diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
new file mode 100644
index 0000000..d4a7f7c
--- /dev/null
+++ b/fs/btrfs/disk-io.c
@@ -0,0 +1,4511 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/radix-tree.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
+#include <linux/workqueue.h>
+#include <linux/kthread.h>
+#include <linux/slab.h>
+#include <linux/migrate.h>
+#include <linux/ratelimit.h>
+#include <linux/uuid.h>
+#include <linux/semaphore.h>
+#include <linux/error-injection.h>
+#include <linux/crc32c.h>
+#include <asm/unaligned.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "btrfs_inode.h"
+#include "volumes.h"
+#include "print-tree.h"
+#include "locking.h"
+#include "tree-log.h"
+#include "free-space-cache.h"
+#include "free-space-tree.h"
+#include "inode-map.h"
+#include "check-integrity.h"
+#include "rcu-string.h"
+#include "dev-replace.h"
+#include "raid56.h"
+#include "sysfs.h"
+#include "qgroup.h"
+#include "compression.h"
+#include "tree-checker.h"
+#include "ref-verify.h"
+
+#ifdef CONFIG_X86
+#include <asm/cpufeature.h>
+#endif
+
+#define BTRFS_SUPER_FLAG_SUPP	(BTRFS_HEADER_FLAG_WRITTEN |\
+				 BTRFS_HEADER_FLAG_RELOC |\
+				 BTRFS_SUPER_FLAG_ERROR |\
+				 BTRFS_SUPER_FLAG_SEEDING |\
+				 BTRFS_SUPER_FLAG_METADUMP |\
+				 BTRFS_SUPER_FLAG_METADUMP_V2)
+
+static const struct extent_io_ops btree_extent_io_ops;
+static void end_workqueue_fn(struct btrfs_work *work);
+static void btrfs_destroy_ordered_extents(struct btrfs_root *root);
+static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
+				      struct btrfs_fs_info *fs_info);
+static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root);
+static int btrfs_destroy_marked_extents(struct btrfs_fs_info *fs_info,
+					struct extent_io_tree *dirty_pages,
+					int mark);
+static int btrfs_destroy_pinned_extent(struct btrfs_fs_info *fs_info,
+				       struct extent_io_tree *pinned_extents);
+static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info);
+static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info);
+
+/*
+ * btrfs_end_io_wq structs are used to do processing in task context when an IO
+ * is complete.  This is used during reads to verify checksums, and it is used
+ * by writes to insert metadata for new file extents after IO is complete.
+ */
+struct btrfs_end_io_wq {
+	struct bio *bio;
+	bio_end_io_t *end_io;
+	void *private;
+	struct btrfs_fs_info *info;
+	blk_status_t status;
+	enum btrfs_wq_endio_type metadata;
+	struct btrfs_work work;
+};
+
+static struct kmem_cache *btrfs_end_io_wq_cache;
+
+int __init btrfs_end_io_wq_init(void)
+{
+	btrfs_end_io_wq_cache = kmem_cache_create("btrfs_end_io_wq",
+					sizeof(struct btrfs_end_io_wq),
+					0,
+					SLAB_MEM_SPREAD,
+					NULL);
+	if (!btrfs_end_io_wq_cache)
+		return -ENOMEM;
+	return 0;
+}
+
+void __cold btrfs_end_io_wq_exit(void)
+{
+	kmem_cache_destroy(btrfs_end_io_wq_cache);
+}
+
+/*
+ * async submit bios are used to offload expensive checksumming
+ * onto the worker threads.  They checksum file and metadata bios
+ * just before they are sent down the IO stack.
+ */
+struct async_submit_bio {
+	void *private_data;
+	struct bio *bio;
+	extent_submit_bio_start_t *submit_bio_start;
+	int mirror_num;
+	/*
+	 * bio_offset is optional, can be used if the pages in the bio
+	 * can't tell us where in the file the bio should go
+	 */
+	u64 bio_offset;
+	struct btrfs_work work;
+	blk_status_t status;
+};
+
+/*
+ * Lockdep class keys for extent_buffer->lock's in this root.  For a given
+ * eb, the lockdep key is determined by the btrfs_root it belongs to and
+ * the level the eb occupies in the tree.
+ *
+ * Different roots are used for different purposes and may nest inside each
+ * other and they require separate keysets.  As lockdep keys should be
+ * static, assign keysets according to the purpose of the root as indicated
+ * by btrfs_root->objectid.  This ensures that all special purpose roots
+ * have separate keysets.
+ *
+ * Lock-nesting across peer nodes is always done with the immediate parent
+ * node locked thus preventing deadlock.  As lockdep doesn't know this, use
+ * subclass to avoid triggering lockdep warning in such cases.
+ *
+ * The key is set by the readpage_end_io_hook after the buffer has passed
+ * csum validation but before the pages are unlocked.  It is also set by
+ * btrfs_init_new_buffer on freshly allocated blocks.
+ *
+ * We also add a check to make sure the highest level of the tree is the
+ * same as our lockdep setup here.  If BTRFS_MAX_LEVEL changes, this code
+ * needs update as well.
+ */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# if BTRFS_MAX_LEVEL != 8
+#  error
+# endif
+
+static struct btrfs_lockdep_keyset {
+	u64			id;		/* root objectid */
+	const char		*name_stem;	/* lock name stem */
+	char			names[BTRFS_MAX_LEVEL + 1][20];
+	struct lock_class_key	keys[BTRFS_MAX_LEVEL + 1];
+} btrfs_lockdep_keysets[] = {
+	{ .id = BTRFS_ROOT_TREE_OBJECTID,	.name_stem = "root"	},
+	{ .id = BTRFS_EXTENT_TREE_OBJECTID,	.name_stem = "extent"	},
+	{ .id = BTRFS_CHUNK_TREE_OBJECTID,	.name_stem = "chunk"	},
+	{ .id = BTRFS_DEV_TREE_OBJECTID,	.name_stem = "dev"	},
+	{ .id = BTRFS_FS_TREE_OBJECTID,		.name_stem = "fs"	},
+	{ .id = BTRFS_CSUM_TREE_OBJECTID,	.name_stem = "csum"	},
+	{ .id = BTRFS_QUOTA_TREE_OBJECTID,	.name_stem = "quota"	},
+	{ .id = BTRFS_TREE_LOG_OBJECTID,	.name_stem = "log"	},
+	{ .id = BTRFS_TREE_RELOC_OBJECTID,	.name_stem = "treloc"	},
+	{ .id = BTRFS_DATA_RELOC_TREE_OBJECTID,	.name_stem = "dreloc"	},
+	{ .id = BTRFS_UUID_TREE_OBJECTID,	.name_stem = "uuid"	},
+	{ .id = BTRFS_FREE_SPACE_TREE_OBJECTID,	.name_stem = "free-space" },
+	{ .id = 0,				.name_stem = "tree"	},
+};
+
+void __init btrfs_init_lockdep(void)
+{
+	int i, j;
+
+	/* initialize lockdep class names */
+	for (i = 0; i < ARRAY_SIZE(btrfs_lockdep_keysets); i++) {
+		struct btrfs_lockdep_keyset *ks = &btrfs_lockdep_keysets[i];
+
+		for (j = 0; j < ARRAY_SIZE(ks->names); j++)
+			snprintf(ks->names[j], sizeof(ks->names[j]),
+				 "btrfs-%s-%02d", ks->name_stem, j);
+	}
+}
+
+void btrfs_set_buffer_lockdep_class(u64 objectid, struct extent_buffer *eb,
+				    int level)
+{
+	struct btrfs_lockdep_keyset *ks;
+
+	BUG_ON(level >= ARRAY_SIZE(ks->keys));
+
+	/* find the matching keyset, id 0 is the default entry */
+	for (ks = btrfs_lockdep_keysets; ks->id; ks++)
+		if (ks->id == objectid)
+			break;
+
+	lockdep_set_class_and_name(&eb->lock,
+				   &ks->keys[level], ks->names[level]);
+}
+
+#endif
+
+/*
+ * extents on the btree inode are pretty simple, there's one extent
+ * that covers the entire device
+ */
+struct extent_map *btree_get_extent(struct btrfs_inode *inode,
+		struct page *page, size_t pg_offset, u64 start, u64 len,
+		int create)
+{
+	struct btrfs_fs_info *fs_info = inode->root->fs_info;
+	struct extent_map_tree *em_tree = &inode->extent_tree;
+	struct extent_map *em;
+	int ret;
+
+	read_lock(&em_tree->lock);
+	em = lookup_extent_mapping(em_tree, start, len);
+	if (em) {
+		em->bdev = fs_info->fs_devices->latest_bdev;
+		read_unlock(&em_tree->lock);
+		goto out;
+	}
+	read_unlock(&em_tree->lock);
+
+	em = alloc_extent_map();
+	if (!em) {
+		em = ERR_PTR(-ENOMEM);
+		goto out;
+	}
+	em->start = 0;
+	em->len = (u64)-1;
+	em->block_len = (u64)-1;
+	em->block_start = 0;
+	em->bdev = fs_info->fs_devices->latest_bdev;
+
+	write_lock(&em_tree->lock);
+	ret = add_extent_mapping(em_tree, em, 0);
+	if (ret == -EEXIST) {
+		free_extent_map(em);
+		em = lookup_extent_mapping(em_tree, start, len);
+		if (!em)
+			em = ERR_PTR(-EIO);
+	} else if (ret) {
+		free_extent_map(em);
+		em = ERR_PTR(ret);
+	}
+	write_unlock(&em_tree->lock);
+
+out:
+	return em;
+}
+
+u32 btrfs_csum_data(const char *data, u32 seed, size_t len)
+{
+	return crc32c(seed, data, len);
+}
+
+void btrfs_csum_final(u32 crc, u8 *result)
+{
+	put_unaligned_le32(~crc, result);
+}
+
+/*
+ * compute the csum for a btree block, and either verify it or write it
+ * into the csum field of the block.
+ */
+static int csum_tree_block(struct btrfs_fs_info *fs_info,
+			   struct extent_buffer *buf,
+			   int verify)
+{
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
+	char result[BTRFS_CSUM_SIZE];
+	unsigned long len;
+	unsigned long cur_len;
+	unsigned long offset = BTRFS_CSUM_SIZE;
+	char *kaddr;
+	unsigned long map_start;
+	unsigned long map_len;
+	int err;
+	u32 crc = ~(u32)0;
+
+	len = buf->len - offset;
+	while (len > 0) {
+		err = map_private_extent_buffer(buf, offset, 32,
+					&kaddr, &map_start, &map_len);
+		if (err)
+			return err;
+		cur_len = min(len, map_len - (offset - map_start));
+		crc = btrfs_csum_data(kaddr + offset - map_start,
+				      crc, cur_len);
+		len -= cur_len;
+		offset += cur_len;
+	}
+	memset(result, 0, BTRFS_CSUM_SIZE);
+
+	btrfs_csum_final(crc, result);
+
+	if (verify) {
+		if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
+			u32 val;
+			u32 found = 0;
+			memcpy(&found, result, csum_size);
+
+			read_extent_buffer(buf, &val, 0, csum_size);
+			btrfs_warn_rl(fs_info,
+				"%s checksum verify failed on %llu wanted %X found %X level %d",
+				fs_info->sb->s_id, buf->start,
+				val, found, btrfs_header_level(buf));
+			return -EUCLEAN;
+		}
+	} else {
+		write_extent_buffer(buf, result, 0, csum_size);
+	}
+
+	return 0;
+}
+
+/*
+ * we can't consider a given block up to date unless the transid of the
+ * block matches the transid in the parent node's pointer.  This is how we
+ * detect blocks that either didn't get written at all or got written
+ * in the wrong place.
+ */
+static int verify_parent_transid(struct extent_io_tree *io_tree,
+				 struct extent_buffer *eb, u64 parent_transid,
+				 int atomic)
+{
+	struct extent_state *cached_state = NULL;
+	int ret;
+	bool need_lock = (current->journal_info == BTRFS_SEND_TRANS_STUB);
+
+	if (!parent_transid || btrfs_header_generation(eb) == parent_transid)
+		return 0;
+
+	if (atomic)
+		return -EAGAIN;
+
+	if (need_lock) {
+		btrfs_tree_read_lock(eb);
+		btrfs_set_lock_blocking_rw(eb, BTRFS_READ_LOCK);
+	}
+
+	lock_extent_bits(io_tree, eb->start, eb->start + eb->len - 1,
+			 &cached_state);
+	if (extent_buffer_uptodate(eb) &&
+	    btrfs_header_generation(eb) == parent_transid) {
+		ret = 0;
+		goto out;
+	}
+	btrfs_err_rl(eb->fs_info,
+		"parent transid verify failed on %llu wanted %llu found %llu",
+			eb->start,
+			parent_transid, btrfs_header_generation(eb));
+	ret = 1;
+
+	/*
+	 * Things reading via commit roots that don't have normal protection,
+	 * like send, can have a really old block in cache that may point at a
+	 * block that has been freed and re-allocated.  So don't clear uptodate
+	 * if we find an eb that is under IO (dirty/writeback) because we could
+	 * end up reading in the stale data and then writing it back out and
+	 * making everybody very sad.
+	 */
+	if (!extent_buffer_under_io(eb))
+		clear_extent_buffer_uptodate(eb);
+out:
+	unlock_extent_cached(io_tree, eb->start, eb->start + eb->len - 1,
+			     &cached_state);
+	if (need_lock)
+		btrfs_tree_read_unlock_blocking(eb);
+	return ret;
+}
+
+/*
+ * Return 0 if the superblock checksum type matches the checksum value of that
+ * algorithm. Pass the raw disk superblock data.
+ */
+static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
+				  char *raw_disk_sb)
+{
+	struct btrfs_super_block *disk_sb =
+		(struct btrfs_super_block *)raw_disk_sb;
+	u16 csum_type = btrfs_super_csum_type(disk_sb);
+	int ret = 0;
+
+	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
+		u32 crc = ~(u32)0;
+		char result[sizeof(crc)];
+
+		/*
+		 * The super_block structure does not span the whole
+		 * BTRFS_SUPER_INFO_SIZE range, we expect that the unused space
+		 * is filled with zeros and is included in the checksum.
+		 */
+		crc = btrfs_csum_data(raw_disk_sb + BTRFS_CSUM_SIZE,
+				crc, BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+		btrfs_csum_final(crc, result);
+
+		if (memcmp(raw_disk_sb, result, sizeof(result)))
+			ret = 1;
+	}
+
+	if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
+		btrfs_err(fs_info, "unsupported checksum algorithm %u",
+				csum_type);
+		ret = 1;
+	}
+
+	return ret;
+}
+
+static int verify_level_key(struct btrfs_fs_info *fs_info,
+			    struct extent_buffer *eb, int level,
+			    struct btrfs_key *first_key, u64 parent_transid)
+{
+	int found_level;
+	struct btrfs_key found_key;
+	int ret;
+
+	found_level = btrfs_header_level(eb);
+	if (found_level != level) {
+#ifdef CONFIG_BTRFS_DEBUG
+		WARN_ON(1);
+		btrfs_err(fs_info,
+"tree level mismatch detected, bytenr=%llu level expected=%u has=%u",
+			  eb->start, level, found_level);
+#endif
+		return -EIO;
+	}
+
+	if (!first_key)
+		return 0;
+
+	/*
+	 * For live tree block (new tree blocks in current transaction),
+	 * we need proper lock context to avoid race, which is impossible here.
+	 * So we only checks tree blocks which is read from disk, whose
+	 * generation <= fs_info->last_trans_committed.
+	 */
+	if (btrfs_header_generation(eb) > fs_info->last_trans_committed)
+		return 0;
+	if (found_level)
+		btrfs_node_key_to_cpu(eb, &found_key, 0);
+	else
+		btrfs_item_key_to_cpu(eb, &found_key, 0);
+	ret = btrfs_comp_cpu_keys(first_key, &found_key);
+
+#ifdef CONFIG_BTRFS_DEBUG
+	if (ret) {
+		WARN_ON(1);
+		btrfs_err(fs_info,
+"tree first key mismatch detected, bytenr=%llu parent_transid=%llu key expected=(%llu,%u,%llu) has=(%llu,%u,%llu)",
+			  eb->start, parent_transid, first_key->objectid,
+			  first_key->type, first_key->offset,
+			  found_key.objectid, found_key.type,
+			  found_key.offset);
+	}
+#endif
+	return ret;
+}
+
+/*
+ * helper to read a given tree block, doing retries as required when
+ * the checksums don't match and we have alternate mirrors to try.
+ *
+ * @parent_transid:	expected transid, skip check if 0
+ * @level:		expected level, mandatory check
+ * @first_key:		expected key of first slot, skip check if NULL
+ */
+static int btree_read_extent_buffer_pages(struct btrfs_fs_info *fs_info,
+					  struct extent_buffer *eb,
+					  u64 parent_transid, int level,
+					  struct btrfs_key *first_key)
+{
+	struct extent_io_tree *io_tree;
+	int failed = 0;
+	int ret;
+	int num_copies = 0;
+	int mirror_num = 0;
+	int failed_mirror = 0;
+
+	io_tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
+	while (1) {
+		clear_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
+		ret = read_extent_buffer_pages(io_tree, eb, WAIT_COMPLETE,
+					       mirror_num);
+		if (!ret) {
+			if (verify_parent_transid(io_tree, eb,
+						   parent_transid, 0))
+				ret = -EIO;
+			else if (verify_level_key(fs_info, eb, level,
+						  first_key, parent_transid))
+				ret = -EUCLEAN;
+			else
+				break;
+		}
+
+		num_copies = btrfs_num_copies(fs_info,
+					      eb->start, eb->len);
+		if (num_copies == 1)
+			break;
+
+		if (!failed_mirror) {
+			failed = 1;
+			failed_mirror = eb->read_mirror;
+		}
+
+		mirror_num++;
+		if (mirror_num == failed_mirror)
+			mirror_num++;
+
+		if (mirror_num > num_copies)
+			break;
+	}
+
+	if (failed && !ret && failed_mirror)
+		repair_eb_io_failure(fs_info, eb, failed_mirror);
+
+	return ret;
+}
+
+/*
+ * checksum a dirty tree block before IO.  This has extra checks to make sure
+ * we only fill in the checksum field in the first page of a multi-page block
+ */
+
+static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
+{
+	u64 start = page_offset(page);
+	u64 found_start;
+	struct extent_buffer *eb;
+
+	eb = (struct extent_buffer *)page->private;
+	if (page != eb->pages[0])
+		return 0;
+
+	found_start = btrfs_header_bytenr(eb);
+	/*
+	 * Please do not consolidate these warnings into a single if.
+	 * It is useful to know what went wrong.
+	 */
+	if (WARN_ON(found_start != start))
+		return -EUCLEAN;
+	if (WARN_ON(!PageUptodate(page)))
+		return -EUCLEAN;
+
+	ASSERT(memcmp_extent_buffer(eb, fs_info->fsid,
+			btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
+
+	return csum_tree_block(fs_info, eb, 0);
+}
+
+static int check_tree_block_fsid(struct btrfs_fs_info *fs_info,
+				 struct extent_buffer *eb)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	u8 fsid[BTRFS_FSID_SIZE];
+	int ret = 1;
+
+	read_extent_buffer(eb, fsid, btrfs_header_fsid(), BTRFS_FSID_SIZE);
+	while (fs_devices) {
+		if (!memcmp(fsid, fs_devices->fsid, BTRFS_FSID_SIZE)) {
+			ret = 0;
+			break;
+		}
+		fs_devices = fs_devices->seed;
+	}
+	return ret;
+}
+
+static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
+				      u64 phy_offset, struct page *page,
+				      u64 start, u64 end, int mirror)
+{
+	u64 found_start;
+	int found_level;
+	struct extent_buffer *eb;
+	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	int ret = 0;
+	int reads_done;
+
+	if (!page->private)
+		goto out;
+
+	eb = (struct extent_buffer *)page->private;
+
+	/* the pending IO might have been the only thing that kept this buffer
+	 * in memory.  Make sure we have a ref for all this other checks
+	 */
+	extent_buffer_get(eb);
+
+	reads_done = atomic_dec_and_test(&eb->io_pages);
+	if (!reads_done)
+		goto err;
+
+	eb->read_mirror = mirror;
+	if (test_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags)) {
+		ret = -EIO;
+		goto err;
+	}
+
+	found_start = btrfs_header_bytenr(eb);
+	if (found_start != eb->start) {
+		btrfs_err_rl(fs_info, "bad tree block start, want %llu have %llu",
+			     eb->start, found_start);
+		ret = -EIO;
+		goto err;
+	}
+	if (check_tree_block_fsid(fs_info, eb)) {
+		btrfs_err_rl(fs_info, "bad fsid on block %llu",
+			     eb->start);
+		ret = -EIO;
+		goto err;
+	}
+	found_level = btrfs_header_level(eb);
+	if (found_level >= BTRFS_MAX_LEVEL) {
+		btrfs_err(fs_info, "bad tree block level %d on %llu",
+			  (int)btrfs_header_level(eb), eb->start);
+		ret = -EIO;
+		goto err;
+	}
+
+	btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb),
+				       eb, found_level);
+
+	ret = csum_tree_block(fs_info, eb, 1);
+	if (ret)
+		goto err;
+
+	/*
+	 * If this is a leaf block and it is corrupt, set the corrupt bit so
+	 * that we don't try and read the other copies of this block, just
+	 * return -EIO.
+	 */
+	if (found_level == 0 && btrfs_check_leaf_full(fs_info, eb)) {
+		set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
+		ret = -EIO;
+	}
+
+	if (found_level > 0 && btrfs_check_node(fs_info, eb))
+		ret = -EIO;
+
+	if (!ret)
+		set_extent_buffer_uptodate(eb);
+err:
+	if (reads_done &&
+	    test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
+		btree_readahead_hook(eb, ret);
+
+	if (ret) {
+		/*
+		 * our io error hook is going to dec the io pages
+		 * again, we have to make sure it has something
+		 * to decrement
+		 */
+		atomic_inc(&eb->io_pages);
+		clear_extent_buffer_uptodate(eb);
+	}
+	free_extent_buffer(eb);
+out:
+	return ret;
+}
+
+static int btree_io_failed_hook(struct page *page, int failed_mirror)
+{
+	struct extent_buffer *eb;
+
+	eb = (struct extent_buffer *)page->private;
+	set_bit(EXTENT_BUFFER_READ_ERR, &eb->bflags);
+	eb->read_mirror = failed_mirror;
+	atomic_dec(&eb->io_pages);
+	if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags))
+		btree_readahead_hook(eb, -EIO);
+	return -EIO;	/* we fixed nothing */
+}
+
+static void end_workqueue_bio(struct bio *bio)
+{
+	struct btrfs_end_io_wq *end_io_wq = bio->bi_private;
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_workqueue *wq;
+	btrfs_work_func_t func;
+
+	fs_info = end_io_wq->info;
+	end_io_wq->status = bio->bi_status;
+
+	if (bio_op(bio) == REQ_OP_WRITE) {
+		if (end_io_wq->metadata == BTRFS_WQ_ENDIO_METADATA) {
+			wq = fs_info->endio_meta_write_workers;
+			func = btrfs_endio_meta_write_helper;
+		} else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_FREE_SPACE) {
+			wq = fs_info->endio_freespace_worker;
+			func = btrfs_freespace_write_helper;
+		} else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56) {
+			wq = fs_info->endio_raid56_workers;
+			func = btrfs_endio_raid56_helper;
+		} else {
+			wq = fs_info->endio_write_workers;
+			func = btrfs_endio_write_helper;
+		}
+	} else {
+		if (unlikely(end_io_wq->metadata ==
+			     BTRFS_WQ_ENDIO_DIO_REPAIR)) {
+			wq = fs_info->endio_repair_workers;
+			func = btrfs_endio_repair_helper;
+		} else if (end_io_wq->metadata == BTRFS_WQ_ENDIO_RAID56) {
+			wq = fs_info->endio_raid56_workers;
+			func = btrfs_endio_raid56_helper;
+		} else if (end_io_wq->metadata) {
+			wq = fs_info->endio_meta_workers;
+			func = btrfs_endio_meta_helper;
+		} else {
+			wq = fs_info->endio_workers;
+			func = btrfs_endio_helper;
+		}
+	}
+
+	btrfs_init_work(&end_io_wq->work, func, end_workqueue_fn, NULL, NULL);
+	btrfs_queue_work(wq, &end_io_wq->work);
+}
+
+blk_status_t btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
+			enum btrfs_wq_endio_type metadata)
+{
+	struct btrfs_end_io_wq *end_io_wq;
+
+	end_io_wq = kmem_cache_alloc(btrfs_end_io_wq_cache, GFP_NOFS);
+	if (!end_io_wq)
+		return BLK_STS_RESOURCE;
+
+	end_io_wq->private = bio->bi_private;
+	end_io_wq->end_io = bio->bi_end_io;
+	end_io_wq->info = info;
+	end_io_wq->status = 0;
+	end_io_wq->bio = bio;
+	end_io_wq->metadata = metadata;
+
+	bio->bi_private = end_io_wq;
+	bio->bi_end_io = end_workqueue_bio;
+	return 0;
+}
+
+static void run_one_async_start(struct btrfs_work *work)
+{
+	struct async_submit_bio *async;
+	blk_status_t ret;
+
+	async = container_of(work, struct  async_submit_bio, work);
+	ret = async->submit_bio_start(async->private_data, async->bio,
+				      async->bio_offset);
+	if (ret)
+		async->status = ret;
+}
+
+static void run_one_async_done(struct btrfs_work *work)
+{
+	struct async_submit_bio *async;
+
+	async = container_of(work, struct  async_submit_bio, work);
+
+	/* If an error occurred we just want to clean up the bio and move on */
+	if (async->status) {
+		async->bio->bi_status = async->status;
+		bio_endio(async->bio);
+		return;
+	}
+
+	btrfs_submit_bio_done(async->private_data, async->bio, async->mirror_num);
+}
+
+static void run_one_async_free(struct btrfs_work *work)
+{
+	struct async_submit_bio *async;
+
+	async = container_of(work, struct  async_submit_bio, work);
+	kfree(async);
+}
+
+blk_status_t btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
+				 int mirror_num, unsigned long bio_flags,
+				 u64 bio_offset, void *private_data,
+				 extent_submit_bio_start_t *submit_bio_start)
+{
+	struct async_submit_bio *async;
+
+	async = kmalloc(sizeof(*async), GFP_NOFS);
+	if (!async)
+		return BLK_STS_RESOURCE;
+
+	async->private_data = private_data;
+	async->bio = bio;
+	async->mirror_num = mirror_num;
+	async->submit_bio_start = submit_bio_start;
+
+	btrfs_init_work(&async->work, btrfs_worker_helper, run_one_async_start,
+			run_one_async_done, run_one_async_free);
+
+	async->bio_offset = bio_offset;
+
+	async->status = 0;
+
+	if (op_is_sync(bio->bi_opf))
+		btrfs_set_work_high_priority(&async->work);
+
+	btrfs_queue_work(fs_info->workers, &async->work);
+	return 0;
+}
+
+static blk_status_t btree_csum_one_bio(struct bio *bio)
+{
+	struct bio_vec *bvec;
+	struct btrfs_root *root;
+	int i, ret = 0;
+
+	ASSERT(!bio_flagged(bio, BIO_CLONED));
+	bio_for_each_segment_all(bvec, bio, i) {
+		root = BTRFS_I(bvec->bv_page->mapping->host)->root;
+		ret = csum_dirty_buffer(root->fs_info, bvec->bv_page);
+		if (ret)
+			break;
+	}
+
+	return errno_to_blk_status(ret);
+}
+
+static blk_status_t btree_submit_bio_start(void *private_data, struct bio *bio,
+					     u64 bio_offset)
+{
+	/*
+	 * when we're called for a write, we're already in the async
+	 * submission context.  Just jump into btrfs_map_bio
+	 */
+	return btree_csum_one_bio(bio);
+}
+
+static int check_async_write(struct btrfs_inode *bi)
+{
+	if (atomic_read(&bi->sync_writers))
+		return 0;
+#ifdef CONFIG_X86
+	if (static_cpu_has(X86_FEATURE_XMM4_2))
+		return 0;
+#endif
+	return 1;
+}
+
+static blk_status_t btree_submit_bio_hook(void *private_data, struct bio *bio,
+					  int mirror_num, unsigned long bio_flags,
+					  u64 bio_offset)
+{
+	struct inode *inode = private_data;
+	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
+	int async = check_async_write(BTRFS_I(inode));
+	blk_status_t ret;
+
+	if (bio_op(bio) != REQ_OP_WRITE) {
+		/*
+		 * called for a read, do the setup so that checksum validation
+		 * can happen in the async kernel threads
+		 */
+		ret = btrfs_bio_wq_end_io(fs_info, bio,
+					  BTRFS_WQ_ENDIO_METADATA);
+		if (ret)
+			goto out_w_error;
+		ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
+	} else if (!async) {
+		ret = btree_csum_one_bio(bio);
+		if (ret)
+			goto out_w_error;
+		ret = btrfs_map_bio(fs_info, bio, mirror_num, 0);
+	} else {
+		/*
+		 * kthread helpers are used to submit writes so that
+		 * checksumming can happen in parallel across all CPUs
+		 */
+		ret = btrfs_wq_submit_bio(fs_info, bio, mirror_num, 0,
+					  bio_offset, private_data,
+					  btree_submit_bio_start);
+	}
+
+	if (ret)
+		goto out_w_error;
+	return 0;
+
+out_w_error:
+	bio->bi_status = ret;
+	bio_endio(bio);
+	return ret;
+}
+
+#ifdef CONFIG_MIGRATION
+static int btree_migratepage(struct address_space *mapping,
+			struct page *newpage, struct page *page,
+			enum migrate_mode mode)
+{
+	/*
+	 * we can't safely write a btree page from here,
+	 * we haven't done the locking hook
+	 */
+	if (PageDirty(page))
+		return -EAGAIN;
+	/*
+	 * Buffers may be managed in a filesystem specific way.
+	 * We must have no buffers or drop them.
+	 */
+	if (page_has_private(page) &&
+	    !try_to_release_page(page, GFP_KERNEL))
+		return -EAGAIN;
+	return migrate_page(mapping, newpage, page, mode);
+}
+#endif
+
+
+static int btree_writepages(struct address_space *mapping,
+			    struct writeback_control *wbc)
+{
+	struct btrfs_fs_info *fs_info;
+	int ret;
+
+	if (wbc->sync_mode == WB_SYNC_NONE) {
+
+		if (wbc->for_kupdate)
+			return 0;
+
+		fs_info = BTRFS_I(mapping->host)->root->fs_info;
+		/* this is a bit racy, but that's ok */
+		ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+					     BTRFS_DIRTY_METADATA_THRESH,
+					     fs_info->dirty_metadata_batch);
+		if (ret < 0)
+			return 0;
+	}
+	return btree_write_cache_pages(mapping, wbc);
+}
+
+static int btree_readpage(struct file *file, struct page *page)
+{
+	struct extent_io_tree *tree;
+	tree = &BTRFS_I(page->mapping->host)->io_tree;
+	return extent_read_full_page(tree, page, btree_get_extent, 0);
+}
+
+static int btree_releasepage(struct page *page, gfp_t gfp_flags)
+{
+	if (PageWriteback(page) || PageDirty(page))
+		return 0;
+
+	return try_release_extent_buffer(page);
+}
+
+static void btree_invalidatepage(struct page *page, unsigned int offset,
+				 unsigned int length)
+{
+	struct extent_io_tree *tree;
+	tree = &BTRFS_I(page->mapping->host)->io_tree;
+	extent_invalidatepage(tree, page, offset);
+	btree_releasepage(page, GFP_NOFS);
+	if (PagePrivate(page)) {
+		btrfs_warn(BTRFS_I(page->mapping->host)->root->fs_info,
+			   "page private not zero on page %llu",
+			   (unsigned long long)page_offset(page));
+		ClearPagePrivate(page);
+		set_page_private(page, 0);
+		put_page(page);
+	}
+}
+
+static int btree_set_page_dirty(struct page *page)
+{
+#ifdef DEBUG
+	struct extent_buffer *eb;
+
+	BUG_ON(!PagePrivate(page));
+	eb = (struct extent_buffer *)page->private;
+	BUG_ON(!eb);
+	BUG_ON(!test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags));
+	BUG_ON(!atomic_read(&eb->refs));
+	btrfs_assert_tree_locked(eb);
+#endif
+	return __set_page_dirty_nobuffers(page);
+}
+
+static const struct address_space_operations btree_aops = {
+	.readpage	= btree_readpage,
+	.writepages	= btree_writepages,
+	.releasepage	= btree_releasepage,
+	.invalidatepage = btree_invalidatepage,
+#ifdef CONFIG_MIGRATION
+	.migratepage	= btree_migratepage,
+#endif
+	.set_page_dirty = btree_set_page_dirty,
+};
+
+void readahead_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr)
+{
+	struct extent_buffer *buf = NULL;
+	struct inode *btree_inode = fs_info->btree_inode;
+
+	buf = btrfs_find_create_tree_block(fs_info, bytenr);
+	if (IS_ERR(buf))
+		return;
+	read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
+				 buf, WAIT_NONE, 0);
+	free_extent_buffer(buf);
+}
+
+int reada_tree_block_flagged(struct btrfs_fs_info *fs_info, u64 bytenr,
+			 int mirror_num, struct extent_buffer **eb)
+{
+	struct extent_buffer *buf = NULL;
+	struct inode *btree_inode = fs_info->btree_inode;
+	struct extent_io_tree *io_tree = &BTRFS_I(btree_inode)->io_tree;
+	int ret;
+
+	buf = btrfs_find_create_tree_block(fs_info, bytenr);
+	if (IS_ERR(buf))
+		return 0;
+
+	set_bit(EXTENT_BUFFER_READAHEAD, &buf->bflags);
+
+	ret = read_extent_buffer_pages(io_tree, buf, WAIT_PAGE_LOCK,
+				       mirror_num);
+	if (ret) {
+		free_extent_buffer(buf);
+		return ret;
+	}
+
+	if (test_bit(EXTENT_BUFFER_CORRUPT, &buf->bflags)) {
+		free_extent_buffer(buf);
+		return -EIO;
+	} else if (extent_buffer_uptodate(buf)) {
+		*eb = buf;
+	} else {
+		free_extent_buffer(buf);
+	}
+	return 0;
+}
+
+struct extent_buffer *btrfs_find_create_tree_block(
+						struct btrfs_fs_info *fs_info,
+						u64 bytenr)
+{
+	if (btrfs_is_testing(fs_info))
+		return alloc_test_extent_buffer(fs_info, bytenr);
+	return alloc_extent_buffer(fs_info, bytenr);
+}
+
+
+int btrfs_write_tree_block(struct extent_buffer *buf)
+{
+	return filemap_fdatawrite_range(buf->pages[0]->mapping, buf->start,
+					buf->start + buf->len - 1);
+}
+
+void btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
+{
+	filemap_fdatawait_range(buf->pages[0]->mapping,
+			        buf->start, buf->start + buf->len - 1);
+}
+
+/*
+ * Read tree block at logical address @bytenr and do variant basic but critical
+ * verification.
+ *
+ * @parent_transid:	expected transid of this tree block, skip check if 0
+ * @level:		expected level, mandatory check
+ * @first_key:		expected key in slot 0, skip check if NULL
+ */
+struct extent_buffer *read_tree_block(struct btrfs_fs_info *fs_info, u64 bytenr,
+				      u64 parent_transid, int level,
+				      struct btrfs_key *first_key)
+{
+	struct extent_buffer *buf = NULL;
+	int ret;
+
+	buf = btrfs_find_create_tree_block(fs_info, bytenr);
+	if (IS_ERR(buf))
+		return buf;
+
+	ret = btree_read_extent_buffer_pages(fs_info, buf, parent_transid,
+					     level, first_key);
+	if (ret) {
+		free_extent_buffer(buf);
+		return ERR_PTR(ret);
+	}
+	return buf;
+
+}
+
+void clean_tree_block(struct btrfs_fs_info *fs_info,
+		      struct extent_buffer *buf)
+{
+	if (btrfs_header_generation(buf) ==
+	    fs_info->running_transaction->transid) {
+		btrfs_assert_tree_locked(buf);
+
+		if (test_and_clear_bit(EXTENT_BUFFER_DIRTY, &buf->bflags)) {
+			percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
+						 -buf->len,
+						 fs_info->dirty_metadata_batch);
+			/* ugh, clear_extent_buffer_dirty needs to lock the page */
+			btrfs_set_lock_blocking(buf);
+			clear_extent_buffer_dirty(buf);
+		}
+	}
+}
+
+static struct btrfs_subvolume_writers *btrfs_alloc_subvolume_writers(void)
+{
+	struct btrfs_subvolume_writers *writers;
+	int ret;
+
+	writers = kmalloc(sizeof(*writers), GFP_NOFS);
+	if (!writers)
+		return ERR_PTR(-ENOMEM);
+
+	ret = percpu_counter_init(&writers->counter, 0, GFP_NOFS);
+	if (ret < 0) {
+		kfree(writers);
+		return ERR_PTR(ret);
+	}
+
+	init_waitqueue_head(&writers->wait);
+	return writers;
+}
+
+static void
+btrfs_free_subvolume_writers(struct btrfs_subvolume_writers *writers)
+{
+	percpu_counter_destroy(&writers->counter);
+	kfree(writers);
+}
+
+static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
+			 u64 objectid)
+{
+	bool dummy = test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);
+	root->node = NULL;
+	root->commit_root = NULL;
+	root->state = 0;
+	root->orphan_cleanup_state = 0;
+
+	root->objectid = objectid;
+	root->last_trans = 0;
+	root->highest_objectid = 0;
+	root->nr_delalloc_inodes = 0;
+	root->nr_ordered_extents = 0;
+	root->inode_tree = RB_ROOT;
+	INIT_RADIX_TREE(&root->delayed_nodes_tree, GFP_ATOMIC);
+	root->block_rsv = NULL;
+
+	INIT_LIST_HEAD(&root->dirty_list);
+	INIT_LIST_HEAD(&root->root_list);
+	INIT_LIST_HEAD(&root->delalloc_inodes);
+	INIT_LIST_HEAD(&root->delalloc_root);
+	INIT_LIST_HEAD(&root->ordered_extents);
+	INIT_LIST_HEAD(&root->ordered_root);
+	INIT_LIST_HEAD(&root->logged_list[0]);
+	INIT_LIST_HEAD(&root->logged_list[1]);
+	spin_lock_init(&root->inode_lock);
+	spin_lock_init(&root->delalloc_lock);
+	spin_lock_init(&root->ordered_extent_lock);
+	spin_lock_init(&root->accounting_lock);
+	spin_lock_init(&root->log_extents_lock[0]);
+	spin_lock_init(&root->log_extents_lock[1]);
+	spin_lock_init(&root->qgroup_meta_rsv_lock);
+	mutex_init(&root->objectid_mutex);
+	mutex_init(&root->log_mutex);
+	mutex_init(&root->ordered_extent_mutex);
+	mutex_init(&root->delalloc_mutex);
+	init_waitqueue_head(&root->log_writer_wait);
+	init_waitqueue_head(&root->log_commit_wait[0]);
+	init_waitqueue_head(&root->log_commit_wait[1]);
+	INIT_LIST_HEAD(&root->log_ctxs[0]);
+	INIT_LIST_HEAD(&root->log_ctxs[1]);
+	atomic_set(&root->log_commit[0], 0);
+	atomic_set(&root->log_commit[1], 0);
+	atomic_set(&root->log_writers, 0);
+	atomic_set(&root->log_batch, 0);
+	refcount_set(&root->refs, 1);
+	atomic_set(&root->will_be_snapshotted, 0);
+	atomic_set(&root->snapshot_force_cow, 0);
+	root->log_transid = 0;
+	root->log_transid_committed = -1;
+	root->last_log_commit = 0;
+	if (!dummy)
+		extent_io_tree_init(&root->dirty_log_pages, NULL);
+
+	memset(&root->root_key, 0, sizeof(root->root_key));
+	memset(&root->root_item, 0, sizeof(root->root_item));
+	memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
+	if (!dummy)
+		root->defrag_trans_start = fs_info->generation;
+	else
+		root->defrag_trans_start = 0;
+	root->root_key.objectid = objectid;
+	root->anon_dev = 0;
+
+	spin_lock_init(&root->root_item_lock);
+}
+
+static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info,
+		gfp_t flags)
+{
+	struct btrfs_root *root = kzalloc(sizeof(*root), flags);
+	if (root)
+		root->fs_info = fs_info;
+	return root;
+}
+
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+/* Should only be used by the testing infrastructure */
+struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root;
+
+	if (!fs_info)
+		return ERR_PTR(-EINVAL);
+
+	root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	if (!root)
+		return ERR_PTR(-ENOMEM);
+
+	/* We don't use the stripesize in selftest, set it as sectorsize */
+	__setup_root(root, fs_info, BTRFS_ROOT_TREE_OBJECTID);
+	root->alloc_bytenr = 0;
+
+	return root;
+}
+#endif
+
+struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
+				     struct btrfs_fs_info *fs_info,
+				     u64 objectid)
+{
+	struct extent_buffer *leaf;
+	struct btrfs_root *tree_root = fs_info->tree_root;
+	struct btrfs_root *root;
+	struct btrfs_key key;
+	int ret = 0;
+	uuid_le uuid = NULL_UUID_LE;
+
+	root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	if (!root)
+		return ERR_PTR(-ENOMEM);
+
+	__setup_root(root, fs_info, objectid);
+	root->root_key.objectid = objectid;
+	root->root_key.type = BTRFS_ROOT_ITEM_KEY;
+	root->root_key.offset = 0;
+
+	leaf = btrfs_alloc_tree_block(trans, root, 0, objectid, NULL, 0, 0, 0);
+	if (IS_ERR(leaf)) {
+		ret = PTR_ERR(leaf);
+		leaf = NULL;
+		goto fail;
+	}
+
+	root->node = leaf;
+	btrfs_mark_buffer_dirty(leaf);
+
+	root->commit_root = btrfs_root_node(root);
+	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+
+	root->root_item.flags = 0;
+	root->root_item.byte_limit = 0;
+	btrfs_set_root_bytenr(&root->root_item, leaf->start);
+	btrfs_set_root_generation(&root->root_item, trans->transid);
+	btrfs_set_root_level(&root->root_item, 0);
+	btrfs_set_root_refs(&root->root_item, 1);
+	btrfs_set_root_used(&root->root_item, leaf->len);
+	btrfs_set_root_last_snapshot(&root->root_item, 0);
+	btrfs_set_root_dirid(&root->root_item, 0);
+	if (is_fstree(objectid))
+		uuid_le_gen(&uuid);
+	memcpy(root->root_item.uuid, uuid.b, BTRFS_UUID_SIZE);
+	root->root_item.drop_level = 0;
+
+	key.objectid = objectid;
+	key.type = BTRFS_ROOT_ITEM_KEY;
+	key.offset = 0;
+	ret = btrfs_insert_root(trans, tree_root, &key, &root->root_item);
+	if (ret)
+		goto fail;
+
+	btrfs_tree_unlock(leaf);
+
+	return root;
+
+fail:
+	if (leaf) {
+		btrfs_tree_unlock(leaf);
+		free_extent_buffer(root->commit_root);
+		free_extent_buffer(leaf);
+	}
+	kfree(root);
+
+	return ERR_PTR(ret);
+}
+
+static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
+					 struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root;
+	struct extent_buffer *leaf;
+
+	root = btrfs_alloc_root(fs_info, GFP_NOFS);
+	if (!root)
+		return ERR_PTR(-ENOMEM);
+
+	__setup_root(root, fs_info, BTRFS_TREE_LOG_OBJECTID);
+
+	root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
+	root->root_key.type = BTRFS_ROOT_ITEM_KEY;
+	root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;
+
+	/*
+	 * DON'T set REF_COWS for log trees
+	 *
+	 * log trees do not get reference counted because they go away
+	 * before a real commit is actually done.  They do store pointers
+	 * to file data extents, and those reference counts still get
+	 * updated (along with back refs to the log tree).
+	 */
+
+	leaf = btrfs_alloc_tree_block(trans, root, 0, BTRFS_TREE_LOG_OBJECTID,
+			NULL, 0, 0, 0);
+	if (IS_ERR(leaf)) {
+		kfree(root);
+		return ERR_CAST(leaf);
+	}
+
+	root->node = leaf;
+
+	btrfs_mark_buffer_dirty(root->node);
+	btrfs_tree_unlock(root->node);
+	return root;
+}
+
+int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
+			     struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *log_root;
+
+	log_root = alloc_log_tree(trans, fs_info);
+	if (IS_ERR(log_root))
+		return PTR_ERR(log_root);
+	WARN_ON(fs_info->log_root_tree);
+	fs_info->log_root_tree = log_root;
+	return 0;
+}
+
+int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_root *log_root;
+	struct btrfs_inode_item *inode_item;
+
+	log_root = alloc_log_tree(trans, fs_info);
+	if (IS_ERR(log_root))
+		return PTR_ERR(log_root);
+
+	log_root->last_trans = trans->transid;
+	log_root->root_key.offset = root->root_key.objectid;
+
+	inode_item = &log_root->root_item.inode;
+	btrfs_set_stack_inode_generation(inode_item, 1);
+	btrfs_set_stack_inode_size(inode_item, 3);
+	btrfs_set_stack_inode_nlink(inode_item, 1);
+	btrfs_set_stack_inode_nbytes(inode_item,
+				     fs_info->nodesize);
+	btrfs_set_stack_inode_mode(inode_item, S_IFDIR | 0755);
+
+	btrfs_set_root_node(&log_root->root_item, log_root->node);
+
+	WARN_ON(root->log_root);
+	root->log_root = log_root;
+	root->log_transid = 0;
+	root->log_transid_committed = -1;
+	root->last_log_commit = 0;
+	return 0;
+}
+
+static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
+					       struct btrfs_key *key)
+{
+	struct btrfs_root *root;
+	struct btrfs_fs_info *fs_info = tree_root->fs_info;
+	struct btrfs_path *path;
+	u64 generation;
+	int ret;
+	int level;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	root = btrfs_alloc_root(fs_info, GFP_NOFS);
+	if (!root) {
+		ret = -ENOMEM;
+		goto alloc_fail;
+	}
+
+	__setup_root(root, fs_info, key->objectid);
+
+	ret = btrfs_find_root(tree_root, key, path,
+			      &root->root_item, &root->root_key);
+	if (ret) {
+		if (ret > 0)
+			ret = -ENOENT;
+		goto find_fail;
+	}
+
+	generation = btrfs_root_generation(&root->root_item);
+	level = btrfs_root_level(&root->root_item);
+	root->node = read_tree_block(fs_info,
+				     btrfs_root_bytenr(&root->root_item),
+				     generation, level, NULL);
+	if (IS_ERR(root->node)) {
+		ret = PTR_ERR(root->node);
+		goto find_fail;
+	} else if (!btrfs_buffer_uptodate(root->node, generation, 0)) {
+		ret = -EIO;
+		free_extent_buffer(root->node);
+		goto find_fail;
+	}
+	root->commit_root = btrfs_root_node(root);
+out:
+	btrfs_free_path(path);
+	return root;
+
+find_fail:
+	kfree(root);
+alloc_fail:
+	root = ERR_PTR(ret);
+	goto out;
+}
+
+struct btrfs_root *btrfs_read_fs_root(struct btrfs_root *tree_root,
+				      struct btrfs_key *location)
+{
+	struct btrfs_root *root;
+
+	root = btrfs_read_tree_root(tree_root, location);
+	if (IS_ERR(root))
+		return root;
+
+	if (root->root_key.objectid != BTRFS_TREE_LOG_OBJECTID) {
+		set_bit(BTRFS_ROOT_REF_COWS, &root->state);
+		btrfs_check_and_init_root_item(&root->root_item);
+	}
+
+	return root;
+}
+
+int btrfs_init_fs_root(struct btrfs_root *root)
+{
+	int ret;
+	struct btrfs_subvolume_writers *writers;
+
+	root->free_ino_ctl = kzalloc(sizeof(*root->free_ino_ctl), GFP_NOFS);
+	root->free_ino_pinned = kzalloc(sizeof(*root->free_ino_pinned),
+					GFP_NOFS);
+	if (!root->free_ino_pinned || !root->free_ino_ctl) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+
+	writers = btrfs_alloc_subvolume_writers();
+	if (IS_ERR(writers)) {
+		ret = PTR_ERR(writers);
+		goto fail;
+	}
+	root->subv_writers = writers;
+
+	btrfs_init_free_ino_ctl(root);
+	spin_lock_init(&root->ino_cache_lock);
+	init_waitqueue_head(&root->ino_cache_wait);
+
+	ret = get_anon_bdev(&root->anon_dev);
+	if (ret)
+		goto fail;
+
+	mutex_lock(&root->objectid_mutex);
+	ret = btrfs_find_highest_objectid(root,
+					&root->highest_objectid);
+	if (ret) {
+		mutex_unlock(&root->objectid_mutex);
+		goto fail;
+	}
+
+	ASSERT(root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
+
+	mutex_unlock(&root->objectid_mutex);
+
+	return 0;
+fail:
+	/* The caller is responsible to call btrfs_free_fs_root */
+	return ret;
+}
+
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+					u64 root_id)
+{
+	struct btrfs_root *root;
+
+	spin_lock(&fs_info->fs_roots_radix_lock);
+	root = radix_tree_lookup(&fs_info->fs_roots_radix,
+				 (unsigned long)root_id);
+	spin_unlock(&fs_info->fs_roots_radix_lock);
+	return root;
+}
+
+int btrfs_insert_fs_root(struct btrfs_fs_info *fs_info,
+			 struct btrfs_root *root)
+{
+	int ret;
+
+	ret = radix_tree_preload(GFP_NOFS);
+	if (ret)
+		return ret;
+
+	spin_lock(&fs_info->fs_roots_radix_lock);
+	ret = radix_tree_insert(&fs_info->fs_roots_radix,
+				(unsigned long)root->root_key.objectid,
+				root);
+	if (ret == 0)
+		set_bit(BTRFS_ROOT_IN_RADIX, &root->state);
+	spin_unlock(&fs_info->fs_roots_radix_lock);
+	radix_tree_preload_end();
+
+	return ret;
+}
+
+struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
+				     struct btrfs_key *location,
+				     bool check_ref)
+{
+	struct btrfs_root *root;
+	struct btrfs_path *path;
+	struct btrfs_key key;
+	int ret;
+
+	if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
+		return fs_info->tree_root;
+	if (location->objectid == BTRFS_EXTENT_TREE_OBJECTID)
+		return fs_info->extent_root;
+	if (location->objectid == BTRFS_CHUNK_TREE_OBJECTID)
+		return fs_info->chunk_root;
+	if (location->objectid == BTRFS_DEV_TREE_OBJECTID)
+		return fs_info->dev_root;
+	if (location->objectid == BTRFS_CSUM_TREE_OBJECTID)
+		return fs_info->csum_root;
+	if (location->objectid == BTRFS_QUOTA_TREE_OBJECTID)
+		return fs_info->quota_root ? fs_info->quota_root :
+					     ERR_PTR(-ENOENT);
+	if (location->objectid == BTRFS_UUID_TREE_OBJECTID)
+		return fs_info->uuid_root ? fs_info->uuid_root :
+					    ERR_PTR(-ENOENT);
+	if (location->objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
+		return fs_info->free_space_root ? fs_info->free_space_root :
+						  ERR_PTR(-ENOENT);
+again:
+	root = btrfs_lookup_fs_root(fs_info, location->objectid);
+	if (root) {
+		if (check_ref && btrfs_root_refs(&root->root_item) == 0)
+			return ERR_PTR(-ENOENT);
+		return root;
+	}
+
+	root = btrfs_read_fs_root(fs_info->tree_root, location);
+	if (IS_ERR(root))
+		return root;
+
+	if (check_ref && btrfs_root_refs(&root->root_item) == 0) {
+		ret = -ENOENT;
+		goto fail;
+	}
+
+	ret = btrfs_init_fs_root(root);
+	if (ret)
+		goto fail;
+
+	path = btrfs_alloc_path();
+	if (!path) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+	key.objectid = BTRFS_ORPHAN_OBJECTID;
+	key.type = BTRFS_ORPHAN_ITEM_KEY;
+	key.offset = location->objectid;
+
+	ret = btrfs_search_slot(NULL, fs_info->tree_root, &key, path, 0, 0);
+	btrfs_free_path(path);
+	if (ret < 0)
+		goto fail;
+	if (ret == 0)
+		set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
+
+	ret = btrfs_insert_fs_root(fs_info, root);
+	if (ret) {
+		if (ret == -EEXIST) {
+			btrfs_free_fs_root(root);
+			goto again;
+		}
+		goto fail;
+	}
+	return root;
+fail:
+	btrfs_free_fs_root(root);
+	return ERR_PTR(ret);
+}
+
+static int btrfs_congested_fn(void *congested_data, int bdi_bits)
+{
+	struct btrfs_fs_info *info = (struct btrfs_fs_info *)congested_data;
+	int ret = 0;
+	struct btrfs_device *device;
+	struct backing_dev_info *bdi;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(device, &info->fs_devices->devices, dev_list) {
+		if (!device->bdev)
+			continue;
+		bdi = device->bdev->bd_bdi;
+		if (bdi_congested(bdi, bdi_bits)) {
+			ret = 1;
+			break;
+		}
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
+/*
+ * called by the kthread helper functions to finally call the bio end_io
+ * functions.  This is where read checksum verification actually happens
+ */
+static void end_workqueue_fn(struct btrfs_work *work)
+{
+	struct bio *bio;
+	struct btrfs_end_io_wq *end_io_wq;
+
+	end_io_wq = container_of(work, struct btrfs_end_io_wq, work);
+	bio = end_io_wq->bio;
+
+	bio->bi_status = end_io_wq->status;
+	bio->bi_private = end_io_wq->private;
+	bio->bi_end_io = end_io_wq->end_io;
+	kmem_cache_free(btrfs_end_io_wq_cache, end_io_wq);
+	bio_endio(bio);
+}
+
+static int cleaner_kthread(void *arg)
+{
+	struct btrfs_root *root = arg;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	int again;
+
+	while (1) {
+		again = 0;
+
+		/* Make the cleaner go to sleep early. */
+		if (btrfs_need_cleaner_sleep(fs_info))
+			goto sleep;
+
+		/*
+		 * Do not do anything if we might cause open_ctree() to block
+		 * before we have finished mounting the filesystem.
+		 */
+		if (!test_bit(BTRFS_FS_OPEN, &fs_info->flags))
+			goto sleep;
+
+		if (!mutex_trylock(&fs_info->cleaner_mutex))
+			goto sleep;
+
+		/*
+		 * Avoid the problem that we change the status of the fs
+		 * during the above check and trylock.
+		 */
+		if (btrfs_need_cleaner_sleep(fs_info)) {
+			mutex_unlock(&fs_info->cleaner_mutex);
+			goto sleep;
+		}
+
+		mutex_lock(&fs_info->cleaner_delayed_iput_mutex);
+		btrfs_run_delayed_iputs(fs_info);
+		mutex_unlock(&fs_info->cleaner_delayed_iput_mutex);
+
+		again = btrfs_clean_one_deleted_snapshot(root);
+		mutex_unlock(&fs_info->cleaner_mutex);
+
+		/*
+		 * The defragger has dealt with the R/O remount and umount,
+		 * needn't do anything special here.
+		 */
+		btrfs_run_defrag_inodes(fs_info);
+
+		/*
+		 * Acquires fs_info->delete_unused_bgs_mutex to avoid racing
+		 * with relocation (btrfs_relocate_chunk) and relocation
+		 * acquires fs_info->cleaner_mutex (btrfs_relocate_block_group)
+		 * after acquiring fs_info->delete_unused_bgs_mutex. So we
+		 * can't hold, nor need to, fs_info->cleaner_mutex when deleting
+		 * unused block groups.
+		 */
+		btrfs_delete_unused_bgs(fs_info);
+sleep:
+		if (kthread_should_park())
+			kthread_parkme();
+		if (kthread_should_stop())
+			return 0;
+		if (!again) {
+			set_current_state(TASK_INTERRUPTIBLE);
+			schedule();
+			__set_current_state(TASK_RUNNING);
+		}
+	}
+}
+
+static int transaction_kthread(void *arg)
+{
+	struct btrfs_root *root = arg;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_transaction *cur;
+	u64 transid;
+	time64_t now;
+	unsigned long delay;
+	bool cannot_commit;
+
+	do {
+		cannot_commit = false;
+		delay = HZ * fs_info->commit_interval;
+		mutex_lock(&fs_info->transaction_kthread_mutex);
+
+		spin_lock(&fs_info->trans_lock);
+		cur = fs_info->running_transaction;
+		if (!cur) {
+			spin_unlock(&fs_info->trans_lock);
+			goto sleep;
+		}
+
+		now = ktime_get_seconds();
+		if (cur->state < TRANS_STATE_BLOCKED &&
+		    !test_bit(BTRFS_FS_NEED_ASYNC_COMMIT, &fs_info->flags) &&
+		    (now < cur->start_time ||
+		     now - cur->start_time < fs_info->commit_interval)) {
+			spin_unlock(&fs_info->trans_lock);
+			delay = HZ * 5;
+			goto sleep;
+		}
+		transid = cur->transid;
+		spin_unlock(&fs_info->trans_lock);
+
+		/* If the file system is aborted, this will always fail. */
+		trans = btrfs_attach_transaction(root);
+		if (IS_ERR(trans)) {
+			if (PTR_ERR(trans) != -ENOENT)
+				cannot_commit = true;
+			goto sleep;
+		}
+		if (transid == trans->transid) {
+			btrfs_commit_transaction(trans);
+		} else {
+			btrfs_end_transaction(trans);
+		}
+sleep:
+		wake_up_process(fs_info->cleaner_kthread);
+		mutex_unlock(&fs_info->transaction_kthread_mutex);
+
+		if (unlikely(test_bit(BTRFS_FS_STATE_ERROR,
+				      &fs_info->fs_state)))
+			btrfs_cleanup_transaction(fs_info);
+		if (!kthread_should_stop() &&
+				(!btrfs_transaction_blocked(fs_info) ||
+				 cannot_commit))
+			schedule_timeout_interruptible(delay);
+	} while (!kthread_should_stop());
+	return 0;
+}
+
+/*
+ * this will find the highest generation in the array of
+ * root backups.  The index of the highest array is returned,
+ * or -1 if we can't find anything.
+ *
+ * We check to make sure the array is valid by comparing the
+ * generation of the latest  root in the array with the generation
+ * in the super block.  If they don't match we pitch it.
+ */
+static int find_newest_super_backup(struct btrfs_fs_info *info, u64 newest_gen)
+{
+	u64 cur;
+	int newest_index = -1;
+	struct btrfs_root_backup *root_backup;
+	int i;
+
+	for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; i++) {
+		root_backup = info->super_copy->super_roots + i;
+		cur = btrfs_backup_tree_root_gen(root_backup);
+		if (cur == newest_gen)
+			newest_index = i;
+	}
+
+	/* check to see if we actually wrapped around */
+	if (newest_index == BTRFS_NUM_BACKUP_ROOTS - 1) {
+		root_backup = info->super_copy->super_roots;
+		cur = btrfs_backup_tree_root_gen(root_backup);
+		if (cur == newest_gen)
+			newest_index = 0;
+	}
+	return newest_index;
+}
+
+
+/*
+ * find the oldest backup so we know where to store new entries
+ * in the backup array.  This will set the backup_root_index
+ * field in the fs_info struct
+ */
+static void find_oldest_super_backup(struct btrfs_fs_info *info,
+				     u64 newest_gen)
+{
+	int newest_index = -1;
+
+	newest_index = find_newest_super_backup(info, newest_gen);
+	/* if there was garbage in there, just move along */
+	if (newest_index == -1) {
+		info->backup_root_index = 0;
+	} else {
+		info->backup_root_index = (newest_index + 1) % BTRFS_NUM_BACKUP_ROOTS;
+	}
+}
+
+/*
+ * copy all the root pointers into the super backup array.
+ * this will bump the backup pointer by one when it is
+ * done
+ */
+static void backup_super_roots(struct btrfs_fs_info *info)
+{
+	int next_backup;
+	struct btrfs_root_backup *root_backup;
+	int last_backup;
+
+	next_backup = info->backup_root_index;
+	last_backup = (next_backup + BTRFS_NUM_BACKUP_ROOTS - 1) %
+		BTRFS_NUM_BACKUP_ROOTS;
+
+	/*
+	 * just overwrite the last backup if we're at the same generation
+	 * this happens only at umount
+	 */
+	root_backup = info->super_for_commit->super_roots + last_backup;
+	if (btrfs_backup_tree_root_gen(root_backup) ==
+	    btrfs_header_generation(info->tree_root->node))
+		next_backup = last_backup;
+
+	root_backup = info->super_for_commit->super_roots + next_backup;
+
+	/*
+	 * make sure all of our padding and empty slots get zero filled
+	 * regardless of which ones we use today
+	 */
+	memset(root_backup, 0, sizeof(*root_backup));
+
+	info->backup_root_index = (next_backup + 1) % BTRFS_NUM_BACKUP_ROOTS;
+
+	btrfs_set_backup_tree_root(root_backup, info->tree_root->node->start);
+	btrfs_set_backup_tree_root_gen(root_backup,
+			       btrfs_header_generation(info->tree_root->node));
+
+	btrfs_set_backup_tree_root_level(root_backup,
+			       btrfs_header_level(info->tree_root->node));
+
+	btrfs_set_backup_chunk_root(root_backup, info->chunk_root->node->start);
+	btrfs_set_backup_chunk_root_gen(root_backup,
+			       btrfs_header_generation(info->chunk_root->node));
+	btrfs_set_backup_chunk_root_level(root_backup,
+			       btrfs_header_level(info->chunk_root->node));
+
+	btrfs_set_backup_extent_root(root_backup, info->extent_root->node->start);
+	btrfs_set_backup_extent_root_gen(root_backup,
+			       btrfs_header_generation(info->extent_root->node));
+	btrfs_set_backup_extent_root_level(root_backup,
+			       btrfs_header_level(info->extent_root->node));
+
+	/*
+	 * we might commit during log recovery, which happens before we set
+	 * the fs_root.  Make sure it is valid before we fill it in.
+	 */
+	if (info->fs_root && info->fs_root->node) {
+		btrfs_set_backup_fs_root(root_backup,
+					 info->fs_root->node->start);
+		btrfs_set_backup_fs_root_gen(root_backup,
+			       btrfs_header_generation(info->fs_root->node));
+		btrfs_set_backup_fs_root_level(root_backup,
+			       btrfs_header_level(info->fs_root->node));
+	}
+
+	btrfs_set_backup_dev_root(root_backup, info->dev_root->node->start);
+	btrfs_set_backup_dev_root_gen(root_backup,
+			       btrfs_header_generation(info->dev_root->node));
+	btrfs_set_backup_dev_root_level(root_backup,
+				       btrfs_header_level(info->dev_root->node));
+
+	btrfs_set_backup_csum_root(root_backup, info->csum_root->node->start);
+	btrfs_set_backup_csum_root_gen(root_backup,
+			       btrfs_header_generation(info->csum_root->node));
+	btrfs_set_backup_csum_root_level(root_backup,
+			       btrfs_header_level(info->csum_root->node));
+
+	btrfs_set_backup_total_bytes(root_backup,
+			     btrfs_super_total_bytes(info->super_copy));
+	btrfs_set_backup_bytes_used(root_backup,
+			     btrfs_super_bytes_used(info->super_copy));
+	btrfs_set_backup_num_devices(root_backup,
+			     btrfs_super_num_devices(info->super_copy));
+
+	/*
+	 * if we don't copy this out to the super_copy, it won't get remembered
+	 * for the next commit
+	 */
+	memcpy(&info->super_copy->super_roots,
+	       &info->super_for_commit->super_roots,
+	       sizeof(*root_backup) * BTRFS_NUM_BACKUP_ROOTS);
+}
+
+/*
+ * this copies info out of the root backup array and back into
+ * the in-memory super block.  It is meant to help iterate through
+ * the array, so you send it the number of backups you've already
+ * tried and the last backup index you used.
+ *
+ * this returns -1 when it has tried all the backups
+ */
+static noinline int next_root_backup(struct btrfs_fs_info *info,
+				     struct btrfs_super_block *super,
+				     int *num_backups_tried, int *backup_index)
+{
+	struct btrfs_root_backup *root_backup;
+	int newest = *backup_index;
+
+	if (*num_backups_tried == 0) {
+		u64 gen = btrfs_super_generation(super);
+
+		newest = find_newest_super_backup(info, gen);
+		if (newest == -1)
+			return -1;
+
+		*backup_index = newest;
+		*num_backups_tried = 1;
+	} else if (*num_backups_tried == BTRFS_NUM_BACKUP_ROOTS) {
+		/* we've tried all the backups, all done */
+		return -1;
+	} else {
+		/* jump to the next oldest backup */
+		newest = (*backup_index + BTRFS_NUM_BACKUP_ROOTS - 1) %
+			BTRFS_NUM_BACKUP_ROOTS;
+		*backup_index = newest;
+		*num_backups_tried += 1;
+	}
+	root_backup = super->super_roots + newest;
+
+	btrfs_set_super_generation(super,
+				   btrfs_backup_tree_root_gen(root_backup));
+	btrfs_set_super_root(super, btrfs_backup_tree_root(root_backup));
+	btrfs_set_super_root_level(super,
+				   btrfs_backup_tree_root_level(root_backup));
+	btrfs_set_super_bytes_used(super, btrfs_backup_bytes_used(root_backup));
+
+	/*
+	 * fixme: the total bytes and num_devices need to match or we should
+	 * need a fsck
+	 */
+	btrfs_set_super_total_bytes(super, btrfs_backup_total_bytes(root_backup));
+	btrfs_set_super_num_devices(super, btrfs_backup_num_devices(root_backup));
+	return 0;
+}
+
+/* helper to cleanup workers */
+static void btrfs_stop_all_workers(struct btrfs_fs_info *fs_info)
+{
+	btrfs_destroy_workqueue(fs_info->fixup_workers);
+	btrfs_destroy_workqueue(fs_info->delalloc_workers);
+	btrfs_destroy_workqueue(fs_info->workers);
+	btrfs_destroy_workqueue(fs_info->endio_workers);
+	btrfs_destroy_workqueue(fs_info->endio_raid56_workers);
+	btrfs_destroy_workqueue(fs_info->endio_repair_workers);
+	btrfs_destroy_workqueue(fs_info->rmw_workers);
+	btrfs_destroy_workqueue(fs_info->endio_write_workers);
+	btrfs_destroy_workqueue(fs_info->endio_freespace_worker);
+	btrfs_destroy_workqueue(fs_info->submit_workers);
+	btrfs_destroy_workqueue(fs_info->delayed_workers);
+	btrfs_destroy_workqueue(fs_info->caching_workers);
+	btrfs_destroy_workqueue(fs_info->readahead_workers);
+	btrfs_destroy_workqueue(fs_info->flush_workers);
+	btrfs_destroy_workqueue(fs_info->qgroup_rescan_workers);
+	btrfs_destroy_workqueue(fs_info->extent_workers);
+	/*
+	 * Now that all other work queues are destroyed, we can safely destroy
+	 * the queues used for metadata I/O, since tasks from those other work
+	 * queues can do metadata I/O operations.
+	 */
+	btrfs_destroy_workqueue(fs_info->endio_meta_workers);
+	btrfs_destroy_workqueue(fs_info->endio_meta_write_workers);
+}
+
+static void free_root_extent_buffers(struct btrfs_root *root)
+{
+	if (root) {
+		free_extent_buffer(root->node);
+		free_extent_buffer(root->commit_root);
+		root->node = NULL;
+		root->commit_root = NULL;
+	}
+}
+
+/* helper to cleanup tree roots */
+static void free_root_pointers(struct btrfs_fs_info *info, int chunk_root)
+{
+	free_root_extent_buffers(info->tree_root);
+
+	free_root_extent_buffers(info->dev_root);
+	free_root_extent_buffers(info->extent_root);
+	free_root_extent_buffers(info->csum_root);
+	free_root_extent_buffers(info->quota_root);
+	free_root_extent_buffers(info->uuid_root);
+	if (chunk_root)
+		free_root_extent_buffers(info->chunk_root);
+	free_root_extent_buffers(info->free_space_root);
+}
+
+void btrfs_free_fs_roots(struct btrfs_fs_info *fs_info)
+{
+	int ret;
+	struct btrfs_root *gang[8];
+	int i;
+
+	while (!list_empty(&fs_info->dead_roots)) {
+		gang[0] = list_entry(fs_info->dead_roots.next,
+				     struct btrfs_root, root_list);
+		list_del(&gang[0]->root_list);
+
+		if (test_bit(BTRFS_ROOT_IN_RADIX, &gang[0]->state)) {
+			btrfs_drop_and_free_fs_root(fs_info, gang[0]);
+		} else {
+			free_extent_buffer(gang[0]->node);
+			free_extent_buffer(gang[0]->commit_root);
+			btrfs_put_fs_root(gang[0]);
+		}
+	}
+
+	while (1) {
+		ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
+					     (void **)gang, 0,
+					     ARRAY_SIZE(gang));
+		if (!ret)
+			break;
+		for (i = 0; i < ret; i++)
+			btrfs_drop_and_free_fs_root(fs_info, gang[i]);
+	}
+
+	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
+		btrfs_free_log_root_tree(NULL, fs_info);
+		btrfs_destroy_pinned_extent(fs_info, fs_info->pinned_extents);
+	}
+}
+
+static void btrfs_init_scrub(struct btrfs_fs_info *fs_info)
+{
+	mutex_init(&fs_info->scrub_lock);
+	atomic_set(&fs_info->scrubs_running, 0);
+	atomic_set(&fs_info->scrub_pause_req, 0);
+	atomic_set(&fs_info->scrubs_paused, 0);
+	atomic_set(&fs_info->scrub_cancel_req, 0);
+	init_waitqueue_head(&fs_info->scrub_pause_wait);
+	fs_info->scrub_workers_refcnt = 0;
+}
+
+static void btrfs_init_balance(struct btrfs_fs_info *fs_info)
+{
+	spin_lock_init(&fs_info->balance_lock);
+	mutex_init(&fs_info->balance_mutex);
+	atomic_set(&fs_info->balance_pause_req, 0);
+	atomic_set(&fs_info->balance_cancel_req, 0);
+	fs_info->balance_ctl = NULL;
+	init_waitqueue_head(&fs_info->balance_wait_q);
+}
+
+static void btrfs_init_btree_inode(struct btrfs_fs_info *fs_info)
+{
+	struct inode *inode = fs_info->btree_inode;
+
+	inode->i_ino = BTRFS_BTREE_INODE_OBJECTID;
+	set_nlink(inode, 1);
+	/*
+	 * we set the i_size on the btree inode to the max possible int.
+	 * the real end of the address space is determined by all of
+	 * the devices in the system
+	 */
+	inode->i_size = OFFSET_MAX;
+	inode->i_mapping->a_ops = &btree_aops;
+
+	RB_CLEAR_NODE(&BTRFS_I(inode)->rb_node);
+	extent_io_tree_init(&BTRFS_I(inode)->io_tree, inode);
+	BTRFS_I(inode)->io_tree.track_uptodate = 0;
+	extent_map_tree_init(&BTRFS_I(inode)->extent_tree);
+
+	BTRFS_I(inode)->io_tree.ops = &btree_extent_io_ops;
+
+	BTRFS_I(inode)->root = fs_info->tree_root;
+	memset(&BTRFS_I(inode)->location, 0, sizeof(struct btrfs_key));
+	set_bit(BTRFS_INODE_DUMMY, &BTRFS_I(inode)->runtime_flags);
+	btrfs_insert_inode_hash(inode);
+}
+
+static void btrfs_init_dev_replace_locks(struct btrfs_fs_info *fs_info)
+{
+	mutex_init(&fs_info->dev_replace.lock_finishing_cancel_unmount);
+	rwlock_init(&fs_info->dev_replace.lock);
+	atomic_set(&fs_info->dev_replace.read_locks, 0);
+	atomic_set(&fs_info->dev_replace.blocking_readers, 0);
+	init_waitqueue_head(&fs_info->replace_wait);
+	init_waitqueue_head(&fs_info->dev_replace.read_lock_wq);
+}
+
+static void btrfs_init_qgroup(struct btrfs_fs_info *fs_info)
+{
+	spin_lock_init(&fs_info->qgroup_lock);
+	mutex_init(&fs_info->qgroup_ioctl_lock);
+	fs_info->qgroup_tree = RB_ROOT;
+	fs_info->qgroup_op_tree = RB_ROOT;
+	INIT_LIST_HEAD(&fs_info->dirty_qgroups);
+	fs_info->qgroup_seq = 1;
+	fs_info->qgroup_ulist = NULL;
+	fs_info->qgroup_rescan_running = false;
+	mutex_init(&fs_info->qgroup_rescan_lock);
+}
+
+static int btrfs_init_workqueues(struct btrfs_fs_info *fs_info,
+		struct btrfs_fs_devices *fs_devices)
+{
+	u32 max_active = fs_info->thread_pool_size;
+	unsigned int flags = WQ_MEM_RECLAIM | WQ_FREEZABLE | WQ_UNBOUND;
+
+	fs_info->workers =
+		btrfs_alloc_workqueue(fs_info, "worker",
+				      flags | WQ_HIGHPRI, max_active, 16);
+
+	fs_info->delalloc_workers =
+		btrfs_alloc_workqueue(fs_info, "delalloc",
+				      flags, max_active, 2);
+
+	fs_info->flush_workers =
+		btrfs_alloc_workqueue(fs_info, "flush_delalloc",
+				      flags, max_active, 0);
+
+	fs_info->caching_workers =
+		btrfs_alloc_workqueue(fs_info, "cache", flags, max_active, 0);
+
+	/*
+	 * a higher idle thresh on the submit workers makes it much more
+	 * likely that bios will be send down in a sane order to the
+	 * devices
+	 */
+	fs_info->submit_workers =
+		btrfs_alloc_workqueue(fs_info, "submit", flags,
+				      min_t(u64, fs_devices->num_devices,
+					    max_active), 64);
+
+	fs_info->fixup_workers =
+		btrfs_alloc_workqueue(fs_info, "fixup", flags, 1, 0);
+
+	/*
+	 * endios are largely parallel and should have a very
+	 * low idle thresh
+	 */
+	fs_info->endio_workers =
+		btrfs_alloc_workqueue(fs_info, "endio", flags, max_active, 4);
+	fs_info->endio_meta_workers =
+		btrfs_alloc_workqueue(fs_info, "endio-meta", flags,
+				      max_active, 4);
+	fs_info->endio_meta_write_workers =
+		btrfs_alloc_workqueue(fs_info, "endio-meta-write", flags,
+				      max_active, 2);
+	fs_info->endio_raid56_workers =
+		btrfs_alloc_workqueue(fs_info, "endio-raid56", flags,
+				      max_active, 4);
+	fs_info->endio_repair_workers =
+		btrfs_alloc_workqueue(fs_info, "endio-repair", flags, 1, 0);
+	fs_info->rmw_workers =
+		btrfs_alloc_workqueue(fs_info, "rmw", flags, max_active, 2);
+	fs_info->endio_write_workers =
+		btrfs_alloc_workqueue(fs_info, "endio-write", flags,
+				      max_active, 2);
+	fs_info->endio_freespace_worker =
+		btrfs_alloc_workqueue(fs_info, "freespace-write", flags,
+				      max_active, 0);
+	fs_info->delayed_workers =
+		btrfs_alloc_workqueue(fs_info, "delayed-meta", flags,
+				      max_active, 0);
+	fs_info->readahead_workers =
+		btrfs_alloc_workqueue(fs_info, "readahead", flags,
+				      max_active, 2);
+	fs_info->qgroup_rescan_workers =
+		btrfs_alloc_workqueue(fs_info, "qgroup-rescan", flags, 1, 0);
+	fs_info->extent_workers =
+		btrfs_alloc_workqueue(fs_info, "extent-refs", flags,
+				      min_t(u64, fs_devices->num_devices,
+					    max_active), 8);
+
+	if (!(fs_info->workers && fs_info->delalloc_workers &&
+	      fs_info->submit_workers && fs_info->flush_workers &&
+	      fs_info->endio_workers && fs_info->endio_meta_workers &&
+	      fs_info->endio_meta_write_workers &&
+	      fs_info->endio_repair_workers &&
+	      fs_info->endio_write_workers && fs_info->endio_raid56_workers &&
+	      fs_info->endio_freespace_worker && fs_info->rmw_workers &&
+	      fs_info->caching_workers && fs_info->readahead_workers &&
+	      fs_info->fixup_workers && fs_info->delayed_workers &&
+	      fs_info->extent_workers &&
+	      fs_info->qgroup_rescan_workers)) {
+		return -ENOMEM;
+	}
+
+	return 0;
+}
+
+static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
+			    struct btrfs_fs_devices *fs_devices)
+{
+	int ret;
+	struct btrfs_root *log_tree_root;
+	struct btrfs_super_block *disk_super = fs_info->super_copy;
+	u64 bytenr = btrfs_super_log_root(disk_super);
+	int level = btrfs_super_log_root_level(disk_super);
+
+	if (fs_devices->rw_devices == 0) {
+		btrfs_warn(fs_info, "log replay required on RO media");
+		return -EIO;
+	}
+
+	log_tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	if (!log_tree_root)
+		return -ENOMEM;
+
+	__setup_root(log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);
+
+	log_tree_root->node = read_tree_block(fs_info, bytenr,
+					      fs_info->generation + 1,
+					      level, NULL);
+	if (IS_ERR(log_tree_root->node)) {
+		btrfs_warn(fs_info, "failed to read log tree");
+		ret = PTR_ERR(log_tree_root->node);
+		kfree(log_tree_root);
+		return ret;
+	} else if (!extent_buffer_uptodate(log_tree_root->node)) {
+		btrfs_err(fs_info, "failed to read log tree");
+		free_extent_buffer(log_tree_root->node);
+		kfree(log_tree_root);
+		return -EIO;
+	}
+	/* returns with log_tree_root freed on success */
+	ret = btrfs_recover_log_trees(log_tree_root);
+	if (ret) {
+		btrfs_handle_fs_error(fs_info, ret,
+				      "Failed to recover log tree");
+		free_extent_buffer(log_tree_root->node);
+		kfree(log_tree_root);
+		return ret;
+	}
+
+	if (sb_rdonly(fs_info->sb)) {
+		ret = btrfs_commit_super(fs_info);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *tree_root = fs_info->tree_root;
+	struct btrfs_root *root;
+	struct btrfs_key location;
+	int ret;
+
+	BUG_ON(!fs_info->tree_root);
+
+	location.objectid = BTRFS_EXTENT_TREE_OBJECTID;
+	location.type = BTRFS_ROOT_ITEM_KEY;
+	location.offset = 0;
+
+	root = btrfs_read_tree_root(tree_root, &location);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
+	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+	fs_info->extent_root = root;
+
+	location.objectid = BTRFS_DEV_TREE_OBJECTID;
+	root = btrfs_read_tree_root(tree_root, &location);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
+	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+	fs_info->dev_root = root;
+	btrfs_init_devices_late(fs_info);
+
+	location.objectid = BTRFS_CSUM_TREE_OBJECTID;
+	root = btrfs_read_tree_root(tree_root, &location);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		goto out;
+	}
+	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+	fs_info->csum_root = root;
+
+	location.objectid = BTRFS_QUOTA_TREE_OBJECTID;
+	root = btrfs_read_tree_root(tree_root, &location);
+	if (!IS_ERR(root)) {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		set_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags);
+		fs_info->quota_root = root;
+	}
+
+	location.objectid = BTRFS_UUID_TREE_OBJECTID;
+	root = btrfs_read_tree_root(tree_root, &location);
+	if (IS_ERR(root)) {
+		ret = PTR_ERR(root);
+		if (ret != -ENOENT)
+			goto out;
+	} else {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->uuid_root = root;
+	}
+
+	if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
+		location.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID;
+		root = btrfs_read_tree_root(tree_root, &location);
+		if (IS_ERR(root)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->free_space_root = root;
+	}
+
+	return 0;
+out:
+	btrfs_warn(fs_info, "failed to read root (objectid=%llu): %d",
+		   location.objectid, ret);
+	return ret;
+}
+
+/*
+ * Real super block validation
+ * NOTE: super csum type and incompat features will not be checked here.
+ *
+ * @sb:		super block to check
+ * @mirror_num:	the super block number to check its bytenr:
+ * 		0	the primary (1st) sb
+ * 		1, 2	2nd and 3rd backup copy
+ * 	       -1	skip bytenr check
+ */
+static int validate_super(struct btrfs_fs_info *fs_info,
+			    struct btrfs_super_block *sb, int mirror_num)
+{
+	u64 nodesize = btrfs_super_nodesize(sb);
+	u64 sectorsize = btrfs_super_sectorsize(sb);
+	int ret = 0;
+
+	if (btrfs_super_magic(sb) != BTRFS_MAGIC) {
+		btrfs_err(fs_info, "no valid FS found");
+		ret = -EINVAL;
+	}
+	if (btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP) {
+		btrfs_err(fs_info, "unrecognized or unsupported super flag: %llu",
+				btrfs_super_flags(sb) & ~BTRFS_SUPER_FLAG_SUPP);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_root_level(sb) >= BTRFS_MAX_LEVEL) {
+		btrfs_err(fs_info, "tree_root level too big: %d >= %d",
+				btrfs_super_root_level(sb), BTRFS_MAX_LEVEL);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_chunk_root_level(sb) >= BTRFS_MAX_LEVEL) {
+		btrfs_err(fs_info, "chunk_root level too big: %d >= %d",
+				btrfs_super_chunk_root_level(sb), BTRFS_MAX_LEVEL);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_log_root_level(sb) >= BTRFS_MAX_LEVEL) {
+		btrfs_err(fs_info, "log_root level too big: %d >= %d",
+				btrfs_super_log_root_level(sb), BTRFS_MAX_LEVEL);
+		ret = -EINVAL;
+	}
+
+	/*
+	 * Check sectorsize and nodesize first, other check will need it.
+	 * Check all possible sectorsize(4K, 8K, 16K, 32K, 64K) here.
+	 */
+	if (!is_power_of_2(sectorsize) || sectorsize < 4096 ||
+	    sectorsize > BTRFS_MAX_METADATA_BLOCKSIZE) {
+		btrfs_err(fs_info, "invalid sectorsize %llu", sectorsize);
+		ret = -EINVAL;
+	}
+	/* Only PAGE SIZE is supported yet */
+	if (sectorsize != PAGE_SIZE) {
+		btrfs_err(fs_info,
+			"sectorsize %llu not supported yet, only support %lu",
+			sectorsize, PAGE_SIZE);
+		ret = -EINVAL;
+	}
+	if (!is_power_of_2(nodesize) || nodesize < sectorsize ||
+	    nodesize > BTRFS_MAX_METADATA_BLOCKSIZE) {
+		btrfs_err(fs_info, "invalid nodesize %llu", nodesize);
+		ret = -EINVAL;
+	}
+	if (nodesize != le32_to_cpu(sb->__unused_leafsize)) {
+		btrfs_err(fs_info, "invalid leafsize %u, should be %llu",
+			  le32_to_cpu(sb->__unused_leafsize), nodesize);
+		ret = -EINVAL;
+	}
+
+	/* Root alignment check */
+	if (!IS_ALIGNED(btrfs_super_root(sb), sectorsize)) {
+		btrfs_warn(fs_info, "tree_root block unaligned: %llu",
+			   btrfs_super_root(sb));
+		ret = -EINVAL;
+	}
+	if (!IS_ALIGNED(btrfs_super_chunk_root(sb), sectorsize)) {
+		btrfs_warn(fs_info, "chunk_root block unaligned: %llu",
+			   btrfs_super_chunk_root(sb));
+		ret = -EINVAL;
+	}
+	if (!IS_ALIGNED(btrfs_super_log_root(sb), sectorsize)) {
+		btrfs_warn(fs_info, "log_root block unaligned: %llu",
+			   btrfs_super_log_root(sb));
+		ret = -EINVAL;
+	}
+
+	if (memcmp(fs_info->fsid, sb->dev_item.fsid, BTRFS_FSID_SIZE) != 0) {
+		btrfs_err(fs_info,
+			   "dev_item UUID does not match fsid: %pU != %pU",
+			   fs_info->fsid, sb->dev_item.fsid);
+		ret = -EINVAL;
+	}
+
+	/*
+	 * Hint to catch really bogus numbers, bitflips or so, more exact checks are
+	 * done later
+	 */
+	if (btrfs_super_bytes_used(sb) < 6 * btrfs_super_nodesize(sb)) {
+		btrfs_err(fs_info, "bytes_used is too small %llu",
+			  btrfs_super_bytes_used(sb));
+		ret = -EINVAL;
+	}
+	if (!is_power_of_2(btrfs_super_stripesize(sb))) {
+		btrfs_err(fs_info, "invalid stripesize %u",
+			  btrfs_super_stripesize(sb));
+		ret = -EINVAL;
+	}
+	if (btrfs_super_num_devices(sb) > (1UL << 31))
+		btrfs_warn(fs_info, "suspicious number of devices: %llu",
+			   btrfs_super_num_devices(sb));
+	if (btrfs_super_num_devices(sb) == 0) {
+		btrfs_err(fs_info, "number of devices is 0");
+		ret = -EINVAL;
+	}
+
+	if (mirror_num >= 0 &&
+	    btrfs_super_bytenr(sb) != btrfs_sb_offset(mirror_num)) {
+		btrfs_err(fs_info, "super offset mismatch %llu != %u",
+			  btrfs_super_bytenr(sb), BTRFS_SUPER_INFO_OFFSET);
+		ret = -EINVAL;
+	}
+
+	/*
+	 * Obvious sys_chunk_array corruptions, it must hold at least one key
+	 * and one chunk
+	 */
+	if (btrfs_super_sys_array_size(sb) > BTRFS_SYSTEM_CHUNK_ARRAY_SIZE) {
+		btrfs_err(fs_info, "system chunk array too big %u > %u",
+			  btrfs_super_sys_array_size(sb),
+			  BTRFS_SYSTEM_CHUNK_ARRAY_SIZE);
+		ret = -EINVAL;
+	}
+	if (btrfs_super_sys_array_size(sb) < sizeof(struct btrfs_disk_key)
+			+ sizeof(struct btrfs_chunk)) {
+		btrfs_err(fs_info, "system chunk array too small %u < %zu",
+			  btrfs_super_sys_array_size(sb),
+			  sizeof(struct btrfs_disk_key)
+			  + sizeof(struct btrfs_chunk));
+		ret = -EINVAL;
+	}
+
+	/*
+	 * The generation is a global counter, we'll trust it more than the others
+	 * but it's still possible that it's the one that's wrong.
+	 */
+	if (btrfs_super_generation(sb) < btrfs_super_chunk_root_generation(sb))
+		btrfs_warn(fs_info,
+			"suspicious: generation < chunk_root_generation: %llu < %llu",
+			btrfs_super_generation(sb),
+			btrfs_super_chunk_root_generation(sb));
+	if (btrfs_super_generation(sb) < btrfs_super_cache_generation(sb)
+	    && btrfs_super_cache_generation(sb) != (u64)-1)
+		btrfs_warn(fs_info,
+			"suspicious: generation < cache_generation: %llu < %llu",
+			btrfs_super_generation(sb),
+			btrfs_super_cache_generation(sb));
+
+	return ret;
+}
+
+/*
+ * Validation of super block at mount time.
+ * Some checks already done early at mount time, like csum type and incompat
+ * flags will be skipped.
+ */
+static int btrfs_validate_mount_super(struct btrfs_fs_info *fs_info)
+{
+	return validate_super(fs_info, fs_info->super_copy, 0);
+}
+
+/*
+ * Validation of super block at write time.
+ * Some checks like bytenr check will be skipped as their values will be
+ * overwritten soon.
+ * Extra checks like csum type and incompat flags will be done here.
+ */
+static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
+				      struct btrfs_super_block *sb)
+{
+	int ret;
+
+	ret = validate_super(fs_info, sb, -1);
+	if (ret < 0)
+		goto out;
+	if (btrfs_super_csum_type(sb) != BTRFS_CSUM_TYPE_CRC32) {
+		ret = -EUCLEAN;
+		btrfs_err(fs_info, "invalid csum type, has %u want %u",
+			  btrfs_super_csum_type(sb), BTRFS_CSUM_TYPE_CRC32);
+		goto out;
+	}
+	if (btrfs_super_incompat_flags(sb) & ~BTRFS_FEATURE_INCOMPAT_SUPP) {
+		ret = -EUCLEAN;
+		btrfs_err(fs_info,
+		"invalid incompat flags, has 0x%llx valid mask 0x%llx",
+			  btrfs_super_incompat_flags(sb),
+			  (unsigned long long)BTRFS_FEATURE_INCOMPAT_SUPP);
+		goto out;
+	}
+out:
+	if (ret < 0)
+		btrfs_err(fs_info,
+		"super block corruption detected before writing it to disk");
+	return ret;
+}
+
+int open_ctree(struct super_block *sb,
+	       struct btrfs_fs_devices *fs_devices,
+	       char *options)
+{
+	u32 sectorsize;
+	u32 nodesize;
+	u32 stripesize;
+	u64 generation;
+	u64 features;
+	struct btrfs_key location;
+	struct buffer_head *bh;
+	struct btrfs_super_block *disk_super;
+	struct btrfs_fs_info *fs_info = btrfs_sb(sb);
+	struct btrfs_root *tree_root;
+	struct btrfs_root *chunk_root;
+	int ret;
+	int err = -EINVAL;
+	int num_backups_tried = 0;
+	int backup_index = 0;
+	int clear_free_space_tree = 0;
+	int level;
+
+	tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	if (!tree_root || !chunk_root) {
+		err = -ENOMEM;
+		goto fail;
+	}
+
+	ret = init_srcu_struct(&fs_info->subvol_srcu);
+	if (ret) {
+		err = ret;
+		goto fail;
+	}
+
+	ret = percpu_counter_init(&fs_info->dirty_metadata_bytes, 0, GFP_KERNEL);
+	if (ret) {
+		err = ret;
+		goto fail_srcu;
+	}
+	fs_info->dirty_metadata_batch = PAGE_SIZE *
+					(1 + ilog2(nr_cpu_ids));
+
+	ret = percpu_counter_init(&fs_info->delalloc_bytes, 0, GFP_KERNEL);
+	if (ret) {
+		err = ret;
+		goto fail_dirty_metadata_bytes;
+	}
+
+	ret = percpu_counter_init(&fs_info->bio_counter, 0, GFP_KERNEL);
+	if (ret) {
+		err = ret;
+		goto fail_delalloc_bytes;
+	}
+
+	INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_ATOMIC);
+	INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC);
+	INIT_LIST_HEAD(&fs_info->trans_list);
+	INIT_LIST_HEAD(&fs_info->dead_roots);
+	INIT_LIST_HEAD(&fs_info->delayed_iputs);
+	INIT_LIST_HEAD(&fs_info->delalloc_roots);
+	INIT_LIST_HEAD(&fs_info->caching_block_groups);
+	INIT_LIST_HEAD(&fs_info->pending_raid_kobjs);
+	spin_lock_init(&fs_info->pending_raid_kobjs_lock);
+	spin_lock_init(&fs_info->delalloc_root_lock);
+	spin_lock_init(&fs_info->trans_lock);
+	spin_lock_init(&fs_info->fs_roots_radix_lock);
+	spin_lock_init(&fs_info->delayed_iput_lock);
+	spin_lock_init(&fs_info->defrag_inodes_lock);
+	spin_lock_init(&fs_info->tree_mod_seq_lock);
+	spin_lock_init(&fs_info->super_lock);
+	spin_lock_init(&fs_info->qgroup_op_lock);
+	spin_lock_init(&fs_info->buffer_lock);
+	spin_lock_init(&fs_info->unused_bgs_lock);
+	rwlock_init(&fs_info->tree_mod_log_lock);
+	mutex_init(&fs_info->unused_bg_unpin_mutex);
+	mutex_init(&fs_info->delete_unused_bgs_mutex);
+	mutex_init(&fs_info->reloc_mutex);
+	mutex_init(&fs_info->delalloc_root_mutex);
+	mutex_init(&fs_info->cleaner_delayed_iput_mutex);
+	seqlock_init(&fs_info->profiles_lock);
+
+	INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
+	INIT_LIST_HEAD(&fs_info->space_info);
+	INIT_LIST_HEAD(&fs_info->tree_mod_seq_list);
+	INIT_LIST_HEAD(&fs_info->unused_bgs);
+	btrfs_mapping_init(&fs_info->mapping_tree);
+	btrfs_init_block_rsv(&fs_info->global_block_rsv,
+			     BTRFS_BLOCK_RSV_GLOBAL);
+	btrfs_init_block_rsv(&fs_info->trans_block_rsv, BTRFS_BLOCK_RSV_TRANS);
+	btrfs_init_block_rsv(&fs_info->chunk_block_rsv, BTRFS_BLOCK_RSV_CHUNK);
+	btrfs_init_block_rsv(&fs_info->empty_block_rsv, BTRFS_BLOCK_RSV_EMPTY);
+	btrfs_init_block_rsv(&fs_info->delayed_block_rsv,
+			     BTRFS_BLOCK_RSV_DELOPS);
+	atomic_set(&fs_info->async_delalloc_pages, 0);
+	atomic_set(&fs_info->defrag_running, 0);
+	atomic_set(&fs_info->qgroup_op_seq, 0);
+	atomic_set(&fs_info->reada_works_cnt, 0);
+	atomic64_set(&fs_info->tree_mod_seq, 0);
+	fs_info->sb = sb;
+	fs_info->max_inline = BTRFS_DEFAULT_MAX_INLINE;
+	fs_info->metadata_ratio = 0;
+	fs_info->defrag_inodes = RB_ROOT;
+	atomic64_set(&fs_info->free_chunk_space, 0);
+	fs_info->tree_mod_log = RB_ROOT;
+	fs_info->commit_interval = BTRFS_DEFAULT_COMMIT_INTERVAL;
+	fs_info->avg_delayed_ref_runtime = NSEC_PER_SEC >> 6; /* div by 64 */
+	/* readahead state */
+	INIT_RADIX_TREE(&fs_info->reada_tree, GFP_NOFS & ~__GFP_DIRECT_RECLAIM);
+	spin_lock_init(&fs_info->reada_lock);
+	btrfs_init_ref_verify(fs_info);
+
+	fs_info->thread_pool_size = min_t(unsigned long,
+					  num_online_cpus() + 2, 8);
+
+	INIT_LIST_HEAD(&fs_info->ordered_roots);
+	spin_lock_init(&fs_info->ordered_root_lock);
+
+	fs_info->btree_inode = new_inode(sb);
+	if (!fs_info->btree_inode) {
+		err = -ENOMEM;
+		goto fail_bio_counter;
+	}
+	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
+
+	fs_info->delayed_root = kmalloc(sizeof(struct btrfs_delayed_root),
+					GFP_KERNEL);
+	if (!fs_info->delayed_root) {
+		err = -ENOMEM;
+		goto fail_iput;
+	}
+	btrfs_init_delayed_root(fs_info->delayed_root);
+
+	btrfs_init_scrub(fs_info);
+#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
+	fs_info->check_integrity_print_mask = 0;
+#endif
+	btrfs_init_balance(fs_info);
+	btrfs_init_async_reclaim_work(&fs_info->async_reclaim_work);
+
+	sb->s_blocksize = BTRFS_BDEV_BLOCKSIZE;
+	sb->s_blocksize_bits = blksize_bits(BTRFS_BDEV_BLOCKSIZE);
+
+	btrfs_init_btree_inode(fs_info);
+
+	spin_lock_init(&fs_info->block_group_cache_lock);
+	fs_info->block_group_cache_tree = RB_ROOT;
+	fs_info->first_logical_byte = (u64)-1;
+
+	extent_io_tree_init(&fs_info->freed_extents[0], NULL);
+	extent_io_tree_init(&fs_info->freed_extents[1], NULL);
+	fs_info->pinned_extents = &fs_info->freed_extents[0];
+	set_bit(BTRFS_FS_BARRIER, &fs_info->flags);
+
+	mutex_init(&fs_info->ordered_operations_mutex);
+	mutex_init(&fs_info->tree_log_mutex);
+	mutex_init(&fs_info->chunk_mutex);
+	mutex_init(&fs_info->transaction_kthread_mutex);
+	mutex_init(&fs_info->cleaner_mutex);
+	mutex_init(&fs_info->ro_block_group_mutex);
+	init_rwsem(&fs_info->commit_root_sem);
+	init_rwsem(&fs_info->cleanup_work_sem);
+	init_rwsem(&fs_info->subvol_sem);
+	sema_init(&fs_info->uuid_tree_rescan_sem, 1);
+
+	btrfs_init_dev_replace_locks(fs_info);
+	btrfs_init_qgroup(fs_info);
+
+	btrfs_init_free_cluster(&fs_info->meta_alloc_cluster);
+	btrfs_init_free_cluster(&fs_info->data_alloc_cluster);
+
+	init_waitqueue_head(&fs_info->transaction_throttle);
+	init_waitqueue_head(&fs_info->transaction_wait);
+	init_waitqueue_head(&fs_info->transaction_blocked_wait);
+	init_waitqueue_head(&fs_info->async_submit_wait);
+
+	INIT_LIST_HEAD(&fs_info->pinned_chunks);
+
+	/* Usable values until the real ones are cached from the superblock */
+	fs_info->nodesize = 4096;
+	fs_info->sectorsize = 4096;
+	fs_info->stripesize = 4096;
+
+	ret = btrfs_alloc_stripe_hash_table(fs_info);
+	if (ret) {
+		err = ret;
+		goto fail_alloc;
+	}
+
+	__setup_root(tree_root, fs_info, BTRFS_ROOT_TREE_OBJECTID);
+
+	invalidate_bdev(fs_devices->latest_bdev);
+
+	/*
+	 * Read super block and check the signature bytes only
+	 */
+	bh = btrfs_read_dev_super(fs_devices->latest_bdev);
+	if (IS_ERR(bh)) {
+		err = PTR_ERR(bh);
+		goto fail_alloc;
+	}
+
+	/*
+	 * We want to check superblock checksum, the type is stored inside.
+	 * Pass the whole disk block of size BTRFS_SUPER_INFO_SIZE (4k).
+	 */
+	if (btrfs_check_super_csum(fs_info, bh->b_data)) {
+		btrfs_err(fs_info, "superblock checksum mismatch");
+		err = -EINVAL;
+		brelse(bh);
+		goto fail_alloc;
+	}
+
+	/*
+	 * super_copy is zeroed at allocation time and we never touch the
+	 * following bytes up to INFO_SIZE, the checksum is calculated from
+	 * the whole block of INFO_SIZE
+	 */
+	memcpy(fs_info->super_copy, bh->b_data, sizeof(*fs_info->super_copy));
+	memcpy(fs_info->super_for_commit, fs_info->super_copy,
+	       sizeof(*fs_info->super_for_commit));
+	brelse(bh);
+
+	memcpy(fs_info->fsid, fs_info->super_copy->fsid, BTRFS_FSID_SIZE);
+
+	ret = btrfs_validate_mount_super(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "superblock contains fatal errors");
+		err = -EINVAL;
+		goto fail_alloc;
+	}
+
+	disk_super = fs_info->super_copy;
+	if (!btrfs_super_root(disk_super))
+		goto fail_alloc;
+
+	/* check FS state, whether FS is broken. */
+	if (btrfs_super_flags(disk_super) & BTRFS_SUPER_FLAG_ERROR)
+		set_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state);
+
+	/*
+	 * run through our array of backup supers and setup
+	 * our ring pointer to the oldest one
+	 */
+	generation = btrfs_super_generation(disk_super);
+	find_oldest_super_backup(fs_info, generation);
+
+	/*
+	 * In the long term, we'll store the compression type in the super
+	 * block, and it'll be used for per file compression control.
+	 */
+	fs_info->compress_type = BTRFS_COMPRESS_ZLIB;
+
+	ret = btrfs_parse_options(fs_info, options, sb->s_flags);
+	if (ret) {
+		err = ret;
+		goto fail_alloc;
+	}
+
+	features = btrfs_super_incompat_flags(disk_super) &
+		~BTRFS_FEATURE_INCOMPAT_SUPP;
+	if (features) {
+		btrfs_err(fs_info,
+		    "cannot mount because of unsupported optional features (%llx)",
+		    features);
+		err = -EINVAL;
+		goto fail_alloc;
+	}
+
+	features = btrfs_super_incompat_flags(disk_super);
+	features |= BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF;
+	if (fs_info->compress_type == BTRFS_COMPRESS_LZO)
+		features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_LZO;
+	else if (fs_info->compress_type == BTRFS_COMPRESS_ZSTD)
+		features |= BTRFS_FEATURE_INCOMPAT_COMPRESS_ZSTD;
+
+	if (features & BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA)
+		btrfs_info(fs_info, "has skinny extents");
+
+	/*
+	 * flag our filesystem as having big metadata blocks if
+	 * they are bigger than the page size
+	 */
+	if (btrfs_super_nodesize(disk_super) > PAGE_SIZE) {
+		if (!(features & BTRFS_FEATURE_INCOMPAT_BIG_METADATA))
+			btrfs_info(fs_info,
+				"flagging fs with big metadata feature");
+		features |= BTRFS_FEATURE_INCOMPAT_BIG_METADATA;
+	}
+
+	nodesize = btrfs_super_nodesize(disk_super);
+	sectorsize = btrfs_super_sectorsize(disk_super);
+	stripesize = sectorsize;
+	fs_info->dirty_metadata_batch = nodesize * (1 + ilog2(nr_cpu_ids));
+	fs_info->delalloc_batch = sectorsize * 512 * (1 + ilog2(nr_cpu_ids));
+
+	/* Cache block sizes */
+	fs_info->nodesize = nodesize;
+	fs_info->sectorsize = sectorsize;
+	fs_info->stripesize = stripesize;
+
+	/*
+	 * mixed block groups end up with duplicate but slightly offset
+	 * extent buffers for the same range.  It leads to corruptions
+	 */
+	if ((features & BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS) &&
+	    (sectorsize != nodesize)) {
+		btrfs_err(fs_info,
+"unequal nodesize/sectorsize (%u != %u) are not allowed for mixed block groups",
+			nodesize, sectorsize);
+		goto fail_alloc;
+	}
+
+	/*
+	 * Needn't use the lock because there is no other task which will
+	 * update the flag.
+	 */
+	btrfs_set_super_incompat_flags(disk_super, features);
+
+	features = btrfs_super_compat_ro_flags(disk_super) &
+		~BTRFS_FEATURE_COMPAT_RO_SUPP;
+	if (!sb_rdonly(sb) && features) {
+		btrfs_err(fs_info,
+	"cannot mount read-write because of unsupported optional features (%llx)",
+		       features);
+		err = -EINVAL;
+		goto fail_alloc;
+	}
+
+	ret = btrfs_init_workqueues(fs_info, fs_devices);
+	if (ret) {
+		err = ret;
+		goto fail_sb_buffer;
+	}
+
+	sb->s_bdi->congested_fn = btrfs_congested_fn;
+	sb->s_bdi->congested_data = fs_info;
+	sb->s_bdi->capabilities |= BDI_CAP_CGROUP_WRITEBACK;
+	sb->s_bdi->ra_pages = VM_MAX_READAHEAD * SZ_1K / PAGE_SIZE;
+	sb->s_bdi->ra_pages *= btrfs_super_num_devices(disk_super);
+	sb->s_bdi->ra_pages = max(sb->s_bdi->ra_pages, SZ_4M / PAGE_SIZE);
+
+	sb->s_blocksize = sectorsize;
+	sb->s_blocksize_bits = blksize_bits(sectorsize);
+	memcpy(&sb->s_uuid, fs_info->fsid, BTRFS_FSID_SIZE);
+
+	mutex_lock(&fs_info->chunk_mutex);
+	ret = btrfs_read_sys_array(fs_info);
+	mutex_unlock(&fs_info->chunk_mutex);
+	if (ret) {
+		btrfs_err(fs_info, "failed to read the system array: %d", ret);
+		goto fail_sb_buffer;
+	}
+
+	generation = btrfs_super_chunk_root_generation(disk_super);
+	level = btrfs_super_chunk_root_level(disk_super);
+
+	__setup_root(chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);
+
+	chunk_root->node = read_tree_block(fs_info,
+					   btrfs_super_chunk_root(disk_super),
+					   generation, level, NULL);
+	if (IS_ERR(chunk_root->node) ||
+	    !extent_buffer_uptodate(chunk_root->node)) {
+		btrfs_err(fs_info, "failed to read chunk root");
+		if (!IS_ERR(chunk_root->node))
+			free_extent_buffer(chunk_root->node);
+		chunk_root->node = NULL;
+		goto fail_tree_roots;
+	}
+	btrfs_set_root_node(&chunk_root->root_item, chunk_root->node);
+	chunk_root->commit_root = btrfs_root_node(chunk_root);
+
+	read_extent_buffer(chunk_root->node, fs_info->chunk_tree_uuid,
+	   btrfs_header_chunk_tree_uuid(chunk_root->node), BTRFS_UUID_SIZE);
+
+	ret = btrfs_read_chunk_tree(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to read chunk tree: %d", ret);
+		goto fail_tree_roots;
+	}
+
+	/*
+	 * Keep the devid that is marked to be the target device for the
+	 * device replace procedure
+	 */
+	btrfs_free_extra_devids(fs_devices, 0);
+
+	if (!fs_devices->latest_bdev) {
+		btrfs_err(fs_info, "failed to read devices");
+		goto fail_tree_roots;
+	}
+
+retry_root_backup:
+	generation = btrfs_super_generation(disk_super);
+	level = btrfs_super_root_level(disk_super);
+
+	tree_root->node = read_tree_block(fs_info,
+					  btrfs_super_root(disk_super),
+					  generation, level, NULL);
+	if (IS_ERR(tree_root->node) ||
+	    !extent_buffer_uptodate(tree_root->node)) {
+		btrfs_warn(fs_info, "failed to read tree root");
+		if (!IS_ERR(tree_root->node))
+			free_extent_buffer(tree_root->node);
+		tree_root->node = NULL;
+		goto recovery_tree_root;
+	}
+
+	btrfs_set_root_node(&tree_root->root_item, tree_root->node);
+	tree_root->commit_root = btrfs_root_node(tree_root);
+	btrfs_set_root_refs(&tree_root->root_item, 1);
+
+	mutex_lock(&tree_root->objectid_mutex);
+	ret = btrfs_find_highest_objectid(tree_root,
+					&tree_root->highest_objectid);
+	if (ret) {
+		mutex_unlock(&tree_root->objectid_mutex);
+		goto recovery_tree_root;
+	}
+
+	ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
+
+	mutex_unlock(&tree_root->objectid_mutex);
+
+	ret = btrfs_read_roots(fs_info);
+	if (ret)
+		goto recovery_tree_root;
+
+	fs_info->generation = generation;
+	fs_info->last_trans_committed = generation;
+
+	ret = btrfs_verify_dev_extents(fs_info);
+	if (ret) {
+		btrfs_err(fs_info,
+			  "failed to verify dev extents against chunks: %d",
+			  ret);
+		goto fail_block_groups;
+	}
+	ret = btrfs_recover_balance(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to recover balance: %d", ret);
+		goto fail_block_groups;
+	}
+
+	ret = btrfs_init_dev_stats(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init dev_stats: %d", ret);
+		goto fail_block_groups;
+	}
+
+	ret = btrfs_init_dev_replace(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init dev_replace: %d", ret);
+		goto fail_block_groups;
+	}
+
+	btrfs_free_extra_devids(fs_devices, 1);
+
+	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
+				ret);
+		goto fail_block_groups;
+	}
+
+	ret = btrfs_sysfs_add_device(fs_devices);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init sysfs device interface: %d",
+				ret);
+		goto fail_fsdev_sysfs;
+	}
+
+	ret = btrfs_sysfs_add_mounted(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init sysfs interface: %d", ret);
+		goto fail_fsdev_sysfs;
+	}
+
+	ret = btrfs_init_space_info(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to initialize space info: %d", ret);
+		goto fail_sysfs;
+	}
+
+	ret = btrfs_read_block_groups(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to read block groups: %d", ret);
+		goto fail_sysfs;
+	}
+
+	if (!sb_rdonly(sb) && !btrfs_check_rw_degradable(fs_info, NULL)) {
+		btrfs_warn(fs_info,
+		"writeable mount is not allowed due to too many missing devices");
+		goto fail_sysfs;
+	}
+
+	fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
+					       "btrfs-cleaner");
+	if (IS_ERR(fs_info->cleaner_kthread))
+		goto fail_sysfs;
+
+	fs_info->transaction_kthread = kthread_run(transaction_kthread,
+						   tree_root,
+						   "btrfs-transaction");
+	if (IS_ERR(fs_info->transaction_kthread))
+		goto fail_cleaner;
+
+	if (!btrfs_test_opt(fs_info, NOSSD) &&
+	    !fs_info->fs_devices->rotating) {
+		btrfs_set_and_info(fs_info, SSD, "enabling ssd optimizations");
+	}
+
+	/*
+	 * Mount does not set all options immediately, we can do it now and do
+	 * not have to wait for transaction commit
+	 */
+	btrfs_apply_pending_changes(fs_info);
+
+#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
+	if (btrfs_test_opt(fs_info, CHECK_INTEGRITY)) {
+		ret = btrfsic_mount(fs_info, fs_devices,
+				    btrfs_test_opt(fs_info,
+					CHECK_INTEGRITY_INCLUDING_EXTENT_DATA) ?
+				    1 : 0,
+				    fs_info->check_integrity_print_mask);
+		if (ret)
+			btrfs_warn(fs_info,
+				"failed to initialize integrity check module: %d",
+				ret);
+	}
+#endif
+	ret = btrfs_read_qgroup_config(fs_info);
+	if (ret)
+		goto fail_trans_kthread;
+
+	if (btrfs_build_ref_tree(fs_info))
+		btrfs_err(fs_info, "couldn't build ref tree");
+
+	/* do not make disk changes in broken FS or nologreplay is given */
+	if (btrfs_super_log_root(disk_super) != 0 &&
+	    !btrfs_test_opt(fs_info, NOLOGREPLAY)) {
+		ret = btrfs_replay_log(fs_info, fs_devices);
+		if (ret) {
+			err = ret;
+			goto fail_qgroup;
+		}
+	}
+
+	ret = btrfs_find_orphan_roots(fs_info);
+	if (ret)
+		goto fail_qgroup;
+
+	if (!sb_rdonly(sb)) {
+		ret = btrfs_cleanup_fs_roots(fs_info);
+		if (ret)
+			goto fail_qgroup;
+
+		mutex_lock(&fs_info->cleaner_mutex);
+		ret = btrfs_recover_relocation(tree_root);
+		mutex_unlock(&fs_info->cleaner_mutex);
+		if (ret < 0) {
+			btrfs_warn(fs_info, "failed to recover relocation: %d",
+					ret);
+			err = -EINVAL;
+			goto fail_qgroup;
+		}
+	}
+
+	location.objectid = BTRFS_FS_TREE_OBJECTID;
+	location.type = BTRFS_ROOT_ITEM_KEY;
+	location.offset = 0;
+
+	fs_info->fs_root = btrfs_read_fs_root_no_name(fs_info, &location);
+	if (IS_ERR(fs_info->fs_root)) {
+		err = PTR_ERR(fs_info->fs_root);
+		btrfs_warn(fs_info, "failed to read fs tree: %d", err);
+		goto fail_qgroup;
+	}
+
+	if (sb_rdonly(sb))
+		return 0;
+
+	if (btrfs_test_opt(fs_info, CLEAR_CACHE) &&
+	    btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
+		clear_free_space_tree = 1;
+	} else if (btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE) &&
+		   !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID)) {
+		btrfs_warn(fs_info, "free space tree is invalid");
+		clear_free_space_tree = 1;
+	}
+
+	if (clear_free_space_tree) {
+		btrfs_info(fs_info, "clearing free space tree");
+		ret = btrfs_clear_free_space_tree(fs_info);
+		if (ret) {
+			btrfs_warn(fs_info,
+				   "failed to clear free space tree: %d", ret);
+			close_ctree(fs_info);
+			return ret;
+		}
+	}
+
+	if (btrfs_test_opt(fs_info, FREE_SPACE_TREE) &&
+	    !btrfs_fs_compat_ro(fs_info, FREE_SPACE_TREE)) {
+		btrfs_info(fs_info, "creating free space tree");
+		ret = btrfs_create_free_space_tree(fs_info);
+		if (ret) {
+			btrfs_warn(fs_info,
+				"failed to create free space tree: %d", ret);
+			close_ctree(fs_info);
+			return ret;
+		}
+	}
+
+	down_read(&fs_info->cleanup_work_sem);
+	if ((ret = btrfs_orphan_cleanup(fs_info->fs_root)) ||
+	    (ret = btrfs_orphan_cleanup(fs_info->tree_root))) {
+		up_read(&fs_info->cleanup_work_sem);
+		close_ctree(fs_info);
+		return ret;
+	}
+	up_read(&fs_info->cleanup_work_sem);
+
+	ret = btrfs_resume_balance_async(fs_info);
+	if (ret) {
+		btrfs_warn(fs_info, "failed to resume balance: %d", ret);
+		close_ctree(fs_info);
+		return ret;
+	}
+
+	ret = btrfs_resume_dev_replace_async(fs_info);
+	if (ret) {
+		btrfs_warn(fs_info, "failed to resume device replace: %d", ret);
+		close_ctree(fs_info);
+		return ret;
+	}
+
+	btrfs_qgroup_rescan_resume(fs_info);
+
+	if (!fs_info->uuid_root) {
+		btrfs_info(fs_info, "creating UUID tree");
+		ret = btrfs_create_uuid_tree(fs_info);
+		if (ret) {
+			btrfs_warn(fs_info,
+				"failed to create the UUID tree: %d", ret);
+			close_ctree(fs_info);
+			return ret;
+		}
+	} else if (btrfs_test_opt(fs_info, RESCAN_UUID_TREE) ||
+		   fs_info->generation !=
+				btrfs_super_uuid_tree_generation(disk_super)) {
+		btrfs_info(fs_info, "checking UUID tree");
+		ret = btrfs_check_uuid_tree(fs_info);
+		if (ret) {
+			btrfs_warn(fs_info,
+				"failed to check the UUID tree: %d", ret);
+			close_ctree(fs_info);
+			return ret;
+		}
+	} else {
+		set_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags);
+	}
+	set_bit(BTRFS_FS_OPEN, &fs_info->flags);
+
+	/*
+	 * backuproot only affect mount behavior, and if open_ctree succeeded,
+	 * no need to keep the flag
+	 */
+	btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);
+
+	return 0;
+
+fail_qgroup:
+	btrfs_free_qgroup_config(fs_info);
+fail_trans_kthread:
+	kthread_stop(fs_info->transaction_kthread);
+	btrfs_cleanup_transaction(fs_info);
+	btrfs_free_fs_roots(fs_info);
+fail_cleaner:
+	kthread_stop(fs_info->cleaner_kthread);
+
+	/*
+	 * make sure we're done with the btree inode before we stop our
+	 * kthreads
+	 */
+	filemap_write_and_wait(fs_info->btree_inode->i_mapping);
+
+fail_sysfs:
+	btrfs_sysfs_remove_mounted(fs_info);
+
+fail_fsdev_sysfs:
+	btrfs_sysfs_remove_fsid(fs_info->fs_devices);
+
+fail_block_groups:
+	btrfs_put_block_group_cache(fs_info);
+
+fail_tree_roots:
+	free_root_pointers(fs_info, 1);
+	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
+
+fail_sb_buffer:
+	btrfs_stop_all_workers(fs_info);
+	btrfs_free_block_groups(fs_info);
+fail_alloc:
+fail_iput:
+	btrfs_mapping_tree_free(&fs_info->mapping_tree);
+
+	iput(fs_info->btree_inode);
+fail_bio_counter:
+	percpu_counter_destroy(&fs_info->bio_counter);
+fail_delalloc_bytes:
+	percpu_counter_destroy(&fs_info->delalloc_bytes);
+fail_dirty_metadata_bytes:
+	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
+fail_srcu:
+	cleanup_srcu_struct(&fs_info->subvol_srcu);
+fail:
+	btrfs_free_stripe_hash_table(fs_info);
+	btrfs_close_devices(fs_info->fs_devices);
+	return err;
+
+recovery_tree_root:
+	if (!btrfs_test_opt(fs_info, USEBACKUPROOT))
+		goto fail_tree_roots;
+
+	free_root_pointers(fs_info, 0);
+
+	/* don't use the log in recovery mode, it won't be valid */
+	btrfs_set_super_log_root(disk_super, 0);
+
+	/* we can't trust the free space cache either */
+	btrfs_set_opt(fs_info->mount_opt, CLEAR_CACHE);
+
+	ret = next_root_backup(fs_info, fs_info->super_copy,
+			       &num_backups_tried, &backup_index);
+	if (ret == -1)
+		goto fail_block_groups;
+	goto retry_root_backup;
+}
+ALLOW_ERROR_INJECTION(open_ctree, ERRNO);
+
+static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
+{
+	if (uptodate) {
+		set_buffer_uptodate(bh);
+	} else {
+		struct btrfs_device *device = (struct btrfs_device *)
+			bh->b_private;
+
+		btrfs_warn_rl_in_rcu(device->fs_info,
+				"lost page write due to IO error on %s",
+					  rcu_str_deref(device->name));
+		/* note, we don't set_buffer_write_io_error because we have
+		 * our own ways of dealing with the IO errors
+		 */
+		clear_buffer_uptodate(bh);
+		btrfs_dev_stat_inc_and_print(device, BTRFS_DEV_STAT_WRITE_ERRS);
+	}
+	unlock_buffer(bh);
+	put_bh(bh);
+}
+
+int btrfs_read_dev_one_super(struct block_device *bdev, int copy_num,
+			struct buffer_head **bh_ret)
+{
+	struct buffer_head *bh;
+	struct btrfs_super_block *super;
+	u64 bytenr;
+
+	bytenr = btrfs_sb_offset(copy_num);
+	if (bytenr + BTRFS_SUPER_INFO_SIZE >= i_size_read(bdev->bd_inode))
+		return -EINVAL;
+
+	bh = __bread(bdev, bytenr / BTRFS_BDEV_BLOCKSIZE, BTRFS_SUPER_INFO_SIZE);
+	/*
+	 * If we fail to read from the underlying devices, as of now
+	 * the best option we have is to mark it EIO.
+	 */
+	if (!bh)
+		return -EIO;
+
+	super = (struct btrfs_super_block *)bh->b_data;
+	if (btrfs_super_bytenr(super) != bytenr ||
+		    btrfs_super_magic(super) != BTRFS_MAGIC) {
+		brelse(bh);
+		return -EINVAL;
+	}
+
+	*bh_ret = bh;
+	return 0;
+}
+
+
+struct buffer_head *btrfs_read_dev_super(struct block_device *bdev)
+{
+	struct buffer_head *bh;
+	struct buffer_head *latest = NULL;
+	struct btrfs_super_block *super;
+	int i;
+	u64 transid = 0;
+	int ret = -EINVAL;
+
+	/* 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
+	 */
+	for (i = 0; i < 1; i++) {
+		ret = btrfs_read_dev_one_super(bdev, i, &bh);
+		if (ret)
+			continue;
+
+		super = (struct btrfs_super_block *)bh->b_data;
+
+		if (!latest || btrfs_super_generation(super) > transid) {
+			brelse(latest);
+			latest = bh;
+			transid = btrfs_super_generation(super);
+		} else {
+			brelse(bh);
+		}
+	}
+
+	if (!latest)
+		return ERR_PTR(ret);
+
+	return latest;
+}
+
+/*
+ * Write superblock @sb to the @device. Do not wait for completion, all the
+ * buffer heads we write are pinned.
+ *
+ * Write @max_mirrors copies of the superblock, where 0 means default that fit
+ * the expected device size at commit time. Note that max_mirrors must be
+ * same for write and wait phases.
+ *
+ * Return number of errors when buffer head is not found or submission fails.
+ */
+static int write_dev_supers(struct btrfs_device *device,
+			    struct btrfs_super_block *sb, int max_mirrors)
+{
+	struct buffer_head *bh;
+	int i;
+	int ret;
+	int errors = 0;
+	u32 crc;
+	u64 bytenr;
+	int op_flags;
+
+	if (max_mirrors == 0)
+		max_mirrors = BTRFS_SUPER_MIRROR_MAX;
+
+	for (i = 0; i < max_mirrors; i++) {
+		bytenr = btrfs_sb_offset(i);
+		if (bytenr + BTRFS_SUPER_INFO_SIZE >=
+		    device->commit_total_bytes)
+			break;
+
+		btrfs_set_super_bytenr(sb, bytenr);
+
+		crc = ~(u32)0;
+		crc = btrfs_csum_data((const char *)sb + BTRFS_CSUM_SIZE, crc,
+				      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+		btrfs_csum_final(crc, sb->csum);
+
+		/* One reference for us, and we leave it for the caller */
+		bh = __getblk(device->bdev, bytenr / BTRFS_BDEV_BLOCKSIZE,
+			      BTRFS_SUPER_INFO_SIZE);
+		if (!bh) {
+			btrfs_err(device->fs_info,
+			    "couldn't get super buffer head for bytenr %llu",
+			    bytenr);
+			errors++;
+			continue;
+		}
+
+		memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
+
+		/* one reference for submit_bh */
+		get_bh(bh);
+
+		set_buffer_uptodate(bh);
+		lock_buffer(bh);
+		bh->b_end_io = btrfs_end_buffer_write_sync;
+		bh->b_private = device;
+
+		/*
+		 * we fua the first super.  The others we allow
+		 * to go down lazy.
+		 */
+		op_flags = REQ_SYNC | REQ_META | REQ_PRIO;
+		if (i == 0 && !btrfs_test_opt(device->fs_info, NOBARRIER))
+			op_flags |= REQ_FUA;
+		ret = btrfsic_submit_bh(REQ_OP_WRITE, op_flags, bh);
+		if (ret)
+			errors++;
+	}
+	return errors < i ? 0 : -1;
+}
+
+/*
+ * Wait for write completion of superblocks done by write_dev_supers,
+ * @max_mirrors same for write and wait phases.
+ *
+ * Return number of errors when buffer head is not found or not marked up to
+ * date.
+ */
+static int wait_dev_supers(struct btrfs_device *device, int max_mirrors)
+{
+	struct buffer_head *bh;
+	int i;
+	int errors = 0;
+	bool primary_failed = false;
+	u64 bytenr;
+
+	if (max_mirrors == 0)
+		max_mirrors = BTRFS_SUPER_MIRROR_MAX;
+
+	for (i = 0; i < max_mirrors; i++) {
+		bytenr = btrfs_sb_offset(i);
+		if (bytenr + BTRFS_SUPER_INFO_SIZE >=
+		    device->commit_total_bytes)
+			break;
+
+		bh = __find_get_block(device->bdev,
+				      bytenr / BTRFS_BDEV_BLOCKSIZE,
+				      BTRFS_SUPER_INFO_SIZE);
+		if (!bh) {
+			errors++;
+			if (i == 0)
+				primary_failed = true;
+			continue;
+		}
+		wait_on_buffer(bh);
+		if (!buffer_uptodate(bh)) {
+			errors++;
+			if (i == 0)
+				primary_failed = true;
+		}
+
+		/* drop our reference */
+		brelse(bh);
+
+		/* drop the reference from the writing run */
+		brelse(bh);
+	}
+
+	/* log error, force error return */
+	if (primary_failed) {
+		btrfs_err(device->fs_info, "error writing primary super block to device %llu",
+			  device->devid);
+		return -1;
+	}
+
+	return errors < i ? 0 : -1;
+}
+
+/*
+ * endio for the write_dev_flush, this will wake anyone waiting
+ * for the barrier when it is done
+ */
+static void btrfs_end_empty_barrier(struct bio *bio)
+{
+	complete(bio->bi_private);
+}
+
+/*
+ * Submit a flush request to the device if it supports it. Error handling is
+ * done in the waiting counterpart.
+ */
+static void write_dev_flush(struct btrfs_device *device)
+{
+	struct request_queue *q = bdev_get_queue(device->bdev);
+	struct bio *bio = device->flush_bio;
+
+	if (!test_bit(QUEUE_FLAG_WC, &q->queue_flags))
+		return;
+
+	bio_reset(bio);
+	bio->bi_end_io = btrfs_end_empty_barrier;
+	bio_set_dev(bio, device->bdev);
+	bio->bi_opf = REQ_OP_WRITE | REQ_SYNC | REQ_PREFLUSH;
+	init_completion(&device->flush_wait);
+	bio->bi_private = &device->flush_wait;
+
+	btrfsic_submit_bio(bio);
+	set_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
+}
+
+/*
+ * If the flush bio has been submitted by write_dev_flush, wait for it.
+ */
+static blk_status_t wait_dev_flush(struct btrfs_device *device)
+{
+	struct bio *bio = device->flush_bio;
+
+	if (!test_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state))
+		return BLK_STS_OK;
+
+	clear_bit(BTRFS_DEV_STATE_FLUSH_SENT, &device->dev_state);
+	wait_for_completion_io(&device->flush_wait);
+
+	return bio->bi_status;
+}
+
+static int check_barrier_error(struct btrfs_fs_info *fs_info)
+{
+	if (!btrfs_check_rw_degradable(fs_info, NULL))
+		return -EIO;
+	return 0;
+}
+
+/*
+ * send an empty flush down to each device in parallel,
+ * then wait for them
+ */
+static int barrier_all_devices(struct btrfs_fs_info *info)
+{
+	struct list_head *head;
+	struct btrfs_device *dev;
+	int errors_wait = 0;
+	blk_status_t ret;
+
+	lockdep_assert_held(&info->fs_devices->device_list_mutex);
+	/* send down all the barriers */
+	head = &info->fs_devices->devices;
+	list_for_each_entry(dev, head, dev_list) {
+		if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
+			continue;
+		if (!dev->bdev)
+			continue;
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
+		    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
+			continue;
+
+		write_dev_flush(dev);
+		dev->last_flush_error = BLK_STS_OK;
+	}
+
+	/* wait for all the barriers */
+	list_for_each_entry(dev, head, dev_list) {
+		if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
+			continue;
+		if (!dev->bdev) {
+			errors_wait++;
+			continue;
+		}
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
+		    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
+			continue;
+
+		ret = wait_dev_flush(dev);
+		if (ret) {
+			dev->last_flush_error = ret;
+			btrfs_dev_stat_inc_and_print(dev,
+					BTRFS_DEV_STAT_FLUSH_ERRS);
+			errors_wait++;
+		}
+	}
+
+	if (errors_wait) {
+		/*
+		 * At some point we need the status of all disks
+		 * to arrive at the volume status. So error checking
+		 * is being pushed to a separate loop.
+		 */
+		return check_barrier_error(info);
+	}
+	return 0;
+}
+
+int btrfs_get_num_tolerated_disk_barrier_failures(u64 flags)
+{
+	int raid_type;
+	int min_tolerated = INT_MAX;
+
+	if ((flags & BTRFS_BLOCK_GROUP_PROFILE_MASK) == 0 ||
+	    (flags & BTRFS_AVAIL_ALLOC_BIT_SINGLE))
+		min_tolerated = min(min_tolerated,
+				    btrfs_raid_array[BTRFS_RAID_SINGLE].
+				    tolerated_failures);
+
+	for (raid_type = 0; raid_type < BTRFS_NR_RAID_TYPES; raid_type++) {
+		if (raid_type == BTRFS_RAID_SINGLE)
+			continue;
+		if (!(flags & btrfs_raid_array[raid_type].bg_flag))
+			continue;
+		min_tolerated = min(min_tolerated,
+				    btrfs_raid_array[raid_type].
+				    tolerated_failures);
+	}
+
+	if (min_tolerated == INT_MAX) {
+		pr_warn("BTRFS: unknown raid flag: %llu", flags);
+		min_tolerated = 0;
+	}
+
+	return min_tolerated;
+}
+
+int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors)
+{
+	struct list_head *head;
+	struct btrfs_device *dev;
+	struct btrfs_super_block *sb;
+	struct btrfs_dev_item *dev_item;
+	int ret;
+	int do_barriers;
+	int max_errors;
+	int total_errors = 0;
+	u64 flags;
+
+	do_barriers = !btrfs_test_opt(fs_info, NOBARRIER);
+
+	/*
+	 * max_mirrors == 0 indicates we're from commit_transaction,
+	 * not from fsync where the tree roots in fs_info have not
+	 * been consistent on disk.
+	 */
+	if (max_mirrors == 0)
+		backup_super_roots(fs_info);
+
+	sb = fs_info->super_for_commit;
+	dev_item = &sb->dev_item;
+
+	mutex_lock(&fs_info->fs_devices->device_list_mutex);
+	head = &fs_info->fs_devices->devices;
+	max_errors = btrfs_super_num_devices(fs_info->super_copy) - 1;
+
+	if (do_barriers) {
+		ret = barrier_all_devices(fs_info);
+		if (ret) {
+			mutex_unlock(
+				&fs_info->fs_devices->device_list_mutex);
+			btrfs_handle_fs_error(fs_info, ret,
+					      "errors while submitting device barriers.");
+			return ret;
+		}
+	}
+
+	list_for_each_entry(dev, head, dev_list) {
+		if (!dev->bdev) {
+			total_errors++;
+			continue;
+		}
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
+		    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
+			continue;
+
+		btrfs_set_stack_device_generation(dev_item, 0);
+		btrfs_set_stack_device_type(dev_item, dev->type);
+		btrfs_set_stack_device_id(dev_item, dev->devid);
+		btrfs_set_stack_device_total_bytes(dev_item,
+						   dev->commit_total_bytes);
+		btrfs_set_stack_device_bytes_used(dev_item,
+						  dev->commit_bytes_used);
+		btrfs_set_stack_device_io_align(dev_item, dev->io_align);
+		btrfs_set_stack_device_io_width(dev_item, dev->io_width);
+		btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
+		memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
+		memcpy(dev_item->fsid, dev->fs_devices->fsid, BTRFS_FSID_SIZE);
+
+		flags = btrfs_super_flags(sb);
+		btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);
+
+		ret = btrfs_validate_write_super(fs_info, sb);
+		if (ret < 0) {
+			mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+			btrfs_handle_fs_error(fs_info, -EUCLEAN,
+				"unexpected superblock corruption detected");
+			return -EUCLEAN;
+		}
+
+		ret = write_dev_supers(dev, sb, max_mirrors);
+		if (ret)
+			total_errors++;
+	}
+	if (total_errors > max_errors) {
+		btrfs_err(fs_info, "%d errors while writing supers",
+			  total_errors);
+		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+
+		/* FUA is masked off if unsupported and can't be the reason */
+		btrfs_handle_fs_error(fs_info, -EIO,
+				      "%d errors while writing supers",
+				      total_errors);
+		return -EIO;
+	}
+
+	total_errors = 0;
+	list_for_each_entry(dev, head, dev_list) {
+		if (!dev->bdev)
+			continue;
+		if (!test_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &dev->dev_state) ||
+		    !test_bit(BTRFS_DEV_STATE_WRITEABLE, &dev->dev_state))
+			continue;
+
+		ret = wait_dev_supers(dev, max_mirrors);
+		if (ret)
+			total_errors++;
+	}
+	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
+	if (total_errors > max_errors) {
+		btrfs_handle_fs_error(fs_info, -EIO,
+				      "%d errors while writing supers",
+				      total_errors);
+		return -EIO;
+	}
+	return 0;
+}
+
+/* Drop a fs root from the radix tree and free it. */
+void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
+				  struct btrfs_root *root)
+{
+	spin_lock(&fs_info->fs_roots_radix_lock);
+	radix_tree_delete(&fs_info->fs_roots_radix,
+			  (unsigned long)root->root_key.objectid);
+	spin_unlock(&fs_info->fs_roots_radix_lock);
+
+	if (btrfs_root_refs(&root->root_item) == 0)
+		synchronize_srcu(&fs_info->subvol_srcu);
+
+	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
+		btrfs_free_log(NULL, root);
+		if (root->reloc_root) {
+			free_extent_buffer(root->reloc_root->node);
+			free_extent_buffer(root->reloc_root->commit_root);
+			btrfs_put_fs_root(root->reloc_root);
+			root->reloc_root = NULL;
+		}
+	}
+
+	if (root->free_ino_pinned)
+		__btrfs_remove_free_space_cache(root->free_ino_pinned);
+	if (root->free_ino_ctl)
+		__btrfs_remove_free_space_cache(root->free_ino_ctl);
+	btrfs_free_fs_root(root);
+}
+
+void btrfs_free_fs_root(struct btrfs_root *root)
+{
+	iput(root->ino_cache_inode);
+	WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree));
+	if (root->anon_dev)
+		free_anon_bdev(root->anon_dev);
+	if (root->subv_writers)
+		btrfs_free_subvolume_writers(root->subv_writers);
+	free_extent_buffer(root->node);
+	free_extent_buffer(root->commit_root);
+	kfree(root->free_ino_ctl);
+	kfree(root->free_ino_pinned);
+	btrfs_put_fs_root(root);
+}
+
+int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
+{
+	u64 root_objectid = 0;
+	struct btrfs_root *gang[8];
+	int i = 0;
+	int err = 0;
+	unsigned int ret = 0;
+	int index;
+
+	while (1) {
+		index = srcu_read_lock(&fs_info->subvol_srcu);
+		ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
+					     (void **)gang, root_objectid,
+					     ARRAY_SIZE(gang));
+		if (!ret) {
+			srcu_read_unlock(&fs_info->subvol_srcu, index);
+			break;
+		}
+		root_objectid = gang[ret - 1]->root_key.objectid + 1;
+
+		for (i = 0; i < ret; i++) {
+			/* Avoid to grab roots in dead_roots */
+			if (btrfs_root_refs(&gang[i]->root_item) == 0) {
+				gang[i] = NULL;
+				continue;
+			}
+			/* grab all the search result for later use */
+			gang[i] = btrfs_grab_fs_root(gang[i]);
+		}
+		srcu_read_unlock(&fs_info->subvol_srcu, index);
+
+		for (i = 0; i < ret; i++) {
+			if (!gang[i])
+				continue;
+			root_objectid = gang[i]->root_key.objectid;
+			err = btrfs_orphan_cleanup(gang[i]);
+			if (err)
+				break;
+			btrfs_put_fs_root(gang[i]);
+		}
+		root_objectid++;
+	}
+
+	/* release the uncleaned roots due to error */
+	for (; i < ret; i++) {
+		if (gang[i])
+			btrfs_put_fs_root(gang[i]);
+	}
+	return err;
+}
+
+int btrfs_commit_super(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root = fs_info->tree_root;
+	struct btrfs_trans_handle *trans;
+
+	mutex_lock(&fs_info->cleaner_mutex);
+	btrfs_run_delayed_iputs(fs_info);
+	mutex_unlock(&fs_info->cleaner_mutex);
+	wake_up_process(fs_info->cleaner_kthread);
+
+	/* wait until ongoing cleanup work done */
+	down_write(&fs_info->cleanup_work_sem);
+	up_write(&fs_info->cleanup_work_sem);
+
+	trans = btrfs_join_transaction(root);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+	return btrfs_commit_transaction(trans);
+}
+
+void close_ctree(struct btrfs_fs_info *fs_info)
+{
+	int ret;
+
+	set_bit(BTRFS_FS_CLOSING_START, &fs_info->flags);
+	/*
+	 * We don't want the cleaner to start new transactions, add more delayed
+	 * iputs, etc. while we're closing. We can't use kthread_stop() yet
+	 * because that frees the task_struct, and the transaction kthread might
+	 * still try to wake up the cleaner.
+	 */
+	kthread_park(fs_info->cleaner_kthread);
+
+	/* wait for the qgroup rescan worker to stop */
+	btrfs_qgroup_wait_for_completion(fs_info, false);
+
+	/* wait for the uuid_scan task to finish */
+	down(&fs_info->uuid_tree_rescan_sem);
+	/* avoid complains from lockdep et al., set sem back to initial state */
+	up(&fs_info->uuid_tree_rescan_sem);
+
+	/* pause restriper - we want to resume on mount */
+	btrfs_pause_balance(fs_info);
+
+	btrfs_dev_replace_suspend_for_unmount(fs_info);
+
+	btrfs_scrub_cancel(fs_info);
+
+	/* wait for any defraggers to finish */
+	wait_event(fs_info->transaction_wait,
+		   (atomic_read(&fs_info->defrag_running) == 0));
+
+	/* clear out the rbtree of defraggable inodes */
+	btrfs_cleanup_defrag_inodes(fs_info);
+
+	cancel_work_sync(&fs_info->async_reclaim_work);
+
+	if (!sb_rdonly(fs_info->sb)) {
+		/*
+		 * The cleaner kthread is stopped, so do one final pass over
+		 * unused block groups.
+		 */
+		btrfs_delete_unused_bgs(fs_info);
+
+		ret = btrfs_commit_super(fs_info);
+		if (ret)
+			btrfs_err(fs_info, "commit super ret %d", ret);
+	}
+
+	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state) ||
+	    test_bit(BTRFS_FS_STATE_TRANS_ABORTED, &fs_info->fs_state))
+		btrfs_error_commit_super(fs_info);
+
+	kthread_stop(fs_info->transaction_kthread);
+	kthread_stop(fs_info->cleaner_kthread);
+
+	set_bit(BTRFS_FS_CLOSING_DONE, &fs_info->flags);
+
+	btrfs_free_qgroup_config(fs_info);
+	ASSERT(list_empty(&fs_info->delalloc_roots));
+
+	if (percpu_counter_sum(&fs_info->delalloc_bytes)) {
+		btrfs_info(fs_info, "at unmount delalloc count %lld",
+		       percpu_counter_sum(&fs_info->delalloc_bytes));
+	}
+
+	btrfs_sysfs_remove_mounted(fs_info);
+	btrfs_sysfs_remove_fsid(fs_info->fs_devices);
+
+	btrfs_free_fs_roots(fs_info);
+
+	btrfs_put_block_group_cache(fs_info);
+
+	/*
+	 * we must make sure there is not any read request to
+	 * submit after we stopping all workers.
+	 */
+	invalidate_inode_pages2(fs_info->btree_inode->i_mapping);
+	btrfs_stop_all_workers(fs_info);
+
+	btrfs_free_block_groups(fs_info);
+
+	clear_bit(BTRFS_FS_OPEN, &fs_info->flags);
+	free_root_pointers(fs_info, 1);
+
+	iput(fs_info->btree_inode);
+
+#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
+	if (btrfs_test_opt(fs_info, CHECK_INTEGRITY))
+		btrfsic_unmount(fs_info->fs_devices);
+#endif
+
+	btrfs_close_devices(fs_info->fs_devices);
+	btrfs_mapping_tree_free(&fs_info->mapping_tree);
+
+	percpu_counter_destroy(&fs_info->dirty_metadata_bytes);
+	percpu_counter_destroy(&fs_info->delalloc_bytes);
+	percpu_counter_destroy(&fs_info->bio_counter);
+	cleanup_srcu_struct(&fs_info->subvol_srcu);
+
+	btrfs_free_stripe_hash_table(fs_info);
+	btrfs_free_ref_cache(fs_info);
+
+	while (!list_empty(&fs_info->pinned_chunks)) {
+		struct extent_map *em;
+
+		em = list_first_entry(&fs_info->pinned_chunks,
+				      struct extent_map, list);
+		list_del_init(&em->list);
+		free_extent_map(em);
+	}
+}
+
+int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid,
+			  int atomic)
+{
+	int ret;
+	struct inode *btree_inode = buf->pages[0]->mapping->host;
+
+	ret = extent_buffer_uptodate(buf);
+	if (!ret)
+		return ret;
+
+	ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,
+				    parent_transid, atomic);
+	if (ret == -EAGAIN)
+		return ret;
+	return !ret;
+}
+
+void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
+{
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_root *root;
+	u64 transid = btrfs_header_generation(buf);
+	int was_dirty;
+
+#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
+	/*
+	 * This is a fast path so only do this check if we have sanity tests
+	 * enabled.  Normal people shouldn't be using umapped buffers as dirty
+	 * outside of the sanity tests.
+	 */
+	if (unlikely(test_bit(EXTENT_BUFFER_UNMAPPED, &buf->bflags)))
+		return;
+#endif
+	root = BTRFS_I(buf->pages[0]->mapping->host)->root;
+	fs_info = root->fs_info;
+	btrfs_assert_tree_locked(buf);
+	if (transid != fs_info->generation)
+		WARN(1, KERN_CRIT "btrfs transid mismatch buffer %llu, found %llu running %llu\n",
+			buf->start, transid, fs_info->generation);
+	was_dirty = set_extent_buffer_dirty(buf);
+	if (!was_dirty)
+		percpu_counter_add_batch(&fs_info->dirty_metadata_bytes,
+					 buf->len,
+					 fs_info->dirty_metadata_batch);
+#ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
+	/*
+	 * Since btrfs_mark_buffer_dirty() can be called with item pointer set
+	 * but item data not updated.
+	 * So here we should only check item pointers, not item data.
+	 */
+	if (btrfs_header_level(buf) == 0 &&
+	    btrfs_check_leaf_relaxed(fs_info, buf)) {
+		btrfs_print_leaf(buf);
+		ASSERT(0);
+	}
+#endif
+}
+
+static void __btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info,
+					int flush_delayed)
+{
+	/*
+	 * looks as though older kernels can get into trouble with
+	 * this code, they end up stuck in balance_dirty_pages forever
+	 */
+	int ret;
+
+	if (current->flags & PF_MEMALLOC)
+		return;
+
+	if (flush_delayed)
+		btrfs_balance_delayed_items(fs_info);
+
+	ret = __percpu_counter_compare(&fs_info->dirty_metadata_bytes,
+				     BTRFS_DIRTY_METADATA_THRESH,
+				     fs_info->dirty_metadata_batch);
+	if (ret > 0) {
+		balance_dirty_pages_ratelimited(fs_info->btree_inode->i_mapping);
+	}
+}
+
+void btrfs_btree_balance_dirty(struct btrfs_fs_info *fs_info)
+{
+	__btrfs_btree_balance_dirty(fs_info, 1);
+}
+
+void btrfs_btree_balance_dirty_nodelay(struct btrfs_fs_info *fs_info)
+{
+	__btrfs_btree_balance_dirty(fs_info, 0);
+}
+
+int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid, int level,
+		      struct btrfs_key *first_key)
+{
+	struct btrfs_root *root = BTRFS_I(buf->pages[0]->mapping->host)->root;
+	struct btrfs_fs_info *fs_info = root->fs_info;
+
+	return btree_read_extent_buffer_pages(fs_info, buf, parent_transid,
+					      level, first_key);
+}
+
+static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info)
+{
+	/* cleanup FS via transaction */
+	btrfs_cleanup_transaction(fs_info);
+
+	mutex_lock(&fs_info->cleaner_mutex);
+	btrfs_run_delayed_iputs(fs_info);
+	mutex_unlock(&fs_info->cleaner_mutex);
+
+	down_write(&fs_info->cleanup_work_sem);
+	up_write(&fs_info->cleanup_work_sem);
+}
+
+static void btrfs_destroy_ordered_extents(struct btrfs_root *root)
+{
+	struct btrfs_ordered_extent *ordered;
+
+	spin_lock(&root->ordered_extent_lock);
+	/*
+	 * This will just short circuit the ordered completion stuff which will
+	 * make sure the ordered extent gets properly cleaned up.
+	 */
+	list_for_each_entry(ordered, &root->ordered_extents,
+			    root_extent_list)
+		set_bit(BTRFS_ORDERED_IOERR, &ordered->flags);
+	spin_unlock(&root->ordered_extent_lock);
+}
+
+static void btrfs_destroy_all_ordered_extents(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root;
+	struct list_head splice;
+
+	INIT_LIST_HEAD(&splice);
+
+	spin_lock(&fs_info->ordered_root_lock);
+	list_splice_init(&fs_info->ordered_roots, &splice);
+	while (!list_empty(&splice)) {
+		root = list_first_entry(&splice, struct btrfs_root,
+					ordered_root);
+		list_move_tail(&root->ordered_root,
+			       &fs_info->ordered_roots);
+
+		spin_unlock(&fs_info->ordered_root_lock);
+		btrfs_destroy_ordered_extents(root);
+
+		cond_resched();
+		spin_lock(&fs_info->ordered_root_lock);
+	}
+	spin_unlock(&fs_info->ordered_root_lock);
+}
+
+static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
+				      struct btrfs_fs_info *fs_info)
+{
+	struct rb_node *node;
+	struct btrfs_delayed_ref_root *delayed_refs;
+	struct btrfs_delayed_ref_node *ref;
+	int ret = 0;
+
+	delayed_refs = &trans->delayed_refs;
+
+	spin_lock(&delayed_refs->lock);
+	if (atomic_read(&delayed_refs->num_entries) == 0) {
+		spin_unlock(&delayed_refs->lock);
+		btrfs_info(fs_info, "delayed_refs has NO entry");
+		return ret;
+	}
+
+	while ((node = rb_first(&delayed_refs->href_root)) != NULL) {
+		struct btrfs_delayed_ref_head *head;
+		struct rb_node *n;
+		bool pin_bytes = false;
+
+		head = rb_entry(node, struct btrfs_delayed_ref_head,
+				href_node);
+		if (!mutex_trylock(&head->mutex)) {
+			refcount_inc(&head->refs);
+			spin_unlock(&delayed_refs->lock);
+
+			mutex_lock(&head->mutex);
+			mutex_unlock(&head->mutex);
+			btrfs_put_delayed_ref_head(head);
+			spin_lock(&delayed_refs->lock);
+			continue;
+		}
+		spin_lock(&head->lock);
+		while ((n = rb_first(&head->ref_tree)) != NULL) {
+			ref = rb_entry(n, struct btrfs_delayed_ref_node,
+				       ref_node);
+			ref->in_tree = 0;
+			rb_erase(&ref->ref_node, &head->ref_tree);
+			RB_CLEAR_NODE(&ref->ref_node);
+			if (!list_empty(&ref->add_list))
+				list_del(&ref->add_list);
+			atomic_dec(&delayed_refs->num_entries);
+			btrfs_put_delayed_ref(ref);
+		}
+		if (head->must_insert_reserved)
+			pin_bytes = true;
+		btrfs_free_delayed_extent_op(head->extent_op);
+		delayed_refs->num_heads--;
+		if (head->processing == 0)
+			delayed_refs->num_heads_ready--;
+		atomic_dec(&delayed_refs->num_entries);
+		rb_erase(&head->href_node, &delayed_refs->href_root);
+		RB_CLEAR_NODE(&head->href_node);
+		spin_unlock(&head->lock);
+		spin_unlock(&delayed_refs->lock);
+		mutex_unlock(&head->mutex);
+
+		if (pin_bytes)
+			btrfs_pin_extent(fs_info, head->bytenr,
+					 head->num_bytes, 1);
+		btrfs_put_delayed_ref_head(head);
+		cond_resched();
+		spin_lock(&delayed_refs->lock);
+	}
+
+	spin_unlock(&delayed_refs->lock);
+
+	return ret;
+}
+
+static void btrfs_destroy_delalloc_inodes(struct btrfs_root *root)
+{
+	struct btrfs_inode *btrfs_inode;
+	struct list_head splice;
+
+	INIT_LIST_HEAD(&splice);
+
+	spin_lock(&root->delalloc_lock);
+	list_splice_init(&root->delalloc_inodes, &splice);
+
+	while (!list_empty(&splice)) {
+		struct inode *inode = NULL;
+		btrfs_inode = list_first_entry(&splice, struct btrfs_inode,
+					       delalloc_inodes);
+		__btrfs_del_delalloc_inode(root, btrfs_inode);
+		spin_unlock(&root->delalloc_lock);
+
+		/*
+		 * Make sure we get a live inode and that it'll not disappear
+		 * meanwhile.
+		 */
+		inode = igrab(&btrfs_inode->vfs_inode);
+		if (inode) {
+			invalidate_inode_pages2(inode->i_mapping);
+			iput(inode);
+		}
+		spin_lock(&root->delalloc_lock);
+	}
+	spin_unlock(&root->delalloc_lock);
+}
+
+static void btrfs_destroy_all_delalloc_inodes(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_root *root;
+	struct list_head splice;
+
+	INIT_LIST_HEAD(&splice);
+
+	spin_lock(&fs_info->delalloc_root_lock);
+	list_splice_init(&fs_info->delalloc_roots, &splice);
+	while (!list_empty(&splice)) {
+		root = list_first_entry(&splice, struct btrfs_root,
+					 delalloc_root);
+		root = btrfs_grab_fs_root(root);
+		BUG_ON(!root);
+		spin_unlock(&fs_info->delalloc_root_lock);
+
+		btrfs_destroy_delalloc_inodes(root);
+		btrfs_put_fs_root(root);
+
+		spin_lock(&fs_info->delalloc_root_lock);
+	}
+	spin_unlock(&fs_info->delalloc_root_lock);
+}
+
+static int btrfs_destroy_marked_extents(struct btrfs_fs_info *fs_info,
+					struct extent_io_tree *dirty_pages,
+					int mark)
+{
+	int ret;
+	struct extent_buffer *eb;
+	u64 start = 0;
+	u64 end;
+
+	while (1) {
+		ret = find_first_extent_bit(dirty_pages, start, &start, &end,
+					    mark, NULL);
+		if (ret)
+			break;
+
+		clear_extent_bits(dirty_pages, start, end, mark);
+		while (start <= end) {
+			eb = find_extent_buffer(fs_info, start);
+			start += fs_info->nodesize;
+			if (!eb)
+				continue;
+			wait_on_extent_buffer_writeback(eb);
+
+			if (test_and_clear_bit(EXTENT_BUFFER_DIRTY,
+					       &eb->bflags))
+				clear_extent_buffer_dirty(eb);
+			free_extent_buffer_stale(eb);
+		}
+	}
+
+	return ret;
+}
+
+static int btrfs_destroy_pinned_extent(struct btrfs_fs_info *fs_info,
+				       struct extent_io_tree *pinned_extents)
+{
+	struct extent_io_tree *unpin;
+	u64 start;
+	u64 end;
+	int ret;
+	bool loop = true;
+
+	unpin = pinned_extents;
+again:
+	while (1) {
+		/*
+		 * The btrfs_finish_extent_commit() may get the same range as
+		 * ours between find_first_extent_bit and clear_extent_dirty.
+		 * Hence, hold the unused_bg_unpin_mutex to avoid double unpin
+		 * the same extent range.
+		 */
+		mutex_lock(&fs_info->unused_bg_unpin_mutex);
+		ret = find_first_extent_bit(unpin, 0, &start, &end,
+					    EXTENT_DIRTY, NULL);
+		if (ret) {
+			mutex_unlock(&fs_info->unused_bg_unpin_mutex);
+			break;
+		}
+
+		clear_extent_dirty(unpin, start, end);
+		btrfs_error_unpin_extent_range(fs_info, start, end);
+		mutex_unlock(&fs_info->unused_bg_unpin_mutex);
+		cond_resched();
+	}
+
+	if (loop) {
+		if (unpin == &fs_info->freed_extents[0])
+			unpin = &fs_info->freed_extents[1];
+		else
+			unpin = &fs_info->freed_extents[0];
+		loop = false;
+		goto again;
+	}
+
+	return 0;
+}
+
+static void btrfs_cleanup_bg_io(struct btrfs_block_group_cache *cache)
+{
+	struct inode *inode;
+
+	inode = cache->io_ctl.inode;
+	if (inode) {
+		invalidate_inode_pages2(inode->i_mapping);
+		BTRFS_I(inode)->generation = 0;
+		cache->io_ctl.inode = NULL;
+		iput(inode);
+	}
+	btrfs_put_block_group(cache);
+}
+
+void btrfs_cleanup_dirty_bgs(struct btrfs_transaction *cur_trans,
+			     struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_block_group_cache *cache;
+
+	spin_lock(&cur_trans->dirty_bgs_lock);
+	while (!list_empty(&cur_trans->dirty_bgs)) {
+		cache = list_first_entry(&cur_trans->dirty_bgs,
+					 struct btrfs_block_group_cache,
+					 dirty_list);
+
+		if (!list_empty(&cache->io_list)) {
+			spin_unlock(&cur_trans->dirty_bgs_lock);
+			list_del_init(&cache->io_list);
+			btrfs_cleanup_bg_io(cache);
+			spin_lock(&cur_trans->dirty_bgs_lock);
+		}
+
+		list_del_init(&cache->dirty_list);
+		spin_lock(&cache->lock);
+		cache->disk_cache_state = BTRFS_DC_ERROR;
+		spin_unlock(&cache->lock);
+
+		spin_unlock(&cur_trans->dirty_bgs_lock);
+		btrfs_put_block_group(cache);
+		spin_lock(&cur_trans->dirty_bgs_lock);
+	}
+	spin_unlock(&cur_trans->dirty_bgs_lock);
+
+	/*
+	 * Refer to the definition of io_bgs member for details why it's safe
+	 * to use it without any locking
+	 */
+	while (!list_empty(&cur_trans->io_bgs)) {
+		cache = list_first_entry(&cur_trans->io_bgs,
+					 struct btrfs_block_group_cache,
+					 io_list);
+
+		list_del_init(&cache->io_list);
+		spin_lock(&cache->lock);
+		cache->disk_cache_state = BTRFS_DC_ERROR;
+		spin_unlock(&cache->lock);
+		btrfs_cleanup_bg_io(cache);
+	}
+}
+
+void btrfs_cleanup_one_transaction(struct btrfs_transaction *cur_trans,
+				   struct btrfs_fs_info *fs_info)
+{
+	btrfs_cleanup_dirty_bgs(cur_trans, fs_info);
+	ASSERT(list_empty(&cur_trans->dirty_bgs));
+	ASSERT(list_empty(&cur_trans->io_bgs));
+
+	btrfs_destroy_delayed_refs(cur_trans, fs_info);
+
+	cur_trans->state = TRANS_STATE_COMMIT_START;
+	wake_up(&fs_info->transaction_blocked_wait);
+
+	cur_trans->state = TRANS_STATE_UNBLOCKED;
+	wake_up(&fs_info->transaction_wait);
+
+	btrfs_destroy_delayed_inodes(fs_info);
+	btrfs_assert_delayed_root_empty(fs_info);
+
+	btrfs_destroy_marked_extents(fs_info, &cur_trans->dirty_pages,
+				     EXTENT_DIRTY);
+	btrfs_destroy_pinned_extent(fs_info,
+				    fs_info->pinned_extents);
+
+	cur_trans->state =TRANS_STATE_COMPLETED;
+	wake_up(&cur_trans->commit_wait);
+}
+
+static int btrfs_cleanup_transaction(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_transaction *t;
+
+	mutex_lock(&fs_info->transaction_kthread_mutex);
+
+	spin_lock(&fs_info->trans_lock);
+	while (!list_empty(&fs_info->trans_list)) {
+		t = list_first_entry(&fs_info->trans_list,
+				     struct btrfs_transaction, list);
+		if (t->state >= TRANS_STATE_COMMIT_START) {
+			refcount_inc(&t->use_count);
+			spin_unlock(&fs_info->trans_lock);
+			btrfs_wait_for_commit(fs_info, t->transid);
+			btrfs_put_transaction(t);
+			spin_lock(&fs_info->trans_lock);
+			continue;
+		}
+		if (t == fs_info->running_transaction) {
+			t->state = TRANS_STATE_COMMIT_DOING;
+			spin_unlock(&fs_info->trans_lock);
+			/*
+			 * We wait for 0 num_writers since we don't hold a trans
+			 * handle open currently for this transaction.
+			 */
+			wait_event(t->writer_wait,
+				   atomic_read(&t->num_writers) == 0);
+		} else {
+			spin_unlock(&fs_info->trans_lock);
+		}
+		btrfs_cleanup_one_transaction(t, fs_info);
+
+		spin_lock(&fs_info->trans_lock);
+		if (t == fs_info->running_transaction)
+			fs_info->running_transaction = NULL;
+		list_del_init(&t->list);
+		spin_unlock(&fs_info->trans_lock);
+
+		btrfs_put_transaction(t);
+		trace_btrfs_transaction_commit(fs_info->tree_root);
+		spin_lock(&fs_info->trans_lock);
+	}
+	spin_unlock(&fs_info->trans_lock);
+	btrfs_destroy_all_ordered_extents(fs_info);
+	btrfs_destroy_delayed_inodes(fs_info);
+	btrfs_assert_delayed_root_empty(fs_info);
+	btrfs_destroy_pinned_extent(fs_info, fs_info->pinned_extents);
+	btrfs_destroy_all_delalloc_inodes(fs_info);
+	mutex_unlock(&fs_info->transaction_kthread_mutex);
+
+	return 0;
+}
+
+static const struct extent_io_ops btree_extent_io_ops = {
+	/* mandatory callbacks */
+	.submit_bio_hook = btree_submit_bio_hook,
+	.readpage_end_io_hook = btree_readpage_end_io_hook,
+	.readpage_io_failed_hook = btree_io_failed_hook,
+
+	/* optional callbacks */
+};