text: // SPDX-License-Identifier: GPL-2.0
  /*
   * Copyright (C) 2007 Oracle.  All rights reserved.
   */
  
  #include <linux/bio.h>
  #include <linux/slab.h>
  #include <linux/pagemap.h>
  #include <linux/highmem.h>
  #include <linux/sched/mm.h>
  #include <crypto/hash.h>
  #include "misc.h"
  #include "ctree.h"
  #include "disk-io.h"
  #include "transaction.h"
  #include "volumes.h"
  #include "print-tree.h"
  #include "compression.h"
  
  #define __MAX_CSUM_ITEMS(r, size) ((unsigned long)(((BTRFS_LEAF_DATA_SIZE(r) - \
  				   sizeof(struct btrfs_item) * 2) / \
  				  size) - 1))
  
  #define MAX_CSUM_ITEMS(r, size) (min_t(u32, __MAX_CSUM_ITEMS(r, size), \
  				       PAGE_SIZE))
  
  /**
   * Set inode's size according to filesystem options
   *
   * @inode:      inode we want to update the disk_i_size for
   * @new_i_size: i_size we want to set to, 0 if we use i_size
   *
   * With NO_HOLES set this simply sets the disk_is_size to whatever i_size_read()
   * returns as it is perfectly fine with a file that has holes without hole file
   * extent items.
   *
   * However without NO_HOLES we need to only return the area that is contiguous
   * from the 0 offset of the file.  Otherwise we could end up adjust i_size up
   * to an extent that has a gap in between.
   *
   * Finally new_i_size should only be set in the case of truncate where we're not
   * ready to use i_size_read() as the limiter yet.
   */
  void btrfs_inode_safe_disk_i_size_write(struct btrfs_inode *inode, u64 new_i_size)
  {
  	struct btrfs_fs_info *fs_info = inode->root->fs_info;
  	u64 start, end, i_size;
  	int ret;
  
  	i_size = new_i_size ?: i_size_read(&inode->vfs_inode);
  	if (btrfs_fs_incompat(fs_info, NO_HOLES)) {
  		inode->disk_i_size = i_size;
  		return;
  	}
  
  	spin_lock(&inode->lock);
  	ret = find_contiguous_extent_bit(&inode->file_extent_tree, 0, &start,
  					 &end, EXTENT_DIRTY);
  	if (!ret && start == 0)
  		i_size = min(i_size, end + 1);
  	else
  		i_size = 0;
  	inode->disk_i_size = i_size;
  	spin_unlock(&inode->lock);
  }
  
  /**
   * Mark range within a file as having a new extent inserted
   *
   * @inode: inode being modified
   * @start: start file offset of the file extent we've inserted
   * @len:   logical length of the file extent item
   *
   * Call when we are inserting a new file extent where there was none before.
   * Does not need to call this in the case where we're replacing an existing file
   * extent, however if not sure it's fine to call this multiple times.
   *
   * The start and len must match the file extent item, so thus must be sectorsize
   * aligned.
   */
  int btrfs_inode_set_file_extent_range(struct btrfs_inode *inode, u64 start,
  				      u64 len)
  {
  	if (len == 0)
  		return 0;
  
  	ASSERT(IS_ALIGNED(start + len, inode->root->fs_info->sectorsize));
  
  	if (btrfs_fs_incompat(inode->root->fs_info, NO_HOLES))
  		return 0;
  	return set_extent_bits(&inode->file_extent_tree, start, start + len - 1,
  			       EXTENT_DIRTY);
  }
  
  /**
   * Marks an inode range as not having a backing extent
   *
   * @inode: inode being modified
   * @start: start file offset of the file extent we've inserted
   * @len:   logical length of the file extent item
   *
   * Called when we drop a file extent, for example when we truncate.  Doesn't
   * need to be called for cases where we're replacing a file extent, like when
   * we've COWed a file extent.
   *
   * The start and len must match the file extent item, so thus must be sectorsize
   * aligned.
   */
  int btrfs_inode_clear_file_extent_range(struct btrfs_inode *inode, u64 start,
  					u64 len)
  {
  	if (len == 0)
  		return 0;
  
  	ASSERT(IS_ALIGNED(start + len, inode->root->fs_info->sectorsize) ||
  	       len == (u64)-1);
  
  	if (btrfs_fs_incompat(inode->root->fs_info, NO_HOLES))
  		return 0;
  	return clear_extent_bit(&inode->file_extent_tree, start,
  				start + len - 1, EXTENT_DIRTY, 0, 0, NULL);
  }
  
  static inline u32 max_ordered_sum_bytes(struct btrfs_fs_info *fs_info,
  					u16 csum_size)
  {
  	u32 ncsums = (PAGE_SIZE - sizeof(struct btrfs_ordered_sum)) / csum_size;
  
  	return ncsums * fs_info->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();
  	if (!path)
  		return -ENOMEM;
  	file_key.objectid = objectid;
  	file_key.offset = pos;
  	file_key.type = BTRFS_EXTENT_DATA_KEY;
  
  	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  				      sizeof(*item));
  	if (ret < 0)
  		goto out;
  	BUG_ON(ret); /* Can't happen */
  	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;
  }
  
  static struct btrfs_csum_item *
  btrfs_lookup_csum(struct btrfs_trans_handle *trans,
  		  struct btrfs_root *root,
  		  struct btrfs_path *path,
  		  u64 bytenr, int cow)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	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;
  	const u32 csum_size = fs_info->csum_size;
  	int csums_in_item;
  
  	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  	file_key.offset = bytenr;
  	file_key.type = 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 (found_key.type != BTRFS_EXTENT_CSUM_KEY)
  			goto fail;
  
  		csum_offset = (bytenr - found_key.offset) >>
  				fs_info->sectorsize_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;
  		} else if (csum_offset > csums_in_item) {
  			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)
  {
  	struct btrfs_key file_key;
  	int ins_len = mod < 0 ? -1 : 0;
  	int cow = mod != 0;
  
  	file_key.objectid = objectid;
  	file_key.offset = offset;
  	file_key.type = BTRFS_EXTENT_DATA_KEY;
  
  	return btrfs_search_slot(trans, root, &file_key, path, ins_len, cow);
  }
  
  /*
   * Find checksums for logical bytenr range [disk_bytenr, disk_bytenr + len) and
   * estore the result to @dst.
   *
   * Return >0 for the number of sectors we found.
   * Return 0 for the range [disk_bytenr, disk_bytenr + sectorsize) has no csum
   * for it. Caller may want to try next sector until one range is hit.
   * Return <0 for fatal error.
   */
  static int search_csum_tree(struct btrfs_fs_info *fs_info,
  			    struct btrfs_path *path, u64 disk_bytenr,
  			    u64 len, u8 *dst)
  {
  	struct btrfs_csum_item *item = NULL;
  	struct btrfs_key key;
  	const u32 sectorsize = fs_info->sectorsize;
  	const u32 csum_size = fs_info->csum_size;
  	u32 itemsize;
  	int ret;
  	u64 csum_start;
  	u64 csum_len;
  
  	ASSERT(IS_ALIGNED(disk_bytenr, sectorsize) &&
  	       IS_ALIGNED(len, sectorsize));
  
  	/* Check if the current csum item covers disk_bytenr */
  	if (path->nodes[0]) {
  		item = btrfs_item_ptr(path->nodes[0], path->slots[0],
  				      struct btrfs_csum_item);
  		btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
  		itemsize = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
  
  		csum_start = key.offset;
  		csum_len = (itemsize / csum_size) * sectorsize;
  
  		if (in_range(disk_bytenr, csum_start, csum_len))
  			goto found;
  	}
  
  	/* Current item doesn't contain the desired range, search again */
  	btrfs_release_path(path);
  	item = btrfs_lookup_csum(NULL, fs_info->csum_root, path, disk_bytenr, 0);
  	if (IS_ERR(item)) {
  		ret = PTR_ERR(item);
  		goto out;
  	}
  	btrfs_item_key_to_cpu(path->nodes[0], &key, path->slots[0]);
  	itemsize = btrfs_item_size_nr(path->nodes[0], path->slots[0]);
  
  	csum_start = key.offset;
  	csum_len = (itemsize / csum_size) * sectorsize;
  	ASSERT(in_range(disk_bytenr, csum_start, csum_len));
  
  found:
  	ret = (min(csum_start + csum_len, disk_bytenr + len) -
  		   disk_bytenr) >> fs_info->sectorsize_bits;
  	read_extent_buffer(path->nodes[0], dst, (unsigned long)item,
  			ret * csum_size);
  out:
  	if (ret == -ENOENT)
  		ret = 0;
  	return ret;
  }
  
  /*
   * Locate the file_offset of @cur_disk_bytenr of a @bio.
   *
   * Bio of btrfs represents read range of
   * [bi_sector << 9, bi_sector << 9 + bi_size).
   * Knowing this, we can iterate through each bvec to locate the page belong to
   * @cur_disk_bytenr and get the file offset.
   *
   * @inode is used to determine if the bvec page really belongs to @inode.
   *
   * Return 0 if we can't find the file offset
   * Return >0 if we find the file offset and restore it to @file_offset_ret
   */
  static int search_file_offset_in_bio(struct bio *bio, struct inode *inode,
  				     u64 disk_bytenr, u64 *file_offset_ret)
  {
  	struct bvec_iter iter;
  	struct bio_vec bvec;
  	u64 cur = bio->bi_iter.bi_sector << SECTOR_SHIFT;
  	int ret = 0;
  
  	bio_for_each_segment(bvec, bio, iter) {
  		struct page *page = bvec.bv_page;
  
  		if (cur > disk_bytenr)
  			break;
  		if (cur + bvec.bv_len <= disk_bytenr) {
  			cur += bvec.bv_len;
  			continue;
  		}
  		ASSERT(in_range(disk_bytenr, cur, bvec.bv_len));
  		if (page->mapping && page->mapping->host &&
  		    page->mapping->host == inode) {
  			ret = 1;
  			*file_offset_ret = page_offset(page) + bvec.bv_offset +
  					   disk_bytenr - cur;
  			break;
  		}
  	}
  	return ret;
  }
  
  /**
   * Lookup the checksum for the read bio in csum tree.
   *
   * @inode: inode that the bio is for.
   * @bio: bio to look up.
   * @dst: Buffer of size nblocks * btrfs_super_csum_size() used to return
   *       checksum (nblocks = bio->bi_iter.bi_size / fs_info->sectorsize). If
   *       NULL, the checksum buffer is allocated and returned in
   *       btrfs_bio(bio)->csum instead.
   *
   * Return: BLK_STS_RESOURCE if allocating memory fails, BLK_STS_OK otherwise.
   */
  blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio, u8 *dst)
  {
  	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
  	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
  	struct btrfs_path *path;
  	const u32 sectorsize = fs_info->sectorsize;
  	const u32 csum_size = fs_info->csum_size;
  	u32 orig_len = bio->bi_iter.bi_size;
  	u64 orig_disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
  	u64 cur_disk_bytenr;
  	u8 *csum;
  	const unsigned int nblocks = orig_len >> fs_info->sectorsize_bits;
  	int count = 0;
  
  	if (!fs_info->csum_root || (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
  		return BLK_STS_OK;
  
  	/*
  	 * This function is only called for read bio.
  	 *
  	 * This means two things:
  	 * - All our csums should only be in csum tree
  	 *   No ordered extents csums, as ordered extents are only for write
  	 *   path.
  	 * - No need to bother any other info from bvec
  	 *   Since we're looking up csums, the only important info is the
  	 *   disk_bytenr and the length, which can be extracted from bi_iter
  	 *   directly.
  	 */
  	ASSERT(bio_op(bio) == REQ_OP_READ);
  	path = btrfs_alloc_path();
  	if (!path)
  		return BLK_STS_RESOURCE;
  
  	if (!dst) {
  		struct btrfs_bio *bbio = btrfs_bio(bio);
  
  		if (nblocks * csum_size > BTRFS_BIO_INLINE_CSUM_SIZE) {
  			bbio->csum = kmalloc_array(nblocks, csum_size, GFP_NOFS);
  			if (!bbio->csum) {
  				btrfs_free_path(path);
  				return BLK_STS_RESOURCE;
  			}
  		} else {
  			bbio->csum = bbio->csum_inline;
  		}
  		csum = bbio->csum;
  	} else {
  		csum = dst;
  	}
  
  	/*
  	 * If requested number of sectors is larger than one leaf can contain,
  	 * kick the readahead for csum tree.
  	 */
  	if (nblocks > fs_info->csums_per_leaf)
  		path->reada = READA_FORWARD;
  
  	/*
  	 * the free space stuff is only read when it hasn't been
  	 * updated in the current transaction.  So, we can safely
  	 * read from the commit root and sidestep a nasty deadlock
  	 * between reading the free space cache and updating the csum tree.
  	 */
  	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
  		path->search_commit_root = 1;
  		path->skip_locking = 1;
  	}
  
  	for (cur_disk_bytenr = orig_disk_bytenr;
  	     cur_disk_bytenr < orig_disk_bytenr + orig_len;
  	     cur_disk_bytenr += (count * sectorsize)) {
  		u64 search_len = orig_disk_bytenr + orig_len - cur_disk_bytenr;
  		unsigned int sector_offset;
  		u8 *csum_dst;
  
  		/*
  		 * Although both cur_disk_bytenr and orig_disk_bytenr is u64,
  		 * we're calculating the offset to the bio start.
  		 *
  		 * Bio size is limited to UINT_MAX, thus unsigned int is large
  		 * enough to contain the raw result, not to mention the right
  		 * shifted result.
  		 */
  		ASSERT(cur_disk_bytenr - orig_disk_bytenr < UINT_MAX);
  		sector_offset = (cur_disk_bytenr - orig_disk_bytenr) >>
  				fs_info->sectorsize_bits;
  		csum_dst = csum + sector_offset * csum_size;
  
  		count = search_csum_tree(fs_info, path, cur_disk_bytenr,
  					 search_len, csum_dst);
  		if (count <= 0) {
  			/*
  			 * Either we hit a critical error or we didn't find
  			 * the csum.
  			 * Either way, we put zero into the csums dst, and skip
  			 * to the next sector.
  			 */
  			memset(csum_dst, 0, csum_size);
  			count = 1;
  
  			/*
  			 * For data reloc inode, we need to mark the range
  			 * NODATASUM so that balance won't report false csum
  			 * error.
  			 */
  			if (BTRFS_I(inode)->root->root_key.objectid ==
  			    BTRFS_DATA_RELOC_TREE_OBJECTID) {
  				u64 file_offset;
  				int ret;
  
  				ret = search_file_offset_in_bio(bio, inode,
  						cur_disk_bytenr, &file_offset);
  				if (ret)
  					set_extent_bits(io_tree, file_offset,
  						file_offset + sectorsize - 1,
  						EXTENT_NODATASUM);
  			} else {
  				btrfs_warn_rl(fs_info,
  			"csum hole found for disk bytenr range [%llu, %llu)",
  				cur_disk_bytenr, cur_disk_bytenr + sectorsize);
  			}
  		}
  	}
  
  	btrfs_free_path(path);
  	return BLK_STS_OK;
  }
  
  int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
  			     struct list_head *list, int search_commit)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_key key;
  	struct btrfs_path *path;
  	struct extent_buffer *leaf;
  	struct btrfs_ordered_sum *sums;
  	struct btrfs_csum_item *item;
  	LIST_HEAD(tmplist);
  	unsigned long offset;
  	int ret;
  	size_t size;
  	u64 csum_end;
  	const u32 csum_size = fs_info->csum_size;
  
  	ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
  	       IS_ALIGNED(end + 1, fs_info->sectorsize));
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	if (search_commit) {
  		path->skip_locking = 1;
  		path->reada = READA_FORWARD;
  		path->search_commit_root = 1;
  	}
  
  	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) >> fs_info->sectorsize_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 ||
  		    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) * fs_info->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(fs_info, csum_size));
  			sums = kzalloc(btrfs_ordered_sum_size(fs_info, size),
  				       GFP_NOFS);
  			if (!sums) {
  				ret = -ENOMEM;
  				goto fail;
  			}
  
  			sums->bytenr = start;
  			sums->len = (int)size;
  
  			offset = (start - key.offset) >> fs_info->sectorsize_bits;
  			offset *= csum_size;
  			size >>= fs_info->sectorsize_bits;
  
  			read_extent_buffer(path->nodes[0],
  					   sums->sums,
  					   ((unsigned long)item) + offset,
  					   csum_size * size);
  
  			start += fs_info->sectorsize * size;
  			list_add_tail(&sums->list, &tmplist);
  		}
  		path->slots[0]++;
  	}
  	ret = 0;
  fail:
  	while (ret < 0 && !list_empty(&tmplist)) {
  		sums = list_entry(tmplist.next, struct btrfs_ordered_sum, list);
  		list_del(&sums->list);
  		kfree(sums);
  	}
  	list_splice_tail(&tmplist, list);
  
  	btrfs_free_path(path);
  	return ret;
  }
  
  /*
   * btrfs_csum_one_bio - Calculates checksums of the data contained inside a bio
   * @inode:	 Owner of the data inside the bio
   * @bio:	 Contains the data to be checksummed
   * @file_start:  offset in file this bio begins to describe
   * @contig:	 Boolean. If true/1 means all bio vecs in this bio are
   *		 contiguous and they begin at @file_start in the file. False/0
   *		 means this bio can contain potentially discontiguous bio vecs
   *		 so the logical offset of each should be calculated separately.
   */
  blk_status_t btrfs_csum_one_bio(struct btrfs_inode *inode, struct bio *bio,
  		       u64 file_start, int contig)
  {
  	struct btrfs_fs_info *fs_info = inode->root->fs_info;
  	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
  	struct btrfs_ordered_sum *sums;
  	struct btrfs_ordered_extent *ordered = NULL;
  	char *data;
  	struct bvec_iter iter;
  	struct bio_vec bvec;
  	int index;
  	int nr_sectors;
  	unsigned long total_bytes = 0;
  	unsigned long this_sum_bytes = 0;
  	int i;
  	u64 offset;
  	unsigned nofs_flag;
  
  	nofs_flag = memalloc_nofs_save();
  	sums = kvzalloc(btrfs_ordered_sum_size(fs_info, bio->bi_iter.bi_size),
  		       GFP_KERNEL);
  	memalloc_nofs_restore(nofs_flag);
  
  	if (!sums)
  		return BLK_STS_RESOURCE;
  
  	sums->len = bio->bi_iter.bi_size;
  	INIT_LIST_HEAD(&sums->list);
  
  	if (contig)
  		offset = file_start;
  	else
  		offset = 0; /* shut up gcc */
  
  	sums->bytenr = bio->bi_iter.bi_sector << 9;
  	index = 0;
  
  	shash->tfm = fs_info->csum_shash;
  
  	bio_for_each_segment(bvec, bio, iter) {
  		if (!contig)
  			offset = page_offset(bvec.bv_page) + bvec.bv_offset;
  
  		if (!ordered) {
  			ordered = btrfs_lookup_ordered_extent(inode, offset);
  			/*
  			 * The bio range is not covered by any ordered extent,
  			 * must be a code logic error.
  			 */
  			if (unlikely(!ordered)) {
  				WARN(1, KERN_WARNING
  			"no ordered extent for root %llu ino %llu offset %llu\n",
  				     inode->root->root_key.objectid,
  				     btrfs_ino(inode), offset);
  				kvfree(sums);
  				return BLK_STS_IOERR;
  			}
  		}
  
  		nr_sectors = BTRFS_BYTES_TO_BLKS(fs_info,
  						 bvec.bv_len + fs_info->sectorsize
  						 - 1);
  
  		for (i = 0; i < nr_sectors; i++) {
  			if (offset >= ordered->file_offset + ordered->num_bytes ||
  			    offset < ordered->file_offset) {
  				unsigned long bytes_left;
  
  				sums->len = this_sum_bytes;
  				this_sum_bytes = 0;
  				btrfs_add_ordered_sum(ordered, sums);
  				btrfs_put_ordered_extent(ordered);
  
  				bytes_left = bio->bi_iter.bi_size - total_bytes;
  
  				nofs_flag = memalloc_nofs_save();
  				sums = kvzalloc(btrfs_ordered_sum_size(fs_info,
  						      bytes_left), GFP_KERNEL);
  				memalloc_nofs_restore(nofs_flag);
  				BUG_ON(!sums); /* -ENOMEM */
  				sums->len = bytes_left;
  				ordered = btrfs_lookup_ordered_extent(inode,
  								offset);
  				ASSERT(ordered); /* Logic error */
  				sums->bytenr = (bio->bi_iter.bi_sector << 9)
  					+ total_bytes;
  				index = 0;
  			}
  
  			data = bvec_kmap_local(&bvec);
  			crypto_shash_digest(shash,
  					    data + (i * fs_info->sectorsize),
  					    fs_info->sectorsize,
  					    sums->sums + index);
  			kunmap_local(data);
  			index += fs_info->csum_size;
  			offset += fs_info->sectorsize;
  			this_sum_bytes += fs_info->sectorsize;
  			total_bytes += fs_info->sectorsize;
  		}
  
  	}
  	this_sum_bytes = 0;
  	btrfs_add_ordered_sum(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 void truncate_one_csum(struct btrfs_fs_info *fs_info,
  				       struct btrfs_path *path,
  				       struct btrfs_key *key,
  				       u64 bytenr, u64 len)
  {
  	struct extent_buffer *leaf;
  	const u32 csum_size = fs_info->csum_size;
  	u64 csum_end;
  	u64 end_byte = bytenr + len;
  	u32 blocksize_bits = fs_info->sectorsize_bits;
  
  	leaf = path->nodes[0];
  	csum_end = btrfs_item_size_nr(leaf, path->slots[0]) / csum_size;
  	csum_end <<= 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;
  		btrfs_truncate_item(path, new_size, 1);
  	} 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;
  
  		btrfs_truncate_item(path, new_size, 0);
  
  		key->offset = end_byte;
  		btrfs_set_item_key_safe(fs_info, path, key);
  	} else {
  		BUG();
  	}
  }
  
  /*
   * 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_fs_info *fs_info = trans->fs_info;
  	struct btrfs_path *path;
  	struct btrfs_key key;
  	u64 end_byte = bytenr + len;
  	u64 csum_end;
  	struct extent_buffer *leaf;
  	int ret = 0;
  	const u32 csum_size = fs_info->csum_size;
  	u32 blocksize_bits = fs_info->sectorsize_bits;
  
  	ASSERT(root == fs_info->csum_root ||
  	       root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID);
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  
  	while (1) {
  		key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  		key.offset = end_byte - 1;
  		key.type = BTRFS_EXTENT_CSUM_KEY;
  
  		ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
  		if (ret > 0) {
  			ret = 0;
  			if (path->slots[0] == 0)
  				break;
  			path->slots[0]--;
  		} else 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;
  		}
  
  		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) {
  			int del_nr = 1;
  
  			/*
  			 * Check how many csum items preceding this one in this
  			 * leaf correspond to our range and then delete them all
  			 * at once.
  			 */
  			if (key.offset > bytenr && path->slots[0] > 0) {
  				int slot = path->slots[0] - 1;
  
  				while (slot >= 0) {
  					struct btrfs_key pk;
  
  					btrfs_item_key_to_cpu(leaf, &pk, slot);
  					if (pk.offset < bytenr ||
  					    pk.type != BTRFS_EXTENT_CSUM_KEY ||
  					    pk.objectid !=
  					    BTRFS_EXTENT_CSUM_OBJECTID)
  						break;
  					path->slots[0] = slot;
  					del_nr++;
  					key.offset = pk.offset;
  					slot--;
  				}
  			}
  			ret = btrfs_del_items(trans, root, path,
  					      path->slots[0], del_nr);
  			if (ret)
  				break;
  			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]);
  
  			memzero_extent_buffer(leaf, 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);
  			if (ret && ret != -EAGAIN) {
  				btrfs_abort_transaction(trans, ret);
  				break;
  			}
  			ret = 0;
  
  			key.offset = end_byte - 1;
  		} else {
  			truncate_one_csum(fs_info, path, &key, bytenr, len);
  			if (key.offset < bytenr)
  				break;
  		}
  		btrfs_release_path(path);
  	}
  	btrfs_free_path(path);
  	return ret;
  }
  
  static int find_next_csum_offset(struct btrfs_root *root,
  				 struct btrfs_path *path,
  				 u64 *next_offset)
  {
  	const u32 nritems = btrfs_header_nritems(path->nodes[0]);
  	struct btrfs_key found_key;
  	int slot = path->slots[0] + 1;
  	int ret;
  
  	if (nritems == 0 || slot >= nritems) {
  		ret = btrfs_next_leaf(root, path);
  		if (ret < 0) {
  			return ret;
  		} else if (ret > 0) {
  			*next_offset = (u64)-1;
  			return 0;
  		}
  		slot = path->slots[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)
  		*next_offset = (u64)-1;
  	else
  		*next_offset = found_key.offset;
  
  	return 0;
  }
  
  int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
  			   struct btrfs_root *root,
  			   struct btrfs_ordered_sum *sums)
  {
  	struct btrfs_fs_info *fs_info = root->fs_info;
  	struct btrfs_key file_key;
  	struct btrfs_key found_key;
  	struct btrfs_path *path;
  	struct btrfs_csum_item *item;
  	struct btrfs_csum_item *item_end;
  	struct extent_buffer *leaf = NULL;
  	u64 next_offset;
  	u64 total_bytes = 0;
  	u64 csum_offset;
  	u64 bytenr;
  	u32 ins_size;
  	int index = 0;
  	int found_next;
  	int ret;
  	const u32 csum_size = fs_info->csum_size;
  
  	path = btrfs_alloc_path();
  	if (!path)
  		return -ENOMEM;
  again:
  	next_offset = (u64)-1;
  	found_next = 0;
  	bytenr = sums->bytenr + total_bytes;
  	file_key.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
  	file_key.offset = bytenr;
  	file_key.type = BTRFS_EXTENT_CSUM_KEY;
  
  	item = btrfs_lookup_csum(trans, root, path, bytenr, 1);
  	if (!IS_ERR(item)) {
  		ret = 0;
  		leaf = path->nodes[0];
  		item_end = btrfs_item_ptr(leaf, path->slots[0],
  					  struct btrfs_csum_item);
  		item_end = (struct btrfs_csum_item *)((char *)item_end +
  			   btrfs_item_size_nr(leaf, path->slots[0]));
  		goto found;
  	}
  	ret = PTR_ERR(item);
  	if (ret != -EFBIG && ret != -ENOENT)
  		goto out;
  
  	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(fs_info, csum_size)) {
  			/* already at max size, make a new one */
  			goto insert;
  		}
  	} else {
  		/* We didn't find a csum item, insert one. */
  		ret = find_next_csum_offset(root, path, &next_offset);
  		if (ret < 0)
  			goto out;
  		found_next = 1;
  		goto insert;
  	}
  
  	/*
  	 * At this point, we know the tree has a checksum item that ends at an
  	 * offset matching the start of the checksum range we want to insert.
  	 * We try to extend that item as much as possible and then add as many
  	 * checksums to it as they fit.
  	 *
  	 * First check if the leaf has enough free space for at least one
  	 * checksum. If it has go directly to the item extension code, otherwise
  	 * release the path and do a search for insertion before the extension.
  	 */
  	if (btrfs_leaf_free_space(leaf) >= csum_size) {
  		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
  		csum_offset = (bytenr - found_key.offset) >>
  			fs_info->sectorsize_bits;
  		goto extend_csum;
  	}
  
  	btrfs_release_path(path);
  	path->search_for_extension = 1;
  	ret = btrfs_search_slot(trans, root, &file_key, path,
  				csum_size, 1);
  	path->search_for_extension = 0;
  	if (ret < 0)
  		goto out;
  
  	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) >> fs_info->sectorsize_bits;
  
  	if (found_key.type != BTRFS_EXTENT_CSUM_KEY ||
  	    found_key.objectid != BTRFS_EXTENT_CSUM_OBJECTID ||
  	    csum_offset >= MAX_CSUM_ITEMS(fs_info, csum_size)) {
  		goto insert;
  	}
  
  extend_csum:
  	if (csum_offset == btrfs_item_size_nr(leaf, path->slots[0]) /
  	    csum_size) {
  		int extend_nr;
  		u64 tmp;
  		u32 diff;
  
  		tmp = sums->len - total_bytes;
  		tmp >>= fs_info->sectorsize_bits;
  		WARN_ON(tmp < 1);
  		extend_nr = max_t(int, 1, tmp);
  
  		/*
  		 * A log tree can already have checksum items with a subset of
  		 * the checksums we are trying to log. This can happen after
  		 * doing a sequence of partial writes into prealloc extents and
  		 * fsyncs in between, with a full fsync logging a larger subrange
  		 * of an extent for which a previous fast fsync logged a smaller
  		 * subrange. And this happens in particular due to merging file
  		 * extent items when we complete an ordered extent for a range
  		 * covered by a prealloc extent - this is done at
  		 * btrfs_mark_extent_written().
  		 *
  		 * So if we try to extend the previous checksum item, which has
  		 * a range that ends at the start of the range we want to insert,
  		 * make sure we don't extend beyond the start offset of the next
  		 * checksum item. If we are at the last item in the leaf, then
  		 * forget the optimization of extending and add a new checksum
  		 * item - it is not worth the complexity of releasing the path,
  		 * getting the first key for the next leaf, repeat the btree
  		 * search, etc, because log trees are temporary anyway and it
  		 * would only save a few bytes of leaf space.
  		 */
  		if (root->root_key.objectid == BTRFS_TREE_LOG_OBJECTID) {
  			if (path->slots[0] + 1 >=
  			    btrfs_header_nritems(path->nodes[0])) {
  				ret = find_next_csum_offset(root, path, &next_offset);
  				if (ret < 0)
  					goto out;
  				found_next = 1;
  				goto insert;
  			}
  
  			ret = find_next_csum_offset(root, path, &next_offset);
  			if (ret < 0)
  				goto out;
  
  			tmp = (next_offset - bytenr) >> fs_info->sectorsize_bits;
  			if (tmp <= INT_MAX)
  				extend_nr = min_t(int, extend_nr, tmp);
  		}
  
  		diff = (csum_offset + extend_nr) * csum_size;
  		diff = min(diff,
  			   MAX_CSUM_ITEMS(fs_info, csum_size) * csum_size);
  
  		diff = diff - btrfs_item_size_nr(leaf, path->slots[0]);
  		diff = min_t(u32, btrfs_leaf_free_space(leaf), diff);
  		diff /= csum_size;
  		diff *= csum_size;
  
  		btrfs_extend_item(path, diff);
  		ret = 0;
  		goto csum;
  	}
  
  insert:
  	btrfs_release_path(path);
  	csum_offset = 0;
  	if (found_next) {
  		u64 tmp;
  
  		tmp = sums->len - total_bytes;
  		tmp >>= fs_info->sectorsize_bits;
  		tmp = min(tmp, (next_offset - file_key.offset) >>
  					 fs_info->sectorsize_bits);
  
  		tmp = max_t(u64, 1, tmp);
  		tmp = min_t(u64, tmp, MAX_CSUM_ITEMS(fs_info, csum_size));
  		ins_size = csum_size * tmp;
  	} else {
  		ins_size = csum_size;
  	}
  	ret = btrfs_insert_empty_item(trans, root, path, &file_key,
  				      ins_size);
  	if (ret < 0)
  		goto out;
  	if (WARN_ON(ret != 0))
  		goto out;
  	leaf = path->nodes[0];
  csum:
  	item = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
  	item_end = (struct btrfs_csum_item *)((unsigned char *)item +
  				      btrfs_item_size_nr(leaf, path->slots[0]));
  	item = (struct btrfs_csum_item *)((unsigned char *)item +
  					  csum_offset * csum_size);
  found:
  	ins_size = (u32)(sums->len - total_bytes) >> fs_info->sectorsize_bits;
  	ins_size *= csum_size;
  	ins_size = min_t(u32, (unsigned long)item_end - (unsigned long)item,
  			      ins_size);
  	write_extent_buffer(leaf, sums->sums + index, (unsigned long)item,
  			    ins_size);
  
  	index += ins_size;
  	ins_size /= csum_size;
  	total_bytes += ins_size * fs_info->sectorsize;
  
  	btrfs_mark_buffer_dirty(path->nodes[0]);
  	if (total_bytes < sums->len) {
  		btrfs_release_path(path);
  		cond_resched();
  		goto again;
  	}
  out:
  	btrfs_free_path(path);
  	return ret;
  }
  
  void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
  				     const struct btrfs_path *path,
  				     struct btrfs_file_extent_item *fi,
  				     const bool new_inline,
  				     struct extent_map *em)
  {
  	struct btrfs_fs_info *fs_info = inode->root->fs_info;
  	struct btrfs_root *root = inode->root;
  	struct extent_buffer *leaf = path->nodes[0];
  	const int slot = path->slots[0];
  	struct btrfs_key key;
  	u64 extent_start, extent_end;
  	u64 bytenr;
  	u8 type = btrfs_file_extent_type(leaf, fi);
  	int compress_type = btrfs_file_extent_compression(leaf, fi);
  
  	btrfs_item_key_to_cpu(leaf, &key, slot);
  	extent_start = key.offset;
  	extent_end = btrfs_file_extent_end(path);
  	em->ram_bytes = btrfs_file_extent_ram_bytes(leaf, fi);
  	if (type == BTRFS_FILE_EXTENT_REG ||
  	    type == BTRFS_FILE_EXTENT_PREALLOC) {
  		em->start = extent_start;
  		em->len = extent_end - extent_start;
  		em->orig_start = extent_start -
  			btrfs_file_extent_offset(leaf, fi);
  		em->orig_block_len = btrfs_file_extent_disk_num_bytes(leaf, fi);
  		bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
  		if (bytenr == 0) {
  			em->block_start = EXTENT_MAP_HOLE;
  			return;
  		}
  		if (compress_type != BTRFS_COMPRESS_NONE) {
  			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
  			em->compress_type = compress_type;
  			em->block_start = bytenr;
  			em->block_len = em->orig_block_len;
  		} else {
  			bytenr += btrfs_file_extent_offset(leaf, fi);
  			em->block_start = bytenr;
  			em->block_len = em->len;
  			if (type == BTRFS_FILE_EXTENT_PREALLOC)
  				set_bit(EXTENT_FLAG_PREALLOC, &em->flags);
  		}
  	} else if (type == BTRFS_FILE_EXTENT_INLINE) {
  		em->block_start = EXTENT_MAP_INLINE;
  		em->start = extent_start;
  		em->len = extent_end - extent_start;
  		/*
  		 * Initialize orig_start and block_len with the same values
  		 * as in inode.c:btrfs_get_extent().
  		 */
  		em->orig_start = EXTENT_MAP_HOLE;
  		em->block_len = (u64)-1;
  		if (!new_inline && compress_type != BTRFS_COMPRESS_NONE) {
  			set_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
  			em->compress_type = compress_type;
  		}
  	} else {
  		btrfs_err(fs_info,
  			  "unknown file extent item type %d, inode %llu, offset %llu, "
  			  "root %llu", type, btrfs_ino(inode), extent_start,
  			  root->root_key.objectid);
  	}
  }
  
  /*
   * Returns the end offset (non inclusive) of the file extent item the given path
   * points to. If it points to an inline extent, the returned offset is rounded
   * up to the sector size.
   */
  u64 btrfs_file_extent_end(const struct btrfs_path *path)
  {
  	const struct extent_buffer *leaf = path->nodes[0];
  	const int slot = path->slots[0];
  	struct btrfs_file_extent_item *fi;
  	struct btrfs_key key;
  	u64 end;
  
  	btrfs_item_key_to_cpu(leaf, &key, slot);
  	ASSERT(key.type == BTRFS_EXTENT_DATA_KEY);
  	fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
  
  	if (btrfs_file_extent_type(leaf, fi) == BTRFS_FILE_EXTENT_INLINE) {
  		end = btrfs_file_extent_ram_bytes(leaf, fi);
  		end = ALIGN(key.offset + end, leaf->fs_info->sectorsize);
  	} else {
  		end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
  	}
  
  	return end;
  }
  