/*
 * 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/falloc.h>
#include <linux/swap.h>
#include <linux/writeback.h>
#include <linux/statfs.h>
#include <linux/compat.h>
#include <linux/slab.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"

/*
 * when auto defrag is enabled we
 * queue up these defrag structs to remember which
 * inodes need defragging passes
 */
struct inode_defrag {
        struct rb_node rb_node;
        /* objectid */
        u64 ino;
        /*
         * transid where the defrag was added, we search for
         * extents newer than this
         */
        u64 transid;

        /* root objectid */
        u64 root;

        /* last offset we were able to defrag */
        u64 last_offset;

        /* if we've wrapped around back to zero once already */
        int cycled;
};

/* pop a record for an inode into the defrag tree.  The lock
 * must be held already
 *
 * If you're inserting a record for an older transid than an
 * existing record, the transid already in the tree is lowered
 *
 * If an existing record is found the defrag item you
 * pass in is freed
 */
static void __btrfs_add_inode_defrag(struct inode *inode,
                                    struct inode_defrag *defrag)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct inode_defrag *entry;
        struct rb_node **p;
        struct rb_node *parent = NULL;

        p = &root->fs_info->defrag_inodes.rb_node;
        while (*p) {
                parent = *p;
                entry = rb_entry(parent, struct inode_defrag, rb_node);

                if (defrag->ino < entry->ino)
                        p = &parent->rb_left;
                else if (defrag->ino > entry->ino)
                        p = &parent->rb_right;
                else {
                        /* if we're reinserting an entry for
                         * an old defrag run, make sure to
                         * lower the transid of our existing record
                         */
                        if (defrag->transid < entry->transid)
                                entry->transid = defrag->transid;
                        if (defrag->last_offset > entry->last_offset)
                                entry->last_offset = defrag->last_offset;
                        goto exists;
                }
        }
        BTRFS_I(inode)->in_defrag = 1;
        rb_link_node(&defrag->rb_node, parent, p);
        rb_insert_color(&defrag->rb_node, &root->fs_info->defrag_inodes);
        return;

exists:
        kfree(defrag);
        return;

}

/*
 * insert a defrag record for this inode if auto defrag is
 * enabled
 */
int btrfs_add_inode_defrag(struct btrfs_trans_handle *trans,
                           struct inode *inode)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct inode_defrag *defrag;
        u64 transid;

        if (!btrfs_test_opt(root, AUTO_DEFRAG))
                return 0;

        if (btrfs_fs_closing(root->fs_info))
                return 0;

        if (BTRFS_I(inode)->in_defrag)
                return 0;

        if (trans)
                transid = trans->transid;
        else
                transid = BTRFS_I(inode)->root->last_trans;

        defrag = kzalloc(sizeof(*defrag), GFP_NOFS);
        if (!defrag)
                return -ENOMEM;

        defrag->ino = btrfs_ino(inode);
        defrag->transid = transid;
        defrag->root = root->root_key.objectid;

        spin_lock(&root->fs_info->defrag_inodes_lock);
        if (!BTRFS_I(inode)->in_defrag)
                __btrfs_add_inode_defrag(inode, defrag);
        else
                kfree(defrag);
        spin_unlock(&root->fs_info->defrag_inodes_lock);
        return 0;
}

/*
 * must be called with the defrag_inodes lock held
 */
struct inode_defrag *btrfs_find_defrag_inode(struct btrfs_fs_info *info, u64 ino,
                                             struct rb_node **next)
{
        struct inode_defrag *entry = NULL;
        struct rb_node *p;
        struct rb_node *parent = NULL;

        p = info->defrag_inodes.rb_node;
        while (p) {
                parent = p;
                entry = rb_entry(parent, struct inode_defrag, rb_node);

                if (ino < entry->ino)
                        p = parent->rb_left;
                else if (ino > entry->ino)
                        p = parent->rb_right;
                else
                        return entry;
        }

        if (next) {
                while (parent && ino > entry->ino) {
                        parent = rb_next(parent);
                        entry = rb_entry(parent, struct inode_defrag, rb_node);
                }
                *next = parent;
        }
        return NULL;
}

/*
 * run through the list of inodes in the FS that need
 * defragging
 */
int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info)
{
        struct inode_defrag *defrag;
        struct btrfs_root *inode_root;
        struct inode *inode;
        struct rb_node *n;
        struct btrfs_key key;
        struct btrfs_ioctl_defrag_range_args range;
        u64 first_ino = 0;
        int num_defrag;
        int defrag_batch = 1024;

        memset(&range, 0, sizeof(range));
        range.len = (u64)-1;

        atomic_inc(&fs_info->defrag_running);
        spin_lock(&fs_info->defrag_inodes_lock);
        while(1) {
                n = NULL;

                /* find an inode to defrag */
                defrag = btrfs_find_defrag_inode(fs_info, first_ino, &n);
                if (!defrag) {
                        if (n)
                                defrag = rb_entry(n, struct inode_defrag, rb_node);
                        else if (first_ino) {
                                first_ino = 0;
                                continue;
                        } else {
                                break;
                        }
                }

                /* remove it from the rbtree */
                first_ino = defrag->ino + 1;
                rb_erase(&defrag->rb_node, &fs_info->defrag_inodes);

                if (btrfs_fs_closing(fs_info))
                        goto next_free;

                spin_unlock(&fs_info->defrag_inodes_lock);

                /* get the inode */
                key.objectid = defrag->root;
                btrfs_set_key_type(&key, BTRFS_ROOT_ITEM_KEY);
                key.offset = (u64)-1;
                inode_root = btrfs_read_fs_root_no_name(fs_info, &key);
                if (IS_ERR(inode_root))
                        goto next;

                key.objectid = defrag->ino;
                btrfs_set_key_type(&key, BTRFS_INODE_ITEM_KEY);
                key.offset = 0;

                inode = btrfs_iget(fs_info->sb, &key, inode_root, NULL);
                if (IS_ERR(inode))
                        goto next;

                /* do a chunk of defrag */
                BTRFS_I(inode)->in_defrag = 0;
                range.start = defrag->last_offset;
                num_defrag = btrfs_defrag_file(inode, NULL, &range, defrag->transid,
                                               defrag_batch);
                /*
                 * if we filled the whole defrag batch, there
                 * must be more work to do.  Queue this defrag
                 * again
                 */
                if (num_defrag == defrag_batch) {
                        defrag->last_offset = range.start;
                        __btrfs_add_inode_defrag(inode, defrag);
                        /*
                         * we don't want to kfree defrag, we added it back to
                         * the rbtree
                         */
                        defrag = NULL;
                } else if (defrag->last_offset && !defrag->cycled) {
                        /*
                         * we didn't fill our defrag batch, but
                         * we didn't start at zero.  Make sure we loop
                         * around to the start of the file.
                         */
                        defrag->last_offset = 0;
                        defrag->cycled = 1;
                        __btrfs_add_inode_defrag(inode, defrag);
                        defrag = NULL;
                }

                iput(inode);
next:
                spin_lock(&fs_info->defrag_inodes_lock);
next_free:
                kfree(defrag);
        }
        spin_unlock(&fs_info->defrag_inodes_lock);

        atomic_dec(&fs_info->defrag_running);

        /*
         * during unmount, we use the transaction_wait queue to
         * wait for the defragger to stop
         */
        wake_up(&fs_info->transaction_wait);
        return 0;
}

/* 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,
                                         size_t write_bytes,
                                         struct page **prepared_pages,
                                         struct iov_iter *i)
{
        size_t copied = 0;
        size_t total_copied = 0;
        int pg = 0;
        int offset = pos & (PAGE_CACHE_SIZE - 1);

        while (write_bytes > 0) {
                size_t count = min_t(size_t,
                                     PAGE_CACHE_SIZE - offset, write_bytes);
                struct page *page = prepared_pages[pg];
                /*
                 * Copy data from userspace to the current page
                 *
                 * Disable pagefault to avoid recursive lock since
                 * the pages are already locked
                 */
                pagefault_disable();
                copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
                pagefault_enable();

                /* Flush processor's dcache for this page */
                flush_dcache_page(page);

                /*
                 * if we get a partial write, we can end up with
                 * partially up to date pages.  These add
                 * a lot of complexity, so make sure they don't
                 * happen by forcing this copy to be retried.
                 *
                 * The rest of the btrfs_file_write code will fall
                 * back to page at a time copies after we return 0.
                 */
                if (!PageUptodate(page) && copied < count)
                        copied = 0;

                iov_iter_advance(i, copied);
                write_bytes -= copied;
                total_copied += copied;

                /* Return to btrfs_file_aio_write to fault page */
                if (unlikely(copied == 0))
                        break;

                if (unlikely(copied < PAGE_CACHE_SIZE - offset)) {
                        offset += copied;
                } else {
                        pg++;
                        offset = 0;
                }
        }
        return total_copied;
}

/*
 * unlocks pages after btrfs_file_write is done with them
 */
void btrfs_drop_pages(struct page **pages, size_t num_pages)
{
        size_t i;
        for (i = 0; i < num_pages; i++) {
                /* 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.
 */
int btrfs_dirty_pages(struct btrfs_root *root, struct inode *inode,
                      struct page **pages, size_t num_pages,
                      loff_t pos, size_t write_bytes,
                      struct extent_state **cached)
{
        int err = 0;
        int i;
        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,
                                        cached);
        if (err)
                return err;

        for (i = 0; i < num_pages; i++) {
                struct page *p = pages[i];
                SetPageUptodate(p);
                ClearPageChecked(p);
                set_page_dirty(p);
        }

        /*
         * 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.
         */
        if (end_pos > isize)
                i_size_write(inode, end_pos);
        return 0;
}

/*
 * 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();
                if (!split2)
                        split2 = alloc_extent_map();
                BUG_ON(!split || !split2);

                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 (testend && em->start + em->len >= start + len) {
                                free_extent_map(em);
                                write_unlock(&em_tree->lock);
                                break;
                        }
                        start = em->start + em->len;
                        if (testend)
                                len = start + len - (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;
                        split->compress_type = em->compress_type;
                        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;
                        split->compress_type = em->compress_type;

                        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.
 */
int btrfs_drop_extents(struct btrfs_trans_handle *trans, struct inode *inode,
                       u64 start, u64 end, u64 *hint_byte, int drop_cache)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_buffer *leaf;
        struct btrfs_file_extent_item *fi;
        struct btrfs_path *path;
        struct btrfs_key key;
        struct btrfs_key new_key;
        u64 ino = btrfs_ino(inode);
        u64 search_start = start;
        u64 disk_bytenr = 0;
        u64 num_bytes = 0;
        u64 extent_offset = 0;
        u64 extent_end = 0;
        int del_nr = 0;
        int del_slot = 0;
        int extent_type;
        int recow;
        int ret;

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

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;

        while (1) {
                recow = 0;
                ret = btrfs_lookup_file_extent(trans, root, path, ino,
                                               search_start, -1);
                if (ret < 0)
                        break;
                if (ret > 0 && path->slots[0] > 0 && search_start == start) {
                        leaf = path->nodes[0];
                        btrfs_item_key_to_cpu(leaf, &key, path->slots[0] - 1);
                        if (key.objectid == ino &&
                            key.type == BTRFS_EXTENT_DATA_KEY)
                                path->slots[0]--;
                }
                ret = 0;
next_slot:
                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
                        BUG_ON(del_nr > 0);
                        ret = btrfs_next_leaf(root, path);
                        if (ret < 0)
                                break;
                        if (ret > 0) {
                                ret = 0;
                                break;
                        }
                        leaf = path->nodes[0];
                        recow = 1;
                }

                btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
                if (key.objectid > ino ||
                    key.type > BTRFS_EXTENT_DATA_KEY || key.offset >= end)
                        break;

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);
                extent_type = btrfs_file_extent_type(leaf, fi);

                if (extent_type == BTRFS_FILE_EXTENT_REG ||
                    extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
                        num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
                        extent_offset = btrfs_file_extent_offset(leaf, fi);
                        extent_end = key.offset +
                                btrfs_file_extent_num_bytes(leaf, fi);
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        extent_end = key.offset +
                                btrfs_file_extent_inline_len(leaf, fi);
                } else {
                        WARN_ON(1);
                        extent_end = search_start;
                }

                if (extent_end <= search_start) {
                        path->slots[0]++;
                        goto next_slot;
                }

                search_start = max(key.offset, start);
                if (recow) {
                        btrfs_release_path(path);
                        continue;
                }

                /*
                 *     | - range to drop - |
                 *  | -------- extent -------- |
                 */
                if (start > key.offset && end < extent_end) {
                        BUG_ON(del_nr > 0);
                        BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);

                        memcpy(&new_key, &key, sizeof(new_key));
                        new_key.offset = start;
                        ret = btrfs_duplicate_item(trans, root, path,
                                                   &new_key);
                        if (ret == -EAGAIN) {
                                btrfs_release_path(path);
                                continue;
                        }
                        if (ret < 0)
                                break;

                        leaf = path->nodes[0];
                        fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        start - key.offset);

                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);

                        extent_offset += start - key.offset;
                        btrfs_set_file_extent_offset(leaf, fi, extent_offset);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        extent_end - start);
                        btrfs_mark_buffer_dirty(leaf);

                        if (disk_bytenr > 0) {
                                ret = btrfs_inc_extent_ref(trans, root,
                                                disk_bytenr, num_bytes, 0,
                                                root->root_key.objectid,
                                                new_key.objectid,
                                                start - extent_offset);
                                BUG_ON(ret);
                                *hint_byte = disk_bytenr;
                        }
                        key.offset = start;
                }
                /*
                 *  | ---- range to drop ----- |
                 *      | -------- extent -------- |
                 */
                if (start <= key.offset && end < extent_end) {
                        BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);

                        memcpy(&new_key, &key, sizeof(new_key));
                        new_key.offset = end;
                        btrfs_set_item_key_safe(trans, root, path, &new_key);

                        extent_offset += end - key.offset;
                        btrfs_set_file_extent_offset(leaf, fi, extent_offset);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        extent_end - end);
                        btrfs_mark_buffer_dirty(leaf);
                        if (disk_bytenr > 0) {
                                inode_sub_bytes(inode, end - key.offset);
                                *hint_byte = disk_bytenr;
                        }
                        break;
                }

                search_start = extent_end;
                /*
                 *       | ---- range to drop ----- |
                 *  | -------- extent -------- |
                 */
                if (start > key.offset && end >= extent_end) {
                        BUG_ON(del_nr > 0);
                        BUG_ON(extent_type == BTRFS_FILE_EXTENT_INLINE);

                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        start - key.offset);
                        btrfs_mark_buffer_dirty(leaf);
                        if (disk_bytenr > 0) {
                                inode_sub_bytes(inode, extent_end - start);
                                *hint_byte = disk_bytenr;
                        }
                        if (end == extent_end)
                                break;

                        path->slots[0]++;
                        goto next_slot;
                }

                /*
                 *  | ---- range to drop ----- |
                 *    | ------ extent ------ |
                 */
                if (start <= key.offset && end >= extent_end) {
                        if (del_nr == 0) {
                                del_slot = path->slots[0];
                                del_nr = 1;
                        } else {
                                BUG_ON(del_slot + del_nr != path->slots[0]);
                                del_nr++;
                        }

                        if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                                inode_sub_bytes(inode,
                                                extent_end - key.offset);
                                extent_end = ALIGN(extent_end,
                                                   root->sectorsize);
                        } else if (disk_bytenr > 0) {
                                ret = btrfs_free_extent(trans, root,
                                                disk_bytenr, num_bytes, 0,
                                                root->root_key.objectid,
                                                key.objectid, key.offset -
                                                extent_offset);
                                BUG_ON(ret);
                                inode_sub_bytes(inode,
                                                extent_end - key.offset);
                                *hint_byte = disk_bytenr;
                        }

                        if (end == extent_end)
                                break;

                        if (path->slots[0] + 1 < btrfs_header_nritems(leaf)) {
                                path->slots[0]++;
                                goto next_slot;
                        }

                        ret = btrfs_del_items(trans, root, path, del_slot,
                                              del_nr);
                        BUG_ON(ret);

                        del_nr = 0;
                        del_slot = 0;

                        btrfs_release_path(path);
                        continue;
                }

                BUG_ON(1);
        }

        if (del_nr > 0) {
                ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
                BUG_ON(ret);
        }

        btrfs_free_path(path);
        return ret;
}

static int extent_mergeable(struct extent_buffer *leaf, int slot,
                            u64 objectid, u64 bytenr, u64 orig_offset,
                            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_offset(leaf, fi) != key.offset - orig_offset ||
            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 inode *inode, u64 start, u64 end)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_buffer *leaf;
        struct btrfs_path *path;
        struct btrfs_file_extent_item *fi;
        struct btrfs_key key;
        struct btrfs_key new_key;
        u64 bytenr;
        u64 num_bytes;
        u64 extent_end;
        u64 orig_offset;
        u64 other_start;
        u64 other_end;
        u64 split;
        int del_nr = 0;
        int del_slot = 0;
        int recow;
        int ret;
        u64 ino = btrfs_ino(inode);

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

        path = btrfs_alloc_path();
        if (!path)
                return -ENOMEM;
again:
        recow = 0;
        split = start;
        key.objectid = ino;
        key.type = BTRFS_EXTENT_DATA_KEY;
        key.offset = split;

        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
        if (ret < 0)
                goto out;
        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 != ino || key.type != BTRFS_EXTENT_DATA_KEY);
        fi = btrfs_item_ptr(leaf, path->slots[0],
                            struct btrfs_file_extent_item);
        BUG_ON(btrfs_file_extent_type(leaf, fi) !=
               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);
        memcpy(&new_key, &key, sizeof(new_key));

        if (start == key.offset && end < extent_end) {
                other_start = 0;
                other_end = start;
                if (extent_mergeable(leaf, path->slots[0] - 1,
                                     ino, bytenr, orig_offset,
                                     &other_start, &other_end)) {
                        new_key.offset = end;
                        btrfs_set_item_key_safe(trans, root, path, &new_key);
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        extent_end - end);
                        btrfs_set_file_extent_offset(leaf, fi,
                                                     end - orig_offset);
                        fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        end - other_start);
                        btrfs_mark_buffer_dirty(leaf);
                        goto out;
                }
        }

        if (start > key.offset && end == extent_end) {
                other_start = end;
                other_end = 0;
                if (extent_mergeable(leaf, path->slots[0] + 1,
                                     ino, bytenr, orig_offset,
                                     &other_start, &other_end)) {
                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        start - key.offset);
                        path->slots[0]++;
                        new_key.offset = start;
                        btrfs_set_item_key_safe(trans, root, path, &new_key);

                        fi = btrfs_item_ptr(leaf, path->slots[0],
                                            struct btrfs_file_extent_item);
                        btrfs_set_file_extent_num_bytes(leaf, fi,
                                                        other_end - start);
                        btrfs_set_file_extent_offset(leaf, fi,
                                                     start - orig_offset);
                        btrfs_mark_buffer_dirty(leaf);
                        goto out;
                }
        }

        while (start > key.offset || end < extent_end) {
                if (key.offset == start)
                        split = end;

                new_key.offset = split;
                ret = btrfs_duplicate_item(trans, root, path, &new_key);
                if (ret == -EAGAIN) {
                        btrfs_release_path(path);
                        goto again;
                }
                BUG_ON(ret < 0);

                leaf = path->nodes[0];
                fi = btrfs_item_ptr(leaf, path->slots[0] - 1,
                                    struct btrfs_file_extent_item);
                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                split - key.offset);

                fi = btrfs_item_ptr(leaf, path->slots[0],
                                    struct btrfs_file_extent_item);

                btrfs_set_file_extent_offset(leaf, fi, split - orig_offset);
                btrfs_set_file_extent_num_bytes(leaf, fi,
                                                extent_end - split);
                btrfs_mark_buffer_dirty(leaf);

                ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes, 0,
                                           root->root_key.objectid,
                                           ino, orig_offset);
                BUG_ON(ret);

                if (split == start) {
                        key.offset = start;
                } else {
                        BUG_ON(start != key.offset);
                        path->slots[0]--;
                        extent_end = end;
                }
                recow = 1;
        }

        other_start = end;
        other_end = 0;
        if (extent_mergeable(leaf, path->slots[0] + 1,
                             ino, bytenr, orig_offset,
                             &other_start, &other_end)) {
                if (recow) {
                        btrfs_release_path(path);
                        goto again;
                }
                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,
                                        ino, orig_offset);
                BUG_ON(ret);
        }
        other_start = 0;
        other_end = start;
        if (extent_mergeable(leaf, path->slots[0] - 1,
                             ino, bytenr, orig_offset,
                             &other_start, &other_end)) {
                if (recow) {

                        btrfs_release_path(path);
                        goto again;
                }
                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,
                                        ino, orig_offset);
                BUG_ON(ret);
        }
        if (del_nr == 0) {
                fi = btrfs_item_ptr(leaf, path->slots[0],
                           struct btrfs_file_extent_item);
                btrfs_set_file_extent_type(leaf, fi,
                                           BTRFS_FILE_EXTENT_REG);
                btrfs_mark_buffer_dirty(leaf);
        } else {
                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);
        }
out:
        btrfs_free_path(path);
        return 0;
}

/*
 * on error we return an unlocked page and the error value
 * on success we return a locked page and 0
 */
static int prepare_uptodate_page(struct page *page, u64 pos,
                                 bool force_uptodate)
{
        int ret = 0;

        if (((pos & (PAGE_CACHE_SIZE - 1)) || force_uptodate) &&
            !PageUptodate(page)) {
                ret = btrfs_readpage(NULL, page);
                if (ret)
                        return ret;
                lock_page(page);
                if (!PageUptodate(page)) {
                        unlock_page(page);
                        return -EIO;
                }
        }
        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,
                         size_t write_bytes, bool force_uptodate)
{
        struct extent_state *cached_state = NULL;
        int i;
        unsigned long index = pos >> PAGE_CACHE_SHIFT;
        struct inode *inode = fdentry(file)->d_inode;
        gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
        int err = 0;
        int faili = 0;
        u64 start_pos;
        u64 last_pos;

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

again:
        for (i = 0; i < num_pages; i++) {
                pages[i] = find_or_create_page(inode->i_mapping, index + i,
                                               mask);
                if (!pages[i]) {
                        faili = i - 1;
                        err = -ENOMEM;
                        goto fail;
                }

                if (i == 0)
                        err = prepare_uptodate_page(pages[i], pos,
                                                    force_uptodate);
                if (i == num_pages - 1)
                        err = prepare_uptodate_page(pages[i],
                                                    pos + write_bytes, false);
                if (err) {
                        page_cache_release(pages[i]);
                        faili = i - 1;
                        goto fail;
                }
                wait_on_page_writeback(pages[i]);
        }
        err = 0;
        if (start_pos < inode->i_size) {
                struct btrfs_ordered_extent *ordered;
                lock_extent_bits(&BTRFS_I(inode)->io_tree,
                                 start_pos, last_pos - 1, 0, &cached_state,
                                 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_cached(&BTRFS_I(inode)->io_tree,
                                             start_pos, last_pos - 1,
                                             &cached_state, 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_bit(&BTRFS_I(inode)->io_tree, start_pos,
                                  last_pos - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
                                  EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,
                                  GFP_NOFS);
                unlock_extent_cached(&BTRFS_I(inode)->io_tree,
                                     start_pos, last_pos - 1, &cached_state,
                                     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;
fail:
        while (faili >= 0) {
                unlock_page(pages[faili]);
                page_cache_release(pages[faili]);
                faili--;
        }
        return err;

}

static noinline ssize_t __btrfs_buffered_write(struct file *file,
                                               struct iov_iter *i,
                                               loff_t pos)
{
        struct inode *inode = fdentry(file)->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct page **pages = NULL;
        unsigned long first_index;
        size_t num_written = 0;
        int nrptrs;
        int ret = 0;
        bool force_page_uptodate = false;

        nrptrs = min((iov_iter_count(i) + PAGE_CACHE_SIZE - 1) /
                     PAGE_CACHE_SIZE, PAGE_CACHE_SIZE /
                     (sizeof(struct page *)));
        nrptrs = min(nrptrs, current->nr_dirtied_pause - current->nr_dirtied);
        nrptrs = max(nrptrs, 8);
        pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
        if (!pages)
                return -ENOMEM;

        first_index = pos >> PAGE_CACHE_SHIFT;

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

                WARN_ON(num_pages > nrptrs);

                /*
                 * Fault pages before locking them in prepare_pages
                 * to avoid recursive lock
                 */
                if (unlikely(iov_iter_fault_in_readable(i, write_bytes))) {
                        ret = -EFAULT;
                        break;
                }

                ret = btrfs_delalloc_reserve_space(inode,
                                        num_pages << PAGE_CACHE_SHIFT);
                if (ret)
                        break;

                /*
                 * This is going to setup the pages array with the number of
                 * pages we want, so we don't really need to worry about the
                 * contents of pages from loop to loop
                 */
                ret = prepare_pages(root, file, pages, num_pages,
                                    pos, first_index, write_bytes,
                                    force_page_uptodate);
                if (ret) {
                        btrfs_delalloc_release_space(inode,
                                        num_pages << PAGE_CACHE_SHIFT);
                        break;
                }

                copied = btrfs_copy_from_user(pos, num_pages,
                                           write_bytes, pages, i);

                /*
                 * if we have trouble faulting in the pages, fall
                 * back to one page at a time
                 */
                if (copied < write_bytes)
                        nrptrs = 1;

                if (copied == 0) {
                        force_page_uptodate = true;
                        dirty_pages = 0;
                } else {
                        force_page_uptodate = false;
                        dirty_pages = (copied + offset +
                                       PAGE_CACHE_SIZE - 1) >>
                                       PAGE_CACHE_SHIFT;
                }

                /*
                 * If we had a short copy we need to release the excess delaloc
                 * bytes we reserved.  We need to increment outstanding_extents
                 * because btrfs_delalloc_release_space will decrement it, but
                 * we still have an outstanding extent for the chunk we actually
                 * managed to copy.
                 */
                if (num_pages > dirty_pages) {
                        if (copied > 0) {
                                spin_lock(&BTRFS_I(inode)->lock);
                                BTRFS_I(inode)->outstanding_extents++;
                                spin_unlock(&BTRFS_I(inode)->lock);
                        }
                        btrfs_delalloc_release_space(inode,
                                        (num_pages - dirty_pages) <<
                                        PAGE_CACHE_SHIFT);
                }

                if (copied > 0) {
                        ret = btrfs_dirty_pages(root, inode, pages,
                                                dirty_pages, pos, copied,
                                                NULL);
                        if (ret) {
                                btrfs_delalloc_release_space(inode,
                                        dirty_pages << PAGE_CACHE_SHIFT);
                                btrfs_drop_pages(pages, num_pages);
                                break;
                        }
                }

                btrfs_drop_pages(pages, num_pages);

                cond_resched();

                balance_dirty_pages_ratelimited_nr(inode->i_mapping,
                                                   dirty_pages);
                if (dirty_pages < (root->leafsize >> PAGE_CACHE_SHIFT) + 1)
                        btrfs_btree_balance_dirty(root, 1);
                btrfs_throttle(root);

                pos += copied;
                num_written += copied;
        }

        kfree(pages);

        return num_written ? num_written : ret;
}

static ssize_t __btrfs_direct_write(struct kiocb *iocb,
                                    const struct iovec *iov,
                                    unsigned long nr_segs, loff_t pos,
                                    loff_t *ppos, size_t count, size_t ocount)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = fdentry(file)->d_inode;
        struct iov_iter i;
        ssize_t written;
        ssize_t written_buffered;
        loff_t endbyte;
        int err;

        written = generic_file_direct_write(iocb, iov, &nr_segs, pos, ppos,
                                            count, ocount);

        /*
         * the generic O_DIRECT will update in-memory i_size after the
         * DIOs are done.  But our endio handlers that update the on
         * disk i_size never update past the in memory i_size.  So we
         * need one more update here to catch any additions to the
         * file
         */
        if (inode->i_size != BTRFS_I(inode)->disk_i_size) {
                btrfs_ordered_update_i_size(inode, inode->i_size, NULL);
                mark_inode_dirty(inode);
        }

        if (written < 0 || written == count)
                return written;

        pos += written;
        count -= written;
        iov_iter_init(&i, iov, nr_segs, count, written);
        written_buffered = __btrfs_buffered_write(file, &i, pos);
        if (written_buffered < 0) {
                err = written_buffered;
                goto out;
        }
        endbyte = pos + written_buffered - 1;
        err = filemap_write_and_wait_range(file->f_mapping, pos, endbyte);
        if (err)
                goto out;
        written += written_buffered;
        *ppos = pos + written_buffered;
        invalidate_mapping_pages(file->f_mapping, pos >> PAGE_CACHE_SHIFT,
                                 endbyte >> PAGE_CACHE_SHIFT);
out:
        return written ? written : err;
}

static ssize_t btrfs_file_aio_write(struct kiocb *iocb,
                                    const struct iovec *iov,
                                    unsigned long nr_segs, loff_t pos)
{
        struct file *file = iocb->ki_filp;
        struct inode *inode = fdentry(file)->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        loff_t *ppos = &iocb->ki_pos;
        u64 start_pos;
        ssize_t num_written = 0;
        ssize_t err = 0;
        size_t count, ocount;

        vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);

        mutex_lock(&inode->i_mutex);

        err = generic_segment_checks(iov, &nr_segs, &ocount, VERIFY_READ);
        if (err) {
                mutex_unlock(&inode->i_mutex);
                goto out;
        }
        count = ocount;

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

        if (count == 0) {
                mutex_unlock(&inode->i_mutex);
                goto out;
        }

        err = file_remove_suid(file);
        if (err) {
                mutex_unlock(&inode->i_mutex);
                goto out;
        }

        /*
         * If BTRFS flips readonly due to some impossible error
         * (fs_info->fs_state now has BTRFS_SUPER_FLAG_ERROR),
         * although we have opened a file as writable, we have
         * to stop this write operation to ensure FS consistency.
         */
        if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR) {
                mutex_unlock(&inode->i_mutex);
                err = -EROFS;
                goto out;
        }

        err = btrfs_update_time(file);
        if (err) {
                mutex_unlock(&inode->i_mutex);
                goto out;
        }
        BTRFS_I(inode)->sequence++;

        start_pos = round_down(pos, root->sectorsize);
        if (start_pos > i_size_read(inode)) {
                err = btrfs_cont_expand(inode, i_size_read(inode), start_pos);
                if (err) {
                        mutex_unlock(&inode->i_mutex);
                        goto out;
                }
        }

        if (unlikely(file->f_flags & O_DIRECT)) {
                num_written = __btrfs_direct_write(iocb, iov, nr_segs,
                                                   pos, ppos, count, ocount);
        } else {
                struct iov_iter i;

                iov_iter_init(&i, iov, nr_segs, count, num_written);

                num_written = __btrfs_buffered_write(file, &i, pos);
                if (num_written > 0)
                        *ppos = pos + num_written;
        }

        mutex_unlock(&inode->i_mutex);

        /*
         * 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 || num_written == -EIOCBQUEUED) {
                err = generic_write_sync(file, pos, num_written);
                if (err < 0 && num_written > 0)
                        num_written = err;
        }
out:
        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, loff_t start, loff_t end, int datasync)
{
        struct dentry *dentry = file->f_path.dentry;
        struct inode *inode = dentry->d_inode;
        struct btrfs_root *root = BTRFS_I(inode)->root;
        int ret = 0;
        struct btrfs_trans_handle *trans;

        trace_btrfs_sync_file(file, datasync);

        ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
        if (ret)
                return ret;
        mutex_lock(&inode->i_mutex);

        /* we wait first, since the writeback may change the inode */
        root->log_batch++;
        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) {
                mutex_unlock(&inode->i_mutex);
                goto out;
        }

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

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

        trans = btrfs_start_transaction(root, 0);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
                mutex_unlock(&inode->i_mutex);
                goto out;
        }

        ret = btrfs_log_dentry_safe(trans, root, dentry);
        if (ret < 0) {
                mutex_unlock(&inode->i_mutex);
                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(&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);
        }
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)
{
        struct address_space *mapping = filp->f_mapping;

        if (!mapping->a_ops->readpage)
                return -ENOEXEC;

        file_accessed(filp);
        vma->vm_ops = &btrfs_file_vm_ops;
        vma->vm_flags |= VM_CAN_NONLINEAR;

        return 0;
}

static long btrfs_fallocate(struct file *file, int mode,
                            loff_t offset, loff_t len)
{
        struct inode *inode = file->f_path.dentry->d_inode;
        struct extent_state *cached_state = NULL;
        u64 cur_offset;
        u64 last_byte;
        u64 alloc_start;
        u64 alloc_end;
        u64 alloc_hint = 0;
        u64 locked_end;
        u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
        struct extent_map *em;
        int ret;

        alloc_start = offset & ~mask;
        alloc_end =  (offset + len + mask) & ~mask;

        /* We only support the FALLOC_FL_KEEP_SIZE mode */
        if (mode & ~FALLOC_FL_KEEP_SIZE)
                return -EOPNOTSUPP;

        /*
         * wait for ordered IO before we have any locks.  We'll loop again
         * below with the locks held.
         */
        btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);

        mutex_lock(&inode->i_mutex);
        ret = inode_newsize_ok(inode, alloc_end);
        if (ret)
                goto out;

        if (alloc_start > inode->i_size) {
                ret = btrfs_cont_expand(inode, i_size_read(inode),
                                        alloc_start);
                if (ret)
                        goto out;
        }

        locked_end = alloc_end - 1;
        while (1) {
                struct btrfs_ordered_extent *ordered;

                /* the extent lock is ordered inside the running
                 * transaction
                 */
                lock_extent_bits(&BTRFS_I(inode)->io_tree, alloc_start,
                                 locked_end, 0, &cached_state, GFP_NOFS);
                ordered = btrfs_lookup_first_ordered_extent(inode,
                                                            alloc_end - 1);
                if (ordered &&
                    ordered->file_offset + ordered->len > alloc_start &&
                    ordered->file_offset < alloc_end) {
                        btrfs_put_ordered_extent(ordered);
                        unlock_extent_cached(&BTRFS_I(inode)->io_tree,
                                             alloc_start, locked_end,
                                             &cached_state, GFP_NOFS);
                        /*
                         * we can't wait on the range with the transaction
                         * running or with the extent lock held
                         */
                        btrfs_wait_ordered_range(inode, alloc_start,
                                                 alloc_end - alloc_start);
                } else {
                        if (ordered)
                                btrfs_put_ordered_extent(ordered);
                        break;
                }
        }

        cur_offset = alloc_start;
        while (1) {
                u64 actual_end;

                em = btrfs_get_extent(inode, NULL, 0, cur_offset,
                                      alloc_end - cur_offset, 0);
                BUG_ON(IS_ERR_OR_NULL(em));
                last_byte = min(extent_map_end(em), alloc_end);
                actual_end = min_t(u64, extent_map_end(em), offset + len);
                last_byte = (last_byte + mask) & ~mask;

                if (em->block_start == EXTENT_MAP_HOLE ||
                    (cur_offset >= inode->i_size &&
                     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {

                        /*
                         * Make sure we have enough space before we do the
                         * allocation.
                         */
                        ret = btrfs_check_data_free_space(inode, last_byte -
                                                          cur_offset);
                        if (ret) {
                                free_extent_map(em);
                                break;
                        }

                        ret = btrfs_prealloc_file_range(inode, mode, cur_offset,
                                                        last_byte - cur_offset,
                                                        1 << inode->i_blkbits,
                                                        offset + len,
                                                        &alloc_hint);

                        /* Let go of our reservation. */
                        btrfs_free_reserved_data_space(inode, last_byte -
                                                       cur_offset);
                        if (ret < 0) {
                                free_extent_map(em);
                                break;
                        }
                } else if (actual_end > inode->i_size &&
                           !(mode & FALLOC_FL_KEEP_SIZE)) {
                        /*
                         * We didn't need to allocate any more space, but we
                         * still extended the size of the file so we need to
                         * update i_size.
                         */
                        inode->i_ctime = CURRENT_TIME;
                        i_size_write(inode, actual_end);
                        btrfs_ordered_update_i_size(inode, actual_end, NULL);
                }
                free_extent_map(em);

                cur_offset = last_byte;
                if (cur_offset >= alloc_end) {
                        ret = 0;
                        break;
                }
        }
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
                             &cached_state, GFP_NOFS);
out:
        mutex_unlock(&inode->i_mutex);
        return ret;
}

static int find_desired_extent(struct inode *inode, loff_t *offset, int origin)
{
        struct btrfs_root *root = BTRFS_I(inode)->root;
        struct extent_map *em;
        struct extent_state *cached_state = NULL;
        u64 lockstart = *offset;
        u64 lockend = i_size_read(inode);
        u64 start = *offset;
        u64 orig_start = *offset;
        u64 len = i_size_read(inode);
        u64 last_end = 0;
        int ret = 0;

        lockend = max_t(u64, root->sectorsize, lockend);
        if (lockend <= lockstart)
                lockend = lockstart + root->sectorsize;

        len = lockend - lockstart + 1;

        len = max_t(u64, len, root->sectorsize);
        if (inode->i_size == 0)
                return -ENXIO;

        lock_extent_bits(&BTRFS_I(inode)->io_tree, lockstart, lockend, 0,
                         &cached_state, GFP_NOFS);

        /*
         * Delalloc is such a pain.  If we have a hole and we have pending
         * delalloc for a portion of the hole we will get back a hole that
         * exists for the entire range since it hasn't been actually written
         * yet.  So to take care of this case we need to look for an extent just
         * before the position we want in case there is outstanding delalloc
         * going on here.
         */
        if (origin == SEEK_HOLE && start != 0) {
                if (start <= root->sectorsize)
                        em = btrfs_get_extent_fiemap(inode, NULL, 0, 0,
                                                     root->sectorsize, 0);
                else
                        em = btrfs_get_extent_fiemap(inode, NULL, 0,
                                                     start - root->sectorsize,
                                                     root->sectorsize, 0);
                if (IS_ERR(em)) {
                        ret = -ENXIO;
                        goto out;
                }
                last_end = em->start + em->len;
                if (em->block_start == EXTENT_MAP_DELALLOC)
                        last_end = min_t(u64, last_end, inode->i_size);
                free_extent_map(em);
        }

        while (1) {
                em = btrfs_get_extent_fiemap(inode, NULL, 0, start, len, 0);
                if (IS_ERR(em)) {
                        ret = -ENXIO;
                        break;
                }

                if (em->block_start == EXTENT_MAP_HOLE) {
                        if (test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
                                if (last_end <= orig_start) {
                                        free_extent_map(em);
                                        ret = -ENXIO;
                                        break;
                                }
                        }

                        if (origin == SEEK_HOLE) {
                                *offset = start;
                                free_extent_map(em);
                                break;
                        }
                } else {
                        if (origin == SEEK_DATA) {
                                if (em->block_start == EXTENT_MAP_DELALLOC) {
                                        if (start >= inode->i_size) {
                                                free_extent_map(em);
                                                ret = -ENXIO;
                                                break;
                                        }
                                }

                                *offset = start;
                                free_extent_map(em);
                                break;
                        }
                }

                start = em->start + em->len;
                last_end = em->start + em->len;

                if (em->block_start == EXTENT_MAP_DELALLOC)
                        last_end = min_t(u64, last_end, inode->i_size);

                if (test_bit(EXTENT_FLAG_VACANCY, &em->flags)) {
                        free_extent_map(em);
                        ret = -ENXIO;
                        break;
                }
                free_extent_map(em);
                cond_resched();
        }
        if (!ret)
                *offset = min(*offset, inode->i_size);
out:
        unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,
                             &cached_state, GFP_NOFS);
        return ret;
}

static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int origin)
{
        struct inode *inode = file->f_mapping->host;
        int ret;

        mutex_lock(&inode->i_mutex);
        switch (origin) {
        case SEEK_END:
        case SEEK_CUR:
                offset = generic_file_llseek(file, offset, origin);
                goto out;
        case SEEK_DATA:
        case SEEK_HOLE:
                if (offset >= i_size_read(inode)) {
                        mutex_unlock(&inode->i_mutex);
                        return -ENXIO;
                }

                ret = find_desired_extent(inode, &offset, origin);
                if (ret) {
                        mutex_unlock(&inode->i_mutex);
                        return ret;
                }
        }

        if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
                offset = -EINVAL;
                goto out;
        }
        if (offset > inode->i_sb->s_maxbytes) {
                offset = -EINVAL;
                goto out;
        }

        /* Special lock needed here? */
        if (offset != file->f_pos) {
                file->f_pos = offset;
                file->f_version = 0;
        }
out:
        mutex_unlock(&inode->i_mutex);
        return offset;
}

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