fs/btrfs/file-item.c - kernel/msm-4.9 - 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/bio.h>
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/highmem.h>
 #include "ctree.h"
 #include "disk-io.h"
 #include "transaction.h"
 #include "print-tree.h"

 #define MAX_CSUM_ITEMS(r, size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
 				   sizeof(struct btrfs_item) * 2) / \
 				  size) - 1))

 #define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
 				   sizeof(struct btrfs_ordered_sum)) / \
 				   sizeof(struct btrfs_sector_sum) * \
 				   (r)->sectorsize - (r)->sectorsize)

 int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     u64 objectid, u64 pos,
 			     u64 disk_offset, u64 disk_num_bytes,
 			     u64 num_bytes, u64 offset, u64 ram_bytes,
 			     u8 compression, u8 encryption, u16 other_encoding)
 {
 	int ret = 0;
 	struct btrfs_file_extent_item *item;
 	struct btrfs_key file_key;
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;

 	path = btrfs_alloc_path();
 	BUG_ON(!path);
 	file_key.objectid = objectid;
 	file_key.offset = pos;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);

 	path->leave_spinning = 1;
 	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 				      sizeof(*item));
 	if (ret < 0)
 		goto out;
 	BUG_ON(ret);
 	leaf = path->nodes[0];
 	item = btrfs_item_ptr(leaf, path->slots[0],
 			      struct btrfs_file_extent_item);
 	btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
 	btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
 	btrfs_set_file_extent_offset(leaf, item, offset);
 	btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
 	btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
 	btrfs_set_file_extent_generation(leaf, item, trans->transid);
 	btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
 	btrfs_set_file_extent_compression(leaf, item, compression);
 	btrfs_set_file_extent_encryption(leaf, item, encryption);
 	btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);

 	btrfs_mark_buffer_dirty(leaf);
 out:
 	btrfs_free_path(path);
 	return ret;
 }

 struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
 					  struct btrfs_root *root,
 					  struct btrfs_path *path,
 					  u64 bytenr, int cow)
 {
 	int ret;
 	struct btrfs_key file_key;
 	struct btrfs_key found_key;
 	struct btrfs_csum_item *item;
 	struct extent_buffer *leaf;
 	u64 csum_offset = 0;
 	u16 csum_size =
 		btrfs_super_csum_size(&root->fs_info->super_copy);
 	int csums_in_item;

 	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 	file_key.offset = bytenr;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
 	ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
 	if (ret < 0)
 		goto fail;
 	leaf = path->nodes[0];
 	if (ret > 0) {
 		ret = 1;
 		if (path->slots[0] == 0)
 			goto fail;
 		path->slots[0]--;
 		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 		if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
 			goto fail;

 		csum_offset = (bytenr - found_key.offset) >>
 				root->fs_info->sb->s_blocksize_bits;
 		csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
 		csums_in_item /= csum_size;

 		if (csum_offset >= csums_in_item) {
 			ret = -EFBIG;
 			goto fail;
 		}
 	}
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
 	return item;
 fail:
 	if (ret > 0)
 		ret = -ENOENT;
 	return ERR_PTR(ret);
 }


 int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root,
 			     struct btrfs_path *path, u64 objectid,
 			     u64 offset, int mod)
 {
 	int ret;
 	struct btrfs_key file_key;
 	int ins_len = mod < 0 ? -1 : 0;
 	int cow = mod != 0;

 	file_key.objectid = objectid;
 	file_key.offset = offset;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
 	ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
 	return ret;
 }


 int btrfs_lookup_bio_sums(struct btrfs_root *root, struct inode *inode,
 			  struct bio *bio, u32 *dst)
 {
 	u32 sum;
 	struct bio_vec *bvec = bio->bi_io_vec;
 	int bio_index = 0;
 	u64 offset;
 	u64 item_start_offset = 0;
 	u64 item_last_offset = 0;
 	u64 disk_bytenr;
 	u32 diff;
 	u16 csum_size =
 		btrfs_super_csum_size(&root->fs_info->super_copy);
 	int ret;
 	struct btrfs_path *path;
 	struct btrfs_csum_item *item = NULL;
 	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;

 	path = btrfs_alloc_path();
 	if (bio->bi_size > PAGE_CACHE_SIZE * 8)
 		path->reada = 2;

 	WARN_ON(bio->bi_vcnt <= 0);

 	disk_bytenr = (u64)bio->bi_sector << 9;
 	while (bio_index < bio->bi_vcnt) {
 		offset = page_offset(bvec->bv_page) + bvec->bv_offset;
 		ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
 		if (ret == 0)
 			goto found;

 		if (!item || disk_bytenr < item_start_offset ||
 		    disk_bytenr >= item_last_offset) {
 			struct btrfs_key found_key;
 			u32 item_size;

 			if (item)
 				btrfs_release_path(root, path);
 			item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
 						 path, disk_bytenr, 0);
 			if (IS_ERR(item)) {
 				ret = PTR_ERR(item);
 				if (ret == -ENOENT || ret == -EFBIG)
 					ret = 0;
 				sum = 0;
 				if (BTRFS_I(inode)->root->root_key.objectid ==
 				    BTRFS_DATA_RELOC_TREE_OBJECTID) {
 					set_extent_bits(io_tree, offset,
 						offset + bvec->bv_len - 1,
 						EXTENT_NODATASUM, GFP_NOFS);
 				} else {
 					printk(KERN_INFO "btrfs no csum found "
 					       "for inode %lu start %llu\n",
 					       inode->i_ino,
 					       (unsigned long long)offset);
 				}
 				item = NULL;
 				btrfs_release_path(root, path);
 				goto found;
 			}
 			btrfs_item_key_to_cpu(path->nodes[0], &found_key,
 					      path->slots[0]);

 			item_start_offset = found_key.offset;
 			item_size = btrfs_item_size_nr(path->nodes[0],
 						       path->slots[0]);
 			item_last_offset = item_start_offset +
 				(item_size / csum_size) *
 				root->sectorsize;
 			item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 					      struct btrfs_csum_item);
 		}
 		/*
 		 * this byte range must be able to fit inside
 		 * a single leaf so it will also fit inside a u32
 		 */
 		diff = disk_bytenr - item_start_offset;
 		diff = diff / root->sectorsize;
 		diff = diff * csum_size;

 		read_extent_buffer(path->nodes[0], &sum,
 				   ((unsigned long)item) + diff,
 				   csum_size);
 found:
 		if (dst)
 			*dst++ = sum;
 		else
 			set_state_private(io_tree, offset, sum);
 		disk_bytenr += bvec->bv_len;
 		bio_index++;
 		bvec++;
 	}
 	btrfs_free_path(path);
 	return 0;
 }

 int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
 			     struct list_head *list)
 {
 	struct btrfs_key key;
 	struct btrfs_path *path;
 	struct extent_buffer *leaf;
 	struct btrfs_ordered_sum *sums;
 	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_csum_item *item;
 	unsigned long offset;
 	int ret;
 	size_t size;
 	u64 csum_end;
 	u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);

 	path = btrfs_alloc_path();
 	BUG_ON(!path);

 	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 	key.offset = start;
 	key.type = BTRFS_EXTENT_CSUM_KEY;

 	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
 	if (ret < 0)
 		goto fail;
 	if (ret > 0 && path->slots[0] > 0) {
 		leaf = path->nodes[0];
 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
 		if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
 		    key.type == BTRFS_EXTENT_CSUM_KEY) {
 			offset = (start - key.offset) >>
 				 root->fs_info->sb->s_blocksize_bits;
 			if (offset * csum_size <
 			    btrfs_item_size_nr(leaf, path->slots[0] - 1))
 				path->slots[0]--;
 		}
 	}

 	while (start <= end) {
 		leaf = path->nodes[0];
 		if (path->slots[0] >= btrfs_header_nritems(leaf)) {
 			ret = btrfs_next_leaf(root, path);
 			if (ret < 0)
 				goto fail;
 			if (ret > 0)
 				break;
 			leaf = path->nodes[0];
 		}

 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 		if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 		    key.type != BTRFS_EXTENT_CSUM_KEY)
 			break;

 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
 		if (key.offset > end)
 			break;

 		if (key.offset > start)
 			start = key.offset;

 		size = btrfs_item_size_nr(leaf, path->slots[0]);
 		csum_end = key.offset + (size / csum_size) * root->sectorsize;
 		if (csum_end <= start) {
 			path->slots[0]++;
 			continue;
 		}

 		csum_end = min(csum_end, end + 1);
 		item = btrfs_item_ptr(path->nodes[0], path->slots[0],
 				      struct btrfs_csum_item);
 		while (start < csum_end) {
 			size = min_t(size_t, csum_end - start,
 					MAX_ORDERED_SUM_BYTES(root));
 			sums = kzalloc(btrfs_ordered_sum_size(root, size),
 					GFP_NOFS);
 			BUG_ON(!sums);

 			sector_sum = sums->sums;
 			sums->bytenr = start;
 			sums->len = size;

 			offset = (start - key.offset) >>
 				root->fs_info->sb->s_blocksize_bits;
 			offset *= csum_size;

 			while (size > 0) {
 				read_extent_buffer(path->nodes[0],
 						&sector_sum->sum,
 						((unsigned long)item) +
 						offset, csum_size);
 				sector_sum->bytenr = start;

 				size -= root->sectorsize;
 				start += root->sectorsize;
 				offset += csum_size;
 				sector_sum++;
 			}
 			list_add_tail(&sums->list, list);
 		}
 		path->slots[0]++;
 	}
 	ret = 0;
 fail:
 	btrfs_free_path(path);
 	return ret;
 }

 int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
 		       struct bio *bio, u64 file_start, int contig)
 {
 	struct btrfs_ordered_sum *sums;
 	struct btrfs_sector_sum *sector_sum;
 	struct btrfs_ordered_extent *ordered;
 	char *data;
 	struct bio_vec *bvec = bio->bi_io_vec;
 	int bio_index = 0;
 	unsigned long total_bytes = 0;
 	unsigned long this_sum_bytes = 0;
 	u64 offset;
 	u64 disk_bytenr;

 	WARN_ON(bio->bi_vcnt <= 0);
 	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
 	if (!sums)
 		return -ENOMEM;

 	sector_sum = sums->sums;
 	disk_bytenr = (u64)bio->bi_sector << 9;
 	sums->len = bio->bi_size;
 	INIT_LIST_HEAD(&sums->list);

 	if (contig)
 		offset = file_start;
 	else
 		offset = page_offset(bvec->bv_page) + bvec->bv_offset;

 	ordered = btrfs_lookup_ordered_extent(inode, offset);
 	BUG_ON(!ordered);
 	sums->bytenr = ordered->start;

 	while (bio_index < bio->bi_vcnt) {
 		if (!contig)
 			offset = page_offset(bvec->bv_page) + bvec->bv_offset;

 		if (!contig && (offset >= ordered->file_offset + ordered->len ||
 		    offset < ordered->file_offset)) {
 			unsigned long bytes_left;
 			sums->len = this_sum_bytes;
 			this_sum_bytes = 0;
 			btrfs_add_ordered_sum(inode, ordered, sums);
 			btrfs_put_ordered_extent(ordered);

 			bytes_left = bio->bi_size - total_bytes;

 			sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
 				       GFP_NOFS);
 			BUG_ON(!sums);
 			sector_sum = sums->sums;
 			sums->len = bytes_left;
 			ordered = btrfs_lookup_ordered_extent(inode, offset);
 			BUG_ON(!ordered);
 			sums->bytenr = ordered->start;
 		}

 		data = kmap_atomic(bvec->bv_page, KM_USER0);
 		sector_sum->sum = ~(u32)0;
 		sector_sum->sum = btrfs_csum_data(root,
 						  data + bvec->bv_offset,
 						  sector_sum->sum,
 						  bvec->bv_len);
 		kunmap_atomic(data, KM_USER0);
 		btrfs_csum_final(sector_sum->sum,
 				 (char *)&sector_sum->sum);
 		sector_sum->bytenr = disk_bytenr;

 		sector_sum++;
 		bio_index++;
 		total_bytes += bvec->bv_len;
 		this_sum_bytes += bvec->bv_len;
 		disk_bytenr += bvec->bv_len;
 		offset += bvec->bv_len;
 		bvec++;
 	}
 	this_sum_bytes = 0;
 	btrfs_add_ordered_sum(inode, ordered, sums);
 	btrfs_put_ordered_extent(ordered);
 	return 0;
 }

 /*
  * helper function for csum removal, this expects the
  * key to describe the csum pointed to by the path, and it expects
  * the csum to overlap the range [bytenr, len]
  *
  * The csum should not be entirely contained in the range and the
  * range should not be entirely contained in the csum.
  *
  * This calls btrfs_truncate_item with the correct args based on the
  * overlap, and fixes up the key as required.
  */
 static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
 				      struct btrfs_root *root,
 				      struct btrfs_path *path,
 				      struct btrfs_key *key,
 				      u64 bytenr, u64 len)
 {
 	struct extent_buffer *leaf;
 	u16 csum_size =
 		btrfs_super_csum_size(&root->fs_info->super_copy);
 	u64 csum_end;
 	u64 end_byte = bytenr + len;
 	u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
 	int ret;

 	leaf = path->nodes[0];
 	csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 	csum_end <<= root->fs_info->sb->s_blocksize_bits;
 	csum_end += key->offset;

 	if (key->offset < bytenr && csum_end <= end_byte) {
 		/*
 		 *         [ bytenr - len ]
 		 *         [   ]
 		 *   [csum     ]
 		 *   A simple truncate off the end of the item
 		 */
 		u32 new_size = (bytenr - key->offset) >> blocksize_bits;
 		new_size *= csum_size;
 		ret = btrfs_truncate_item(trans, root, path, new_size, 1);
 		BUG_ON(ret);
 	} else if (key->offset >= bytenr && csum_end > end_byte &&
 		   end_byte > key->offset) {
 		/*
 		 *         [ bytenr - len ]
 		 *                 [ ]
 		 *                 [csum     ]
 		 * we need to truncate from the beginning of the csum
 		 */
 		u32 new_size = (csum_end - end_byte) >> blocksize_bits;
 		new_size *= csum_size;

 		ret = btrfs_truncate_item(trans, root, path, new_size, 0);
 		BUG_ON(ret);

 		key->offset = end_byte;
 		ret = btrfs_set_item_key_safe(trans, root, path, key);
 		BUG_ON(ret);
 	} else {
 		BUG();
 	}
 	return 0;
 }

 /*
  * deletes the csum items from the csum tree for a given
  * range of bytes.
  */
 int btrfs_del_csums(struct btrfs_trans_handle *trans,
 		    struct btrfs_root *root, u64 bytenr, u64 len)
 {
 	struct btrfs_path *path;
 	struct btrfs_key key;
 	u64 end_byte = bytenr + len;
 	u64 csum_end;
 	struct extent_buffer *leaf;
 	int ret;
 	u16 csum_size =
 		btrfs_super_csum_size(&root->fs_info->super_copy);
 	int blocksize_bits = root->fs_info->sb->s_blocksize_bits;

 	root = root->fs_info->csum_root;

 	path = btrfs_alloc_path();

 	while (1) {
 		key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 		key.offset = end_byte - 1;
 		key.type = BTRFS_EXTENT_CSUM_KEY;

 		path->leave_spinning = 1;
 		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
 		if (ret > 0) {
 			if (path->slots[0] == 0)
 				goto out;
 			path->slots[0]--;
 		}
 		leaf = path->nodes[0];
 		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

 		if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 		    key.type != BTRFS_EXTENT_CSUM_KEY) {
 			break;
 		}

 		if (key.offset >= end_byte)
 			break;

 		csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
 		csum_end <<= blocksize_bits;
 		csum_end += key.offset;

 		/* this csum ends before we start, we're done */
 		if (csum_end <= bytenr)
 			break;

 		/* delete the entire item, it is inside our range */
 		if (key.offset >= bytenr && csum_end <= end_byte) {
 			ret = btrfs_del_item(trans, root, path);
 			BUG_ON(ret);
 			if (key.offset == bytenr)
 				break;
 		} else if (key.offset < bytenr && csum_end > end_byte) {
 			unsigned long offset;
 			unsigned long shift_len;
 			unsigned long item_offset;
 			/*
 			 *        [ bytenr - len ]
 			 *     [csum                ]
 			 *
 			 * Our bytes are in the middle of the csum,
 			 * we need to split this item and insert a new one.
 			 *
 			 * But we can't drop the path because the
 			 * csum could change, get removed, extended etc.
 			 *
 			 * The trick here is the max size of a csum item leaves
 			 * enough room in the tree block for a single
 			 * item header.  So, we split the item in place,
 			 * adding a new header pointing to the existing
 			 * bytes.  Then we loop around again and we have
 			 * a nicely formed csum item that we can neatly
 			 * truncate.
 			 */
 			offset = (bytenr - key.offset) >> blocksize_bits;
 			offset *= csum_size;

 			shift_len = (len >> blocksize_bits) * csum_size;

 			item_offset = btrfs_item_ptr_offset(leaf,
 							    path->slots[0]);

 			memset_extent_buffer(leaf, 0, item_offset + offset,
 					     shift_len);
 			key.offset = bytenr;

 			/*
 			 * btrfs_split_item returns -EAGAIN when the
 			 * item changed size or key
 			 */
 			ret = btrfs_split_item(trans, root, path, &key, offset);
 			BUG_ON(ret && ret != -EAGAIN);

 			key.offset = end_byte - 1;
 		} else {
 			ret = truncate_one_csum(trans, root, path,
 						&key, bytenr, len);
 			BUG_ON(ret);
 			if (key.offset < bytenr)
 				break;
 		}
 		btrfs_release_path(root, path);
 	}
 out:
 	btrfs_free_path(path);
 	return 0;
 }

 int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
 			   struct btrfs_root *root,
 			   struct btrfs_ordered_sum *sums)
 {
 	u64 bytenr;
 	int ret;
 	struct btrfs_key file_key;
 	struct btrfs_key found_key;
 	u64 next_offset;
 	u64 total_bytes = 0;
 	int found_next;
 	struct btrfs_path *path;
 	struct btrfs_csum_item *item;
 	struct btrfs_csum_item *item_end;
 	struct extent_buffer *leaf = NULL;
 	u64 csum_offset;
 	struct btrfs_sector_sum *sector_sum;
 	u32 nritems;
 	u32 ins_size;
 	char *eb_map;
 	char *eb_token;
 	unsigned long map_len;
 	unsigned long map_start;
 	u16 csum_size =
 		btrfs_super_csum_size(&root->fs_info->super_copy);

 	path = btrfs_alloc_path();
 	BUG_ON(!path);
 	sector_sum = sums->sums;
 again:
 	next_offset = (u64)-1;
 	found_next = 0;
 	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
 	file_key.offset = sector_sum->bytenr;
 	bytenr = sector_sum->bytenr;
 	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);

 	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
 	if (!IS_ERR(item)) {
 		leaf = path->nodes[0];
 		ret = 0;
 		goto found;
 	}
 	ret = PTR_ERR(item);
 	if (ret != -EFBIG && ret != -ENOENT)
 		goto fail_unlock;

 	if (ret == -EFBIG) {
 		u32 item_size;
 		/* we found one, but it isn't big enough yet */
 		leaf = path->nodes[0];
 		item_size = btrfs_item_size_nr(leaf, path->slots[0]);
 		if ((item_size / csum_size) >=
 		    MAX_CSUM_ITEMS(root, csum_size)) {
 			/* already at max size, make a new one */
 			goto insert;
 		}
 	} else {
 		int slot = path->slots[0] + 1;
 		/* we didn't find a csum item, insert one */
 		nritems = btrfs_header_nritems(path->nodes[0]);
 		if (path->slots[0] >= nritems - 1) {
 			ret = btrfs_next_leaf(root, path);
 			if (ret == 1)
 				found_next = 1;
 			if (ret != 0)
 				goto insert;
 			slot = 0;
 		}
 		btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
 		if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 		    found_key.type != BTRFS_EXTENT_CSUM_KEY) {
 			found_next = 1;
 			goto insert;
 		}
 		next_offset = found_key.offset;
 		found_next = 1;
 		goto insert;
 	}

 	/*
 	 * at this point, we know the tree has an item, but it isn't big
 	 * enough yet to put our csum in.  Grow it
 	 */
 	btrfs_release_path(root, path);
 	ret = btrfs_search_slot(trans, root, &file_key, path,
 				csum_size, 1);
 	if (ret < 0)
 		goto fail_unlock;

 	if (ret > 0) {
 		if (path->slots[0] == 0)
 			goto insert;
 		path->slots[0]--;
 	}

 	leaf = path->nodes[0];
 	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 	csum_offset = (bytenr - found_key.offset) >>
 			root->fs_info->sb->s_blocksize_bits;

 	if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY ||
 	    found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
 	    csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
 		goto insert;
 	}

 	if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
 	    csum_size) {
 		u32 diff = (csum_offset + 1) * csum_size;

 		/*
 		 * is the item big enough already?  we dropped our lock
 		 * before and need to recheck
 		 */
 		if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
 			goto csum;

 		diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
 		if (diff != csum_size)
 			goto insert;

 		ret = btrfs_extend_item(trans, root, path, diff);
 		BUG_ON(ret);
 		goto csum;
 	}

 insert:
 	btrfs_release_path(root, path);
 	csum_offset = 0;
 	if (found_next) {
 		u64 tmp = total_bytes + root->sectorsize;
 		u64 next_sector = sector_sum->bytenr;
 		struct btrfs_sector_sum *next = sector_sum + 1;

 		while (tmp < sums->len) {
 			if (next_sector + root->sectorsize != next->bytenr)
 				break;
 			tmp += root->sectorsize;
 			next_sector = next->bytenr;
 			next++;
 		}
 		tmp = min(tmp, next_offset - file_key.offset);
 		tmp >>= root->fs_info->sb->s_blocksize_bits;
 		tmp = max((u64)1, tmp);
 		tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
 		ins_size = csum_size * tmp;
 	} else {
 		ins_size = csum_size;
 	}
 	path->leave_spinning = 1;
 	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
 				      ins_size);
 	path->leave_spinning = 0;
 	if (ret < 0)
 		goto fail_unlock;
 	if (ret != 0) {
 		WARN_ON(1);
 		goto fail_unlock;
 	}
 csum:
 	leaf = path->nodes[0];
 	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 	ret = 0;
 	item = (struct btrfs_csum_item *)((unsigned char *)item +
 					  csum_offset * csum_size);
 found:
 	item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
 	item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
 				      btrfs_item_size_nr(leaf, path->slots[0]));
 	eb_token = NULL;
 next_sector:

 	if (!eb_token ||
 	   (unsigned long)item + csum_size >= map_start + map_len) {
 		int err;

 		if (eb_token)
 			unmap_extent_buffer(leaf, eb_token, KM_USER1);
 		eb_token = NULL;
 		err = map_private_extent_buffer(leaf, (unsigned long)item,
 						csum_size,
 						&eb_token, &eb_map,
 						&map_start, &map_len, KM_USER1);
 		if (err)
 			eb_token = NULL;
 	}
 	if (eb_token) {
 		memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
 		       &sector_sum->sum, csum_size);
 	} else {
 		write_extent_buffer(leaf, &sector_sum->sum,
 				    (unsigned long)item, csum_size);
 	}

 	total_bytes += root->sectorsize;
 	sector_sum++;
 	if (total_bytes < sums->len) {
 		item = (struct btrfs_csum_item *)((char *)item +
 						  csum_size);
 		if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
 		    sector_sum->bytenr) {
 			bytenr = sector_sum->bytenr;
 			goto next_sector;
 		}
 	}
 	if (eb_token) {
 		unmap_extent_buffer(leaf, eb_token, KM_USER1);
 		eb_token = NULL;
 	}
 	btrfs_mark_buffer_dirty(path->nodes[0]);
 	if (total_bytes < sums->len) {
 		btrfs_release_path(root, path);
 		cond_resched();
 		goto again;
 	}
 out:
 	btrfs_free_path(path);
 	return ret;

 fail_unlock:
 	goto out;
 }
	/*
	* 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/bio.h>
	#include <linux/slab.h>
	#include <linux/pagemap.h>
	#include <linux/highmem.h>
	#include "ctree.h"
	#include "disk-io.h"
	#include "transaction.h"
	#include "print-tree.h"

	#define MAX_CSUM_ITEMS(r, size) ((((BTRFS_LEAF_DATA_SIZE(r) - \
	sizeof(struct btrfs_item) * 2) / \
	size) - 1))

	#define MAX_ORDERED_SUM_BYTES(r) ((PAGE_SIZE - \
	sizeof(struct btrfs_ordered_sum)) / \
	sizeof(struct btrfs_sector_sum) * \
	(r)->sectorsize - (r)->sectorsize)

	int btrfs_insert_file_extent(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	u64 objectid, u64 pos,
	u64 disk_offset, u64 disk_num_bytes,
	u64 num_bytes, u64 offset, u64 ram_bytes,
	u8 compression, u8 encryption, u16 other_encoding)
	{
	int ret = 0;
	struct btrfs_file_extent_item *item;
	struct btrfs_key file_key;
	struct btrfs_path *path;
	struct extent_buffer *leaf;

	path = btrfs_alloc_path();
	BUG_ON(!path);
	file_key.objectid = objectid;
	file_key.offset = pos;
	btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);

	path->leave_spinning = 1;
	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
	sizeof(*item));
	if (ret < 0)
	goto out;
	BUG_ON(ret);
	leaf = path->nodes[0];
	item = btrfs_item_ptr(leaf, path->slots[0],
	struct btrfs_file_extent_item);
	btrfs_set_file_extent_disk_bytenr(leaf, item, disk_offset);
	btrfs_set_file_extent_disk_num_bytes(leaf, item, disk_num_bytes);
	btrfs_set_file_extent_offset(leaf, item, offset);
	btrfs_set_file_extent_num_bytes(leaf, item, num_bytes);
	btrfs_set_file_extent_ram_bytes(leaf, item, ram_bytes);
	btrfs_set_file_extent_generation(leaf, item, trans->transid);
	btrfs_set_file_extent_type(leaf, item, BTRFS_FILE_EXTENT_REG);
	btrfs_set_file_extent_compression(leaf, item, compression);
	btrfs_set_file_extent_encryption(leaf, item, encryption);
	btrfs_set_file_extent_other_encoding(leaf, item, other_encoding);

	btrfs_mark_buffer_dirty(leaf);
	out:
	btrfs_free_path(path);
	return ret;
	}

	struct btrfs_csum_item btrfs_lookup_csum(struct btrfs_trans_handle trans,
	struct btrfs_root *root,
	struct btrfs_path *path,
	u64 bytenr, int cow)
	{
	int ret;
	struct btrfs_key file_key;
	struct btrfs_key found_key;
	struct btrfs_csum_item *item;
	struct extent_buffer *leaf;
	u64 csum_offset = 0;
	u16 csum_size =
	btrfs_super_csum_size(&root->fs_info->super_copy);
	int csums_in_item;

	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
	file_key.offset = bytenr;
	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);
	ret = btrfs_search_slot(trans, root, &file_key, path, 0, cow);
	if (ret < 0)
	goto fail;
	leaf = path->nodes[0];
	if (ret > 0) {
	ret = 1;
	if (path->slots[0] == 0)
	goto fail;
	path->slots[0]--;
	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
	if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY)
	goto fail;

	csum_offset = (bytenr - found_key.offset) >>
	root->fs_info->sb->s_blocksize_bits;
	csums_in_item = btrfs_item_size_nr(leaf, path->slots[0]);
	csums_in_item /= csum_size;

	if (csum_offset >= csums_in_item) {
	ret = -EFBIG;
	goto fail;
	}
	}
	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
	item = (struct btrfs_csum_item )((unsigned char )item +
	csum_offset * csum_size);
	return item;
	fail:
	if (ret > 0)
	ret = -ENOENT;
	return ERR_PTR(ret);
	}


	int btrfs_lookup_file_extent(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path, u64 objectid,
	u64 offset, int mod)
	{
	int ret;
	struct btrfs_key file_key;
	int ins_len = mod < 0 ? -1 : 0;
	int cow = mod != 0;

	file_key.objectid = objectid;
	file_key.offset = offset;
	btrfs_set_key_type(&file_key, BTRFS_EXTENT_DATA_KEY);
	ret = btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
	return ret;
	}


	int btrfs_lookup_bio_sums(struct btrfs_root root, struct inode inode,
	struct bio bio, u32 dst)
	{
	u32 sum;
	struct bio_vec *bvec = bio->bi_io_vec;
	int bio_index = 0;
	u64 offset;
	u64 item_start_offset = 0;
	u64 item_last_offset = 0;
	u64 disk_bytenr;
	u32 diff;
	u16 csum_size =
	btrfs_super_csum_size(&root->fs_info->super_copy);
	int ret;
	struct btrfs_path *path;
	struct btrfs_csum_item *item = NULL;
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;

	path = btrfs_alloc_path();
	if (bio->bi_size > PAGE_CACHE_SIZE * 8)
	path->reada = 2;

	WARN_ON(bio->bi_vcnt <= 0);

	disk_bytenr = (u64)bio->bi_sector << 9;
	while (bio_index < bio->bi_vcnt) {
	offset = page_offset(bvec->bv_page) + bvec->bv_offset;
	ret = btrfs_find_ordered_sum(inode, offset, disk_bytenr, &sum);
	if (ret == 0)
	goto found;

	if (!item \|\| disk_bytenr < item_start_offset \|\|
	disk_bytenr >= item_last_offset) {
	struct btrfs_key found_key;
	u32 item_size;

	if (item)
	btrfs_release_path(root, path);
	item = btrfs_lookup_csum(NULL, root->fs_info->csum_root,
	path, disk_bytenr, 0);
	if (IS_ERR(item)) {
	ret = PTR_ERR(item);
	if (ret == -ENOENT \|\| ret == -EFBIG)
	ret = 0;
	sum = 0;
	if (BTRFS_I(inode)->root->root_key.objectid ==
	BTRFS_DATA_RELOC_TREE_OBJECTID) {
	set_extent_bits(io_tree, offset,
	offset + bvec->bv_len - 1,
	EXTENT_NODATASUM, GFP_NOFS);
	} else {
	printk(KERN_INFO "btrfs no csum found "
	"for inode %lu start %llu\n",
	inode->i_ino,
	(unsigned long long)offset);
	}
	item = NULL;
	btrfs_release_path(root, path);
	goto found;
	}
	btrfs_item_key_to_cpu(path->nodes[0], &found_key,
	path->slots[0]);

	item_start_offset = found_key.offset;
	item_size = btrfs_item_size_nr(path->nodes[0],
	path->slots[0]);
	item_last_offset = item_start_offset +
	(item_size / csum_size) *
	root->sectorsize;
	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
	struct btrfs_csum_item);
	}
	/*
	* this byte range must be able to fit inside
	* a single leaf so it will also fit inside a u32
	*/
	diff = disk_bytenr - item_start_offset;
	diff = diff / root->sectorsize;
	diff = diff * csum_size;

	read_extent_buffer(path->nodes[0], &sum,
	((unsigned long)item) + diff,
	csum_size);
	found:
	if (dst)
	*dst++ = sum;
	else
	set_state_private(io_tree, offset, sum);
	disk_bytenr += bvec->bv_len;
	bio_index++;
	bvec++;
	}
	btrfs_free_path(path);
	return 0;
	}

	int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
	struct list_head *list)
	{
	struct btrfs_key key;
	struct btrfs_path *path;
	struct extent_buffer *leaf;
	struct btrfs_ordered_sum *sums;
	struct btrfs_sector_sum *sector_sum;
	struct btrfs_csum_item *item;
	unsigned long offset;
	int ret;
	size_t size;
	u64 csum_end;
	u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);

	path = btrfs_alloc_path();
	BUG_ON(!path);

	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
	key.offset = start;
	key.type = BTRFS_EXTENT_CSUM_KEY;

	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
	if (ret < 0)
	goto fail;
	if (ret > 0 && path->slots[0] > 0) {
	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
	if (key.objectid == BTRFS_EXTENT_CSUM_OBJECTID &&
	key.type == BTRFS_EXTENT_CSUM_KEY) {
	offset = (start - key.offset) >>
	root->fs_info->sb->s_blocksize_bits;
	if (offset * csum_size <
	btrfs_item_size_nr(leaf, path->slots[0] - 1))
	path->slots[0]--;
	}
	}

	while (start <= end) {
	leaf = path->nodes[0];
	if (path->slots[0] >= btrfs_header_nritems(leaf)) {
	ret = btrfs_next_leaf(root, path);
	if (ret < 0)
	goto fail;
	if (ret > 0)
	break;
	leaf = path->nodes[0];
	}

	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
	if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID \|\|
	key.type != BTRFS_EXTENT_CSUM_KEY)
	break;

	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
	if (key.offset > end)
	break;

	if (key.offset > start)
	start = key.offset;

	size = btrfs_item_size_nr(leaf, path->slots[0]);
	csum_end = key.offset + (size / csum_size) * root->sectorsize;
	if (csum_end <= start) {
	path->slots[0]++;
	continue;
	}

	csum_end = min(csum_end, end + 1);
	item = btrfs_item_ptr(path->nodes[0], path->slots[0],
	struct btrfs_csum_item);
	while (start < csum_end) {
	size = min_t(size_t, csum_end - start,
	MAX_ORDERED_SUM_BYTES(root));
	sums = kzalloc(btrfs_ordered_sum_size(root, size),
	GFP_NOFS);
	BUG_ON(!sums);

	sector_sum = sums->sums;
	sums->bytenr = start;
	sums->len = size;

	offset = (start - key.offset) >>
	root->fs_info->sb->s_blocksize_bits;
	offset *= csum_size;

	while (size > 0) {
	read_extent_buffer(path->nodes[0],
	&sector_sum->sum,
	((unsigned long)item) +
	offset, csum_size);
	sector_sum->bytenr = start;

	size -= root->sectorsize;
	start += root->sectorsize;
	offset += csum_size;
	sector_sum++;
	}
	list_add_tail(&sums->list, list);
	}
	path->slots[0]++;
	}
	ret = 0;
	fail:
	btrfs_free_path(path);
	return ret;
	}

	int btrfs_csum_one_bio(struct btrfs_root root, struct inode inode,
	struct bio *bio, u64 file_start, int contig)
	{
	struct btrfs_ordered_sum *sums;
	struct btrfs_sector_sum *sector_sum;
	struct btrfs_ordered_extent *ordered;
	char *data;
	struct bio_vec *bvec = bio->bi_io_vec;
	int bio_index = 0;
	unsigned long total_bytes = 0;
	unsigned long this_sum_bytes = 0;
	u64 offset;
	u64 disk_bytenr;

	WARN_ON(bio->bi_vcnt <= 0);
	sums = kzalloc(btrfs_ordered_sum_size(root, bio->bi_size), GFP_NOFS);
	if (!sums)
	return -ENOMEM;

	sector_sum = sums->sums;
	disk_bytenr = (u64)bio->bi_sector << 9;
	sums->len = bio->bi_size;
	INIT_LIST_HEAD(&sums->list);

	if (contig)
	offset = file_start;
	else
	offset = page_offset(bvec->bv_page) + bvec->bv_offset;

	ordered = btrfs_lookup_ordered_extent(inode, offset);
	BUG_ON(!ordered);
	sums->bytenr = ordered->start;

	while (bio_index < bio->bi_vcnt) {
	if (!contig)
	offset = page_offset(bvec->bv_page) + bvec->bv_offset;

	if (!contig && (offset >= ordered->file_offset + ordered->len \|\|
	offset < ordered->file_offset)) {
	unsigned long bytes_left;
	sums->len = this_sum_bytes;
	this_sum_bytes = 0;
	btrfs_add_ordered_sum(inode, ordered, sums);
	btrfs_put_ordered_extent(ordered);

	bytes_left = bio->bi_size - total_bytes;

	sums = kzalloc(btrfs_ordered_sum_size(root, bytes_left),
	GFP_NOFS);
	BUG_ON(!sums);
	sector_sum = sums->sums;
	sums->len = bytes_left;
	ordered = btrfs_lookup_ordered_extent(inode, offset);
	BUG_ON(!ordered);
	sums->bytenr = ordered->start;
	}

	data = kmap_atomic(bvec->bv_page, KM_USER0);
	sector_sum->sum = ~(u32)0;
	sector_sum->sum = btrfs_csum_data(root,
	data + bvec->bv_offset,
	sector_sum->sum,
	bvec->bv_len);
	kunmap_atomic(data, KM_USER0);
	btrfs_csum_final(sector_sum->sum,
	(char *)&sector_sum->sum);
	sector_sum->bytenr = disk_bytenr;

	sector_sum++;
	bio_index++;
	total_bytes += bvec->bv_len;
	this_sum_bytes += bvec->bv_len;
	disk_bytenr += bvec->bv_len;
	offset += bvec->bv_len;
	bvec++;
	}
	this_sum_bytes = 0;
	btrfs_add_ordered_sum(inode, ordered, sums);
	btrfs_put_ordered_extent(ordered);
	return 0;
	}

	/*
	* helper function for csum removal, this expects the
	* key to describe the csum pointed to by the path, and it expects
	* the csum to overlap the range [bytenr, len]
	*
	* The csum should not be entirely contained in the range and the
	* range should not be entirely contained in the csum.
	*
	* This calls btrfs_truncate_item with the correct args based on the
	* overlap, and fixes up the key as required.
	*/
	static noinline int truncate_one_csum(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_path *path,
	struct btrfs_key *key,
	u64 bytenr, u64 len)
	{
	struct extent_buffer *leaf;
	u16 csum_size =
	btrfs_super_csum_size(&root->fs_info->super_copy);
	u64 csum_end;
	u64 end_byte = bytenr + len;
	u32 blocksize_bits = root->fs_info->sb->s_blocksize_bits;
	int ret;

	leaf = path->nodes[0];
	csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
	csum_end <<= root->fs_info->sb->s_blocksize_bits;
	csum_end += key->offset;

	if (key->offset < bytenr && csum_end <= end_byte) {
	/*
	* [ bytenr - len ]
	* [ ]
	* [csum ]
	* A simple truncate off the end of the item
	*/
	u32 new_size = (bytenr - key->offset) >> blocksize_bits;
	new_size *= csum_size;
	ret = btrfs_truncate_item(trans, root, path, new_size, 1);
	BUG_ON(ret);
	} else if (key->offset >= bytenr && csum_end > end_byte &&
	end_byte > key->offset) {
	/*
	* [ bytenr - len ]
	* [ ]
	* [csum ]
	* we need to truncate from the beginning of the csum
	*/
	u32 new_size = (csum_end - end_byte) >> blocksize_bits;
	new_size *= csum_size;

	ret = btrfs_truncate_item(trans, root, path, new_size, 0);
	BUG_ON(ret);

	key->offset = end_byte;
	ret = btrfs_set_item_key_safe(trans, root, path, key);
	BUG_ON(ret);
	} else {
	BUG();
	}
	return 0;
	}

	/*
	* deletes the csum items from the csum tree for a given
	* range of bytes.
	*/
	int btrfs_del_csums(struct btrfs_trans_handle *trans,
	struct btrfs_root *root, u64 bytenr, u64 len)
	{
	struct btrfs_path *path;
	struct btrfs_key key;
	u64 end_byte = bytenr + len;
	u64 csum_end;
	struct extent_buffer *leaf;
	int ret;
	u16 csum_size =
	btrfs_super_csum_size(&root->fs_info->super_copy);
	int blocksize_bits = root->fs_info->sb->s_blocksize_bits;

	root = root->fs_info->csum_root;

	path = btrfs_alloc_path();

	while (1) {
	key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
	key.offset = end_byte - 1;
	key.type = BTRFS_EXTENT_CSUM_KEY;

	path->leave_spinning = 1;
	ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
	if (ret > 0) {
	if (path->slots[0] == 0)
	goto out;
	path->slots[0]--;
	}
	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);

	if (key.objectid != BTRFS_EXTENT_CSUM_OBJECTID \|\|
	key.type != BTRFS_EXTENT_CSUM_KEY) {
	break;
	}

	if (key.offset >= end_byte)
	break;

	csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
	csum_end <<= blocksize_bits;
	csum_end += key.offset;

	/* this csum ends before we start, we're done */
	if (csum_end <= bytenr)
	break;

	/* delete the entire item, it is inside our range */
	if (key.offset >= bytenr && csum_end <= end_byte) {
	ret = btrfs_del_item(trans, root, path);
	BUG_ON(ret);
	if (key.offset == bytenr)
	break;
	} else if (key.offset < bytenr && csum_end > end_byte) {
	unsigned long offset;
	unsigned long shift_len;
	unsigned long item_offset;
	/*
	* [ bytenr - len ]
	* [csum ]
	*
	* Our bytes are in the middle of the csum,
	* we need to split this item and insert a new one.
	*
	* But we can't drop the path because the
	* csum could change, get removed, extended etc.
	*
	* The trick here is the max size of a csum item leaves
	* enough room in the tree block for a single
	* item header. So, we split the item in place,
	* adding a new header pointing to the existing
	* bytes. Then we loop around again and we have
	* a nicely formed csum item that we can neatly
	* truncate.
	*/
	offset = (bytenr - key.offset) >> blocksize_bits;
	offset *= csum_size;

	shift_len = (len >> blocksize_bits) * csum_size;

	item_offset = btrfs_item_ptr_offset(leaf,
	path->slots[0]);

	memset_extent_buffer(leaf, 0, item_offset + offset,
	shift_len);
	key.offset = bytenr;

	/*
	* btrfs_split_item returns -EAGAIN when the
	* item changed size or key
	*/
	ret = btrfs_split_item(trans, root, path, &key, offset);
	BUG_ON(ret && ret != -EAGAIN);

	key.offset = end_byte - 1;
	} else {
	ret = truncate_one_csum(trans, root, path,
	&key, bytenr, len);
	BUG_ON(ret);
	if (key.offset < bytenr)
	break;
	}
	btrfs_release_path(root, path);
	}
	out:
	btrfs_free_path(path);
	return 0;
	}

	int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
	struct btrfs_root *root,
	struct btrfs_ordered_sum *sums)
	{
	u64 bytenr;
	int ret;
	struct btrfs_key file_key;
	struct btrfs_key found_key;
	u64 next_offset;
	u64 total_bytes = 0;
	int found_next;
	struct btrfs_path *path;
	struct btrfs_csum_item *item;
	struct btrfs_csum_item *item_end;
	struct extent_buffer *leaf = NULL;
	u64 csum_offset;
	struct btrfs_sector_sum *sector_sum;
	u32 nritems;
	u32 ins_size;
	char *eb_map;
	char *eb_token;
	unsigned long map_len;
	unsigned long map_start;
	u16 csum_size =
	btrfs_super_csum_size(&root->fs_info->super_copy);

	path = btrfs_alloc_path();
	BUG_ON(!path);
	sector_sum = sums->sums;
	again:
	next_offset = (u64)-1;
	found_next = 0;
	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
	file_key.offset = sector_sum->bytenr;
	bytenr = sector_sum->bytenr;
	btrfs_set_key_type(&file_key, BTRFS_EXTENT_CSUM_KEY);

	item = btrfs_lookup_csum(trans, root, path, sector_sum->bytenr, 1);
	if (!IS_ERR(item)) {
	leaf = path->nodes[0];
	ret = 0;
	goto found;
	}
	ret = PTR_ERR(item);
	if (ret != -EFBIG && ret != -ENOENT)
	goto fail_unlock;

	if (ret == -EFBIG) {
	u32 item_size;
	/* we found one, but it isn't big enough yet */
	leaf = path->nodes[0];
	item_size = btrfs_item_size_nr(leaf, path->slots[0]);
	if ((item_size / csum_size) >=
	MAX_CSUM_ITEMS(root, csum_size)) {
	/* already at max size, make a new one */
	goto insert;
	}
	} else {
	int slot = path->slots[0] + 1;
	/* we didn't find a csum item, insert one */
	nritems = btrfs_header_nritems(path->nodes[0]);
	if (path->slots[0] >= nritems - 1) {
	ret = btrfs_next_leaf(root, path);
	if (ret == 1)
	found_next = 1;
	if (ret != 0)
	goto insert;
	slot = 0;
	}
	btrfs_item_key_to_cpu(path->nodes[0], &found_key, slot);
	if (found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID \|\|
	found_key.type != BTRFS_EXTENT_CSUM_KEY) {
	found_next = 1;
	goto insert;
	}
	next_offset = found_key.offset;
	found_next = 1;
	goto insert;
	}

	/*
	* at this point, we know the tree has an item, but it isn't big
	* enough yet to put our csum in. Grow it
	*/
	btrfs_release_path(root, path);
	ret = btrfs_search_slot(trans, root, &file_key, path,
	csum_size, 1);
	if (ret < 0)
	goto fail_unlock;

	if (ret > 0) {
	if (path->slots[0] == 0)
	goto insert;
	path->slots[0]--;
	}

	leaf = path->nodes[0];
	btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
	csum_offset = (bytenr - found_key.offset) >>
	root->fs_info->sb->s_blocksize_bits;

	if (btrfs_key_type(&found_key) != BTRFS_EXTENT_CSUM_KEY \|\|
	found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID \|\|
	csum_offset >= MAX_CSUM_ITEMS(root, csum_size)) {
	goto insert;
	}

	if (csum_offset >= btrfs_item_size_nr(leaf, path->slots[0]) /
	csum_size) {
	u32 diff = (csum_offset + 1) * csum_size;

	/*
	* is the item big enough already? we dropped our lock
	* before and need to recheck
	*/
	if (diff < btrfs_item_size_nr(leaf, path->slots[0]))
	goto csum;

	diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
	if (diff != csum_size)
	goto insert;

	ret = btrfs_extend_item(trans, root, path, diff);
	BUG_ON(ret);
	goto csum;
	}

	insert:
	btrfs_release_path(root, path);
	csum_offset = 0;
	if (found_next) {
	u64 tmp = total_bytes + root->sectorsize;
	u64 next_sector = sector_sum->bytenr;
	struct btrfs_sector_sum *next = sector_sum + 1;

	while (tmp < sums->len) {
	if (next_sector + root->sectorsize != next->bytenr)
	break;
	tmp += root->sectorsize;
	next_sector = next->bytenr;
	next++;
	}
	tmp = min(tmp, next_offset - file_key.offset);
	tmp >>= root->fs_info->sb->s_blocksize_bits;
	tmp = max((u64)1, tmp);
	tmp = min(tmp, (u64)MAX_CSUM_ITEMS(root, csum_size));
	ins_size = csum_size * tmp;
	} else {
	ins_size = csum_size;
	}
	path->leave_spinning = 1;
	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
	ins_size);
	path->leave_spinning = 0;
	if (ret < 0)
	goto fail_unlock;
	if (ret != 0) {
	WARN_ON(1);
	goto fail_unlock;
	}
	csum:
	leaf = path->nodes[0];
	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
	ret = 0;
	item = (struct btrfs_csum_item )((unsigned char )item +
	csum_offset * csum_size);
	found:
	item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
	item_end = (struct btrfs_csum_item )((unsigned char )item_end +
	btrfs_item_size_nr(leaf, path->slots[0]));
	eb_token = NULL;
	next_sector:

	if (!eb_token \|\|
	(unsigned long)item + csum_size >= map_start + map_len) {
	int err;

	if (eb_token)
	unmap_extent_buffer(leaf, eb_token, KM_USER1);
	eb_token = NULL;
	err = map_private_extent_buffer(leaf, (unsigned long)item,
	csum_size,
	&eb_token, &eb_map,
	&map_start, &map_len, KM_USER1);
	if (err)
	eb_token = NULL;
	}
	if (eb_token) {
	memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
	&sector_sum->sum, csum_size);
	} else {
	write_extent_buffer(leaf, &sector_sum->sum,
	(unsigned long)item, csum_size);
	}

	total_bytes += root->sectorsize;
	sector_sum++;
	if (total_bytes < sums->len) {
	item = (struct btrfs_csum_item )((char )item +
	csum_size);
	if (item < item_end && bytenr + PAGE_CACHE_SIZE ==
	sector_sum->bytenr) {
	bytenr = sector_sum->bytenr;
	goto next_sector;
	}
	}
	if (eb_token) {
	unmap_extent_buffer(leaf, eb_token, KM_USER1);
	eb_token = NULL;
	}
	btrfs_mark_buffer_dirty(path->nodes[0]);
	if (total_bytes < sums->len) {
	btrfs_release_path(root, path);
	cond_resched();
	goto again;
	}
	out:
	btrfs_free_path(path);
	return ret;

	fail_unlock:
	goto out;
	}