fs/btrfs/ordered-data.c - kernel/msm - Gitiles

 /*
  * 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/gfp.h>
 #include <linux/slab.h>
 #include <linux/blkdev.h>
 #include <linux/writeback.h>
 #include <linux/pagevec.h>
 #include "ctree.h"
 #include "transaction.h"
 #include "btrfs_inode.h"
 #include "extent_io.h"

 static u64 entry_end(struct btrfs_ordered_extent *entry)
 {
 	if (entry->file_offset + entry->len < entry->file_offset)
 		return (u64)-1;
 	return entry->file_offset + entry->len;
 }

 /* returns NULL if the insertion worked, or it returns the node it did find
  * in the tree
  */
 static struct rb_node *tree_insert(struct rb_root *root, u64 file_offset,
 				   struct rb_node *node)
 {
 	struct rb_node **p = &root->rb_node;
 	struct rb_node *parent = NULL;
 	struct btrfs_ordered_extent *entry;

 	while (*p) {
 		parent = *p;
 		entry = rb_entry(parent, struct btrfs_ordered_extent, rb_node);

 		if (file_offset < entry->file_offset)
 			p = &(*p)->rb_left;
 		else if (file_offset >= entry_end(entry))
 			p = &(*p)->rb_right;
 		else
 			return parent;
 	}

 	rb_link_node(node, parent, p);
 	rb_insert_color(node, root);
 	return NULL;
 }

 /*
  * look for a given offset in the tree, and if it can't be found return the
  * first lesser offset
  */
 static struct rb_node *__tree_search(struct rb_root *root, u64 file_offset,
 				     struct rb_node **prev_ret)
 {
 	struct rb_node *n = root->rb_node;
 	struct rb_node *prev = NULL;
 	struct rb_node *test;
 	struct btrfs_ordered_extent *entry;
 	struct btrfs_ordered_extent *prev_entry = NULL;

 	while (n) {
 		entry = rb_entry(n, struct btrfs_ordered_extent, rb_node);
 		prev = n;
 		prev_entry = entry;

 		if (file_offset < entry->file_offset)
 			n = n->rb_left;
 		else if (file_offset >= entry_end(entry))
 			n = n->rb_right;
 		else
 			return n;
 	}
 	if (!prev_ret)
 		return NULL;

 	while (prev && file_offset >= entry_end(prev_entry)) {
 		test = rb_next(prev);
 		if (!test)
 			break;
 		prev_entry = rb_entry(test, struct btrfs_ordered_extent,
 				      rb_node);
 		if (file_offset < entry_end(prev_entry))
 			break;

 		prev = test;
 	}
 	if (prev)
 		prev_entry = rb_entry(prev, struct btrfs_ordered_extent,
 				      rb_node);
 	while (prev && file_offset < entry_end(prev_entry)) {
 		test = rb_prev(prev);
 		if (!test)
 			break;
 		prev_entry = rb_entry(test, struct btrfs_ordered_extent,
 				      rb_node);
 		prev = test;
 	}
 	*prev_ret = prev;
 	return NULL;
 }

 /*
  * helper to check if a given offset is inside a given entry
  */
 static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
 {
 	if (file_offset < entry->file_offset ||
 	    entry->file_offset + entry->len <= file_offset)
 		return 0;
 	return 1;
 }

 /*
  * look find the first ordered struct that has this offset, otherwise
  * the first one less than this offset
  */
 static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
 					  u64 file_offset)
 {
 	struct rb_root *root = &tree->tree;
 	struct rb_node *prev;
 	struct rb_node *ret;
 	struct btrfs_ordered_extent *entry;

 	if (tree->last) {
 		entry = rb_entry(tree->last, struct btrfs_ordered_extent,
 				 rb_node);
 		if (offset_in_entry(entry, file_offset))
 			return tree->last;
 	}
 	ret = __tree_search(root, file_offset, &prev);
 	if (!ret)
 		ret = prev;
 	if (ret)
 		tree->last = ret;
 	return ret;
 }

 /* allocate and add a new ordered_extent into the per-inode tree.
  * file_offset is the logical offset in the file
  *
  * start is the disk block number of an extent already reserved in the
  * extent allocation tree
  *
  * len is the length of the extent
  *
  * This also sets the EXTENT_ORDERED bit on the range in the inode.
  *
  * The tree is given a single reference on the ordered extent that was
  * inserted.
  */
 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
 			     u64 start, u64 len, u64 disk_len, int type)
 {
 	struct btrfs_ordered_inode_tree *tree;
 	struct rb_node *node;
 	struct btrfs_ordered_extent *entry;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	entry = kzalloc(sizeof(*entry), GFP_NOFS);
 	if (!entry)
 		return -ENOMEM;

 	mutex_lock(&tree->mutex);
 	entry->file_offset = file_offset;
 	entry->start = start;
 	entry->len = len;
 	entry->disk_len = disk_len;
 	entry->inode = inode;
 	if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
 		set_bit(type, &entry->flags);

 	/* one ref for the tree */
 	atomic_set(&entry->refs, 1);
 	init_waitqueue_head(&entry->wait);
 	INIT_LIST_HEAD(&entry->list);
 	INIT_LIST_HEAD(&entry->root_extent_list);

 	node = tree_insert(&tree->tree, file_offset,
 			   &entry->rb_node);
 	BUG_ON(node);

 	set_extent_ordered(&BTRFS_I(inode)->io_tree, file_offset,
 			   entry_end(entry) - 1, GFP_NOFS);

 	spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 	list_add_tail(&entry->root_extent_list,
 		      &BTRFS_I(inode)->root->fs_info->ordered_extents);
 	spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);

 	mutex_unlock(&tree->mutex);
 	BUG_ON(node);
 	return 0;
 }

 /*
  * Add a struct btrfs_ordered_sum into the list of checksums to be inserted
  * when an ordered extent is finished.  If the list covers more than one
  * ordered extent, it is split across multiples.
  */
 int btrfs_add_ordered_sum(struct inode *inode,
 			  struct btrfs_ordered_extent *entry,
 			  struct btrfs_ordered_sum *sum)
 {
 	struct btrfs_ordered_inode_tree *tree;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	mutex_lock(&tree->mutex);
 	list_add_tail(&sum->list, &entry->list);
 	mutex_unlock(&tree->mutex);
 	return 0;
 }

 /*
  * this is used to account for finished IO across a given range
  * of the file.  The IO should not span ordered extents.  If
  * a given ordered_extent is completely done, 1 is returned, otherwise
  * 0.
  *
  * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
  * to make sure this function only returns 1 once for a given ordered extent.
  */
 int btrfs_dec_test_ordered_pending(struct inode *inode,
 				   u64 file_offset, u64 io_size)
 {
 	struct btrfs_ordered_inode_tree *tree;
 	struct rb_node *node;
 	struct btrfs_ordered_extent *entry;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	int ret;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	mutex_lock(&tree->mutex);
 	clear_extent_ordered(io_tree, file_offset, file_offset + io_size - 1,
 			     GFP_NOFS);
 	node = tree_search(tree, file_offset);
 	if (!node) {
 		ret = 1;
 		goto out;
 	}

 	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 	if (!offset_in_entry(entry, file_offset)) {
 		ret = 1;
 		goto out;
 	}

 	ret = test_range_bit(io_tree, entry->file_offset,
 			     entry->file_offset + entry->len - 1,
 			     EXTENT_ORDERED, 0);
 	if (ret == 0)
 		ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
 out:
 	mutex_unlock(&tree->mutex);
 	return ret == 0;
 }

 /*
  * used to drop a reference on an ordered extent.  This will free
  * the extent if the last reference is dropped
  */
 int btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
 {
 	struct list_head *cur;
 	struct btrfs_ordered_sum *sum;

 	if (atomic_dec_and_test(&entry->refs)) {
 		while (!list_empty(&entry->list)) {
 			cur = entry->list.next;
 			sum = list_entry(cur, struct btrfs_ordered_sum, list);
 			list_del(&sum->list);
 			kfree(sum);
 		}
 		kfree(entry);
 	}
 	return 0;
 }

 /*
  * remove an ordered extent from the tree.  No references are dropped
  * but, anyone waiting on this extent is woken up.
  */
 int btrfs_remove_ordered_extent(struct inode *inode,
 				struct btrfs_ordered_extent *entry)
 {
 	struct btrfs_ordered_inode_tree *tree;
 	struct rb_node *node;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	mutex_lock(&tree->mutex);
 	node = &entry->rb_node;
 	rb_erase(node, &tree->tree);
 	tree->last = NULL;
 	set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);

 	spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
 	list_del_init(&entry->root_extent_list);
 	spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);

 	mutex_unlock(&tree->mutex);
 	wake_up(&entry->wait);
 	return 0;
 }

 /*
  * wait for all the ordered extents in a root.  This is done when balancing
  * space between drives.
  */
 int btrfs_wait_ordered_extents(struct btrfs_root *root, int nocow_only)
 {
 	struct list_head splice;
 	struct list_head *cur;
 	struct btrfs_ordered_extent *ordered;
 	struct inode *inode;

 	INIT_LIST_HEAD(&splice);

 	spin_lock(&root->fs_info->ordered_extent_lock);
 	list_splice_init(&root->fs_info->ordered_extents, &splice);
 	while (!list_empty(&splice)) {
 		cur = splice.next;
 		ordered = list_entry(cur, struct btrfs_ordered_extent,
 				     root_extent_list);
 		if (nocow_only &&
 		    !test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags) &&
 		    !test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags)) {
 			list_move(&ordered->root_extent_list,
 				  &root->fs_info->ordered_extents);
 			cond_resched_lock(&root->fs_info->ordered_extent_lock);
 			continue;
 		}

 		list_del_init(&ordered->root_extent_list);
 		atomic_inc(&ordered->refs);

 		/*
 		 * the inode may be getting freed (in sys_unlink path).
 		 */
 		inode = igrab(ordered->inode);

 		spin_unlock(&root->fs_info->ordered_extent_lock);

 		if (inode) {
 			btrfs_start_ordered_extent(inode, ordered, 1);
 			btrfs_put_ordered_extent(ordered);
 			iput(inode);
 		} else {
 			btrfs_put_ordered_extent(ordered);
 		}

 		spin_lock(&root->fs_info->ordered_extent_lock);
 	}
 	spin_unlock(&root->fs_info->ordered_extent_lock);
 	return 0;
 }

 /*
  * Used to start IO or wait for a given ordered extent to finish.
  *
  * If wait is one, this effectively waits on page writeback for all the pages
  * in the extent, and it waits on the io completion code to insert
  * metadata into the btree corresponding to the extent
  */
 void btrfs_start_ordered_extent(struct inode *inode,
 				       struct btrfs_ordered_extent *entry,
 				       int wait)
 {
 	u64 start = entry->file_offset;
 	u64 end = start + entry->len - 1;

 	/*
 	 * pages in the range can be dirty, clean or writeback.  We
 	 * start IO on any dirty ones so the wait doesn't stall waiting
 	 * for pdflush to find them
 	 */
 	btrfs_fdatawrite_range(inode->i_mapping, start, end, WB_SYNC_ALL);
 	if (wait) {
 		wait_event(entry->wait, test_bit(BTRFS_ORDERED_COMPLETE,
 						 &entry->flags));
 	}
 }

 /*
  * Used to wait on ordered extents across a large range of bytes.
  */
 int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
 {
 	u64 end;
 	u64 orig_end;
 	u64 wait_end;
 	struct btrfs_ordered_extent *ordered;

 	if (start + len < start) {
 		orig_end = INT_LIMIT(loff_t);
 	} else {
 		orig_end = start + len - 1;
 		if (orig_end > INT_LIMIT(loff_t))
 			orig_end = INT_LIMIT(loff_t);
 	}
 	wait_end = orig_end;
 again:
 	/* start IO across the range first to instantiate any delalloc
 	 * extents
 	 */
 	btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_NONE);

 	/* The compression code will leave pages locked but return from
 	 * writepage without setting the page writeback.  Starting again
 	 * with WB_SYNC_ALL will end up waiting for the IO to actually start.
 	 */
 	btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_ALL);

 	btrfs_wait_on_page_writeback_range(inode->i_mapping,
 					   start >> PAGE_CACHE_SHIFT,
 					   orig_end >> PAGE_CACHE_SHIFT);

 	end = orig_end;
 	while (1) {
 		ordered = btrfs_lookup_first_ordered_extent(inode, end);
 		if (!ordered)
 			break;
 		if (ordered->file_offset > orig_end) {
 			btrfs_put_ordered_extent(ordered);
 			break;
 		}
 		if (ordered->file_offset + ordered->len < start) {
 			btrfs_put_ordered_extent(ordered);
 			break;
 		}
 		btrfs_start_ordered_extent(inode, ordered, 1);
 		end = ordered->file_offset;
 		btrfs_put_ordered_extent(ordered);
 		if (end == 0 || end == start)
 			break;
 		end--;
 	}
 	if (test_range_bit(&BTRFS_I(inode)->io_tree, start, orig_end,
 			   EXTENT_ORDERED | EXTENT_DELALLOC, 0)) {
 		schedule_timeout(1);
 		goto again;
 	}
 	return 0;
 }

 /*
  * find an ordered extent corresponding to file_offset.  return NULL if
  * nothing is found, otherwise take a reference on the extent and return it
  */
 struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
 							 u64 file_offset)
 {
 	struct btrfs_ordered_inode_tree *tree;
 	struct rb_node *node;
 	struct btrfs_ordered_extent *entry = NULL;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	mutex_lock(&tree->mutex);
 	node = tree_search(tree, file_offset);
 	if (!node)
 		goto out;

 	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 	if (!offset_in_entry(entry, file_offset))
 		entry = NULL;
 	if (entry)
 		atomic_inc(&entry->refs);
 out:
 	mutex_unlock(&tree->mutex);
 	return entry;
 }

 /*
  * lookup and return any extent before 'file_offset'.  NULL is returned
  * if none is found
  */
 struct btrfs_ordered_extent *
 btrfs_lookup_first_ordered_extent(struct inode *inode, u64 file_offset)
 {
 	struct btrfs_ordered_inode_tree *tree;
 	struct rb_node *node;
 	struct btrfs_ordered_extent *entry = NULL;

 	tree = &BTRFS_I(inode)->ordered_tree;
 	mutex_lock(&tree->mutex);
 	node = tree_search(tree, file_offset);
 	if (!node)
 		goto out;

 	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 	atomic_inc(&entry->refs);
 out:
 	mutex_unlock(&tree->mutex);
 	return entry;
 }

 /*
  * After an extent is done, call this to conditionally update the on disk
  * i_size.  i_size is updated to cover any fully written part of the file.
  */
 int btrfs_ordered_update_i_size(struct inode *inode,
 				struct btrfs_ordered_extent *ordered)
 {
 	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
 	u64 disk_i_size;
 	u64 new_i_size;
 	u64 i_size_test;
 	struct rb_node *node;
 	struct btrfs_ordered_extent *test;

 	mutex_lock(&tree->mutex);
 	disk_i_size = BTRFS_I(inode)->disk_i_size;

 	/*
 	 * if the disk i_size is already at the inode->i_size, or
 	 * this ordered extent is inside the disk i_size, we're done
 	 */
 	if (disk_i_size >= inode->i_size ||
 	    ordered->file_offset + ordered->len <= disk_i_size) {
 		goto out;
 	}

 	/*
 	 * we can't update the disk_isize if there are delalloc bytes
 	 * between disk_i_size and  this ordered extent
 	 */
 	if (test_range_bit(io_tree, disk_i_size,
 			   ordered->file_offset + ordered->len - 1,
 			   EXTENT_DELALLOC, 0)) {
 		goto out;
 	}
 	/*
 	 * walk backward from this ordered extent to disk_i_size.
 	 * if we find an ordered extent then we can't update disk i_size
 	 * yet
 	 */
 	node = &ordered->rb_node;
 	while (1) {
 		node = rb_prev(node);
 		if (!node)
 			break;
 		test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 		if (test->file_offset + test->len <= disk_i_size)
 			break;
 		if (test->file_offset >= inode->i_size)
 			break;
 		if (test->file_offset >= disk_i_size)
 			goto out;
 	}
 	new_i_size = min_t(u64, entry_end(ordered), i_size_read(inode));

 	/*
 	 * at this point, we know we can safely update i_size to at least
 	 * the offset from this ordered extent.  But, we need to
 	 * walk forward and see if ios from higher up in the file have
 	 * finished.
 	 */
 	node = rb_next(&ordered->rb_node);
 	i_size_test = 0;
 	if (node) {
 		/*
 		 * do we have an area where IO might have finished
 		 * between our ordered extent and the next one.
 		 */
 		test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
 		if (test->file_offset > entry_end(ordered))
 			i_size_test = test->file_offset;
 	} else {
 		i_size_test = i_size_read(inode);
 	}

 	/*
 	 * i_size_test is the end of a region after this ordered
 	 * extent where there are no ordered extents.  As long as there
 	 * are no delalloc bytes in this area, it is safe to update
 	 * disk_i_size to the end of the region.
 	 */
 	if (i_size_test > entry_end(ordered) &&
 	    !test_range_bit(io_tree, entry_end(ordered), i_size_test - 1,
 			   EXTENT_DELALLOC, 0)) {
 		new_i_size = min_t(u64, i_size_test, i_size_read(inode));
 	}
 	BTRFS_I(inode)->disk_i_size = new_i_size;
 out:
 	mutex_unlock(&tree->mutex);
 	return 0;
 }

 /*
  * search the ordered extents for one corresponding to 'offset' and
  * try to find a checksum.  This is used because we allow pages to
  * be reclaimed before their checksum is actually put into the btree
  */
 int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr,
 			   u32 *sum)
 {
 	struct btrfs_ordered_sum *ordered_sum;
 	struct btrfs_sector_sum *sector_sums;
 	struct btrfs_ordered_extent *ordered;
 	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
 	unsigned long num_sectors;
 	unsigned long i;
 	u32 sectorsize = BTRFS_I(inode)->root->sectorsize;
 	int ret = 1;

 	ordered = btrfs_lookup_ordered_extent(inode, offset);
 	if (!ordered)
 		return 1;

 	mutex_lock(&tree->mutex);
 	list_for_each_entry_reverse(ordered_sum, &ordered->list, list) {
 		if (disk_bytenr >= ordered_sum->bytenr) {
 			num_sectors = ordered_sum->len / sectorsize;
 			sector_sums = ordered_sum->sums;
 			for (i = 0; i < num_sectors; i++) {
 				if (sector_sums[i].bytenr == disk_bytenr) {
 					*sum = sector_sums[i].sum;
 					ret = 0;
 					goto out;
 				}
 			}
 		}
 	}
 out:
 	mutex_unlock(&tree->mutex);
 	btrfs_put_ordered_extent(ordered);
 	return ret;
 }


 /**
  * taken from mm/filemap.c because it isn't exported
  *
  * __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
  * @mapping:	address space structure to write
  * @start:	offset in bytes where the range starts
  * @end:	offset in bytes where the range ends (inclusive)
  * @sync_mode:	enable synchronous operation
  *
  * Start writeback against all of a mapping's dirty pages that lie
  * within the byte offsets <start, end> inclusive.
  *
  * If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
  * opposed to a regular memory cleansing writeback.  The difference between
  * these two operations is that if a dirty page/buffer is encountered, it must
  * be waited upon, and not just skipped over.
  */
 int btrfs_fdatawrite_range(struct address_space *mapping, loff_t start,
 			   loff_t end, int sync_mode)
 {
 	struct writeback_control wbc = {
 		.sync_mode = sync_mode,
 		.nr_to_write = mapping->nrpages * 2,
 		.range_start = start,
 		.range_end = end,
 		.for_writepages = 1,
 	};
 	return btrfs_writepages(mapping, &wbc);
 }

 /**
  * taken from mm/filemap.c because it isn't exported
  *
  * wait_on_page_writeback_range - wait for writeback to complete
  * @mapping:	target address_space
  * @start:	beginning page index
  * @end:	ending page index
  *
  * Wait for writeback to complete against pages indexed by start->end
  * inclusive
  */
 int btrfs_wait_on_page_writeback_range(struct address_space *mapping,
 				       pgoff_t start, pgoff_t end)
 {
 	struct pagevec pvec;
 	int nr_pages;
 	int ret = 0;
 	pgoff_t index;

 	if (end < start)
 		return 0;

 	pagevec_init(&pvec, 0);
 	index = start;
 	while ((index <= end) &&
 			(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
 			PAGECACHE_TAG_WRITEBACK,
 			min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
 		unsigned i;

 		for (i = 0; i < nr_pages; i++) {
 			struct page *page = pvec.pages[i];

 			/* until radix tree lookup accepts end_index */
 			if (page->index > end)
 				continue;

 			wait_on_page_writeback(page);
 			if (PageError(page))
 				ret = -EIO;
 		}
 		pagevec_release(&pvec);
 		cond_resched();
 	}

 	/* Check for outstanding write errors */
 	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
 		ret = -ENOSPC;
 	if (test_and_clear_bit(AS_EIO, &mapping->flags))
 		ret = -EIO;

 	return ret;
 }
	/*
	* 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/gfp.h>
	#include <linux/slab.h>
	#include <linux/blkdev.h>
	#include <linux/writeback.h>
	#include <linux/pagevec.h>
	#include "ctree.h"
	#include "transaction.h"
	#include "btrfs_inode.h"
	#include "extent_io.h"

	static u64 entry_end(struct btrfs_ordered_extent *entry)
	{
	if (entry->file_offset + entry->len < entry->file_offset)
	return (u64)-1;
	return entry->file_offset + entry->len;
	}

	/* returns NULL if the insertion worked, or it returns the node it did find
	* in the tree
	*/
	static struct rb_node tree_insert(struct rb_root root, u64 file_offset,
	struct rb_node *node)
	{
	struct rb_node **p = &root->rb_node;
	struct rb_node *parent = NULL;
	struct btrfs_ordered_extent *entry;

	while (*p) {
	parent = *p;
	entry = rb_entry(parent, struct btrfs_ordered_extent, rb_node);

	if (file_offset < entry->file_offset)
	p = &(*p)->rb_left;
	else if (file_offset >= entry_end(entry))
	p = &(*p)->rb_right;
	else
	return parent;
	}

	rb_link_node(node, parent, p);
	rb_insert_color(node, root);
	return NULL;
	}

	/*
	* look for a given offset in the tree, and if it can't be found return the
	* first lesser offset
	*/
	static struct rb_node __tree_search(struct rb_root root, u64 file_offset,
	struct rb_node **prev_ret)
	{
	struct rb_node *n = root->rb_node;
	struct rb_node *prev = NULL;
	struct rb_node *test;
	struct btrfs_ordered_extent *entry;
	struct btrfs_ordered_extent *prev_entry = NULL;

	while (n) {
	entry = rb_entry(n, struct btrfs_ordered_extent, rb_node);
	prev = n;
	prev_entry = entry;

	if (file_offset < entry->file_offset)
	n = n->rb_left;
	else if (file_offset >= entry_end(entry))
	n = n->rb_right;
	else
	return n;
	}
	if (!prev_ret)
	return NULL;

	while (prev && file_offset >= entry_end(prev_entry)) {
	test = rb_next(prev);
	if (!test)
	break;
	prev_entry = rb_entry(test, struct btrfs_ordered_extent,
	rb_node);
	if (file_offset < entry_end(prev_entry))
	break;

	prev = test;
	}
	if (prev)
	prev_entry = rb_entry(prev, struct btrfs_ordered_extent,
	rb_node);
	while (prev && file_offset < entry_end(prev_entry)) {
	test = rb_prev(prev);
	if (!test)
	break;
	prev_entry = rb_entry(test, struct btrfs_ordered_extent,
	rb_node);
	prev = test;
	}
	*prev_ret = prev;
	return NULL;
	}

	/*
	* helper to check if a given offset is inside a given entry
	*/
	static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
	{
	if (file_offset < entry->file_offset \|\|
	entry->file_offset + entry->len <= file_offset)
	return 0;
	return 1;
	}

	/*
	* look find the first ordered struct that has this offset, otherwise
	* the first one less than this offset
	*/
	static inline struct rb_node tree_search(struct btrfs_ordered_inode_tree tree,
	u64 file_offset)
	{
	struct rb_root *root = &tree->tree;
	struct rb_node *prev;
	struct rb_node *ret;
	struct btrfs_ordered_extent *entry;

	if (tree->last) {
	entry = rb_entry(tree->last, struct btrfs_ordered_extent,
	rb_node);
	if (offset_in_entry(entry, file_offset))
	return tree->last;
	}
	ret = __tree_search(root, file_offset, &prev);
	if (!ret)
	ret = prev;
	if (ret)
	tree->last = ret;
	return ret;
	}

	/* allocate and add a new ordered_extent into the per-inode tree.
	* file_offset is the logical offset in the file
	*
	* start is the disk block number of an extent already reserved in the
	* extent allocation tree
	*
	* len is the length of the extent
	*
	* This also sets the EXTENT_ORDERED bit on the range in the inode.
	*
	* The tree is given a single reference on the ordered extent that was
	* inserted.
	*/
	int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
	u64 start, u64 len, u64 disk_len, int type)
	{
	struct btrfs_ordered_inode_tree *tree;
	struct rb_node *node;
	struct btrfs_ordered_extent *entry;

	tree = &BTRFS_I(inode)->ordered_tree;
	entry = kzalloc(sizeof(*entry), GFP_NOFS);
	if (!entry)
	return -ENOMEM;

	mutex_lock(&tree->mutex);
	entry->file_offset = file_offset;
	entry->start = start;
	entry->len = len;
	entry->disk_len = disk_len;
	entry->inode = inode;
	if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
	set_bit(type, &entry->flags);

	/* one ref for the tree */
	atomic_set(&entry->refs, 1);
	init_waitqueue_head(&entry->wait);
	INIT_LIST_HEAD(&entry->list);
	INIT_LIST_HEAD(&entry->root_extent_list);

	node = tree_insert(&tree->tree, file_offset,
	&entry->rb_node);
	BUG_ON(node);

	set_extent_ordered(&BTRFS_I(inode)->io_tree, file_offset,
	entry_end(entry) - 1, GFP_NOFS);

	spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
	list_add_tail(&entry->root_extent_list,
	&BTRFS_I(inode)->root->fs_info->ordered_extents);
	spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);

	mutex_unlock(&tree->mutex);
	BUG_ON(node);
	return 0;
	}

	/*
	* Add a struct btrfs_ordered_sum into the list of checksums to be inserted
	* when an ordered extent is finished. If the list covers more than one
	* ordered extent, it is split across multiples.
	*/
	int btrfs_add_ordered_sum(struct inode *inode,
	struct btrfs_ordered_extent *entry,
	struct btrfs_ordered_sum *sum)
	{
	struct btrfs_ordered_inode_tree *tree;

	tree = &BTRFS_I(inode)->ordered_tree;
	mutex_lock(&tree->mutex);
	list_add_tail(&sum->list, &entry->list);
	mutex_unlock(&tree->mutex);
	return 0;
	}

	/*
	* this is used to account for finished IO across a given range
	* of the file. The IO should not span ordered extents. If
	* a given ordered_extent is completely done, 1 is returned, otherwise
	* 0.
	*
	* test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
	* to make sure this function only returns 1 once for a given ordered extent.
	*/
	int btrfs_dec_test_ordered_pending(struct inode *inode,
	u64 file_offset, u64 io_size)
	{
	struct btrfs_ordered_inode_tree *tree;
	struct rb_node *node;
	struct btrfs_ordered_extent *entry;
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
	int ret;

	tree = &BTRFS_I(inode)->ordered_tree;
	mutex_lock(&tree->mutex);
	clear_extent_ordered(io_tree, file_offset, file_offset + io_size - 1,
	GFP_NOFS);
	node = tree_search(tree, file_offset);
	if (!node) {
	ret = 1;
	goto out;
	}

	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
	if (!offset_in_entry(entry, file_offset)) {
	ret = 1;
	goto out;
	}

	ret = test_range_bit(io_tree, entry->file_offset,
	entry->file_offset + entry->len - 1,
	EXTENT_ORDERED, 0);
	if (ret == 0)
	ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
	out:
	mutex_unlock(&tree->mutex);
	return ret == 0;
	}

	/*
	* used to drop a reference on an ordered extent. This will free
	* the extent if the last reference is dropped
	*/
	int btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
	{
	struct list_head *cur;
	struct btrfs_ordered_sum *sum;

	if (atomic_dec_and_test(&entry->refs)) {
	while (!list_empty(&entry->list)) {
	cur = entry->list.next;
	sum = list_entry(cur, struct btrfs_ordered_sum, list);
	list_del(&sum->list);
	kfree(sum);
	}
	kfree(entry);
	}
	return 0;
	}

	/*
	* remove an ordered extent from the tree. No references are dropped
	* but, anyone waiting on this extent is woken up.
	*/
	int btrfs_remove_ordered_extent(struct inode *inode,
	struct btrfs_ordered_extent *entry)
	{
	struct btrfs_ordered_inode_tree *tree;
	struct rb_node *node;

	tree = &BTRFS_I(inode)->ordered_tree;
	mutex_lock(&tree->mutex);
	node = &entry->rb_node;
	rb_erase(node, &tree->tree);
	tree->last = NULL;
	set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);

	spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
	list_del_init(&entry->root_extent_list);
	spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);

	mutex_unlock(&tree->mutex);
	wake_up(&entry->wait);
	return 0;
	}

	/*
	* wait for all the ordered extents in a root. This is done when balancing
	* space between drives.
	*/
	int btrfs_wait_ordered_extents(struct btrfs_root *root, int nocow_only)
	{
	struct list_head splice;
	struct list_head *cur;
	struct btrfs_ordered_extent *ordered;
	struct inode *inode;

	INIT_LIST_HEAD(&splice);

	spin_lock(&root->fs_info->ordered_extent_lock);
	list_splice_init(&root->fs_info->ordered_extents, &splice);
	while (!list_empty(&splice)) {
	cur = splice.next;
	ordered = list_entry(cur, struct btrfs_ordered_extent,
	root_extent_list);
	if (nocow_only &&
	!test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags) &&
	!test_bit(BTRFS_ORDERED_PREALLOC, &ordered->flags)) {
	list_move(&ordered->root_extent_list,
	&root->fs_info->ordered_extents);
	cond_resched_lock(&root->fs_info->ordered_extent_lock);
	continue;
	}

	list_del_init(&ordered->root_extent_list);
	atomic_inc(&ordered->refs);

	/*
	* the inode may be getting freed (in sys_unlink path).
	*/
	inode = igrab(ordered->inode);

	spin_unlock(&root->fs_info->ordered_extent_lock);

	if (inode) {
	btrfs_start_ordered_extent(inode, ordered, 1);
	btrfs_put_ordered_extent(ordered);
	iput(inode);
	} else {
	btrfs_put_ordered_extent(ordered);
	}

	spin_lock(&root->fs_info->ordered_extent_lock);
	}
	spin_unlock(&root->fs_info->ordered_extent_lock);
	return 0;
	}

	/*
	* Used to start IO or wait for a given ordered extent to finish.
	*
	* If wait is one, this effectively waits on page writeback for all the pages
	* in the extent, and it waits on the io completion code to insert
	* metadata into the btree corresponding to the extent
	*/
	void btrfs_start_ordered_extent(struct inode *inode,
	struct btrfs_ordered_extent *entry,
	int wait)
	{
	u64 start = entry->file_offset;
	u64 end = start + entry->len - 1;

	/*
	* pages in the range can be dirty, clean or writeback. We
	* start IO on any dirty ones so the wait doesn't stall waiting
	* for pdflush to find them
	*/
	btrfs_fdatawrite_range(inode->i_mapping, start, end, WB_SYNC_ALL);
	if (wait) {
	wait_event(entry->wait, test_bit(BTRFS_ORDERED_COMPLETE,
	&entry->flags));
	}
	}

	/*
	* Used to wait on ordered extents across a large range of bytes.
	*/
	int btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
	{
	u64 end;
	u64 orig_end;
	u64 wait_end;
	struct btrfs_ordered_extent *ordered;

	if (start + len < start) {
	orig_end = INT_LIMIT(loff_t);
	} else {
	orig_end = start + len - 1;
	if (orig_end > INT_LIMIT(loff_t))
	orig_end = INT_LIMIT(loff_t);
	}
	wait_end = orig_end;
	again:
	/* start IO across the range first to instantiate any delalloc
	* extents
	*/
	btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_NONE);

	/* The compression code will leave pages locked but return from
	* writepage without setting the page writeback. Starting again
	* with WB_SYNC_ALL will end up waiting for the IO to actually start.
	*/
	btrfs_fdatawrite_range(inode->i_mapping, start, orig_end, WB_SYNC_ALL);

	btrfs_wait_on_page_writeback_range(inode->i_mapping,
	start >> PAGE_CACHE_SHIFT,
	orig_end >> PAGE_CACHE_SHIFT);

	end = orig_end;
	while (1) {
	ordered = btrfs_lookup_first_ordered_extent(inode, end);
	if (!ordered)
	break;
	if (ordered->file_offset > orig_end) {
	btrfs_put_ordered_extent(ordered);
	break;
	}
	if (ordered->file_offset + ordered->len < start) {
	btrfs_put_ordered_extent(ordered);
	break;
	}
	btrfs_start_ordered_extent(inode, ordered, 1);
	end = ordered->file_offset;
	btrfs_put_ordered_extent(ordered);
	if (end == 0 \|\| end == start)
	break;
	end--;
	}
	if (test_range_bit(&BTRFS_I(inode)->io_tree, start, orig_end,
	EXTENT_ORDERED \| EXTENT_DELALLOC, 0)) {
	schedule_timeout(1);
	goto again;
	}
	return 0;
	}

	/*
	* find an ordered extent corresponding to file_offset. return NULL if
	* nothing is found, otherwise take a reference on the extent and return it
	*/
	struct btrfs_ordered_extent btrfs_lookup_ordered_extent(struct inode inode,
	u64 file_offset)
	{
	struct btrfs_ordered_inode_tree *tree;
	struct rb_node *node;
	struct btrfs_ordered_extent *entry = NULL;

	tree = &BTRFS_I(inode)->ordered_tree;
	mutex_lock(&tree->mutex);
	node = tree_search(tree, file_offset);
	if (!node)
	goto out;

	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
	if (!offset_in_entry(entry, file_offset))
	entry = NULL;
	if (entry)
	atomic_inc(&entry->refs);
	out:
	mutex_unlock(&tree->mutex);
	return entry;
	}

	/*
	* lookup and return any extent before 'file_offset'. NULL is returned
	* if none is found
	*/
	struct btrfs_ordered_extent *
	btrfs_lookup_first_ordered_extent(struct inode *inode, u64 file_offset)
	{
	struct btrfs_ordered_inode_tree *tree;
	struct rb_node *node;
	struct btrfs_ordered_extent *entry = NULL;

	tree = &BTRFS_I(inode)->ordered_tree;
	mutex_lock(&tree->mutex);
	node = tree_search(tree, file_offset);
	if (!node)
	goto out;

	entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
	atomic_inc(&entry->refs);
	out:
	mutex_unlock(&tree->mutex);
	return entry;
	}

	/*
	* After an extent is done, call this to conditionally update the on disk
	* i_size. i_size is updated to cover any fully written part of the file.
	*/
	int btrfs_ordered_update_i_size(struct inode *inode,
	struct btrfs_ordered_extent *ordered)
	{
	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
	u64 disk_i_size;
	u64 new_i_size;
	u64 i_size_test;
	struct rb_node *node;
	struct btrfs_ordered_extent *test;

	mutex_lock(&tree->mutex);
	disk_i_size = BTRFS_I(inode)->disk_i_size;

	/*
	* if the disk i_size is already at the inode->i_size, or
	* this ordered extent is inside the disk i_size, we're done
	*/
	if (disk_i_size >= inode->i_size \|\|
	ordered->file_offset + ordered->len <= disk_i_size) {
	goto out;
	}

	/*
	* we can't update the disk_isize if there are delalloc bytes
	* between disk_i_size and this ordered extent
	*/
	if (test_range_bit(io_tree, disk_i_size,
	ordered->file_offset + ordered->len - 1,
	EXTENT_DELALLOC, 0)) {
	goto out;
	}
	/*
	* walk backward from this ordered extent to disk_i_size.
	* if we find an ordered extent then we can't update disk i_size
	* yet
	*/
	node = &ordered->rb_node;
	while (1) {
	node = rb_prev(node);
	if (!node)
	break;
	test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
	if (test->file_offset + test->len <= disk_i_size)
	break;
	if (test->file_offset >= inode->i_size)
	break;
	if (test->file_offset >= disk_i_size)
	goto out;
	}
	new_i_size = min_t(u64, entry_end(ordered), i_size_read(inode));

	/*
	* at this point, we know we can safely update i_size to at least
	* the offset from this ordered extent. But, we need to
	* walk forward and see if ios from higher up in the file have
	* finished.
	*/
	node = rb_next(&ordered->rb_node);
	i_size_test = 0;
	if (node) {
	/*
	* do we have an area where IO might have finished
	* between our ordered extent and the next one.
	*/
	test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
	if (test->file_offset > entry_end(ordered))
	i_size_test = test->file_offset;
	} else {
	i_size_test = i_size_read(inode);
	}

	/*
	* i_size_test is the end of a region after this ordered
	* extent where there are no ordered extents. As long as there
	* are no delalloc bytes in this area, it is safe to update
	* disk_i_size to the end of the region.
	*/
	if (i_size_test > entry_end(ordered) &&
	!test_range_bit(io_tree, entry_end(ordered), i_size_test - 1,
	EXTENT_DELALLOC, 0)) {
	new_i_size = min_t(u64, i_size_test, i_size_read(inode));
	}
	BTRFS_I(inode)->disk_i_size = new_i_size;
	out:
	mutex_unlock(&tree->mutex);
	return 0;
	}

	/*
	* search the ordered extents for one corresponding to 'offset' and
	* try to find a checksum. This is used because we allow pages to
	* be reclaimed before their checksum is actually put into the btree
	*/
	int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr,
	u32 *sum)
	{
	struct btrfs_ordered_sum *ordered_sum;
	struct btrfs_sector_sum *sector_sums;
	struct btrfs_ordered_extent *ordered;
	struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
	unsigned long num_sectors;
	unsigned long i;
	u32 sectorsize = BTRFS_I(inode)->root->sectorsize;
	int ret = 1;

	ordered = btrfs_lookup_ordered_extent(inode, offset);
	if (!ordered)
	return 1;

	mutex_lock(&tree->mutex);
	list_for_each_entry_reverse(ordered_sum, &ordered->list, list) {
	if (disk_bytenr >= ordered_sum->bytenr) {
	num_sectors = ordered_sum->len / sectorsize;
	sector_sums = ordered_sum->sums;
	for (i = 0; i < num_sectors; i++) {
	if (sector_sums[i].bytenr == disk_bytenr) {
	*sum = sector_sums[i].sum;
	ret = 0;
	goto out;
	}
	}
	}
	}
	out:
	mutex_unlock(&tree->mutex);
	btrfs_put_ordered_extent(ordered);
	return ret;
	}


	/**
	* taken from mm/filemap.c because it isn't exported
	*
	* __filemap_fdatawrite_range - start writeback on mapping dirty pages in range
	* @mapping: address space structure to write
	* @start: offset in bytes where the range starts
	* @end: offset in bytes where the range ends (inclusive)
	* @sync_mode: enable synchronous operation
	*
	* Start writeback against all of a mapping's dirty pages that lie
	* within the byte offsets <start, end> inclusive.
	*
	* If sync_mode is WB_SYNC_ALL then this is a "data integrity" operation, as
	* opposed to a regular memory cleansing writeback. The difference between
	* these two operations is that if a dirty page/buffer is encountered, it must
	* be waited upon, and not just skipped over.
	*/
	int btrfs_fdatawrite_range(struct address_space *mapping, loff_t start,
	loff_t end, int sync_mode)
	{
	struct writeback_control wbc = {
	.sync_mode = sync_mode,
	.nr_to_write = mapping->nrpages * 2,
	.range_start = start,
	.range_end = end,
	.for_writepages = 1,
	};
	return btrfs_writepages(mapping, &wbc);
	}

	/**
	* taken from mm/filemap.c because it isn't exported
	*
	* wait_on_page_writeback_range - wait for writeback to complete
	* @mapping: target address_space
	* @start: beginning page index
	* @end: ending page index
	*
	* Wait for writeback to complete against pages indexed by start->end
	* inclusive
	*/
	int btrfs_wait_on_page_writeback_range(struct address_space *mapping,
	pgoff_t start, pgoff_t end)
	{
	struct pagevec pvec;
	int nr_pages;
	int ret = 0;
	pgoff_t index;

	if (end < start)
	return 0;

	pagevec_init(&pvec, 0);
	index = start;
	while ((index <= end) &&
	(nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
	PAGECACHE_TAG_WRITEBACK,
	min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1)) != 0) {
	unsigned i;

	for (i = 0; i < nr_pages; i++) {
	struct page *page = pvec.pages[i];

	/* until radix tree lookup accepts end_index */
	if (page->index > end)
	continue;

	wait_on_page_writeback(page);
	if (PageError(page))
	ret = -EIO;
	}
	pagevec_release(&pvec);
	cond_resched();
	}

	/* Check for outstanding write errors */
	if (test_and_clear_bit(AS_ENOSPC, &mapping->flags))
	ret = -ENOSPC;
	if (test_and_clear_bit(AS_EIO, &mapping->flags))
	ret = -EIO;

	return ret;
	}