Skip to content
Snippets Groups Projects
Select Git revision
  • 569f75bd02d20043c4baf9fc38d937f37e7572b0
  • vme-testing default
  • ci-test
  • master
  • remoteproc
  • am625-sk-ov5640
  • pcal6534-upstreaming
  • lps22df-upstreaming
  • msc-upstreaming
  • imx8mp
  • iio/noa1305
  • vme-next
  • vme-next-4.14-rc4
  • v4.14-rc4
  • v4.14-rc3
  • v4.14-rc2
  • v4.14-rc1
  • v4.13
  • vme-next-4.13-rc7
  • v4.13-rc7
  • v4.13-rc6
  • v4.13-rc5
  • v4.13-rc4
  • v4.13-rc3
  • v4.13-rc2
  • v4.13-rc1
  • v4.12
  • v4.12-rc7
  • v4.12-rc6
  • v4.12-rc5
  • v4.12-rc4
  • v4.12-rc3
32 results

irq_cpu.c

Blame
  • file.c 83.81 KiB
    /*
     * Copyright (C) 2007 Oracle.  All rights reserved.
     *
     * This program is free software; you can redistribute it and/or
     * modify it under the terms of the GNU General Public
     * License v2 as published by the Free Software Foundation.
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     * General Public License for more details.
     *
     * You should have received a copy of the GNU General Public
     * License along with this program; if not, write to the
     * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     * Boston, MA 021110-1307, USA.
     */
    
    #include <linux/fs.h>
    #include <linux/pagemap.h>
    #include <linux/highmem.h>
    #include <linux/time.h>
    #include <linux/init.h>
    #include <linux/string.h>
    #include <linux/backing-dev.h>
    #include <linux/mpage.h>
    #include <linux/falloc.h>
    #include <linux/swap.h>
    #include <linux/writeback.h>
    #include <linux/compat.h>
    #include <linux/slab.h>
    #include <linux/btrfs.h>
    #include <linux/uio.h>
    #include "ctree.h"
    #include "disk-io.h"
    #include "transaction.h"
    #include "btrfs_inode.h"
    #include "print-tree.h"
    #include "tree-log.h"
    #include "locking.h"
    #include "volumes.h"
    #include "qgroup.h"
    #include "compression.h"
    
    static struct kmem_cache *btrfs_inode_defrag_cachep;
    /*
     * when auto defrag is enabled we
     * queue up these defrag structs to remember which
     * inodes need defragging passes
     */
    struct inode_defrag {
    	struct rb_node rb_node;
    	/* objectid */
    	u64 ino;
    	/*
    	 * transid where the defrag was added, we search for
    	 * extents newer than this
    	 */
    	u64 transid;
    
    	/* root objectid */
    	u64 root;
    
    	/* last offset we were able to defrag */
    	u64 last_offset;
    
    	/* if we've wrapped around back to zero once already */
    	int cycled;
    };
    
    static int __compare_inode_defrag(struct inode_defrag *defrag1,
    				  struct inode_defrag *defrag2)
    {
    	if (defrag1->root > defrag2->root)
    		return 1;
    	else if (defrag1->root < defrag2->root)
    		return -1;
    	else if (defrag1->ino > defrag2->ino)
    		return 1;
    	else if (defrag1->ino < defrag2->ino)
    		return -1;
    	else
    		return 0;
    }
    
    /* pop a record for an inode into the defrag tree.  The lock
     * must be held already
     *
     * If you're inserting a record for an older transid than an
     * existing record, the transid already in the tree is lowered
     *
     * If an existing record is found the defrag item you
     * pass in is freed
     */
    static int __btrfs_add_inode_defrag(struct btrfs_inode *inode,
    				    struct inode_defrag *defrag)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	struct inode_defrag *entry;
    	struct rb_node **p;
    	struct rb_node *parent = NULL;
    	int ret;
    
    	p = &fs_info->defrag_inodes.rb_node;
    	while (*p) {
    		parent = *p;
    		entry = rb_entry(parent, struct inode_defrag, rb_node);
    
    		ret = __compare_inode_defrag(defrag, entry);
    		if (ret < 0)
    			p = &parent->rb_left;
    		else if (ret > 0)
    			p = &parent->rb_right;
    		else {
    			/* if we're reinserting an entry for
    			 * an old defrag run, make sure to
    			 * lower the transid of our existing record
    			 */
    			if (defrag->transid < entry->transid)
    				entry->transid = defrag->transid;
    			if (defrag->last_offset > entry->last_offset)
    				entry->last_offset = defrag->last_offset;
    			return -EEXIST;
    		}
    	}
    	set_bit(BTRFS_INODE_IN_DEFRAG, &inode->runtime_flags);
    	rb_link_node(&defrag->rb_node, parent, p);
    	rb_insert_color(&defrag->rb_node, &fs_info->defrag_inodes);
    	return 0;
    }
    
    static inline int __need_auto_defrag(struct btrfs_fs_info *fs_info)
    {
    	if (!btrfs_test_opt(fs_info, AUTO_DEFRAG))
    		return 0;
    
    	if (btrfs_fs_closing(fs_info))
    		return 0;
    
    	return 1;
    }
    
    /*
     * insert a defrag record for this inode if auto defrag is
     * enabled
     */
    int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
    			   struct btrfs_inode *inode)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	struct btrfs_root *root = inode->root;
    	struct inode_defrag *defrag;
    	u64 transid;
    	int ret;
    
    	if (!__need_auto_defrag(fs_info))
    		return 0;
    
    	if (test_bit(BTRFS_INODE_IN_DEFRAG, &inode->runtime_flags))
    		return 0;
    
    	if (trans)
    		transid = trans->transid;
    	else
    		transid = inode->root->last_trans;
    
    	defrag = kmem_cache_zalloc(btrfs_inode_defrag_cachep, GFP_NOFS);
    	if (!defrag)
    		return -ENOMEM;
    
    	defrag->ino = btrfs_ino(inode);
    	defrag->transid = transid;
    	defrag->root = root->root_key.objectid;
    
    	spin_lock(&fs_info->defrag_inodes_lock);
    	if (!test_bit(BTRFS_INODE_IN_DEFRAG, &inode->runtime_flags)) {
    		/*
    		 * If we set IN_DEFRAG flag and evict the inode from memory,
    		 * and then re-read this inode, this new inode doesn't have
    		 * IN_DEFRAG flag. At the case, we may find the existed defrag.
    		 */
    		ret = __btrfs_add_inode_defrag(inode, defrag);
    		if (ret)
    			kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    	} else {
    		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    	}
    	spin_unlock(&fs_info->defrag_inodes_lock);
    	return 0;
    }
    
    /*
     * Requeue the defrag object. If there is a defrag object that points to
     * the same inode in the tree, we will merge them together (by
     * __btrfs_add_inode_defrag()) and free the one that we want to requeue.
     */
    static void btrfs_requeue_inode_defrag(struct btrfs_inode *inode,
    				       struct inode_defrag *defrag)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	int ret;
    
    	if (!__need_auto_defrag(fs_info))
    		goto out;
    
    	/*
    	 * Here we don't check the IN_DEFRAG flag, because we need merge
    	 * them together.
    	 */
    	spin_lock(&fs_info->defrag_inodes_lock);
    	ret = __btrfs_add_inode_defrag(inode, defrag);
    	spin_unlock(&fs_info->defrag_inodes_lock);
    	if (ret)
    		goto out;
    	return;
    out:
    	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    }
    
    /*
     * pick the defragable inode that we want, if it doesn't exist, we will get
     * the next one.
     */
    static struct inode_defrag *
    btrfs_pick_defrag_inode(struct btrfs_fs_info *fs_info, u64 root, u64 ino)
    {
    	struct inode_defrag *entry = NULL;
    	struct inode_defrag tmp;
    	struct rb_node *p;
    	struct rb_node *parent = NULL;
    	int ret;
    
    	tmp.ino = ino;
    	tmp.root = root;
    
    	spin_lock(&fs_info->defrag_inodes_lock);
    	p = fs_info->defrag_inodes.rb_node;
    	while (p) {
    		parent = p;
    		entry = rb_entry(parent, struct inode_defrag, rb_node);
    
    		ret = __compare_inode_defrag(&tmp, entry);
    		if (ret < 0)
    			p = parent->rb_left;
    		else if (ret > 0)
    			p = parent->rb_right;
    		else
    			goto out;
    	}
    
    	if (parent && __compare_inode_defrag(&tmp, entry) > 0) {
    		parent = rb_next(parent);
    		if (parent)
    			entry = rb_entry(parent, struct inode_defrag, rb_node);
    		else
    			entry = NULL;
    	}
    out:
    	if (entry)
    		rb_erase(parent, &fs_info->defrag_inodes);
    	spin_unlock(&fs_info->defrag_inodes_lock);
    	return entry;
    }
    
    void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info)
    {
    	struct inode_defrag *defrag;
    	struct rb_node *node;
    
    	spin_lock(&fs_info->defrag_inodes_lock);
    	node = rb_first(&fs_info->defrag_inodes);
    	while (node) {
    		rb_erase(node, &fs_info->defrag_inodes);
    		defrag = rb_entry(node, struct inode_defrag, rb_node);
    		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    
    		cond_resched_lock(&fs_info->defrag_inodes_lock);
    
    		node = rb_first(&fs_info->defrag_inodes);
    	}
    	spin_unlock(&fs_info->defrag_inodes_lock);
    }
    
    #define BTRFS_DEFRAG_BATCH	1024
    
    static int __btrfs_run_defrag_inode(struct btrfs_fs_info *fs_info,
    				    struct inode_defrag *defrag)
    {
    	struct btrfs_root *inode_root;
    	struct inode *inode;
    	struct btrfs_key key;
    	struct btrfs_ioctl_defrag_range_args range;
    	int num_defrag;
    	int index;
    	int ret;
    
    	/* get the inode */
    	key.objectid = defrag->root;
    	key.type = BTRFS_ROOT_ITEM_KEY;
    	key.offset = (u64)-1;
    
    	index = srcu_read_lock(&fs_info->subvol_srcu);
    
    	inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
    	if (IS_ERR(inode_root)) {
    		ret = PTR_ERR(inode_root);
    		goto cleanup;
    	}
    
    	key.objectid = defrag->ino;
    	key.type = BTRFS_INODE_ITEM_KEY;
    	key.offset = 0;
    	inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
    	if (IS_ERR(inode)) {
    		ret = PTR_ERR(inode);
    		goto cleanup;
    	}
    	srcu_read_unlock(&fs_info->subvol_srcu, index);
    
    	/* do a chunk of defrag */
    	clear_bit(BTRFS_INODE_IN_DEFRAG, &BTRFS_I(inode)->runtime_flags);
    	memset(&range, 0, sizeof(range));
    	range.len = (u64)-1;
    	range.start = defrag->last_offset;
    
    	sb_start_write(fs_info->sb);
    	num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
    				       BTRFS_DEFRAG_BATCH);
    	sb_end_write(fs_info->sb);
    	/*
    	 * if we filled the whole defrag batch, there
    	 * must be more work to do.  Queue this defrag
    	 * again
    	 */
    	if (num_defrag == BTRFS_DEFRAG_BATCH) {
    		defrag->last_offset = range.start;
    		btrfs_requeue_inode_defrag(BTRFS_I(inode), defrag);
    	} else if (defrag->last_offset && !defrag->cycled) {
    		/*
    		 * we didn't fill our defrag batch, but
    		 * we didn't start at zero.  Make sure we loop
    		 * around to the start of the file.
    		 */
    		defrag->last_offset = 0;
    		defrag->cycled = 1;
    		btrfs_requeue_inode_defrag(BTRFS_I(inode), defrag);
    	} else {
    		kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    	}
    
    	iput(inode);
    	return 0;
    cleanup:
    	srcu_read_unlock(&fs_info->subvol_srcu, index);
    	kmem_cache_free(btrfs_inode_defrag_cachep, defrag);
    	return ret;
    }
    
    /*
     * run through the list of inodes in the FS that need
     * defragging
     */
    int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
    {
    	struct inode_defrag *defrag;
    	u64 first_ino = 0;
    	u64 root_objectid = 0;
    
    	atomic_inc(&fs_info->defrag_running);
    	while (1) {
    		/* Pause the auto defragger. */
    		if (test_bit(BTRFS_FS_STATE_REMOUNTING,
    			     &fs_info->fs_state))
    			break;
    
    		if (!__need_auto_defrag(fs_info))
    			break;
    
    		/* find an inode to defrag */
    		defrag = btrfs_pick_defrag_inode(fs_info, root_objectid,
    						 first_ino);
    		if (!defrag) {
    			if (root_objectid || first_ino) {
    				root_objectid = 0;
    				first_ino = 0;
    				continue;
    			} else {
    				break;
    			}
    		}
    
    		first_ino = defrag->ino + 1;
    		root_objectid = defrag->root;
    
    		__btrfs_run_defrag_inode(fs_info, defrag);
    	}
    	atomic_dec(&fs_info->defrag_running);
    
    	/*
    	 * during unmount, we use the transaction_wait queue to
    	 * wait for the defragger to stop
    	 */
    	wake_up(&fs_info->transaction_wait);
    	return 0;
    }
    
    /* simple helper to fault in pages and copy.  This should go away
     * and be replaced with calls into generic code.
     */
    static noinline int btrfs_copy_from_user(loff_t pos, size_t write_bytes,
    					 struct page **prepared_pages,
    					 struct iov_iter *i)
    {
    	size_t copied = 0;
    	size_t total_copied = 0;
    	int pg = 0;
    	int offset = pos & (PAGE_SIZE - 1);
    
    	while (write_bytes > 0) {
    		size_t count = min_t(size_t,
    				     PAGE_SIZE - offset, write_bytes);
    		struct page *page = prepared_pages[pg];
    		/*
    		 * Copy data from userspace to the current page
    		 */
    		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
    
    		/* Flush processor's dcache for this page */
    		flush_dcache_page(page);
    
    		/*
    		 * if we get a partial write, we can end up with
    		 * partially up to date pages.  These add
    		 * a lot of complexity, so make sure they don't
    		 * happen by forcing this copy to be retried.
    		 *
    		 * The rest of the btrfs_file_write code will fall
    		 * back to page at a time copies after we return 0.
    		 */
    		if (!PageUptodate(page) && copied < count)
    			copied = 0;
    
    		iov_iter_advance(i, copied);
    		write_bytes -= copied;
    		total_copied += copied;
    
    		/* Return to btrfs_file_write_iter to fault page */
    		if (unlikely(copied == 0))
    			break;
    
    		if (copied < PAGE_SIZE - offset) {
    			offset += copied;
    		} else {
    			pg++;
    			offset = 0;
    		}
    	}
    	return total_copied;
    }
    
    /*
     * unlocks pages after btrfs_file_write is done with them
     */
    static void btrfs_drop_pages(struct page **pages, size_t num_pages)
    {
    	size_t i;
    	for (i = 0; i < num_pages; i++) {
    		/* page checked is some magic around finding pages that
    		 * have been modified without going through btrfs_set_page_dirty
    		 * clear it here. There should be no need to mark the pages
    		 * accessed as prepare_pages should have marked them accessed
    		 * in prepare_pages via find_or_create_page()
    		 */
    		ClearPageChecked(pages[i]);
    		unlock_page(pages[i]);
    		put_page(pages[i]);
    	}
    }
    
    /*
     * after copy_from_user, pages need to be dirtied and we need to make
     * sure holes are created between the current EOF and the start of
     * any next extents (if required).
     *
     * this also makes the decision about creating an inline extent vs
     * doing real data extents, marking pages dirty and delalloc as required.
     */
    int btrfs_dirty_pages(struct inode *inode, struct page **pages,
    		      size_t num_pages, loff_t pos, size_t write_bytes,
    		      struct extent_state **cached)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	int err = 0;
    	int i;
    	u64 num_bytes;
    	u64 start_pos;
    	u64 end_of_last_block;
    	u64 end_pos = pos + write_bytes;
    	loff_t isize = i_size_read(inode);
    
    	start_pos = pos & ~((u64) fs_info->sectorsize - 1);
    	num_bytes = round_up(write_bytes + pos - start_pos,
    			     fs_info->sectorsize);
    
    	end_of_last_block = start_pos + num_bytes - 1;
    	err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block,
    					cached, 0);
    	if (err)
    		return err;
    
    	for (i = 0; i < num_pages; i++) {
    		struct page *p = pages[i];
    		SetPageUptodate(p);
    		ClearPageChecked(p);
    		set_page_dirty(p);
    	}
    
    	/*
    	 * we've only changed i_size in ram, and we haven't updated
    	 * the disk i_size.  There is no need to log the inode
    	 * at this time.
    	 */
    	if (end_pos > isize)
    		i_size_write(inode, end_pos);
    	return 0;
    }
    
    /*
     * this drops all the extents in the cache that intersect the range
     * [start, end].  Existing extents are split as required.
     */
    void btrfs_drop_extent_cache(struct btrfs_inode *inode, u64 start, u64 end,
    			     int skip_pinned)
    {
    	struct extent_map *em;
    	struct extent_map *split = NULL;
    	struct extent_map *split2 = NULL;
    	struct extent_map_tree *em_tree = &inode->extent_tree;
    	u64 len = end - start + 1;
    	u64 gen;
    	int ret;
    	int testend = 1;
    	unsigned long flags;
    	int compressed = 0;
    	bool modified;
    
    	WARN_ON(end < start);
    	if (end == (u64)-1) {
    		len = (u64)-1;
    		testend = 0;
    	}
    	while (1) {
    		int no_splits = 0;
    
    		modified = false;
    		if (!split)
    			split = alloc_extent_map();
    		if (!split2)
    			split2 = alloc_extent_map();
    		if (!split || !split2)
    			no_splits = 1;
    
    		write_lock(&em_tree->lock);
    		em = lookup_extent_mapping(em_tree, start, len);
    		if (!em) {
    			write_unlock(&em_tree->lock);
    			break;
    		}
    		flags = em->flags;
    		gen = em->generation;
    		if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {
    			if (testend && em->start + em->len >= start + len) {
    				free_extent_map(em);
    				write_unlock(&em_tree->lock);
    				break;
    			}
    			start = em->start + em->len;
    			if (testend)
    				len = start + len - (em->start + em->len);
    			free_extent_map(em);
    			write_unlock(&em_tree->lock);
    			continue;
    		}
    		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
    		clear_bit(EXTENT_FLAG_PINNED, &em->flags);
    		clear_bit(EXTENT_FLAG_LOGGING, &flags);
    		modified = !list_empty(&em->list);
    		if (no_splits)
    			goto next;
    
    		if (em->start < start) {
    			split->start = em->start;
    			split->len = start - em->start;
    
    			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
    				split->orig_start = em->orig_start;
    				split->block_start = em->block_start;
    
    				if (compressed)
    					split->block_len = em->block_len;
    				else
    					split->block_len = split->len;
    				split->orig_block_len = max(split->block_len,
    						em->orig_block_len);
    				split->ram_bytes = em->ram_bytes;
    			} else {
    				split->orig_start = split->start;
    				split->block_len = 0;
    				split->block_start = em->block_start;
    				split->orig_block_len = 0;
    				split->ram_bytes = split->len;
    			}
    
    			split->generation = gen;
    			split->bdev = em->bdev;
    			split->flags = flags;
    			split->compress_type = em->compress_type;
    			replace_extent_mapping(em_tree, em, split, modified);
    			free_extent_map(split);
    			split = split2;
    			split2 = NULL;
    		}
    		if (testend && em->start + em->len > start + len) {
    			u64 diff = start + len - em->start;
    
    			split->start = start + len;
    			split->len = em->start + em->len - (start + len);
    			split->bdev = em->bdev;
    			split->flags = flags;
    			split->compress_type = em->compress_type;
    			split->generation = gen;
    
    			if (em->block_start < EXTENT_MAP_LAST_BYTE) {
    				split->orig_block_len = max(em->block_len,
    						    em->orig_block_len);
    
    				split->ram_bytes = em->ram_bytes;
    				if (compressed) {
    					split->block_len = em->block_len;
    					split->block_start = em->block_start;
    					split->orig_start = em->orig_start;
    				} else {
    					split->block_len = split->len;
    					split->block_start = em->block_start
    						+ diff;
    					split->orig_start = em->orig_start;
    				}
    			} else {
    				split->ram_bytes = split->len;
    				split->orig_start = split->start;
    				split->block_len = 0;
    				split->block_start = em->block_start;
    				split->orig_block_len = 0;
    			}
    
    			if (extent_map_in_tree(em)) {
    				replace_extent_mapping(em_tree, em, split,
    						       modified);
    			} else {
    				ret = add_extent_mapping(em_tree, split,
    							 modified);
    				ASSERT(ret == 0); /* Logic error */
    			}
    			free_extent_map(split);
    			split = NULL;
    		}
    next:
    		if (extent_map_in_tree(em))
    			remove_extent_mapping(em_tree, em);
    		write_unlock(&em_tree->lock);
    
    		/* once for us */
    		free_extent_map(em);
    		/* once for the tree*/
    		free_extent_map(em);
    	}
    	if (split)
    		free_extent_map(split);
    	if (split2)
    		free_extent_map(split2);
    }
    
    /*
     * this is very complex, but the basic idea is to drop all extents
     * in the range start - end.  hint_block is filled in with a block number
     * that would be a good hint to the block allocator for this file.
     *
     * If an extent intersects the range but is not entirely inside the range
     * it is either truncated or split.  Anything entirely inside the range
     * is deleted from the tree.
     */
    int __btrfs_drop_extents(struct btrfs_trans_handle *trans,
    			 struct btrfs_root *root, struct inode *inode,
    			 struct btrfs_path *path, u64 start, u64 end,
    			 u64 *drop_end, int drop_cache,
    			 int replace_extent,
    			 u32 extent_item_size,
    			 int *key_inserted)
    {
    	struct btrfs_fs_info *fs_info = root->fs_info;
    	struct extent_buffer *leaf;
    	struct btrfs_file_extent_item *fi;
    	struct btrfs_key key;
    	struct btrfs_key new_key;
    	u64 ino = btrfs_ino(BTRFS_I(inode));
    	u64 search_start = start;
    	u64 disk_bytenr = 0;
    	u64 num_bytes = 0;
    	u64 extent_offset = 0;
    	u64 extent_end = 0;
    	u64 last_end = start;
    	int del_nr = 0;
    	int del_slot = 0;
    	int extent_type;
    	int recow;
    	int ret;
    	int modify_tree = -1;
    	int update_refs;
    	int found = 0;
    	int leafs_visited = 0;
    
    	if (drop_cache)
    		btrfs_drop_extent_cache(BTRFS_I(inode), start, end - 1, 0);
    
    	if (start >= BTRFS_I(inode)->disk_i_size && !replace_extent)
    		modify_tree = 0;
    
    	update_refs = (test_bit(BTRFS_ROOT_REF_COWS, &root->state) ||
    		       root == fs_info->tree_root);
    	while (1) {
    		recow = 0;
    		ret = btrfs_lookup_file_extent(trans, root, path, ino,
    					       search_start, modify_tree);
    		if (ret < 0)
    			break;
    		if (ret > 0 && path->slots[0] > 0 && search_start == start) {
    			leaf = path->nodes[0];
    			btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
    			if (key.objectid == ino &&
    			    key.type == BTRFS_EXTENT_DATA_KEY)
    				path->slots[0]--;
    		}
    		ret = 0;
    		leafs_visited++;
    next_slot:
    		leaf = path->nodes[0];
    		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
    			BUG_ON(del_nr > 0);
    			ret = btrfs_next_leaf(root, path);
    			if (ret < 0)
    				break;
    			if (ret > 0) {
    				ret = 0;
    				break;
    			}
    			leafs_visited++;
    			leaf = path->nodes[0];
    			recow = 1;
    		}
    
    		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
    
    		if (key.objectid > ino)
    			break;
    		if (WARN_ON_ONCE(key.objectid < ino) ||
    		    key.type < BTRFS_EXTENT_DATA_KEY) {
    			ASSERT(del_nr == 0);
    			path->slots[0]++;
    			goto next_slot;
    		}
    		if (key.type > BTRFS_EXTENT_DATA_KEY || key.offset >= end)
    			break;
    
    		fi = btrfs_item_ptr(leaf, path->slots[0],
    				    struct btrfs_file_extent_item);
    		extent_type = btrfs_file_extent_type(leaf, fi);
    
    		if (extent_type == BTRFS_FILE_EXTENT_REG ||
    		    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
    			disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
    			num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
    			extent_offset = btrfs_file_extent_offset(leaf, fi);
    			extent_end = key.offset +
    				btrfs_file_extent_num_bytes(leaf, fi);
    		} else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
    			extent_end = key.offset +
    				btrfs_file_extent_inline_len(leaf,
    						     path->slots[0], fi);
    		} else {
    			/* can't happen */
    			BUG();
    		}
    
    		/*
    		 * Don't skip extent items representing 0 byte lengths. They
    		 * used to be created (bug) if while punching holes we hit
    		 * -ENOSPC condition. So if we find one here, just ensure we
    		 * delete it, otherwise we would insert a new file extent item
    		 * with the same key (offset) as that 0 bytes length file
    		 * extent item in the call to setup_items_for_insert() later
    		 * in this function.
    		 */
    		if (extent_end == key.offset && extent_end >= search_start) {
    			last_end = extent_end;
    			goto delete_extent_item;
    		}
    
    		if (extent_end <= search_start) {
    			path->slots[0]++;
    			goto next_slot;
    		}
    
    		found = 1;
    		search_start = max(key.offset, start);
    		if (recow || !modify_tree) {
    			modify_tree = -1;
    			btrfs_release_path(path);
    			continue;
    		}
    
    		/*
    		 *     | - range to drop - |
    		 *  | -------- extent -------- |
    		 */
    		if (start > key.offset && end < extent_end) {
    			BUG_ON(del_nr > 0);
    			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
    				ret = -EOPNOTSUPP;
    				break;
    			}
    
    			memcpy(&new_key, &key, sizeof(new_key));
    			new_key.offset = start;
    			ret = btrfs_duplicate_item(trans, root, path,
    						   &new_key);
    			if (ret == -EAGAIN) {
    				btrfs_release_path(path);
    				continue;
    			}
    			if (ret < 0)
    				break;
    
    			leaf = path->nodes[0];
    			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
    					    struct btrfs_file_extent_item);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							start - key.offset);
    
    			fi = btrfs_item_ptr(leaf, path->slots[0],
    					    struct btrfs_file_extent_item);
    
    			extent_offset += start - key.offset;
    			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							extent_end - start);
    			btrfs_mark_buffer_dirty(leaf);
    
    			if (update_refs && disk_bytenr > 0) {
    				ret = btrfs_inc_extent_ref(trans, fs_info,
    						disk_bytenr, num_bytes, 0,
    						root->root_key.objectid,
    						new_key.objectid,
    						start - extent_offset);
    				BUG_ON(ret); /* -ENOMEM */
    			}
    			key.offset = start;
    		}
    		/*
    		 * From here on out we will have actually dropped something, so
    		 * last_end can be updated.
    		 */
    		last_end = extent_end;
    
    		/*
    		 *  | ---- range to drop ----- |
    		 *      | -------- extent -------- |
    		 */
    		if (start <= key.offset && end < extent_end) {
    			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
    				ret = -EOPNOTSUPP;
    				break;
    			}
    
    			memcpy(&new_key, &key, sizeof(new_key));
    			new_key.offset = end;
    			btrfs_set_item_key_safe(fs_info, path, &new_key);
    
    			extent_offset += end - key.offset;
    			btrfs_set_file_extent_offset(leaf, fi, extent_offset);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							extent_end - end);
    			btrfs_mark_buffer_dirty(leaf);
    			if (update_refs && disk_bytenr > 0)
    				inode_sub_bytes(inode, end - key.offset);
    			break;
    		}
    
    		search_start = extent_end;
    		/*
    		 *       | ---- range to drop ----- |
    		 *  | -------- extent -------- |
    		 */
    		if (start > key.offset && end >= extent_end) {
    			BUG_ON(del_nr > 0);
    			if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
    				ret = -EOPNOTSUPP;
    				break;
    			}
    
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							start - key.offset);
    			btrfs_mark_buffer_dirty(leaf);
    			if (update_refs && disk_bytenr > 0)
    				inode_sub_bytes(inode, extent_end - start);
    			if (end == extent_end)
    				break;
    
    			path->slots[0]++;
    			goto next_slot;
    		}
    
    		/*
    		 *  | ---- range to drop ----- |
    		 *    | ------ extent ------ |
    		 */
    		if (start <= key.offset && end >= extent_end) {
    delete_extent_item:
    			if (del_nr == 0) {
    				del_slot = path->slots[0];
    				del_nr = 1;
    			} else {
    				BUG_ON(del_slot + del_nr != path->slots[0]);
    				del_nr++;
    			}
    
    			if (update_refs &&
    			    extent_type == BTRFS_FILE_EXTENT_INLINE) {
    				inode_sub_bytes(inode,
    						extent_end - key.offset);
    				extent_end = ALIGN(extent_end,
    						   fs_info->sectorsize);
    			} else if (update_refs && disk_bytenr > 0) {
    				ret = btrfs_free_extent(trans, fs_info,
    						disk_bytenr, num_bytes, 0,
    						root->root_key.objectid,
    						key.objectid, key.offset -
    						extent_offset);
    				BUG_ON(ret); /* -ENOMEM */
    				inode_sub_bytes(inode,
    						extent_end - key.offset);
    			}
    
    			if (end == extent_end)
    				break;
    
    			if (path->slots[0] + 1 < btrfs_header_nritems(leaf)) {
    				path->slots[0]++;
    				goto next_slot;
    			}
    
    			ret = btrfs_del_items(trans, root, path, del_slot,
    					      del_nr);
    			if (ret) {
    				btrfs_abort_transaction(trans, ret);
    				break;
    			}
    
    			del_nr = 0;
    			del_slot = 0;
    
    			btrfs_release_path(path);
    			continue;
    		}
    
    		BUG_ON(1);
    	}
    
    	if (!ret && del_nr > 0) {
    		/*
    		 * Set path->slots[0] to first slot, so that after the delete
    		 * if items are move off from our leaf to its immediate left or
    		 * right neighbor leafs, we end up with a correct and adjusted
    		 * path->slots[0] for our insertion (if replace_extent != 0).
    		 */
    		path->slots[0] = del_slot;
    		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
    		if (ret)
    			btrfs_abort_transaction(trans, ret);
    	}
    
    	leaf = path->nodes[0];
    	/*
    	 * If btrfs_del_items() was called, it might have deleted a leaf, in
    	 * which case it unlocked our path, so check path->locks[0] matches a
    	 * write lock.
    	 */
    	if (!ret && replace_extent && leafs_visited == 1 &&
    	    (path->locks[0] == BTRFS_WRITE_LOCK_BLOCKING ||
    	     path->locks[0] == BTRFS_WRITE_LOCK) &&
    	    btrfs_leaf_free_space(fs_info, leaf) >=
    	    sizeof(struct btrfs_item) + extent_item_size) {
    
    		key.objectid = ino;
    		key.type = BTRFS_EXTENT_DATA_KEY;
    		key.offset = start;
    		if (!del_nr && path->slots[0] < btrfs_header_nritems(leaf)) {
    			struct btrfs_key slot_key;
    
    			btrfs_item_key_to_cpu(leaf, &slot_key, path->slots[0]);
    			if (btrfs_comp_cpu_keys(&key, &slot_key) > 0)
    				path->slots[0]++;
    		}
    		setup_items_for_insert(root, path, &key,
    				       &extent_item_size,
    				       extent_item_size,
    				       sizeof(struct btrfs_item) +
    				       extent_item_size, 1);
    		*key_inserted = 1;
    	}
    
    	if (!replace_extent || !(*key_inserted))
    		btrfs_release_path(path);
    	if (drop_end)
    		*drop_end = found ? min(end, last_end) : end;
    	return ret;
    }
    
    int btrfs_drop_extents(struct btrfs_trans_handle *trans,
    		       struct btrfs_root *root, struct inode *inode, u64 start,
    		       u64 end, int drop_cache)
    {
    	struct btrfs_path *path;
    	int ret;
    
    	path = btrfs_alloc_path();
    	if (!path)
    		return -ENOMEM;
    	ret = __btrfs_drop_extents(trans, root, inode, path, start, end, NULL,
    				   drop_cache, 0, 0, NULL);
    	btrfs_free_path(path);
    	return ret;
    }
    
    static int extent_mergeable(struct extent_buffer *leaf, int slot,
    			    u64 objectid, u64 bytenr, u64 orig_offset,
    			    u64 *start, u64 *end)
    {
    	struct btrfs_file_extent_item *fi;
    	struct btrfs_key key;
    	u64 extent_end;
    
    	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
    		return 0;
    
    	btrfs_item_key_to_cpu(leaf, &key, slot);
    	if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
    		return 0;
    
    	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
    	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
    	    btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||
    	    btrfs_file_extent_offset(leaf, fi) != key.offset - orig_offset ||
    	    btrfs_file_extent_compression(leaf, fi) ||
    	    btrfs_file_extent_encryption(leaf, fi) ||
    	    btrfs_file_extent_other_encoding(leaf, fi))
    		return 0;
    
    	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
    	if ((*start && *start != key.offset) || (*end && *end != extent_end))
    		return 0;
    
    	*start = key.offset;
    	*end = extent_end;
    	return 1;
    }
    
    /*
     * Mark extent in the range start - end as written.
     *
     * This changes extent type from 'pre-allocated' to 'regular'. If only
     * part of extent is marked as written, the extent will be split into
     * two or three.
     */
    int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
    			      struct btrfs_inode *inode, u64 start, u64 end)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	struct btrfs_root *root = inode->root;
    	struct extent_buffer *leaf;
    	struct btrfs_path *path;
    	struct btrfs_file_extent_item *fi;
    	struct btrfs_key key;
    	struct btrfs_key new_key;
    	u64 bytenr;
    	u64 num_bytes;
    	u64 extent_end;
    	u64 orig_offset;
    	u64 other_start;
    	u64 other_end;
    	u64 split;
    	int del_nr = 0;
    	int del_slot = 0;
    	int recow;
    	int ret;
    	u64 ino = btrfs_ino(inode);
    
    	path = btrfs_alloc_path();
    	if (!path)
    		return -ENOMEM;
    again:
    	recow = 0;
    	split = start;
    	key.objectid = ino;
    	key.type = BTRFS_EXTENT_DATA_KEY;
    	key.offset = split;
    
    	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
    	if (ret < 0)
    		goto out;
    	if (ret > 0 && path->slots[0] > 0)
    		path->slots[0]--;
    
    	leaf = path->nodes[0];
    	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
    	if (key.objectid != ino ||
    	    key.type != BTRFS_EXTENT_DATA_KEY) {
    		ret = -EINVAL;
    		btrfs_abort_transaction(trans, ret);
    		goto out;
    	}
    	fi = btrfs_item_ptr(leaf, path->slots[0],
    			    struct btrfs_file_extent_item);
    	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_PREALLOC) {
    		ret = -EINVAL;
    		btrfs_abort_transaction(trans, ret);
    		goto out;
    	}
    	extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
    	if (key.offset > start || extent_end < end) {
    		ret = -EINVAL;
    		btrfs_abort_transaction(trans, ret);
    		goto out;
    	}
    
    	bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
    	num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
    	orig_offset = key.offset - btrfs_file_extent_offset(leaf, fi);
    	memcpy(&new_key, &key, sizeof(new_key));
    
    	if (start == key.offset && end < extent_end) {
    		other_start = 0;
    		other_end = start;
    		if (extent_mergeable(leaf, path->slots[0] - 1,
    				     ino, bytenr, orig_offset,
    				     &other_start, &other_end)) {
    			new_key.offset = end;
    			btrfs_set_item_key_safe(fs_info, path, &new_key);
    			fi = btrfs_item_ptr(leaf, path->slots[0],
    					    struct btrfs_file_extent_item);
    			btrfs_set_file_extent_generation(leaf, fi,
    							 trans->transid);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							extent_end - end);
    			btrfs_set_file_extent_offset(leaf, fi,
    						     end - orig_offset);
    			fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
    					    struct btrfs_file_extent_item);
    			btrfs_set_file_extent_generation(leaf, fi,
    							 trans->transid);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							end - other_start);
    			btrfs_mark_buffer_dirty(leaf);
    			goto out;
    		}
    	}
    
    	if (start > key.offset && end == extent_end) {
    		other_start = end;
    		other_end = 0;
    		if (extent_mergeable(leaf, path->slots[0] + 1,
    				     ino, bytenr, orig_offset,
    				     &other_start, &other_end)) {
    			fi = btrfs_item_ptr(leaf, path->slots[0],
    					    struct btrfs_file_extent_item);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							start - key.offset);
    			btrfs_set_file_extent_generation(leaf, fi,
    							 trans->transid);
    			path->slots[0]++;
    			new_key.offset = start;
    			btrfs_set_item_key_safe(fs_info, path, &new_key);
    
    			fi = btrfs_item_ptr(leaf, path->slots[0],
    					    struct btrfs_file_extent_item);
    			btrfs_set_file_extent_generation(leaf, fi,
    							 trans->transid);
    			btrfs_set_file_extent_num_bytes(leaf, fi,
    							other_end - start);
    			btrfs_set_file_extent_offset(leaf, fi,
    						     start - orig_offset);
    			btrfs_mark_buffer_dirty(leaf);
    			goto out;
    		}
    	}
    
    	while (start > key.offset || end < extent_end) {
    		if (key.offset == start)
    			split = end;
    
    		new_key.offset = split;
    		ret = btrfs_duplicate_item(trans, root, path, &new_key);
    		if (ret == -EAGAIN) {
    			btrfs_release_path(path);
    			goto again;
    		}
    		if (ret < 0) {
    			btrfs_abort_transaction(trans, ret);
    			goto out;
    		}
    
    		leaf = path->nodes[0];
    		fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
    				    struct btrfs_file_extent_item);
    		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
    		btrfs_set_file_extent_num_bytes(leaf, fi,
    						split - key.offset);
    
    		fi = btrfs_item_ptr(leaf, path->slots[0],
    				    struct btrfs_file_extent_item);
    
    		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
    		btrfs_set_file_extent_offset(leaf, fi, split - orig_offset);
    		btrfs_set_file_extent_num_bytes(leaf, fi,
    						extent_end - split);
    		btrfs_mark_buffer_dirty(leaf);
    
    		ret = btrfs_inc_extent_ref(trans, fs_info, bytenr, num_bytes,
    					   0, root->root_key.objectid,
    					   ino, orig_offset);
    		if (ret) {
    			btrfs_abort_transaction(trans, ret);
    			goto out;
    		}
    
    		if (split == start) {
    			key.offset = start;
    		} else {
    			if (start != key.offset) {
    				ret = -EINVAL;
    				btrfs_abort_transaction(trans, ret);
    				goto out;
    			}
    			path->slots[0]--;
    			extent_end = end;
    		}
    		recow = 1;
    	}
    
    	other_start = end;
    	other_end = 0;
    	if (extent_mergeable(leaf, path->slots[0] + 1,
    			     ino, bytenr, orig_offset,
    			     &other_start, &other_end)) {
    		if (recow) {
    			btrfs_release_path(path);
    			goto again;
    		}
    		extent_end = other_end;
    		del_slot = path->slots[0] + 1;
    		del_nr++;
    		ret = btrfs_free_extent(trans, fs_info, bytenr, num_bytes,
    					0, root->root_key.objectid,
    					ino, orig_offset);
    		if (ret) {
    			btrfs_abort_transaction(trans, ret);
    			goto out;
    		}
    	}
    	other_start = 0;
    	other_end = start;
    	if (extent_mergeable(leaf, path->slots[0] - 1,
    			     ino, bytenr, orig_offset,
    			     &other_start, &other_end)) {
    		if (recow) {
    			btrfs_release_path(path);
    			goto again;
    		}
    		key.offset = other_start;
    		del_slot = path->slots[0];
    		del_nr++;
    		ret = btrfs_free_extent(trans, fs_info, bytenr, num_bytes,
    					0, root->root_key.objectid,
    					ino, orig_offset);
    		if (ret) {
    			btrfs_abort_transaction(trans, ret);
    			goto out;
    		}
    	}
    	if (del_nr == 0) {
    		fi = btrfs_item_ptr(leaf, path->slots[0],
    			   struct btrfs_file_extent_item);
    		btrfs_set_file_extent_type(leaf, fi,
    					   BTRFS_FILE_EXTENT_REG);
    		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
    		btrfs_mark_buffer_dirty(leaf);
    	} else {
    		fi = btrfs_item_ptr(leaf, del_slot - 1,
    			   struct btrfs_file_extent_item);
    		btrfs_set_file_extent_type(leaf, fi,
    					   BTRFS_FILE_EXTENT_REG);
    		btrfs_set_file_extent_generation(leaf, fi, trans->transid);
    		btrfs_set_file_extent_num_bytes(leaf, fi,
    						extent_end - key.offset);
    		btrfs_mark_buffer_dirty(leaf);
    
    		ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
    		if (ret < 0) {
    			btrfs_abort_transaction(trans, ret);
    			goto out;
    		}
    	}
    out:
    	btrfs_free_path(path);
    	return 0;
    }
    
    /*
     * on error we return an unlocked page and the error value
     * on success we return a locked page and 0
     */
    static int prepare_uptodate_page(struct inode *inode,
    				 struct page *page, u64 pos,
    				 bool force_uptodate)
    {
    	int ret = 0;
    
    	if (((pos & (PAGE_SIZE - 1)) || force_uptodate) &&
    	    !PageUptodate(page)) {
    		ret = btrfs_readpage(NULL, page);
    		if (ret)
    			return ret;
    		lock_page(page);
    		if (!PageUptodate(page)) {
    			unlock_page(page);
    			return -EIO;
    		}
    		if (page->mapping != inode->i_mapping) {
    			unlock_page(page);
    			return -EAGAIN;
    		}
    	}
    	return 0;
    }
    
    /*
     * this just gets pages into the page cache and locks them down.
     */
    static noinline int prepare_pages(struct inode *inode, struct page **pages,
    				  size_t num_pages, loff_t pos,
    				  size_t write_bytes, bool force_uptodate)
    {
    	int i;
    	unsigned long index = pos >> PAGE_SHIFT;
    	gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
    	int err = 0;
    	int faili;
    
    	for (i = 0; i < num_pages; i++) {
    again:
    		pages[i] = find_or_create_page(inode->i_mapping, index + i,
    					       mask | __GFP_WRITE);
    		if (!pages[i]) {
    			faili = i - 1;
    			err = -ENOMEM;
    			goto fail;
    		}
    
    		if (i == 0)
    			err = prepare_uptodate_page(inode, pages[i], pos,
    						    force_uptodate);
    		if (!err && i == num_pages - 1)
    			err = prepare_uptodate_page(inode, pages[i],
    						    pos + write_bytes, false);
    		if (err) {
    			put_page(pages[i]);
    			if (err == -EAGAIN) {
    				err = 0;
    				goto again;
    			}
    			faili = i - 1;
    			goto fail;
    		}
    		wait_on_page_writeback(pages[i]);
    	}
    
    	return 0;
    fail:
    	while (faili >= 0) {
    		unlock_page(pages[faili]);
    		put_page(pages[faili]);
    		faili--;
    	}
    	return err;
    
    }
    
    static int btrfs_find_new_delalloc_bytes(struct btrfs_inode *inode,
    					 const u64 start,
    					 const u64 len,
    					 struct extent_state **cached_state)
    {
    	u64 search_start = start;
    	const u64 end = start + len - 1;
    
    	while (search_start < end) {
    		const u64 search_len = end - search_start + 1;
    		struct extent_map *em;
    		u64 em_len;
    		int ret = 0;
    
    		em = btrfs_get_extent(inode, NULL, 0, search_start,
    				      search_len, 0);
    		if (IS_ERR(em))
    			return PTR_ERR(em);
    
    		if (em->block_start != EXTENT_MAP_HOLE)
    			goto next;
    
    		em_len = em->len;
    		if (em->start < search_start)
    			em_len -= search_start - em->start;
    		if (em_len > search_len)
    			em_len = search_len;
    
    		ret = set_extent_bit(&inode->io_tree, search_start,
    				     search_start + em_len - 1,
    				     EXTENT_DELALLOC_NEW,
    				     NULL, cached_state, GFP_NOFS);
    next:
    		search_start = extent_map_end(em);
    		free_extent_map(em);
    		if (ret)
    			return ret;
    	}
    	return 0;
    }
    
    /*
     * This function locks the extent and properly waits for data=ordered extents
     * to finish before allowing the pages to be modified if need.
     *
     * The return value:
     * 1 - the extent is locked
     * 0 - the extent is not locked, and everything is OK
     * -EAGAIN - need re-prepare the pages
     * the other < 0 number - Something wrong happens
     */
    static noinline int
    lock_and_cleanup_extent_if_need(struct btrfs_inode *inode, struct page **pages,
    				size_t num_pages, loff_t pos,
    				size_t write_bytes,
    				u64 *lockstart, u64 *lockend,
    				struct extent_state **cached_state)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	u64 start_pos;
    	u64 last_pos;
    	int i;
    	int ret = 0;
    
    	start_pos = round_down(pos, fs_info->sectorsize);
    	last_pos = start_pos
    		+ round_up(pos + write_bytes - start_pos,
    			   fs_info->sectorsize) - 1;
    
    	if (start_pos < inode->vfs_inode.i_size ||
    	    (inode->flags & BTRFS_INODE_PREALLOC)) {
    		struct btrfs_ordered_extent *ordered;
    		unsigned int clear_bits;
    
    		lock_extent_bits(&inode->io_tree, start_pos, last_pos,
    				cached_state);
    		ordered = btrfs_lookup_ordered_range(inode, start_pos,
    						     last_pos - start_pos + 1);
    		if (ordered &&
    		    ordered->file_offset + ordered->len > start_pos &&
    		    ordered->file_offset <= last_pos) {
    			unlock_extent_cached(&inode->io_tree, start_pos,
    					last_pos, cached_state, GFP_NOFS);
    			for (i = 0; i < num_pages; i++) {
    				unlock_page(pages[i]);
    				put_page(pages[i]);
    			}
    			btrfs_start_ordered_extent(&inode->vfs_inode,
    					ordered, 1);
    			btrfs_put_ordered_extent(ordered);
    			return -EAGAIN;
    		}
    		if (ordered)
    			btrfs_put_ordered_extent(ordered);
    		ret = btrfs_find_new_delalloc_bytes(inode, start_pos,
    						    last_pos - start_pos + 1,
    						    cached_state);
    		clear_bits = EXTENT_DIRTY | EXTENT_DELALLOC |
    			EXTENT_DO_ACCOUNTING | EXTENT_DEFRAG;
    		if (ret)
    			clear_bits |= EXTENT_DELALLOC_NEW | EXTENT_LOCKED;
    		clear_extent_bit(&inode->io_tree, start_pos,
    				 last_pos, clear_bits,
    				 (clear_bits & EXTENT_LOCKED) ? 1 : 0,
    				 0, cached_state, GFP_NOFS);
    		if (ret)
    			return ret;
    		*lockstart = start_pos;
    		*lockend = last_pos;
    		ret = 1;
    	}
    
    	for (i = 0; i < num_pages; i++) {
    		if (clear_page_dirty_for_io(pages[i]))
    			account_page_redirty(pages[i]);
    		set_page_extent_mapped(pages[i]);
    		WARN_ON(!PageLocked(pages[i]));
    	}
    
    	return ret;
    }
    
    static noinline int check_can_nocow(struct btrfs_inode *inode, loff_t pos,
    				    size_t *write_bytes)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	struct btrfs_root *root = inode->root;
    	struct btrfs_ordered_extent *ordered;
    	u64 lockstart, lockend;
    	u64 num_bytes;
    	int ret;
    
    	ret = btrfs_start_write_no_snapshoting(root);
    	if (!ret)
    		return -ENOSPC;
    
    	lockstart = round_down(pos, fs_info->sectorsize);
    	lockend = round_up(pos + *write_bytes,
    			   fs_info->sectorsize) - 1;
    
    	while (1) {
    		lock_extent(&inode->io_tree, lockstart, lockend);
    		ordered = btrfs_lookup_ordered_range(inode, lockstart,
    						     lockend - lockstart + 1);
    		if (!ordered) {
    			break;
    		}
    		unlock_extent(&inode->io_tree, lockstart, lockend);
    		btrfs_start_ordered_extent(&inode->vfs_inode, ordered, 1);
    		btrfs_put_ordered_extent(ordered);
    	}
    
    	num_bytes = lockend - lockstart + 1;
    	ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes,
    			NULL, NULL, NULL);
    	if (ret <= 0) {
    		ret = 0;
    		btrfs_end_write_no_snapshoting(root);
    	} else {
    		*write_bytes = min_t(size_t, *write_bytes ,
    				     num_bytes - pos + lockstart);
    	}
    
    	unlock_extent(&inode->io_tree, lockstart, lockend);
    
    	return ret;
    }
    
    static noinline ssize_t __btrfs_buffered_write(struct file *file,
    					       struct iov_iter *i,
    					       loff_t pos)
    {
    	struct inode *inode = file_inode(file);
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	struct btrfs_root *root = BTRFS_I(inode)->root;
    	struct page **pages = NULL;
    	struct extent_state *cached_state = NULL;
    	u64 release_bytes = 0;
    	u64 lockstart;
    	u64 lockend;
    	size_t num_written = 0;
    	int nrptrs;
    	int ret = 0;
    	bool only_release_metadata = false;
    	bool force_page_uptodate = false;
    	bool need_unlock;
    
    	nrptrs = min(DIV_ROUND_UP(iov_iter_count(i), PAGE_SIZE),
    			PAGE_SIZE / (sizeof(struct page *)));
    	nrptrs = min(nrptrs, current->nr_dirtied_pause - current->nr_dirtied);
    	nrptrs = max(nrptrs, 8);
    	pages = kmalloc_array(nrptrs, sizeof(struct page *), GFP_KERNEL);
    	if (!pages)
    		return -ENOMEM;
    
    	while (iov_iter_count(i) > 0) {
    		size_t offset = pos & (PAGE_SIZE - 1);
    		size_t sector_offset;
    		size_t write_bytes = min(iov_iter_count(i),
    					 nrptrs * (size_t)PAGE_SIZE -
    					 offset);
    		size_t num_pages = DIV_ROUND_UP(write_bytes + offset,
    						PAGE_SIZE);
    		size_t reserve_bytes;
    		size_t dirty_pages;
    		size_t copied;
    		size_t dirty_sectors;
    		size_t num_sectors;
    
    		WARN_ON(num_pages > nrptrs);
    
    		/*
    		 * Fault pages before locking them in prepare_pages
    		 * to avoid recursive lock
    		 */
    		if (unlikely(iov_iter_fault_in_readable(i, write_bytes))) {
    			ret = -EFAULT;
    			break;
    		}
    
    		sector_offset = pos & (fs_info->sectorsize - 1);
    		reserve_bytes = round_up(write_bytes + sector_offset,
    				fs_info->sectorsize);
    
    		ret = btrfs_check_data_free_space(inode, pos, write_bytes);
    		if (ret < 0) {
    			if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
    						      BTRFS_INODE_PREALLOC)) &&
    			    check_can_nocow(BTRFS_I(inode), pos,
    					&write_bytes) > 0) {
    				/*
    				 * For nodata cow case, no need to reserve
    				 * data space.
    				 */
    				only_release_metadata = true;
    				/*
    				 * our prealloc extent may be smaller than
    				 * write_bytes, so scale down.
    				 */
    				num_pages = DIV_ROUND_UP(write_bytes + offset,
    							 PAGE_SIZE);
    				reserve_bytes = round_up(write_bytes +
    							 sector_offset,
    							 fs_info->sectorsize);
    			} else {
    				break;
    			}
    		}
    
    		ret = btrfs_delalloc_reserve_metadata(BTRFS_I(inode),
    				reserve_bytes);
    		if (ret) {
    			if (!only_release_metadata)
    				btrfs_free_reserved_data_space(inode, pos,
    							       write_bytes);
    			else
    				btrfs_end_write_no_snapshoting(root);
    			break;
    		}
    
    		release_bytes = reserve_bytes;
    		need_unlock = false;
    again:
    		/*
    		 * This is going to setup the pages array with the number of
    		 * pages we want, so we don't really need to worry about the
    		 * contents of pages from loop to loop
    		 */
    		ret = prepare_pages(inode, pages, num_pages,
    				    pos, write_bytes,
    				    force_page_uptodate);
    		if (ret)
    			break;
    
    		ret = lock_and_cleanup_extent_if_need(BTRFS_I(inode), pages,
    				num_pages, pos, write_bytes, &lockstart,
    				&lockend, &cached_state);
    		if (ret < 0) {
    			if (ret == -EAGAIN)
    				goto again;
    			break;
    		} else if (ret > 0) {
    			need_unlock = true;
    			ret = 0;
    		}
    
    		copied = btrfs_copy_from_user(pos, write_bytes, pages, i);
    
    		num_sectors = BTRFS_BYTES_TO_BLKS(fs_info, reserve_bytes);
    		dirty_sectors = round_up(copied + sector_offset,
    					fs_info->sectorsize);
    		dirty_sectors = BTRFS_BYTES_TO_BLKS(fs_info, dirty_sectors);
    
    		/*
    		 * if we have trouble faulting in the pages, fall
    		 * back to one page at a time
    		 */
    		if (copied < write_bytes)
    			nrptrs = 1;
    
    		if (copied == 0) {
    			force_page_uptodate = true;
    			dirty_sectors = 0;
    			dirty_pages = 0;
    		} else {
    			force_page_uptodate = false;
    			dirty_pages = DIV_ROUND_UP(copied + offset,
    						   PAGE_SIZE);
    		}
    
    		/*
    		 * If we had a short copy we need to release the excess delaloc
    		 * bytes we reserved.  We need to increment outstanding_extents
    		 * because btrfs_delalloc_release_space and
    		 * btrfs_delalloc_release_metadata will decrement it, but
    		 * we still have an outstanding extent for the chunk we actually
    		 * managed to copy.
    		 */
    		if (num_sectors > dirty_sectors) {
    			/* release everything except the sectors we dirtied */
    			release_bytes -= dirty_sectors <<
    						fs_info->sb->s_blocksize_bits;
    			if (copied > 0) {
    				spin_lock(&BTRFS_I(inode)->lock);
    				BTRFS_I(inode)->outstanding_extents++;
    				spin_unlock(&BTRFS_I(inode)->lock);
    			}
    			if (only_release_metadata) {
    				btrfs_delalloc_release_metadata(BTRFS_I(inode),
    								release_bytes);
    			} else {
    				u64 __pos;
    
    				__pos = round_down(pos,
    						   fs_info->sectorsize) +
    					(dirty_pages << PAGE_SHIFT);
    				btrfs_delalloc_release_space(inode, __pos,
    							     release_bytes);
    			}
    		}
    
    		release_bytes = round_up(copied + sector_offset,
    					fs_info->sectorsize);
    
    		if (copied > 0)
    			ret = btrfs_dirty_pages(inode, pages, dirty_pages,
    						pos, copied, NULL);
    		if (need_unlock)
    			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
    					     lockstart, lockend, &cached_state,
    					     GFP_NOFS);
    		if (ret) {
    			btrfs_drop_pages(pages, num_pages);
    			break;
    		}
    
    		release_bytes = 0;
    		if (only_release_metadata)
    			btrfs_end_write_no_snapshoting(root);
    
    		if (only_release_metadata && copied > 0) {
    			lockstart = round_down(pos,
    					       fs_info->sectorsize);
    			lockend = round_up(pos + copied,
    					   fs_info->sectorsize) - 1;
    
    			set_extent_bit(&BTRFS_I(inode)->io_tree, lockstart,
    				       lockend, EXTENT_NORESERVE, NULL,
    				       NULL, GFP_NOFS);
    			only_release_metadata = false;
    		}
    
    		btrfs_drop_pages(pages, num_pages);
    
    		cond_resched();
    
    		balance_dirty_pages_ratelimited(inode->i_mapping);
    		if (dirty_pages < (fs_info->nodesize >> PAGE_SHIFT) + 1)
    			btrfs_btree_balance_dirty(fs_info);
    
    		pos += copied;
    		num_written += copied;
    	}
    
    	kfree(pages);
    
    	if (release_bytes) {
    		if (only_release_metadata) {
    			btrfs_end_write_no_snapshoting(root);
    			btrfs_delalloc_release_metadata(BTRFS_I(inode),
    					release_bytes);
    		} else {
    			btrfs_delalloc_release_space(inode,
    						round_down(pos, fs_info->sectorsize),
    						release_bytes);
    		}
    	}
    
    	return num_written ? num_written : ret;
    }
    
    static ssize_t __btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
    {
    	struct file *file = iocb->ki_filp;
    	struct inode *inode = file_inode(file);
    	loff_t pos = iocb->ki_pos;
    	ssize_t written;
    	ssize_t written_buffered;
    	loff_t endbyte;
    	int err;
    
    	written = generic_file_direct_write(iocb, from);
    
    	if (written < 0 || !iov_iter_count(from))
    		return written;
    
    	pos += written;
    	written_buffered = __btrfs_buffered_write(file, from, pos);
    	if (written_buffered < 0) {
    		err = written_buffered;
    		goto out;
    	}
    	/*
    	 * Ensure all data is persisted. We want the next direct IO read to be
    	 * able to read what was just written.
    	 */
    	endbyte = pos + written_buffered - 1;
    	err = btrfs_fdatawrite_range(inode, pos, endbyte);
    	if (err)
    		goto out;
    	err = filemap_fdatawait_range(inode->i_mapping, pos, endbyte);
    	if (err)
    		goto out;
    	written += written_buffered;
    	iocb->ki_pos = pos + written_buffered;
    	invalidate_mapping_pages(file->f_mapping, pos >> PAGE_SHIFT,
    				 endbyte >> PAGE_SHIFT);
    out:
    	return written ? written : err;
    }
    
    static void update_time_for_write(struct inode *inode)
    {
    	struct timespec now;
    
    	if (IS_NOCMTIME(inode))
    		return;
    
    	now = current_time(inode);
    	if (!timespec_equal(&inode->i_mtime, &now))
    		inode->i_mtime = now;
    
    	if (!timespec_equal(&inode->i_ctime, &now))
    		inode->i_ctime = now;
    
    	if (IS_I_VERSION(inode))
    		inode_inc_iversion(inode);
    }
    
    static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
    				    struct iov_iter *from)
    {
    	struct file *file = iocb->ki_filp;
    	struct inode *inode = file_inode(file);
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	struct btrfs_root *root = BTRFS_I(inode)->root;
    	u64 start_pos;
    	u64 end_pos;
    	ssize_t num_written = 0;
    	bool sync = (file->f_flags & O_DSYNC) || IS_SYNC(file->f_mapping->host);
    	ssize_t err;
    	loff_t pos;
    	size_t count = iov_iter_count(from);
    	loff_t oldsize;
    	int clean_page = 0;
    
    	if (!inode_trylock(inode)) {
    		if (iocb->ki_flags & IOCB_NOWAIT)
    			return -EAGAIN;
    		inode_lock(inode);
    	}
    
    	err = generic_write_checks(iocb, from);
    	if (err <= 0) {
    		inode_unlock(inode);
    		return err;
    	}
    
    	pos = iocb->ki_pos;
    	if (iocb->ki_flags & IOCB_NOWAIT) {
    		/*
    		 * We will allocate space in case nodatacow is not set,
    		 * so bail
    		 */
    		if (!(BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW |
    					      BTRFS_INODE_PREALLOC)) ||
    		    check_can_nocow(BTRFS_I(inode), pos, &count) <= 0) {
    			inode_unlock(inode);
    			return -EAGAIN;
    		}
    	}
    
    	current->backing_dev_info = inode_to_bdi(inode);
    	err = file_remove_privs(file);
    	if (err) {
    		inode_unlock(inode);
    		goto out;
    	}
    
    	/*
    	 * If BTRFS flips readonly due to some impossible error
    	 * (fs_info->fs_state now has BTRFS_SUPER_FLAG_ERROR),
    	 * although we have opened a file as writable, we have
    	 * to stop this write operation to ensure FS consistency.
    	 */
    	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state)) {
    		inode_unlock(inode);
    		err = -EROFS;
    		goto out;
    	}
    
    	/*
    	 * We reserve space for updating the inode when we reserve space for the
    	 * extent we are going to write, so we will enospc out there.  We don't
    	 * need to start yet another transaction to update the inode as we will
    	 * update the inode when we finish writing whatever data we write.
    	 */
    	update_time_for_write(inode);
    
    	start_pos = round_down(pos, fs_info->sectorsize);
    	oldsize = i_size_read(inode);
    	if (start_pos > oldsize) {
    		/* Expand hole size to cover write data, preventing empty gap */
    		end_pos = round_up(pos + count,
    				   fs_info->sectorsize);
    		err = btrfs_cont_expand(inode, oldsize, end_pos);
    		if (err) {
    			inode_unlock(inode);
    			goto out;
    		}
    		if (start_pos > round_up(oldsize, fs_info->sectorsize))
    			clean_page = 1;
    	}
    
    	if (sync)
    		atomic_inc(&BTRFS_I(inode)->sync_writers);
    
    	if (iocb->ki_flags & IOCB_DIRECT) {
    		num_written = __btrfs_direct_write(iocb, from);
    	} else {
    		num_written = __btrfs_buffered_write(file, from, pos);
    		if (num_written > 0)
    			iocb->ki_pos = pos + num_written;
    		if (clean_page)
    			pagecache_isize_extended(inode, oldsize,
    						i_size_read(inode));
    	}
    
    	inode_unlock(inode);
    
    	/*
    	 * We also have to set last_sub_trans to the current log transid,
    	 * otherwise subsequent syncs to a file that's been synced in this
    	 * transaction will appear to have already occurred.
    	 */
    	spin_lock(&BTRFS_I(inode)->lock);
    	BTRFS_I(inode)->last_sub_trans = root->log_transid;
    	spin_unlock(&BTRFS_I(inode)->lock);
    	if (num_written > 0)
    		num_written = generic_write_sync(iocb, num_written);
    
    	if (sync)
    		atomic_dec(&BTRFS_I(inode)->sync_writers);
    out:
    	current->backing_dev_info = NULL;
    	return num_written ? num_written : err;
    }
    
    int btrfs_release_file(struct inode *inode, struct file *filp)
    {
    	if (filp->private_data)
    		btrfs_ioctl_trans_end(filp);
    	/*
    	 * ordered_data_close is set by settattr when we are about to truncate
    	 * a file from a non-zero size to a zero size.  This tries to
    	 * flush down new bytes that may have been written if the
    	 * application were using truncate to replace a file in place.
    	 */
    	if (test_and_clear_bit(BTRFS_INODE_ORDERED_DATA_CLOSE,
    			       &BTRFS_I(inode)->runtime_flags))
    			filemap_flush(inode->i_mapping);
    	return 0;
    }
    
    static int start_ordered_ops(struct inode *inode, loff_t start, loff_t end)
    {
    	int ret;
    
    	atomic_inc(&BTRFS_I(inode)->sync_writers);
    	ret = btrfs_fdatawrite_range(inode, start, end);
    	atomic_dec(&BTRFS_I(inode)->sync_writers);
    
    	return ret;
    }
    
    /*
     * fsync call for both files and directories.  This logs the inode into
     * the tree log instead of forcing full commits whenever possible.
     *
     * It needs to call filemap_fdatawait so that all ordered extent updates are
     * in the metadata btree are up to date for copying to the log.
     *
     * It drops the inode mutex before doing the tree log commit.  This is an
     * important optimization for directories because holding the mutex prevents
     * new operations on the dir while we write to disk.
     */
    int btrfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
    {
    	struct dentry *dentry = file_dentry(file);
    	struct inode *inode = d_inode(dentry);
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	struct btrfs_root *root = BTRFS_I(inode)->root;
    	struct btrfs_trans_handle *trans;
    	struct btrfs_log_ctx ctx;
    	int ret = 0;
    	bool full_sync = 0;
    	u64 len;
    
    	/*
    	 * The range length can be represented by u64, we have to do the typecasts
    	 * to avoid signed overflow if it's [0, LLONG_MAX] eg. from fsync()
    	 */
    	len = (u64)end - (u64)start + 1;
    	trace_btrfs_sync_file(file, datasync);
    
    	/*
    	 * We write the dirty pages in the range and wait until they complete
    	 * out of the ->i_mutex. If so, we can flush the dirty pages by
    	 * multi-task, and make the performance up.  See
    	 * btrfs_wait_ordered_range for an explanation of the ASYNC check.
    	 */
    	ret = start_ordered_ops(inode, start, end);
    	if (ret)
    		return ret;
    
    	inode_lock(inode);
    	atomic_inc(&root->log_batch);
    	full_sync = test_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
    			     &BTRFS_I(inode)->runtime_flags);
    	/*
    	 * We might have have had more pages made dirty after calling
    	 * start_ordered_ops and before acquiring the inode's i_mutex.
    	 */
    	if (full_sync) {
    		/*
    		 * For a full sync, we need to make sure any ordered operations
    		 * start and finish before we start logging the inode, so that
    		 * all extents are persisted and the respective file extent
    		 * items are in the fs/subvol btree.
    		 */
    		ret = btrfs_wait_ordered_range(inode, start, len);
    	} else {
    		/*
    		 * Start any new ordered operations before starting to log the
    		 * inode. We will wait for them to finish in btrfs_sync_log().
    		 *
    		 * Right before acquiring the inode's mutex, we might have new
    		 * writes dirtying pages, which won't immediately start the
    		 * respective ordered operations - that is done through the
    		 * fill_delalloc callbacks invoked from the writepage and
    		 * writepages address space operations. So make sure we start
    		 * all ordered operations before starting to log our inode. Not
    		 * doing this means that while logging the inode, writeback
    		 * could start and invoke writepage/writepages, which would call
    		 * the fill_delalloc callbacks (cow_file_range,
    		 * submit_compressed_extents). These callbacks add first an
    		 * extent map to the modified list of extents and then create
    		 * the respective ordered operation, which means in
    		 * tree-log.c:btrfs_log_inode() we might capture all existing
    		 * ordered operations (with btrfs_get_logged_extents()) before
    		 * the fill_delalloc callback adds its ordered operation, and by
    		 * the time we visit the modified list of extent maps (with
    		 * btrfs_log_changed_extents()), we see and process the extent
    		 * map they created. We then use the extent map to construct a
    		 * file extent item for logging without waiting for the
    		 * respective ordered operation to finish - this file extent
    		 * item points to a disk location that might not have yet been
    		 * written to, containing random data - so after a crash a log
    		 * replay will make our inode have file extent items that point
    		 * to disk locations containing invalid data, as we returned
    		 * success to userspace without waiting for the respective
    		 * ordered operation to finish, because it wasn't captured by
    		 * btrfs_get_logged_extents().
    		 */
    		ret = start_ordered_ops(inode, start, end);
    	}
    	if (ret) {
    		inode_unlock(inode);
    		goto out;
    	}
    	atomic_inc(&root->log_batch);
    
    	/*
    	 * If the last transaction that changed this file was before the current
    	 * transaction and we have the full sync flag set in our inode, we can
    	 * bail out now without any syncing.
    	 *
    	 * Note that we can't bail out if the full sync flag isn't set. This is
    	 * because when the full sync flag is set we start all ordered extents
    	 * and wait for them to fully complete - when they complete they update
    	 * the inode's last_trans field through:
    	 *
    	 *     btrfs_finish_ordered_io() ->
    	 *         btrfs_update_inode_fallback() ->
    	 *             btrfs_update_inode() ->
    	 *                 btrfs_set_inode_last_trans()
    	 *
    	 * So we are sure that last_trans is up to date and can do this check to
    	 * bail out safely. For the fast path, when the full sync flag is not
    	 * set in our inode, we can not do it because we start only our ordered
    	 * extents and don't wait for them to complete (that is when
    	 * btrfs_finish_ordered_io runs), so here at this point their last_trans
    	 * value might be less than or equals to fs_info->last_trans_committed,
    	 * and setting a speculative last_trans for an inode when a buffered
    	 * write is made (such as fs_info->generation + 1 for example) would not
    	 * be reliable since after setting the value and before fsync is called
    	 * any number of transactions can start and commit (transaction kthread
    	 * commits the current transaction periodically), and a transaction
    	 * commit does not start nor waits for ordered extents to complete.
    	 */
    	smp_mb();
    	if (btrfs_inode_in_log(BTRFS_I(inode), fs_info->generation) ||
    	    (full_sync && BTRFS_I(inode)->last_trans <=
    	     fs_info->last_trans_committed) ||
    	    (!btrfs_have_ordered_extents_in_range(inode, start, len) &&
    	     BTRFS_I(inode)->last_trans
    	     <= fs_info->last_trans_committed)) {
    		/*
    		 * We've had everything committed since the last time we were
    		 * modified so clear this flag in case it was set for whatever
    		 * reason, it's no longer relevant.
    		 */
    		clear_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
    			  &BTRFS_I(inode)->runtime_flags);
    		/*
    		 * An ordered extent might have started before and completed
    		 * already with io errors, in which case the inode was not
    		 * updated and we end up here. So check the inode's mapping
    		 * flags for any errors that might have happened while doing
    		 * writeback of file data.
    		 */
    		ret = filemap_check_errors(inode->i_mapping);
    		inode_unlock(inode);
    		goto out;
    	}
    
    	/*
    	 * ok we haven't committed the transaction yet, lets do a commit
    	 */
    	if (file->private_data)
    		btrfs_ioctl_trans_end(file);
    
    	/*
    	 * We use start here because we will need to wait on the IO to complete
    	 * in btrfs_sync_log, which could require joining a transaction (for
    	 * example checking cross references in the nocow path).  If we use join
    	 * here we could get into a situation where we're waiting on IO to
    	 * happen that is blocked on a transaction trying to commit.  With start
    	 * we inc the extwriter counter, so we wait for all extwriters to exit
    	 * before we start blocking join'ers.  This comment is to keep somebody
    	 * from thinking they are super smart and changing this to
    	 * btrfs_join_transaction *cough*Josef*cough*.
    	 */
    	trans = btrfs_start_transaction(root, 0);
    	if (IS_ERR(trans)) {
    		ret = PTR_ERR(trans);
    		inode_unlock(inode);
    		goto out;
    	}
    	trans->sync = true;
    
    	btrfs_init_log_ctx(&ctx, inode);
    
    	ret = btrfs_log_dentry_safe(trans, root, dentry, start, end, &ctx);
    	if (ret < 0) {
    		/* Fallthrough and commit/free transaction. */
    		ret = 1;
    	}
    
    	/* we've logged all the items and now have a consistent
    	 * version of the file in the log.  It is possible that
    	 * someone will come in and modify the file, but that's
    	 * fine because the log is consistent on disk, and we
    	 * have references to all of the file's extents
    	 *
    	 * It is possible that someone will come in and log the
    	 * file again, but that will end up using the synchronization
    	 * inside btrfs_sync_log to keep things safe.
    	 */
    	inode_unlock(inode);
    
    	/*
    	 * If any of the ordered extents had an error, just return it to user
    	 * space, so that the application knows some writes didn't succeed and
    	 * can take proper action (retry for e.g.). Blindly committing the
    	 * transaction in this case, would fool userspace that everything was
    	 * successful. And we also want to make sure our log doesn't contain
    	 * file extent items pointing to extents that weren't fully written to -
    	 * just like in the non fast fsync path, where we check for the ordered
    	 * operation's error flag before writing to the log tree and return -EIO
    	 * if any of them had this flag set (btrfs_wait_ordered_range) -
    	 * therefore we need to check for errors in the ordered operations,
    	 * which are indicated by ctx.io_err.
    	 */
    	if (ctx.io_err) {
    		btrfs_end_transaction(trans);
    		ret = ctx.io_err;
    		goto out;
    	}
    
    	if (ret != BTRFS_NO_LOG_SYNC) {
    		if (!ret) {
    			ret = btrfs_sync_log(trans, root, &ctx);
    			if (!ret) {
    				ret = btrfs_end_transaction(trans);
    				goto out;
    			}
    		}
    		if (!full_sync) {
    			ret = btrfs_wait_ordered_range(inode, start, len);
    			if (ret) {
    				btrfs_end_transaction(trans);
    				goto out;
    			}
    		}
    		ret = btrfs_commit_transaction(trans);
    	} else {
    		ret = btrfs_end_transaction(trans);
    	}
    out:
    	return ret > 0 ? -EIO : ret;
    }
    
    static const struct vm_operations_struct btrfs_file_vm_ops = {
    	.fault		= filemap_fault,
    	.map_pages	= filemap_map_pages,
    	.page_mkwrite	= btrfs_page_mkwrite,
    };
    
    static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
    {
    	struct address_space *mapping = filp->f_mapping;
    
    	if (!mapping->a_ops->readpage)
    		return -ENOEXEC;
    
    	file_accessed(filp);
    	vma->vm_ops = &btrfs_file_vm_ops;
    
    	return 0;
    }
    
    static int hole_mergeable(struct btrfs_inode *inode, struct extent_buffer *leaf,
    			  int slot, u64 start, u64 end)
    {
    	struct btrfs_file_extent_item *fi;
    	struct btrfs_key key;
    
    	if (slot < 0 || slot >= btrfs_header_nritems(leaf))
    		return 0;
    
    	btrfs_item_key_to_cpu(leaf, &key, slot);
    	if (key.objectid != btrfs_ino(inode) ||
    	    key.type != BTRFS_EXTENT_DATA_KEY)
    		return 0;
    
    	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
    
    	if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG)
    		return 0;
    
    	if (btrfs_file_extent_disk_bytenr(leaf, fi))
    		return 0;
    
    	if (key.offset == end)
    		return 1;
    	if (key.offset + btrfs_file_extent_num_bytes(leaf, fi) == start)
    		return 1;
    	return 0;
    }
    
    static int fill_holes(struct btrfs_trans_handle *trans,
    		struct btrfs_inode *inode,
    		struct btrfs_path *path, u64 offset, u64 end)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->vfs_inode.i_sb);
    	struct btrfs_root *root = inode->root;
    	struct extent_buffer *leaf;
    	struct btrfs_file_extent_item *fi;
    	struct extent_map *hole_em;
    	struct extent_map_tree *em_tree = &inode->extent_tree;
    	struct btrfs_key key;
    	int ret;
    
    	if (btrfs_fs_incompat(fs_info, NO_HOLES))
    		goto out;
    
    	key.objectid = btrfs_ino(inode);
    	key.type = BTRFS_EXTENT_DATA_KEY;
    	key.offset = offset;
    
    	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
    	if (ret <= 0) {
    		/*
    		 * We should have dropped this offset, so if we find it then
    		 * something has gone horribly wrong.
    		 */
    		if (ret == 0)
    			ret = -EINVAL;
    		return ret;
    	}
    
    	leaf = path->nodes[0];
    	if (hole_mergeable(inode, leaf, path->slots[0] - 1, offset, end)) {
    		u64 num_bytes;
    
    		path->slots[0]--;
    		fi = btrfs_item_ptr(leaf, path->slots[0],
    				    struct btrfs_file_extent_item);
    		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) +
    			end - offset;
    		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
    		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
    		btrfs_set_file_extent_offset(leaf, fi, 0);
    		btrfs_mark_buffer_dirty(leaf);
    		goto out;
    	}
    
    	if (hole_mergeable(inode, leaf, path->slots[0], offset, end)) {
    		u64 num_bytes;
    
    		key.offset = offset;
    		btrfs_set_item_key_safe(fs_info, path, &key);
    		fi = btrfs_item_ptr(leaf, path->slots[0],
    				    struct btrfs_file_extent_item);
    		num_bytes = btrfs_file_extent_num_bytes(leaf, fi) + end -
    			offset;
    		btrfs_set_file_extent_num_bytes(leaf, fi, num_bytes);
    		btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
    		btrfs_set_file_extent_offset(leaf, fi, 0);
    		btrfs_mark_buffer_dirty(leaf);
    		goto out;
    	}
    	btrfs_release_path(path);
    
    	ret = btrfs_insert_file_extent(trans, root, btrfs_ino(inode),
    			offset, 0, 0, end - offset, 0, end - offset, 0, 0, 0);
    	if (ret)
    		return ret;
    
    out:
    	btrfs_release_path(path);
    
    	hole_em = alloc_extent_map();
    	if (!hole_em) {
    		btrfs_drop_extent_cache(inode, offset, end - 1, 0);
    		set_bit(BTRFS_INODE_NEEDS_FULL_SYNC, &inode->runtime_flags);
    	} else {
    		hole_em->start = offset;
    		hole_em->len = end - offset;
    		hole_em->ram_bytes = hole_em->len;
    		hole_em->orig_start = offset;
    
    		hole_em->block_start = EXTENT_MAP_HOLE;
    		hole_em->block_len = 0;
    		hole_em->orig_block_len = 0;
    		hole_em->bdev = fs_info->fs_devices->latest_bdev;
    		hole_em->compress_type = BTRFS_COMPRESS_NONE;
    		hole_em->generation = trans->transid;
    
    		do {
    			btrfs_drop_extent_cache(inode, offset, end - 1, 0);
    			write_lock(&em_tree->lock);
    			ret = add_extent_mapping(em_tree, hole_em, 1);
    			write_unlock(&em_tree->lock);
    		} while (ret == -EEXIST);
    		free_extent_map(hole_em);
    		if (ret)
    			set_bit(BTRFS_INODE_NEEDS_FULL_SYNC,
    					&inode->runtime_flags);
    	}
    
    	return 0;
    }
    
    /*
     * Find a hole extent on given inode and change start/len to the end of hole
     * extent.(hole/vacuum extent whose em->start <= start &&
     *	   em->start + em->len > start)
     * When a hole extent is found, return 1 and modify start/len.
     */
    static int find_first_non_hole(struct inode *inode, u64 *start, u64 *len)
    {
    	struct extent_map *em;
    	int ret = 0;
    
    	em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, *start, *len, 0);
    	if (IS_ERR(em))
    		return PTR_ERR(em);
    
    	/* Hole or vacuum extent(only exists in no-hole mode) */
    	if (em->block_start == EXTENT_MAP_HOLE) {
    		ret = 1;
    		*len = em->start + em->len > *start + *len ?
    		       0 : *start + *len - em->start - em->len;
    		*start = em->start + em->len;
    	}
    	free_extent_map(em);
    	return ret;
    }
    
    static int btrfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	struct btrfs_root *root = BTRFS_I(inode)->root;
    	struct extent_state *cached_state = NULL;
    	struct btrfs_path *path;
    	struct btrfs_block_rsv *rsv;
    	struct btrfs_trans_handle *trans;
    	u64 lockstart;
    	u64 lockend;
    	u64 tail_start;
    	u64 tail_len;
    	u64 orig_start = offset;
    	u64 cur_offset;
    	u64 min_size = btrfs_calc_trans_metadata_size(fs_info, 1);
    	u64 drop_end;
    	int ret = 0;
    	int err = 0;
    	unsigned int rsv_count;
    	bool same_block;
    	bool no_holes = btrfs_fs_incompat(fs_info, NO_HOLES);
    	u64 ino_size;
    	bool truncated_block = false;
    	bool updated_inode = false;
    
    	ret = btrfs_wait_ordered_range(inode, offset, len);
    	if (ret)
    		return ret;
    
    	inode_lock(inode);
    	ino_size = round_up(inode->i_size, fs_info->sectorsize);
    	ret = find_first_non_hole(inode, &offset, &len);
    	if (ret < 0)
    		goto out_only_mutex;
    	if (ret && !len) {
    		/* Already in a large hole */
    		ret = 0;
    		goto out_only_mutex;
    	}
    
    	lockstart = round_up(offset, btrfs_inode_sectorsize(inode));
    	lockend = round_down(offset + len,
    			     btrfs_inode_sectorsize(inode)) - 1;
    	same_block = (BTRFS_BYTES_TO_BLKS(fs_info, offset))
    		== (BTRFS_BYTES_TO_BLKS(fs_info, offset + len - 1));
    	/*
    	 * We needn't truncate any block which is beyond the end of the file
    	 * because we are sure there is no data there.
    	 */
    	/*
    	 * Only do this if we are in the same block and we aren't doing the
    	 * entire block.
    	 */
    	if (same_block && len < fs_info->sectorsize) {
    		if (offset < ino_size) {
    			truncated_block = true;
    			ret = btrfs_truncate_block(inode, offset, len, 0);
    		} else {
    			ret = 0;
    		}
    		goto out_only_mutex;
    	}
    
    	/* zero back part of the first block */
    	if (offset < ino_size) {
    		truncated_block = true;
    		ret = btrfs_truncate_block(inode, offset, 0, 0);
    		if (ret) {
    			inode_unlock(inode);
    			return ret;
    		}
    	}
    
    	/* Check the aligned pages after the first unaligned page,
    	 * if offset != orig_start, which means the first unaligned page
    	 * including several following pages are already in holes,
    	 * the extra check can be skipped */
    	if (offset == orig_start) {
    		/* after truncate page, check hole again */
    		len = offset + len - lockstart;
    		offset = lockstart;
    		ret = find_first_non_hole(inode, &offset, &len);
    		if (ret < 0)
    			goto out_only_mutex;
    		if (ret && !len) {
    			ret = 0;
    			goto out_only_mutex;
    		}
    		lockstart = offset;
    	}
    
    	/* Check the tail unaligned part is in a hole */
    	tail_start = lockend + 1;
    	tail_len = offset + len - tail_start;
    	if (tail_len) {
    		ret = find_first_non_hole(inode, &tail_start, &tail_len);
    		if (unlikely(ret < 0))
    			goto out_only_mutex;
    		if (!ret) {
    			/* zero the front end of the last page */
    			if (tail_start + tail_len < ino_size) {
    				truncated_block = true;
    				ret = btrfs_truncate_block(inode,
    							tail_start + tail_len,
    							0, 1);
    				if (ret)
    					goto out_only_mutex;
    			}
    		}
    	}
    
    	if (lockend < lockstart) {
    		ret = 0;
    		goto out_only_mutex;
    	}
    
    	while (1) {
    		struct btrfs_ordered_extent *ordered;
    
    		truncate_pagecache_range(inode, lockstart, lockend);
    
    		lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
    				 &cached_state);
    		ordered = btrfs_lookup_first_ordered_extent(inode, lockend);
    
    		/*
    		 * We need to make sure we have no ordered extents in this range
    		 * and nobody raced in and read a page in this range, if we did
    		 * we need to try again.
    		 */
    		if ((!ordered ||
    		    (ordered->file_offset + ordered->len <= lockstart ||
    		     ordered->file_offset > lockend)) &&
    		     !btrfs_page_exists_in_range(inode, lockstart, lockend)) {
    			if (ordered)
    				btrfs_put_ordered_extent(ordered);
    			break;
    		}
    		if (ordered)
    			btrfs_put_ordered_extent(ordered);
    		unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart,
    				     lockend, &cached_state, GFP_NOFS);
    		ret = btrfs_wait_ordered_range(inode, lockstart,
    					       lockend - lockstart + 1);
    		if (ret) {
    			inode_unlock(inode);
    			return ret;
    		}
    	}
    
    	path = btrfs_alloc_path();
    	if (!path) {
    		ret = -ENOMEM;
    		goto out;
    	}
    
    	rsv = btrfs_alloc_block_rsv(fs_info, BTRFS_BLOCK_RSV_TEMP);
    	if (!rsv) {
    		ret = -ENOMEM;
    		goto out_free;
    	}
    	rsv->size = btrfs_calc_trans_metadata_size(fs_info, 1);
    	rsv->failfast = 1;
    
    	/*
    	 * 1 - update the inode
    	 * 1 - removing the extents in the range
    	 * 1 - adding the hole extent if no_holes isn't set
    	 */
    	rsv_count = no_holes ? 2 : 3;
    	trans = btrfs_start_transaction(root, rsv_count);
    	if (IS_ERR(trans)) {
    		err = PTR_ERR(trans);
    		goto out_free;
    	}
    
    	ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv, rsv,
    				      min_size, 0);
    	BUG_ON(ret);
    	trans->block_rsv = rsv;
    
    	cur_offset = lockstart;
    	len = lockend - cur_offset;
    	while (cur_offset < lockend) {
    		ret = __btrfs_drop_extents(trans, root, inode, path,
    					   cur_offset, lockend + 1,
    					   &drop_end, 1, 0, 0, NULL);
    		if (ret != -ENOSPC)
    			break;
    
    		trans->block_rsv = &fs_info->trans_block_rsv;
    
    		if (cur_offset < drop_end && cur_offset < ino_size) {
    			ret = fill_holes(trans, BTRFS_I(inode), path,
    					cur_offset, drop_end);
    			if (ret) {
    				/*
    				 * If we failed then we didn't insert our hole
    				 * entries for the area we dropped, so now the
    				 * fs is corrupted, so we must abort the
    				 * transaction.
    				 */
    				btrfs_abort_transaction(trans, ret);
    				err = ret;
    				break;
    			}
    		}
    
    		cur_offset = drop_end;
    
    		ret = btrfs_update_inode(trans, root, inode);
    		if (ret) {
    			err = ret;
    			break;
    		}
    
    		btrfs_end_transaction(trans);
    		btrfs_btree_balance_dirty(fs_info);
    
    		trans = btrfs_start_transaction(root, rsv_count);
    		if (IS_ERR(trans)) {
    			ret = PTR_ERR(trans);
    			trans = NULL;
    			break;
    		}
    
    		ret = btrfs_block_rsv_migrate(&fs_info->trans_block_rsv,
    					      rsv, min_size, 0);
    		BUG_ON(ret);	/* shouldn't happen */
    		trans->block_rsv = rsv;
    
    		ret = find_first_non_hole(inode, &cur_offset, &len);
    		if (unlikely(ret < 0))
    			break;
    		if (ret && !len) {
    			ret = 0;
    			break;
    		}
    	}
    
    	if (ret) {
    		err = ret;
    		goto out_trans;
    	}
    
    	trans->block_rsv = &fs_info->trans_block_rsv;
    	/*
    	 * If we are using the NO_HOLES feature we might have had already an
    	 * hole that overlaps a part of the region [lockstart, lockend] and
    	 * ends at (or beyond) lockend. Since we have no file extent items to
    	 * represent holes, drop_end can be less than lockend and so we must
    	 * make sure we have an extent map representing the existing hole (the
    	 * call to __btrfs_drop_extents() might have dropped the existing extent
    	 * map representing the existing hole), otherwise the fast fsync path
    	 * will not record the existence of the hole region
    	 * [existing_hole_start, lockend].
    	 */
    	if (drop_end <= lockend)
    		drop_end = lockend + 1;
    	/*
    	 * Don't insert file hole extent item if it's for a range beyond eof
    	 * (because it's useless) or if it represents a 0 bytes range (when
    	 * cur_offset == drop_end).
    	 */
    	if (cur_offset < ino_size && cur_offset < drop_end) {
    		ret = fill_holes(trans, BTRFS_I(inode), path,
    				cur_offset, drop_end);
    		if (ret) {
    			/* Same comment as above. */
    			btrfs_abort_transaction(trans, ret);
    			err = ret;
    			goto out_trans;
    		}
    	}
    
    out_trans:
    	if (!trans)
    		goto out_free;
    
    	inode_inc_iversion(inode);
    	inode->i_mtime = inode->i_ctime = current_time(inode);
    
    	trans->block_rsv = &fs_info->trans_block_rsv;
    	ret = btrfs_update_inode(trans, root, inode);
    	updated_inode = true;
    	btrfs_end_transaction(trans);
    	btrfs_btree_balance_dirty(fs_info);
    out_free:
    	btrfs_free_path(path);
    	btrfs_free_block_rsv(fs_info, rsv);
    out:
    	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
    			     &cached_state, GFP_NOFS);
    out_only_mutex:
    	if (!updated_inode && truncated_block && !ret && !err) {
    		/*
    		 * If we only end up zeroing part of a page, we still need to
    		 * update the inode item, so that all the time fields are
    		 * updated as well as the necessary btrfs inode in memory fields
    		 * for detecting, at fsync time, if the inode isn't yet in the
    		 * log tree or it's there but not up to date.
    		 */
    		trans = btrfs_start_transaction(root, 1);
    		if (IS_ERR(trans)) {
    			err = PTR_ERR(trans);
    		} else {
    			err = btrfs_update_inode(trans, root, inode);
    			ret = btrfs_end_transaction(trans);
    		}
    	}
    	inode_unlock(inode);
    	if (ret && !err)
    		err = ret;
    	return err;
    }
    
    /* Helper structure to record which range is already reserved */
    struct falloc_range {
    	struct list_head list;
    	u64 start;
    	u64 len;
    };
    
    /*
     * Helper function to add falloc range
     *
     * Caller should have locked the larger range of extent containing
     * [start, len)
     */
    static int add_falloc_range(struct list_head *head, u64 start, u64 len)
    {
    	struct falloc_range *prev = NULL;
    	struct falloc_range *range = NULL;
    
    	if (list_empty(head))
    		goto insert;
    
    	/*
    	 * As fallocate iterate by bytenr order, we only need to check
    	 * the last range.
    	 */
    	prev = list_entry(head->prev, struct falloc_range, list);
    	if (prev->start + prev->len == start) {
    		prev->len += len;
    		return 0;
    	}
    insert:
    	range = kmalloc(sizeof(*range), GFP_KERNEL);
    	if (!range)
    		return -ENOMEM;
    	range->start = start;
    	range->len = len;
    	list_add_tail(&range->list, head);
    	return 0;
    }
    
    static long btrfs_fallocate(struct file *file, int mode,
    			    loff_t offset, loff_t len)
    {
    	struct inode *inode = file_inode(file);
    	struct extent_state *cached_state = NULL;
    	struct falloc_range *range;
    	struct falloc_range *tmp;
    	struct list_head reserve_list;
    	u64 cur_offset;
    	u64 last_byte;
    	u64 alloc_start;
    	u64 alloc_end;
    	u64 alloc_hint = 0;
    	u64 locked_end;
    	u64 actual_end = 0;
    	struct extent_map *em;
    	int blocksize = btrfs_inode_sectorsize(inode);
    	int ret;
    
    	alloc_start = round_down(offset, blocksize);
    	alloc_end = round_up(offset + len, blocksize);
    	cur_offset = alloc_start;
    
    	/* Make sure we aren't being give some crap mode */
    	if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
    		return -EOPNOTSUPP;
    
    	if (mode & FALLOC_FL_PUNCH_HOLE)
    		return btrfs_punch_hole(inode, offset, len);
    
    	/*
    	 * Only trigger disk allocation, don't trigger qgroup reserve
    	 *
    	 * For qgroup space, it will be checked later.
    	 */
    	ret = btrfs_alloc_data_chunk_ondemand(BTRFS_I(inode),
    			alloc_end - alloc_start);
    	if (ret < 0)
    		return ret;
    
    	inode_lock(inode);
    
    	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size) {
    		ret = inode_newsize_ok(inode, offset + len);
    		if (ret)
    			goto out;
    	}
    
    	/*
    	 * TODO: Move these two operations after we have checked
    	 * accurate reserved space, or fallocate can still fail but
    	 * with page truncated or size expanded.
    	 *
    	 * But that's a minor problem and won't do much harm BTW.
    	 */
    	if (alloc_start > inode->i_size) {
    		ret = btrfs_cont_expand(inode, i_size_read(inode),
    					alloc_start);
    		if (ret)
    			goto out;
    	} else if (offset + len > inode->i_size) {
    		/*
    		 * If we are fallocating from the end of the file onward we
    		 * need to zero out the end of the block if i_size lands in the
    		 * middle of a block.
    		 */
    		ret = btrfs_truncate_block(inode, inode->i_size, 0, 0);
    		if (ret)
    			goto out;
    	}
    
    	/*
    	 * wait for ordered IO before we have any locks.  We'll loop again
    	 * below with the locks held.
    	 */
    	ret = btrfs_wait_ordered_range(inode, alloc_start,
    				       alloc_end - alloc_start);
    	if (ret)
    		goto out;
    
    	locked_end = alloc_end - 1;
    	while (1) {
    		struct btrfs_ordered_extent *ordered;
    
    		/* the extent lock is ordered inside the running
    		 * transaction
    		 */
    		lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
    				 locked_end, &cached_state);
    		ordered = btrfs_lookup_first_ordered_extent(inode,
    							    alloc_end - 1);
    		if (ordered &&
    		    ordered->file_offset + ordered->len > alloc_start &&
    		    ordered->file_offset < alloc_end) {
    			btrfs_put_ordered_extent(ordered);
    			unlock_extent_cached(&BTRFS_I(inode)->io_tree,
    					     alloc_start, locked_end,
    					     &cached_state, GFP_KERNEL);
    			/*
    			 * we can't wait on the range with the transaction
    			 * running or with the extent lock held
    			 */
    			ret = btrfs_wait_ordered_range(inode, alloc_start,
    						       alloc_end - alloc_start);
    			if (ret)
    				goto out;
    		} else {
    			if (ordered)
    				btrfs_put_ordered_extent(ordered);
    			break;
    		}
    	}
    
    	/* First, check if we exceed the qgroup limit */
    	INIT_LIST_HEAD(&reserve_list);
    	while (1) {
    		em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, cur_offset,
    				      alloc_end - cur_offset, 0);
    		if (IS_ERR(em)) {
    			ret = PTR_ERR(em);
    			break;
    		}
    		last_byte = min(extent_map_end(em), alloc_end);
    		actual_end = min_t(u64, extent_map_end(em), offset + len);
    		last_byte = ALIGN(last_byte, blocksize);
    		if (em->block_start == EXTENT_MAP_HOLE ||
    		    (cur_offset >= inode->i_size &&
    		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
    			ret = add_falloc_range(&reserve_list, cur_offset,
    					       last_byte - cur_offset);
    			if (ret < 0) {
    				free_extent_map(em);
    				break;
    			}
    			ret = btrfs_qgroup_reserve_data(inode, cur_offset,
    					last_byte - cur_offset);
    			if (ret < 0) {
    				free_extent_map(em);
    				break;
    			}
    		} else {
    			/*
    			 * Do not need to reserve unwritten extent for this
    			 * range, free reserved data space first, otherwise
    			 * it'll result in false ENOSPC error.
    			 */
    			btrfs_free_reserved_data_space(inode, cur_offset,
    				last_byte - cur_offset);
    		}
    		free_extent_map(em);
    		cur_offset = last_byte;
    		if (cur_offset >= alloc_end)
    			break;
    	}
    
    	/*
    	 * If ret is still 0, means we're OK to fallocate.
    	 * Or just cleanup the list and exit.
    	 */
    	list_for_each_entry_safe(range, tmp, &reserve_list, list) {
    		if (!ret)
    			ret = btrfs_prealloc_file_range(inode, mode,
    					range->start,
    					range->len, i_blocksize(inode),
    					offset + len, &alloc_hint);
    		else
    			btrfs_free_reserved_data_space(inode, range->start,
    						       range->len);
    		list_del(&range->list);
    		kfree(range);
    	}
    	if (ret < 0)
    		goto out_unlock;
    
    	if (actual_end > inode->i_size &&
    	    !(mode & FALLOC_FL_KEEP_SIZE)) {
    		struct btrfs_trans_handle *trans;
    		struct btrfs_root *root = BTRFS_I(inode)->root;
    
    		/*
    		 * We didn't need to allocate any more space, but we
    		 * still extended the size of the file so we need to
    		 * update i_size and the inode item.
    		 */
    		trans = btrfs_start_transaction(root, 1);
    		if (IS_ERR(trans)) {
    			ret = PTR_ERR(trans);
    		} else {
    			inode->i_ctime = current_time(inode);
    			i_size_write(inode, actual_end);
    			btrfs_ordered_update_i_size(inode, actual_end, NULL);
    			ret = btrfs_update_inode(trans, root, inode);
    			if (ret)
    				btrfs_end_transaction(trans);
    			else
    				ret = btrfs_end_transaction(trans);
    		}
    	}
    out_unlock:
    	unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
    			     &cached_state, GFP_KERNEL);
    out:
    	inode_unlock(inode);
    	/* Let go of our reservation. */
    	if (ret != 0)
    		btrfs_free_reserved_data_space(inode, alloc_start,
    				       alloc_end - cur_offset);
    	return ret;
    }
    
    static int find_desired_extent(struct inode *inode, loff_t *offset, int whence)
    {
    	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    	struct extent_map *em = NULL;
    	struct extent_state *cached_state = NULL;
    	u64 lockstart;
    	u64 lockend;
    	u64 start;
    	u64 len;
    	int ret = 0;
    
    	if (inode->i_size == 0)
    		return -ENXIO;
    
    	/*
    	 * *offset can be negative, in this case we start finding DATA/HOLE from
    	 * the very start of the file.
    	 */
    	start = max_t(loff_t, 0, *offset);
    
    	lockstart = round_down(start, fs_info->sectorsize);
    	lockend = round_up(i_size_read(inode),
    			   fs_info->sectorsize);
    	if (lockend <= lockstart)
    		lockend = lockstart + fs_info->sectorsize;
    	lockend--;
    	len = lockend - lockstart + 1;
    
    	lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend,
    			 &cached_state);
    
    	while (start < inode->i_size) {
    		em = btrfs_get_extent_fiemap(BTRFS_I(inode), NULL, 0,
    				start, len, 0);
    		if (IS_ERR(em)) {
    			ret = PTR_ERR(em);
    			em = NULL;
    			break;
    		}
    
    		if (whence == SEEK_HOLE &&
    		    (em->block_start == EXTENT_MAP_HOLE ||
    		     test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
    			break;
    		else if (whence == SEEK_DATA &&
    			   (em->block_start != EXTENT_MAP_HOLE &&
    			    !test_bit(EXTENT_FLAG_PREALLOC, &em->flags)))
    			break;
    
    		start = em->start + em->len;
    		free_extent_map(em);
    		em = NULL;
    		cond_resched();
    	}
    	free_extent_map(em);
    	if (!ret) {
    		if (whence == SEEK_DATA && start >= inode->i_size)
    			ret = -ENXIO;
    		else
    			*offset = min_t(loff_t, start, inode->i_size);
    	}
    	unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
    			     &cached_state, GFP_NOFS);
    	return ret;
    }
    
    static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int whence)
    {
    	struct inode *inode = file->f_mapping->host;
    	int ret;
    
    	inode_lock(inode);
    	switch (whence) {
    	case SEEK_END:
    	case SEEK_CUR:
    		offset = generic_file_llseek(file, offset, whence);
    		goto out;
    	case SEEK_DATA:
    	case SEEK_HOLE:
    		if (offset >= i_size_read(inode)) {
    			inode_unlock(inode);
    			return -ENXIO;
    		}
    
    		ret = find_desired_extent(inode, &offset, whence);
    		if (ret) {
    			inode_unlock(inode);
    			return ret;
    		}
    	}
    
    	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
    out:
    	inode_unlock(inode);
    	return offset;
    }
    
    static int btrfs_file_open(struct inode *inode, struct file *filp)
    {
    	filp->f_mode |= FMODE_AIO_NOWAIT;
    	return generic_file_open(inode, filp);
    }
    
    const struct file_operations btrfs_file_operations = {
    	.llseek		= btrfs_file_llseek,
    	.read_iter      = generic_file_read_iter,
    	.splice_read	= generic_file_splice_read,
    	.write_iter	= btrfs_file_write_iter,
    	.mmap		= btrfs_file_mmap,
    	.open		= btrfs_file_open,
    	.release	= btrfs_release_file,
    	.fsync		= btrfs_sync_file,
    	.fallocate	= btrfs_fallocate,
    	.unlocked_ioctl	= btrfs_ioctl,
    #ifdef CONFIG_COMPAT
    	.compat_ioctl	= btrfs_compat_ioctl,
    #endif
    	.clone_file_range = btrfs_clone_file_range,
    	.dedupe_file_range = btrfs_dedupe_file_range,
    };
    
    void btrfs_auto_defrag_exit(void)
    {
    	kmem_cache_destroy(btrfs_inode_defrag_cachep);
    }
    
    int btrfs_auto_defrag_init(void)
    {
    	btrfs_inode_defrag_cachep = kmem_cache_create("btrfs_inode_defrag",
    					sizeof(struct inode_defrag), 0,
    					SLAB_MEM_SPREAD,
    					NULL);
    	if (!btrfs_inode_defrag_cachep)
    		return -ENOMEM;
    
    	return 0;
    }
    
    int btrfs_fdatawrite_range(struct inode *inode, loff_t start, loff_t end)
    {
    	int ret;
    
    	/*
    	 * So with compression we will find and lock a dirty page and clear the
    	 * first one as dirty, setup an async extent, and immediately return
    	 * with the entire range locked but with nobody actually marked with
    	 * writeback.  So we can't just filemap_write_and_wait_range() and
    	 * expect it to work since it will just kick off a thread to do the
    	 * actual work.  So we need to call filemap_fdatawrite_range _again_
    	 * since it will wait on the page lock, which won't be unlocked until
    	 * after the pages have been marked as writeback and so we're good to go
    	 * from there.  We have to do this otherwise we'll miss the ordered
    	 * extents and that results in badness.  Please Josef, do not think you
    	 * know better and pull this out at some point in the future, it is
    	 * right and you are wrong.
    	 */
    	ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
    	if (!ret && test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
    			     &BTRFS_I(inode)->runtime_flags))
    		ret = filemap_fdatawrite_range(inode->i_mapping, start, end);
    
    	return ret;
    }