Moved, renamed, and deleted files

The original directory structure was scattered and unorganized.
Changes are basically to make it look like kernel structure.

1 files changed, 0 insertions, 2440 deletions

diff --git a/ANDROID_3.4.5/fs/btrfs/scrub.c b/ANDROID_3.4.5/fs/btrfs/scrub.c
deleted file mode 100644
index 2f3d6f91..00000000
--- a/ANDROID_3.4.5/fs/btrfs/scrub.c
+++ /dev/null
@@ -1,2440 +0,0 @@
-/*
- * Copyright (C) 2011 STRATO.  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/blkdev.h>
-#include <linux/ratelimit.h>
-#include "ctree.h"
-#include "volumes.h"
-#include "disk-io.h"
-#include "ordered-data.h"
-#include "transaction.h"
-#include "backref.h"
-#include "extent_io.h"
-#include "check-integrity.h"
-
-/*
- * This is only the first step towards a full-features scrub. It reads all
- * extent and super block and verifies the checksums. In case a bad checksum
- * is found or the extent cannot be read, good data will be written back if
- * any can be found.
- *
- * Future enhancements:
- *  - In case an unrepairable extent is encountered, track which files are
- *    affected and report them
- *  - track and record media errors, throw out bad devices
- *  - add a mode to also read unallocated space
- */
-
-struct scrub_block;
-struct scrub_dev;
-
-#define SCRUB_PAGES_PER_BIO	16	/* 64k per bio */
-#define SCRUB_BIOS_PER_DEV	16	/* 1 MB per device in flight */
-#define SCRUB_MAX_PAGES_PER_BLOCK	16	/* 64k per node/leaf/sector */
-
-struct scrub_page {
-	struct scrub_block	*sblock;
-	struct page		*page;
-	struct block_device	*bdev;
-	u64			flags;  /* extent flags */
-	u64			generation;
-	u64			logical;
-	u64			physical;
-	struct {
-		unsigned int	mirror_num:8;
-		unsigned int	have_csum:1;
-		unsigned int	io_error:1;
-	};
-	u8			csum[BTRFS_CSUM_SIZE];
-};
-
-struct scrub_bio {
-	int			index;
-	struct scrub_dev	*sdev;
-	struct bio		*bio;
-	int			err;
-	u64			logical;
-	u64			physical;
-	struct scrub_page	*pagev[SCRUB_PAGES_PER_BIO];
-	int			page_count;
-	int			next_free;
-	struct btrfs_work	work;
-};
-
-struct scrub_block {
-	struct scrub_page	pagev[SCRUB_MAX_PAGES_PER_BLOCK];
-	int			page_count;
-	atomic_t		outstanding_pages;
-	atomic_t		ref_count; /* free mem on transition to zero */
-	struct scrub_dev	*sdev;
-	struct {
-		unsigned int	header_error:1;
-		unsigned int	checksum_error:1;
-		unsigned int	no_io_error_seen:1;
-	};
-};
-
-struct scrub_dev {
-	struct scrub_bio	*bios[SCRUB_BIOS_PER_DEV];
-	struct btrfs_device	*dev;
-	int			first_free;
-	int			curr;
-	atomic_t		in_flight;
-	atomic_t		fixup_cnt;
-	spinlock_t		list_lock;
-	wait_queue_head_t	list_wait;
-	u16			csum_size;
-	struct list_head	csum_list;
-	atomic_t		cancel_req;
-	int			readonly;
-	int			pages_per_bio; /* <= SCRUB_PAGES_PER_BIO */
-	u32			sectorsize;
-	u32			nodesize;
-	u32			leafsize;
-	/*
-	 * statistics
-	 */
-	struct btrfs_scrub_progress stat;
-	spinlock_t		stat_lock;
-};
-
-struct scrub_fixup_nodatasum {
-	struct scrub_dev	*sdev;
-	u64			logical;
-	struct btrfs_root	*root;
-	struct btrfs_work	work;
-	int			mirror_num;
-};
-
-struct scrub_warning {
-	struct btrfs_path	*path;
-	u64			extent_item_size;
-	char			*scratch_buf;
-	char			*msg_buf;
-	const char		*errstr;
-	sector_t		sector;
-	u64			logical;
-	struct btrfs_device	*dev;
-	int			msg_bufsize;
-	int			scratch_bufsize;
-};
-
-
-static int scrub_handle_errored_block(struct scrub_block *sblock_to_check);
-static int scrub_setup_recheck_block(struct scrub_dev *sdev,
-				     struct btrfs_mapping_tree *map_tree,
-				     u64 length, u64 logical,
-				     struct scrub_block *sblock);
-static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
-			       struct scrub_block *sblock, int is_metadata,
-			       int have_csum, u8 *csum, u64 generation,
-			       u16 csum_size);
-static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
-					 struct scrub_block *sblock,
-					 int is_metadata, int have_csum,
-					 const u8 *csum, u64 generation,
-					 u16 csum_size);
-static void scrub_complete_bio_end_io(struct bio *bio, int err);
-static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
-					     struct scrub_block *sblock_good,
-					     int force_write);
-static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
-					    struct scrub_block *sblock_good,
-					    int page_num, int force_write);
-static int scrub_checksum_data(struct scrub_block *sblock);
-static int scrub_checksum_tree_block(struct scrub_block *sblock);
-static int scrub_checksum_super(struct scrub_block *sblock);
-static void scrub_block_get(struct scrub_block *sblock);
-static void scrub_block_put(struct scrub_block *sblock);
-static int scrub_add_page_to_bio(struct scrub_dev *sdev,
-				 struct scrub_page *spage);
-static int scrub_pages(struct scrub_dev *sdev, u64 logical, u64 len,
-		       u64 physical, u64 flags, u64 gen, int mirror_num,
-		       u8 *csum, int force);
-static void scrub_bio_end_io(struct bio *bio, int err);
-static void scrub_bio_end_io_worker(struct btrfs_work *work);
-static void scrub_block_complete(struct scrub_block *sblock);
-
-
-static void scrub_free_csums(struct scrub_dev *sdev)
-{
-	while (!list_empty(&sdev->csum_list)) {
-		struct btrfs_ordered_sum *sum;
-		sum = list_first_entry(&sdev->csum_list,
-				       struct btrfs_ordered_sum, list);
-		list_del(&sum->list);
-		kfree(sum);
-	}
-}
-
-static noinline_for_stack void scrub_free_dev(struct scrub_dev *sdev)
-{
-	int i;
-
-	if (!sdev)
-		return;
-
-	/* this can happen when scrub is cancelled */
-	if (sdev->curr != -1) {
-		struct scrub_bio *sbio = sdev->bios[sdev->curr];
-
-		for (i = 0; i < sbio->page_count; i++) {
-			BUG_ON(!sbio->pagev[i]);
-			BUG_ON(!sbio->pagev[i]->page);
-			scrub_block_put(sbio->pagev[i]->sblock);
-		}
-		bio_put(sbio->bio);
-	}
-
-	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
-		struct scrub_bio *sbio = sdev->bios[i];
-
-		if (!sbio)
-			break;
-		kfree(sbio);
-	}
-
-	scrub_free_csums(sdev);
-	kfree(sdev);
-}
-
-static noinline_for_stack
-struct scrub_dev *scrub_setup_dev(struct btrfs_device *dev)
-{
-	struct scrub_dev *sdev;
-	int		i;
-	struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
-	int pages_per_bio;
-
-	pages_per_bio = min_t(int, SCRUB_PAGES_PER_BIO,
-			      bio_get_nr_vecs(dev->bdev));
-	sdev = kzalloc(sizeof(*sdev), GFP_NOFS);
-	if (!sdev)
-		goto nomem;
-	sdev->dev = dev;
-	sdev->pages_per_bio = pages_per_bio;
-	sdev->curr = -1;
-	for (i = 0; i < SCRUB_BIOS_PER_DEV; ++i) {
-		struct scrub_bio *sbio;
-
-		sbio = kzalloc(sizeof(*sbio), GFP_NOFS);
-		if (!sbio)
-			goto nomem;
-		sdev->bios[i] = sbio;
-
-		sbio->index = i;
-		sbio->sdev = sdev;
-		sbio->page_count = 0;
-		sbio->work.func = scrub_bio_end_io_worker;
-
-		if (i != SCRUB_BIOS_PER_DEV-1)
-			sdev->bios[i]->next_free = i + 1;
-		else
-			sdev->bios[i]->next_free = -1;
-	}
-	sdev->first_free = 0;
-	sdev->nodesize = dev->dev_root->nodesize;
-	sdev->leafsize = dev->dev_root->leafsize;
-	sdev->sectorsize = dev->dev_root->sectorsize;
-	atomic_set(&sdev->in_flight, 0);
-	atomic_set(&sdev->fixup_cnt, 0);
-	atomic_set(&sdev->cancel_req, 0);
-	sdev->csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	INIT_LIST_HEAD(&sdev->csum_list);
-
-	spin_lock_init(&sdev->list_lock);
-	spin_lock_init(&sdev->stat_lock);
-	init_waitqueue_head(&sdev->list_wait);
-	return sdev;
-
-nomem:
-	scrub_free_dev(sdev);
-	return ERR_PTR(-ENOMEM);
-}
-
-static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root, void *ctx)
-{
-	u64 isize;
-	u32 nlink;
-	int ret;
-	int i;
-	struct extent_buffer *eb;
-	struct btrfs_inode_item *inode_item;
-	struct scrub_warning *swarn = ctx;
-	struct btrfs_fs_info *fs_info = swarn->dev->dev_root->fs_info;
-	struct inode_fs_paths *ipath = NULL;
-	struct btrfs_root *local_root;
-	struct btrfs_key root_key;
-
-	root_key.objectid = root;
-	root_key.type = BTRFS_ROOT_ITEM_KEY;
-	root_key.offset = (u64)-1;
-	local_root = btrfs_read_fs_root_no_name(fs_info, &root_key);
-	if (IS_ERR(local_root)) {
-		ret = PTR_ERR(local_root);
-		goto err;
-	}
-
-	ret = inode_item_info(inum, 0, local_root, swarn->path);
-	if (ret) {
-		btrfs_release_path(swarn->path);
-		goto err;
-	}
-
-	eb = swarn->path->nodes[0];
-	inode_item = btrfs_item_ptr(eb, swarn->path->slots[0],
-					struct btrfs_inode_item);
-	isize = btrfs_inode_size(eb, inode_item);
-	nlink = btrfs_inode_nlink(eb, inode_item);
-	btrfs_release_path(swarn->path);
-
-	ipath = init_ipath(4096, local_root, swarn->path);
-	if (IS_ERR(ipath)) {
-		ret = PTR_ERR(ipath);
-		ipath = NULL;
-		goto err;
-	}
-	ret = paths_from_inode(inum, ipath);
-
-	if (ret < 0)
-		goto err;
-
-	/*
-	 * we deliberately ignore the bit ipath might have been too small to
-	 * hold all of the paths here
-	 */
-	for (i = 0; i < ipath->fspath->elem_cnt; ++i)
-		printk(KERN_WARNING "btrfs: %s at logical %llu on dev "
-			"%s, sector %llu, root %llu, inode %llu, offset %llu, "
-			"length %llu, links %u (path: %s)\n", swarn->errstr,
-			swarn->logical, swarn->dev->name,
-			(unsigned long long)swarn->sector, root, inum, offset,
-			min(isize - offset, (u64)PAGE_SIZE), nlink,
-			(char *)(unsigned long)ipath->fspath->val[i]);
-
-	free_ipath(ipath);
-	return 0;
-
-err:
-	printk(KERN_WARNING "btrfs: %s at logical %llu on dev "
-		"%s, sector %llu, root %llu, inode %llu, offset %llu: path "
-		"resolving failed with ret=%d\n", swarn->errstr,
-		swarn->logical, swarn->dev->name,
-		(unsigned long long)swarn->sector, root, inum, offset, ret);
-
-	free_ipath(ipath);
-	return 0;
-}
-
-static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
-{
-	struct btrfs_device *dev = sblock->sdev->dev;
-	struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
-	struct btrfs_path *path;
-	struct btrfs_key found_key;
-	struct extent_buffer *eb;
-	struct btrfs_extent_item *ei;
-	struct scrub_warning swarn;
-	u32 item_size;
-	int ret;
-	u64 ref_root;
-	u8 ref_level;
-	unsigned long ptr = 0;
-	const int bufsize = 4096;
-	u64 extent_item_pos;
-
-	path = btrfs_alloc_path();
-
-	swarn.scratch_buf = kmalloc(bufsize, GFP_NOFS);
-	swarn.msg_buf = kmalloc(bufsize, GFP_NOFS);
-	BUG_ON(sblock->page_count < 1);
-	swarn.sector = (sblock->pagev[0].physical) >> 9;
-	swarn.logical = sblock->pagev[0].logical;
-	swarn.errstr = errstr;
-	swarn.dev = dev;
-	swarn.msg_bufsize = bufsize;
-	swarn.scratch_bufsize = bufsize;
-
-	if (!path || !swarn.scratch_buf || !swarn.msg_buf)
-		goto out;
-
-	ret = extent_from_logical(fs_info, swarn.logical, path, &found_key);
-	if (ret < 0)
-		goto out;
-
-	extent_item_pos = swarn.logical - found_key.objectid;
-	swarn.extent_item_size = found_key.offset;
-
-	eb = path->nodes[0];
-	ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
-	item_size = btrfs_item_size_nr(eb, path->slots[0]);
-	btrfs_release_path(path);
-
-	if (ret & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
-		do {
-			ret = tree_backref_for_extent(&ptr, eb, ei, item_size,
-							&ref_root, &ref_level);
-			printk(KERN_WARNING
-				"btrfs: %s at logical %llu on dev %s, "
-				"sector %llu: metadata %s (level %d) in tree "
-				"%llu\n", errstr, swarn.logical, dev->name,
-				(unsigned long long)swarn.sector,
-				ref_level ? "node" : "leaf",
-				ret < 0 ? -1 : ref_level,
-				ret < 0 ? -1 : ref_root);
-		} while (ret != 1);
-	} else {
-		swarn.path = path;
-		iterate_extent_inodes(fs_info, found_key.objectid,
-					extent_item_pos, 1,
-					scrub_print_warning_inode, &swarn);
-	}
-
-out:
-	btrfs_free_path(path);
-	kfree(swarn.scratch_buf);
-	kfree(swarn.msg_buf);
-}
-
-static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *ctx)
-{
-	struct page *page = NULL;
-	unsigned long index;
-	struct scrub_fixup_nodatasum *fixup = ctx;
-	int ret;
-	int corrected = 0;
-	struct btrfs_key key;
-	struct inode *inode = NULL;
-	u64 end = offset + PAGE_SIZE - 1;
-	struct btrfs_root *local_root;
-
-	key.objectid = root;
-	key.type = BTRFS_ROOT_ITEM_KEY;
-	key.offset = (u64)-1;
-	local_root = btrfs_read_fs_root_no_name(fixup->root->fs_info, &key);
-	if (IS_ERR(local_root))
-		return PTR_ERR(local_root);
-
-	key.type = BTRFS_INODE_ITEM_KEY;
-	key.objectid = inum;
-	key.offset = 0;
-	inode = btrfs_iget(fixup->root->fs_info->sb, &key, local_root, NULL);
-	if (IS_ERR(inode))
-		return PTR_ERR(inode);
-
-	index = offset >> PAGE_CACHE_SHIFT;
-
-	page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
-	if (!page) {
-		ret = -ENOMEM;
-		goto out;
-	}
-
-	if (PageUptodate(page)) {
-		struct btrfs_mapping_tree *map_tree;
-		if (PageDirty(page)) {
-			/*
-			 * we need to write the data to the defect sector. the
-			 * data that was in that sector is not in memory,
-			 * because the page was modified. we must not write the
-			 * modified page to that sector.
-			 *
-			 * TODO: what could be done here: wait for the delalloc
-			 *       runner to write out that page (might involve
-			 *       COW) and see whether the sector is still
-			 *       referenced afterwards.
-			 *
-			 * For the meantime, we'll treat this error
-			 * incorrectable, although there is a chance that a
-			 * later scrub will find the bad sector again and that
-			 * there's no dirty page in memory, then.
-			 */
-			ret = -EIO;
-			goto out;
-		}
-		map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
-		ret = repair_io_failure(map_tree, offset, PAGE_SIZE,
-					fixup->logical, page,
-					fixup->mirror_num);
-		unlock_page(page);
-		corrected = !ret;
-	} else {
-		/*
-		 * we need to get good data first. the general readpage path
-		 * will call repair_io_failure for us, we just have to make
-		 * sure we read the bad mirror.
-		 */
-		ret = set_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
-					EXTENT_DAMAGED, GFP_NOFS);
-		if (ret) {
-			/* set_extent_bits should give proper error */
-			WARN_ON(ret > 0);
-			if (ret > 0)
-				ret = -EFAULT;
-			goto out;
-		}
-
-		ret = extent_read_full_page(&BTRFS_I(inode)->io_tree, page,
-						btrfs_get_extent,
-						fixup->mirror_num);
-		wait_on_page_locked(page);
-
-		corrected = !test_range_bit(&BTRFS_I(inode)->io_tree, offset,
-						end, EXTENT_DAMAGED, 0, NULL);
-		if (!corrected)
-			clear_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
-						EXTENT_DAMAGED, GFP_NOFS);
-	}
-
-out:
-	if (page)
-		put_page(page);
-	if (inode)
-		iput(inode);
-
-	if (ret < 0)
-		return ret;
-
-	if (ret == 0 && corrected) {
-		/*
-		 * we only need to call readpage for one of the inodes belonging
-		 * to this extent. so make iterate_extent_inodes stop
-		 */
-		return 1;
-	}
-
-	return -EIO;
-}
-
-static void scrub_fixup_nodatasum(struct btrfs_work *work)
-{
-	int ret;
-	struct scrub_fixup_nodatasum *fixup;
-	struct scrub_dev *sdev;
-	struct btrfs_trans_handle *trans = NULL;
-	struct btrfs_fs_info *fs_info;
-	struct btrfs_path *path;
-	int uncorrectable = 0;
-
-	fixup = container_of(work, struct scrub_fixup_nodatasum, work);
-	sdev = fixup->sdev;
-	fs_info = fixup->root->fs_info;
-
-	path = btrfs_alloc_path();
-	if (!path) {
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.malloc_errors;
-		spin_unlock(&sdev->stat_lock);
-		uncorrectable = 1;
-		goto out;
-	}
-
-	trans = btrfs_join_transaction(fixup->root);
-	if (IS_ERR(trans)) {
-		uncorrectable = 1;
-		goto out;
-	}
-
-	/*
-	 * the idea is to trigger a regular read through the standard path. we
-	 * read a page from the (failed) logical address by specifying the
-	 * corresponding copynum of the failed sector. thus, that readpage is
-	 * expected to fail.
-	 * that is the point where on-the-fly error correction will kick in
-	 * (once it's finished) and rewrite the failed sector if a good copy
-	 * can be found.
-	 */
-	ret = iterate_inodes_from_logical(fixup->logical, fixup->root->fs_info,
-						path, scrub_fixup_readpage,
-						fixup);
-	if (ret < 0) {
-		uncorrectable = 1;
-		goto out;
-	}
-	WARN_ON(ret != 1);
-
-	spin_lock(&sdev->stat_lock);
-	++sdev->stat.corrected_errors;
-	spin_unlock(&sdev->stat_lock);
-
-out:
-	if (trans && !IS_ERR(trans))
-		btrfs_end_transaction(trans, fixup->root);
-	if (uncorrectable) {
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.uncorrectable_errors;
-		spin_unlock(&sdev->stat_lock);
-		printk_ratelimited(KERN_ERR
-			"btrfs: unable to fixup (nodatasum) error at logical %llu on dev %s\n",
-			(unsigned long long)fixup->logical, sdev->dev->name);
-	}
-
-	btrfs_free_path(path);
-	kfree(fixup);
-
-	/* see caller why we're pretending to be paused in the scrub counters */
-	mutex_lock(&fs_info->scrub_lock);
-	atomic_dec(&fs_info->scrubs_running);
-	atomic_dec(&fs_info->scrubs_paused);
-	mutex_unlock(&fs_info->scrub_lock);
-	atomic_dec(&sdev->fixup_cnt);
-	wake_up(&fs_info->scrub_pause_wait);
-	wake_up(&sdev->list_wait);
-}
-
-/*
- * scrub_handle_errored_block gets called when either verification of the
- * pages failed or the bio failed to read, e.g. with EIO. In the latter
- * case, this function handles all pages in the bio, even though only one
- * may be bad.
- * The goal of this function is to repair the errored block by using the
- * contents of one of the mirrors.
- */
-static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
-{
-	struct scrub_dev *sdev = sblock_to_check->sdev;
-	struct btrfs_fs_info *fs_info;
-	u64 length;
-	u64 logical;
-	u64 generation;
-	unsigned int failed_mirror_index;
-	unsigned int is_metadata;
-	unsigned int have_csum;
-	u8 *csum;
-	struct scrub_block *sblocks_for_recheck; /* holds one for each mirror */
-	struct scrub_block *sblock_bad;
-	int ret;
-	int mirror_index;
-	int page_num;
-	int success;
-	static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
-				      DEFAULT_RATELIMIT_BURST);
-
-	BUG_ON(sblock_to_check->page_count < 1);
-	fs_info = sdev->dev->dev_root->fs_info;
-	length = sblock_to_check->page_count * PAGE_SIZE;
-	logical = sblock_to_check->pagev[0].logical;
-	generation = sblock_to_check->pagev[0].generation;
-	BUG_ON(sblock_to_check->pagev[0].mirror_num < 1);
-	failed_mirror_index = sblock_to_check->pagev[0].mirror_num - 1;
-	is_metadata = !(sblock_to_check->pagev[0].flags &
-			BTRFS_EXTENT_FLAG_DATA);
-	have_csum = sblock_to_check->pagev[0].have_csum;
-	csum = sblock_to_check->pagev[0].csum;
-
-	/*
-	 * read all mirrors one after the other. This includes to
-	 * re-read the extent or metadata block that failed (that was
-	 * the cause that this fixup code is called) another time,
-	 * page by page this time in order to know which pages
-	 * caused I/O errors and which ones are good (for all mirrors).
-	 * It is the goal to handle the situation when more than one
-	 * mirror contains I/O errors, but the errors do not
-	 * overlap, i.e. the data can be repaired by selecting the
-	 * pages from those mirrors without I/O error on the
-	 * particular pages. One example (with blocks >= 2 * PAGE_SIZE)
-	 * would be that mirror #1 has an I/O error on the first page,
-	 * the second page is good, and mirror #2 has an I/O error on
-	 * the second page, but the first page is good.
-	 * Then the first page of the first mirror can be repaired by
-	 * taking the first page of the second mirror, and the
-	 * second page of the second mirror can be repaired by
-	 * copying the contents of the 2nd page of the 1st mirror.
-	 * One more note: if the pages of one mirror contain I/O
-	 * errors, the checksum cannot be verified. In order to get
-	 * the best data for repairing, the first attempt is to find
-	 * a mirror without I/O errors and with a validated checksum.
-	 * Only if this is not possible, the pages are picked from
-	 * mirrors with I/O errors without considering the checksum.
-	 * If the latter is the case, at the end, the checksum of the
-	 * repaired area is verified in order to correctly maintain
-	 * the statistics.
-	 */
-
-	sblocks_for_recheck = kzalloc(BTRFS_MAX_MIRRORS *
-				     sizeof(*sblocks_for_recheck),
-				     GFP_NOFS);
-	if (!sblocks_for_recheck) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.malloc_errors++;
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		goto out;
-	}
-
-	/* setup the context, map the logical blocks and alloc the pages */
-	ret = scrub_setup_recheck_block(sdev, &fs_info->mapping_tree, length,
-					logical, sblocks_for_recheck);
-	if (ret) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		goto out;
-	}
-	BUG_ON(failed_mirror_index >= BTRFS_MAX_MIRRORS);
-	sblock_bad = sblocks_for_recheck + failed_mirror_index;
-
-	/* build and submit the bios for the failed mirror, check checksums */
-	ret = scrub_recheck_block(fs_info, sblock_bad, is_metadata, have_csum,
-				  csum, generation, sdev->csum_size);
-	if (ret) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		goto out;
-	}
-
-	if (!sblock_bad->header_error && !sblock_bad->checksum_error &&
-	    sblock_bad->no_io_error_seen) {
-		/*
-		 * the error disappeared after reading page by page, or
-		 * the area was part of a huge bio and other parts of the
-		 * bio caused I/O errors, or the block layer merged several
-		 * read requests into one and the error is caused by a
-		 * different bio (usually one of the two latter cases is
-		 * the cause)
-		 */
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.unverified_errors++;
-		spin_unlock(&sdev->stat_lock);
-
-		goto out;
-	}
-
-	if (!sblock_bad->no_io_error_seen) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.read_errors++;
-		spin_unlock(&sdev->stat_lock);
-		if (__ratelimit(&_rs))
-			scrub_print_warning("i/o error", sblock_to_check);
-	} else if (sblock_bad->checksum_error) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.csum_errors++;
-		spin_unlock(&sdev->stat_lock);
-		if (__ratelimit(&_rs))
-			scrub_print_warning("checksum error", sblock_to_check);
-	} else if (sblock_bad->header_error) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.verify_errors++;
-		spin_unlock(&sdev->stat_lock);
-		if (__ratelimit(&_rs))
-			scrub_print_warning("checksum/header error",
-					    sblock_to_check);
-	}
-
-	if (sdev->readonly)
-		goto did_not_correct_error;
-
-	if (!is_metadata && !have_csum) {
-		struct scrub_fixup_nodatasum *fixup_nodatasum;
-
-		/*
-		 * !is_metadata and !have_csum, this means that the data
-		 * might not be COW'ed, that it might be modified
-		 * concurrently. The general strategy to work on the
-		 * commit root does not help in the case when COW is not
-		 * used.
-		 */
-		fixup_nodatasum = kzalloc(sizeof(*fixup_nodatasum), GFP_NOFS);
-		if (!fixup_nodatasum)
-			goto did_not_correct_error;
-		fixup_nodatasum->sdev = sdev;
-		fixup_nodatasum->logical = logical;
-		fixup_nodatasum->root = fs_info->extent_root;
-		fixup_nodatasum->mirror_num = failed_mirror_index + 1;
-		/*
-		 * increment scrubs_running to prevent cancel requests from
-		 * completing as long as a fixup worker is running. we must also
-		 * increment scrubs_paused to prevent deadlocking on pause
-		 * requests used for transactions commits (as the worker uses a
-		 * transaction context). it is safe to regard the fixup worker
-		 * as paused for all matters practical. effectively, we only
-		 * avoid cancellation requests from completing.
-		 */
-		mutex_lock(&fs_info->scrub_lock);
-		atomic_inc(&fs_info->scrubs_running);
-		atomic_inc(&fs_info->scrubs_paused);
-		mutex_unlock(&fs_info->scrub_lock);
-		atomic_inc(&sdev->fixup_cnt);
-		fixup_nodatasum->work.func = scrub_fixup_nodatasum;
-		btrfs_queue_worker(&fs_info->scrub_workers,
-				   &fixup_nodatasum->work);
-		goto out;
-	}
-
-	/*
-	 * now build and submit the bios for the other mirrors, check
-	 * checksums
-	 */
-	for (mirror_index = 0;
-	     mirror_index < BTRFS_MAX_MIRRORS &&
-	     sblocks_for_recheck[mirror_index].page_count > 0;
-	     mirror_index++) {
-		if (mirror_index == failed_mirror_index)
-			continue;
-
-		/* build and submit the bios, check checksums */
-		ret = scrub_recheck_block(fs_info,
-					  sblocks_for_recheck + mirror_index,
-					  is_metadata, have_csum, csum,
-					  generation, sdev->csum_size);
-		if (ret)
-			goto did_not_correct_error;
-	}
-
-	/*
-	 * first try to pick the mirror which is completely without I/O
-	 * errors and also does not have a checksum error.
-	 * If one is found, and if a checksum is present, the full block
-	 * that is known to contain an error is rewritten. Afterwards
-	 * the block is known to be corrected.
-	 * If a mirror is found which is completely correct, and no
-	 * checksum is present, only those pages are rewritten that had
-	 * an I/O error in the block to be repaired, since it cannot be
-	 * determined, which copy of the other pages is better (and it
-	 * could happen otherwise that a correct page would be
-	 * overwritten by a bad one).
-	 */
-	for (mirror_index = 0;
-	     mirror_index < BTRFS_MAX_MIRRORS &&
-	     sblocks_for_recheck[mirror_index].page_count > 0;
-	     mirror_index++) {
-		struct scrub_block *sblock_other = sblocks_for_recheck +
-						   mirror_index;
-
-		if (!sblock_other->header_error &&
-		    !sblock_other->checksum_error &&
-		    sblock_other->no_io_error_seen) {
-			int force_write = is_metadata || have_csum;
-
-			ret = scrub_repair_block_from_good_copy(sblock_bad,
-								sblock_other,
-								force_write);
-			if (0 == ret)
-				goto corrected_error;
-		}
-	}
-
-	/*
-	 * in case of I/O errors in the area that is supposed to be
-	 * repaired, continue by picking good copies of those pages.
-	 * Select the good pages from mirrors to rewrite bad pages from
-	 * the area to fix. Afterwards verify the checksum of the block
-	 * that is supposed to be repaired. This verification step is
-	 * only done for the purpose of statistic counting and for the
-	 * final scrub report, whether errors remain.
-	 * A perfect algorithm could make use of the checksum and try
-	 * all possible combinations of pages from the different mirrors
-	 * until the checksum verification succeeds. For example, when
-	 * the 2nd page of mirror #1 faces I/O errors, and the 2nd page
-	 * of mirror #2 is readable but the final checksum test fails,
-	 * then the 2nd page of mirror #3 could be tried, whether now
-	 * the final checksum succeedes. But this would be a rare
-	 * exception and is therefore not implemented. At least it is
-	 * avoided that the good copy is overwritten.
-	 * A more useful improvement would be to pick the sectors
-	 * without I/O error based on sector sizes (512 bytes on legacy
-	 * disks) instead of on PAGE_SIZE. Then maybe 512 byte of one
-	 * mirror could be repaired by taking 512 byte of a different
-	 * mirror, even if other 512 byte sectors in the same PAGE_SIZE
-	 * area are unreadable.
-	 */
-
-	/* can only fix I/O errors from here on */
-	if (sblock_bad->no_io_error_seen)
-		goto did_not_correct_error;
-
-	success = 1;
-	for (page_num = 0; page_num < sblock_bad->page_count; page_num++) {
-		struct scrub_page *page_bad = sblock_bad->pagev + page_num;
-
-		if (!page_bad->io_error)
-			continue;
-
-		for (mirror_index = 0;
-		     mirror_index < BTRFS_MAX_MIRRORS &&
-		     sblocks_for_recheck[mirror_index].page_count > 0;
-		     mirror_index++) {
-			struct scrub_block *sblock_other = sblocks_for_recheck +
-							   mirror_index;
-			struct scrub_page *page_other = sblock_other->pagev +
-							page_num;
-
-			if (!page_other->io_error) {
-				ret = scrub_repair_page_from_good_copy(
-					sblock_bad, sblock_other, page_num, 0);
-				if (0 == ret) {
-					page_bad->io_error = 0;
-					break; /* succeeded for this page */
-				}
-			}
-		}
-
-		if (page_bad->io_error) {
-			/* did not find a mirror to copy the page from */
-			success = 0;
-		}
-	}
-
-	if (success) {
-		if (is_metadata || have_csum) {
-			/*
-			 * need to verify the checksum now that all
-			 * sectors on disk are repaired (the write
-			 * request for data to be repaired is on its way).
-			 * Just be lazy and use scrub_recheck_block()
-			 * which re-reads the data before the checksum
-			 * is verified, but most likely the data comes out
-			 * of the page cache.
-			 */
-			ret = scrub_recheck_block(fs_info, sblock_bad,
-						  is_metadata, have_csum, csum,
-						  generation, sdev->csum_size);
-			if (!ret && !sblock_bad->header_error &&
-			    !sblock_bad->checksum_error &&
-			    sblock_bad->no_io_error_seen)
-				goto corrected_error;
-			else
-				goto did_not_correct_error;
-		} else {
-corrected_error:
-			spin_lock(&sdev->stat_lock);
-			sdev->stat.corrected_errors++;
-			spin_unlock(&sdev->stat_lock);
-			printk_ratelimited(KERN_ERR
-				"btrfs: fixed up error at logical %llu on dev %s\n",
-				(unsigned long long)logical, sdev->dev->name);
-		}
-	} else {
-did_not_correct_error:
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.uncorrectable_errors++;
-		spin_unlock(&sdev->stat_lock);
-		printk_ratelimited(KERN_ERR
-			"btrfs: unable to fixup (regular) error at logical %llu on dev %s\n",
-			(unsigned long long)logical, sdev->dev->name);
-	}
-
-out:
-	if (sblocks_for_recheck) {
-		for (mirror_index = 0; mirror_index < BTRFS_MAX_MIRRORS;
-		     mirror_index++) {
-			struct scrub_block *sblock = sblocks_for_recheck +
-						     mirror_index;
-			int page_index;
-
-			for (page_index = 0; page_index < SCRUB_PAGES_PER_BIO;
-			     page_index++)
-				if (sblock->pagev[page_index].page)
-					__free_page(
-						sblock->pagev[page_index].page);
-		}
-		kfree(sblocks_for_recheck);
-	}
-
-	return 0;
-}
-
-static int scrub_setup_recheck_block(struct scrub_dev *sdev,
-				     struct btrfs_mapping_tree *map_tree,
-				     u64 length, u64 logical,
-				     struct scrub_block *sblocks_for_recheck)
-{
-	int page_index;
-	int mirror_index;
-	int ret;
-
-	/*
-	 * note: the three members sdev, ref_count and outstanding_pages
-	 * are not used (and not set) in the blocks that are used for
-	 * the recheck procedure
-	 */
-
-	page_index = 0;
-	while (length > 0) {
-		u64 sublen = min_t(u64, length, PAGE_SIZE);
-		u64 mapped_length = sublen;
-		struct btrfs_bio *bbio = NULL;
-
-		/*
-		 * with a length of PAGE_SIZE, each returned stripe
-		 * represents one mirror
-		 */
-		ret = btrfs_map_block(map_tree, WRITE, logical, &mapped_length,
-				      &bbio, 0);
-		if (ret || !bbio || mapped_length < sublen) {
-			kfree(bbio);
-			return -EIO;
-		}
-
-		BUG_ON(page_index >= SCRUB_PAGES_PER_BIO);
-		for (mirror_index = 0; mirror_index < (int)bbio->num_stripes;
-		     mirror_index++) {
-			struct scrub_block *sblock;
-			struct scrub_page *page;
-
-			if (mirror_index >= BTRFS_MAX_MIRRORS)
-				continue;
-
-			sblock = sblocks_for_recheck + mirror_index;
-			page = sblock->pagev + page_index;
-			page->logical = logical;
-			page->physical = bbio->stripes[mirror_index].physical;
-			/* for missing devices, bdev is NULL */
-			page->bdev = bbio->stripes[mirror_index].dev->bdev;
-			page->mirror_num = mirror_index + 1;
-			page->page = alloc_page(GFP_NOFS);
-			if (!page->page) {
-				spin_lock(&sdev->stat_lock);
-				sdev->stat.malloc_errors++;
-				spin_unlock(&sdev->stat_lock);
-				return -ENOMEM;
-			}
-			sblock->page_count++;
-		}
-		kfree(bbio);
-		length -= sublen;
-		logical += sublen;
-		page_index++;
-	}
-
-	return 0;
-}
-
-/*
- * this function will check the on disk data for checksum errors, header
- * errors and read I/O errors. If any I/O errors happen, the exact pages
- * which are errored are marked as being bad. The goal is to enable scrub
- * to take those pages that are not errored from all the mirrors so that
- * the pages that are errored in the just handled mirror can be repaired.
- */
-static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
-			       struct scrub_block *sblock, int is_metadata,
-			       int have_csum, u8 *csum, u64 generation,
-			       u16 csum_size)
-{
-	int page_num;
-
-	sblock->no_io_error_seen = 1;
-	sblock->header_error = 0;
-	sblock->checksum_error = 0;
-
-	for (page_num = 0; page_num < sblock->page_count; page_num++) {
-		struct bio *bio;
-		int ret;
-		struct scrub_page *page = sblock->pagev + page_num;
-		DECLARE_COMPLETION_ONSTACK(complete);
-
-		if (page->bdev == NULL) {
-			page->io_error = 1;
-			sblock->no_io_error_seen = 0;
-			continue;
-		}
-
-		BUG_ON(!page->page);
-		bio = bio_alloc(GFP_NOFS, 1);
-		if (!bio)
-			return -EIO;
-		bio->bi_bdev = page->bdev;
-		bio->bi_sector = page->physical >> 9;
-		bio->bi_end_io = scrub_complete_bio_end_io;
-		bio->bi_private = &complete;
-
-		ret = bio_add_page(bio, page->page, PAGE_SIZE, 0);
-		if (PAGE_SIZE != ret) {
-			bio_put(bio);
-			return -EIO;
-		}
-		btrfsic_submit_bio(READ, bio);
-
-		/* this will also unplug the queue */
-		wait_for_completion(&complete);
-
-		page->io_error = !test_bit(BIO_UPTODATE, &bio->bi_flags);
-		if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
-			sblock->no_io_error_seen = 0;
-		bio_put(bio);
-	}
-
-	if (sblock->no_io_error_seen)
-		scrub_recheck_block_checksum(fs_info, sblock, is_metadata,
-					     have_csum, csum, generation,
-					     csum_size);
-
-	return 0;
-}
-
-static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
-					 struct scrub_block *sblock,
-					 int is_metadata, int have_csum,
-					 const u8 *csum, u64 generation,
-					 u16 csum_size)
-{
-	int page_num;
-	u8 calculated_csum[BTRFS_CSUM_SIZE];
-	u32 crc = ~(u32)0;
-	struct btrfs_root *root = fs_info->extent_root;
-	void *mapped_buffer;
-
-	BUG_ON(!sblock->pagev[0].page);
-	if (is_metadata) {
-		struct btrfs_header *h;
-
-		mapped_buffer = kmap_atomic(sblock->pagev[0].page);
-		h = (struct btrfs_header *)mapped_buffer;
-
-		if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr) ||
-		    generation != le64_to_cpu(h->generation) ||
-		    memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE) ||
-		    memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
-			   BTRFS_UUID_SIZE))
-			sblock->header_error = 1;
-		csum = h->csum;
-	} else {
-		if (!have_csum)
-			return;
-
-		mapped_buffer = kmap_atomic(sblock->pagev[0].page);
-	}
-
-	for (page_num = 0;;) {
-		if (page_num == 0 && is_metadata)
-			crc = btrfs_csum_data(root,
-				((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE,
-				crc, PAGE_SIZE - BTRFS_CSUM_SIZE);
-		else
-			crc = btrfs_csum_data(root, mapped_buffer, crc,
-					      PAGE_SIZE);
-
-		kunmap_atomic(mapped_buffer);
-		page_num++;
-		if (page_num >= sblock->page_count)
-			break;
-		BUG_ON(!sblock->pagev[page_num].page);
-
-		mapped_buffer = kmap_atomic(sblock->pagev[page_num].page);
-	}
-
-	btrfs_csum_final(crc, calculated_csum);
-	if (memcmp(calculated_csum, csum, csum_size))
-		sblock->checksum_error = 1;
-}
-
-static void scrub_complete_bio_end_io(struct bio *bio, int err)
-{
-	complete((struct completion *)bio->bi_private);
-}
-
-static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
-					     struct scrub_block *sblock_good,
-					     int force_write)
-{
-	int page_num;
-	int ret = 0;
-
-	for (page_num = 0; page_num < sblock_bad->page_count; page_num++) {
-		int ret_sub;
-
-		ret_sub = scrub_repair_page_from_good_copy(sblock_bad,
-							   sblock_good,
-							   page_num,
-							   force_write);
-		if (ret_sub)
-			ret = ret_sub;
-	}
-
-	return ret;
-}
-
-static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
-					    struct scrub_block *sblock_good,
-					    int page_num, int force_write)
-{
-	struct scrub_page *page_bad = sblock_bad->pagev + page_num;
-	struct scrub_page *page_good = sblock_good->pagev + page_num;
-
-	BUG_ON(sblock_bad->pagev[page_num].page == NULL);
-	BUG_ON(sblock_good->pagev[page_num].page == NULL);
-	if (force_write || sblock_bad->header_error ||
-	    sblock_bad->checksum_error || page_bad->io_error) {
-		struct bio *bio;
-		int ret;
-		DECLARE_COMPLETION_ONSTACK(complete);
-
-		bio = bio_alloc(GFP_NOFS, 1);
-		if (!bio)
-			return -EIO;
-		bio->bi_bdev = page_bad->bdev;
-		bio->bi_sector = page_bad->physical >> 9;
-		bio->bi_end_io = scrub_complete_bio_end_io;
-		bio->bi_private = &complete;
-
-		ret = bio_add_page(bio, page_good->page, PAGE_SIZE, 0);
-		if (PAGE_SIZE != ret) {
-			bio_put(bio);
-			return -EIO;
-		}
-		btrfsic_submit_bio(WRITE, bio);
-
-		/* this will also unplug the queue */
-		wait_for_completion(&complete);
-		bio_put(bio);
-	}
-
-	return 0;
-}
-
-static void scrub_checksum(struct scrub_block *sblock)
-{
-	u64 flags;
-	int ret;
-
-	BUG_ON(sblock->page_count < 1);
-	flags = sblock->pagev[0].flags;
-	ret = 0;
-	if (flags & BTRFS_EXTENT_FLAG_DATA)
-		ret = scrub_checksum_data(sblock);
-	else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
-		ret = scrub_checksum_tree_block(sblock);
-	else if (flags & BTRFS_EXTENT_FLAG_SUPER)
-		(void)scrub_checksum_super(sblock);
-	else
-		WARN_ON(1);
-	if (ret)
-		scrub_handle_errored_block(sblock);
-}
-
-static int scrub_checksum_data(struct scrub_block *sblock)
-{
-	struct scrub_dev *sdev = sblock->sdev;
-	u8 csum[BTRFS_CSUM_SIZE];
-	u8 *on_disk_csum;
-	struct page *page;
-	void *buffer;
-	u32 crc = ~(u32)0;
-	int fail = 0;
-	struct btrfs_root *root = sdev->dev->dev_root;
-	u64 len;
-	int index;
-
-	BUG_ON(sblock->page_count < 1);
-	if (!sblock->pagev[0].have_csum)
-		return 0;
-
-	on_disk_csum = sblock->pagev[0].csum;
-	page = sblock->pagev[0].page;
-	buffer = kmap_atomic(page);
-
-	len = sdev->sectorsize;
-	index = 0;
-	for (;;) {
-		u64 l = min_t(u64, len, PAGE_SIZE);
-
-		crc = btrfs_csum_data(root, buffer, crc, l);
-		kunmap_atomic(buffer);
-		len -= l;
-		if (len == 0)
-			break;
-		index++;
-		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
-		buffer = kmap_atomic(page);
-	}
-
-	btrfs_csum_final(crc, csum);
-	if (memcmp(csum, on_disk_csum, sdev->csum_size))
-		fail = 1;
-
-	return fail;
-}
-
-static int scrub_checksum_tree_block(struct scrub_block *sblock)
-{
-	struct scrub_dev *sdev = sblock->sdev;
-	struct btrfs_header *h;
-	struct btrfs_root *root = sdev->dev->dev_root;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	u8 calculated_csum[BTRFS_CSUM_SIZE];
-	u8 on_disk_csum[BTRFS_CSUM_SIZE];
-	struct page *page;
-	void *mapped_buffer;
-	u64 mapped_size;
-	void *p;
-	u32 crc = ~(u32)0;
-	int fail = 0;
-	int crc_fail = 0;
-	u64 len;
-	int index;
-
-	BUG_ON(sblock->page_count < 1);
-	page = sblock->pagev[0].page;
-	mapped_buffer = kmap_atomic(page);
-	h = (struct btrfs_header *)mapped_buffer;
-	memcpy(on_disk_csum, h->csum, sdev->csum_size);
-
-	/*
-	 * we don't use the getter functions here, as we
-	 * a) don't have an extent buffer and
-	 * b) the page is already kmapped
-	 */
-
-	if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr))
-		++fail;
-
-	if (sblock->pagev[0].generation != le64_to_cpu(h->generation))
-		++fail;
-
-	if (memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
-		++fail;
-
-	if (memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
-		   BTRFS_UUID_SIZE))
-		++fail;
-
-	BUG_ON(sdev->nodesize != sdev->leafsize);
-	len = sdev->nodesize - BTRFS_CSUM_SIZE;
-	mapped_size = PAGE_SIZE - BTRFS_CSUM_SIZE;
-	p = ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE;
-	index = 0;
-	for (;;) {
-		u64 l = min_t(u64, len, mapped_size);
-
-		crc = btrfs_csum_data(root, p, crc, l);
-		kunmap_atomic(mapped_buffer);
-		len -= l;
-		if (len == 0)
-			break;
-		index++;
-		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
-		mapped_buffer = kmap_atomic(page);
-		mapped_size = PAGE_SIZE;
-		p = mapped_buffer;
-	}
-
-	btrfs_csum_final(crc, calculated_csum);
-	if (memcmp(calculated_csum, on_disk_csum, sdev->csum_size))
-		++crc_fail;
-
-	return fail || crc_fail;
-}
-
-static int scrub_checksum_super(struct scrub_block *sblock)
-{
-	struct btrfs_super_block *s;
-	struct scrub_dev *sdev = sblock->sdev;
-	struct btrfs_root *root = sdev->dev->dev_root;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	u8 calculated_csum[BTRFS_CSUM_SIZE];
-	u8 on_disk_csum[BTRFS_CSUM_SIZE];
-	struct page *page;
-	void *mapped_buffer;
-	u64 mapped_size;
-	void *p;
-	u32 crc = ~(u32)0;
-	int fail = 0;
-	u64 len;
-	int index;
-
-	BUG_ON(sblock->page_count < 1);
-	page = sblock->pagev[0].page;
-	mapped_buffer = kmap_atomic(page);
-	s = (struct btrfs_super_block *)mapped_buffer;
-	memcpy(on_disk_csum, s->csum, sdev->csum_size);
-
-	if (sblock->pagev[0].logical != le64_to_cpu(s->bytenr))
-		++fail;
-
-	if (sblock->pagev[0].generation != le64_to_cpu(s->generation))
-		++fail;
-
-	if (memcmp(s->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
-		++fail;
-
-	len = BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE;
-	mapped_size = PAGE_SIZE - BTRFS_CSUM_SIZE;
-	p = ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE;
-	index = 0;
-	for (;;) {
-		u64 l = min_t(u64, len, mapped_size);
-
-		crc = btrfs_csum_data(root, p, crc, l);
-		kunmap_atomic(mapped_buffer);
-		len -= l;
-		if (len == 0)
-			break;
-		index++;
-		BUG_ON(index >= sblock->page_count);
-		BUG_ON(!sblock->pagev[index].page);
-		page = sblock->pagev[index].page;
-		mapped_buffer = kmap_atomic(page);
-		mapped_size = PAGE_SIZE;
-		p = mapped_buffer;
-	}
-
-	btrfs_csum_final(crc, calculated_csum);
-	if (memcmp(calculated_csum, on_disk_csum, sdev->csum_size))
-		++fail;
-
-	if (fail) {
-		/*
-		 * if we find an error in a super block, we just report it.
-		 * They will get written with the next transaction commit
-		 * anyway
-		 */
-		spin_lock(&sdev->stat_lock);
-		++sdev->stat.super_errors;
-		spin_unlock(&sdev->stat_lock);
-	}
-
-	return fail;
-}
-
-static void scrub_block_get(struct scrub_block *sblock)
-{
-	atomic_inc(&sblock->ref_count);
-}
-
-static void scrub_block_put(struct scrub_block *sblock)
-{
-	if (atomic_dec_and_test(&sblock->ref_count)) {
-		int i;
-
-		for (i = 0; i < sblock->page_count; i++)
-			if (sblock->pagev[i].page)
-				__free_page(sblock->pagev[i].page);
-		kfree(sblock);
-	}
-}
-
-static void scrub_submit(struct scrub_dev *sdev)
-{
-	struct scrub_bio *sbio;
-
-	if (sdev->curr == -1)
-		return;
-
-	sbio = sdev->bios[sdev->curr];
-	sdev->curr = -1;
-	atomic_inc(&sdev->in_flight);
-
-	btrfsic_submit_bio(READ, sbio->bio);
-}
-
-static int scrub_add_page_to_bio(struct scrub_dev *sdev,
-				 struct scrub_page *spage)
-{
-	struct scrub_block *sblock = spage->sblock;
-	struct scrub_bio *sbio;
-	int ret;
-
-again:
-	/*
-	 * grab a fresh bio or wait for one to become available
-	 */
-	while (sdev->curr == -1) {
-		spin_lock(&sdev->list_lock);
-		sdev->curr = sdev->first_free;
-		if (sdev->curr != -1) {
-			sdev->first_free = sdev->bios[sdev->curr]->next_free;
-			sdev->bios[sdev->curr]->next_free = -1;
-			sdev->bios[sdev->curr]->page_count = 0;
-			spin_unlock(&sdev->list_lock);
-		} else {
-			spin_unlock(&sdev->list_lock);
-			wait_event(sdev->list_wait, sdev->first_free != -1);
-		}
-	}
-	sbio = sdev->bios[sdev->curr];
-	if (sbio->page_count == 0) {
-		struct bio *bio;
-
-		sbio->physical = spage->physical;
-		sbio->logical = spage->logical;
-		bio = sbio->bio;
-		if (!bio) {
-			bio = bio_alloc(GFP_NOFS, sdev->pages_per_bio);
-			if (!bio)
-				return -ENOMEM;
-			sbio->bio = bio;
-		}
-
-		bio->bi_private = sbio;
-		bio->bi_end_io = scrub_bio_end_io;
-		bio->bi_bdev = sdev->dev->bdev;
-		bio->bi_sector = spage->physical >> 9;
-		sbio->err = 0;
-	} else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
-		   spage->physical ||
-		   sbio->logical + sbio->page_count * PAGE_SIZE !=
-		   spage->logical) {
-		scrub_submit(sdev);
-		goto again;
-	}
-
-	sbio->pagev[sbio->page_count] = spage;
-	ret = bio_add_page(sbio->bio, spage->page, PAGE_SIZE, 0);
-	if (ret != PAGE_SIZE) {
-		if (sbio->page_count < 1) {
-			bio_put(sbio->bio);
-			sbio->bio = NULL;
-			return -EIO;
-		}
-		scrub_submit(sdev);
-		goto again;
-	}
-
-	scrub_block_get(sblock); /* one for the added page */
-	atomic_inc(&sblock->outstanding_pages);
-	sbio->page_count++;
-	if (sbio->page_count == sdev->pages_per_bio)
-		scrub_submit(sdev);
-
-	return 0;
-}
-
-static int scrub_pages(struct scrub_dev *sdev, u64 logical, u64 len,
-		       u64 physical, u64 flags, u64 gen, int mirror_num,
-		       u8 *csum, int force)
-{
-	struct scrub_block *sblock;
-	int index;
-
-	sblock = kzalloc(sizeof(*sblock), GFP_NOFS);
-	if (!sblock) {
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.malloc_errors++;
-		spin_unlock(&sdev->stat_lock);
-		return -ENOMEM;
-	}
-
-	/* one ref inside this function, plus one for each page later on */
-	atomic_set(&sblock->ref_count, 1);
-	sblock->sdev = sdev;
-	sblock->no_io_error_seen = 1;
-
-	for (index = 0; len > 0; index++) {
-		struct scrub_page *spage = sblock->pagev + index;
-		u64 l = min_t(u64, len, PAGE_SIZE);
-
-		BUG_ON(index >= SCRUB_MAX_PAGES_PER_BLOCK);
-		spage->page = alloc_page(GFP_NOFS);
-		if (!spage->page) {
-			spin_lock(&sdev->stat_lock);
-			sdev->stat.malloc_errors++;
-			spin_unlock(&sdev->stat_lock);
-			while (index > 0) {
-				index--;
-				__free_page(sblock->pagev[index].page);
-			}
-			kfree(sblock);
-			return -ENOMEM;
-		}
-		spage->sblock = sblock;
-		spage->bdev = sdev->dev->bdev;
-		spage->flags = flags;
-		spage->generation = gen;
-		spage->logical = logical;
-		spage->physical = physical;
-		spage->mirror_num = mirror_num;
-		if (csum) {
-			spage->have_csum = 1;
-			memcpy(spage->csum, csum, sdev->csum_size);
-		} else {
-			spage->have_csum = 0;
-		}
-		sblock->page_count++;
-		len -= l;
-		logical += l;
-		physical += l;
-	}
-
-	BUG_ON(sblock->page_count == 0);
-	for (index = 0; index < sblock->page_count; index++) {
-		struct scrub_page *spage = sblock->pagev + index;
-		int ret;
-
-		ret = scrub_add_page_to_bio(sdev, spage);
-		if (ret) {
-			scrub_block_put(sblock);
-			return ret;
-		}
-	}
-
-	if (force)
-		scrub_submit(sdev);
-
-	/* last one frees, either here or in bio completion for last page */
-	scrub_block_put(sblock);
-	return 0;
-}
-
-static void scrub_bio_end_io(struct bio *bio, int err)
-{
-	struct scrub_bio *sbio = bio->bi_private;
-	struct scrub_dev *sdev = sbio->sdev;
-	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
-
-	sbio->err = err;
-	sbio->bio = bio;
-
-	btrfs_queue_worker(&fs_info->scrub_workers, &sbio->work);
-}
-
-static void scrub_bio_end_io_worker(struct btrfs_work *work)
-{
-	struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
-	struct scrub_dev *sdev = sbio->sdev;
-	int i;
-
-	BUG_ON(sbio->page_count > SCRUB_PAGES_PER_BIO);
-	if (sbio->err) {
-		for (i = 0; i < sbio->page_count; i++) {
-			struct scrub_page *spage = sbio->pagev[i];
-
-			spage->io_error = 1;
-			spage->sblock->no_io_error_seen = 0;
-		}
-	}
-
-	/* now complete the scrub_block items that have all pages completed */
-	for (i = 0; i < sbio->page_count; i++) {
-		struct scrub_page *spage = sbio->pagev[i];
-		struct scrub_block *sblock = spage->sblock;
-
-		if (atomic_dec_and_test(&sblock->outstanding_pages))
-			scrub_block_complete(sblock);
-		scrub_block_put(sblock);
-	}
-
-	if (sbio->err) {
-		/* what is this good for??? */
-		sbio->bio->bi_flags &= ~(BIO_POOL_MASK - 1);
-		sbio->bio->bi_flags |= 1 << BIO_UPTODATE;
-		sbio->bio->bi_phys_segments = 0;
-		sbio->bio->bi_idx = 0;
-
-		for (i = 0; i < sbio->page_count; i++) {
-			struct bio_vec *bi;
-			bi = &sbio->bio->bi_io_vec[i];
-			bi->bv_offset = 0;
-			bi->bv_len = PAGE_SIZE;
-		}
-	}
-
-	bio_put(sbio->bio);
-	sbio->bio = NULL;
-	spin_lock(&sdev->list_lock);
-	sbio->next_free = sdev->first_free;
-	sdev->first_free = sbio->index;
-	spin_unlock(&sdev->list_lock);
-	atomic_dec(&sdev->in_flight);
-	wake_up(&sdev->list_wait);
-}
-
-static void scrub_block_complete(struct scrub_block *sblock)
-{
-	if (!sblock->no_io_error_seen)
-		scrub_handle_errored_block(sblock);
-	else
-		scrub_checksum(sblock);
-}
-
-static int scrub_find_csum(struct scrub_dev *sdev, u64 logical, u64 len,
-			   u8 *csum)
-{
-	struct btrfs_ordered_sum *sum = NULL;
-	int ret = 0;
-	unsigned long i;
-	unsigned long num_sectors;
-
-	while (!list_empty(&sdev->csum_list)) {
-		sum = list_first_entry(&sdev->csum_list,
-				       struct btrfs_ordered_sum, list);
-		if (sum->bytenr > logical)
-			return 0;
-		if (sum->bytenr + sum->len > logical)
-			break;
-
-		++sdev->stat.csum_discards;
-		list_del(&sum->list);
-		kfree(sum);
-		sum = NULL;
-	}
-	if (!sum)
-		return 0;
-
-	num_sectors = sum->len / sdev->sectorsize;
-	for (i = 0; i < num_sectors; ++i) {
-		if (sum->sums[i].bytenr == logical) {
-			memcpy(csum, &sum->sums[i].sum, sdev->csum_size);
-			ret = 1;
-			break;
-		}
-	}
-	if (ret && i == num_sectors - 1) {
-		list_del(&sum->list);
-		kfree(sum);
-	}
-	return ret;
-}
-
-/* scrub extent tries to collect up to 64 kB for each bio */
-static int scrub_extent(struct scrub_dev *sdev, u64 logical, u64 len,
-			u64 physical, u64 flags, u64 gen, int mirror_num)
-{
-	int ret;
-	u8 csum[BTRFS_CSUM_SIZE];
-	u32 blocksize;
-
-	if (flags & BTRFS_EXTENT_FLAG_DATA) {
-		blocksize = sdev->sectorsize;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.data_extents_scrubbed++;
-		sdev->stat.data_bytes_scrubbed += len;
-		spin_unlock(&sdev->stat_lock);
-	} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
-		BUG_ON(sdev->nodesize != sdev->leafsize);
-		blocksize = sdev->nodesize;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.tree_extents_scrubbed++;
-		sdev->stat.tree_bytes_scrubbed += len;
-		spin_unlock(&sdev->stat_lock);
-	} else {
-		blocksize = sdev->sectorsize;
-		BUG_ON(1);
-	}
-
-	while (len) {
-		u64 l = min_t(u64, len, blocksize);
-		int have_csum = 0;
-
-		if (flags & BTRFS_EXTENT_FLAG_DATA) {
-			/* push csums to sbio */
-			have_csum = scrub_find_csum(sdev, logical, l, csum);
-			if (have_csum == 0)
-				++sdev->stat.no_csum;
-		}
-		ret = scrub_pages(sdev, logical, l, physical, flags, gen,
-				  mirror_num, have_csum ? csum : NULL, 0);
-		if (ret)
-			return ret;
-		len -= l;
-		logical += l;
-		physical += l;
-	}
-	return 0;
-}
-
-static noinline_for_stack int scrub_stripe(struct scrub_dev *sdev,
-	struct map_lookup *map, int num, u64 base, u64 length)
-{
-	struct btrfs_path *path;
-	struct btrfs_fs_info *fs_info = sdev->dev->dev_root->fs_info;
-	struct btrfs_root *root = fs_info->extent_root;
-	struct btrfs_root *csum_root = fs_info->csum_root;
-	struct btrfs_extent_item *extent;
-	struct blk_plug plug;
-	u64 flags;
-	int ret;
-	int slot;
-	int i;
-	u64 nstripes;
-	struct extent_buffer *l;
-	struct btrfs_key key;
-	u64 physical;
-	u64 logical;
-	u64 generation;
-	int mirror_num;
-	struct reada_control *reada1;
-	struct reada_control *reada2;
-	struct btrfs_key key_start;
-	struct btrfs_key key_end;
-
-	u64 increment = map->stripe_len;
-	u64 offset;
-
-	nstripes = length;
-	offset = 0;
-	do_div(nstripes, map->stripe_len);
-	if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
-		offset = map->stripe_len * num;
-		increment = map->stripe_len * map->num_stripes;
-		mirror_num = 1;
-	} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
-		int factor = map->num_stripes / map->sub_stripes;
-		offset = map->stripe_len * (num / map->sub_stripes);
-		increment = map->stripe_len * factor;
-		mirror_num = num % map->sub_stripes + 1;
-	} else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
-		increment = map->stripe_len;
-		mirror_num = num % map->num_stripes + 1;
-	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
-		increment = map->stripe_len;
-		mirror_num = num % map->num_stripes + 1;
-	} else {
-		increment = map->stripe_len;
-		mirror_num = 1;
-	}
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	/*
-	 * work on commit root. The related disk blocks are static as
-	 * long as COW is applied. This means, it is save to rewrite
-	 * them to repair disk errors without any race conditions
-	 */
-	path->search_commit_root = 1;
-	path->skip_locking = 1;
-
-	/*
-	 * trigger the readahead for extent tree csum tree and wait for
-	 * completion. During readahead, the scrub is officially paused
-	 * to not hold off transaction commits
-	 */
-	logical = base + offset;
-
-	wait_event(sdev->list_wait,
-		   atomic_read(&sdev->in_flight) == 0);
-	atomic_inc(&fs_info->scrubs_paused);
-	wake_up(&fs_info->scrub_pause_wait);
-
-	/* FIXME it might be better to start readahead at commit root */
-	key_start.objectid = logical;
-	key_start.type = BTRFS_EXTENT_ITEM_KEY;
-	key_start.offset = (u64)0;
-	key_end.objectid = base + offset + nstripes * increment;
-	key_end.type = BTRFS_EXTENT_ITEM_KEY;
-	key_end.offset = (u64)0;
-	reada1 = btrfs_reada_add(root, &key_start, &key_end);
-
-	key_start.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-	key_start.type = BTRFS_EXTENT_CSUM_KEY;
-	key_start.offset = logical;
-	key_end.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
-	key_end.type = BTRFS_EXTENT_CSUM_KEY;
-	key_end.offset = base + offset + nstripes * increment;
-	reada2 = btrfs_reada_add(csum_root, &key_start, &key_end);
-
-	if (!IS_ERR(reada1))
-		btrfs_reada_wait(reada1);
-	if (!IS_ERR(reada2))
-		btrfs_reada_wait(reada2);
-
-	mutex_lock(&fs_info->scrub_lock);
-	while (atomic_read(&fs_info->scrub_pause_req)) {
-		mutex_unlock(&fs_info->scrub_lock);
-		wait_event(fs_info->scrub_pause_wait,
-		   atomic_read(&fs_info->scrub_pause_req) == 0);
-		mutex_lock(&fs_info->scrub_lock);
-	}
-	atomic_dec(&fs_info->scrubs_paused);
-	mutex_unlock(&fs_info->scrub_lock);
-	wake_up(&fs_info->scrub_pause_wait);
-
-	/*
-	 * collect all data csums for the stripe to avoid seeking during
-	 * the scrub. This might currently (crc32) end up to be about 1MB
-	 */
-	blk_start_plug(&plug);
-
-	/*
-	 * now find all extents for each stripe and scrub them
-	 */
-	logical = base + offset;
-	physical = map->stripes[num].physical;
-	ret = 0;
-	for (i = 0; i < nstripes; ++i) {
-		/*
-		 * canceled?
-		 */
-		if (atomic_read(&fs_info->scrub_cancel_req) ||
-		    atomic_read(&sdev->cancel_req)) {
-			ret = -ECANCELED;
-			goto out;
-		}
-		/*
-		 * check to see if we have to pause
-		 */
-		if (atomic_read(&fs_info->scrub_pause_req)) {
-			/* push queued extents */
-			scrub_submit(sdev);
-			wait_event(sdev->list_wait,
-				   atomic_read(&sdev->in_flight) == 0);
-			atomic_inc(&fs_info->scrubs_paused);
-			wake_up(&fs_info->scrub_pause_wait);
-			mutex_lock(&fs_info->scrub_lock);
-			while (atomic_read(&fs_info->scrub_pause_req)) {
-				mutex_unlock(&fs_info->scrub_lock);
-				wait_event(fs_info->scrub_pause_wait,
-				   atomic_read(&fs_info->scrub_pause_req) == 0);
-				mutex_lock(&fs_info->scrub_lock);
-			}
-			atomic_dec(&fs_info->scrubs_paused);
-			mutex_unlock(&fs_info->scrub_lock);
-			wake_up(&fs_info->scrub_pause_wait);
-		}
-
-		ret = btrfs_lookup_csums_range(csum_root, logical,
-					       logical + map->stripe_len - 1,
-					       &sdev->csum_list, 1);
-		if (ret)
-			goto out;
-
-		key.objectid = logical;
-		key.type = BTRFS_EXTENT_ITEM_KEY;
-		key.offset = (u64)0;
-
-		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-		if (ret < 0)
-			goto out;
-		if (ret > 0) {
-			ret = btrfs_previous_item(root, path, 0,
-						  BTRFS_EXTENT_ITEM_KEY);
-			if (ret < 0)
-				goto out;
-			if (ret > 0) {
-				/* there's no smaller item, so stick with the
-				 * larger one */
-				btrfs_release_path(path);
-				ret = btrfs_search_slot(NULL, root, &key,
-							path, 0, 0);
-				if (ret < 0)
-					goto out;
-			}
-		}
-
-		while (1) {
-			l = path->nodes[0];
-			slot = path->slots[0];
-			if (slot >= btrfs_header_nritems(l)) {
-				ret = btrfs_next_leaf(root, path);
-				if (ret == 0)
-					continue;
-				if (ret < 0)
-					goto out;
-
-				break;
-			}
-			btrfs_item_key_to_cpu(l, &key, slot);
-
-			if (key.objectid + key.offset <= logical)
-				goto next;
-
-			if (key.objectid >= logical + map->stripe_len)
-				break;
-
-			if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY)
-				goto next;
-
-			extent = btrfs_item_ptr(l, slot,
-						struct btrfs_extent_item);
-			flags = btrfs_extent_flags(l, extent);
-			generation = btrfs_extent_generation(l, extent);
-
-			if (key.objectid < logical &&
-			    (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
-				printk(KERN_ERR
-				       "btrfs scrub: tree block %llu spanning "
-				       "stripes, ignored. logical=%llu\n",
-				       (unsigned long long)key.objectid,
-				       (unsigned long long)logical);
-				goto next;
-			}
-
-			/*
-			 * trim extent to this stripe
-			 */
-			if (key.objectid < logical) {
-				key.offset -= logical - key.objectid;
-				key.objectid = logical;
-			}
-			if (key.objectid + key.offset >
-			    logical + map->stripe_len) {
-				key.offset = logical + map->stripe_len -
-					     key.objectid;
-			}
-
-			ret = scrub_extent(sdev, key.objectid, key.offset,
-					   key.objectid - logical + physical,
-					   flags, generation, mirror_num);
-			if (ret)
-				goto out;
-
-next:
-			path->slots[0]++;
-		}
-		btrfs_release_path(path);
-		logical += increment;
-		physical += map->stripe_len;
-		spin_lock(&sdev->stat_lock);
-		sdev->stat.last_physical = physical;
-		spin_unlock(&sdev->stat_lock);
-	}
-	/* push queued extents */
-	scrub_submit(sdev);
-
-out:
-	blk_finish_plug(&plug);
-	btrfs_free_path(path);
-	return ret < 0 ? ret : 0;
-}
-
-static noinline_for_stack int scrub_chunk(struct scrub_dev *sdev,
-	u64 chunk_tree, u64 chunk_objectid, u64 chunk_offset, u64 length,
-	u64 dev_offset)
-{
-	struct btrfs_mapping_tree *map_tree =
-		&sdev->dev->dev_root->fs_info->mapping_tree;
-	struct map_lookup *map;
-	struct extent_map *em;
-	int i;
-	int ret = -EINVAL;
-
-	read_lock(&map_tree->map_tree.lock);
-	em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
-	read_unlock(&map_tree->map_tree.lock);
-
-	if (!em)
-		return -EINVAL;
-
-	map = (struct map_lookup *)em->bdev;
-	if (em->start != chunk_offset)
-		goto out;
-
-	if (em->len < length)
-		goto out;
-
-	for (i = 0; i < map->num_stripes; ++i) {
-		if (map->stripes[i].dev == sdev->dev &&
-		    map->stripes[i].physical == dev_offset) {
-			ret = scrub_stripe(sdev, map, i, chunk_offset, length);
-			if (ret)
-				goto out;
-		}
-	}
-out:
-	free_extent_map(em);
-
-	return ret;
-}
-
-static noinline_for_stack
-int scrub_enumerate_chunks(struct scrub_dev *sdev, u64 start, u64 end)
-{
-	struct btrfs_dev_extent *dev_extent = NULL;
-	struct btrfs_path *path;
-	struct btrfs_root *root = sdev->dev->dev_root;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	u64 length;
-	u64 chunk_tree;
-	u64 chunk_objectid;
-	u64 chunk_offset;
-	int ret;
-	int slot;
-	struct extent_buffer *l;
-	struct btrfs_key key;
-	struct btrfs_key found_key;
-	struct btrfs_block_group_cache *cache;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	path->reada = 2;
-	path->search_commit_root = 1;
-	path->skip_locking = 1;
-
-	key.objectid = sdev->dev->devid;
-	key.offset = 0ull;
-	key.type = BTRFS_DEV_EXTENT_KEY;
-
-
-	while (1) {
-		ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-		if (ret < 0)
-			break;
-		if (ret > 0) {
-			if (path->slots[0] >=
-			    btrfs_header_nritems(path->nodes[0])) {
-				ret = btrfs_next_leaf(root, path);
-				if (ret)
-					break;
-			}
-		}
-
-		l = path->nodes[0];
-		slot = path->slots[0];
-
-		btrfs_item_key_to_cpu(l, &found_key, slot);
-
-		if (found_key.objectid != sdev->dev->devid)
-			break;
-
-		if (btrfs_key_type(&found_key) != BTRFS_DEV_EXTENT_KEY)
-			break;
-
-		if (found_key.offset >= end)
-			break;
-
-		if (found_key.offset < key.offset)
-			break;
-
-		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
-		length = btrfs_dev_extent_length(l, dev_extent);
-
-		if (found_key.offset + length <= start) {
-			key.offset = found_key.offset + length;
-			btrfs_release_path(path);
-			continue;
-		}
-
-		chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent);
-		chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent);
-		chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
-
-		/*
-		 * get a reference on the corresponding block group to prevent
-		 * the chunk from going away while we scrub it
-		 */
-		cache = btrfs_lookup_block_group(fs_info, chunk_offset);
-		if (!cache) {
-			ret = -ENOENT;
-			break;
-		}
-		ret = scrub_chunk(sdev, chunk_tree, chunk_objectid,
-				  chunk_offset, length, found_key.offset);
-		btrfs_put_block_group(cache);
-		if (ret)
-			break;
-
-		key.offset = found_key.offset + length;
-		btrfs_release_path(path);
-	}
-
-	btrfs_free_path(path);
-
-	/*
-	 * ret can still be 1 from search_slot or next_leaf,
-	 * that's not an error
-	 */
-	return ret < 0 ? ret : 0;
-}
-
-static noinline_for_stack int scrub_supers(struct scrub_dev *sdev)
-{
-	int	i;
-	u64	bytenr;
-	u64	gen;
-	int	ret;
-	struct btrfs_device *device = sdev->dev;
-	struct btrfs_root *root = device->dev_root;
-
-	if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
-		return -EIO;
-
-	gen = root->fs_info->last_trans_committed;
-
-	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
-		bytenr = btrfs_sb_offset(i);
-		if (bytenr + BTRFS_SUPER_INFO_SIZE > device->total_bytes)
-			break;
-
-		ret = scrub_pages(sdev, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
-				     BTRFS_EXTENT_FLAG_SUPER, gen, i, NULL, 1);
-		if (ret)
-			return ret;
-	}
-	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
-
-	return 0;
-}
-
-/*
- * get a reference count on fs_info->scrub_workers. start worker if necessary
- */
-static noinline_for_stack int scrub_workers_get(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	int ret = 0;
-
-	mutex_lock(&fs_info->scrub_lock);
-	if (fs_info->scrub_workers_refcnt == 0) {
-		btrfs_init_workers(&fs_info->scrub_workers, "scrub",
-			   fs_info->thread_pool_size, &fs_info->generic_worker);
-		fs_info->scrub_workers.idle_thresh = 4;
-		ret = btrfs_start_workers(&fs_info->scrub_workers);
-		if (ret)
-			goto out;
-	}
-	++fs_info->scrub_workers_refcnt;
-out:
-	mutex_unlock(&fs_info->scrub_lock);
-
-	return ret;
-}
-
-static noinline_for_stack void scrub_workers_put(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
-	mutex_lock(&fs_info->scrub_lock);
-	if (--fs_info->scrub_workers_refcnt == 0)
-		btrfs_stop_workers(&fs_info->scrub_workers);
-	WARN_ON(fs_info->scrub_workers_refcnt < 0);
-	mutex_unlock(&fs_info->scrub_lock);
-}
-
-
-int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
-		    struct btrfs_scrub_progress *progress, int readonly)
-{
-	struct scrub_dev *sdev;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	int ret;
-	struct btrfs_device *dev;
-
-	if (btrfs_fs_closing(root->fs_info))
-		return -EINVAL;
-
-	/*
-	 * check some assumptions
-	 */
-	if (root->nodesize != root->leafsize) {
-		printk(KERN_ERR
-		       "btrfs_scrub: size assumption nodesize == leafsize (%d == %d) fails\n",
-		       root->nodesize, root->leafsize);
-		return -EINVAL;
-	}
-
-	if (root->nodesize > BTRFS_STRIPE_LEN) {
-		/*
-		 * in this case scrub is unable to calculate the checksum
-		 * the way scrub is implemented. Do not handle this
-		 * situation at all because it won't ever happen.
-		 */
-		printk(KERN_ERR
-		       "btrfs_scrub: size assumption nodesize <= BTRFS_STRIPE_LEN (%d <= %d) fails\n",
-		       root->nodesize, BTRFS_STRIPE_LEN);
-		return -EINVAL;
-	}
-
-	if (root->sectorsize != PAGE_SIZE) {
-		/* not supported for data w/o checksums */
-		printk(KERN_ERR
-		       "btrfs_scrub: size assumption sectorsize != PAGE_SIZE (%d != %lld) fails\n",
-		       root->sectorsize, (unsigned long long)PAGE_SIZE);
-		return -EINVAL;
-	}
-
-	ret = scrub_workers_get(root);
-	if (ret)
-		return ret;
-
-	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
-	if (!dev || dev->missing) {
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return -ENODEV;
-	}
-	mutex_lock(&fs_info->scrub_lock);
-
-	if (!dev->in_fs_metadata) {
-		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return -ENODEV;
-	}
-
-	if (dev->scrub_device) {
-		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return -EINPROGRESS;
-	}
-	sdev = scrub_setup_dev(dev);
-	if (IS_ERR(sdev)) {
-		mutex_unlock(&fs_info->scrub_lock);
-		mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-		scrub_workers_put(root);
-		return PTR_ERR(sdev);
-	}
-	sdev->readonly = readonly;
-	dev->scrub_device = sdev;
-
-	atomic_inc(&fs_info->scrubs_running);
-	mutex_unlock(&fs_info->scrub_lock);
-	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-
-	down_read(&fs_info->scrub_super_lock);
-	ret = scrub_supers(sdev);
-	up_read(&fs_info->scrub_super_lock);
-
-	if (!ret)
-		ret = scrub_enumerate_chunks(sdev, start, end);
-
-	wait_event(sdev->list_wait, atomic_read(&sdev->in_flight) == 0);
-	atomic_dec(&fs_info->scrubs_running);
-	wake_up(&fs_info->scrub_pause_wait);
-
-	wait_event(sdev->list_wait, atomic_read(&sdev->fixup_cnt) == 0);
-
-	if (progress)
-		memcpy(progress, &sdev->stat, sizeof(*progress));
-
-	mutex_lock(&fs_info->scrub_lock);
-	dev->scrub_device = NULL;
-	mutex_unlock(&fs_info->scrub_lock);
-
-	scrub_free_dev(sdev);
-	scrub_workers_put(root);
-
-	return ret;
-}
-
-void btrfs_scrub_pause(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
-	mutex_lock(&fs_info->scrub_lock);
-	atomic_inc(&fs_info->scrub_pause_req);
-	while (atomic_read(&fs_info->scrubs_paused) !=
-	       atomic_read(&fs_info->scrubs_running)) {
-		mutex_unlock(&fs_info->scrub_lock);
-		wait_event(fs_info->scrub_pause_wait,
-			   atomic_read(&fs_info->scrubs_paused) ==
-			   atomic_read(&fs_info->scrubs_running));
-		mutex_lock(&fs_info->scrub_lock);
-	}
-	mutex_unlock(&fs_info->scrub_lock);
-}
-
-void btrfs_scrub_continue(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
-	atomic_dec(&fs_info->scrub_pause_req);
-	wake_up(&fs_info->scrub_pause_wait);
-}
-
-void btrfs_scrub_pause_super(struct btrfs_root *root)
-{
-	down_write(&root->fs_info->scrub_super_lock);
-}
-
-void btrfs_scrub_continue_super(struct btrfs_root *root)
-{
-	up_write(&root->fs_info->scrub_super_lock);
-}
-
-int __btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
-{
-
-	mutex_lock(&fs_info->scrub_lock);
-	if (!atomic_read(&fs_info->scrubs_running)) {
-		mutex_unlock(&fs_info->scrub_lock);
-		return -ENOTCONN;
-	}
-
-	atomic_inc(&fs_info->scrub_cancel_req);
-	while (atomic_read(&fs_info->scrubs_running)) {
-		mutex_unlock(&fs_info->scrub_lock);
-		wait_event(fs_info->scrub_pause_wait,
-			   atomic_read(&fs_info->scrubs_running) == 0);
-		mutex_lock(&fs_info->scrub_lock);
-	}
-	atomic_dec(&fs_info->scrub_cancel_req);
-	mutex_unlock(&fs_info->scrub_lock);
-
-	return 0;
-}
-
-int btrfs_scrub_cancel(struct btrfs_root *root)
-{
-	return __btrfs_scrub_cancel(root->fs_info);
-}
-
-int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct scrub_dev *sdev;
-
-	mutex_lock(&fs_info->scrub_lock);
-	sdev = dev->scrub_device;
-	if (!sdev) {
-		mutex_unlock(&fs_info->scrub_lock);
-		return -ENOTCONN;
-	}
-	atomic_inc(&sdev->cancel_req);
-	while (dev->scrub_device) {
-		mutex_unlock(&fs_info->scrub_lock);
-		wait_event(fs_info->scrub_pause_wait,
-			   dev->scrub_device == NULL);
-		mutex_lock(&fs_info->scrub_lock);
-	}
-	mutex_unlock(&fs_info->scrub_lock);
-
-	return 0;
-}
-
-int btrfs_scrub_cancel_devid(struct btrfs_root *root, u64 devid)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_device *dev;
-	int ret;
-
-	/*
-	 * we have to hold the device_list_mutex here so the device
-	 * does not go away in cancel_dev. FIXME: find a better solution
-	 */
-	mutex_lock(&fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
-	if (!dev) {
-		mutex_unlock(&fs_info->fs_devices->device_list_mutex);
-		return -ENODEV;
-	}
-	ret = btrfs_scrub_cancel_dev(root, dev);
-	mutex_unlock(&fs_info->fs_devices->device_list_mutex);
-
-	return ret;
-}
-
-int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
-			 struct btrfs_scrub_progress *progress)
-{
-	struct btrfs_device *dev;
-	struct scrub_dev *sdev = NULL;
-
-	mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
-	dev = btrfs_find_device(root, devid, NULL, NULL);
-	if (dev)
-		sdev = dev->scrub_device;
-	if (sdev)
-		memcpy(progress, &sdev->stat, sizeof(*progress));
-	mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
-
-	return dev ? (sdev ? 0 : -ENOTCONN) : -ENODEV;
-}