[mirror_ubuntu-zesty-kernel.git] / fs / btrfs / compression.c

/*
 * Copyright (C) 2008 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/kernel.h>
#include <linux/bio.h>
#include <linux/buffer_head.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/smp_lock.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/bit_spinlock.h>
#include <linux/version.h>
#include <linux/pagevec.h>
#include "compat.h"
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "volumes.h"
#include "ordered-data.h"
#include "compression.h"
#include "extent_io.h"
#include "extent_map.h"

struct compressed_bio {
	/* number of bios pending for this compressed extent */
	atomic_t pending_bios;

	/* the pages with the compressed data on them */
	struct page **compressed_pages;

	/* inode that owns this data */
	struct inode *inode;

	/* starting offset in the inode for our pages */
	u64 start;

	/* number of bytes in the inode we're working on */
	unsigned long len;

	/* number of bytes on disk */
	unsigned long compressed_len;

	/* number of compressed pages in the array */
	unsigned long nr_pages;

	/* IO errors */
	int errors;
	int mirror_num;

	/* for reads, this is the bio we are copying the data into */
	struct bio *orig_bio;

	/*
	 * the start of a variable length array of checksums only
	 * used by reads
	 */
	u32 sums;
};

static inline int compressed_bio_size(struct btrfs_root *root,
				      unsigned long disk_size)
{
	u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
	return sizeof(struct compressed_bio) +
		((disk_size + root->sectorsize - 1) / root->sectorsize) *
		csum_size;
}

static struct bio *compressed_bio_alloc(struct block_device *bdev,
					u64 first_byte, gfp_t gfp_flags)
{
	struct bio *bio;
	int nr_vecs;

	nr_vecs = bio_get_nr_vecs(bdev);
	bio = bio_alloc(gfp_flags, nr_vecs);

	if (bio == NULL && (current->flags & PF_MEMALLOC)) {
		while (!bio && (nr_vecs /= 2))
			bio = bio_alloc(gfp_flags, nr_vecs);
	}

	if (bio) {
		bio->bi_size = 0;
		bio->bi_bdev = bdev;
		bio->bi_sector = first_byte >> 9;
	}
	return bio;
}

static int check_compressed_csum(struct inode *inode,
				 struct compressed_bio *cb,
				 u64 disk_start)
{
	int ret;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct page *page;
	unsigned long i;
	char *kaddr;
	u32 csum;
	u32 *cb_sum = &cb->sums;

	if (btrfs_test_flag(inode, NODATASUM))
		return 0;

	for (i = 0; i < cb->nr_pages; i++) {
		page = cb->compressed_pages[i];
		csum = ~(u32)0;

		kaddr = kmap_atomic(page, KM_USER0);
		csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
		btrfs_csum_final(csum, (char *)&csum);
		kunmap_atomic(kaddr, KM_USER0);

		if (csum != *cb_sum) {
			printk(KERN_INFO "btrfs csum failed ino %lu "
			       "extent %llu csum %u "
			       "wanted %u mirror %d\n", inode->i_ino,
			       (unsigned long long)disk_start,
			       csum, *cb_sum, cb->mirror_num);
			ret = -EIO;
			goto fail;
		}
		cb_sum++;

	}
	ret = 0;
fail:
	return ret;
}

/* when we finish reading compressed pages from the disk, we
 * decompress them and then run the bio end_io routines on the
 * decompressed pages (in the inode address space).
 *
 * This allows the checksumming and other IO error handling routines
 * to work normally
 *
 * The compressed pages are freed here, and it must be run
 * in process context
 */
static void end_compressed_bio_read(struct bio *bio, int err)
{
	struct extent_io_tree *tree;
	struct compressed_bio *cb = bio->bi_private;
	struct inode *inode;
	struct page *page;
	unsigned long index;
	int ret;

	if (err)
		cb->errors = 1;

	/* if there are more bios still pending for this compressed
	 * extent, just exit
	 */
	if (!atomic_dec_and_test(&cb->pending_bios))
		goto out;

	inode = cb->inode;
	ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
	if (ret)
		goto csum_failed;

	/* ok, we're the last bio for this extent, lets start
	 * the decompression.
	 */
	tree = &BTRFS_I(inode)->io_tree;
	ret = btrfs_zlib_decompress_biovec(cb->compressed_pages,
					cb->start,
					cb->orig_bio->bi_io_vec,
					cb->orig_bio->bi_vcnt,
					cb->compressed_len);
csum_failed:
	if (ret)
		cb->errors = 1;

	/* release the compressed pages */
	index = 0;
	for (index = 0; index < cb->nr_pages; index++) {
		page = cb->compressed_pages[index];
		page->mapping = NULL;
		page_cache_release(page);
	}

	/* do io completion on the original bio */
	if (cb->errors) {
		bio_io_error(cb->orig_bio);
	} else {
		int bio_index = 0;
		struct bio_vec *bvec = cb->orig_bio->bi_io_vec;

		/*
		 * we have verified the checksum already, set page
		 * checked so the end_io handlers know about it
		 */
		while (bio_index < cb->orig_bio->bi_vcnt) {
			SetPageChecked(bvec->bv_page);
			bvec++;
			bio_index++;
		}
		bio_endio(cb->orig_bio, 0);
	}

	/* finally free the cb struct */
	kfree(cb->compressed_pages);
	kfree(cb);
out:
	bio_put(bio);
}

/*
 * Clear the writeback bits on all of the file
 * pages for a compressed write
 */
static noinline int end_compressed_writeback(struct inode *inode, u64 start,
					     unsigned long ram_size)
{
	unsigned long index = start >> PAGE_CACHE_SHIFT;
	unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
	struct page *pages[16];
	unsigned long nr_pages = end_index - index + 1;
	int i;
	int ret;

	while (nr_pages > 0) {
		ret = find_get_pages_contig(inode->i_mapping, index,
				     min_t(unsigned long,
				     nr_pages, ARRAY_SIZE(pages)), pages);
		if (ret == 0) {
			nr_pages -= 1;
			index += 1;
			continue;
		}
		for (i = 0; i < ret; i++) {
			end_page_writeback(pages[i]);
			page_cache_release(pages[i]);
		}
		nr_pages -= ret;
		index += ret;
	}
	/* the inode may be gone now */
	return 0;
}

/*
 * do the cleanup once all the compressed pages hit the disk.
 * This will clear writeback on the file pages and free the compressed
 * pages.
 *
 * This also calls the writeback end hooks for the file pages so that
 * metadata and checksums can be updated in the file.
 */
static void end_compressed_bio_write(struct bio *bio, int err)
{
	struct extent_io_tree *tree;
	struct compressed_bio *cb = bio->bi_private;
	struct inode *inode;
	struct page *page;
	unsigned long index;

	if (err)
		cb->errors = 1;

	/* if there are more bios still pending for this compressed
	 * extent, just exit
	 */
	if (!atomic_dec_and_test(&cb->pending_bios))
		goto out;

	/* ok, we're the last bio for this extent, step one is to
	 * call back into the FS and do all the end_io operations
	 */
	inode = cb->inode;
	tree = &BTRFS_I(inode)->io_tree;
	cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
	tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
					 cb->start,
					 cb->start + cb->len - 1,
					 NULL, 1);
	cb->compressed_pages[0]->mapping = NULL;

	end_compressed_writeback(inode, cb->start, cb->len);
	/* note, our inode could be gone now */

	/*
	 * release the compressed pages, these came from alloc_page and
	 * are not attached to the inode at all
	 */
	index = 0;
	for (index = 0; index < cb->nr_pages; index++) {
		page = cb->compressed_pages[index];
		page->mapping = NULL;
		page_cache_release(page);
	}

	/* finally free the cb struct */
	kfree(cb->compressed_pages);
	kfree(cb);
out:
	bio_put(bio);
}

/*
 * worker function to build and submit bios for previously compressed pages.
 * The corresponding pages in the inode should be marked for writeback
 * and the compressed pages should have a reference on them for dropping
 * when the IO is complete.
 *
 * This also checksums the file bytes and gets things ready for
 * the end io hooks.
 */
int btrfs_submit_compressed_write(struct inode *inode, u64 start,
				 unsigned long len, u64 disk_start,
				 unsigned long compressed_len,
				 struct page **compressed_pages,
				 unsigned long nr_pages)
{
	struct bio *bio = NULL;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	struct compressed_bio *cb;
	unsigned long bytes_left;
	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
	int page_index = 0;
	struct page *page;
	u64 first_byte = disk_start;
	struct block_device *bdev;
	int ret;

	WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
	atomic_set(&cb->pending_bios, 0);
	cb->errors = 0;
	cb->inode = inode;
	cb->start = start;
	cb->len = len;
	cb->mirror_num = 0;
	cb->compressed_pages = compressed_pages;
	cb->compressed_len = compressed_len;
	cb->orig_bio = NULL;
	cb->nr_pages = nr_pages;

	bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;

	bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
	bio->bi_private = cb;
	bio->bi_end_io = end_compressed_bio_write;
	atomic_inc(&cb->pending_bios);

	/* create and submit bios for the compressed pages */
	bytes_left = compressed_len;
	for (page_index = 0; page_index < cb->nr_pages; page_index++) {
		page = compressed_pages[page_index];
		page->mapping = inode->i_mapping;
		if (bio->bi_size)
			ret = io_tree->ops->merge_bio_hook(page, 0,
							   PAGE_CACHE_SIZE,
							   bio, 0);
		else
			ret = 0;

		page->mapping = NULL;
		if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
		    PAGE_CACHE_SIZE) {
			bio_get(bio);

			/*
			 * inc the count before we submit the bio so
			 * we know the end IO handler won't happen before
			 * we inc the count.  Otherwise, the cb might get
			 * freed before we're done setting it up
			 */
			atomic_inc(&cb->pending_bios);
			ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
			BUG_ON(ret);

			ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
			BUG_ON(ret);

			ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
			BUG_ON(ret);

			bio_put(bio);

			bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
			bio->bi_private = cb;
			bio->bi_end_io = end_compressed_bio_write;
			bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
		}
		if (bytes_left < PAGE_CACHE_SIZE) {
			printk("bytes left %lu compress len %lu nr %lu\n",
			       bytes_left, cb->compressed_len, cb->nr_pages);
		}
		bytes_left -= PAGE_CACHE_SIZE;
		first_byte += PAGE_CACHE_SIZE;
		cond_resched();
	}
	bio_get(bio);

	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
	BUG_ON(ret);

	ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
	BUG_ON(ret);

	ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
	BUG_ON(ret);

	bio_put(bio);
	return 0;
}

static noinline int add_ra_bio_pages(struct inode *inode,
				     u64 compressed_end,
				     struct compressed_bio *cb)
{
	unsigned long end_index;
	unsigned long page_index;
	u64 last_offset;
	u64 isize = i_size_read(inode);
	int ret;
	struct page *page;
	unsigned long nr_pages = 0;
	struct extent_map *em;
	struct address_space *mapping = inode->i_mapping;
	struct pagevec pvec;
	struct extent_map_tree *em_tree;
	struct extent_io_tree *tree;
	u64 end;
	int misses = 0;

	page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
	last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
	em_tree = &BTRFS_I(inode)->extent_tree;
	tree = &BTRFS_I(inode)->io_tree;

	if (isize == 0)
		return 0;

	end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;

	pagevec_init(&pvec, 0);
	while (last_offset < compressed_end) {
		page_index = last_offset >> PAGE_CACHE_SHIFT;

		if (page_index > end_index)
			break;

		rcu_read_lock();
		page = radix_tree_lookup(&mapping->page_tree, page_index);
		rcu_read_unlock();
		if (page) {
			misses++;
			if (misses > 4)
				break;
			goto next;
		}

		page = alloc_page(mapping_gfp_mask(mapping) | GFP_NOFS);
		if (!page)
			break;

		page->index = page_index;
		/*
		 * what we want to do here is call add_to_page_cache_lru,
		 * but that isn't exported, so we reproduce it here
		 */
		if (add_to_page_cache(page, mapping,
				      page->index, GFP_NOFS)) {
			page_cache_release(page);
			goto next;
		}

		/* open coding of lru_cache_add, also not exported */
		page_cache_get(page);
		if (!pagevec_add(&pvec, page))
			__pagevec_lru_add_file(&pvec);

		end = last_offset + PAGE_CACHE_SIZE - 1;
		/*
		 * at this point, we have a locked page in the page cache
		 * for these bytes in the file.  But, we have to make
		 * sure they map to this compressed extent on disk.
		 */
		set_page_extent_mapped(page);
		lock_extent(tree, last_offset, end, GFP_NOFS);
		spin_lock(&em_tree->lock);
		em = lookup_extent_mapping(em_tree, last_offset,
					   PAGE_CACHE_SIZE);
		spin_unlock(&em_tree->lock);

		if (!em || last_offset < em->start ||
		    (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
		    (em->block_start >> 9) != cb->orig_bio->bi_sector) {
			free_extent_map(em);
			unlock_extent(tree, last_offset, end, GFP_NOFS);
			unlock_page(page);
			page_cache_release(page);
			break;
		}
		free_extent_map(em);

		if (page->index == end_index) {
			char *userpage;
			size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);

			if (zero_offset) {
				int zeros;
				zeros = PAGE_CACHE_SIZE - zero_offset;
				userpage = kmap_atomic(page, KM_USER0);
				memset(userpage + zero_offset, 0, zeros);
				flush_dcache_page(page);
				kunmap_atomic(userpage, KM_USER0);
			}
		}

		ret = bio_add_page(cb->orig_bio, page,
				   PAGE_CACHE_SIZE, 0);

		if (ret == PAGE_CACHE_SIZE) {
			nr_pages++;
			page_cache_release(page);
		} else {
			unlock_extent(tree, last_offset, end, GFP_NOFS);
			unlock_page(page);
			page_cache_release(page);
			break;
		}
next:
		last_offset += PAGE_CACHE_SIZE;
	}
	if (pagevec_count(&pvec))
		__pagevec_lru_add_file(&pvec);
	return 0;
}

/*
 * for a compressed read, the bio we get passed has all the inode pages
 * in it.  We don't actually do IO on those pages but allocate new ones
 * to hold the compressed pages on disk.
 *
 * bio->bi_sector points to the compressed extent on disk
 * bio->bi_io_vec points to all of the inode pages
 * bio->bi_vcnt is a count of pages
 *
 * After the compressed pages are read, we copy the bytes into the
 * bio we were passed and then call the bio end_io calls
 */
int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
				 int mirror_num, unsigned long bio_flags)
{
	struct extent_io_tree *tree;
	struct extent_map_tree *em_tree;
	struct compressed_bio *cb;
	struct btrfs_root *root = BTRFS_I(inode)->root;
	unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
	unsigned long compressed_len;
	unsigned long nr_pages;
	unsigned long page_index;
	struct page *page;
	struct block_device *bdev;
	struct bio *comp_bio;
	u64 cur_disk_byte = (u64)bio->bi_sector << 9;
	u64 em_len;
	u64 em_start;
	struct extent_map *em;
	int ret;
	u32 *sums;

	tree = &BTRFS_I(inode)->io_tree;
	em_tree = &BTRFS_I(inode)->extent_tree;

	/* we need the actual starting offset of this extent in the file */
	spin_lock(&em_tree->lock);
	em = lookup_extent_mapping(em_tree,
				   page_offset(bio->bi_io_vec->bv_page),
				   PAGE_CACHE_SIZE);
	spin_unlock(&em_tree->lock);

	compressed_len = em->block_len;
	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
	atomic_set(&cb->pending_bios, 0);
	cb->errors = 0;
	cb->inode = inode;
	cb->mirror_num = mirror_num;
	sums = &cb->sums;

	cb->start = em->orig_start;
	em_len = em->len;
	em_start = em->start;

	free_extent_map(em);
	em = NULL;

	cb->len = uncompressed_len;
	cb->compressed_len = compressed_len;
	cb->orig_bio = bio;

	nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
				 PAGE_CACHE_SIZE;
	cb->compressed_pages = kmalloc(sizeof(struct page *) * nr_pages,
				       GFP_NOFS);
	bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;

	for (page_index = 0; page_index < nr_pages; page_index++) {
		cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
							      __GFP_HIGHMEM);
	}
	cb->nr_pages = nr_pages;

	add_ra_bio_pages(inode, em_start + em_len, cb);

	/* include any pages we added in add_ra-bio_pages */
	uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
	cb->len = uncompressed_len;

	comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
	comp_bio->bi_private = cb;
	comp_bio->bi_end_io = end_compressed_bio_read;
	atomic_inc(&cb->pending_bios);

	for (page_index = 0; page_index < nr_pages; page_index++) {
		page = cb->compressed_pages[page_index];
		page->mapping = inode->i_mapping;
		page->index = em_start >> PAGE_CACHE_SHIFT;

		if (comp_bio->bi_size)
			ret = tree->ops->merge_bio_hook(page, 0,
							PAGE_CACHE_SIZE,
							comp_bio, 0);
		else
			ret = 0;

		page->mapping = NULL;
		if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
		    PAGE_CACHE_SIZE) {
			bio_get(comp_bio);

			ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
			BUG_ON(ret);

			/*
			 * inc the count before we submit the bio so
			 * we know the end IO handler won't happen before
			 * we inc the count.  Otherwise, the cb might get
			 * freed before we're done setting it up
			 */
			atomic_inc(&cb->pending_bios);

			if (!btrfs_test_flag(inode, NODATASUM)) {
				btrfs_lookup_bio_sums(root, inode, comp_bio,
						      sums);
			}
			sums += (comp_bio->bi_size + root->sectorsize - 1) /
				root->sectorsize;

			ret = btrfs_map_bio(root, READ, comp_bio,
					    mirror_num, 0);
			BUG_ON(ret);

			bio_put(comp_bio);

			comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
							GFP_NOFS);
			comp_bio->bi_private = cb;
			comp_bio->bi_end_io = end_compressed_bio_read;

			bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
		}
		cur_disk_byte += PAGE_CACHE_SIZE;
	}
	bio_get(comp_bio);

	ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
	BUG_ON(ret);

	if (!btrfs_test_flag(inode, NODATASUM))
		btrfs_lookup_bio_sums(root, inode, comp_bio, sums);

	ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
	BUG_ON(ret);

	bio_put(comp_bio);
	return 0;
}
Commit	Line	Data
c8b97818 CM	1	/*
	2	* Copyright (C) 2008 Oracle. All rights reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or
	5	* modify it under the terms of the GNU General Public
	6	* License v2 as published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful,
	9	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	11	* General Public License for more details.
	12	*
	13	* You should have received a copy of the GNU General Public
	14	* License along with this program; if not, write to the
	15	* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	16	* Boston, MA 021110-1307, USA.
	17	*/
	18
	19	#include <linux/kernel.h>
	20	#include <linux/bio.h>
	21	#include <linux/buffer_head.h>
	22	#include <linux/file.h>
	23	#include <linux/fs.h>
	24	#include <linux/pagemap.h>
	25	#include <linux/highmem.h>
	26	#include <linux/time.h>
	27	#include <linux/init.h>
	28	#include <linux/string.h>
	29	#include <linux/smp_lock.h>
	30	#include <linux/backing-dev.h>
	31	#include <linux/mpage.h>
	32	#include <linux/swap.h>
	33	#include <linux/writeback.h>
	34	#include <linux/bit_spinlock.h>
	35	#include <linux/version.h>
771ed689	36	#include <linux/pagevec.h>
4b4e25f2	37	#include "compat.h"
c8b97818 CM	38	#include "ctree.h"
	39	#include "disk-io.h"
	40	#include "transaction.h"
	41	#include "btrfs_inode.h"
	42	#include "volumes.h"
	43	#include "ordered-data.h"
c8b97818 CM	44	#include "compression.h"
	45	#include "extent_io.h"
	46	#include "extent_map.h"
	47
	48	struct compressed_bio {
	49	/* number of bios pending for this compressed extent */
	50	atomic_t pending_bios;
	51
	52	/* the pages with the compressed data on them */
	53	struct page **compressed_pages;
	54
	55	/* inode that owns this data */
	56	struct inode *inode;
	57
	58	/* starting offset in the inode for our pages */
	59	u64 start;
	60
	61	/* number of bytes in the inode we're working on */
	62	unsigned long len;
	63
	64	/* number of bytes on disk */
	65	unsigned long compressed_len;
	66
	67	/* number of compressed pages in the array */
	68	unsigned long nr_pages;
	69
	70	/* IO errors */
	71	int errors;
d20f7043	72	int mirror_num;
c8b97818 CM	73
	74	/* for reads, this is the bio we are copying the data into */
	75	struct bio *orig_bio;
d20f7043 CM	76
	77	/*
	78	* the start of a variable length array of checksums only
	79	* used by reads
	80	*/
	81	u32 sums;
c8b97818 CM	82	};
c8b97818 CM	83
d20f7043 CM	84	static inline int compressed_bio_size(struct btrfs_root *root,
	85	unsigned long disk_size)
	86	{
	87	u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
	88	return sizeof(struct compressed_bio) +
	89	((disk_size + root->sectorsize - 1) / root->sectorsize) *
	90	csum_size;
	91	}
	92
c8b97818 CM	93	static struct bio compressed_bio_alloc(struct block_device bdev,
	94	u64 first_byte, gfp_t gfp_flags)
	95	{
	96	struct bio *bio;
	97	int nr_vecs;
	98
	99	nr_vecs = bio_get_nr_vecs(bdev);
	100	bio = bio_alloc(gfp_flags, nr_vecs);
	101
	102	if (bio == NULL && (current->flags & PF_MEMALLOC)) {
	103	while (!bio && (nr_vecs /= 2))
	104	bio = bio_alloc(gfp_flags, nr_vecs);
	105	}
	106
	107	if (bio) {
	108	bio->bi_size = 0;
	109	bio->bi_bdev = bdev;
	110	bio->bi_sector = first_byte >> 9;
	111	}
	112	return bio;
	113	}
	114
d20f7043 CM	115	static int check_compressed_csum(struct inode *inode,
	116	struct compressed_bio *cb,
	117	u64 disk_start)
	118	{
	119	int ret;
	120	struct btrfs_root *root = BTRFS_I(inode)->root;
	121	struct page *page;
	122	unsigned long i;
	123	char *kaddr;
	124	u32 csum;
	125	u32 *cb_sum = &cb->sums;
	126
17d217fe	127	if (btrfs_test_flag(inode, NODATASUM))
d20f7043 CM	128	return 0;
	129
	130	for (i = 0; i < cb->nr_pages; i++) {
	131	page = cb->compressed_pages[i];
	132	csum = ~(u32)0;
	133
	134	kaddr = kmap_atomic(page, KM_USER0);
	135	csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
	136	btrfs_csum_final(csum, (char *)&csum);
	137	kunmap_atomic(kaddr, KM_USER0);
	138
	139	if (csum != *cb_sum) {
d397712b CM	140	printk(KERN_INFO "btrfs csum failed ino %lu "
d397712b CM	141	"extent %llu csum %u "
d20f7043 CM	142	"wanted %u mirror %d\n", inode->i_ino,
	143	(unsigned long long)disk_start,
	144	csum, *cb_sum, cb->mirror_num);
	145	ret = -EIO;
	146	goto fail;
	147	}
	148	cb_sum++;
	149
	150	}
	151	ret = 0;
	152	fail:
	153	return ret;
	154	}
	155
c8b97818 CM	156	/* when we finish reading compressed pages from the disk, we
	157	* decompress them and then run the bio end_io routines on the
	158	* decompressed pages (in the inode address space).
	159	*
	160	* This allows the checksumming and other IO error handling routines
	161	* to work normally
	162	*
	163	* The compressed pages are freed here, and it must be run
	164	* in process context
	165	*/
	166	static void end_compressed_bio_read(struct bio *bio, int err)
	167	{
	168	struct extent_io_tree *tree;
	169	struct compressed_bio *cb = bio->bi_private;
	170	struct inode *inode;
	171	struct page *page;
	172	unsigned long index;
	173	int ret;
	174
	175	if (err)
	176	cb->errors = 1;
	177
	178	/* if there are more bios still pending for this compressed
	179	* extent, just exit
	180	*/
	181	if (!atomic_dec_and_test(&cb->pending_bios))
	182	goto out;
	183
d20f7043 CM	184	inode = cb->inode;
	185	ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
	186	if (ret)
	187	goto csum_failed;
	188
c8b97818 CM	189	/* ok, we're the last bio for this extent, lets start
	190	* the decompression.
	191	*/
c8b97818 CM	192	tree = &BTRFS_I(inode)->io_tree;
	193	ret = btrfs_zlib_decompress_biovec(cb->compressed_pages,
	194	cb->start,
	195	cb->orig_bio->bi_io_vec,
	196	cb->orig_bio->bi_vcnt,
	197	cb->compressed_len);
d20f7043	198	csum_failed:
c8b97818 CM	199	if (ret)
	200	cb->errors = 1;
	201
	202	/* release the compressed pages */
	203	index = 0;
	204	for (index = 0; index < cb->nr_pages; index++) {
	205	page = cb->compressed_pages[index];
	206	page->mapping = NULL;
	207	page_cache_release(page);
	208	}
	209
	210	/* do io completion on the original bio */
771ed689	211	if (cb->errors) {
c8b97818	212	bio_io_error(cb->orig_bio);
d20f7043 CM	213	} else {
	214	int bio_index = 0;
	215	struct bio_vec *bvec = cb->orig_bio->bi_io_vec;
	216
	217	/*
	218	* we have verified the checksum already, set page
	219	* checked so the end_io handlers know about it
	220	*/
d397712b	221	while (bio_index < cb->orig_bio->bi_vcnt) {
d20f7043 CM	222	SetPageChecked(bvec->bv_page);
	223	bvec++;
	224	bio_index++;
	225	}
c8b97818	226	bio_endio(cb->orig_bio, 0);
d20f7043	227	}
c8b97818 CM	228
	229	/* finally free the cb struct */
	230	kfree(cb->compressed_pages);
	231	kfree(cb);
	232	out:
	233	bio_put(bio);
	234	}
	235
	236	/*
	237	* Clear the writeback bits on all of the file
	238	* pages for a compressed write
	239	*/
	240	static noinline int end_compressed_writeback(struct inode *inode, u64 start,
	241	unsigned long ram_size)
	242	{
	243	unsigned long index = start >> PAGE_CACHE_SHIFT;
	244	unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
	245	struct page *pages[16];
	246	unsigned long nr_pages = end_index - index + 1;
	247	int i;
	248	int ret;
	249
d397712b	250	while (nr_pages > 0) {
c8b97818	251	ret = find_get_pages_contig(inode->i_mapping, index,
5b050f04 CM	252	min_t(unsigned long,
5b050f04 CM	253	nr_pages, ARRAY_SIZE(pages)), pages);
c8b97818 CM	254	if (ret == 0) {
	255	nr_pages -= 1;
	256	index += 1;
	257	continue;
	258	}
	259	for (i = 0; i < ret; i++) {
	260	end_page_writeback(pages[i]);
	261	page_cache_release(pages[i]);
	262	}
	263	nr_pages -= ret;
	264	index += ret;
	265	}
	266	/* the inode may be gone now */
	267	return 0;
	268	}
	269
	270	/*
	271	* do the cleanup once all the compressed pages hit the disk.
	272	* This will clear writeback on the file pages and free the compressed
	273	* pages.
	274	*
	275	* This also calls the writeback end hooks for the file pages so that
	276	* metadata and checksums can be updated in the file.
	277	*/
	278	static void end_compressed_bio_write(struct bio *bio, int err)
	279	{
	280	struct extent_io_tree *tree;
	281	struct compressed_bio *cb = bio->bi_private;
	282	struct inode *inode;
	283	struct page *page;
	284	unsigned long index;
	285
	286	if (err)
	287	cb->errors = 1;
	288
	289	/* if there are more bios still pending for this compressed
	290	* extent, just exit
	291	*/
	292	if (!atomic_dec_and_test(&cb->pending_bios))
	293	goto out;
	294
	295	/* ok, we're the last bio for this extent, step one is to
	296	* call back into the FS and do all the end_io operations
	297	*/
	298	inode = cb->inode;
	299	tree = &BTRFS_I(inode)->io_tree;
70b99e69	300	cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
c8b97818 CM	301	tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
	302	cb->start,
	303	cb->start + cb->len - 1,
	304	NULL, 1);
70b99e69	305	cb->compressed_pages[0]->mapping = NULL;
c8b97818 CM	306
	307	end_compressed_writeback(inode, cb->start, cb->len);
	308	/* note, our inode could be gone now */
	309
	310	/*
	311	* release the compressed pages, these came from alloc_page and
	312	* are not attached to the inode at all
	313	*/
	314	index = 0;
	315	for (index = 0; index < cb->nr_pages; index++) {
	316	page = cb->compressed_pages[index];
	317	page->mapping = NULL;
	318	page_cache_release(page);
	319	}
	320
	321	/* finally free the cb struct */
	322	kfree(cb->compressed_pages);
	323	kfree(cb);
	324	out:
	325	bio_put(bio);
	326	}
	327
	328	/*
	329	* worker function to build and submit bios for previously compressed pages.
	330	* The corresponding pages in the inode should be marked for writeback
	331	* and the compressed pages should have a reference on them for dropping
	332	* when the IO is complete.
	333	*
	334	* This also checksums the file bytes and gets things ready for
	335	* the end io hooks.
	336	*/
	337	int btrfs_submit_compressed_write(struct inode *inode, u64 start,
	338	unsigned long len, u64 disk_start,
	339	unsigned long compressed_len,
	340	struct page **compressed_pages,
	341	unsigned long nr_pages)
	342	{
	343	struct bio *bio = NULL;
	344	struct btrfs_root *root = BTRFS_I(inode)->root;
	345	struct compressed_bio *cb;
	346	unsigned long bytes_left;
	347	struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
	348	int page_index = 0;
	349	struct page *page;
	350	u64 first_byte = disk_start;
	351	struct block_device *bdev;
	352	int ret;
	353
	354	WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
d20f7043	355	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
c8b97818 CM	356	atomic_set(&cb->pending_bios, 0);
	357	cb->errors = 0;
	358	cb->inode = inode;
	359	cb->start = start;
	360	cb->len = len;
d20f7043	361	cb->mirror_num = 0;
c8b97818 CM	362	cb->compressed_pages = compressed_pages;
	363	cb->compressed_len = compressed_len;
	364	cb->orig_bio = NULL;
	365	cb->nr_pages = nr_pages;
	366
	367	bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
	368
c8b97818 CM	369	bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
	370	bio->bi_private = cb;
	371	bio->bi_end_io = end_compressed_bio_write;
	372	atomic_inc(&cb->pending_bios);
	373
	374	/* create and submit bios for the compressed pages */
	375	bytes_left = compressed_len;
cfbc246e	376	for (page_index = 0; page_index < cb->nr_pages; page_index++) {
c8b97818 CM	377	page = compressed_pages[page_index];
	378	page->mapping = inode->i_mapping;
	379	if (bio->bi_size)
	380	ret = io_tree->ops->merge_bio_hook(page, 0,
	381	PAGE_CACHE_SIZE,
	382	bio, 0);
	383	else
	384	ret = 0;
	385
70b99e69	386	page->mapping = NULL;
c8b97818 CM	387	if (ret \|\| bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
	388	PAGE_CACHE_SIZE) {
	389	bio_get(bio);
	390
af09abfe CM	391	/*
	392	* inc the count before we submit the bio so
	393	* we know the end IO handler won't happen before
	394	* we inc the count. Otherwise, the cb might get
	395	* freed before we're done setting it up
	396	*/
	397	atomic_inc(&cb->pending_bios);
c8b97818 CM	398	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
	399	BUG_ON(ret);
	400
d20f7043 CM	401	ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
	402	BUG_ON(ret);
	403
c8b97818 CM	404	ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
	405	BUG_ON(ret);
	406
	407	bio_put(bio);
	408
	409	bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
c8b97818 CM	410	bio->bi_private = cb;
	411	bio->bi_end_io = end_compressed_bio_write;
	412	bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
	413	}
cfbc246e CM	414	if (bytes_left < PAGE_CACHE_SIZE) {
	415	printk("bytes left %lu compress len %lu nr %lu\n",
	416	bytes_left, cb->compressed_len, cb->nr_pages);
	417	}
c8b97818 CM	418	bytes_left -= PAGE_CACHE_SIZE;
c8b97818 CM	419	first_byte += PAGE_CACHE_SIZE;
771ed689	420	cond_resched();
c8b97818 CM	421	}
	422	bio_get(bio);
	423
	424	ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
	425	BUG_ON(ret);
	426
d20f7043 CM	427	ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
	428	BUG_ON(ret);
	429
c8b97818 CM	430	ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
	431	BUG_ON(ret);
	432
	433	bio_put(bio);
	434	return 0;
	435	}
	436
771ed689 CM	437	static noinline int add_ra_bio_pages(struct inode *inode,
	438	u64 compressed_end,
	439	struct compressed_bio *cb)
	440	{
	441	unsigned long end_index;
	442	unsigned long page_index;
	443	u64 last_offset;
	444	u64 isize = i_size_read(inode);
	445	int ret;
	446	struct page *page;
	447	unsigned long nr_pages = 0;
	448	struct extent_map *em;
	449	struct address_space *mapping = inode->i_mapping;
	450	struct pagevec pvec;
	451	struct extent_map_tree *em_tree;
	452	struct extent_io_tree *tree;
	453	u64 end;
	454	int misses = 0;
	455
	456	page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
	457	last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
	458	em_tree = &BTRFS_I(inode)->extent_tree;
	459	tree = &BTRFS_I(inode)->io_tree;
	460
	461	if (isize == 0)
	462	return 0;
	463
	464	end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
	465
	466	pagevec_init(&pvec, 0);
d397712b	467	while (last_offset < compressed_end) {
771ed689 CM	468	page_index = last_offset >> PAGE_CACHE_SHIFT;
	469
	470	if (page_index > end_index)
	471	break;
	472
	473	rcu_read_lock();
	474	page = radix_tree_lookup(&mapping->page_tree, page_index);
	475	rcu_read_unlock();
	476	if (page) {
	477	misses++;
	478	if (misses > 4)
	479	break;
	480	goto next;
	481	}
	482
	483	page = alloc_page(mapping_gfp_mask(mapping) \| GFP_NOFS);
	484	if (!page)
	485	break;
	486
	487	page->index = page_index;
	488	/*
	489	* what we want to do here is call add_to_page_cache_lru,
	490	* but that isn't exported, so we reproduce it here
	491	*/
	492	if (add_to_page_cache(page, mapping,
	493	page->index, GFP_NOFS)) {
	494	page_cache_release(page);
	495	goto next;
	496	}
	497
	498	/* open coding of lru_cache_add, also not exported */
	499	page_cache_get(page);
	500	if (!pagevec_add(&pvec, page))
15916de8	501	__pagevec_lru_add_file(&pvec);
771ed689 CM	502
	503	end = last_offset + PAGE_CACHE_SIZE - 1;
	504	/*
	505	* at this point, we have a locked page in the page cache
	506	* for these bytes in the file. But, we have to make
	507	* sure they map to this compressed extent on disk.
	508	*/
	509	set_page_extent_mapped(page);
	510	lock_extent(tree, last_offset, end, GFP_NOFS);
	511	spin_lock(&em_tree->lock);
	512	em = lookup_extent_mapping(em_tree, last_offset,
	513	PAGE_CACHE_SIZE);
	514	spin_unlock(&em_tree->lock);
	515
	516	if (!em \|\| last_offset < em->start \|\|
	517	(last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) \|\|
	518	(em->block_start >> 9) != cb->orig_bio->bi_sector) {
	519	free_extent_map(em);
	520	unlock_extent(tree, last_offset, end, GFP_NOFS);
	521	unlock_page(page);
	522	page_cache_release(page);
	523	break;
	524	}
	525	free_extent_map(em);
	526
	527	if (page->index == end_index) {
	528	char *userpage;
	529	size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
	530
	531	if (zero_offset) {
	532	int zeros;
	533	zeros = PAGE_CACHE_SIZE - zero_offset;
	534	userpage = kmap_atomic(page, KM_USER0);
	535	memset(userpage + zero_offset, 0, zeros);
	536	flush_dcache_page(page);
	537	kunmap_atomic(userpage, KM_USER0);
	538	}
	539	}
	540
	541	ret = bio_add_page(cb->orig_bio, page,
	542	PAGE_CACHE_SIZE, 0);
	543
	544	if (ret == PAGE_CACHE_SIZE) {
	545	nr_pages++;
	546	page_cache_release(page);
	547	} else {
	548	unlock_extent(tree, last_offset, end, GFP_NOFS);
	549	unlock_page(page);
	550	page_cache_release(page);
	551	break;
	552	}
	553	next:
	554	last_offset += PAGE_CACHE_SIZE;
	555	}
	556	if (pagevec_count(&pvec))
15916de8	557	__pagevec_lru_add_file(&pvec);
771ed689 CM	558	return 0;
	559	}
	560
c8b97818 CM	561	/*
	562	* for a compressed read, the bio we get passed has all the inode pages
	563	* in it. We don't actually do IO on those pages but allocate new ones
	564	* to hold the compressed pages on disk.
	565	*
	566	* bio->bi_sector points to the compressed extent on disk
	567	* bio->bi_io_vec points to all of the inode pages
	568	* bio->bi_vcnt is a count of pages
	569	*
	570	* After the compressed pages are read, we copy the bytes into the
	571	* bio we were passed and then call the bio end_io calls
	572	*/
	573	int btrfs_submit_compressed_read(struct inode inode, struct bio bio,
	574	int mirror_num, unsigned long bio_flags)
	575	{
	576	struct extent_io_tree *tree;
	577	struct extent_map_tree *em_tree;
	578	struct compressed_bio *cb;
	579	struct btrfs_root *root = BTRFS_I(inode)->root;
	580	unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
	581	unsigned long compressed_len;
	582	unsigned long nr_pages;
	583	unsigned long page_index;
	584	struct page *page;
	585	struct block_device *bdev;
	586	struct bio *comp_bio;
	587	u64 cur_disk_byte = (u64)bio->bi_sector << 9;
e04ca626 CM	588	u64 em_len;
e04ca626 CM	589	u64 em_start;
c8b97818 CM	590	struct extent_map *em;
c8b97818 CM	591	int ret;
d20f7043	592	u32 *sums;
c8b97818 CM	593
	594	tree = &BTRFS_I(inode)->io_tree;
	595	em_tree = &BTRFS_I(inode)->extent_tree;
	596
	597	/* we need the actual starting offset of this extent in the file */
	598	spin_lock(&em_tree->lock);
	599	em = lookup_extent_mapping(em_tree,
	600	page_offset(bio->bi_io_vec->bv_page),
	601	PAGE_CACHE_SIZE);
	602	spin_unlock(&em_tree->lock);
	603
d20f7043 CM	604	compressed_len = em->block_len;
d20f7043 CM	605	cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
c8b97818 CM	606	atomic_set(&cb->pending_bios, 0);
	607	cb->errors = 0;
	608	cb->inode = inode;
d20f7043 CM	609	cb->mirror_num = mirror_num;
d20f7043 CM	610	sums = &cb->sums;
c8b97818	611
ff5b7ee3	612	cb->start = em->orig_start;
e04ca626 CM	613	em_len = em->len;
e04ca626 CM	614	em_start = em->start;
d20f7043	615
c8b97818	616	free_extent_map(em);
e04ca626	617	em = NULL;
c8b97818 CM	618
	619	cb->len = uncompressed_len;
	620	cb->compressed_len = compressed_len;
	621	cb->orig_bio = bio;
	622
	623	nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
	624	PAGE_CACHE_SIZE;
	625	cb->compressed_pages = kmalloc(sizeof(struct page ) nr_pages,
	626	GFP_NOFS);
	627	bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
	628
	629	for (page_index = 0; page_index < nr_pages; page_index++) {
	630	cb->compressed_pages[page_index] = alloc_page(GFP_NOFS \|
	631	__GFP_HIGHMEM);
	632	}
	633	cb->nr_pages = nr_pages;
	634
e04ca626	635	add_ra_bio_pages(inode, em_start + em_len, cb);
771ed689	636
771ed689 CM	637	/* include any pages we added in add_ra-bio_pages */
	638	uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
	639	cb->len = uncompressed_len;
	640
c8b97818 CM	641	comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
	642	comp_bio->bi_private = cb;
	643	comp_bio->bi_end_io = end_compressed_bio_read;
	644	atomic_inc(&cb->pending_bios);
	645
	646	for (page_index = 0; page_index < nr_pages; page_index++) {
	647	page = cb->compressed_pages[page_index];
	648	page->mapping = inode->i_mapping;
d20f7043 CM	649	page->index = em_start >> PAGE_CACHE_SHIFT;
d20f7043 CM	650
c8b97818 CM	651	if (comp_bio->bi_size)
	652	ret = tree->ops->merge_bio_hook(page, 0,
	653	PAGE_CACHE_SIZE,
	654	comp_bio, 0);
	655	else
	656	ret = 0;
	657
70b99e69	658	page->mapping = NULL;
c8b97818 CM	659	if (ret \|\| bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
	660	PAGE_CACHE_SIZE) {
	661	bio_get(comp_bio);
	662
	663	ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
	664	BUG_ON(ret);
	665
af09abfe CM	666	/*
	667	* inc the count before we submit the bio so
	668	* we know the end IO handler won't happen before
	669	* we inc the count. Otherwise, the cb might get
	670	* freed before we're done setting it up
	671	*/
	672	atomic_inc(&cb->pending_bios);
	673
17d217fe	674	if (!btrfs_test_flag(inode, NODATASUM)) {
d20f7043 CM	675	btrfs_lookup_bio_sums(root, inode, comp_bio,
	676	sums);
	677	}
	678	sums += (comp_bio->bi_size + root->sectorsize - 1) /
	679	root->sectorsize;
	680
	681	ret = btrfs_map_bio(root, READ, comp_bio,
	682	mirror_num, 0);
c8b97818 CM	683	BUG_ON(ret);
	684
	685	bio_put(comp_bio);
	686
	687	comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
	688	GFP_NOFS);
771ed689 CM	689	comp_bio->bi_private = cb;
	690	comp_bio->bi_end_io = end_compressed_bio_read;
	691
	692	bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
c8b97818 CM	693	}
	694	cur_disk_byte += PAGE_CACHE_SIZE;
	695	}
	696	bio_get(comp_bio);
	697
	698	ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
	699	BUG_ON(ret);
	700
d397712b	701	if (!btrfs_test_flag(inode, NODATASUM))
d20f7043	702	btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
d20f7043 CM	703
d20f7043 CM	704	ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
c8b97818 CM	705	BUG_ON(ret);
	706
	707	bio_put(comp_bio);
	708	return 0;
	709	}