ordered-data.c

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/*
 * 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/slab.h>
#include <linux/blkdev.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include "ctree.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "extent_io.h"

static struct kmem_cache *btrfs_ordered_extent_cache;

static u64 entry_end(struct btrfs_ordered_extent *entry)
{
    if (entry->file_offset + entry->len < entry->file_offset)
        return (u64)-1;
    return entry->file_offset + entry->len;
}

/* returns NULL if the insertion worked, or it returns the node it did find
 * in the tree
 */
static struct rb_node *tree_insert(struct rb_root *root, u64 file_offset,
                   struct rb_node *node)
{
    struct rb_node **p = &root->rb_node;
    struct rb_node *parent = NULL;
    struct btrfs_ordered_extent *entry;

    while (*p) {
        parent = *p;
        entry = rb_entry(parent, struct btrfs_ordered_extent, rb_node);

        if (file_offset < entry->file_offset)
            p = &(*p)->rb_left;
        else if (file_offset >= entry_end(entry))
            p = &(*p)->rb_right;
        else
            return parent;
    }

    rb_link_node(node, parent, p);
    rb_insert_color(node, root);
    return NULL;
}

static void ordered_data_tree_panic(struct inode *inode, int errno,
                           u64 offset)
{
    struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
    btrfs_panic(fs_info, errno, "Inconsistency in ordered tree at offset "
            "%llu\n", (unsigned long long)offset);
}

/*
 * look for a given offset in the tree, and if it can't be found return the
 * first lesser offset
 */
static struct rb_node *__tree_search(struct rb_root *root, u64 file_offset,
                     struct rb_node **prev_ret)
{
    struct rb_node *n = root->rb_node;
    struct rb_node *prev = NULL;
    struct rb_node *test;
    struct btrfs_ordered_extent *entry;
    struct btrfs_ordered_extent *prev_entry = NULL;

    while (n) {
        entry = rb_entry(n, struct btrfs_ordered_extent, rb_node);
        prev = n;
        prev_entry = entry;

        if (file_offset < entry->file_offset)
            n = n->rb_left;
        else if (file_offset >= entry_end(entry))
            n = n->rb_right;
        else
            return n;
    }
    if (!prev_ret)
        return NULL;

    while (prev && file_offset >= entry_end(prev_entry)) {
        test = rb_next(prev);
        if (!test)
            break;
        prev_entry = rb_entry(test, struct btrfs_ordered_extent,
                      rb_node);
        if (file_offset < entry_end(prev_entry))
            break;

        prev = test;
    }
    if (prev)
        prev_entry = rb_entry(prev, struct btrfs_ordered_extent,
                      rb_node);
    while (prev && file_offset < entry_end(prev_entry)) {
        test = rb_prev(prev);
        if (!test)
            break;
        prev_entry = rb_entry(test, struct btrfs_ordered_extent,
                      rb_node);
        prev = test;
    }
    *prev_ret = prev;
    return NULL;
}

/*
 * helper to check if a given offset is inside a given entry
 */
static int offset_in_entry(struct btrfs_ordered_extent *entry, u64 file_offset)
{
    if (file_offset < entry->file_offset ||
        entry->file_offset + entry->len <= file_offset)
        return 0;
    return 1;
}

static int range_overlaps(struct btrfs_ordered_extent *entry, u64 file_offset,
              u64 len)
{
    if (file_offset + len <= entry->file_offset ||
        entry->file_offset + entry->len <= file_offset)
        return 0;
    return 1;
}

/*
 * look find the first ordered struct that has this offset, otherwise
 * the first one less than this offset
 */
static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
                      u64 file_offset)
{
    struct rb_root *root = &tree->tree;
    struct rb_node *prev = NULL;
    struct rb_node *ret;
    struct btrfs_ordered_extent *entry;

    if (tree->last) {
        entry = rb_entry(tree->last, struct btrfs_ordered_extent,
                 rb_node);
        if (offset_in_entry(entry, file_offset))
            return tree->last;
    }
    ret = __tree_search(root, file_offset, &prev);
    if (!ret)
        ret = prev;
    if (ret)
        tree->last = ret;
    return ret;
}

/* allocate and add a new ordered_extent into the per-inode tree.
 * file_offset is the logical offset in the file
 *
 * start is the disk block number of an extent already reserved in the
 * extent allocation tree
 *
 * len is the length of the extent
 *
 * The tree is given a single reference on the ordered extent that was
 * inserted.
 */
static int __btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
                      u64 start, u64 len, u64 disk_len,
                      int type, int dio, int compress_type)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry;

    tree = &BTRFS_I(inode)->ordered_tree;
    entry = kmem_cache_zalloc(btrfs_ordered_extent_cache, GFP_NOFS);
    if (!entry)
        return -ENOMEM;

    entry->file_offset = file_offset;
    entry->start = start;
    entry->len = len;
    entry->disk_len = disk_len;
    entry->bytes_left = len;
    entry->inode = igrab(inode);
    entry->compress_type = compress_type;
    if (type != BTRFS_ORDERED_IO_DONE && type != BTRFS_ORDERED_COMPLETE)
        set_bit(type, &entry->flags);

    if (dio)
        set_bit(BTRFS_ORDERED_DIRECT, &entry->flags);

    /* one ref for the tree */
    atomic_set(&entry->refs, 1);
    init_waitqueue_head(&entry->wait);
    INIT_LIST_HEAD(&entry->list);
    INIT_LIST_HEAD(&entry->root_extent_list);

    trace_btrfs_ordered_extent_add(inode, entry);

    spin_lock_irq(&tree->lock);
    node = tree_insert(&tree->tree, file_offset,
               &entry->rb_node);
    if (node)
        ordered_data_tree_panic(inode, -EEXIST, file_offset);
    spin_unlock_irq(&tree->lock);

    spin_lock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);
    list_add_tail(&entry->root_extent_list,
              &BTRFS_I(inode)->root->fs_info->ordered_extents);
    spin_unlock(&BTRFS_I(inode)->root->fs_info->ordered_extent_lock);

    return 0;
}

int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
                 u64 start, u64 len, u64 disk_len, int type)
{
    return __btrfs_add_ordered_extent(inode, file_offset, start, len,
                      disk_len, type, 0,
                      BTRFS_COMPRESS_NONE);
}

int btrfs_add_ordered_extent_dio(struct inode *inode, u64 file_offset,
                 u64 start, u64 len, u64 disk_len, int type)
{
    return __btrfs_add_ordered_extent(inode, file_offset, start, len,
                      disk_len, type, 1,
                      BTRFS_COMPRESS_NONE);
}

int btrfs_add_ordered_extent_compress(struct inode *inode, u64 file_offset,
                      u64 start, u64 len, u64 disk_len,
                      int type, int compress_type)
{
    return __btrfs_add_ordered_extent(inode, file_offset, start, len,
                      disk_len, type, 0,
                      compress_type);
}

/*
 * Add a struct btrfs_ordered_sum into the list of checksums to be inserted
 * when an ordered extent is finished.  If the list covers more than one
 * ordered extent, it is split across multiples.
 */
void btrfs_add_ordered_sum(struct inode *inode,
               struct btrfs_ordered_extent *entry,
               struct btrfs_ordered_sum *sum)
{
    struct btrfs_ordered_inode_tree *tree;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irq(&tree->lock);
    list_add_tail(&sum->list, &entry->list);
    spin_unlock_irq(&tree->lock);
}

/*
 * this is used to account for finished IO across a given range
 * of the file.  The IO may span ordered extents.  If
 * a given ordered_extent is completely done, 1 is returned, otherwise
 * 0.
 *
 * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
 * to make sure this function only returns 1 once for a given ordered extent.
 *
 * file_offset is updated to one byte past the range that is recorded as
 * complete.  This allows you to walk forward in the file.
 */
int btrfs_dec_test_first_ordered_pending(struct inode *inode,
                   struct btrfs_ordered_extent **cached,
                   u64 *file_offset, u64 io_size, int uptodate)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry = NULL;
    int ret;
    unsigned long flags;
    u64 dec_end;
    u64 dec_start;
    u64 to_dec;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irqsave(&tree->lock, flags);
    node = tree_search(tree, *file_offset);
    if (!node) {
        ret = 1;
        goto out;
    }

    entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
    if (!offset_in_entry(entry, *file_offset)) {
        ret = 1;
        goto out;
    }

    dec_start = max(*file_offset, entry->file_offset);
    dec_end = min(*file_offset + io_size, entry->file_offset +
              entry->len);
    *file_offset = dec_end;
    if (dec_start > dec_end) {
        printk(KERN_CRIT "bad ordering dec_start %llu end %llu\n",
               (unsigned long long)dec_start,
               (unsigned long long)dec_end);
    }
    to_dec = dec_end - dec_start;
    if (to_dec > entry->bytes_left) {
        printk(KERN_CRIT "bad ordered accounting left %llu size %llu\n",
               (unsigned long long)entry->bytes_left,
               (unsigned long long)to_dec);
    }
    entry->bytes_left -= to_dec;
    if (!uptodate)
        set_bit(BTRFS_ORDERED_IOERR, &entry->flags);

    if (entry->bytes_left == 0)
        ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
    else
        ret = 1;
out:
    if (!ret && cached && entry) {
        *cached = entry;
        atomic_inc(&entry->refs);
    }
    spin_unlock_irqrestore(&tree->lock, flags);
    return ret == 0;
}

/*
 * this is used to account for finished IO across a given range
 * of the file.  The IO should not span ordered extents.  If
 * a given ordered_extent is completely done, 1 is returned, otherwise
 * 0.
 *
 * test_and_set_bit on a flag in the struct btrfs_ordered_extent is used
 * to make sure this function only returns 1 once for a given ordered extent.
 */
int btrfs_dec_test_ordered_pending(struct inode *inode,
                   struct btrfs_ordered_extent **cached,
                   u64 file_offset, u64 io_size, int uptodate)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry = NULL;
    unsigned long flags;
    int ret;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irqsave(&tree->lock, flags);
    if (cached && *cached) {
        entry = *cached;
        goto have_entry;
    }

    node = tree_search(tree, file_offset);
    if (!node) {
        ret = 1;
        goto out;
    }

    entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
have_entry:
    if (!offset_in_entry(entry, file_offset)) {
        ret = 1;
        goto out;
    }

    if (io_size > entry->bytes_left) {
        printk(KERN_CRIT "bad ordered accounting left %llu size %llu\n",
               (unsigned long long)entry->bytes_left,
               (unsigned long long)io_size);
    }
    entry->bytes_left -= io_size;
    if (!uptodate)
        set_bit(BTRFS_ORDERED_IOERR, &entry->flags);

    if (entry->bytes_left == 0)
        ret = test_and_set_bit(BTRFS_ORDERED_IO_DONE, &entry->flags);
    else
        ret = 1;
out:
    if (!ret && cached && entry) {
        *cached = entry;
        atomic_inc(&entry->refs);
    }
    spin_unlock_irqrestore(&tree->lock, flags);
    return ret == 0;
}

/*
 * used to drop a reference on an ordered extent.  This will free
 * the extent if the last reference is dropped
 */
void btrfs_put_ordered_extent(struct btrfs_ordered_extent *entry)
{
    struct list_head *cur;
    struct btrfs_ordered_sum *sum;

    trace_btrfs_ordered_extent_put(entry->inode, entry);

    if (atomic_dec_and_test(&entry->refs)) {
        if (entry->inode)
            btrfs_add_delayed_iput(entry->inode);
        while (!list_empty(&entry->list)) {
            cur = entry->list.next;
            sum = list_entry(cur, struct btrfs_ordered_sum, list);
            list_del(&sum->list);
            kfree(sum);
        }
        kmem_cache_free(btrfs_ordered_extent_cache, entry);
    }
}

/*
 * remove an ordered extent from the tree.  No references are dropped
 * and waiters are woken up.
 */
void btrfs_remove_ordered_extent(struct inode *inode,
                 struct btrfs_ordered_extent *entry)
{
    struct btrfs_ordered_inode_tree *tree;
    struct btrfs_root *root = BTRFS_I(inode)->root;
    struct rb_node *node;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irq(&tree->lock);
    node = &entry->rb_node;
    rb_erase(node, &tree->tree);
    tree->last = NULL;
    set_bit(BTRFS_ORDERED_COMPLETE, &entry->flags);
    spin_unlock_irq(&tree->lock);

    spin_lock(&root->fs_info->ordered_extent_lock);
    list_del_init(&entry->root_extent_list);

    trace_btrfs_ordered_extent_remove(inode, entry);

    /*
     * we have no more ordered extents for this inode and
     * no dirty pages.  We can safely remove it from the
     * list of ordered extents
     */
    if (RB_EMPTY_ROOT(&tree->tree) &&
        !mapping_tagged(inode->i_mapping, PAGECACHE_TAG_DIRTY)) {
        list_del_init(&BTRFS_I(inode)->ordered_operations);
    }
    spin_unlock(&root->fs_info->ordered_extent_lock);
    wake_up(&entry->wait);
}

/*
 * wait for all the ordered extents in a root.  This is done when balancing
 * space between drives.
 */
void btrfs_wait_ordered_extents(struct btrfs_root *root, int delay_iput)
{
    struct list_head splice;
    struct list_head *cur;
    struct btrfs_ordered_extent *ordered;
    struct inode *inode;

    INIT_LIST_HEAD(&splice);

    spin_lock(&root->fs_info->ordered_extent_lock);
    list_splice_init(&root->fs_info->ordered_extents, &splice);
    while (!list_empty(&splice)) {
        cur = splice.next;
        ordered = list_entry(cur, struct btrfs_ordered_extent,
                     root_extent_list);
        list_del_init(&ordered->root_extent_list);
        atomic_inc(&ordered->refs);

        /*
         * the inode may be getting freed (in sys_unlink path).
         */
        inode = igrab(ordered->inode);

        spin_unlock(&root->fs_info->ordered_extent_lock);

        if (inode) {
            btrfs_start_ordered_extent(inode, ordered, 1);
            btrfs_put_ordered_extent(ordered);
            if (delay_iput)
                btrfs_add_delayed_iput(inode);
            else
                iput(inode);
        } else {
            btrfs_put_ordered_extent(ordered);
        }

        spin_lock(&root->fs_info->ordered_extent_lock);
    }
    spin_unlock(&root->fs_info->ordered_extent_lock);
}

/*
 * this is used during transaction commit to write all the inodes
 * added to the ordered operation list.  These files must be fully on
 * disk before the transaction commits.
 *
 * we have two modes here, one is to just start the IO via filemap_flush
 * and the other is to wait for all the io.  When we wait, we have an
 * extra check to make sure the ordered operation list really is empty
 * before we return
 */
void btrfs_run_ordered_operations(struct btrfs_root *root, int wait)
{
    struct btrfs_inode *btrfs_inode;
    struct inode *inode;
    struct list_head splice;

    INIT_LIST_HEAD(&splice);

    mutex_lock(&root->fs_info->ordered_operations_mutex);
    spin_lock(&root->fs_info->ordered_extent_lock);
again:
    list_splice_init(&root->fs_info->ordered_operations, &splice);

    while (!list_empty(&splice)) {
        btrfs_inode = list_entry(splice.next, struct btrfs_inode,
                   ordered_operations);

        inode = &btrfs_inode->vfs_inode;

        list_del_init(&btrfs_inode->ordered_operations);

        /*
         * the inode may be getting freed (in sys_unlink path).
         */
        inode = igrab(inode);

        if (!wait && inode) {
            list_add_tail(&BTRFS_I(inode)->ordered_operations,
                  &root->fs_info->ordered_operations);
        }
        spin_unlock(&root->fs_info->ordered_extent_lock);

        if (inode) {
            if (wait)
                btrfs_wait_ordered_range(inode, 0, (u64)-1);
            else
                filemap_flush(inode->i_mapping);
            btrfs_add_delayed_iput(inode);
        }

        cond_resched();
        spin_lock(&root->fs_info->ordered_extent_lock);
    }
    if (wait && !list_empty(&root->fs_info->ordered_operations))
        goto again;

    spin_unlock(&root->fs_info->ordered_extent_lock);
    mutex_unlock(&root->fs_info->ordered_operations_mutex);
}

/*
 * Used to start IO or wait for a given ordered extent to finish.
 *
 * If wait is one, this effectively waits on page writeback for all the pages
 * in the extent, and it waits on the io completion code to insert
 * metadata into the btree corresponding to the extent
 */
void btrfs_start_ordered_extent(struct inode *inode,
                       struct btrfs_ordered_extent *entry,
                       int wait)
{
    u64 start = entry->file_offset;
    u64 end = start + entry->len - 1;

    trace_btrfs_ordered_extent_start(inode, entry);

    /*
     * pages in the range can be dirty, clean or writeback.  We
     * start IO on any dirty ones so the wait doesn't stall waiting
     * for the flusher thread to find them
     */
    if (!test_bit(BTRFS_ORDERED_DIRECT, &entry->flags))
        filemap_fdatawrite_range(inode->i_mapping, start, end);
    if (wait) {
        wait_event(entry->wait, test_bit(BTRFS_ORDERED_COMPLETE,
                         &entry->flags));
    }
}

/*
 * Used to wait on ordered extents across a large range of bytes.
 */
void btrfs_wait_ordered_range(struct inode *inode, u64 start, u64 len)
{
    u64 end;
    u64 orig_end;
    struct btrfs_ordered_extent *ordered;
    int found;

    if (start + len < start) {
        orig_end = INT_LIMIT(loff_t);
    } else {
        orig_end = start + len - 1;
        if (orig_end > INT_LIMIT(loff_t))
            orig_end = INT_LIMIT(loff_t);
    }

    /* start IO across the range first to instantiate any delalloc
     * extents
     */
    filemap_fdatawrite_range(inode->i_mapping, start, orig_end);

    /*
     * So with compression we will find and lock a dirty page and clear the
     * first one as dirty, setup an async extent, and immediately return
     * with the entire range locked but with nobody actually marked with
     * writeback.  So we can't just filemap_write_and_wait_range() and
     * expect it to work since it will just kick off a thread to do the
     * actual work.  So we need to call filemap_fdatawrite_range _again_
     * since it will wait on the page lock, which won't be unlocked until
     * after the pages have been marked as writeback and so we're good to go
     * from there.  We have to do this otherwise we'll miss the ordered
     * extents and that results in badness.  Please Josef, do not think you
     * know better and pull this out at some point in the future, it is
     * right and you are wrong.
     */
    if (test_bit(BTRFS_INODE_HAS_ASYNC_EXTENT,
             &BTRFS_I(inode)->runtime_flags))
        filemap_fdatawrite_range(inode->i_mapping, start, orig_end);

    filemap_fdatawait_range(inode->i_mapping, start, orig_end);

    end = orig_end;
    found = 0;
    while (1) {
        ordered = btrfs_lookup_first_ordered_extent(inode, end);
        if (!ordered)
            break;
        if (ordered->file_offset > orig_end) {
            btrfs_put_ordered_extent(ordered);
            break;
        }
        if (ordered->file_offset + ordered->len < start) {
            btrfs_put_ordered_extent(ordered);
            break;
        }
        found++;
        btrfs_start_ordered_extent(inode, ordered, 1);
        end = ordered->file_offset;
        btrfs_put_ordered_extent(ordered);
        if (end == 0 || end == start)
            break;
        end--;
    }
}

/*
 * find an ordered extent corresponding to file_offset.  return NULL if
 * nothing is found, otherwise take a reference on the extent and return it
 */
struct btrfs_ordered_extent *btrfs_lookup_ordered_extent(struct inode *inode,
                             u64 file_offset)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry = NULL;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irq(&tree->lock);
    node = tree_search(tree, file_offset);
    if (!node)
        goto out;

    entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
    if (!offset_in_entry(entry, file_offset))
        entry = NULL;
    if (entry)
        atomic_inc(&entry->refs);
out:
    spin_unlock_irq(&tree->lock);
    return entry;
}

/* Since the DIO code tries to lock a wide area we need to look for any ordered
 * extents that exist in the range, rather than just the start of the range.
 */
struct btrfs_ordered_extent *btrfs_lookup_ordered_range(struct inode *inode,
                            u64 file_offset,
                            u64 len)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry = NULL;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irq(&tree->lock);
    node = tree_search(tree, file_offset);
    if (!node) {
        node = tree_search(tree, file_offset + len);
        if (!node)
            goto out;
    }

    while (1) {
        entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
        if (range_overlaps(entry, file_offset, len))
            break;

        if (entry->file_offset >= file_offset + len) {
            entry = NULL;
            break;
        }
        entry = NULL;
        node = rb_next(node);
        if (!node)
            break;
    }
out:
    if (entry)
        atomic_inc(&entry->refs);
    spin_unlock_irq(&tree->lock);
    return entry;
}

/*
 * lookup and return any extent before 'file_offset'.  NULL is returned
 * if none is found
 */
struct btrfs_ordered_extent *
btrfs_lookup_first_ordered_extent(struct inode *inode, u64 file_offset)
{
    struct btrfs_ordered_inode_tree *tree;
    struct rb_node *node;
    struct btrfs_ordered_extent *entry = NULL;

    tree = &BTRFS_I(inode)->ordered_tree;
    spin_lock_irq(&tree->lock);
    node = tree_search(tree, file_offset);
    if (!node)
        goto out;

    entry = rb_entry(node, struct btrfs_ordered_extent, rb_node);
    atomic_inc(&entry->refs);
out:
    spin_unlock_irq(&tree->lock);
    return entry;
}

/*
 * After an extent is done, call this to conditionally update the on disk
 * i_size.  i_size is updated to cover any fully written part of the file.
 */
int btrfs_ordered_update_i_size(struct inode *inode, u64 offset,
                struct btrfs_ordered_extent *ordered)
{
    struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
    u64 disk_i_size;
    u64 new_i_size;
    u64 i_size = i_size_read(inode);
    struct rb_node *node;
    struct rb_node *prev = NULL;
    struct btrfs_ordered_extent *test;
    int ret = 1;

    if (ordered)
        offset = entry_end(ordered);
    else
        offset = ALIGN(offset, BTRFS_I(inode)->root->sectorsize);

    spin_lock_irq(&tree->lock);
    disk_i_size = BTRFS_I(inode)->disk_i_size;

    /* truncate file */
    if (disk_i_size > i_size) {
        BTRFS_I(inode)->disk_i_size = i_size;
        ret = 0;
        goto out;
    }

    /*
     * if the disk i_size is already at the inode->i_size, or
     * this ordered extent is inside the disk i_size, we're done
     */
    if (disk_i_size == i_size || offset <= disk_i_size) {
        goto out;
    }

    /*
     * walk backward from this ordered extent to disk_i_size.
     * if we find an ordered extent then we can't update disk i_size
     * yet
     */
    if (ordered) {
        node = rb_prev(&ordered->rb_node);
    } else {
        prev = tree_search(tree, offset);
        /*
         * we insert file extents without involving ordered struct,
         * so there should be no ordered struct cover this offset
         */
        if (prev) {
            test = rb_entry(prev, struct btrfs_ordered_extent,
                    rb_node);
            BUG_ON(offset_in_entry(test, offset));
        }
        node = prev;
    }
    for (; node; node = rb_prev(node)) {
        test = rb_entry(node, struct btrfs_ordered_extent, rb_node);

        /* We treat this entry as if it doesnt exist */
        if (test_bit(BTRFS_ORDERED_UPDATED_ISIZE, &test->flags))
            continue;
        if (test->file_offset + test->len <= disk_i_size)
            break;
        if (test->file_offset >= i_size)
            break;
        if (test->file_offset >= disk_i_size) {
            /*
             * we don't update disk_i_size now, so record this
             * undealt i_size. Or we will not know the real
             * i_size.
             */
            if (test->outstanding_isize < offset)
                test->outstanding_isize = offset;
            if (ordered &&
                ordered->outstanding_isize >
                test->outstanding_isize)
                test->outstanding_isize =
                        ordered->outstanding_isize;
            goto out;
        }
    }
    new_i_size = min_t(u64, offset, i_size);

    /*
     * Some ordered extents may completed before the current one, and
     * we hold the real i_size in ->outstanding_isize.
     */
    if (ordered && ordered->outstanding_isize > new_i_size)
        new_i_size = min_t(u64, ordered->outstanding_isize, i_size);
    BTRFS_I(inode)->disk_i_size = new_i_size;
    ret = 0;
out:
    /*
     * We need to do this because we can't remove ordered extents until
     * after the i_disk_size has been updated and then the inode has been
     * updated to reflect the change, so we need to tell anybody who finds
     * this ordered extent that we've already done all the real work, we
     * just haven't completed all the other work.
     */
    if (ordered)
        set_bit(BTRFS_ORDERED_UPDATED_ISIZE, &ordered->flags);
    spin_unlock_irq(&tree->lock);
    return ret;
}

/*
 * search the ordered extents for one corresponding to 'offset' and
 * try to find a checksum.  This is used because we allow pages to
 * be reclaimed before their checksum is actually put into the btree
 */
int btrfs_find_ordered_sum(struct inode *inode, u64 offset, u64 disk_bytenr,
               u32 *sum)
{
    struct btrfs_ordered_sum *ordered_sum;
    struct btrfs_sector_sum *sector_sums;
    struct btrfs_ordered_extent *ordered;
    struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
    unsigned long num_sectors;
    unsigned long i;
    u32 sectorsize = BTRFS_I(inode)->root->sectorsize;
    int ret = 1;

    ordered = btrfs_lookup_ordered_extent(inode, offset);
    if (!ordered)
        return 1;

    spin_lock_irq(&tree->lock);
    list_for_each_entry_reverse(ordered_sum, &ordered->list, list) {
        if (disk_bytenr >= ordered_sum->bytenr) {
            num_sectors = ordered_sum->len / sectorsize;
            sector_sums = ordered_sum->sums;
            for (i = 0; i < num_sectors; i++) {
                if (sector_sums[i].bytenr == disk_bytenr) {
                    *sum = sector_sums[i].sum;
                    ret = 0;
                    goto out;
                }
            }
        }
    }
out:
    spin_unlock_irq(&tree->lock);
    btrfs_put_ordered_extent(ordered);
    return ret;
}


/*
 * add a given inode to the list of inodes that must be fully on
 * disk before a transaction commit finishes.
 *
 * This basically gives us the ext3 style data=ordered mode, and it is mostly
 * used to make sure renamed files are fully on disk.
 *
 * It is a noop if the inode is already fully on disk.
 *
 * If trans is not null, we'll do a friendly check for a transaction that
 * is already flushing things and force the IO down ourselves.
 */
void btrfs_add_ordered_operation(struct btrfs_trans_handle *trans,
                 struct btrfs_root *root, struct inode *inode)
{
    u64 last_mod;

    last_mod = max(BTRFS_I(inode)->generation, BTRFS_I(inode)->last_trans);

    /*
     * if this file hasn't been changed since the last transaction
     * commit, we can safely return without doing anything
     */
    if (last_mod < root->fs_info->last_trans_committed)
        return;

    /*
     * the transaction is already committing.  Just start the IO and
     * don't bother with all of this list nonsense
     */
    if (trans && root->fs_info->running_transaction->blocked) {
        btrfs_wait_ordered_range(inode, 0, (u64)-1);
        return;
    }

    spin_lock(&root->fs_info->ordered_extent_lock);
    if (list_empty(&BTRFS_I(inode)->ordered_operations)) {
        list_add_tail(&BTRFS_I(inode)->ordered_operations,
                  &root->fs_info->ordered_operations);
    }
    spin_unlock(&root->fs_info->ordered_extent_lock);
}

int __init ordered_data_init(void)
{
    btrfs_ordered_extent_cache = kmem_cache_create("btrfs_ordered_extent",
                     sizeof(struct btrfs_ordered_extent), 0,
                     SLAB_RECLAIM_ACCOUNT | SLAB_MEM_SPREAD,
                     NULL);
    if (!btrfs_ordered_extent_cache)
        return -ENOMEM;
    return 0;
}

void ordered_data_exit(void)
{
    if (btrfs_ordered_extent_cache)
        kmem_cache_destroy(btrfs_ordered_extent_cache);
}