queue_work(fs_info->submit_workers, &device->work);
+}
+
+static void submit_stripe_bio(struct btrfs_bio *bbio, struct bio *bio,
+			      u64 physical, int dev_nr, int async)
+{
+	struct btrfs_device *dev = bbio->stripes[dev_nr].dev;
+	struct btrfs_fs_info *fs_info = bbio->fs_info;
+
+	bio->bi_private = bbio;
+	btrfs_io_bio(bio)->stripe_index = dev_nr;
+	bio->bi_end_io = btrfs_end_bio;
+	bio->bi_iter.bi_sector = physical >> 9;
+	btrfs_debug_in_rcu(fs_info,
+	"btrfs_map_bio: rw %d 0x%x, sector=%llu, dev=%lu (%s id %llu), size=%u",
+		bio_op(bio), bio->bi_opf, (u64)bio->bi_iter.bi_sector,
+		(u_long)dev->bdev->bd_dev, rcu_str_deref(dev->name), dev->devid,
+		bio->bi_iter.bi_size);
+	bio_set_dev(bio, dev->bdev);
+
+	btrfs_bio_counter_inc_noblocked(fs_info);
+
+	if (async)
+		btrfs_schedule_bio(dev, bio);
+	else
+		btrfsic_submit_bio(bio);
+}
+
+static void bbio_error(struct btrfs_bio *bbio, struct bio *bio, u64 logical)
+{
+	atomic_inc(&bbio->error);
+	if (atomic_dec_and_test(&bbio->stripes_pending)) {
+		/* Should be the original bio. */
+		WARN_ON(bio != bbio->orig_bio);
+
+		btrfs_io_bio(bio)->mirror_num = bbio->mirror_num;
+		bio->bi_iter.bi_sector = logical >> 9;
+		if (atomic_read(&bbio->error) > bbio->max_errors)
+			bio->bi_status = BLK_STS_IOERR;
+		else
+			bio->bi_status = BLK_STS_OK;
+		btrfs_end_bbio(bbio, bio);
+	}
+}
+
+blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
+			   int mirror_num, int async_submit)
+{
+	struct btrfs_device *dev;
+	struct bio *first_bio = bio;
+	u64 logical = (u64)bio->bi_iter.bi_sector << 9;
+	u64 length = 0;
+	u64 map_length;
+	int ret;
+	int dev_nr;
+	int total_devs;
+	struct btrfs_bio *bbio = NULL;
+
+	length = bio->bi_iter.bi_size;
+	map_length = length;
+
+	btrfs_bio_counter_inc_blocked(fs_info);
+	ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical,
+				&map_length, &bbio, mirror_num, 1);
+	if (ret) {
+		btrfs_bio_counter_dec(fs_info);
+		return errno_to_blk_status(ret);
+	}
+
+	total_devs = bbio->num_stripes;
+	bbio->orig_bio = first_bio;
+	bbio->private = first_bio->bi_private;
+	bbio->end_io = first_bio->bi_end_io;
+	bbio->fs_info = fs_info;
+	atomic_set(&bbio->stripes_pending, bbio->num_stripes);
+
+	if ((bbio->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK) &&
+	    ((bio_op(bio) == REQ_OP_WRITE) || (mirror_num > 1))) {
+		/* In this case, map_length has been set to the length of
+		   a single stripe; not the whole write */
+		if (bio_op(bio) == REQ_OP_WRITE) {
+			ret = raid56_parity_write(fs_info, bio, bbio,
+						  map_length);
+		} else {
+			ret = raid56_parity_recover(fs_info, bio, bbio,
+						    map_length, mirror_num, 1);
+		}
+
+		btrfs_bio_counter_dec(fs_info);
+		return errno_to_blk_status(ret);
+	}
+
+	if (map_length < length) {
+		btrfs_crit(fs_info,
+			   "mapping failed logical %llu bio len %llu len %llu",
+			   logical, length, map_length);
+		BUG();
+	}
+
+	for (dev_nr = 0; dev_nr < total_devs; dev_nr++) {
+		dev = bbio->stripes[dev_nr].dev;
+		if (!dev || !dev->bdev || test_bit(BTRFS_DEV_STATE_MISSING,
+						   &dev->dev_state) ||
+		    (bio_op(first_bio) == REQ_OP_WRITE &&
+		    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))) {
+			bbio_error(bbio, first_bio, logical);
+			continue;
+		}
+
+		if (dev_nr < total_devs - 1)
+			bio = btrfs_bio_clone(first_bio);
+		else
+			bio = first_bio;
+
+		submit_stripe_bio(bbio, bio, bbio->stripes[dev_nr].physical,
+				  dev_nr, async_submit);
+	}
+	btrfs_bio_counter_dec(fs_info);
+	return BLK_STS_OK;
+}
+
+/*
+ * Find a device specified by @devid or @uuid in the list of @fs_devices, or
+ * return NULL.
+ *
+ * If devid and uuid are both specified, the match must be exact, otherwise
+ * only devid is used.
+ *
+ * If @seed is true, traverse through the seed devices.
+ */
+struct btrfs_device *btrfs_find_device(struct btrfs_fs_devices *fs_devices,
+					u64 devid, u8 *uuid, u8 *fsid,
+					bool seed)
+{
+	struct btrfs_device *device;
+
+	while (fs_devices) {
+		if (!fsid ||
+		    !memcmp(fs_devices->fsid, 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;
+			}
+		}
+		if (seed)
+			fs_devices = fs_devices->seed;
+		else
+			return NULL;
+	}
+	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;
+}
+
+/**
+ * btrfs_alloc_device - allocate struct btrfs_device
+ * @fs_info:	used only for generating a new devid, can be NULL if
+ *		devid is provided (i.e. @devid != NULL).
+ * @devid:	a pointer to devid for this device.  If NULL a new devid
+ *		is generated.
+ * @uuid:	a pointer to UUID for this device.  If NULL a new UUID
+ *		is generated.
+ *
+ * Return: a pointer to a new &struct btrfs_device on success; ERR_PTR()
+ * on error.  Returned struct is not linked onto any lists and must be
+ * destroyed with btrfs_free_device.
+ */
+struct btrfs_device *btrfs_alloc_device(struct btrfs_fs_info *fs_info,
+					const u64 *devid,
+					const u8 *uuid)
+{
+	struct btrfs_device *dev;
+	u64 tmp;
+
+	if (WARN_ON(!devid && !fs_info))
+		return ERR_PTR(-EINVAL);
+
+	dev = __alloc_device();
+	if (IS_ERR(dev))
+		return dev;
+
+	if (devid)
+		tmp = *devid;
+	else {
+		int ret;
+
+		ret = find_next_devid(fs_info, &tmp);
+		if (ret) {
+			btrfs_free_device(dev);
+			return ERR_PTR(ret);
+		}
+	}
+	dev->devid = tmp;
+
+	if (uuid)
+		memcpy(dev->uuid, uuid, BTRFS_UUID_SIZE);
+	else
+		generate_random_uuid(dev->uuid);
+
+	btrfs_init_work(&dev->work, btrfs_submit_helper,
+			pending_bios_fn, NULL, NULL);
+
+	return dev;
+}
+
+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 int read_one_chunk(struct btrfs_fs_info *fs_info, struct btrfs_key *key,
+			  struct extent_buffer *leaf,
+			  struct btrfs_chunk *chunk)
+{
+	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
+	struct map_lookup *map;
+	struct extent_map *em;
+	u64 logical;
+	u64 length;
+	u64 devid;
+	u8 uuid[BTRFS_UUID_SIZE];
+	int num_stripes;
+	int ret;
+	int i;
+
+	logical = key->offset;
+	length = btrfs_chunk_length(leaf, chunk);
+	num_stripes = btrfs_chunk_num_stripes(leaf, chunk);
+
+	/*
+	 * Only need to verify chunk item if we're reading from sys chunk array,
+	 * as chunk item in tree block is already verified by tree-checker.
+	 */
+	if (leaf->start == BTRFS_SUPER_INFO_OFFSET) {
+		ret = btrfs_check_chunk_valid(fs_info, leaf, chunk, logical);
+		if (ret)
+			return ret;
+	}
+
+	read_lock(&map_tree->map_tree.lock);
+	em = lookup_extent_mapping(&map_tree->map_tree, logical, 1);
+	read_unlock(&map_tree->map_tree.lock);
+
+	/* already mapped? */
+	if (em && em->start <= logical && em->start + em->len > logical) {
+		free_extent_map(em);
+		return 0;
+	} else if (em) {
+		free_extent_map(em);
+	}
+
+	em = alloc_extent_map();
+	if (!em)
+		return -ENOMEM;
+	map = kmalloc(map_lookup_size(num_stripes), GFP_NOFS);
+	if (!map) {
+		free_extent_map(em);
+		return -ENOMEM;
+	}
+
+	set_bit(EXTENT_FLAG_FS_MAPPING, &em->flags);
+	em->map_lookup = map;
+	em->start = logical;
+	em->len = length;
+	em->orig_start = 0;
+	em->block_start = 0;
+	em->block_len = em->len;
+
+	map->num_stripes = num_stripes;
+	map->io_width = btrfs_chunk_io_width(leaf, chunk);
+	map->io_align = btrfs_chunk_io_align(leaf, chunk);
+	map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
+	map->type = btrfs_chunk_type(leaf, chunk);
+	map->sub_stripes = btrfs_chunk_sub_stripes(leaf, chunk);
+	map->verified_stripes = 0;
+	for (i = 0; i < num_stripes; i++) {
+		map->stripes[i].physical =
+			btrfs_stripe_offset_nr(leaf, chunk, i);
+		devid = btrfs_stripe_devid_nr(leaf, chunk, i);
+		read_extent_buffer(leaf, uuid, (unsigned long)
+				   btrfs_stripe_dev_uuid_nr(chunk, i),
+				   BTRFS_UUID_SIZE);
+		map->stripes[i].dev = btrfs_find_device(fs_info->fs_devices,
+						devid, uuid, NULL, true);
+		if (!map->stripes[i].dev &&
+		    !btrfs_test_opt(fs_info, DEGRADED)) {
+			free_extent_map(em);
+			btrfs_report_missing_device(fs_info, devid, uuid, true);
+			return -ENOENT;
+		}
+		if (!map->stripes[i].dev) {
+			map->stripes[i].dev =
+				add_missing_dev(fs_info->fs_devices, devid,
+						uuid);
+			if (IS_ERR(map->stripes[i].dev)) {
+				free_extent_map(em);
+				btrfs_err(fs_info,
+					"failed to init missing dev %llu: %ld",
+					devid, PTR_ERR(map->stripes[i].dev));
+				return PTR_ERR(map->stripes[i].dev);
+			}
+			btrfs_report_missing_device(fs_info, devid, uuid, false);
+		}
+		set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
+				&(map->stripes[i].dev->dev_state));
+
+	}
+
+	write_lock(&map_tree->map_tree.lock);
+	ret = add_extent_mapping(&map_tree->map_tree, em, 0);
+	write_unlock(&map_tree->map_tree.lock);
+	if (ret < 0) {
+		btrfs_err(fs_info,
+			  "failed to add chunk map, start=%llu len=%llu: %d",
+			  em->start, em->len, ret);
+	}
+	free_extent_map(em);
+
+	return ret;
+}
+
+static void fill_device_from_item(struct extent_buffer *leaf,
+				 struct btrfs_dev_item *dev_item,
+				 struct btrfs_device *device)
+{
+	unsigned long ptr;
+
+	device->devid = btrfs_device_id(leaf, dev_item);
+	device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item);
+	device->total_bytes = device->disk_total_bytes;
+	device->commit_total_bytes = device->disk_total_bytes;
+	device->bytes_used = btrfs_device_bytes_used(leaf, dev_item);
+	device->commit_bytes_used = device->bytes_used;
+	device->type = btrfs_device_type(leaf, dev_item);
+	device->io_align = btrfs_device_io_align(leaf, dev_item);
+	device->io_width = btrfs_device_io_width(leaf, dev_item);
+	device->sector_size = btrfs_device_sector_size(leaf, dev_item);
+	WARN_ON(device->devid == BTRFS_DEV_REPLACE_DEVID);
+	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
+
+	ptr = btrfs_device_uuid(dev_item);
+	read_extent_buffer(leaf, device->uuid, ptr, BTRFS_UUID_SIZE);
+}
+
+static struct btrfs_fs_devices *open_seed_devices(struct btrfs_fs_info *fs_info,
+						  u8 *fsid)
+{
+	struct btrfs_fs_devices *fs_devices;
+	int ret;
+
+	lockdep_assert_held(&uuid_mutex);
+	ASSERT(fsid);
+
+	fs_devices = fs_info->fs_devices->seed;
+	while (fs_devices) {
+		if (!memcmp(fs_devices->fsid, fsid, BTRFS_FSID_SIZE))
+			return fs_devices;
+
+		fs_devices = fs_devices->seed;
+	}
+
+	fs_devices = find_fsid(fsid);
+	if (!fs_devices) {
+		if (!btrfs_test_opt(fs_info, DEGRADED))
+			return ERR_PTR(-ENOENT);
+
+		fs_devices = alloc_fs_devices(fsid);
+		if (IS_ERR(fs_devices))
+			return fs_devices;
+
+		fs_devices->seeding = 1;
+		fs_devices->opened = 1;
+		return fs_devices;
+	}
+
+	fs_devices = clone_fs_devices(fs_devices);
+	if (IS_ERR(fs_devices))
+		return fs_devices;
+
+	ret = open_fs_devices(fs_devices, FMODE_READ, fs_info->bdev_holder);
+	if (ret) {
+		free_fs_devices(fs_devices);
+		fs_devices = ERR_PTR(ret);
+		goto out;
+	}
+
+	if (!fs_devices->seeding) {
+		close_fs_devices(fs_devices);
+		free_fs_devices(fs_devices);
+		fs_devices = ERR_PTR(-EINVAL);
+		goto out;
+	}
+
+	fs_devices->seed = fs_info->fs_devices->seed;
+	fs_info->fs_devices->seed = fs_devices;
+out:
+	return fs_devices;
+}
+
+static int read_one_dev(struct btrfs_fs_info *fs_info,
+			struct extent_buffer *leaf,
+			struct btrfs_dev_item *dev_item)
+{
+	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_info->fsid, 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, true);
+	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);
+	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_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);
+	if (IS_ERR(sb))
+		return PTR_ERR(sb);
+	set_extent_buffer_uptodate(sb);
+	btrfs_set_buffer_lockdep_class(root->root_key.objectid, sb, 0);
+	/*
+	 * 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) {
+			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(fs_info, &key, sb, chunk);
+			if (ret)
+				break;
+		} else {
+			btrfs_err(fs_info,
+			    "unexpected item type %u in sys_array at offset %u",
+				  (u32)key.type, cur_offset);
+			ret = -EIO;
+			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;
+}
+
+/*
+ * Check if all chunks in the fs are OK for read-write degraded mount
+ *
+ * If the @failing_dev is specified, it's accounted as missing.
+ *
+ * Return true if all chunks meet the minimal RW mount requirements.
+ * Return false if any chunk doesn't meet the minimal RW mount requirements.
+ */
+bool btrfs_check_rw_degradable(struct btrfs_fs_info *fs_info,
+					struct btrfs_device *failing_dev)
+{
+	struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
+	struct extent_map *em;
+	u64 next_start = 0;
+	bool ret = true;
+
+	read_lock(&map_tree->map_tree.lock);
+	em = lookup_extent_mapping(&map_tree->map_tree, 0, (u64)-1);
+	read_unlock(&map_tree->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 writeable 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->map_tree.lock);
+		em = lookup_extent_mapping(&map_tree->map_tree, next_start,
+					   (u64)(-1) - next_start);
+		read_unlock(&map_tree->map_tree.lock);
+	}
+out:
+	return ret;
+}
+
+int btrfs_read_chunk_tree(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root = fs_info->chunk_root;
+	struct btrfs_path *path;
+	struct extent_buffer *leaf;
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	int ret;
+	int slot;
+	u64 total_dev = 0;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	/*
+	 * uuid_mutex is needed only if we are mounting a sprout FS
+	 * otherwise we don't need it.
+	 */
+	mutex_lock(&uuid_mutex);
+	mutex_lock(&fs_info->chunk_mutex);
+
+	/*
+	 * It is possible for mount and umount to race in such a way that
+	 * we execute this code path, but open_fs_devices failed to clear
+	 * total_rw_bytes. We certainly want it cleared before reading the
+	 * device items, so clear it here.
+	 */
+	fs_info->fs_devices->total_rw_bytes = 0;
+
+	/*
+	 * Read all device items, and then all the chunk items. All
+	 * device items are found before any chunk item (their object id
+	 * is smaller than the lowest possible object id for a chunk
+	 * item - BTRFS_FIRST_CHUNK_TREE_OBJECTID).
+	 */
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.offset = 0;
+	key.type = 0;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto error;
+	while (1) {
+		leaf = path->nodes[0];
+		slot = path->slots[0];
+		if (slot >= btrfs_header_nritems(leaf)) {
+			ret = btrfs_next_leaf(root, path);
+			if (ret == 0)
+				continue;
+			if (ret < 0)
+				goto error;
+			break;
+		}
+		btrfs_item_key_to_cpu(leaf, &found_key, slot);
+		if (found_key.type == BTRFS_DEV_ITEM_KEY) {
+			struct btrfs_dev_item *dev_item;
+			dev_item = btrfs_item_ptr(leaf, slot,
+						  struct btrfs_dev_item);
+			ret = read_one_dev(fs_info, leaf, dev_item);
+			if (ret)
+				goto error;
+			total_dev++;
+		} else if (found_key.type == BTRFS_CHUNK_ITEM_KEY) {
+			struct btrfs_chunk *chunk;
+			chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk);
+			ret = read_one_chunk(fs_info, &found_key, leaf, chunk);
+			if (ret)
+				goto error;
+		}
+		path->slots[0]++;
+	}
+
+	/*
+	 * After loading chunk tree, we've got all device information,
+	 * do another round of validation checks.
+	 */
+	if (total_dev != fs_info->fs_devices->total_devices) {
+		btrfs_warn(fs_info,
+"super block num_devices %llu mismatch with DEV_ITEM count %llu, will be repaired on next transaction commit",
+			  btrfs_super_num_devices(fs_info->super_copy),
+			  total_dev);
+		fs_info->fs_devices->total_devices = total_dev;
+		btrfs_set_super_num_devices(fs_info->super_copy, total_dev);
+	}
+	if (btrfs_super_total_bytes(fs_info->super_copy) <
+	    fs_info->fs_devices->total_rw_bytes) {
+		btrfs_err(fs_info,
+	"super_total_bytes %llu mismatch with fs_devices total_rw_bytes %llu",
+			  btrfs_super_total_bytes(fs_info->super_copy),
+			  fs_info->fs_devices->total_rw_bytes);
+		ret = -EINVAL;
+		goto error;
+	}
+	ret = 0;
+error:
+	mutex_unlock(&fs_info->chunk_mutex);
+	mutex_unlock(&uuid_mutex);
+
+	btrfs_free_path(path);
+	return ret;
+}
+
+void btrfs_init_devices_late(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_device *device;
+
+	while (fs_devices) {
+		mutex_lock(&fs_devices->device_list_mutex);
+		list_for_each_entry(device, &fs_devices->devices, dev_list)
+			device->fs_info = fs_info;
+		mutex_unlock(&fs_devices->device_list_mutex);
+
+		fs_devices = fs_devices->seed;
+	}
+}
+
+static void __btrfs_reset_dev_stats(struct btrfs_device *dev)
+{
+	int i;
+
+	for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+		btrfs_dev_stat_reset(dev, i);
+}
+
+int btrfs_init_dev_stats(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_key key;
+	struct btrfs_key found_key;
+	struct btrfs_root *dev_root = fs_info->dev_root;
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct extent_buffer *eb;
+	int slot;
+	int ret = 0;
+	struct btrfs_device *device;
+	struct btrfs_path *path = NULL;
+	int i;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		int item_size;
+		struct btrfs_dev_stats_item *ptr;
+
+		key.objectid = BTRFS_DEV_STATS_OBJECTID;
+		key.type = BTRFS_PERSISTENT_ITEM_KEY;
+		key.offset = device->devid;
+		ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
+		if (ret) {
+			__btrfs_reset_dev_stats(device);
+			device->dev_stats_valid = 1;
+			btrfs_release_path(path);
+			continue;
+		}
+		slot = path->slots[0];
+		eb = path->nodes[0];
+		btrfs_item_key_to_cpu(eb, &found_key, slot);
+		item_size = btrfs_item_size_nr(eb, slot);
+
+		ptr = btrfs_item_ptr(eb, slot,
+				     struct btrfs_dev_stats_item);
+
+		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
+			if (item_size >= (1 + i) * sizeof(__le64))
+				btrfs_dev_stat_set(device, i,
+					btrfs_dev_stats_value(eb, ptr, i));
+			else
+				btrfs_dev_stat_reset(device, i);
+		}
+
+		device->dev_stats_valid = 1;
+		btrfs_dev_stat_print_on_load(device);
+		btrfs_release_path(path);
+	}
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+out:
+	btrfs_free_path(path);
+	return ret < 0 ? ret : 0;
+}
+
+static int update_dev_stat_item(struct btrfs_trans_handle *trans,
+				struct btrfs_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;
+}
+
+/*
+ * called from commit_transaction. Writes all changed device stats to disk.
+ */
+int btrfs_run_dev_stats(struct btrfs_trans_handle *trans,
+			struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_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;
+}
+
+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);
+}
+
+static void btrfs_dev_stat_print_on_error(struct btrfs_device *dev)
+{
+	if (!dev->dev_stats_valid)
+		return;
+	btrfs_err_rl_in_rcu(dev->fs_info,
+		"bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
+			   rcu_str_deref(dev->name),
+			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
+			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
+			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
+			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS),
+			   btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_GENERATION_ERRS));
+}
+
+static void btrfs_dev_stat_print_on_load(struct btrfs_device *dev)
+{
+	int i;
+
+	for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+		if (btrfs_dev_stat_read(dev, i) != 0)
+			break;
+	if (i == BTRFS_DEV_STAT_VALUES_MAX)
+		return; /* all values == 0, suppress message */
+
+	btrfs_info_in_rcu(dev->fs_info,
+		"bdev %s errs: wr %u, rd %u, flush %u, corrupt %u, gen %u",
+	       rcu_str_deref(dev->name),
+	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_WRITE_ERRS),
+	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_READ_ERRS),
+	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_FLUSH_ERRS),
+	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_CORRUPTION_ERRS),
+	       btrfs_dev_stat_read(dev, BTRFS_DEV_STAT_GENERATION_ERRS));
+}
+
+int btrfs_get_dev_stats(struct btrfs_fs_info *fs_info,
+			struct btrfs_ioctl_get_dev_stats *stats)
+{
+	struct btrfs_device *dev;
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	int i;
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	dev = btrfs_find_device(fs_info->fs_devices, stats->devid,
+				NULL, NULL, true);
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	if (!dev) {
+		btrfs_warn(fs_info, "get dev_stats failed, device not found");
+		return -ENODEV;
+	} else if (!dev->dev_stats_valid) {
+		btrfs_warn(fs_info, "get dev_stats failed, not yet valid");
+		return -ENODEV;
+	} else if (stats->flags & BTRFS_DEV_STATS_RESET) {
+		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++) {
+			if (stats->nr_items > i)
+				stats->values[i] =
+					btrfs_dev_stat_read_and_reset(dev, i);
+			else
+				btrfs_dev_stat_reset(dev, i);
+		}
+		btrfs_info(fs_info, "device stats zeroed by %s (%d)",
+			   current->comm, task_pid_nr(current));
+	} else {
+		for (i = 0; i < BTRFS_DEV_STAT_VALUES_MAX; i++)
+			if (stats->nr_items > i)
+				stats->values[i] = btrfs_dev_stat_read(dev, i);
+	}
+	if (stats->nr_items > BTRFS_DEV_STAT_VALUES_MAX)
+		stats->nr_items = BTRFS_DEV_STAT_VALUES_MAX;
+	return 0;
+}
+
+void btrfs_scratch_superblocks(struct block_device *bdev, const char *device_path)
+{
+	struct buffer_head *bh;
+	struct btrfs_super_block *disk_super;
+	int copy_num;
+
+	if (!bdev)
+		return;
+
+	for (copy_num = 0; copy_num < BTRFS_SUPER_MIRROR_MAX;
+		copy_num++) {
+
+		if (btrfs_read_dev_one_super(bdev, copy_num, &bh))
+			continue;
+
+		disk_super = (struct btrfs_super_block *)bh->b_data;
+
+		memset(&disk_super->magic, 0, sizeof(disk_super->magic));
+		set_buffer_dirty(bh);
+		sync_dirty_buffer(bh);
+		brelse(bh);
+	}
+
+	/* Notify udev that device has changed */
+	btrfs_kobject_uevent(bdev, KOBJ_CHANGE);
+
+	/* Update ctime/mtime for device path for libblkid */
+	update_dev_time(device_path);
+}
+
+/*
+ * Update the size of all devices, which is used for writing out the
+ * super blocks.
+ */
+void btrfs_update_commit_device_size(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_device *curr, *next;
+
+	if (list_empty(&fs_devices->resized_devices))
+		return;
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	mutex_lock(&fs_info->chunk_mutex);
+	list_for_each_entry_safe(curr, next, &fs_devices->resized_devices,
+				 resized_list) {
+		list_del_init(&curr->resized_list);
+		curr->commit_total_bytes = curr->disk_total_bytes;
+	}
+	mutex_unlock(&fs_info->chunk_mutex);
+	mutex_unlock(&fs_devices->device_list_mutex);
+}
+
+/* Must be invoked during the transaction commit */
+void btrfs_update_commit_device_bytes_used(struct btrfs_transaction *trans)
+{
+	struct btrfs_fs_info *fs_info = trans->fs_info;
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct btrfs_device *dev;
+	int i;
+
+	if (list_empty(&trans->pending_chunks))
+		return;
+
+	/* In order to kick the device replace finish process */
+	mutex_lock(&fs_info->chunk_mutex);
+	list_for_each_entry(em, &trans->pending_chunks, list) {
+		map = em->map_lookup;
+
+		for (i = 0; i < map->num_stripes; i++) {
+			dev = map->stripes[i].dev;
+			dev->commit_bytes_used = dev->bytes_used;
+			dev->has_pending_chunks = false;
+		}
+	}
+	mutex_unlock(&fs_info->chunk_mutex);
+}
+
+void btrfs_set_fs_info_ptr(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	while (fs_devices) {
+		fs_devices->fs_info = fs_info;
+		fs_devices = fs_devices->seed;
+	}
+}
+
+void btrfs_reset_fs_info_ptr(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	while (fs_devices) {
+		fs_devices->fs_info = NULL;
+		fs_devices = fs_devices->seed;
+	}
+}
+
+/*
+ * Multiplicity factor for simple profiles: DUP, RAID1-like and RAID10.
+ */
+int btrfs_bg_type_to_factor(u64 flags)
+{
+	if (flags & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1 |
+		     BTRFS_BLOCK_GROUP_RAID10))
+		return 2;
+	return 1;
+}
+
+
+static u64 calc_stripe_length(u64 type, u64 chunk_len, int num_stripes)
+{
+	int index = btrfs_bg_flags_to_raid_index(type);
+	int ncopies = btrfs_raid_array[index].ncopies;
+	int data_stripes;
+
+	switch (type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {
+	case BTRFS_BLOCK_GROUP_RAID5:
+		data_stripes = num_stripes - 1;
+		break;
+	case BTRFS_BLOCK_GROUP_RAID6:
+		data_stripes = num_stripes - 2;
+		break;
+	default:
+		data_stripes = num_stripes / ncopies;
+		break;
+	}
+	return div_u64(chunk_len, data_stripes);
+}
+
+static int verify_one_dev_extent(struct btrfs_fs_info *fs_info,
+				 u64 chunk_offset, u64 devid,
+				 u64 physical_offset, u64 physical_len)
+{
+	struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct btrfs_device *dev;
+	u64 stripe_len;
+	bool found = false;
+	int ret = 0;
+	int i;
+
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, chunk_offset, 1);
+	read_unlock(&em_tree->lock);
+
+	if (!em) {
+		btrfs_err(fs_info,
+"dev extent physical offset %llu on devid %llu doesn't have corresponding chunk",
+			  physical_offset, devid);
+		ret = -EUCLEAN;
+		goto out;
+	}
+
+	map = em->map_lookup;
+	stripe_len = calc_stripe_length(map->type, em->len, map->num_stripes);
+	if (physical_len != stripe_len) {
+		btrfs_err(fs_info,
+"dev extent physical offset %llu on devid %llu length doesn't match chunk %llu, have %llu expect %llu",
+			  physical_offset, devid, em->start, physical_len,
+			  stripe_len);
+		ret = -EUCLEAN;
+		goto out;
+	}
+
+	for (i = 0; i < map->num_stripes; i++) {
+		if (map->stripes[i].dev->devid == devid &&
+		    map->stripes[i].physical == physical_offset) {
+			found = true;
+			if (map->verified_stripes >= map->num_stripes) {
+				btrfs_err(fs_info,
+				"too many dev extents for chunk %llu found",
+					  em->start);
+				ret = -EUCLEAN;
+				goto out;
+			}
+			map->verified_stripes++;
+			break;
+		}
+	}
+	if (!found) {
+		btrfs_err(fs_info,
+	"dev extent physical offset %llu devid %llu has no corresponding chunk",
+			physical_offset, devid);
+		ret = -EUCLEAN;
+	}
+
+	/* Make sure no dev extent is beyond device bondary */
+	dev = btrfs_find_device(fs_info->fs_devices, devid, NULL, NULL, true);
+	if (!dev) {
+		btrfs_err(fs_info, "failed to find devid %llu", devid);
+		ret = -EUCLEAN;
+		goto out;
+	}
+
+	/* It's possible this device is a dummy for seed device */
+	if (dev->disk_total_bytes == 0) {
+		dev = btrfs_find_device(fs_info->fs_devices->seed, devid,
+					NULL, NULL, false);
+		if (!dev) {
+			btrfs_err(fs_info, "failed to find seed devid %llu",
+				  devid);
+			ret = -EUCLEAN;
+			goto out;
+		}
+	}
+
+	if (physical_offset + physical_len > dev->disk_total_bytes) {
+		btrfs_err(fs_info,
+"dev extent devid %llu physical offset %llu len %llu is beyond device boundary %llu",
+			  devid, physical_offset, physical_len,
+			  dev->disk_total_bytes);
+		ret = -EUCLEAN;
+		goto out;
+	}
+out:
+	free_extent_map(em);
+	return ret;
+}
+
+static int verify_chunk_dev_extent_mapping(struct btrfs_fs_info *fs_info)
+{
+	struct extent_map_tree *em_tree = &fs_info->mapping_tree.map_tree;
+	struct extent_map *em;
+	struct rb_node *node;
+	int ret = 0;
+
+	read_lock(&em_tree->lock);
+	for (node = rb_first(&em_tree->map); node; node = rb_next(node)) {
+		em = rb_entry(node, struct extent_map, rb_node);
+		if (em->map_lookup->num_stripes !=
+		    em->map_lookup->verified_stripes) {
+			btrfs_err(fs_info,
+			"chunk %llu has missing dev extent, have %d expect %d",
+				  em->start, em->map_lookup->verified_stripes,
+				  em->map_lookup->num_stripes);
+			ret = -EUCLEAN;
+			goto out;
+		}
+	}
+out:
+	read_unlock(&em_tree->lock);
+	return ret;
+}
+
+/*
+ * Ensure that all dev extents are mapped to correct chunk, otherwise
+ * later chunk allocation/free would cause unexpected behavior.
+ *
+ * NOTE: This will iterate through the whole device tree, which should be of
+ * the same size level as the chunk tree.  This slightly increases mount time.
+ */
+int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_path *path;
+	struct btrfs_root *root = fs_info->dev_root;
+	struct btrfs_key key;
+	u64 prev_devid = 0;
+	u64 prev_dev_ext_end = 0;
+	int ret = 0;
+
+	key.objectid = 1;
+	key.type = BTRFS_DEV_EXTENT_KEY;
+	key.offset = 0;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+
+	path->reada = READA_FORWARD;
+	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
+	if (ret < 0)
+		goto out;
+
+	if (path->slots[0] >= btrfs_header_nritems(path->nodes[0])) {
+		ret = btrfs_next_item(root, path);
+		if (ret < 0)
+			goto out;
+		/* No dev extents at all? Not good */
+		if (ret > 0) {
+			ret = -EUCLEAN;
+			goto out;
+		}
+	}
+	while (1) {
+		struct extent_buffer *leaf = path->nodes[0];
+		struct btrfs_dev_extent *dext;
+		int slot = path->slots[0];
+		u64 chunk_offset;
+		u64 physical_offset;
+		u64 physical_len;
+		u64 devid;
+
+		btrfs_item_key_to_cpu(leaf, &key, slot);
+		if (key.type != BTRFS_DEV_EXTENT_KEY)
+			break;
+		devid = key.objectid;
+		physical_offset = key.offset;
+
+		dext = btrfs_item_ptr(leaf, slot, struct btrfs_dev_extent);
+		chunk_offset = btrfs_dev_extent_chunk_offset(leaf, dext);
+		physical_len = btrfs_dev_extent_length(leaf, dext);
+
+		/* Check if this dev extent overlaps with the previous one */
+		if (devid == prev_devid && physical_offset < prev_dev_ext_end) {
+			btrfs_err(fs_info,
+"dev extent devid %llu physical offset %llu overlap with previous dev extent end %llu",
+				  devid, physical_offset, prev_dev_ext_end);
+			ret = -EUCLEAN;
+			goto out;
+		}
+
+		ret = verify_one_dev_extent(fs_info, chunk_offset, devid,
+					    physical_offset, physical_len);
+		if (ret < 0)
+			goto out;
+		prev_devid = devid;
+		prev_dev_ext_end = physical_offset + physical_len;
+
+		ret = btrfs_next_item(root, path);
+		if (ret < 0)
+			goto out;
+		if (ret > 0) {
+			ret = 0;
+			break;
+		}
+	}
+
+	/* Ensure all chunks have corresponding dev extents */
+	ret = verify_chunk_dev_extent_mapping(fs_info);
+out:
+	btrfs_free_path(path);
+	return ret;
+}