Merge branch 'master' of ssh://mason@master.kernel.org/pub/scm/linux/kernel/git/mason/btrfs-unstable

1 files changed, 2078 insertions, 0 deletions

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
new file mode 100644
index 000000000000..0be044bb6194
--- /dev/null
+++ b/fs/btrfs/disk-io.c
@@ -0,0 +1,2078 @@
+/*
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+
+#include <linux/version.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/scatterlist.h>
+#include <linux/swap.h>
+#include <linux/radix-tree.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h> // for block_sync_page
+#include <linux/workqueue.h>
+#include <linux/kthread.h>
+# include <linux/freezer.h>
+#include "crc32c.h"
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "btrfs_inode.h"
+#include "volumes.h"
+#include "print-tree.h"
+#include "async-thread.h"
+#include "locking.h"
+#include "ref-cache.h"
+#include "tree-log.h"
+
+#if 0
+static int check_tree_block(struct btrfs_root *root, struct extent_buffer *buf)
+{
+        if (extent_buffer_blocknr(buf) != btrfs_header_blocknr(buf)) {
+                printk(KERN_CRIT "buf blocknr(buf) is %llu, header is %llu\n",
+                       (unsigned long long)extent_buffer_blocknr(buf),
+                       (unsigned long long)btrfs_header_blocknr(buf));
+                return 1;
+        }
+        return 0;
+}
+#endif
+
+static struct extent_io_ops btree_extent_io_ops;
+static void end_workqueue_fn(struct btrfs_work *work);
+
+/*
+ * end_io_wq structs are used to do processing in task context when an IO is
+ * complete.  This is used during reads to verify checksums, and it is used
+ * by writes to insert metadata for new file extents after IO is complete.
+ */
+struct end_io_wq {
+        struct bio *bio;
+        bio_end_io_t *end_io;
+        void *private;
+        struct btrfs_fs_info *info;
+        int error;
+        int metadata;
+        struct list_head list;
+        struct btrfs_work work;
+};
+
+/*
+ * async submit bios are used to offload expensive checksumming
+ * onto the worker threads.  They checksum file and metadata bios
+ * just before they are sent down the IO stack.
+ */
+struct async_submit_bio {
+        struct inode *inode;
+        struct bio *bio;
+        struct list_head list;
+        extent_submit_bio_hook_t *submit_bio_hook;
+        int rw;
+        int mirror_num;
+        struct btrfs_work work;
+};
+
+/*
+ * extents on the btree inode are pretty simple, there's one extent
+ * that covers the entire device
+ */
+struct extent_map *btree_get_extent(struct inode *inode, struct page *page,
+                                    size_t page_offset, u64 start, u64 len,
+                                    int create)
+{
+        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
+        struct extent_map *em;
+        int ret;
+
+        spin_lock(&em_tree->lock);
+        em = lookup_extent_mapping(em_tree, start, len);
+        if (em) {
+                em->bdev =
+                        BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
+                spin_unlock(&em_tree->lock);
+                goto out;
+        }
+        spin_unlock(&em_tree->lock);
+
+        em = alloc_extent_map(GFP_NOFS);
+        if (!em) {
+                em = ERR_PTR(-ENOMEM);
+                goto out;
+        }
+        em->start = 0;
+        em->len = (u64)-1;
+        em->block_start = 0;
+        em->bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
+
+        spin_lock(&em_tree->lock);
+        ret = add_extent_mapping(em_tree, em);
+        if (ret == -EEXIST) {
+                u64 failed_start = em->start;
+                u64 failed_len = em->len;
+
+                printk("failed to insert %Lu %Lu -> %Lu into tree\n",
+                       em->start, em->len, em->block_start);
+                free_extent_map(em);
+                em = lookup_extent_mapping(em_tree, start, len);
+                if (em) {
+                        printk("after failing, found %Lu %Lu %Lu\n",
+                               em->start, em->len, em->block_start);
+                        ret = 0;
+                } else {
+                        em = lookup_extent_mapping(em_tree, failed_start,
+                                                   failed_len);
+                        if (em) {
+                                printk("double failure lookup gives us "
+                                       "%Lu %Lu -> %Lu\n", em->start,
+                                       em->len, em->block_start);
+                                free_extent_map(em);
+                        }
+                        ret = -EIO;
+                }
+        } else if (ret) {
+                free_extent_map(em);
+                em = NULL;
+        }
+        spin_unlock(&em_tree->lock);
+
+        if (ret)
+                em = ERR_PTR(ret);
+out:
+        return em;
+}
+
+u32 btrfs_csum_data(struct btrfs_root *root, char *data, u32 seed, size_t len)
+{
+        return btrfs_crc32c(seed, data, len);
+}
+
+void btrfs_csum_final(u32 crc, char *result)
+{
+        *(__le32 *)result = ~cpu_to_le32(crc);
+}
+
+/*
+ * compute the csum for a btree block, and either verify it or write it
+ * into the csum field of the block.
+ */
+static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
+                           int verify)
+{
+        char result[BTRFS_CRC32_SIZE];
+        unsigned long len;
+        unsigned long cur_len;
+        unsigned long offset = BTRFS_CSUM_SIZE;
+        char *map_token = NULL;
+        char *kaddr;
+        unsigned long map_start;
+        unsigned long map_len;
+        int err;
+        u32 crc = ~(u32)0;
+
+        len = buf->len - offset;
+        while(len > 0) {
+                err = map_private_extent_buffer(buf, offset, 32,
+                                        &map_token, &kaddr,
+                                        &map_start, &map_len, KM_USER0);
+                if (err) {
+                        printk("failed to map extent buffer! %lu\n",
+                               offset);
+                        return 1;
+                }
+                cur_len = min(len, map_len - (offset - map_start));
+                crc = btrfs_csum_data(root, kaddr + offset - map_start,
+                                      crc, cur_len);
+                len -= cur_len;
+                offset += cur_len;
+                unmap_extent_buffer(buf, map_token, KM_USER0);
+        }
+        btrfs_csum_final(crc, result);
+
+        if (verify) {
+                /* FIXME, this is not good */
+                if (memcmp_extent_buffer(buf, result, 0, BTRFS_CRC32_SIZE)) {
+                        u32 val;
+                        u32 found = 0;
+                        memcpy(&found, result, BTRFS_CRC32_SIZE);
+
+                        read_extent_buffer(buf, &val, 0, BTRFS_CRC32_SIZE);
+                        printk("btrfs: %s checksum verify failed on %llu "
+                               "wanted %X found %X level %d\n",
+                               root->fs_info->sb->s_id,
+                               buf->start, val, found, btrfs_header_level(buf));
+                        return 1;
+                }
+        } else {
+                write_extent_buffer(buf, result, 0, BTRFS_CRC32_SIZE);
+        }
+        return 0;
+}
+
+/*
+ * we can't consider a given block up to date unless the transid of the
+ * block matches the transid in the parent node's pointer.  This is how we
+ * detect blocks that either didn't get written at all or got written
+ * in the wrong place.
+ */
+static int verify_parent_transid(struct extent_io_tree *io_tree,
+                                 struct extent_buffer *eb, u64 parent_transid)
+{
+        int ret;
+
+        if (!parent_transid || btrfs_header_generation(eb) == parent_transid)
+                return 0;
+
+        lock_extent(io_tree, eb->start, eb->start + eb->len - 1, GFP_NOFS);
+        if (extent_buffer_uptodate(io_tree, eb) &&
+            btrfs_header_generation(eb) == parent_transid) {
+                ret = 0;
+                goto out;
+        }
+        printk("parent transid verify failed on %llu wanted %llu found %llu\n",
+               (unsigned long long)eb->start,
+               (unsigned long long)parent_transid,
+               (unsigned long long)btrfs_header_generation(eb));
+        ret = 1;
+        clear_extent_buffer_uptodate(io_tree, eb);
+out:
+        unlock_extent(io_tree, eb->start, eb->start + eb->len - 1,
+                      GFP_NOFS);
+        return ret;
+}
+
+/*
+ * helper to read a given tree block, doing retries as required when
+ * the checksums don't match and we have alternate mirrors to try.
+ */
+static int btree_read_extent_buffer_pages(struct btrfs_root *root,
+                                          struct extent_buffer *eb,
+                                          u64 start, u64 parent_transid)
+{
+        struct extent_io_tree *io_tree;
+        int ret;
+        int num_copies = 0;
+        int mirror_num = 0;
+
+        io_tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
+        while (1) {
+                ret = read_extent_buffer_pages(io_tree, eb, start, 1,
+                                               btree_get_extent, mirror_num);
+                if (!ret &&
+                    !verify_parent_transid(io_tree, eb, parent_transid))
+                        return ret;
+printk("read extent buffer pages failed with ret %d mirror no %d\n", ret, mirror_num);
+                num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
+                                              eb->start, eb->len);
+                if (num_copies == 1)
+                        return ret;
+
+                mirror_num++;
+                if (mirror_num > num_copies)
+                        return ret;
+        }
+        return -EIO;
+}
+
+/*
+ * checksum a dirty tree block before IO.  This has extra checks to make
+ * sure we only fill in the checksum field in the first page of a multi-page block
+ */
+int csum_dirty_buffer(struct btrfs_root *root, struct page *page)
+{
+        struct extent_io_tree *tree;
+        u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+        u64 found_start;
+        int found_level;
+        unsigned long len;
+        struct extent_buffer *eb;
+        int ret;
+
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+
+        if (page->private == EXTENT_PAGE_PRIVATE)
+                goto out;
+        if (!page->private)
+                goto out;
+        len = page->private >> 2;
+        if (len == 0) {
+                WARN_ON(1);
+        }
+        eb = alloc_extent_buffer(tree, start, len, page, GFP_NOFS);
+        ret = btree_read_extent_buffer_pages(root, eb, start + PAGE_CACHE_SIZE,
+                                             btrfs_header_generation(eb));
+        BUG_ON(ret);
+        found_start = btrfs_header_bytenr(eb);
+        if (found_start != start) {
+                printk("warning: eb start incorrect %Lu buffer %Lu len %lu\n",
+                       start, found_start, len);
+                WARN_ON(1);
+                goto err;
+        }
+        if (eb->first_page != page) {
+                printk("bad first page %lu %lu\n", eb->first_page->index,
+                       page->index);
+                WARN_ON(1);
+                goto err;
+        }
+        if (!PageUptodate(page)) {
+                printk("csum not up to date page %lu\n", page->index);
+                WARN_ON(1);
+                goto err;
+        }
+        found_level = btrfs_header_level(eb);
+
+        csum_tree_block(root, eb, 0);
+err:
+        free_extent_buffer(eb);
+out:
+        return 0;
+}
+
+int btree_readpage_end_io_hook(struct page *page, u64 start, u64 end,
+                               struct extent_state *state)
+{
+        struct extent_io_tree *tree;
+        u64 found_start;
+        int found_level;
+        unsigned long len;
+        struct extent_buffer *eb;
+        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+        int ret = 0;
+
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+        if (page->private == EXTENT_PAGE_PRIVATE)
+                goto out;
+        if (!page->private)
+                goto out;
+        len = page->private >> 2;
+        if (len == 0) {
+                WARN_ON(1);
+        }
+        eb = alloc_extent_buffer(tree, start, len, page, GFP_NOFS);
+
+        found_start = btrfs_header_bytenr(eb);
+        if (found_start != start) {
+                printk("bad tree block start %llu %llu\n",
+                       (unsigned long long)found_start,
+                       (unsigned long long)eb->start);
+                ret = -EIO;
+                goto err;
+        }
+        if (eb->first_page != page) {
+                printk("bad first page %lu %lu\n", eb->first_page->index,
+                       page->index);
+                WARN_ON(1);
+                ret = -EIO;
+                goto err;
+        }
+        if (memcmp_extent_buffer(eb, root->fs_info->fsid,
+                                 (unsigned long)btrfs_header_fsid(eb),
+                                 BTRFS_FSID_SIZE)) {
+                printk("bad fsid on block %Lu\n", eb->start);
+                ret = -EIO;
+                goto err;
+        }
+        found_level = btrfs_header_level(eb);
+
+        ret = csum_tree_block(root, eb, 1);
+        if (ret)
+                ret = -EIO;
+
+        end = min_t(u64, eb->len, PAGE_CACHE_SIZE);
+        end = eb->start + end - 1;
+err:
+        free_extent_buffer(eb);
+out:
+        return ret;
+}
+
+static void end_workqueue_bio(struct bio *bio, int err)
+{
+        struct end_io_wq *end_io_wq = bio->bi_private;
+        struct btrfs_fs_info *fs_info;
+
+        fs_info = end_io_wq->info;
+        end_io_wq->error = err;
+        end_io_wq->work.func = end_workqueue_fn;
+        end_io_wq->work.flags = 0;
+        if (bio->bi_rw & (1 << BIO_RW))
+                btrfs_queue_worker(&fs_info->endio_write_workers,
+                                   &end_io_wq->work);
+        else
+                btrfs_queue_worker(&fs_info->endio_workers, &end_io_wq->work);
+}
+
+int btrfs_bio_wq_end_io(struct btrfs_fs_info *info, struct bio *bio,
+                        int metadata)
+{
+        struct end_io_wq *end_io_wq;
+        end_io_wq = kmalloc(sizeof(*end_io_wq), GFP_NOFS);
+        if (!end_io_wq)
+                return -ENOMEM;
+
+        end_io_wq->private = bio->bi_private;
+        end_io_wq->end_io = bio->bi_end_io;
+        end_io_wq->info = info;
+        end_io_wq->error = 0;
+        end_io_wq->bio = bio;
+        end_io_wq->metadata = metadata;
+
+        bio->bi_private = end_io_wq;
+        bio->bi_end_io = end_workqueue_bio;
+        return 0;
+}
+
+unsigned long btrfs_async_submit_limit(struct btrfs_fs_info *info)
+{
+        unsigned long limit = min_t(unsigned long,
+                                    info->workers.max_workers,
+                                    info->fs_devices->open_devices);
+        return 256 * limit;
+}
+
+int btrfs_congested_async(struct btrfs_fs_info *info, int iodone)
+{
+        return atomic_read(&info->nr_async_bios) >
+                btrfs_async_submit_limit(info);
+}
+
+static void run_one_async_submit(struct btrfs_work *work)
+{
+        struct btrfs_fs_info *fs_info;
+        struct async_submit_bio *async;
+        int limit;
+
+        async = container_of(work, struct  async_submit_bio, work);
+        fs_info = BTRFS_I(async->inode)->root->fs_info;
+
+        limit = btrfs_async_submit_limit(fs_info);
+        limit = limit * 2 / 3;
+
+        atomic_dec(&fs_info->nr_async_submits);
+
+        if (atomic_read(&fs_info->nr_async_submits) < limit &&
+            waitqueue_active(&fs_info->async_submit_wait))
+                wake_up(&fs_info->async_submit_wait);
+
+        async->submit_bio_hook(async->inode, async->rw, async->bio,
+                               async->mirror_num);
+        kfree(async);
+}
+
+int btrfs_wq_submit_bio(struct btrfs_fs_info *fs_info, struct inode *inode,
+                        int rw, struct bio *bio, int mirror_num,
+                        extent_submit_bio_hook_t *submit_bio_hook)
+{
+        struct async_submit_bio *async;
+        int limit = btrfs_async_submit_limit(fs_info);
+
+        async = kmalloc(sizeof(*async), GFP_NOFS);
+        if (!async)
+                return -ENOMEM;
+
+        async->inode = inode;
+        async->rw = rw;
+        async->bio = bio;
+        async->mirror_num = mirror_num;
+        async->submit_bio_hook = submit_bio_hook;
+        async->work.func = run_one_async_submit;
+        async->work.flags = 0;
+
+        while(atomic_read(&fs_info->async_submit_draining) &&
+              atomic_read(&fs_info->nr_async_submits)) {
+                wait_event(fs_info->async_submit_wait,
+                           (atomic_read(&fs_info->nr_async_submits) == 0));
+        }
+
+        atomic_inc(&fs_info->nr_async_submits);
+        btrfs_queue_worker(&fs_info->workers, &async->work);
+
+        if (atomic_read(&fs_info->nr_async_submits) > limit) {
+                wait_event_timeout(fs_info->async_submit_wait,
+                           (atomic_read(&fs_info->nr_async_submits) < limit),
+                           HZ/10);
+
+                wait_event_timeout(fs_info->async_submit_wait,
+                           (atomic_read(&fs_info->nr_async_bios) < limit),
+                           HZ/10);
+        }
+        return 0;
+}
+
+static int btree_csum_one_bio(struct bio *bio)
+{
+        struct bio_vec *bvec = bio->bi_io_vec;
+        int bio_index = 0;
+        struct btrfs_root *root;
+
+        WARN_ON(bio->bi_vcnt <= 0);
+        while(bio_index < bio->bi_vcnt) {
+                root = BTRFS_I(bvec->bv_page->mapping->host)->root;
+                csum_dirty_buffer(root, bvec->bv_page);
+                bio_index++;
+                bvec++;
+        }
+        return 0;
+}
+
+static int __btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
+                                 int mirror_num)
+{
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        int ret;
+
+        /*
+         * when we're called for a write, we're already in the async
+         * submission context.  Just jump into btrfs_map_bio
+         */
+        if (rw & (1 << BIO_RW)) {
+                btree_csum_one_bio(bio);
+                return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio,
+                                     mirror_num, 1);
+        }
+
+        /*
+         * called for a read, do the setup so that checksum validation
+         * can happen in the async kernel threads
+         */
+        ret = btrfs_bio_wq_end_io(root->fs_info, bio, 1);
+        BUG_ON(ret);
+
+        return btrfs_map_bio(BTRFS_I(inode)->root, rw, bio, mirror_num, 1);
+}
+
+static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio,
+                                 int mirror_num)
+{
+        /*
+         * kthread helpers are used to submit writes so that checksumming
+         * can happen in parallel across all CPUs
+         */
+        if (!(rw & (1 << BIO_RW))) {
+                return __btree_submit_bio_hook(inode, rw, bio, mirror_num);
+        }
+        return btrfs_wq_submit_bio(BTRFS_I(inode)->root->fs_info,
+                                   inode, rw, bio, mirror_num,
+                                   __btree_submit_bio_hook);
+}
+
+static int btree_writepage(struct page *page, struct writeback_control *wbc)
+{
+        struct extent_io_tree *tree;
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+
+        if (current->flags & PF_MEMALLOC) {
+                redirty_page_for_writepage(wbc, page);
+                unlock_page(page);
+                return 0;
+        }
+        return extent_write_full_page(tree, page, btree_get_extent, wbc);
+}
+
+static int btree_writepages(struct address_space *mapping,
+                            struct writeback_control *wbc)
+{
+        struct extent_io_tree *tree;
+        tree = &BTRFS_I(mapping->host)->io_tree;
+        if (wbc->sync_mode == WB_SYNC_NONE) {
+                u64 num_dirty;
+                u64 start = 0;
+                unsigned long thresh = 32 * 1024 * 1024;
+
+                if (wbc->for_kupdate)
+                        return 0;
+
+                num_dirty = count_range_bits(tree, &start, (u64)-1,
+                                             thresh, EXTENT_DIRTY);
+                if (num_dirty < thresh) {
+                        return 0;
+                }
+        }
+        return extent_writepages(tree, mapping, btree_get_extent, wbc);
+}
+
+int btree_readpage(struct file *file, struct page *page)
+{
+        struct extent_io_tree *tree;
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+        return extent_read_full_page(tree, page, btree_get_extent);
+}
+
+static int btree_releasepage(struct page *page, gfp_t gfp_flags)
+{
+        struct extent_io_tree *tree;
+        struct extent_map_tree *map;
+        int ret;
+
+        if (PageWriteback(page) || PageDirty(page))
+            return 0;
+
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+        map = &BTRFS_I(page->mapping->host)->extent_tree;
+
+        ret = try_release_extent_state(map, tree, page, gfp_flags);
+        if (!ret) {
+                return 0;
+        }
+
+        ret = try_release_extent_buffer(tree, page);
+        if (ret == 1) {
+                ClearPagePrivate(page);
+                set_page_private(page, 0);
+                page_cache_release(page);
+        }
+
+        return ret;
+}
+
+static void btree_invalidatepage(struct page *page, unsigned long offset)
+{
+        struct extent_io_tree *tree;
+        tree = &BTRFS_I(page->mapping->host)->io_tree;
+        extent_invalidatepage(tree, page, offset);
+        btree_releasepage(page, GFP_NOFS);
+        if (PagePrivate(page)) {
+                printk("warning page private not zero on page %Lu\n",
+                       page_offset(page));
+                ClearPagePrivate(page);
+                set_page_private(page, 0);
+                page_cache_release(page);
+        }
+}
+
+#if 0
+static int btree_writepage(struct page *page, struct writeback_control *wbc)
+{
+        struct buffer_head *bh;
+        struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
+        struct buffer_head *head;
+        if (!page_has_buffers(page)) {
+                create_empty_buffers(page, root->fs_info->sb->s_blocksize,
+                                        (1 << BH_Dirty)|(1 << BH_Uptodate));
+        }
+        head = page_buffers(page);
+        bh = head;
+        do {
+                if (buffer_dirty(bh))
+                        csum_tree_block(root, bh, 0);
+                bh = bh->b_this_page;
+        } while (bh != head);
+        return block_write_full_page(page, btree_get_block, wbc);
+}
+#endif
+
+static struct address_space_operations btree_aops = {
+        .readpage       = btree_readpage,
+        .writepage      = btree_writepage,
+        .writepages     = btree_writepages,
+        .releasepage    = btree_releasepage,
+        .invalidatepage = btree_invalidatepage,
+        .sync_page      = block_sync_page,
+};
+
+int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
+                         u64 parent_transid)
+{
+        struct extent_buffer *buf = NULL;
+        struct inode *btree_inode = root->fs_info->btree_inode;
+        int ret = 0;
+
+        buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
+        if (!buf)
+                return 0;
+        read_extent_buffer_pages(&BTRFS_I(btree_inode)->io_tree,
+                                 buf, 0, 0, btree_get_extent, 0);
+        free_extent_buffer(buf);
+        return ret;
+}
+
+struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root,
+                                            u64 bytenr, u32 blocksize)
+{
+        struct inode *btree_inode = root->fs_info->btree_inode;
+        struct extent_buffer *eb;
+        eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree,
+                                bytenr, blocksize, GFP_NOFS);
+        return eb;
+}
+
+struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
+                                                 u64 bytenr, u32 blocksize)
+{
+        struct inode *btree_inode = root->fs_info->btree_inode;
+        struct extent_buffer *eb;
+
+        eb = alloc_extent_buffer(&BTRFS_I(btree_inode)->io_tree,
+                                 bytenr, blocksize, NULL, GFP_NOFS);
+        return eb;
+}
+
+
+int btrfs_write_tree_block(struct extent_buffer *buf)
+{
+        return btrfs_fdatawrite_range(buf->first_page->mapping, buf->start,
+                                      buf->start + buf->len - 1, WB_SYNC_ALL);
+}
+
+int btrfs_wait_tree_block_writeback(struct extent_buffer *buf)
+{
+        return btrfs_wait_on_page_writeback_range(buf->first_page->mapping,
+                                  buf->start, buf->start + buf->len -1);
+}
+
+struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
+                                      u32 blocksize, u64 parent_transid)
+{
+        struct extent_buffer *buf = NULL;
+        struct inode *btree_inode = root->fs_info->btree_inode;
+        struct extent_io_tree *io_tree;
+        int ret;
+
+        io_tree = &BTRFS_I(btree_inode)->io_tree;
+
+        buf = btrfs_find_create_tree_block(root, bytenr, blocksize);
+        if (!buf)
+                return NULL;
+
+        ret = btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
+
+        if (ret == 0) {
+                buf->flags |= EXTENT_UPTODATE;
+        } else {
+                WARN_ON(1);
+        }
+        return buf;
+
+}
+
+int clean_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+                     struct extent_buffer *buf)
+{
+        struct inode *btree_inode = root->fs_info->btree_inode;
+        if (btrfs_header_generation(buf) ==
+            root->fs_info->running_transaction->transid) {
+                WARN_ON(!btrfs_tree_locked(buf));
+                clear_extent_buffer_dirty(&BTRFS_I(btree_inode)->io_tree,
+                                          buf);
+        }
+        return 0;
+}
+
+static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
+                        u32 stripesize, struct btrfs_root *root,
+                        struct btrfs_fs_info *fs_info,
+                        u64 objectid)
+{
+        root->node = NULL;
+        root->inode = NULL;
+        root->commit_root = NULL;
+        root->ref_tree = NULL;
+        root->sectorsize = sectorsize;
+        root->nodesize = nodesize;
+        root->leafsize = leafsize;
+        root->stripesize = stripesize;
+        root->ref_cows = 0;
+        root->track_dirty = 0;
+
+        root->fs_info = fs_info;
+        root->objectid = objectid;
+        root->last_trans = 0;
+        root->highest_inode = 0;
+        root->last_inode_alloc = 0;
+        root->name = NULL;
+        root->in_sysfs = 0;
+
+        INIT_LIST_HEAD(&root->dirty_list);
+        INIT_LIST_HEAD(&root->orphan_list);
+        INIT_LIST_HEAD(&root->dead_list);
+        spin_lock_init(&root->node_lock);
+        spin_lock_init(&root->list_lock);
+        mutex_init(&root->objectid_mutex);
+        mutex_init(&root->log_mutex);
+        extent_io_tree_init(&root->dirty_log_pages,
+                             fs_info->btree_inode->i_mapping, GFP_NOFS);
+
+        btrfs_leaf_ref_tree_init(&root->ref_tree_struct);
+        root->ref_tree = &root->ref_tree_struct;
+
+        memset(&root->root_key, 0, sizeof(root->root_key));
+        memset(&root->root_item, 0, sizeof(root->root_item));
+        memset(&root->defrag_progress, 0, sizeof(root->defrag_progress));
+        memset(&root->root_kobj, 0, sizeof(root->root_kobj));
+        root->defrag_trans_start = fs_info->generation;
+        init_completion(&root->kobj_unregister);
+        root->defrag_running = 0;
+        root->defrag_level = 0;
+        root->root_key.objectid = objectid;
+        return 0;
+}
+
+static int find_and_setup_root(struct btrfs_root *tree_root,
+                               struct btrfs_fs_info *fs_info,
+                               u64 objectid,
+                               struct btrfs_root *root)
+{
+        int ret;
+        u32 blocksize;
+
+        __setup_root(tree_root->nodesize, tree_root->leafsize,
+                     tree_root->sectorsize, tree_root->stripesize,
+                     root, fs_info, objectid);
+        ret = btrfs_find_last_root(tree_root, objectid,
+                                   &root->root_item, &root->root_key);
+        BUG_ON(ret);
+
+        blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
+        root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
+                                     blocksize, 0);
+        BUG_ON(!root->node);
+        return 0;
+}
+
+int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans,
+                             struct btrfs_fs_info *fs_info)
+{
+        struct extent_buffer *eb;
+        struct btrfs_root *log_root_tree = fs_info->log_root_tree;
+        u64 start = 0;
+        u64 end = 0;
+        int ret;
+
+        if (!log_root_tree)
+                return 0;
+
+        while(1) {
+                ret = find_first_extent_bit(&log_root_tree->dirty_log_pages,
+                                    0, &start, &end, EXTENT_DIRTY);
+                if (ret)
+                        break;
+
+                clear_extent_dirty(&log_root_tree->dirty_log_pages,
+                                   start, end, GFP_NOFS);
+        }
+        eb = fs_info->log_root_tree->node;
+
+        WARN_ON(btrfs_header_level(eb) != 0);
+        WARN_ON(btrfs_header_nritems(eb) != 0);
+
+        ret = btrfs_free_reserved_extent(fs_info->tree_root,
+                                eb->start, eb->len);
+        BUG_ON(ret);
+
+        free_extent_buffer(eb);
+        kfree(fs_info->log_root_tree);
+        fs_info->log_root_tree = NULL;
+        return 0;
+}
+
+int btrfs_init_log_root_tree(struct btrfs_trans_handle *trans,
+                             struct btrfs_fs_info *fs_info)
+{
+        struct btrfs_root *root;
+        struct btrfs_root *tree_root = fs_info->tree_root;
+
+        root = kzalloc(sizeof(*root), GFP_NOFS);
+        if (!root)
+                return -ENOMEM;
+
+        __setup_root(tree_root->nodesize, tree_root->leafsize,
+                     tree_root->sectorsize, tree_root->stripesize,
+                     root, fs_info, BTRFS_TREE_LOG_OBJECTID);
+
+        root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
+        root->root_key.type = BTRFS_ROOT_ITEM_KEY;
+        root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;
+        root->ref_cows = 0;
+
+        root->node = btrfs_alloc_free_block(trans, root, root->leafsize,
+                                            0, BTRFS_TREE_LOG_OBJECTID,
+                                            trans->transid, 0, 0, 0);
+
+        btrfs_set_header_nritems(root->node, 0);
+        btrfs_set_header_level(root->node, 0);
+        btrfs_set_header_bytenr(root->node, root->node->start);
+        btrfs_set_header_generation(root->node, trans->transid);
+        btrfs_set_header_owner(root->node, BTRFS_TREE_LOG_OBJECTID);
+
+        write_extent_buffer(root->node, root->fs_info->fsid,
+                            (unsigned long)btrfs_header_fsid(root->node),
+                            BTRFS_FSID_SIZE);
+        btrfs_mark_buffer_dirty(root->node);
+        btrfs_tree_unlock(root->node);
+        fs_info->log_root_tree = root;
+        return 0;
+}
+
+struct btrfs_root *btrfs_read_fs_root_no_radix(struct btrfs_root *tree_root,
+                                               struct btrfs_key *location)
+{
+        struct btrfs_root *root;
+        struct btrfs_fs_info *fs_info = tree_root->fs_info;
+        struct btrfs_path *path;
+        struct extent_buffer *l;
+        u64 highest_inode;
+        u32 blocksize;
+        int ret = 0;
+
+        root = kzalloc(sizeof(*root), GFP_NOFS);
+        if (!root)
+                return ERR_PTR(-ENOMEM);
+        if (location->offset == (u64)-1) {
+                ret = find_and_setup_root(tree_root, fs_info,
+                                          location->objectid, root);
+                if (ret) {
+                        kfree(root);
+                        return ERR_PTR(ret);
+                }
+                goto insert;
+        }
+
+        __setup_root(tree_root->nodesize, tree_root->leafsize,
+                     tree_root->sectorsize, tree_root->stripesize,
+                     root, fs_info, location->objectid);
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+        ret = btrfs_search_slot(NULL, tree_root, location, path, 0, 0);
+        if (ret != 0) {
+                if (ret > 0)
+                        ret = -ENOENT;
+                goto out;
+        }
+        l = path->nodes[0];
+        read_extent_buffer(l, &root->root_item,
+               btrfs_item_ptr_offset(l, path->slots[0]),
+               sizeof(root->root_item));
+        memcpy(&root->root_key, location, sizeof(*location));
+        ret = 0;
+out:
+        btrfs_release_path(root, path);
+        btrfs_free_path(path);
+        if (ret) {
+                kfree(root);
+                return ERR_PTR(ret);
+        }
+        blocksize = btrfs_level_size(root, btrfs_root_level(&root->root_item));
+        root->node = read_tree_block(root, btrfs_root_bytenr(&root->root_item),
+                                     blocksize, 0);
+        BUG_ON(!root->node);
+insert:
+        if (location->objectid != BTRFS_TREE_LOG_OBJECTID) {
+                root->ref_cows = 1;
+                ret = btrfs_find_highest_inode(root, &highest_inode);
+                if (ret == 0) {
+                        root->highest_inode = highest_inode;
+                        root->last_inode_alloc = highest_inode;
+                }
+        }
+        return root;
+}
+
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+                                        u64 root_objectid)
+{
+        struct btrfs_root *root;
+
+        if (root_objectid == BTRFS_ROOT_TREE_OBJECTID)
+                return fs_info->tree_root;
+        if (root_objectid == BTRFS_EXTENT_TREE_OBJECTID)
+                return fs_info->extent_root;
+
+        root = radix_tree_lookup(&fs_info->fs_roots_radix,
+                                 (unsigned long)root_objectid);
+        return root;
+}
+
+struct btrfs_root *btrfs_read_fs_root_no_name(struct btrfs_fs_info *fs_info,
+                                              struct btrfs_key *location)
+{
+        struct btrfs_root *root;
+        int ret;
+
+        if (location->objectid == BTRFS_ROOT_TREE_OBJECTID)
+                return fs_info->tree_root;
+        if (location->objectid == BTRFS_EXTENT_TREE_OBJECTID)
+                return fs_info->extent_root;
+        if (location->objectid == BTRFS_CHUNK_TREE_OBJECTID)
+                return fs_info->chunk_root;
+        if (location->objectid == BTRFS_DEV_TREE_OBJECTID)
+                return fs_info->dev_root;
+
+        root = radix_tree_lookup(&fs_info->fs_roots_radix,
+                                 (unsigned long)location->objectid);
+        if (root)
+                return root;
+
+        root = btrfs_read_fs_root_no_radix(fs_info->tree_root, location);
+        if (IS_ERR(root))
+                return root;
+        ret = radix_tree_insert(&fs_info->fs_roots_radix,
+                                (unsigned long)root->root_key.objectid,
+                                root);
+        if (ret) {
+                free_extent_buffer(root->node);
+                kfree(root);
+                return ERR_PTR(ret);
+        }
+        ret = btrfs_find_dead_roots(fs_info->tree_root,
+                                    root->root_key.objectid, root);
+        BUG_ON(ret);
+
+        return root;
+}
+
+struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
+                                      struct btrfs_key *location,
+                                      const char *name, int namelen)
+{
+        struct btrfs_root *root;
+        int ret;
+
+        root = btrfs_read_fs_root_no_name(fs_info, location);
+        if (!root)
+                return NULL;
+
+        if (root->in_sysfs)
+                return root;
+
+        ret = btrfs_set_root_name(root, name, namelen);
+        if (ret) {
+                free_extent_buffer(root->node);
+                kfree(root);
+                return ERR_PTR(ret);
+        }
+
+        ret = btrfs_sysfs_add_root(root);
+        if (ret) {
+                free_extent_buffer(root->node);
+                kfree(root->name);
+                kfree(root);
+                return ERR_PTR(ret);
+        }
+        root->in_sysfs = 1;
+        return root;
+}
+#if 0
+static int add_hasher(struct btrfs_fs_info *info, char *type) {
+        struct btrfs_hasher *hasher;
+
+        hasher = kmalloc(sizeof(*hasher), GFP_NOFS);
+        if (!hasher)
+                return -ENOMEM;
+        hasher->hash_tfm = crypto_alloc_hash(type, 0, CRYPTO_ALG_ASYNC);
+        if (!hasher->hash_tfm) {
+                kfree(hasher);
+                return -EINVAL;
+        }
+        spin_lock(&info->hash_lock);
+        list_add(&hasher->list, &info->hashers);
+        spin_unlock(&info->hash_lock);
+        return 0;
+}
+#endif
+
+static int btrfs_congested_fn(void *congested_data, int bdi_bits)
+{
+        struct btrfs_fs_info *info = (struct btrfs_fs_info *)congested_data;
+        int ret = 0;
+        struct list_head *cur;
+        struct btrfs_device *device;
+        struct backing_dev_info *bdi;
+
+        if ((bdi_bits & (1 << BDI_write_congested)) &&
+            btrfs_congested_async(info, 0))
+                return 1;
+
+        list_for_each(cur, &info->fs_devices->devices) {
+                device = list_entry(cur, struct btrfs_device, dev_list);
+                if (!device->bdev)
+                        continue;
+                bdi = blk_get_backing_dev_info(device->bdev);
+                if (bdi && bdi_congested(bdi, bdi_bits)) {
+                        ret = 1;
+                        break;
+                }
+        }
+        return ret;
+}
+
+/*
+ * this unplugs every device on the box, and it is only used when page
+ * is null
+ */
+static void __unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
+{
+        struct list_head *cur;
+        struct btrfs_device *device;
+        struct btrfs_fs_info *info;
+
+        info = (struct btrfs_fs_info *)bdi->unplug_io_data;
+        list_for_each(cur, &info->fs_devices->devices) {
+                device = list_entry(cur, struct btrfs_device, dev_list);
+                bdi = blk_get_backing_dev_info(device->bdev);
+                if (bdi->unplug_io_fn) {
+                        bdi->unplug_io_fn(bdi, page);
+                }
+        }
+}
+
+void btrfs_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
+{
+        struct inode *inode;
+        struct extent_map_tree *em_tree;
+        struct extent_map *em;
+        struct address_space *mapping;
+        u64 offset;
+
+        /* the generic O_DIRECT read code does this */
+        if (!page) {
+                __unplug_io_fn(bdi, page);
+                return;
+        }
+
+        /*
+         * page->mapping may change at any time.  Get a consistent copy
+         * and use that for everything below
+         */
+        smp_mb();
+        mapping = page->mapping;
+        if (!mapping)
+                return;
+
+        inode = mapping->host;
+        offset = page_offset(page);
+
+        em_tree = &BTRFS_I(inode)->extent_tree;
+        spin_lock(&em_tree->lock);
+        em = lookup_extent_mapping(em_tree, offset, PAGE_CACHE_SIZE);
+        spin_unlock(&em_tree->lock);
+        if (!em) {
+                __unplug_io_fn(bdi, page);
+                return;
+        }
+
+        if (em->block_start >= EXTENT_MAP_LAST_BYTE) {
+                free_extent_map(em);
+                __unplug_io_fn(bdi, page);
+                return;
+        }
+        offset = offset - em->start;
+        btrfs_unplug_page(&BTRFS_I(inode)->root->fs_info->mapping_tree,
+                          em->block_start + offset, page);
+        free_extent_map(em);
+}
+
+static int setup_bdi(struct btrfs_fs_info *info, struct backing_dev_info *bdi)
+{
+        bdi_init(bdi);
+        bdi->ra_pages   = default_backing_dev_info.ra_pages;
+        bdi->state              = 0;
+        bdi->capabilities       = default_backing_dev_info.capabilities;
+        bdi->unplug_io_fn       = btrfs_unplug_io_fn;
+        bdi->unplug_io_data     = info;
+        bdi->congested_fn       = btrfs_congested_fn;
+        bdi->congested_data     = info;
+        return 0;
+}
+
+static int bio_ready_for_csum(struct bio *bio)
+{
+        u64 length = 0;
+        u64 buf_len = 0;
+        u64 start = 0;
+        struct page *page;
+        struct extent_io_tree *io_tree = NULL;
+        struct btrfs_fs_info *info = NULL;
+        struct bio_vec *bvec;
+        int i;
+        int ret;
+
+        bio_for_each_segment(bvec, bio, i) {
+                page = bvec->bv_page;
+                if (page->private == EXTENT_PAGE_PRIVATE) {
+                        length += bvec->bv_len;
+                        continue;
+                }
+                if (!page->private) {
+                        length += bvec->bv_len;
+                        continue;
+                }
+                length = bvec->bv_len;
+                buf_len = page->private >> 2;
+                start = page_offset(page) + bvec->bv_offset;
+                io_tree = &BTRFS_I(page->mapping->host)->io_tree;
+                info = BTRFS_I(page->mapping->host)->root->fs_info;
+        }
+        /* are we fully contained in this bio? */
+        if (buf_len <= length)
+                return 1;
+
+        ret = extent_range_uptodate(io_tree, start + length,
+                                    start + buf_len - 1);
+        if (ret == 1)
+                return ret;
+        return ret;
+}
+
+/*
+ * called by the kthread helper functions to finally call the bio end_io
+ * functions.  This is where read checksum verification actually happens
+ */
+static void end_workqueue_fn(struct btrfs_work *work)
+{
+        struct bio *bio;
+        struct end_io_wq *end_io_wq;
+        struct btrfs_fs_info *fs_info;
+        int error;
+
+        end_io_wq = container_of(work, struct end_io_wq, work);
+        bio = end_io_wq->bio;
+        fs_info = end_io_wq->info;
+
+        /* metadata bios are special because the whole tree block must
+         * be checksummed at once.  This makes sure the entire block is in
+         * ram and up to date before trying to verify things.  For
+         * blocksize <= pagesize, it is basically a noop
+         */
+        if (end_io_wq->metadata && !bio_ready_for_csum(bio)) {
+                btrfs_queue_worker(&fs_info->endio_workers,
+                                   &end_io_wq->work);
+                return;
+        }
+        error = end_io_wq->error;
+        bio->bi_private = end_io_wq->private;
+        bio->bi_end_io = end_io_wq->end_io;
+        kfree(end_io_wq);
+        bio_endio(bio, error);
+}
+
+static int cleaner_kthread(void *arg)
+{
+        struct btrfs_root *root = arg;
+
+        do {
+                smp_mb();
+                if (root->fs_info->closing)
+                        break;
+
+                vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
+                mutex_lock(&root->fs_info->cleaner_mutex);
+                btrfs_clean_old_snapshots(root);
+                mutex_unlock(&root->fs_info->cleaner_mutex);
+
+                if (freezing(current)) {
+                        refrigerator();
+                } else {
+                        smp_mb();
+                        if (root->fs_info->closing)
+                                break;
+                        set_current_state(TASK_INTERRUPTIBLE);
+                        schedule();
+                        __set_current_state(TASK_RUNNING);
+                }
+        } while (!kthread_should_stop());
+        return 0;
+}
+
+static int transaction_kthread(void *arg)
+{
+        struct btrfs_root *root = arg;
+        struct btrfs_trans_handle *trans;
+        struct btrfs_transaction *cur;
+        unsigned long now;
+        unsigned long delay;
+        int ret;
+
+        do {
+                smp_mb();
+                if (root->fs_info->closing)
+                        break;
+
+                delay = HZ * 30;
+                vfs_check_frozen(root->fs_info->sb, SB_FREEZE_WRITE);
+                mutex_lock(&root->fs_info->transaction_kthread_mutex);
+
+                if (root->fs_info->total_ref_cache_size > 20 * 1024 * 1024) {
+                        printk("btrfs: total reference cache size %Lu\n",
+                                root->fs_info->total_ref_cache_size);
+                }
+
+                mutex_lock(&root->fs_info->trans_mutex);
+                cur = root->fs_info->running_transaction;
+                if (!cur) {
+                        mutex_unlock(&root->fs_info->trans_mutex);
+                        goto sleep;
+                }
+
+                now = get_seconds();
+                if (now < cur->start_time || now - cur->start_time < 30) {
+                        mutex_unlock(&root->fs_info->trans_mutex);
+                        delay = HZ * 5;
+                        goto sleep;
+                }
+                mutex_unlock(&root->fs_info->trans_mutex);
+                trans = btrfs_start_transaction(root, 1);
+                ret = btrfs_commit_transaction(trans, root);
+sleep:
+                wake_up_process(root->fs_info->cleaner_kthread);
+                mutex_unlock(&root->fs_info->transaction_kthread_mutex);
+
+                if (freezing(current)) {
+                        refrigerator();
+                } else {
+                        if (root->fs_info->closing)
+                                break;
+                        set_current_state(TASK_INTERRUPTIBLE);
+                        schedule_timeout(delay);
+                        __set_current_state(TASK_RUNNING);
+                }
+        } while (!kthread_should_stop());
+        return 0;
+}
+
+struct btrfs_root *open_ctree(struct super_block *sb,
+                              struct btrfs_fs_devices *fs_devices,
+                              char *options)
+{
+        u32 sectorsize;
+        u32 nodesize;
+        u32 leafsize;
+        u32 blocksize;
+        u32 stripesize;
+        struct buffer_head *bh;
+        struct btrfs_root *extent_root = kzalloc(sizeof(struct btrfs_root),
+                                                 GFP_NOFS);
+        struct btrfs_root *tree_root = kzalloc(sizeof(struct btrfs_root),
+                                               GFP_NOFS);
+        struct btrfs_fs_info *fs_info = kzalloc(sizeof(*fs_info),
+                                                GFP_NOFS);
+        struct btrfs_root *chunk_root = kzalloc(sizeof(struct btrfs_root),
+                                                GFP_NOFS);
+        struct btrfs_root *dev_root = kzalloc(sizeof(struct btrfs_root),
+                                              GFP_NOFS);
+        struct btrfs_root *log_tree_root;
+
+        int ret;
+        int err = -EINVAL;
+
+        struct btrfs_super_block *disk_super;
+
+        if (!extent_root || !tree_root || !fs_info ||
+            !chunk_root || !dev_root) {
+                err = -ENOMEM;
+                goto fail;
+        }
+        INIT_RADIX_TREE(&fs_info->fs_roots_radix, GFP_NOFS);
+        INIT_LIST_HEAD(&fs_info->trans_list);
+        INIT_LIST_HEAD(&fs_info->dead_roots);
+        INIT_LIST_HEAD(&fs_info->hashers);
+        INIT_LIST_HEAD(&fs_info->delalloc_inodes);
+        spin_lock_init(&fs_info->hash_lock);
+        spin_lock_init(&fs_info->delalloc_lock);
+        spin_lock_init(&fs_info->new_trans_lock);
+        spin_lock_init(&fs_info->ref_cache_lock);
+
+        init_completion(&fs_info->kobj_unregister);
+        fs_info->tree_root = tree_root;
+        fs_info->extent_root = extent_root;
+        fs_info->chunk_root = chunk_root;
+        fs_info->dev_root = dev_root;
+        fs_info->fs_devices = fs_devices;
+        INIT_LIST_HEAD(&fs_info->dirty_cowonly_roots);
+        INIT_LIST_HEAD(&fs_info->space_info);
+        btrfs_mapping_init(&fs_info->mapping_tree);
+        atomic_set(&fs_info->nr_async_submits, 0);
+        atomic_set(&fs_info->async_submit_draining, 0);
+        atomic_set(&fs_info->nr_async_bios, 0);
+        atomic_set(&fs_info->throttles, 0);
+        atomic_set(&fs_info->throttle_gen, 0);
+        fs_info->sb = sb;
+        fs_info->max_extent = (u64)-1;
+        fs_info->max_inline = 8192 * 1024;
+        setup_bdi(fs_info, &fs_info->bdi);
+        fs_info->btree_inode = new_inode(sb);
+        fs_info->btree_inode->i_ino = 1;
+        fs_info->btree_inode->i_nlink = 1;
+        fs_info->thread_pool_size = min(num_online_cpus() + 2, 8);
+
+        INIT_LIST_HEAD(&fs_info->ordered_extents);
+        spin_lock_init(&fs_info->ordered_extent_lock);
+
+        sb->s_blocksize = 4096;
+        sb->s_blocksize_bits = blksize_bits(4096);
+
+        /*
+         * we set the i_size on the btree inode to the max possible int.
+         * the real end of the address space is determined by all of
+         * the devices in the system
+         */
+        fs_info->btree_inode->i_size = OFFSET_MAX;
+        fs_info->btree_inode->i_mapping->a_ops = &btree_aops;
+        fs_info->btree_inode->i_mapping->backing_dev_info = &fs_info->bdi;
+
+        extent_io_tree_init(&BTRFS_I(fs_info->btree_inode)->io_tree,
+                             fs_info->btree_inode->i_mapping,
+                             GFP_NOFS);
+        extent_map_tree_init(&BTRFS_I(fs_info->btree_inode)->extent_tree,
+                             GFP_NOFS);
+
+        BTRFS_I(fs_info->btree_inode)->io_tree.ops = &btree_extent_io_ops;
+
+        spin_lock_init(&fs_info->block_group_cache_lock);
+        fs_info->block_group_cache_tree.rb_node = NULL;
+
+        extent_io_tree_init(&fs_info->pinned_extents,
+                             fs_info->btree_inode->i_mapping, GFP_NOFS);
+        extent_io_tree_init(&fs_info->pending_del,
+                             fs_info->btree_inode->i_mapping, GFP_NOFS);
+        extent_io_tree_init(&fs_info->extent_ins,
+                             fs_info->btree_inode->i_mapping, GFP_NOFS);
+        fs_info->do_barriers = 1;
+
+        extent_io_tree_init(&fs_info->reloc_mapping_tree,
+                            fs_info->btree_inode->i_mapping, GFP_NOFS);
+        INIT_LIST_HEAD(&fs_info->dead_reloc_roots);
+        btrfs_leaf_ref_tree_init(&fs_info->reloc_ref_tree);
+        btrfs_leaf_ref_tree_init(&fs_info->shared_ref_tree);
+
+        BTRFS_I(fs_info->btree_inode)->root = tree_root;
+        memset(&BTRFS_I(fs_info->btree_inode)->location, 0,
+               sizeof(struct btrfs_key));
+        insert_inode_hash(fs_info->btree_inode);
+
+        mutex_init(&fs_info->trans_mutex);
+        mutex_init(&fs_info->tree_log_mutex);
+        mutex_init(&fs_info->drop_mutex);
+        mutex_init(&fs_info->alloc_mutex);
+        mutex_init(&fs_info->chunk_mutex);
+        mutex_init(&fs_info->transaction_kthread_mutex);
+        mutex_init(&fs_info->cleaner_mutex);
+        mutex_init(&fs_info->volume_mutex);
+        mutex_init(&fs_info->tree_reloc_mutex);
+        init_waitqueue_head(&fs_info->transaction_throttle);
+        init_waitqueue_head(&fs_info->transaction_wait);
+        init_waitqueue_head(&fs_info->async_submit_wait);
+        init_waitqueue_head(&fs_info->tree_log_wait);
+        atomic_set(&fs_info->tree_log_commit, 0);
+        atomic_set(&fs_info->tree_log_writers, 0);
+        fs_info->tree_log_transid = 0;
+
+#if 0
+        ret = add_hasher(fs_info, "crc32c");
+        if (ret) {
+                printk("btrfs: failed hash setup, modprobe cryptomgr?\n");
+                err = -ENOMEM;
+                goto fail_iput;
+        }
+#endif
+        __setup_root(4096, 4096, 4096, 4096, tree_root,
+                     fs_info, BTRFS_ROOT_TREE_OBJECTID);
+
+
+        bh = __bread(fs_devices->latest_bdev,
+                     BTRFS_SUPER_INFO_OFFSET / 4096, 4096);
+        if (!bh)
+                goto fail_iput;
+
+        memcpy(&fs_info->super_copy, bh->b_data, sizeof(fs_info->super_copy));
+        brelse(bh);
+
+        memcpy(fs_info->fsid, fs_info->super_copy.fsid, BTRFS_FSID_SIZE);
+
+        disk_super = &fs_info->super_copy;
+        if (!btrfs_super_root(disk_super))
+                goto fail_sb_buffer;
+
+        err = btrfs_parse_options(tree_root, options);
+        if (err)
+                goto fail_sb_buffer;
+
+        /*
+         * we need to start all the end_io workers up front because the
+         * queue work function gets called at interrupt time, and so it
+         * cannot dynamically grow.
+         */
+        btrfs_init_workers(&fs_info->workers, "worker",
+                           fs_info->thread_pool_size);
+        btrfs_init_workers(&fs_info->submit_workers, "submit",
+                           min_t(u64, fs_devices->num_devices,
+                           fs_info->thread_pool_size));
+
+        /* a higher idle thresh on the submit workers makes it much more
+         * likely that bios will be send down in a sane order to the
+         * devices
+         */
+        fs_info->submit_workers.idle_thresh = 64;
+
+        /* fs_info->workers is responsible for checksumming file data
+         * blocks and metadata.  Using a larger idle thresh allows each
+         * worker thread to operate on things in roughly the order they
+         * were sent by the writeback daemons, improving overall locality
+         * of the IO going down the pipe.
+         */
+        fs_info->workers.idle_thresh = 128;
+
+        btrfs_init_workers(&fs_info->fixup_workers, "fixup", 1);
+        btrfs_init_workers(&fs_info->endio_workers, "endio",
+                           fs_info->thread_pool_size);
+        btrfs_init_workers(&fs_info->endio_write_workers, "endio-write",
+                           fs_info->thread_pool_size);
+
+        /*
+         * endios are largely parallel and should have a very
+         * low idle thresh
+         */
+        fs_info->endio_workers.idle_thresh = 4;
+        fs_info->endio_write_workers.idle_thresh = 64;
+
+        btrfs_start_workers(&fs_info->workers, 1);
+        btrfs_start_workers(&fs_info->submit_workers, 1);
+        btrfs_start_workers(&fs_info->fixup_workers, 1);
+        btrfs_start_workers(&fs_info->endio_workers, fs_info->thread_pool_size);
+        btrfs_start_workers(&fs_info->endio_write_workers,
+                            fs_info->thread_pool_size);
+
+        err = -EINVAL;
+        if (btrfs_super_num_devices(disk_super) > fs_devices->open_devices) {
+                printk("Btrfs: wanted %llu devices, but found %llu\n",
+                       (unsigned long long)btrfs_super_num_devices(disk_super),
+                       (unsigned long long)fs_devices->open_devices);
+                if (btrfs_test_opt(tree_root, DEGRADED))
+                        printk("continuing in degraded mode\n");
+                else {
+                        goto fail_sb_buffer;
+                }
+        }
+
+        fs_info->bdi.ra_pages *= btrfs_super_num_devices(disk_super);
+
+        nodesize = btrfs_super_nodesize(disk_super);
+        leafsize = btrfs_super_leafsize(disk_super);
+        sectorsize = btrfs_super_sectorsize(disk_super);
+        stripesize = btrfs_super_stripesize(disk_super);
+        tree_root->nodesize = nodesize;
+        tree_root->leafsize = leafsize;
+        tree_root->sectorsize = sectorsize;
+        tree_root->stripesize = stripesize;
+
+        sb->s_blocksize = sectorsize;
+        sb->s_blocksize_bits = blksize_bits(sectorsize);
+
+        if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
+                    sizeof(disk_super->magic))) {
+                printk("btrfs: valid FS not found on %s\n", sb->s_id);
+                goto fail_sb_buffer;
+        }
+
+        mutex_lock(&fs_info->chunk_mutex);
+        ret = btrfs_read_sys_array(tree_root);
+        mutex_unlock(&fs_info->chunk_mutex);
+        if (ret) {
+                printk("btrfs: failed to read the system array on %s\n",
+                       sb->s_id);
+                goto fail_sys_array;
+        }
+
+        blocksize = btrfs_level_size(tree_root,
+                                     btrfs_super_chunk_root_level(disk_super));
+
+        __setup_root(nodesize, leafsize, sectorsize, stripesize,
+                     chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);
+
+        chunk_root->node = read_tree_block(chunk_root,
+                                           btrfs_super_chunk_root(disk_super),
+                                           blocksize, 0);
+        BUG_ON(!chunk_root->node);
+
+        read_extent_buffer(chunk_root->node, fs_info->chunk_tree_uuid,
+                 (unsigned long)btrfs_header_chunk_tree_uuid(chunk_root->node),
+                 BTRFS_UUID_SIZE);
+
+        mutex_lock(&fs_info->chunk_mutex);
+        ret = btrfs_read_chunk_tree(chunk_root);
+        mutex_unlock(&fs_info->chunk_mutex);
+        BUG_ON(ret);
+
+        btrfs_close_extra_devices(fs_devices);
+
+        blocksize = btrfs_level_size(tree_root,
+                                     btrfs_super_root_level(disk_super));
+
+
+        tree_root->node = read_tree_block(tree_root,
+                                          btrfs_super_root(disk_super),
+                                          blocksize, 0);
+        if (!tree_root->node)
+                goto fail_sb_buffer;
+
+
+        ret = find_and_setup_root(tree_root, fs_info,
+                                  BTRFS_EXTENT_TREE_OBJECTID, extent_root);
+        if (ret)
+                goto fail_tree_root;
+        extent_root->track_dirty = 1;
+
+        ret = find_and_setup_root(tree_root, fs_info,
+                                  BTRFS_DEV_TREE_OBJECTID, dev_root);
+        dev_root->track_dirty = 1;
+
+        if (ret)
+                goto fail_extent_root;
+
+        btrfs_read_block_groups(extent_root);
+
+        fs_info->generation = btrfs_super_generation(disk_super) + 1;
+        fs_info->data_alloc_profile = (u64)-1;
+        fs_info->metadata_alloc_profile = (u64)-1;
+        fs_info->system_alloc_profile = fs_info->metadata_alloc_profile;
+        fs_info->cleaner_kthread = kthread_run(cleaner_kthread, tree_root,
+                                               "btrfs-cleaner");
+        if (!fs_info->cleaner_kthread)
+                goto fail_extent_root;
+
+        fs_info->transaction_kthread = kthread_run(transaction_kthread,
+                                                   tree_root,
+                                                   "btrfs-transaction");
+        if (!fs_info->transaction_kthread)
+                goto fail_cleaner;
+
+        if (btrfs_super_log_root(disk_super) != 0) {
+                u32 blocksize;
+                u64 bytenr = btrfs_super_log_root(disk_super);
+
+                blocksize =
+                     btrfs_level_size(tree_root,
+                                      btrfs_super_log_root_level(disk_super));
+
+                log_tree_root = kzalloc(sizeof(struct btrfs_root),
+                                                      GFP_NOFS);
+
+                __setup_root(nodesize, leafsize, sectorsize, stripesize,
+                             log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);
+
+                log_tree_root->node = read_tree_block(tree_root, bytenr,
+                                                      blocksize, 0);
+                ret = btrfs_recover_log_trees(log_tree_root);
+                BUG_ON(ret);
+        }
+
+        ret = btrfs_cleanup_reloc_trees(tree_root);
+        BUG_ON(ret);
+
+        fs_info->last_trans_committed = btrfs_super_generation(disk_super);
+        return tree_root;
+
+fail_cleaner:
+        kthread_stop(fs_info->cleaner_kthread);
+fail_extent_root:
+        free_extent_buffer(extent_root->node);
+fail_tree_root:
+        free_extent_buffer(tree_root->node);
+fail_sys_array:
+fail_sb_buffer:
+        btrfs_stop_workers(&fs_info->fixup_workers);
+        btrfs_stop_workers(&fs_info->workers);
+        btrfs_stop_workers(&fs_info->endio_workers);
+        btrfs_stop_workers(&fs_info->endio_write_workers);
+        btrfs_stop_workers(&fs_info->submit_workers);
+fail_iput:
+        iput(fs_info->btree_inode);
+fail:
+        btrfs_close_devices(fs_info->fs_devices);
+        btrfs_mapping_tree_free(&fs_info->mapping_tree);
+
+        kfree(extent_root);
+        kfree(tree_root);
+        bdi_destroy(&fs_info->bdi);
+        kfree(fs_info);
+        kfree(chunk_root);
+        kfree(dev_root);
+        return ERR_PTR(err);
+}
+
+static void btrfs_end_buffer_write_sync(struct buffer_head *bh, int uptodate)
+{
+        char b[BDEVNAME_SIZE];
+
+        if (uptodate) {
+                set_buffer_uptodate(bh);
+        } else {
+                if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
+                        printk(KERN_WARNING "lost page write due to "
+                                        "I/O error on %s\n",
+                                       bdevname(bh->b_bdev, b));
+                }
+                /* note, we dont' set_buffer_write_io_error because we have
+                 * our own ways of dealing with the IO errors
+                 */
+                clear_buffer_uptodate(bh);
+        }
+        unlock_buffer(bh);
+        put_bh(bh);
+}
+
+int write_all_supers(struct btrfs_root *root)
+{
+        struct list_head *cur;
+        struct list_head *head = &root->fs_info->fs_devices->devices;
+        struct btrfs_device *dev;
+        struct btrfs_super_block *sb;
+        struct btrfs_dev_item *dev_item;
+        struct buffer_head *bh;
+        int ret;
+        int do_barriers;
+        int max_errors;
+        int total_errors = 0;
+        u32 crc;
+        u64 flags;
+
+        max_errors = btrfs_super_num_devices(&root->fs_info->super_copy) - 1;
+        do_barriers = !btrfs_test_opt(root, NOBARRIER);
+
+        sb = &root->fs_info->super_for_commit;
+        dev_item = &sb->dev_item;
+        list_for_each(cur, head) {
+                dev = list_entry(cur, struct btrfs_device, dev_list);
+                if (!dev->bdev) {
+                        total_errors++;
+                        continue;
+                }
+                if (!dev->in_fs_metadata)
+                        continue;
+
+                btrfs_set_stack_device_type(dev_item, dev->type);
+                btrfs_set_stack_device_id(dev_item, dev->devid);
+                btrfs_set_stack_device_total_bytes(dev_item, dev->total_bytes);
+                btrfs_set_stack_device_bytes_used(dev_item, dev->bytes_used);
+                btrfs_set_stack_device_io_align(dev_item, dev->io_align);
+                btrfs_set_stack_device_io_width(dev_item, dev->io_width);
+                btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
+                memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
+                flags = btrfs_super_flags(sb);
+                btrfs_set_super_flags(sb, flags | BTRFS_HEADER_FLAG_WRITTEN);
+
+
+                crc = ~(u32)0;
+                crc = btrfs_csum_data(root, (char *)sb + BTRFS_CSUM_SIZE, crc,
+                                      BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE);
+                btrfs_csum_final(crc, sb->csum);
+
+                bh = __getblk(dev->bdev, BTRFS_SUPER_INFO_OFFSET / 4096,
+                              BTRFS_SUPER_INFO_SIZE);
+
+                memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);
+                dev->pending_io = bh;
+
+                get_bh(bh);
+                set_buffer_uptodate(bh);
+                lock_buffer(bh);
+                bh->b_end_io = btrfs_end_buffer_write_sync;
+
+                if (do_barriers && dev->barriers) {
+                        ret = submit_bh(WRITE_BARRIER, bh);
+                        if (ret == -EOPNOTSUPP) {
+                                printk("btrfs: disabling barriers on dev %s\n",
+                                       dev->name);
+                                set_buffer_uptodate(bh);
+                                dev->barriers = 0;
+                                get_bh(bh);
+                                lock_buffer(bh);
+                                ret = submit_bh(WRITE, bh);
+                        }
+                } else {
+                        ret = submit_bh(WRITE, bh);
+                }
+                if (ret)
+                        total_errors++;
+        }
+        if (total_errors > max_errors) {
+                printk("btrfs: %d errors while writing supers\n", total_errors);
+                BUG();
+        }
+        total_errors = 0;
+
+        list_for_each(cur, head) {
+                dev = list_entry(cur, struct btrfs_device, dev_list);
+                if (!dev->bdev)
+                        continue;
+                if (!dev->in_fs_metadata)
+                        continue;
+
+                BUG_ON(!dev->pending_io);
+                bh = dev->pending_io;
+                wait_on_buffer(bh);
+                if (!buffer_uptodate(dev->pending_io)) {
+                        if (do_barriers && dev->barriers) {
+                                printk("btrfs: disabling barriers on dev %s\n",
+                                       dev->name);
+                                set_buffer_uptodate(bh);
+                                get_bh(bh);
+                                lock_buffer(bh);
+                                dev->barriers = 0;
+                                ret = submit_bh(WRITE, bh);
+                                BUG_ON(ret);
+                                wait_on_buffer(bh);
+                                if (!buffer_uptodate(bh))
+                                        total_errors++;
+                        } else {
+                                total_errors++;
+                        }
+
+                }
+                dev->pending_io = NULL;
+                brelse(bh);
+        }
+        if (total_errors > max_errors) {
+                printk("btrfs: %d errors while writing supers\n", total_errors);
+                BUG();
+        }
+        return 0;
+}
+
+int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root
+                      *root)
+{
+        int ret;
+
+        ret = write_all_supers(root);
+        return ret;
+}
+
+int btrfs_free_fs_root(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
+{
+        radix_tree_delete(&fs_info->fs_roots_radix,
+                          (unsigned long)root->root_key.objectid);
+        if (root->in_sysfs)
+                btrfs_sysfs_del_root(root);
+        if (root->inode)
+                iput(root->inode);
+        if (root->node)
+                free_extent_buffer(root->node);
+        if (root->commit_root)
+                free_extent_buffer(root->commit_root);
+        if (root->name)
+                kfree(root->name);
+        kfree(root);
+        return 0;
+}
+
+static int del_fs_roots(struct btrfs_fs_info *fs_info)
+{
+        int ret;
+        struct btrfs_root *gang[8];
+        int i;
+
+        while(1) {
+                ret = radix_tree_gang_lookup(&fs_info->fs_roots_radix,
+                                             (void **)gang, 0,
+                                             ARRAY_SIZE(gang));
+                if (!ret)
+                        break;
+                for (i = 0; i < ret; i++)
+                        btrfs_free_fs_root(fs_info, gang[i]);
+        }
+        return 0;
+}
+
+int close_ctree(struct btrfs_root *root)
+{
+        int ret;
+        struct btrfs_trans_handle *trans;
+        struct btrfs_fs_info *fs_info = root->fs_info;
+
+        fs_info->closing = 1;
+        smp_mb();
+
+        kthread_stop(root->fs_info->transaction_kthread);
+        kthread_stop(root->fs_info->cleaner_kthread);
+
+        btrfs_clean_old_snapshots(root);
+        trans = btrfs_start_transaction(root, 1);
+        ret = btrfs_commit_transaction(trans, root);
+        /* run commit again to  drop the original snapshot */
+        trans = btrfs_start_transaction(root, 1);
+        btrfs_commit_transaction(trans, root);
+        ret = btrfs_write_and_wait_transaction(NULL, root);
+        BUG_ON(ret);
+
+        write_ctree_super(NULL, root);
+
+        if (fs_info->delalloc_bytes) {
+                printk("btrfs: at unmount delalloc count %Lu\n",
+                       fs_info->delalloc_bytes);
+        }
+        if (fs_info->total_ref_cache_size) {
+                printk("btrfs: at umount reference cache size %Lu\n",
+                        fs_info->total_ref_cache_size);
+        }
+
+        if (fs_info->extent_root->node)
+                free_extent_buffer(fs_info->extent_root->node);
+
+        if (fs_info->tree_root->node)
+                free_extent_buffer(fs_info->tree_root->node);
+
+        if (root->fs_info->chunk_root->node);
+                free_extent_buffer(root->fs_info->chunk_root->node);
+
+        if (root->fs_info->dev_root->node);
+                free_extent_buffer(root->fs_info->dev_root->node);
+
+        btrfs_free_block_groups(root->fs_info);
+        fs_info->closing = 2;
+        del_fs_roots(fs_info);
+
+        filemap_write_and_wait(fs_info->btree_inode->i_mapping);
+
+        truncate_inode_pages(fs_info->btree_inode->i_mapping, 0);
+
+        btrfs_stop_workers(&fs_info->fixup_workers);
+        btrfs_stop_workers(&fs_info->workers);
+        btrfs_stop_workers(&fs_info->endio_workers);
+        btrfs_stop_workers(&fs_info->endio_write_workers);
+        btrfs_stop_workers(&fs_info->submit_workers);
+
+        iput(fs_info->btree_inode);
+#if 0
+        while(!list_empty(&fs_info->hashers)) {
+                struct btrfs_hasher *hasher;
+                hasher = list_entry(fs_info->hashers.next, struct btrfs_hasher,
+                                    hashers);
+                list_del(&hasher->hashers);
+                crypto_free_hash(&fs_info->hash_tfm);
+                kfree(hasher);
+        }
+#endif
+        btrfs_close_devices(fs_info->fs_devices);
+        btrfs_mapping_tree_free(&fs_info->mapping_tree);
+
+        bdi_destroy(&fs_info->bdi);
+
+        kfree(fs_info->extent_root);
+        kfree(fs_info->tree_root);
+        kfree(fs_info->chunk_root);
+        kfree(fs_info->dev_root);
+        return 0;
+}
+
+int btrfs_buffer_uptodate(struct extent_buffer *buf, u64 parent_transid)
+{
+        int ret;
+        struct inode *btree_inode = buf->first_page->mapping->host;
+
+        ret = extent_buffer_uptodate(&BTRFS_I(btree_inode)->io_tree, buf);
+        if (!ret)
+                return ret;
+
+        ret = verify_parent_transid(&BTRFS_I(btree_inode)->io_tree, buf,
+                                    parent_transid);
+        return !ret;
+}
+
+int btrfs_set_buffer_uptodate(struct extent_buffer *buf)
+{
+        struct inode *btree_inode = buf->first_page->mapping->host;
+        return set_extent_buffer_uptodate(&BTRFS_I(btree_inode)->io_tree,
+                                          buf);
+}
+
+void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
+{
+        struct btrfs_root *root = BTRFS_I(buf->first_page->mapping->host)->root;
+        u64 transid = btrfs_header_generation(buf);
+        struct inode *btree_inode = root->fs_info->btree_inode;
+
+        WARN_ON(!btrfs_tree_locked(buf));
+        if (transid != root->fs_info->generation) {
+                printk(KERN_CRIT "transid mismatch buffer %llu, found %Lu running %Lu\n",
+                        (unsigned long long)buf->start,
+                        transid, root->fs_info->generation);
+                WARN_ON(1);
+        }
+        set_extent_buffer_dirty(&BTRFS_I(btree_inode)->io_tree, buf);
+}
+
+void btrfs_btree_balance_dirty(struct btrfs_root *root, unsigned long nr)
+{
+        /*
+         * looks as though older kernels can get into trouble with
+         * this code, they end up stuck in balance_dirty_pages forever
+         */
+        struct extent_io_tree *tree;
+        u64 num_dirty;
+        u64 start = 0;
+        unsigned long thresh = 96 * 1024 * 1024;
+        tree = &BTRFS_I(root->fs_info->btree_inode)->io_tree;
+
+        if (current_is_pdflush() || current->flags & PF_MEMALLOC)
+                return;
+
+        num_dirty = count_range_bits(tree, &start, (u64)-1,
+                                     thresh, EXTENT_DIRTY);
+        if (num_dirty > thresh) {
+                balance_dirty_pages_ratelimited_nr(
+                                   root->fs_info->btree_inode->i_mapping, 1);
+        }
+        return;
+}
+
+int btrfs_read_buffer(struct extent_buffer *buf, u64 parent_transid)
+{
+        struct btrfs_root *root = BTRFS_I(buf->first_page->mapping->host)->root;
+        int ret;
+        ret = btree_read_extent_buffer_pages(root, buf, 0, parent_transid);
+        if (ret == 0) {
+                buf->flags |= EXTENT_UPTODATE;
+        }
+        return ret;
+}
+
+int btree_lock_page_hook(struct page *page)
+{
+        struct inode *inode = page->mapping->host;
+        struct btrfs_root *root = BTRFS_I(inode)->root;
+        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+        struct extent_buffer *eb;
+        unsigned long len;
+        u64 bytenr = page_offset(page);
+
+        if (page->private == EXTENT_PAGE_PRIVATE)
+                goto out;
+
+        len = page->private >> 2;
+        eb = find_extent_buffer(io_tree, bytenr, len, GFP_NOFS);
+        if (!eb)
+                goto out;
+
+        btrfs_tree_lock(eb);
+        spin_lock(&root->fs_info->hash_lock);
+        btrfs_set_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN);
+        spin_unlock(&root->fs_info->hash_lock);
+        btrfs_tree_unlock(eb);
+        free_extent_buffer(eb);
+out:
+        lock_page(page);
+        return 0;
+}
+
+static struct extent_io_ops btree_extent_io_ops = {
+        .write_cache_pages_lock_hook = btree_lock_page_hook,
+        .readpage_end_io_hook = btree_readpage_end_io_hook,
+        .submit_bio_hook = btree_submit_bio_hook,
+        /* note we're sharing with inode.c for the merge bio hook */
+        .merge_bio_hook = btrfs_merge_bio_hook,
+};