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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) STRATO AG 2012.  All rights reserved.
   4 */
   5
   6#include <linux/sched.h>
   7#include <linux/bio.h>
   8#include <linux/slab.h>
   9#include <linux/blkdev.h>
  10#include <linux/kthread.h>
  11#include <linux/math64.h>
  12#include "misc.h"
  13#include "ctree.h"
  14#include "extent_map.h"
  15#include "disk-io.h"
  16#include "transaction.h"
  17#include "print-tree.h"
  18#include "volumes.h"
  19#include "async-thread.h"
  20#include "check-integrity.h"
  21#include "rcu-string.h"
  22#include "dev-replace.h"
  23#include "sysfs.h"
  24
  25/*
  26 * Device replace overview
  27 *
  28 * [Objective]
  29 * To copy all extents (both new and on-disk) from source device to target
  30 * device, while still keeping the filesystem read-write.
  31 *
  32 * [Method]
  33 * There are two main methods involved:
  34 *
  35 * - Write duplication
  36 *
  37 *   All new writes will be written to both target and source devices, so even
  38 *   if replace gets canceled, sources device still contans up-to-date data.
  39 *
  40 *   Location:		handle_ops_on_dev_replace() from __btrfs_map_block()
  41 *   Start:		btrfs_dev_replace_start()
  42 *   End:		btrfs_dev_replace_finishing()
  43 *   Content:		Latest data/metadata
  44 *
  45 * - Copy existing extents
  46 *
  47 *   This happens by re-using scrub facility, as scrub also iterates through
  48 *   existing extents from commit root.
  49 *
  50 *   Location:		scrub_write_block_to_dev_replace() from
  51 *   			scrub_block_complete()
  52 *   Content:		Data/meta from commit root.
  53 *
  54 * Due to the content difference, we need to avoid nocow write when dev-replace
  55 * is happening.  This is done by marking the block group read-only and waiting
  56 * for NOCOW writes.
  57 *
  58 * After replace is done, the finishing part is done by swapping the target and
  59 * source devices.
  60 *
  61 *   Location:		btrfs_dev_replace_update_device_in_mapping_tree() from
  62 *   			btrfs_dev_replace_finishing()
  63 */
  64
  65static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
  66				       int scrub_ret);
  67static void btrfs_dev_replace_update_device_in_mapping_tree(
  68						struct btrfs_fs_info *fs_info,
  69						struct btrfs_device *srcdev,
  70						struct btrfs_device *tgtdev);
  71static int btrfs_dev_replace_kthread(void *data);
  72
  73int btrfs_init_dev_replace(struct btrfs_fs_info *fs_info)
  74{
  75	struct btrfs_key key;
  76	struct btrfs_root *dev_root = fs_info->dev_root;
  77	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
  78	struct extent_buffer *eb;
  79	int slot;
  80	int ret = 0;
  81	struct btrfs_path *path = NULL;
  82	int item_size;
  83	struct btrfs_dev_replace_item *ptr;
  84	u64 src_devid;
  85
  86	path = btrfs_alloc_path();
  87	if (!path) {
  88		ret = -ENOMEM;
  89		goto out;
  90	}
  91
  92	key.objectid = 0;
  93	key.type = BTRFS_DEV_REPLACE_KEY;
  94	key.offset = 0;
  95	ret = btrfs_search_slot(NULL, dev_root, &key, path, 0, 0);
  96	if (ret) {
  97no_valid_dev_replace_entry_found:
  98		ret = 0;
  99		dev_replace->replace_state =
 100			BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 101		dev_replace->cont_reading_from_srcdev_mode =
 102		    BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS;
 103		dev_replace->time_started = 0;
 104		dev_replace->time_stopped = 0;
 105		atomic64_set(&dev_replace->num_write_errors, 0);
 106		atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 107		dev_replace->cursor_left = 0;
 108		dev_replace->committed_cursor_left = 0;
 109		dev_replace->cursor_left_last_write_of_item = 0;
 110		dev_replace->cursor_right = 0;
 111		dev_replace->srcdev = NULL;
 112		dev_replace->tgtdev = NULL;
 113		dev_replace->is_valid = 0;
 114		dev_replace->item_needs_writeback = 0;
 115		goto out;
 116	}
 117	slot = path->slots[0];
 118	eb = path->nodes[0];
 119	item_size = btrfs_item_size_nr(eb, slot);
 120	ptr = btrfs_item_ptr(eb, slot, struct btrfs_dev_replace_item);
 121
 122	if (item_size != sizeof(struct btrfs_dev_replace_item)) {
 123		btrfs_warn(fs_info,
 124			"dev_replace entry found has unexpected size, ignore entry");
 125		goto no_valid_dev_replace_entry_found;
 126	}
 127
 128	src_devid = btrfs_dev_replace_src_devid(eb, ptr);
 129	dev_replace->cont_reading_from_srcdev_mode =
 130		btrfs_dev_replace_cont_reading_from_srcdev_mode(eb, ptr);
 131	dev_replace->replace_state = btrfs_dev_replace_replace_state(eb, ptr);
 132	dev_replace->time_started = btrfs_dev_replace_time_started(eb, ptr);
 133	dev_replace->time_stopped =
 134		btrfs_dev_replace_time_stopped(eb, ptr);
 135	atomic64_set(&dev_replace->num_write_errors,
 136		     btrfs_dev_replace_num_write_errors(eb, ptr));
 137	atomic64_set(&dev_replace->num_uncorrectable_read_errors,
 138		     btrfs_dev_replace_num_uncorrectable_read_errors(eb, ptr));
 139	dev_replace->cursor_left = btrfs_dev_replace_cursor_left(eb, ptr);
 140	dev_replace->committed_cursor_left = dev_replace->cursor_left;
 141	dev_replace->cursor_left_last_write_of_item = dev_replace->cursor_left;
 142	dev_replace->cursor_right = btrfs_dev_replace_cursor_right(eb, ptr);
 143	dev_replace->is_valid = 1;
 144
 145	dev_replace->item_needs_writeback = 0;
 146	switch (dev_replace->replace_state) {
 147	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 148	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 149	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 150		dev_replace->srcdev = NULL;
 151		dev_replace->tgtdev = NULL;
 152		break;
 153	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 154	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 155		dev_replace->srcdev = btrfs_find_device(fs_info->fs_devices,
 156						src_devid, NULL, NULL, true);
 157		dev_replace->tgtdev = btrfs_find_device(fs_info->fs_devices,
 158							BTRFS_DEV_REPLACE_DEVID,
 159							NULL, NULL, true);
 160		/*
 161		 * allow 'btrfs dev replace_cancel' if src/tgt device is
 162		 * missing
 163		 */
 164		if (!dev_replace->srcdev &&
 165		    !btrfs_test_opt(fs_info, DEGRADED)) {
 166			ret = -EIO;
 167			btrfs_warn(fs_info,
 168			   "cannot mount because device replace operation is ongoing and");
 169			btrfs_warn(fs_info,
 170			   "srcdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 171			   src_devid);
 172		}
 173		if (!dev_replace->tgtdev &&
 174		    !btrfs_test_opt(fs_info, DEGRADED)) {
 175			ret = -EIO;
 176			btrfs_warn(fs_info,
 177			   "cannot mount because device replace operation is ongoing and");
 178			btrfs_warn(fs_info,
 179			   "tgtdev (devid %llu) is missing, need to run 'btrfs dev scan'?",
 180				BTRFS_DEV_REPLACE_DEVID);
 181		}
 182		if (dev_replace->tgtdev) {
 183			if (dev_replace->srcdev) {
 184				dev_replace->tgtdev->total_bytes =
 185					dev_replace->srcdev->total_bytes;
 186				dev_replace->tgtdev->disk_total_bytes =
 187					dev_replace->srcdev->disk_total_bytes;
 188				dev_replace->tgtdev->commit_total_bytes =
 189					dev_replace->srcdev->commit_total_bytes;
 190				dev_replace->tgtdev->bytes_used =
 191					dev_replace->srcdev->bytes_used;
 192				dev_replace->tgtdev->commit_bytes_used =
 193					dev_replace->srcdev->commit_bytes_used;
 194			}
 195			set_bit(BTRFS_DEV_STATE_REPLACE_TGT,
 196				&dev_replace->tgtdev->dev_state);
 197
 198			WARN_ON(fs_info->fs_devices->rw_devices == 0);
 199			dev_replace->tgtdev->io_width = fs_info->sectorsize;
 200			dev_replace->tgtdev->io_align = fs_info->sectorsize;
 201			dev_replace->tgtdev->sector_size = fs_info->sectorsize;
 202			dev_replace->tgtdev->fs_info = fs_info;
 203			set_bit(BTRFS_DEV_STATE_IN_FS_METADATA,
 204				&dev_replace->tgtdev->dev_state);
 205		}
 206		break;
 207	}
 208
 209out:
 210	btrfs_free_path(path);
 211	return ret;
 212}
 213
 214/*
 215 * Initialize a new device for device replace target from a given source dev
 216 * and path.
 217 *
 218 * Return 0 and new device in @device_out, otherwise return < 0
 219 */
 220static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 221				  const char *device_path,
 222				  struct btrfs_device *srcdev,
 223				  struct btrfs_device **device_out)
 224{
 225	struct btrfs_device *device;
 226	struct block_device *bdev;
 227	struct list_head *devices;
 228	struct rcu_string *name;
 229	u64 devid = BTRFS_DEV_REPLACE_DEVID;
 230	int ret = 0;
 231
 232	*device_out = NULL;
 233	if (fs_info->fs_devices->seeding) {
 234		btrfs_err(fs_info, "the filesystem is a seed filesystem!");
 235		return -EINVAL;
 236	}
 237
 238	bdev = blkdev_get_by_path(device_path, FMODE_WRITE | FMODE_EXCL,
 239				  fs_info->bdev_holder);
 240	if (IS_ERR(bdev)) {
 241		btrfs_err(fs_info, "target device %s is invalid!", device_path);
 242		return PTR_ERR(bdev);
 243	}
 244
 245	sync_blockdev(bdev);
 246
 247	devices = &fs_info->fs_devices->devices;
 248	list_for_each_entry(device, devices, dev_list) {
 249		if (device->bdev == bdev) {
 250			btrfs_err(fs_info,
 251				  "target device is in the filesystem!");
 252			ret = -EEXIST;
 253			goto error;
 254		}
 255	}
 256
 257
 258	if (i_size_read(bdev->bd_inode) <
 259	    btrfs_device_get_total_bytes(srcdev)) {
 260		btrfs_err(fs_info,
 261			  "target device is smaller than source device!");
 262		ret = -EINVAL;
 263		goto error;
 264	}
 265
 266
 267	device = btrfs_alloc_device(NULL, &devid, NULL);
 268	if (IS_ERR(device)) {
 269		ret = PTR_ERR(device);
 270		goto error;
 271	}
 272
 273	name = rcu_string_strdup(device_path, GFP_KERNEL);
 274	if (!name) {
 275		btrfs_free_device(device);
 276		ret = -ENOMEM;
 277		goto error;
 278	}
 279	rcu_assign_pointer(device->name, name);
 280
 281	set_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state);
 282	device->generation = 0;
 283	device->io_width = fs_info->sectorsize;
 284	device->io_align = fs_info->sectorsize;
 285	device->sector_size = fs_info->sectorsize;
 286	device->total_bytes = btrfs_device_get_total_bytes(srcdev);
 287	device->disk_total_bytes = btrfs_device_get_disk_total_bytes(srcdev);
 288	device->bytes_used = btrfs_device_get_bytes_used(srcdev);
 289	device->commit_total_bytes = srcdev->commit_total_bytes;
 290	device->commit_bytes_used = device->bytes_used;
 291	device->fs_info = fs_info;
 292	device->bdev = bdev;
 293	set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 294	set_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
 295	device->mode = FMODE_EXCL;
 296	device->dev_stats_valid = 1;
 297	set_blocksize(device->bdev, BTRFS_BDEV_BLOCKSIZE);
 298	device->fs_devices = fs_info->fs_devices;
 299
 300	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 301	list_add(&device->dev_list, &fs_info->fs_devices->devices);
 302	fs_info->fs_devices->num_devices++;
 303	fs_info->fs_devices->open_devices++;
 304	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 305
 306	*device_out = device;
 307	return 0;
 308
 309error:
 310	blkdev_put(bdev, FMODE_EXCL);
 311	return ret;
 312}
 313
 314/*
 315 * called from commit_transaction. Writes changed device replace state to
 316 * disk.
 317 */
 318int btrfs_run_dev_replace(struct btrfs_trans_handle *trans)
 319{
 320	struct btrfs_fs_info *fs_info = trans->fs_info;
 321	int ret;
 322	struct btrfs_root *dev_root = fs_info->dev_root;
 323	struct btrfs_path *path;
 324	struct btrfs_key key;
 325	struct extent_buffer *eb;
 326	struct btrfs_dev_replace_item *ptr;
 327	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 328
 329	down_read(&dev_replace->rwsem);
 330	if (!dev_replace->is_valid ||
 331	    !dev_replace->item_needs_writeback) {
 332		up_read(&dev_replace->rwsem);
 333		return 0;
 334	}
 335	up_read(&dev_replace->rwsem);
 336
 337	key.objectid = 0;
 338	key.type = BTRFS_DEV_REPLACE_KEY;
 339	key.offset = 0;
 340
 341	path = btrfs_alloc_path();
 342	if (!path) {
 343		ret = -ENOMEM;
 344		goto out;
 345	}
 346	ret = btrfs_search_slot(trans, dev_root, &key, path, -1, 1);
 347	if (ret < 0) {
 348		btrfs_warn(fs_info,
 349			   "error %d while searching for dev_replace item!",
 350			   ret);
 351		goto out;
 352	}
 353
 354	if (ret == 0 &&
 355	    btrfs_item_size_nr(path->nodes[0], path->slots[0]) < sizeof(*ptr)) {
 356		/*
 357		 * need to delete old one and insert a new one.
 358		 * Since no attempt is made to recover any old state, if the
 359		 * dev_replace state is 'running', the data on the target
 360		 * drive is lost.
 361		 * It would be possible to recover the state: just make sure
 362		 * that the beginning of the item is never changed and always
 363		 * contains all the essential information. Then read this
 364		 * minimal set of information and use it as a base for the
 365		 * new state.
 366		 */
 367		ret = btrfs_del_item(trans, dev_root, path);
 368		if (ret != 0) {
 369			btrfs_warn(fs_info,
 370				   "delete too small dev_replace item failed %d!",
 371				   ret);
 372			goto out;
 373		}
 374		ret = 1;
 375	}
 376
 377	if (ret == 1) {
 378		/* need to insert a new item */
 379		btrfs_release_path(path);
 380		ret = btrfs_insert_empty_item(trans, dev_root, path,
 381					      &key, sizeof(*ptr));
 382		if (ret < 0) {
 383			btrfs_warn(fs_info,
 384				   "insert dev_replace item failed %d!", ret);
 385			goto out;
 386		}
 387	}
 388
 389	eb = path->nodes[0];
 390	ptr = btrfs_item_ptr(eb, path->slots[0],
 391			     struct btrfs_dev_replace_item);
 392
 393	down_write(&dev_replace->rwsem);
 394	if (dev_replace->srcdev)
 395		btrfs_set_dev_replace_src_devid(eb, ptr,
 396			dev_replace->srcdev->devid);
 397	else
 398		btrfs_set_dev_replace_src_devid(eb, ptr, (u64)-1);
 399	btrfs_set_dev_replace_cont_reading_from_srcdev_mode(eb, ptr,
 400		dev_replace->cont_reading_from_srcdev_mode);
 401	btrfs_set_dev_replace_replace_state(eb, ptr,
 402		dev_replace->replace_state);
 403	btrfs_set_dev_replace_time_started(eb, ptr, dev_replace->time_started);
 404	btrfs_set_dev_replace_time_stopped(eb, ptr, dev_replace->time_stopped);
 405	btrfs_set_dev_replace_num_write_errors(eb, ptr,
 406		atomic64_read(&dev_replace->num_write_errors));
 407	btrfs_set_dev_replace_num_uncorrectable_read_errors(eb, ptr,
 408		atomic64_read(&dev_replace->num_uncorrectable_read_errors));
 409	dev_replace->cursor_left_last_write_of_item =
 410		dev_replace->cursor_left;
 411	btrfs_set_dev_replace_cursor_left(eb, ptr,
 412		dev_replace->cursor_left_last_write_of_item);
 413	btrfs_set_dev_replace_cursor_right(eb, ptr,
 414		dev_replace->cursor_right);
 415	dev_replace->item_needs_writeback = 0;
 416	up_write(&dev_replace->rwsem);
 417
 418	btrfs_mark_buffer_dirty(eb);
 419
 420out:
 421	btrfs_free_path(path);
 422
 423	return ret;
 424}
 425
 426static char* btrfs_dev_name(struct btrfs_device *device)
 427{
 428	if (!device || test_bit(BTRFS_DEV_STATE_MISSING, &device->dev_state))
 429		return "<missing disk>";
 430	else
 431		return rcu_str_deref(device->name);
 432}
 433
 434static int btrfs_dev_replace_start(struct btrfs_fs_info *fs_info,
 435		const char *tgtdev_name, u64 srcdevid, const char *srcdev_name,
 436		int read_src)
 437{
 438	struct btrfs_root *root = fs_info->dev_root;
 439	struct btrfs_trans_handle *trans;
 440	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 441	int ret;
 442	struct btrfs_device *tgt_device = NULL;
 443	struct btrfs_device *src_device = NULL;
 444
 445	src_device = btrfs_find_device_by_devspec(fs_info, srcdevid,
 446						  srcdev_name);
 447	if (IS_ERR(src_device))
 448		return PTR_ERR(src_device);
 449
 450	if (btrfs_pinned_by_swapfile(fs_info, src_device)) {
 451		btrfs_warn_in_rcu(fs_info,
 452	  "cannot replace device %s (devid %llu) due to active swapfile",
 453			btrfs_dev_name(src_device), src_device->devid);
 454		return -ETXTBSY;
 455	}
 456
 457	/*
 458	 * Here we commit the transaction to make sure commit_total_bytes
 459	 * of all the devices are updated.
 460	 */
 461	trans = btrfs_attach_transaction(root);
 462	if (!IS_ERR(trans)) {
 463		ret = btrfs_commit_transaction(trans);
 464		if (ret)
 465			return ret;
 466	} else if (PTR_ERR(trans) != -ENOENT) {
 467		return PTR_ERR(trans);
 468	}
 469
 470	ret = btrfs_init_dev_replace_tgtdev(fs_info, tgtdev_name,
 471					    src_device, &tgt_device);
 472	if (ret)
 473		return ret;
 474
 475	down_write(&dev_replace->rwsem);
 476	switch (dev_replace->replace_state) {
 477	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 478	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 479	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 480		break;
 481	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 482	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 483		ASSERT(0);
 484		ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_ALREADY_STARTED;
 485		up_write(&dev_replace->rwsem);
 486		goto leave;
 487	}
 488
 489	dev_replace->cont_reading_from_srcdev_mode = read_src;
 490	dev_replace->srcdev = src_device;
 491	dev_replace->tgtdev = tgt_device;
 492
 493	btrfs_info_in_rcu(fs_info,
 494		      "dev_replace from %s (devid %llu) to %s started",
 495		      btrfs_dev_name(src_device),
 496		      src_device->devid,
 497		      rcu_str_deref(tgt_device->name));
 498
 499	/*
 500	 * from now on, the writes to the srcdev are all duplicated to
 501	 * go to the tgtdev as well (refer to btrfs_map_block()).
 502	 */
 503	dev_replace->replace_state = BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
 504	dev_replace->time_started = ktime_get_real_seconds();
 505	dev_replace->cursor_left = 0;
 506	dev_replace->committed_cursor_left = 0;
 507	dev_replace->cursor_left_last_write_of_item = 0;
 508	dev_replace->cursor_right = 0;
 509	dev_replace->is_valid = 1;
 510	dev_replace->item_needs_writeback = 1;
 511	atomic64_set(&dev_replace->num_write_errors, 0);
 512	atomic64_set(&dev_replace->num_uncorrectable_read_errors, 0);
 513	up_write(&dev_replace->rwsem);
 514
 515	ret = btrfs_sysfs_add_devices_dir(tgt_device->fs_devices, tgt_device);
 516	if (ret)
 517		btrfs_err(fs_info, "kobj add dev failed %d", ret);
 518
 519	btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 520
 521	/* Commit dev_replace state and reserve 1 item for it. */
 522	trans = btrfs_start_transaction(root, 1);
 523	if (IS_ERR(trans)) {
 524		ret = PTR_ERR(trans);
 525		down_write(&dev_replace->rwsem);
 526		dev_replace->replace_state =
 527			BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED;
 528		dev_replace->srcdev = NULL;
 529		dev_replace->tgtdev = NULL;
 530		up_write(&dev_replace->rwsem);
 531		goto leave;
 532	}
 533
 534	ret = btrfs_commit_transaction(trans);
 535	WARN_ON(ret);
 536
 537	/* the disk copy procedure reuses the scrub code */
 538	ret = btrfs_scrub_dev(fs_info, src_device->devid, 0,
 539			      btrfs_device_get_total_bytes(src_device),
 540			      &dev_replace->scrub_progress, 0, 1);
 541
 542	ret = btrfs_dev_replace_finishing(fs_info, ret);
 543	if (ret == -EINPROGRESS)
 544		ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
 545
 546	return ret;
 547
 548leave:
 549	btrfs_destroy_dev_replace_tgtdev(tgt_device);
 550	return ret;
 551}
 552
 553int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 554			    struct btrfs_ioctl_dev_replace_args *args)
 555{
 556	int ret;
 557
 558	switch (args->start.cont_reading_from_srcdev_mode) {
 559	case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS:
 560	case BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID:
 561		break;
 562	default:
 563		return -EINVAL;
 564	}
 565
 566	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 567	    args->start.tgtdev_name[0] == '\0')
 568		return -EINVAL;
 569
 570	ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 571					args->start.srcdevid,
 572					args->start.srcdev_name,
 573					args->start.cont_reading_from_srcdev_mode);
 574	args->result = ret;
 575	/* don't warn if EINPROGRESS, someone else might be running scrub */
 576	if (ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS ||
 577	    ret == BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR)
 578		return 0;
 579
 580	return ret;
 581}
 582
 583/*
 584 * blocked until all in-flight bios operations are finished.
 585 */
 586static void btrfs_rm_dev_replace_blocked(struct btrfs_fs_info *fs_info)
 587{
 588	set_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 589	wait_event(fs_info->dev_replace.replace_wait, !percpu_counter_sum(
 590		   &fs_info->dev_replace.bio_counter));
 591}
 592
 593/*
 594 * we have removed target device, it is safe to allow new bios request.
 595 */
 596static void btrfs_rm_dev_replace_unblocked(struct btrfs_fs_info *fs_info)
 597{
 598	clear_bit(BTRFS_FS_STATE_DEV_REPLACING, &fs_info->fs_state);
 599	wake_up(&fs_info->dev_replace.replace_wait);
 600}
 601
 602/*
 603 * When finishing the device replace, before swapping the source device with the
 604 * target device we must update the chunk allocation state in the target device,
 605 * as it is empty because replace works by directly copying the chunks and not
 606 * through the normal chunk allocation path.
 607 */
 608static int btrfs_set_target_alloc_state(struct btrfs_device *srcdev,
 609					struct btrfs_device *tgtdev)
 610{
 611	struct extent_state *cached_state = NULL;
 612	u64 start = 0;
 613	u64 found_start;
 614	u64 found_end;
 615	int ret = 0;
 616
 617	lockdep_assert_held(&srcdev->fs_info->chunk_mutex);
 618
 619	while (!find_first_extent_bit(&srcdev->alloc_state, start,
 620				      &found_start, &found_end,
 621				      CHUNK_ALLOCATED, &cached_state)) {
 622		ret = set_extent_bits(&tgtdev->alloc_state, found_start,
 623				      found_end, CHUNK_ALLOCATED);
 624		if (ret)
 625			break;
 626		start = found_end + 1;
 627	}
 628
 629	free_extent_state(cached_state);
 630	return ret;
 631}
 632
 633static int btrfs_dev_replace_finishing(struct btrfs_fs_info *fs_info,
 634				       int scrub_ret)
 635{
 636	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 637	struct btrfs_device *tgt_device;
 638	struct btrfs_device *src_device;
 639	struct btrfs_root *root = fs_info->tree_root;
 640	u8 uuid_tmp[BTRFS_UUID_SIZE];
 641	struct btrfs_trans_handle *trans;
 642	int ret = 0;
 643
 644	/* don't allow cancel or unmount to disturb the finishing procedure */
 645	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 646
 647	down_read(&dev_replace->rwsem);
 648	/* was the operation canceled, or is it finished? */
 649	if (dev_replace->replace_state !=
 650	    BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED) {
 651		up_read(&dev_replace->rwsem);
 652		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 653		return 0;
 654	}
 655
 656	tgt_device = dev_replace->tgtdev;
 657	src_device = dev_replace->srcdev;
 658	up_read(&dev_replace->rwsem);
 659
 660	/*
 661	 * flush all outstanding I/O and inode extent mappings before the
 662	 * copy operation is declared as being finished
 663	 */
 664	ret = btrfs_start_delalloc_roots(fs_info, -1);
 665	if (ret) {
 666		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 667		return ret;
 668	}
 669	btrfs_wait_ordered_roots(fs_info, U64_MAX, 0, (u64)-1);
 670
 671	/*
 672	 * We have to use this loop approach because at this point src_device
 673	 * has to be available for transaction commit to complete, yet new
 674	 * chunks shouldn't be allocated on the device.
 675	 */
 676	while (1) {
 677		trans = btrfs_start_transaction(root, 0);
 678		if (IS_ERR(trans)) {
 679			mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 680			return PTR_ERR(trans);
 681		}
 682		ret = btrfs_commit_transaction(trans);
 683		WARN_ON(ret);
 684
 685		/* Prevent write_all_supers() during the finishing procedure */
 686		mutex_lock(&fs_info->fs_devices->device_list_mutex);
 687		/* Prevent new chunks being allocated on the source device */
 688		mutex_lock(&fs_info->chunk_mutex);
 689
 690		if (!list_empty(&src_device->post_commit_list)) {
 691			mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 692			mutex_unlock(&fs_info->chunk_mutex);
 693		} else {
 694			break;
 695		}
 696	}
 697
 698	down_write(&dev_replace->rwsem);
 699	dev_replace->replace_state =
 700		scrub_ret ? BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED
 701			  : BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED;
 702	dev_replace->tgtdev = NULL;
 703	dev_replace->srcdev = NULL;
 704	dev_replace->time_stopped = ktime_get_real_seconds();
 705	dev_replace->item_needs_writeback = 1;
 706
 707	/*
 708	 * Update allocation state in the new device and replace the old device
 709	 * with the new one in the mapping tree.
 710	 */
 711	if (!scrub_ret) {
 712		scrub_ret = btrfs_set_target_alloc_state(src_device, tgt_device);
 713		if (scrub_ret)
 714			goto error;
 715		btrfs_dev_replace_update_device_in_mapping_tree(fs_info,
 716								src_device,
 717								tgt_device);
 718	} else {
 719		if (scrub_ret != -ECANCELED)
 720			btrfs_err_in_rcu(fs_info,
 721				 "btrfs_scrub_dev(%s, %llu, %s) failed %d",
 722				 btrfs_dev_name(src_device),
 723				 src_device->devid,
 724				 rcu_str_deref(tgt_device->name), scrub_ret);
 725error:
 726		up_write(&dev_replace->rwsem);
 727		mutex_unlock(&fs_info->chunk_mutex);
 728		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 729		btrfs_rm_dev_replace_blocked(fs_info);
 730		if (tgt_device)
 731			btrfs_destroy_dev_replace_tgtdev(tgt_device);
 732		btrfs_rm_dev_replace_unblocked(fs_info);
 733		mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 734
 735		return scrub_ret;
 736	}
 737
 738	btrfs_info_in_rcu(fs_info,
 739			  "dev_replace from %s (devid %llu) to %s finished",
 740			  btrfs_dev_name(src_device),
 741			  src_device->devid,
 742			  rcu_str_deref(tgt_device->name));
 743	clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &tgt_device->dev_state);
 744	tgt_device->devid = src_device->devid;
 745	src_device->devid = BTRFS_DEV_REPLACE_DEVID;
 746	memcpy(uuid_tmp, tgt_device->uuid, sizeof(uuid_tmp));
 747	memcpy(tgt_device->uuid, src_device->uuid, sizeof(tgt_device->uuid));
 748	memcpy(src_device->uuid, uuid_tmp, sizeof(src_device->uuid));
 749	btrfs_device_set_total_bytes(tgt_device, src_device->total_bytes);
 750	btrfs_device_set_disk_total_bytes(tgt_device,
 751					  src_device->disk_total_bytes);
 752	btrfs_device_set_bytes_used(tgt_device, src_device->bytes_used);
 753	tgt_device->commit_bytes_used = src_device->bytes_used;
 754
 755	btrfs_assign_next_active_device(src_device, tgt_device);
 756
 757	list_add(&tgt_device->dev_alloc_list, &fs_info->fs_devices->alloc_list);
 758	fs_info->fs_devices->rw_devices++;
 759
 760	up_write(&dev_replace->rwsem);
 761	btrfs_rm_dev_replace_blocked(fs_info);
 762
 763	btrfs_rm_dev_replace_remove_srcdev(src_device);
 764
 765	btrfs_rm_dev_replace_unblocked(fs_info);
 766
 767	/*
 768	 * Increment dev_stats_ccnt so that btrfs_run_dev_stats() will
 769	 * update on-disk dev stats value during commit transaction
 770	 */
 771	atomic_inc(&tgt_device->dev_stats_ccnt);
 772
 773	/*
 774	 * this is again a consistent state where no dev_replace procedure
 775	 * is running, the target device is part of the filesystem, the
 776	 * source device is not part of the filesystem anymore and its 1st
 777	 * superblock is scratched out so that it is no longer marked to
 778	 * belong to this filesystem.
 779	 */
 780	mutex_unlock(&fs_info->chunk_mutex);
 781	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
 782
 783	/* replace the sysfs entry */
 784	btrfs_sysfs_remove_devices_dir(fs_info->fs_devices, src_device);
 785	btrfs_sysfs_update_devid(tgt_device);
 786	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &src_device->dev_state))
 787		btrfs_scratch_superblocks(fs_info, src_device->bdev,
 788					  src_device->name->str);
 789
 790	/* write back the superblocks */
 791	trans = btrfs_start_transaction(root, 0);
 792	if (!IS_ERR(trans))
 793		btrfs_commit_transaction(trans);
 794
 795	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 796
 797	btrfs_rm_dev_replace_free_srcdev(src_device);
 798
 799	return 0;
 800}
 801
 802static void btrfs_dev_replace_update_device_in_mapping_tree(
 803						struct btrfs_fs_info *fs_info,
 804						struct btrfs_device *srcdev,
 805						struct btrfs_device *tgtdev)
 806{
 807	struct extent_map_tree *em_tree = &fs_info->mapping_tree;
 808	struct extent_map *em;
 809	struct map_lookup *map;
 810	u64 start = 0;
 811	int i;
 812
 813	write_lock(&em_tree->lock);
 814	do {
 815		em = lookup_extent_mapping(em_tree, start, (u64)-1);
 816		if (!em)
 817			break;
 818		map = em->map_lookup;
 819		for (i = 0; i < map->num_stripes; i++)
 820			if (srcdev == map->stripes[i].dev)
 821				map->stripes[i].dev = tgtdev;
 822		start = em->start + em->len;
 823		free_extent_map(em);
 824	} while (start);
 825	write_unlock(&em_tree->lock);
 826}
 827
 828/*
 829 * Read progress of device replace status according to the state and last
 830 * stored position. The value format is the same as for
 831 * btrfs_dev_replace::progress_1000
 832 */
 833static u64 btrfs_dev_replace_progress(struct btrfs_fs_info *fs_info)
 834{
 835	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 836	u64 ret = 0;
 837
 838	switch (dev_replace->replace_state) {
 839	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 840	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 841		ret = 0;
 842		break;
 843	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 844		ret = 1000;
 845		break;
 846	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 847	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 848		ret = div64_u64(dev_replace->cursor_left,
 849				div_u64(btrfs_device_get_total_bytes(
 850						dev_replace->srcdev), 1000));
 851		break;
 852	}
 853
 854	return ret;
 855}
 856
 857void btrfs_dev_replace_status(struct btrfs_fs_info *fs_info,
 858			      struct btrfs_ioctl_dev_replace_args *args)
 859{
 860	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 861
 862	down_read(&dev_replace->rwsem);
 863	/* even if !dev_replace_is_valid, the values are good enough for
 864	 * the replace_status ioctl */
 865	args->result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 866	args->status.replace_state = dev_replace->replace_state;
 867	args->status.time_started = dev_replace->time_started;
 868	args->status.time_stopped = dev_replace->time_stopped;
 869	args->status.num_write_errors =
 870		atomic64_read(&dev_replace->num_write_errors);
 871	args->status.num_uncorrectable_read_errors =
 872		atomic64_read(&dev_replace->num_uncorrectable_read_errors);
 873	args->status.progress_1000 = btrfs_dev_replace_progress(fs_info);
 874	up_read(&dev_replace->rwsem);
 875}
 876
 877int btrfs_dev_replace_cancel(struct btrfs_fs_info *fs_info)
 878{
 879	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 880	struct btrfs_device *tgt_device = NULL;
 881	struct btrfs_device *src_device = NULL;
 882	struct btrfs_trans_handle *trans;
 883	struct btrfs_root *root = fs_info->tree_root;
 884	int result;
 885	int ret;
 886
 887	if (sb_rdonly(fs_info->sb))
 888		return -EROFS;
 889
 890	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 891	down_write(&dev_replace->rwsem);
 892	switch (dev_replace->replace_state) {
 893	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 894	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 895	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 896		result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
 897		up_write(&dev_replace->rwsem);
 898		break;
 899	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 900		tgt_device = dev_replace->tgtdev;
 901		src_device = dev_replace->srcdev;
 902		up_write(&dev_replace->rwsem);
 903		ret = btrfs_scrub_cancel(fs_info);
 904		if (ret < 0) {
 905			result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NOT_STARTED;
 906		} else {
 907			result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 908			/*
 909			 * btrfs_dev_replace_finishing() will handle the
 910			 * cleanup part
 911			 */
 912			btrfs_info_in_rcu(fs_info,
 913				"dev_replace from %s (devid %llu) to %s canceled",
 914				btrfs_dev_name(src_device), src_device->devid,
 915				btrfs_dev_name(tgt_device));
 916		}
 917		break;
 918	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 919		/*
 920		 * Scrub doing the replace isn't running so we need to do the
 921		 * cleanup step of btrfs_dev_replace_finishing() here
 922		 */
 923		result = BTRFS_IOCTL_DEV_REPLACE_RESULT_NO_ERROR;
 924		tgt_device = dev_replace->tgtdev;
 925		src_device = dev_replace->srcdev;
 926		dev_replace->tgtdev = NULL;
 927		dev_replace->srcdev = NULL;
 928		dev_replace->replace_state =
 929				BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED;
 930		dev_replace->time_stopped = ktime_get_real_seconds();
 931		dev_replace->item_needs_writeback = 1;
 932
 933		up_write(&dev_replace->rwsem);
 934
 935		/* Scrub for replace must not be running in suspended state */
 936		ret = btrfs_scrub_cancel(fs_info);
 937		ASSERT(ret != -ENOTCONN);
 938
 939		trans = btrfs_start_transaction(root, 0);
 940		if (IS_ERR(trans)) {
 941			mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 942			return PTR_ERR(trans);
 943		}
 944		ret = btrfs_commit_transaction(trans);
 945		WARN_ON(ret);
 946
 947		btrfs_info_in_rcu(fs_info,
 948		"suspended dev_replace from %s (devid %llu) to %s canceled",
 949			btrfs_dev_name(src_device), src_device->devid,
 950			btrfs_dev_name(tgt_device));
 951
 952		if (tgt_device)
 953			btrfs_destroy_dev_replace_tgtdev(tgt_device);
 954		break;
 955	default:
 956		up_write(&dev_replace->rwsem);
 957		result = -EINVAL;
 958	}
 959
 960	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 961	return result;
 962}
 963
 964void btrfs_dev_replace_suspend_for_unmount(struct btrfs_fs_info *fs_info)
 965{
 966	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 967
 968	mutex_lock(&dev_replace->lock_finishing_cancel_unmount);
 969	down_write(&dev_replace->rwsem);
 970
 971	switch (dev_replace->replace_state) {
 972	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
 973	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
 974	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
 975	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
 976		break;
 977	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
 978		dev_replace->replace_state =
 979			BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
 980		dev_replace->time_stopped = ktime_get_real_seconds();
 981		dev_replace->item_needs_writeback = 1;
 982		btrfs_info(fs_info, "suspending dev_replace for unmount");
 983		break;
 984	}
 985
 986	up_write(&dev_replace->rwsem);
 987	mutex_unlock(&dev_replace->lock_finishing_cancel_unmount);
 988}
 989
 990/* resume dev_replace procedure that was interrupted by unmount */
 991int btrfs_resume_dev_replace_async(struct btrfs_fs_info *fs_info)
 992{
 993	struct task_struct *task;
 994	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
 995
 996	down_write(&dev_replace->rwsem);
 997
 998	switch (dev_replace->replace_state) {
 999	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1000	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1001	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1002		up_write(&dev_replace->rwsem);
1003		return 0;
1004	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1005		break;
1006	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1007		dev_replace->replace_state =
1008			BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED;
1009		break;
1010	}
1011	if (!dev_replace->tgtdev || !dev_replace->tgtdev->bdev) {
1012		btrfs_info(fs_info,
1013			   "cannot continue dev_replace, tgtdev is missing");
1014		btrfs_info(fs_info,
1015			   "you may cancel the operation after 'mount -o degraded'");
1016		dev_replace->replace_state =
1017					BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1018		up_write(&dev_replace->rwsem);
1019		return 0;
1020	}
1021	up_write(&dev_replace->rwsem);
1022
1023	/*
1024	 * This could collide with a paused balance, but the exclusive op logic
1025	 * should never allow both to start and pause. We don't want to allow
1026	 * dev-replace to start anyway.
1027	 */
1028	if (test_and_set_bit(BTRFS_FS_EXCL_OP, &fs_info->flags)) {
1029		down_write(&dev_replace->rwsem);
1030		dev_replace->replace_state =
1031					BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED;
1032		up_write(&dev_replace->rwsem);
1033		btrfs_info(fs_info,
1034		"cannot resume dev-replace, other exclusive operation running");
1035		return 0;
1036	}
1037
1038	task = kthread_run(btrfs_dev_replace_kthread, fs_info, "btrfs-devrepl");
1039	return PTR_ERR_OR_ZERO(task);
1040}
1041
1042static int btrfs_dev_replace_kthread(void *data)
1043{
1044	struct btrfs_fs_info *fs_info = data;
1045	struct btrfs_dev_replace *dev_replace = &fs_info->dev_replace;
1046	u64 progress;
1047	int ret;
1048
1049	progress = btrfs_dev_replace_progress(fs_info);
1050	progress = div_u64(progress, 10);
1051	btrfs_info_in_rcu(fs_info,
1052		"continuing dev_replace from %s (devid %llu) to target %s @%u%%",
1053		btrfs_dev_name(dev_replace->srcdev),
1054		dev_replace->srcdev->devid,
1055		btrfs_dev_name(dev_replace->tgtdev),
1056		(unsigned int)progress);
1057
1058	ret = btrfs_scrub_dev(fs_info, dev_replace->srcdev->devid,
1059			      dev_replace->committed_cursor_left,
1060			      btrfs_device_get_total_bytes(dev_replace->srcdev),
1061			      &dev_replace->scrub_progress, 0, 1);
1062	ret = btrfs_dev_replace_finishing(fs_info, ret);
1063	WARN_ON(ret && ret != -ECANCELED);
1064
1065	clear_bit(BTRFS_FS_EXCL_OP, &fs_info->flags);
1066	return 0;
1067}
1068
1069int __pure btrfs_dev_replace_is_ongoing(struct btrfs_dev_replace *dev_replace)
1070{
1071	if (!dev_replace->is_valid)
1072		return 0;
1073
1074	switch (dev_replace->replace_state) {
1075	case BTRFS_IOCTL_DEV_REPLACE_STATE_NEVER_STARTED:
1076	case BTRFS_IOCTL_DEV_REPLACE_STATE_FINISHED:
1077	case BTRFS_IOCTL_DEV_REPLACE_STATE_CANCELED:
1078		return 0;
1079	case BTRFS_IOCTL_DEV_REPLACE_STATE_STARTED:
1080	case BTRFS_IOCTL_DEV_REPLACE_STATE_SUSPENDED:
1081		/*
1082		 * return true even if tgtdev is missing (this is
1083		 * something that can happen if the dev_replace
1084		 * procedure is suspended by an umount and then
1085		 * the tgtdev is missing (or "btrfs dev scan") was
1086		 * not called and the filesystem is remounted
1087		 * in degraded state. This does not stop the
1088		 * dev_replace procedure. It needs to be canceled
1089		 * manually if the cancellation is wanted.
1090		 */
1091		break;
1092	}
1093	return 1;
1094}
1095
1096void btrfs_bio_counter_inc_noblocked(struct btrfs_fs_info *fs_info)
1097{
1098	percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1099}
1100
1101void btrfs_bio_counter_sub(struct btrfs_fs_info *fs_info, s64 amount)
1102{
1103	percpu_counter_sub(&fs_info->dev_replace.bio_counter, amount);
1104	cond_wake_up_nomb(&fs_info->dev_replace.replace_wait);
1105}
1106
1107void btrfs_bio_counter_inc_blocked(struct btrfs_fs_info *fs_info)
1108{
1109	while (1) {
1110		percpu_counter_inc(&fs_info->dev_replace.bio_counter);
1111		if (likely(!test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1112				     &fs_info->fs_state)))
1113			break;
1114
1115		btrfs_bio_counter_dec(fs_info);
1116		wait_event(fs_info->dev_replace.replace_wait,
1117			   !test_bit(BTRFS_FS_STATE_DEV_REPLACING,
1118				     &fs_info->fs_state));
1119	}
1120}