/*
 * 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/fs.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/mpage.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include "ctree.h"
#include "disk-io.h"
#include "transaction.h"
#include "btrfs_inode.h"
#include "ioctl.h"
#include "print-tree.h"
#include "tree-log.h"
#include "locking.h"
#include "compat.h"


/* simple helper to fault in pages and copy.  This should go away
 * and be replaced with calls into generic code.
 */
static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
                                         int write_bytes,
                                         struct page **prepared_pages,
                                         const char __user *buf)
{
        long page_fault = 0;
        int i;
        int offset = pos & (PAGE_CACHE_SIZE - 1);

        for (i = 0; i < num_pages && write_bytes > 0; i++, offset = 0) {
                size_t count = min_t(size_t,
                                     PAGE_CACHE_SIZE - offset, write_bytes);
                struct page *page = prepared_pages[i];
                fault_in_pages_readable(buf, count);

                /* Copy data from userspace to the current page */
                kmap(page);
                page_fault = __copy_from_user(page_address(page) + offset,
                                              buf, count);
                /* Flush processor's dcache for this page */
                flush_dcache_page(page);
                kunmap(page);
                buf += count;
                write_bytes -= count;

                if (page_fault)
                        break;
        }
        return page_fault ? -EFAULT : 0;
}

/*
 * unlocks pages after btrfs_file_write is done with them
 */
static noinline void btrfs_drop_pages(struct page **pages, size_t num_pages)
{
        size_t i;
        for (i = 0; i < num_pages; i++) {
                if (!pages[i])
                        break;
                /* page checked is some magic around finding pages that
                 * have been modified without going through btrfs_set_page_dirty
                 * clear it here
                 */
                ClearPageChecked(pages[i]);
                unlock_page(pages[i]);
                mark_page_accessed(pages[i]);
                page_cache_release(pages[i]);
        }
}

/*
 * after copy_from_user, pages need to be dirtied and we need to make
 * sure holes are created between the current EOF and the start of
 * any next extents (if required).
 *
 * this also makes the decision about creating an inline extent vs
 * doing real data extents, marking pages dirty and delalloc as required.
 */
static noinline int dirty_and_release_pages(struct btrfs_trans_handle *trans,
                                   struct btrfs_root *root,
                                   struct file *file,
                                   struct page **pages,
                                   size_t num_pages,
                                   loff_t pos,
                                   size_t write_bytes)
{
        int err = 0;
        int i;
        struct inode *inode = fdentry(file)->d_inode;
        u64 num_bytes;
        u64 start_pos;
        u64 end_of_last_block;
        u64 end_pos = pos + write_bytes;
        loff_t isize = i_size_read(inode);

        start_pos = pos & ~((u64)root->sectorsize - 1);
        num_bytes = (write_bytes + pos - start_pos +
                    root->sectorsize - 1) & ~((u64)root->sectorsize - 1);

        end_of_last_block = start_pos + num_bytes - 1;
        err = btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block);
        if (err)
                return err;

        for (i = 0; i < num_pages; i++) {
                struct page *p = pages[i];
                SetPageUptodate(p);
                ClearPageChecked(p);
                set_page_dirty(p);
        }
        if (end_pos > isize) {
                i_size_write(inode, end_pos);
                /* we've only changed i_size in ram, and we haven't updated
                 * the disk i_size.  There is no need to log the inode
                 * at this time.
                 */
        }
        return err;
}

/*
 * this drops all the extents in the cache that intersect the range
 * [start, end].  Existing extents are split as required.
 */
int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
                            int skip_pinned)
{
        struct extent_map *em;
        struct extent_map *split = NULL;
        struct extent_map *split2 = NULL;
        struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
        u64 len = end - start + 1;
        int ret;
        int testend = 1;
        unsigned long flags;
        int compressed = 0;

        WARN_ON(end < start);
        if (end == (u64)-1) {
                len = (u64)-1;
                testend = 0;
        }
        while (1) {
                if (!split)
                        split = alloc_extent_map(GFP_NOFS);
                if (!split2)
                        split2 = alloc_extent_map(GFP_NOFS);

                write_lock(&em_tree->lock);
                em = lookup_extent_mapping(em_tree, start, len);
                if (!em) {
                        write_unlock(&em_tree->lock);
                        break;
                }
                flags = em->flags;
                if (skip_pinned && test_bit(EXTENT_FLAG_PINNED, &em->flags)) {
                        if (em->start <= start &&
                            (!testend || em->start + em->len >= start + len)) {
                                free_extent_map(em);
                                write_unlock(&em_tree->lock);
                                break;
                        }
                        if (start < em->start) {
                                len = em->start - start;
                        } else {
                                len = start + len - (em->start + em->len);
                                start = em->start + em->len;
                        }
                        free_extent_map(em);
                        write_unlock(&em_tree->lock);
                        continue;
                }
                compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
                clear_bit(EXTENT_FLAG_PINNED, &em->flags);
                remove_extent_mapping(em_tree, em);

                if (em->block_start < EXTENT_MAP_LAST_BYTE &&
                    em->start < start) {
                        split->start = em->start;
                        split->len = start - em->start;
                        split->orig_start = em->orig_start;
                        split->block_start = em->block_start;

                        if (compressed)
                                split->block_len = em->block_len;
                        else
                                split->block_len = split->len;

                        split->bdev = em->bdev;
                        split->flags = flags;
                        ret = add_extent_mapping(em_tree, split);
                        BUG_ON(ret);
                        free_extent_map(split);
                        split = split2;
                        split2 = NULL;
                }
                if (em->block_start < EXTENT_MAP_LAST_BYTE &&
                    testend && em->start + em->len > start + len) {
                        u64 diff = start + len - em->start;

                        split->start = start + len;
                        split->len = em->start + em->len - (start + len);
                        split->bdev = em->bdev;
                        split->flags = flags;

                        if (compressed) {
                                split->block_len = em->block_len;
                                split->block_start = em->block_start;
                                split->orig_start = em->orig_start;
                        } else {
                                split->block_len = split->len;
                                split->block_start = em->block_start + diff;
                                split->orig_start = split->start;
                        }

                        ret = add_extent_mapping(em_tree, split);
                        BUG_ON(ret);
                        free_extent_map(split);
                        split = NULL;
                }
                write_unlock(&em_tree->lock);

                /* once for us */
                free_extent_map(em);
                /* once for the tree*/
                free_extent_map(em);
        }
        if (split)
                free_extent_map(split);
        if (split2)
                free_extent_map(split2);
        return 0;
}

/*
 * this is very complex, but the basic idea is to drop all extents
 * in the range start - end.  hint_block is filled in with a block number
 * that would be a good hint to the block allocator for this file.
 *
 * If an extent intersects the range but is not entirely inside the range
 * it is either truncated or split.  Anything entirely inside the range
 * is deleted from the tree.
 *
 * inline_limit is used to tell this code which offsets in the file to keep
 * if they contain inline extents.
 */
noinline int btrfs_drop_extents(struct btrfs_trans_handle *trans,
                       struct btrfs_root *root, struct inode *inode,
                       u64 start, u64 end, u64 locked_end,
                       u64 inline_limit, u64 *hint_byte, int drop_cache)
{
        u64 extent_end = 0;
        u64 search_start = start;
        u64 ram_bytes = 0;
        u64 disk_bytenr = 0;
        u64 orig_locked_end = locked_end;
        u8 compression;
        u8 encryption;
        u16 other_encoding = 0;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *extent;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_file_extent_item old;
        int keep;
        int slot;
        int bookend;
        int found_type = 0;
        int found_extent;
        int found_inline;
        int recow;
        int ret;

        inline_limit = 0;
        if (drop_cache)
                btrfs_drop_extent_cache(inode, start, end - 1, 0);

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
        while (1) {
                recow = 0;
                btrfs_release_path(root, path);
                ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
                                               search_start, -1);
                if (ret < 0)
                        goto out;
                if (ret > 0) {
                        if (path->slots[0] == 0) {
                                ret = 0;
                                goto out;
                        }
                        path->slots[0]--;
                }
next_slot:
                keep = 0;
                bookend = 0;
                found_extent = 0;
                found_inline = 0;
                compression = 0;
                encryption = 0;
                extent = NULL;
                leaf = path->nodes[0];
                slot = path->slots[0];
                ret = 0;
                btrfs_item_key_to_cpu(leaf, &key, slot);
                if (btrfs_key_type(&key) == BTRFS_EXTENT_DATA_KEY &&
                    key.offset >= end) {
                        goto out;
                }
                if (btrfs_key_type(&key) > BTRFS_EXTENT_DATA_KEY ||
                    key.objectid != inode->i_ino) {
                        goto out;
                }
                if (recow) {
                        search_start = max(key.offset, start);
                        continue;
                }
                if (btrfs_key_type(&key) == BTRFS_EXTENT_DATA_KEY) {
                        extent = btrfs_item_ptr(leaf, slot,
                                                struct btrfs_file_extent_item);
                        found_type = btrfs_file_extent_type(leaf, extent);
                        compression = btrfs_file_extent_compression(leaf,
                                                                    extent);
                        encryption = btrfs_file_extent_encryption(leaf,
                                                                  extent);
                        other_encoding = btrfs_file_extent_other_encoding(leaf,
                                                                  extent);
                        if (found_type == BTRFS_FILE_EXTENT_REG ||
                            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                                extent_end =
                                     btrfs_file_extent_disk_bytenr(leaf,
                                                                   extent);
                                if (extent_end)
                                        *hint_byte = extent_end;

                                extent_end = key.offset +
                                     btrfs_file_extent_num_bytes(leaf, extent);
                                ram_bytes = btrfs_file_extent_ram_bytes(leaf,
                                                                extent);
                                found_extent = 1;
                        } else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
                                found_inline = 1;
                                extent_end = key.offset +
                                     btrfs_file_extent_inline_len(leaf, extent);
                        }
                } else {
                        extent_end = search_start;
                }

                /* we found nothing we can drop */
                if ((!found_extent && !found_inline) ||
                    search_start >= extent_end) {
                        int nextret;
                        u32 nritems;
                        nritems = btrfs_header_nritems(leaf);
                        if (slot >= nritems - 1) {
                                nextret = btrfs_next_leaf(root, path);
                                if (nextret)
                                        goto out;
                                recow = 1;
                        } else {
                                path->slots[0]++;
                        }
                        goto next_slot;
                }

                if (end <= extent_end && start >= key.offset && found_inline)
                        *hint_byte = EXTENT_MAP_INLINE;

                if (found_extent) {
                        read_extent_buffer(leaf, &old, (unsigned long)extent,
                                           sizeof(old));
                }

                if (end < extent_end && end >= key.offset) {
                        bookend = 1;
                        if (found_inline && start <= key.offset)
                                keep = 1;
                }

                if (bookend && found_extent) {
                        if (locked_end < extent_end) {
                                ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
                                                locked_end, extent_end - 1,
                                                GFP_NOFS);
                                if (!ret) {
                                        btrfs_release_path(root, path);
                                        lock_extent(&BTRFS_I(inode)->io_tree,
                                                locked_end, extent_end - 1,
                                                GFP_NOFS);
                                        locked_end = extent_end;
                                        continue;
                                }
                                locked_end = extent_end;
                        }
                        disk_bytenr = le64_to_cpu(old.disk_bytenr);
                        if (disk_bytenr != 0) {
                                ret = btrfs_inc_extent_ref(trans, root,
                                           disk_bytenr,
                                           le64_to_cpu(old.disk_num_bytes), 0,
                                           root->root_key.objectid,
                                           key.objectid, key.offset -
                                           le64_to_cpu(old.offset));
                                BUG_ON(ret);
                        }
                }

                if (found_inline) {
                        u64 mask = root->sectorsize - 1;
                        search_start = (extent_end + mask) & ~mask;
                } else
                        search_start = extent_end;

                /* truncate existing extent */
                if (start > key.offset) {
                        u64 new_num;
                        u64 old_num;
                        keep = 1;
                        WARN_ON(start & (root->sectorsize - 1));
                        if (found_extent) {
                                new_num = start - key.offset;
                                old_num = btrfs_file_extent_num_bytes(leaf,
                                                                      extent);
                                *hint_byte =
                                        btrfs_file_extent_disk_bytenr(leaf,
                                                                      extent);
                                if (btrfs_file_extent_disk_bytenr(leaf,
                                                                  extent)) {
                                        inode_sub_bytes(inode, old_num -
                                                        new_num);
                                }
                                btrfs_set_file_extent_num_bytes(leaf,
                                                        extent, new_num);
                                btrfs_mark_buffer_dirty(leaf);
                        } else if (key.offset < inline_limit &&
                                   (end > extent_end) &&
                                   (inline_limit < extent_end)) {
                                u32 new_size;
                                new_size = btrfs_file_extent_calc_inline_size(
                                                   inline_limit - key.offset);
                                inode_sub_bytes(inode, extent_end -
                                                inline_limit);
                                btrfs_set_file_extent_ram_bytes(leaf, extent,
                                                        new_size);
                                if (!compression && !encryption) {
                                        btrfs_truncate_item(trans, root, path,
                                                            new_size, 1);
                                }
                        }
                }
                /* delete the entire extent */
                if (!keep) {
                        if (found_inline)
                                inode_sub_bytes(inode, extent_end -
                                                key.offset);
                        ret = btrfs_del_item(trans, root, path);
                        /* TODO update progress marker and return */
                        BUG_ON(ret);
                        extent = NULL;
                        btrfs_release_path(root, path);
                        /* the extent will be freed later */
                }
                if (bookend && found_inline && start <= key.offset) {
                        u32 new_size;
                        new_size = btrfs_file_extent_calc_inline_size(
                                                   extent_end - end);
                        inode_sub_bytes(inode, end - key.offset);
                        btrfs_set_file_extent_ram_bytes(leaf, extent,
                                                        new_size);
                        if (!compression && !encryption)
                                ret = btrfs_truncate_item(trans, root, path,
                                                          new_size, 0);
                        BUG_ON(ret);
                }
                /* create bookend, splitting the extent in two */
                if (bookend && found_extent) {
                        struct btrfs_key ins;
                        ins.objectid = inode->i_ino;
                        ins.offset = end;
                        btrfs_set_key_type(&ins, BTRFS_EXTENT_DATA_KEY);

                        btrfs_release_path(root, path);
                        path->leave_spinning = 1;
                        ret = btrfs_insert_empty_item(trans, root, path, &ins,
                                                      sizeof(*extent));
                        BUG_ON(ret);

                        leaf = path->nodes[0];
                        extent = btrfs_item_ptr(leaf, path->slots[0],
                                                struct btrfs_file_extent_item);
                        write_extent_buffer(leaf, &old,
                                            (unsigned long)extent, sizeof(old));

                        btrfs_set_file_extent_compression(leaf, extent,
                                                          compression);
                        btrfs_set_file_extent_encryption(leaf, extent,
                                                         encryption);
                        btrfs_set_file_extent_other_encoding(leaf, extent,
                                                             other_encoding);
                        btrfs_set_file_extent_offset(leaf, extent,
                                    le64_to_cpu(old.offset) + end - key.offset);
                        WARN_ON(le64_to_cpu(old.num_bytes) <
                                (extent_end - end));
                        btrfs_set_file_extent_num_bytes(leaf, extent,
                                                        extent_end - end);

                        /*
                         * set the ram bytes to the size of the full extent
                         * before splitting.  This is a worst case flag,
                         * but its the best we can do because we don't know
                         * how splitting affects compression
                         */
                        btrfs_set_file_extent_ram_bytes(leaf, extent,
                                                        ram_bytes);
                        btrfs_set_file_extent_type(leaf, extent, found_type);

                        btrfs_unlock_up_safe(path, 1);
                        btrfs_mark_buffer_dirty(path->nodes[0]);
                        btrfs_set_lock_blocking(path->nodes[0]);

                        path->leave_spinning = 0;
                        btrfs_release_path(root, path);
                        if (disk_bytenr != 0)
                                inode_add_bytes(inode, extent_end - end);
                }

                if (found_extent && !keep) {
                        u64 old_disk_bytenr = le64_to_cpu(old.disk_bytenr);

                        if (old_disk_bytenr != 0) {
                                inode_sub_bytes(inode,
                                                le64_to_cpu(old.num_bytes));
                                ret = btrfs_free_extent(trans, root,
                                                old_disk_bytenr,
                                                le64_to_cpu(old.disk_num_bytes),
                                                0, root->root_key.objectid,
                                                key.objectid, key.offset -
                                                le64_to_cpu(old.offset));
                                BUG_ON(ret);
                                *hint_byte = old_disk_bytenr;
                        }
                }

                if (search_start >= end) {
                        ret = 0;
                        goto out;
                }
        }
out:
        btrfs_free_path(path);
        if (locked_end > orig_locked_end) {
                unlock_extent(&BTRFS_I(inode)->io_tree, orig_locked_end,
                              locked_end - 1, GFP_NOFS);
        }
        return ret;
}

static int extent_mergeable(struct extent_buffer *leaf, int slot,
                            u64 objectid, u64 bytenr, u64 *start, u64 *end)
{
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 extent_end;

        if (slot < 0 || slot >= btrfs_header_nritems(leaf))
                return 0;

        btrfs_item_key_to_cpu(leaf, &key, slot);
        if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
                return 0;

        fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
        if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
            btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||
            btrfs_file_extent_compression(leaf, fi) ||
            btrfs_file_extent_encryption(leaf, fi) ||
            btrfs_file_extent_other_encoding(leaf, fi))
                return 0;

        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
        if ((*start && *start != key.offset) || (*end && *end != extent_end))
                return 0;

        *start = key.offset;
        *end = extent_end;
        return 1;
}

/*
 * Mark extent in the range start - end as written.
 *
 * This changes extent type from 'pre-allocated' to 'regular'. If only
 * part of extent is marked as written, the extent will be split into
 * two or three.
 */
int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
                              struct btrfs_root *root,
                              struct inode *inode, u64 start, u64 end)
{
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        u64 bytenr;
        u64 num_bytes;
        u64 extent_end;
        u64 orig_offset;
        u64 other_start;
        u64 other_end;
        u64 split = start;
        u64 locked_end = end;
        int extent_type;
        int split_end = 1;
        int ret;

        btrfs_drop_extent_cache(inode, start, end - 1, 0);

        path = btrfs_alloc_path();
        BUG_ON(!path);
again:
        key.objectid = inode->i_ino;
        key.type = BTRFS_EXTENT_DATA_KEY;
        if (split == start)
                key.offset = split;
        else
                key.offset = split - 1;

        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret > 0 && path->slots[0] > 0)
                path->slots[0]--;

        leaf = path->nodes[0];
        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
        BUG_ON(key.objectid != inode->i_ino ||
               key.type != BTRFS_EXTENT_DATA_KEY);
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        extent_type = btrfs_file_extent_type(leaf, fi);
        BUG_ON(extent_type != BTRFS_FILE_EXTENT_PREALLOC);
        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
        BUG_ON(key.offset > start || extent_end < end);

        bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
        num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
        orig_offset = key.offset - btrfs_file_extent_offset(leaf, fi);

        if (key.offset == start)
                split = end;

        if (key.offset == start && extent_end == end) {
                int del_nr = 0;
                int del_slot = 0;
                other_start = end;
                other_end = 0;
                if (extent_mergeable(leaf, path->slots[0] + 1, inode->i_ino,
                                     bytenr, &other_start, &other_end)) {
                        extent_end = other_end;
                        del_slot = path->slots[0] + 1;
                        del_nr++;
                        ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
                                                0, root->root_key.objectid,
                                                inode->i_ino, orig_offset);
                        BUG_ON(ret);
                }
                other_start = 0;
                other_end = start;
                if (extent_mergeable(leaf, path->slots[0] - 1, inode->i_ino,
                                     bytenr, &other_start, &other_end)) {
                        key.offset = other_start;
                        del_slot = path->slots[0];
                        del_nr++;
                        ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
                                                0, root->root_key.objectid,
                                                inode->i_ino, orig_offset);
                        BUG_ON(ret);
                }
                split_end = 0;
                if (del_nr == 0) {
                        btrfs_set_file_extent_type(leaf, fi,
                                                   BTRFS_FILE_EXTENT_REG);
                        goto done;
                }

                fi = btrfs_item_ptr(leaf, del_slot - 1,
                                    struct btrfs_file_extent_item);
                btrfs_set_file_extent_type(leaf, fi, BTRFS_FILE_EXTENT_REG);
                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                extent_end - key.offset);
                btrfs_mark_buffer_dirty(leaf);

                ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
                BUG_ON(ret);
                goto release;
        } else if (split == start) {
                if (locked_end < extent_end) {
                        ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
                                        locked_end, extent_end - 1, GFP_NOFS);
                        if (!ret) {
                                btrfs_release_path(root, path);
                                lock_extent(&BTRFS_I(inode)->io_tree,
                                        locked_end, extent_end - 1, GFP_NOFS);
                                locked_end = extent_end;
                                goto again;
                        }
                        locked_end = extent_end;
                }
                btrfs_set_file_extent_num_bytes(leaf, fi, split - key.offset);
        } else  {
                BUG_ON(key.offset != start);
                key.offset = split;
                btrfs_set_file_extent_offset(leaf, fi, key.offset -
                                             orig_offset);
                btrfs_set_file_extent_num_bytes(leaf, fi, extent_end - split);
                btrfs_set_item_key_safe(trans, root, path, &key);
                extent_end = split;
        }

        if (extent_end == end) {
                split_end = 0;
                extent_type = BTRFS_FILE_EXTENT_REG;
        }
        if (extent_end == end && split == start) {
                other_start = end;
                other_end = 0;
                if (extent_mergeable(leaf, path->slots[0] + 1, inode->i_ino,
                                     bytenr, &other_start, &other_end)) {
                        path->slots[0]++;
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        key.offset = split;
                        btrfs_set_item_key_safe(trans, root, path, &key);
                        btrfs_set_file_extent_offset(leaf, fi, key.offset -
                                                     orig_offset);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        other_end - split);
                        goto done;
                }
        }
        if (extent_end == end && split == end) {
                other_start = 0;
                other_end = start;
                if (extent_mergeable(leaf, path->slots[0] - 1 , inode->i_ino,
                                     bytenr, &other_start, &other_end)) {
                        path->slots[0]--;
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi, extent_end -
                                                        other_start);
                        goto done;
                }
        }

        btrfs_mark_buffer_dirty(leaf);

        ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0,
                                   root->root_key.objectid,
                                   inode->i_ino, orig_offset);
        BUG_ON(ret);
        btrfs_release_path(root, path);

        key.offset = start;
        ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*fi));
        BUG_ON(ret);

        leaf = path->nodes[0];
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        btrfs_set_file_extent_generation(leaf, fi, trans->transid);
        btrfs_set_file_extent_type(leaf, fi, extent_type);
        btrfs_set_file_extent_disk_bytenr(leaf, fi, bytenr);
        btrfs_set_file_extent_disk_num_bytes(leaf, fi, num_bytes);
        btrfs_set_file_extent_offset(leaf, fi, key.offset - orig_offset);
        btrfs_set_file_extent_num_bytes(leaf, fi, extent_end - key.offset);
        btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
        btrfs_set_file_extent_compression(leaf, fi, 0);
        btrfs_set_file_extent_encryption(leaf, fi, 0);
        btrfs_set_file_extent_other_encoding(leaf, fi, 0);
done:
        btrfs_mark_buffer_dirty(leaf);

release:
        btrfs_release_path(root, path);
        if (split_end && split == start) {
                split = end;
                goto again;
        }
        if (locked_end > end) {
                unlock_extent(&BTRFS_I(inode)->io_tree, end, locked_end - 1,
                              GFP_NOFS);
        }
        btrfs_free_path(path);
        return 0;
}

/*
 * this gets pages into the page cache and locks them down, it also properly
 * waits for data=ordered extents to finish before allowing the pages to be
 * modified.
 */
static noinline int prepare_pages(struct btrfs_root *root, struct file *file,
                         struct page **pages, size_t num_pages,
                         loff_t pos, unsigned long first_index,
                         unsigned long last_index, size_t write_bytes)
{
        int i;
        unsigned long index = pos >> PAGE_CACHE_SHIFT;
        struct inode *inode = fdentry(file)->d_inode;
        int err = 0;
        u64 start_pos;
        u64 last_pos;

        start_pos = pos & ~((u64)root->sectorsize - 1);
        last_pos = ((u64)index + num_pages) << PAGE_CACHE_SHIFT;

        if (start_pos > inode->i_size) {
                err = btrfs_cont_expand(inode, start_pos);
                if (err)
                        return err;
        }

        memset(pages, 0, num_pages * sizeof(struct page *));
again:
        for (i = 0; i < num_pages; i++) {
                pages[i] = grab_cache_page(inode->i_mapping, index + i);
                if (!pages[i]) {
                        err = -ENOMEM;
                        BUG_ON(1);
                }
                wait_on_page_writeback(pages[i]);
        }
        if (start_pos < inode->i_size) {
                struct btrfs_ordered_extent *ordered;
                lock_extent(&BTRFS_I(inode)->io_tree,
                            start_pos, last_pos - 1, GFP_NOFS);
                ordered = btrfs_lookup_first_ordered_extent(inode,
                                                            last_pos - 1);
                if (ordered &&
                    ordered->file_offset + ordered->len > start_pos &&
                    ordered->file_offset < last_pos) {
                        btrfs_put_ordered_extent(ordered);
                        unlock_extent(&BTRFS_I(inode)->io_tree,
                                      start_pos, last_pos - 1, GFP_NOFS);
                        for (i = 0; i < num_pages; i++) {
                                unlock_page(pages[i]);
                                page_cache_release(pages[i]);
                        }
                        btrfs_wait_ordered_range(inode, start_pos,
                                                 last_pos - start_pos);
                        goto again;
                }
                if (ordered)
                        btrfs_put_ordered_extent(ordered);

                clear_extent_bits(&BTRFS_I(inode)->io_tree, start_pos,
                                  last_pos - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
                                  EXTENT_DO_ACCOUNTING,
                                  GFP_NOFS);
                unlock_extent(&BTRFS_I(inode)->io_tree,
                              start_pos, last_pos - 1, GFP_NOFS);
        }
        for (i = 0; i < num_pages; i++) {
                clear_page_dirty_for_io(pages[i]);
                set_page_extent_mapped(pages[i]);
                WARN_ON(!PageLocked(pages[i]));
        }
        return 0;
}

static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
                                size_t count, loff_t *ppos)
{
        loff_t pos;
        loff_t start_pos;
        ssize_t num_written = 0;
        ssize_t err = 0;
        int ret = 0;
        struct inode *inode = fdentry(file)->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct page **pages = NULL;
        int nrptrs;
        struct page *pinned[2];
        unsigned long first_index;
        unsigned long last_index;
        int will_write;

        will_write = ((file->f_flags & O_SYNC) || IS_SYNC(inode) ||
                      (file->f_flags & O_DIRECT));

        nrptrs = min((count + PAGE_CACHE_SIZE - 1) / PAGE_CACHE_SIZE,
                     PAGE_CACHE_SIZE / (sizeof(struct page *)));
        pinned[0] = NULL;
        pinned[1] = NULL;

        pos = *ppos;
        start_pos = pos;

        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

        /* do the reserve before the mutex lock in case we have to do some
         * flushing.  We wouldn't deadlock, but this is more polite.
         */
        err = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
        if (err)
                goto out_nolock;

        mutex_lock(&inode->i_mutex);

        current->backing_dev_info = inode->i_mapping->backing_dev_info;
        err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
        if (err)
                goto out;

        if (count == 0)
                goto out;

        err = file_remove_suid(file);
        if (err)
                goto out;

        file_update_time(file);

        pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);

        /* generic_write_checks can change our pos */
        start_pos = pos;

        BTRFS_I(inode)->sequence++;
        first_index = pos >> PAGE_CACHE_SHIFT;
        last_index = (pos + count) >> PAGE_CACHE_SHIFT;

        /*
         * there are lots of better ways to do this, but this code
         * makes sure the first and last page in the file range are
         * up to date and ready for cow
         */
        if ((pos & (PAGE_CACHE_SIZE - 1))) {
                pinned[0] = grab_cache_page(inode->i_mapping, first_index);
                if (!PageUptodate(pinned[0])) {
                        ret = btrfs_readpage(NULL, pinned[0]);
                        BUG_ON(ret);
                        wait_on_page_locked(pinned[0]);
                } else {
                        unlock_page(pinned[0]);
                }
        }
        if ((pos + count) & (PAGE_CACHE_SIZE - 1)) {
                pinned[1] = grab_cache_page(inode->i_mapping, last_index);
                if (!PageUptodate(pinned[1])) {
                        ret = btrfs_readpage(NULL, pinned[1]);
                        BUG_ON(ret);
                        wait_on_page_locked(pinned[1]);
                } else {
                        unlock_page(pinned[1]);
                }
        }

        while (count > 0) {
                size_t offset = pos & (PAGE_CACHE_SIZE - 1);
                size_t write_bytes = min(count, nrptrs *
                                        (size_t)PAGE_CACHE_SIZE -
                                         offset);
                size_t num_pages = (write_bytes + PAGE_CACHE_SIZE - 1) >>
                                        PAGE_CACHE_SHIFT;

                WARN_ON(num_pages > nrptrs);
                memset(pages, 0, sizeof(struct page *) * nrptrs);

                ret = btrfs_check_data_free_space(root, inode, write_bytes);
                if (ret)
                        goto out;

                ret = prepare_pages(root, file, pages, num_pages,
                                    pos, first_index, last_index,
                                    write_bytes);

                if (ret) {
                        btrfs_free_reserved_data_space(root, inode,
                                                       write_bytes);
                        goto out;
                }

                ret = btrfs_copy_from_user(pos, num_pages,
                                           write_bytes, pages, buf);
                if (ret) {
                        btrfs_free_reserved_data_space(root, inode,
                                                       write_bytes);
                        btrfs_drop_pages(pages, num_pages);
                        goto out;
                }

                ret = dirty_and_release_pages(NULL, root, file, pages,
                                              num_pages, pos, write_bytes);
                btrfs_drop_pages(pages, num_pages);
                if (ret) {
                        btrfs_free_reserved_data_space(root, inode,
                                                       write_bytes);
                        goto out;
                }

                if (will_write) {
                        filemap_fdatawrite_range(inode->i_mapping, pos,
                                                 pos + write_bytes - 1);
                } else {
                        balance_dirty_pages_ratelimited_nr(inode->i_mapping,
                                                           num_pages);
                        if (num_pages <
                            (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
                                btrfs_btree_balance_dirty(root, 1);
                        btrfs_throttle(root);
                }

                buf += write_bytes;
                count -= write_bytes;
                pos += write_bytes;
                num_written += write_bytes;

                cond_resched();
        }
out:
        mutex_unlock(&inode->i_mutex);
        if (ret)
                err = ret;
        btrfs_unreserve_metadata_for_delalloc(root, inode, 1);

out_nolock:
        kfree(pages);
        if (pinned[0])
                page_cache_release(pinned[0]);
        if (pinned[1])
                page_cache_release(pinned[1]);
        *ppos = pos;

        /*
         * we want to make sure fsync finds this change
         * but we haven't joined a transaction running right now.
         *
         * Later on, someone is sure to update the inode and get the
         * real transid recorded.
         *
         * We set last_trans now to the fs_info generation + 1,
         * this will either be one more than the running transaction
         * or the generation used for the next transaction if there isn't
         * one running right now.
         */
        BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;

        if (num_written > 0 && will_write) {
                struct btrfs_trans_handle *trans;

                err = btrfs_wait_ordered_range(inode, start_pos, num_written);
                if (err)
                        num_written = err;

                if ((file->f_flags & O_SYNC) || IS_SYNC(inode)) {
                        trans = btrfs_start_transaction(root, 1);
                        ret = btrfs_log_dentry_safe(trans, root,
                                                    file->f_dentry);
                        if (ret == 0) {
                                ret = btrfs_sync_log(trans, root);
                                if (ret == 0)
                                        btrfs_end_transaction(trans, root);
                                else
                                        btrfs_commit_transaction(trans, root);
                        } else if (ret != BTRFS_NO_LOG_SYNC) {
                                btrfs_commit_transaction(trans, root);
                        } else {
                                btrfs_end_transaction(trans, root);
                        }
                }
                if (file->f_flags & O_DIRECT) {
                        invalidate_mapping_pages(inode->i_mapping,
                              start_pos >> PAGE_CACHE_SHIFT,
                             (start_pos + num_written - 1) >> PAGE_CACHE_SHIFT);
                }
        }
        current->backing_dev_info = NULL;
        return num_written ? num_written : err;
}

int btrfs_release_file(struct inode *inode, struct file *filp)
{
        /*
         * ordered_data_close is set by settattr when we are about to truncate
         * a file from a non-zero size to a zero size.  This tries to
         * flush down new bytes that may have been written if the
         * application were using truncate to replace a file in place.
         */
        if (BTRFS_I(inode)->ordered_data_close) {
                BTRFS_I(inode)->ordered_data_close = 0;
                btrfs_add_ordered_operation(NULL, BTRFS_I(inode)->root, inode);
                if (inode->i_size > BTRFS_ORDERED_OPERATIONS_FLUSH_LIMIT)
                        filemap_flush(inode->i_mapping);
        }
        if (filp->private_data)
                btrfs_ioctl_trans_end(filp);
        return 0;
}

/*
 * fsync call for both files and directories.  This logs the inode into
 * the tree log instead of forcing full commits whenever possible.
 *
 * It needs to call filemap_fdatawait so that all ordered extent updates are
 * in the metadata btree are up to date for copying to the log.
 *
 * It drops the inode mutex before doing the tree log commit.  This is an
 * important optimization for directories because holding the mutex prevents
 * new operations on the dir while we write to disk.
 */
int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
{
        struct inode *inode = dentry->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;
        struct btrfs_trans_handle *trans;


        /* we wait first, since the writeback may change the inode */
        root->log_batch++;
        /* the VFS called filemap_fdatawrite for us */
        btrfs_wait_ordered_range(inode, 0, (u64)-1);
        root->log_batch++;

        /*
         * check the transaction that last modified this inode
         * and see if its already been committed
         */
        if (!BTRFS_I(inode)->last_trans)
                goto out;

        /*
         * if the last transaction that changed this file was before
         * the current transaction, we can bail out now without any
         * syncing
         */
        mutex_lock(&root->fs_info->trans_mutex);
        if (BTRFS_I(inode)->last_trans <=
            root->fs_info->last_trans_committed) {
                BTRFS_I(inode)->last_trans = 0;
                mutex_unlock(&root->fs_info->trans_mutex);
                goto out;
        }
        mutex_unlock(&root->fs_info->trans_mutex);

        /*
         * ok we haven't committed the transaction yet, lets do a commit
         */
        if (file && file->private_data)
                btrfs_ioctl_trans_end(file);

        trans = btrfs_start_transaction(root, 1);
        if (!trans) {
                ret = -ENOMEM;
                goto out;
        }

        ret = btrfs_log_dentry_safe(trans, root, dentry);
        if (ret < 0)
                goto out;

        /* we've logged all the items and now have a consistent
         * version of the file in the log.  It is possible that
         * someone will come in and modify the file, but that's
         * fine because the log is consistent on disk, and we
         * have references to all of the file's extents
         *
         * It is possible that someone will come in and log the
         * file again, but that will end up using the synchronization
         * inside btrfs_sync_log to keep things safe.
         */
        mutex_unlock(&dentry->d_inode->i_mutex);

        if (ret != BTRFS_NO_LOG_SYNC) {
                if (ret > 0) {
                        ret = btrfs_commit_transaction(trans, root);
                } else {
                        ret = btrfs_sync_log(trans, root);
                        if (ret == 0)
                                ret = btrfs_end_transaction(trans, root);
                        else
                                ret = btrfs_commit_transaction(trans, root);
                }
        } else {
                ret = btrfs_end_transaction(trans, root);
        }
        mutex_lock(&dentry->d_inode->i_mutex);
out:
        return ret > 0 ? EIO : ret;
}

static const struct vm_operations_struct btrfs_file_vm_ops = {
        .fault          = filemap_fault,
        .page_mkwrite   = btrfs_page_mkwrite,
};

static int btrfs_file_mmap(struct file  *filp, struct vm_area_struct *vma)
{
        vma->vm_ops = &btrfs_file_vm_ops;
        file_accessed(filp);
        return 0;
}

const struct file_operations btrfs_file_operations = {
        .llseek         = generic_file_llseek,
        .read           = do_sync_read,
        .aio_read       = generic_file_aio_read,
        .splice_read    = generic_file_splice_read,
        .write          = btrfs_file_write,
        .mmap           = btrfs_file_mmap,
        .open           = generic_file_open,
        .release        = btrfs_release_file,
        .fsync          = btrfs_sync_file,
        .unlocked_ioctl = btrfs_ioctl,
#ifdef CONFIG_COMPAT
        .compat_ioctl   = btrfs_ioctl,
#endif
};