text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   */
  
  #include <linux/slab.h>
  #include <linux/blkdev.h>
  #include <linux/writeback.h>
  #include <linux/pagevec.h>
  #include "ctree.h"
  #include "transaction.h"
  #include "btrfs_inode.h"
  #include "extent_io.h"
  #include "disk-io.h"
  #include "compression.h"
  
  static struct kmem_cache *btrfs_ordered_extent_cache;
  
  static u64 entry_end(struct btrfs_ordered_extent *entry)
  {
  	if (entry->file_offset + entry->len < entry->file_offset)
  		return (u64)-1;
  	return entry->file_offset + entry->len;
  }
  
  /* returns NULL if the insertion worked, or it returns the node it did find
   * in the tree
   */
  static struct rb_node *tree_insert(struct rb_root *root, u64 file_offset,
  				   struct rb_node *node)
  {
  	struct rb_node **p = &root->rb_node;
  	struct rb_node *parent = NULL;
  	struct btrfs_ordered_extent *entry;
  
  	while (*p) {
  		parent = *p;
  		entry = rb_entry(parent, struct btrfs_ordered_extent, rb_node);
  
  		if (file_offset < entry->file_offset)
  			p = &(*p)->rb_left;
  		else if (file_offset >= entry_end(entry))
  			p = &(*p)->rb_right;
  		else
  			return parent;
  	}
  
  	rb_link_node(node, parent, p);
  	rb_insert_color(node, root);
  	return NULL;
  }
  
  static void ordered_data_tree_panic(struct inode *inode, int errno,
  					       u64 offset)
  {
  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
  	btrfs_panic(fs_info, errno,
  		    "Inconsistency in ordered tree at offset %llu", offset);
  }
  
  /*
   * look for a given offset in the tree, and if it can't be found return the
   * first lesser offset
   */
  static struct rb_node *__tree_search(struct rb_root *root, u64 file_offset,
  				     struct rb_node **prev_ret)
  {
  	struct rb_node *n = root->rb_node;
  	struct rb_node *prev = NULL;
  	struct rb_node *test;
  	struct btrfs_ordered_extent *entry;
  	struct btrfs_ordered_extent *prev_entry = NULL;
  
  	while (n) {
  		entry = rb_entry(n, struct btrfs_ordered_extent, rb_node);
  		prev = n;
  		prev_entry = entry;
  
  		if (file_offset < entry->file_offset)
  			n = n->rb_left;
  		else if (file_offset >= entry_end(entry))
  			n = n->rb_right;
  		else
  			return n;
  	}
  	if (!prev_ret)
  		return NULL;
  
  	while (prev && file_offset >= entry_end(prev_entry)) {
  		test = rb_next(prev);
  		if (!test)
  			break;
  		prev_entry = rb_entry(test, struct btrfs_ordered_extent,
  				      rb_node);
  		if (file_offset < entry_end(prev_entry))
  			break;
  
  		prev = test;
  	}
  	if (prev)
  		prev_entry = rb_entry(prev, struct btrfs_ordered_extent,
  				      rb_node);
  	while (prev && file_offset < entry_end(prev_entry)) {
  		test = rb_prev(prev);
  		if (!test)
  			break;
  		prev_entry = rb_entry(test, struct btrfs_ordered_extent,
  				      rb_node);
  		prev = test;
  	}
  	*prev_ret = prev;
  	return NULL;
  }
  
  /*
   * helper to check if a given offset is inside a given entry
   */
  static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
  {
  	if (file_offset < entry->file_offset ||
  	    entry->file_offset + entry->len <= file_offset)
  		return 0;
  	return 1;
  }
  
  static int range_overlaps(struct btrfs_ordered_extent *entry, u64 file_offset,
  			  u64 len)
  {
  	if (file_offset + len <= entry->file_offset ||
  	    entry->file_offset + entry->len <= file_offset)
  		return 0;
  	return 1;
  }
  
  /*
   * look find the first ordered struct that has this offset, otherwise
   * the first one less than this offset
   */
  static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
  					  u64 file_offset)
  {
  	struct rb_root *root = &tree->tree;
  	struct rb_node *prev = NULL;
  	struct rb_node *ret;
  	struct btrfs_ordered_extent *entry;
  
  	if (tree->last) {
  		entry = rb_entry(tree->last, struct btrfs_ordered_extent,
  				 rb_node);
  		if (offset_in_entry(entry, file_offset))
  			return tree->last;
  	}
  	ret = __tree_search(root, file_offset, &prev);
  	if (!ret)
  		ret = prev;
  	if (ret)
  		tree->last = ret;
  	return ret;
  }
  
  /* allocate and add a new ordered_extent into the per-inode tree.
   * file_offset is the logical offset in the file
   *
   * start is the disk block number of an extent already reserved in the
   * extent allocation tree
   *
   * len is the length of the extent
   *
   * The tree is given a single reference on the ordered extent that was
   * inserted.
   */
  static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
  				      u64 start, u64 len, u64 disk_len,
  				      int type, int dio, int compress_type)
  {
  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
  	struct btrfs_root *root = BTRFS_I(inode)->root;
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	entry = kmem_cache_zalloc(btrfs_ordered_extent_cache, GFP_NOFS);
  	if (!entry)
  		return -ENOMEM;
  
  	entry->file_offset = file_offset;
  	entry->start = start;
  	entry->len = len;
  	entry->disk_len = disk_len;
  	entry->bytes_left = len;
  	entry->inode = igrab(inode);
  	entry->compress_type = compress_type;
  	entry->truncated_len = (u64)-1;
  	if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
  		set_bit(type, &entry->flags);
  
  	if (dio)
  		set_bit(BTRFS_ORDERED_DIRECT, &entry->flags);
  
  	/* one ref for the tree */
  	refcount_set(&entry->refs, 1);
  	init_waitqueue_head(&entry->wait);
  	INIT_LIST_HEAD(&entry->list);
  	INIT_LIST_HEAD(&entry->root_extent_list);
  	INIT_LIST_HEAD(&entry->work_list);
  	init_completion(&entry->completion);
  	INIT_LIST_HEAD(&entry->log_list);
  	INIT_LIST_HEAD(&entry->trans_list);
  
  	trace_btrfs_ordered_extent_add(inode, entry);
  
  	spin_lock_irq(&tree->lock);
  	node = tree_insert(&tree->tree, file_offset,
  			   &entry->rb_node);
  	if (node)
  		ordered_data_tree_panic(inode, -EEXIST, file_offset);
  	spin_unlock_irq(&tree->lock);
  
  	spin_lock(&root->ordered_extent_lock);
  	list_add_tail(&entry->root_extent_list,
  		      &root->ordered_extents);
  	root->nr_ordered_extents++;
  	if (root->nr_ordered_extents == 1) {
  		spin_lock(&fs_info->ordered_root_lock);
  		BUG_ON(!list_empty(&root->ordered_root));
  		list_add_tail(&root->ordered_root, &fs_info->ordered_roots);
  		spin_unlock(&fs_info->ordered_root_lock);
  	}
  	spin_unlock(&root->ordered_extent_lock);
  
  	/*
  	 * We don't need the count_max_extents here, we can assume that all of
  	 * that work has been done at higher layers, so this is truly the
  	 * smallest the extent is going to get.
  	 */
  	spin_lock(&BTRFS_I(inode)->lock);
  	btrfs_mod_outstanding_extents(BTRFS_I(inode), 1);
  	spin_unlock(&BTRFS_I(inode)->lock);
  
  	return 0;
  }
  
  int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
  			     u64 start, u64 len, u64 disk_len, int type)
  {
  	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
  					  disk_len, type, 0,
  					  BTRFS_COMPRESS_NONE);
  }
  
  int btrfs_add_ordered_extent_dio(struct inode *inode, u64 file_offset,
  				 u64 start, u64 len, u64 disk_len, int type)
  {
  	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
  					  disk_len, type, 1,
  					  BTRFS_COMPRESS_NONE);
  }
  
  int btrfs_add_ordered_extent_compress(struct inode *inode, u64 file_offset,
  				      u64 start, u64 len, u64 disk_len,
  				      int type, int compress_type)
  {
  	return __btrfs_add_ordered_extent(inode, file_offset, start, len,
  					  disk_len, type, 0,
  					  compress_type);
  }
  
  /*
   * Add a struct btrfs_ordered_sum into the list of checksums to be inserted
   * when an ordered extent is finished.  If the list covers more than one
   * ordered extent, it is split across multiples.
   */
  void btrfs_add_ordered_sum(struct inode *inode,
  			   struct btrfs_ordered_extent *entry,
  			   struct btrfs_ordered_sum *sum)
  {
  	struct btrfs_ordered_inode_tree *tree;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	list_add_tail(&sum->list, &entry->list);
  	spin_unlock_irq(&tree->lock);
  }
  
  /*
   * this is used to account for finished IO across a given range
   * of the file.  The IO may span ordered extents.  If
   * a given ordered_extent is completely done, 1 is returned, otherwise
   * 0.
   *
   * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
   * to make sure this function only returns 1 once for a given ordered extent.
   *
   * file_offset is updated to one byte past the range that is recorded as
   * complete.  This allows you to walk forward in the file.
   */
  int btrfs_dec_test_first_ordered_pending(struct inode *inode,
  				   struct btrfs_ordered_extent **cached,
  				   u64 *file_offset, u64 io_size, int uptodate)
  {
  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry = NULL;
  	int ret;
  	unsigned long flags;
  	u64 dec_end;
  	u64 dec_start;
  	u64 to_dec;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	spin_lock_irqsave(&tree->lock, flags);
  	node = tree_search(tree, *file_offset);
  	if (!node) {
  		ret = 1;
  		goto out;
  	}
  
  	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  	if (!offset_in_entry(entry, *file_offset)) {
  		ret = 1;
  		goto out;
  	}
  
  	dec_start = max(*file_offset, entry->file_offset);
  	dec_end = min(*file_offset + io_size, entry->file_offset +
  		      entry->len);
  	*file_offset = dec_end;
  	if (dec_start > dec_end) {
  		btrfs_crit(fs_info, "bad ordering dec_start %llu end %llu",
  			   dec_start, dec_end);
  	}
  	to_dec = dec_end - dec_start;
  	if (to_dec > entry->bytes_left) {
  		btrfs_crit(fs_info,
  			   "bad ordered accounting left %llu size %llu",
  			   entry->bytes_left, to_dec);
  	}
  	entry->bytes_left -= to_dec;
  	if (!uptodate)
  		set_bit(BTRFS_ORDERED_IOERR, &entry->flags);
  
  	if (entry->bytes_left == 0) {
  		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
  		/* test_and_set_bit implies a barrier */
  		cond_wake_up_nomb(&entry->wait);
  	} else {
  		ret = 1;
  	}
  out:
  	if (!ret && cached && entry) {
  		*cached = entry;
  		refcount_inc(&entry->refs);
  	}
  	spin_unlock_irqrestore(&tree->lock, flags);
  	return ret == 0;
  }
  
  /*
   * this is used to account for finished IO across a given range
   * of the file.  The IO should not span ordered extents.  If
   * a given ordered_extent is completely done, 1 is returned, otherwise
   * 0.
   *
   * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
   * to make sure this function only returns 1 once for a given ordered extent.
   */
  int btrfs_dec_test_ordered_pending(struct inode *inode,
  				   struct btrfs_ordered_extent **cached,
  				   u64 file_offset, u64 io_size, int uptodate)
  {
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry = NULL;
  	unsigned long flags;
  	int ret;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	spin_lock_irqsave(&tree->lock, flags);
  	if (cached && *cached) {
  		entry = *cached;
  		goto have_entry;
  	}
  
  	node = tree_search(tree, file_offset);
  	if (!node) {
  		ret = 1;
  		goto out;
  	}
  
  	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  have_entry:
  	if (!offset_in_entry(entry, file_offset)) {
  		ret = 1;
  		goto out;
  	}
  
  	if (io_size > entry->bytes_left) {
  		btrfs_crit(BTRFS_I(inode)->root->fs_info,
  			   "bad ordered accounting left %llu size %llu",
  		       entry->bytes_left, io_size);
  	}
  	entry->bytes_left -= io_size;
  	if (!uptodate)
  		set_bit(BTRFS_ORDERED_IOERR, &entry->flags);
  
  	if (entry->bytes_left == 0) {
  		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
  		/* test_and_set_bit implies a barrier */
  		cond_wake_up_nomb(&entry->wait);
  	} else {
  		ret = 1;
  	}
  out:
  	if (!ret && cached && entry) {
  		*cached = entry;
  		refcount_inc(&entry->refs);
  	}
  	spin_unlock_irqrestore(&tree->lock, flags);
  	return ret == 0;
  }
  
  /* Needs to either be called under a log transaction or the log_mutex */
  void btrfs_get_logged_extents(struct btrfs_inode *inode,
  			      struct list_head *logged_list,
  			      const loff_t start,
  			      const loff_t end)
  {
  	struct btrfs_ordered_inode_tree *tree;
  	struct btrfs_ordered_extent *ordered;
  	struct rb_node *n;
  	struct rb_node *prev;
  
  	tree = &inode->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	n = __tree_search(&tree->tree, end, &prev);
  	if (!n)
  		n = prev;
  	for (; n; n = rb_prev(n)) {
  		ordered = rb_entry(n, struct btrfs_ordered_extent, rb_node);
  		if (ordered->file_offset > end)
  			continue;
  		if (entry_end(ordered) <= start)
  			break;
  		if (test_and_set_bit(BTRFS_ORDERED_LOGGED, &ordered->flags))
  			continue;
  		list_add(&ordered->log_list, logged_list);
  		refcount_inc(&ordered->refs);
  	}
  	spin_unlock_irq(&tree->lock);
  }
  
  void btrfs_put_logged_extents(struct list_head *logged_list)
  {
  	struct btrfs_ordered_extent *ordered;
  
  	while (!list_empty(logged_list)) {
  		ordered = list_first_entry(logged_list,
  					   struct btrfs_ordered_extent,
  					   log_list);
  		list_del_init(&ordered->log_list);
  		btrfs_put_ordered_extent(ordered);
  	}
  }
  
  void btrfs_submit_logged_extents(struct list_head *logged_list,
  				 struct btrfs_root *log)
  {
  	int index = log->log_transid % 2;
  
  	spin_lock_irq(&log->log_extents_lock[index]);
  	list_splice_tail(logged_list, &log->logged_list[index]);
  	spin_unlock_irq(&log->log_extents_lock[index]);
  }
  
  void btrfs_wait_logged_extents(struct btrfs_trans_handle *trans,
  			       struct btrfs_root *log, u64 transid)
  {
  	struct btrfs_ordered_extent *ordered;
  	int index = transid % 2;
  
  	spin_lock_irq(&log->log_extents_lock[index]);
  	while (!list_empty(&log->logged_list[index])) {
  		struct inode *inode;
  		ordered = list_first_entry(&log->logged_list[index],
  					   struct btrfs_ordered_extent,
  					   log_list);
  		list_del_init(&ordered->log_list);
  		inode = ordered->inode;
  		spin_unlock_irq(&log->log_extents_lock[index]);
  
  		if (!test_bit(BTRFS_ORDERED_IO_DONE, &ordered->flags) &&
  		    !test_bit(BTRFS_ORDERED_DIRECT, &ordered->flags)) {
  			u64 start = ordered->file_offset;
  			u64 end = ordered->file_offset + ordered->len - 1;
  
  			WARN_ON(!inode);
  			filemap_fdatawrite_range(inode->i_mapping, start, end);
  		}
  		wait_event(ordered->wait, test_bit(BTRFS_ORDERED_IO_DONE,
  						   &ordered->flags));
  
  		/*
  		 * In order to keep us from losing our ordered extent
  		 * information when committing the transaction we have to make
  		 * sure that any logged extents are completed when we go to
  		 * commit the transaction.  To do this we simply increase the
  		 * current transactions pending_ordered counter and decrement it
  		 * when the ordered extent completes.
  		 */
  		if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
  			struct btrfs_ordered_inode_tree *tree;
  
  			tree = &BTRFS_I(inode)->ordered_tree;
  			spin_lock_irq(&tree->lock);
  			if (!test_bit(BTRFS_ORDERED_COMPLETE, &ordered->flags)) {
  				set_bit(BTRFS_ORDERED_PENDING, &ordered->flags);
  				atomic_inc(&trans->transaction->pending_ordered);
  			}
  			spin_unlock_irq(&tree->lock);
  		}
  		btrfs_put_ordered_extent(ordered);
  		spin_lock_irq(&log->log_extents_lock[index]);
  	}
  	spin_unlock_irq(&log->log_extents_lock[index]);
  }
  
  void btrfs_free_logged_extents(struct btrfs_root *log, u64 transid)
  {
  	struct btrfs_ordered_extent *ordered;
  	int index = transid % 2;
  
  	spin_lock_irq(&log->log_extents_lock[index]);
  	while (!list_empty(&log->logged_list[index])) {
  		ordered = list_first_entry(&log->logged_list[index],
  					   struct btrfs_ordered_extent,
  					   log_list);
  		list_del_init(&ordered->log_list);
  		spin_unlock_irq(&log->log_extents_lock[index]);
  		btrfs_put_ordered_extent(ordered);
  		spin_lock_irq(&log->log_extents_lock[index]);
  	}
  	spin_unlock_irq(&log->log_extents_lock[index]);
  }
  
  /*
   * used to drop a reference on an ordered extent.  This will free
   * the extent if the last reference is dropped
   */
  void btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
  {
  	struct list_head *cur;
  	struct btrfs_ordered_sum *sum;
  
  	trace_btrfs_ordered_extent_put(entry->inode, entry);
  
  	if (refcount_dec_and_test(&entry->refs)) {
  		ASSERT(list_empty(&entry->log_list));
  		ASSERT(list_empty(&entry->trans_list));
  		ASSERT(list_empty(&entry->root_extent_list));
  		ASSERT(RB_EMPTY_NODE(&entry->rb_node));
  		if (entry->inode)
  			btrfs_add_delayed_iput(entry->inode);
  		while (!list_empty(&entry->list)) {
  			cur = entry->list.next;
  			sum = list_entry(cur, struct btrfs_ordered_sum, list);
  			list_del(&sum->list);
  			kfree(sum);
  		}
  		kmem_cache_free(btrfs_ordered_extent_cache, entry);
  	}
  }
  
  /*
   * remove an ordered extent from the tree.  No references are dropped
   * and waiters are woken up.
   */
  void btrfs_remove_ordered_extent(struct inode *inode,
  				 struct btrfs_ordered_extent *entry)
  {
  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
  	struct btrfs_ordered_inode_tree *tree;
  	struct btrfs_inode *btrfs_inode = BTRFS_I(inode);
  	struct btrfs_root *root = btrfs_inode->root;
  	struct rb_node *node;
  	bool dec_pending_ordered = false;
  
  	/* This is paired with btrfs_add_ordered_extent. */
  	spin_lock(&btrfs_inode->lock);
  	btrfs_mod_outstanding_extents(btrfs_inode, -1);
  	spin_unlock(&btrfs_inode->lock);
  	if (root != fs_info->tree_root)
  		btrfs_delalloc_release_metadata(btrfs_inode, entry->len, false);
  
  	tree = &btrfs_inode->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	node = &entry->rb_node;
  	rb_erase(node, &tree->tree);
  	RB_CLEAR_NODE(node);
  	if (tree->last == node)
  		tree->last = NULL;
  	set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);
  	if (test_and_clear_bit(BTRFS_ORDERED_PENDING, &entry->flags))
  		dec_pending_ordered = true;
  	spin_unlock_irq(&tree->lock);
  
  	/*
  	 * The current running transaction is waiting on us, we need to let it
  	 * know that we're complete and wake it up.
  	 */
  	if (dec_pending_ordered) {
  		struct btrfs_transaction *trans;
  
  		/*
  		 * The checks for trans are just a formality, it should be set,
  		 * but if it isn't we don't want to deref/assert under the spin
  		 * lock, so be nice and check if trans is set, but ASSERT() so
  		 * if it isn't set a developer will notice.
  		 */
  		spin_lock(&fs_info->trans_lock);
  		trans = fs_info->running_transaction;
  		if (trans)
  			refcount_inc(&trans->use_count);
  		spin_unlock(&fs_info->trans_lock);
  
  		ASSERT(trans);
  		if (trans) {
  			if (atomic_dec_and_test(&trans->pending_ordered))
  				wake_up(&trans->pending_wait);
  			btrfs_put_transaction(trans);
  		}
  	}
  
  	spin_lock(&root->ordered_extent_lock);
  	list_del_init(&entry->root_extent_list);
  	root->nr_ordered_extents--;
  
  	trace_btrfs_ordered_extent_remove(inode, entry);
  
  	if (!root->nr_ordered_extents) {
  		spin_lock(&fs_info->ordered_root_lock);
  		BUG_ON(list_empty(&root->ordered_root));
  		list_del_init(&root->ordered_root);
  		spin_unlock(&fs_info->ordered_root_lock);
  	}
  	spin_unlock(&root->ordered_extent_lock);
  	wake_up(&entry->wait);
  }
  
  static void btrfs_run_ordered_extent_work(struct btrfs_work *work)
  {
  	struct btrfs_ordered_extent *ordered;
  
  	ordered = container_of(work, struct btrfs_ordered_extent, flush_work);
  	btrfs_start_ordered_extent(ordered->inode, ordered, 1);
  	complete(&ordered->completion);
  }
  
  /*
   * wait for all the ordered extents in a root.  This is done when balancing
   * space between drives.
   */
  u64 btrfs_wait_ordered_extents(struct btrfs_root *root, u64 nr,
  			       const u64 range_start, const u64 range_len)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	LIST_HEAD(splice);
  	LIST_HEAD(skipped);
  	LIST_HEAD(works);
  	struct btrfs_ordered_extent *ordered, *next;
  	u64 count = 0;
  	const u64 range_end = range_start + range_len;
  
  	mutex_lock(&root->ordered_extent_mutex);
  	spin_lock(&root->ordered_extent_lock);
  	list_splice_init(&root->ordered_extents, &splice);
  	while (!list_empty(&splice) && nr) {
  		ordered = list_first_entry(&splice, struct btrfs_ordered_extent,
  					   root_extent_list);
  
  		if (range_end <= ordered->start ||
  		    ordered->start + ordered->disk_len <= range_start) {
  			list_move_tail(&ordered->root_extent_list, &skipped);
  			cond_resched_lock(&root->ordered_extent_lock);
  			continue;
  		}
  
  		list_move_tail(&ordered->root_extent_list,
  			       &root->ordered_extents);
  		refcount_inc(&ordered->refs);
  		spin_unlock(&root->ordered_extent_lock);
  
  		btrfs_init_work(&ordered->flush_work,
  				btrfs_flush_delalloc_helper,
  				btrfs_run_ordered_extent_work, NULL, NULL);
  		list_add_tail(&ordered->work_list, &works);
  		btrfs_queue_work(fs_info->flush_workers, &ordered->flush_work);
  
  		cond_resched();
  		spin_lock(&root->ordered_extent_lock);
  		if (nr != U64_MAX)
  			nr--;
  		count++;
  	}
  	list_splice_tail(&skipped, &root->ordered_extents);
  	list_splice_tail(&splice, &root->ordered_extents);
  	spin_unlock(&root->ordered_extent_lock);
  
  	list_for_each_entry_safe(ordered, next, &works, work_list) {
  		list_del_init(&ordered->work_list);
  		wait_for_completion(&ordered->completion);
  		btrfs_put_ordered_extent(ordered);
  		cond_resched();
  	}
  	mutex_unlock(&root->ordered_extent_mutex);
  
  	return count;
  }
  
  u64 btrfs_wait_ordered_roots(struct btrfs_fs_info *fs_info, u64 nr,
  			     const u64 range_start, const u64 range_len)
  {
  	struct btrfs_root *root;
  	struct list_head splice;
  	u64 total_done = 0;
  	u64 done;
  
  	INIT_LIST_HEAD(&splice);
  
  	mutex_lock(&fs_info->ordered_operations_mutex);
  	spin_lock(&fs_info->ordered_root_lock);
  	list_splice_init(&fs_info->ordered_roots, &splice);
  	while (!list_empty(&splice) && nr) {
  		root = list_first_entry(&splice, struct btrfs_root,
  					ordered_root);
  		root = btrfs_grab_fs_root(root);
  		BUG_ON(!root);
  		list_move_tail(&root->ordered_root,
  			       &fs_info->ordered_roots);
  		spin_unlock(&fs_info->ordered_root_lock);
  
  		done = btrfs_wait_ordered_extents(root, nr,
  						  range_start, range_len);
  		btrfs_put_fs_root(root);
  		total_done += done;
  
  		spin_lock(&fs_info->ordered_root_lock);
  		if (nr != U64_MAX) {
  			nr -= done;
  		}
  	}
  	list_splice_tail(&splice, &fs_info->ordered_roots);
  	spin_unlock(&fs_info->ordered_root_lock);
  	mutex_unlock(&fs_info->ordered_operations_mutex);
  
  	return total_done;
  }
  
  /*
   * Used to start IO or wait for a given ordered extent to finish.
   *
   * If wait is one, this effectively waits on page writeback for all the pages
   * in the extent, and it waits on the io completion code to insert
   * metadata into the btree corresponding to the extent
   */
  void btrfs_start_ordered_extent(struct inode *inode,
  				       struct btrfs_ordered_extent *entry,
  				       int wait)
  {
  	u64 start = entry->file_offset;
  	u64 end = start + entry->len - 1;
  
  	trace_btrfs_ordered_extent_start(inode, entry);
  
  	/*
  	 * pages in the range can be dirty, clean or writeback.  We
  	 * start IO on any dirty ones so the wait doesn't stall waiting
  	 * for the flusher thread to find them
  	 */
  	if (!test_bit(BTRFS_ORDERED_DIRECT, &entry->flags))
  		filemap_fdatawrite_range(inode->i_mapping, start, end);
  	if (wait) {
  		wait_event(entry->wait, test_bit(BTRFS_ORDERED_COMPLETE,
  						 &entry->flags));
  	}
  }
  
  /*
   * Used to wait on ordered extents across a large range of bytes.
   */
  int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
  {
  	int ret = 0;
  	int ret_wb = 0;
  	u64 end;
  	u64 orig_end;
  	struct btrfs_ordered_extent *ordered;
  
  	if (start + len < start) {
  		orig_end = INT_LIMIT(loff_t);
  	} else {
  		orig_end = start + len - 1;
  		if (orig_end > INT_LIMIT(loff_t))
  			orig_end = INT_LIMIT(loff_t);
  	}
  
  	/* start IO across the range first to instantiate any delalloc
  	 * extents
  	 */
  	ret = btrfs_fdatawrite_range(inode, start, orig_end);
  	if (ret)
  		return ret;
  
  	/*
  	 * If we have a writeback error don't return immediately. Wait first
  	 * for any ordered extents that haven't completed yet. This is to make
  	 * sure no one can dirty the same page ranges and call writepages()
  	 * before the ordered extents complete - to avoid failures (-EEXIST)
  	 * when adding the new ordered extents to the ordered tree.
  	 */
  	ret_wb = filemap_fdatawait_range(inode->i_mapping, start, orig_end);
  
  	end = orig_end;
  	while (1) {
  		ordered = btrfs_lookup_first_ordered_extent(inode, end);
  		if (!ordered)
  			break;
  		if (ordered->file_offset > orig_end) {
  			btrfs_put_ordered_extent(ordered);
  			break;
  		}
  		if (ordered->file_offset + ordered->len <= start) {
  			btrfs_put_ordered_extent(ordered);
  			break;
  		}
  		btrfs_start_ordered_extent(inode, ordered, 1);
  		end = ordered->file_offset;
  		if (test_bit(BTRFS_ORDERED_IOERR, &ordered->flags))
  			ret = -EIO;
  		btrfs_put_ordered_extent(ordered);
  		if (ret || end == 0 || end == start)
  			break;
  		end--;
  	}
  	return ret_wb ? ret_wb : ret;
  }
  
  /*
   * find an ordered extent corresponding to file_offset.  return NULL if
   * nothing is found, otherwise take a reference on the extent and return it
   */
  struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
  							 u64 file_offset)
  {
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry = NULL;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	node = tree_search(tree, file_offset);
  	if (!node)
  		goto out;
  
  	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  	if (!offset_in_entry(entry, file_offset))
  		entry = NULL;
  	if (entry)
  		refcount_inc(&entry->refs);
  out:
  	spin_unlock_irq(&tree->lock);
  	return entry;
  }
  
  /* Since the DIO code tries to lock a wide area we need to look for any ordered
   * extents that exist in the range, rather than just the start of the range.
   */
  struct btrfs_ordered_extent *btrfs_lookup_ordered_range(
  		struct btrfs_inode *inode, u64 file_offset, u64 len)
  {
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry = NULL;
  
  	tree = &inode->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	node = tree_search(tree, file_offset);
  	if (!node) {
  		node = tree_search(tree, file_offset + len);
  		if (!node)
  			goto out;
  	}
  
  	while (1) {
  		entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  		if (range_overlaps(entry, file_offset, len))
  			break;
  
  		if (entry->file_offset >= file_offset + len) {
  			entry = NULL;
  			break;
  		}
  		entry = NULL;
  		node = rb_next(node);
  		if (!node)
  			break;
  	}
  out:
  	if (entry)
  		refcount_inc(&entry->refs);
  	spin_unlock_irq(&tree->lock);
  	return entry;
  }
  
  bool btrfs_have_ordered_extents_in_range(struct inode *inode,
  					 u64 file_offset,
  					 u64 len)
  {
  	struct btrfs_ordered_extent *oe;
  
  	oe = btrfs_lookup_ordered_range(BTRFS_I(inode), file_offset, len);
  	if (oe) {
  		btrfs_put_ordered_extent(oe);
  		return true;
  	}
  	return false;
  }
  
  /*
   * lookup and return any extent before 'file_offset'.  NULL is returned
   * if none is found
   */
  struct btrfs_ordered_extent *
  btrfs_lookup_first_ordered_extent(struct inode *inode, u64 file_offset)
  {
  	struct btrfs_ordered_inode_tree *tree;
  	struct rb_node *node;
  	struct btrfs_ordered_extent *entry = NULL;
  
  	tree = &BTRFS_I(inode)->ordered_tree;
  	spin_lock_irq(&tree->lock);
  	node = tree_search(tree, file_offset);
  	if (!node)
  		goto out;
  
  	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  	refcount_inc(&entry->refs);
  out:
  	spin_unlock_irq(&tree->lock);
  	return entry;
  }
  
  /*
   * After an extent is done, call this to conditionally update the on disk
   * i_size.  i_size is updated to cover any fully written part of the file.
   */
  int btrfs_ordered_update_i_size(struct inode *inode, u64 offset,
  				struct btrfs_ordered_extent *ordered)
  {
  	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
  	u64 disk_i_size;
  	u64 new_i_size;
  	u64 i_size = i_size_read(inode);
  	struct rb_node *node;
  	struct rb_node *prev = NULL;
  	struct btrfs_ordered_extent *test;
  	int ret = 1;
  	u64 orig_offset = offset;
  
  	spin_lock_irq(&tree->lock);
  	if (ordered) {
  		offset = entry_end(ordered);
  		if (test_bit(BTRFS_ORDERED_TRUNCATED, &ordered->flags))
  			offset = min(offset,
  				     ordered->file_offset +
  				     ordered->truncated_len);
  	} else {
  		offset = ALIGN(offset, btrfs_inode_sectorsize(inode));
  	}
  	disk_i_size = BTRFS_I(inode)->disk_i_size;
  
  	/*
  	 * truncate file.
  	 * If ordered is not NULL, then this is called from endio and
  	 * disk_i_size will be updated by either truncate itself or any
  	 * in-flight IOs which are inside the disk_i_size.
  	 *
  	 * Because btrfs_setsize() may set i_size with disk_i_size if truncate
  	 * fails somehow, we need to make sure we have a precise disk_i_size by
  	 * updating it as usual.
  	 *
  	 */
  	if (!ordered && disk_i_size > i_size) {
  		BTRFS_I(inode)->disk_i_size = orig_offset;
  		ret = 0;
  		goto out;
  	}
  
  	/*
  	 * if the disk i_size is already at the inode->i_size, or
  	 * this ordered extent is inside the disk i_size, we're done
  	 */
  	if (disk_i_size == i_size)
  		goto out;
  
  	/*
  	 * We still need to update disk_i_size if outstanding_isize is greater
  	 * than disk_i_size.
  	 */
  	if (offset <= disk_i_size &&
  	    (!ordered || ordered->outstanding_isize <= disk_i_size))
  		goto out;
  
  	/*
  	 * walk backward from this ordered extent to disk_i_size.
  	 * if we find an ordered extent then we can't update disk i_size
  	 * yet
  	 */
  	if (ordered) {
  		node = rb_prev(&ordered->rb_node);
  	} else {
  		prev = tree_search(tree, offset);
  		/*
  		 * we insert file extents without involving ordered struct,
  		 * so there should be no ordered struct cover this offset
  		 */
  		if (prev) {
  			test = rb_entry(prev, struct btrfs_ordered_extent,
  					rb_node);
  			BUG_ON(offset_in_entry(test, offset));
  		}
  		node = prev;
  	}
  	for (; node; node = rb_prev(node)) {
  		test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
  
  		/* We treat this entry as if it doesn't exist */
  		if (test_bit(BTRFS_ORDERED_UPDATED_ISIZE, &test->flags))
  			continue;
  
  		if (entry_end(test) <= disk_i_size)
  			break;
  		if (test->file_offset >= i_size)
  			break;
  
  		/*
  		 * We don't update disk_i_size now, so record this undealt
  		 * i_size. Or we will not know the real i_size.
  		 */
  		if (test->outstanding_isize < offset)
  			test->outstanding_isize = offset;
  		if (ordered &&
  		    ordered->outstanding_isize > test->outstanding_isize)
  			test->outstanding_isize = ordered->outstanding_isize;
  		goto out;
  	}
  	new_i_size = min_t(u64, offset, i_size);
  
  	/*
  	 * Some ordered extents may completed before the current one, and
  	 * we hold the real i_size in ->outstanding_isize.
  	 */
  	if (ordered && ordered->outstanding_isize > new_i_size)
  		new_i_size = min_t(u64, ordered->outstanding_isize, i_size);
  	BTRFS_I(inode)->disk_i_size = new_i_size;
  	ret = 0;
  out:
  	/*
  	 * We need to do this because we can't remove ordered extents until
  	 * after the i_disk_size has been updated and then the inode has been
  	 * updated to reflect the change, so we need to tell anybody who finds
  	 * this ordered extent that we've already done all the real work, we
  	 * just haven't completed all the other work.
  	 */
  	if (ordered)
  		set_bit(BTRFS_ORDERED_UPDATED_ISIZE, &ordered->flags);
  	spin_unlock_irq(&tree->lock);
  	return ret;
  }
  
  /*
   * search the ordered extents for one corresponding to 'offset' and
   * try to find a checksum.  This is used because we allow pages to
   * be reclaimed before their checksum is actually put into the btree
   */
  int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr,
  			   u32 *sum, int len)
  {
  	struct btrfs_ordered_sum *ordered_sum;
  	struct btrfs_ordered_extent *ordered;
  	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
  	unsigned long num_sectors;
  	unsigned long i;
  	u32 sectorsize = btrfs_inode_sectorsize(inode);
  	int index = 0;
  
  	ordered = btrfs_lookup_ordered_extent(inode, offset);
  	if (!ordered)
  		return 0;
  
  	spin_lock_irq(&tree->lock);
  	list_for_each_entry_reverse(ordered_sum, &ordered->list, list) {
  		if (disk_bytenr >= ordered_sum->bytenr &&
  		    disk_bytenr < ordered_sum->bytenr + ordered_sum->len) {
  			i = (disk_bytenr - ordered_sum->bytenr) >>
  			    inode->i_sb->s_blocksize_bits;
  			num_sectors = ordered_sum->len >>
  				      inode->i_sb->s_blocksize_bits;
  			num_sectors = min_t(int, len - index, num_sectors - i);
  			memcpy(sum + index, ordered_sum->sums + i,
  			       num_sectors);
  
  			index += (int)num_sectors;
  			if (index == len)
  				goto out;
  			disk_bytenr += num_sectors * sectorsize;
  		}
  	}
  out:
  	spin_unlock_irq(&tree->lock);
  	btrfs_put_ordered_extent(ordered);
  	return index;
  }
  
  int __init ordered_data_init(void)
  {
  	btrfs_ordered_extent_cache = kmem_cache_create("btrfs_ordered_extent",
  				     sizeof(struct btrfs_ordered_extent), 0,
  				     SLAB_MEM_SPREAD,
  				     NULL);
  	if (!btrfs_ordered_extent_cache)
  		return -ENOMEM;
  
  	return 0;
  }
  
  void __cold ordered_data_exit(void)
  {
  	kmem_cache_destroy(btrfs_ordered_extent_cache);
  }
  