aops.c

Go to the documentation of this file.

/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * Copyright (C) 2002, 2004 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 as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * 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/slab.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <asm/byteorder.h>
#include <linux/swap.h>
#include <linux/pipe_fs_i.h>
#include <linux/mpage.h>
#include <linux/quotaops.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "alloc.h"
#include "aops.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "file.h"
#include "inode.h"
#include "journal.h"
#include "suballoc.h"
#include "super.h"
#include "symlink.h"
#include "refcounttree.h"
#include "ocfs2_trace.h"

#include "buffer_head_io.h"

static int ocfs2_symlink_get_block(struct inode *inode, sector_t iblock,
                   struct buffer_head *bh_result, int create)
{
    int err = -EIO;
    int status;
    struct ocfs2_dinode *fe = NULL;
    struct buffer_head *bh = NULL;
    struct buffer_head *buffer_cache_bh = NULL;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    void *kaddr;

    trace_ocfs2_symlink_get_block(
            (unsigned long long)OCFS2_I(inode)->ip_blkno,
            (unsigned long long)iblock, bh_result, create);

    BUG_ON(ocfs2_inode_is_fast_symlink(inode));

    if ((iblock << inode->i_sb->s_blocksize_bits) > PATH_MAX + 1) {
        mlog(ML_ERROR, "block offset > PATH_MAX: %llu",
             (unsigned long long)iblock);
        goto bail;
    }

    status = ocfs2_read_inode_block(inode, &bh);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }
    fe = (struct ocfs2_dinode *) bh->b_data;

    if ((u64)iblock >= ocfs2_clusters_to_blocks(inode->i_sb,
                            le32_to_cpu(fe->i_clusters))) {
        mlog(ML_ERROR, "block offset is outside the allocated size: "
             "%llu\n", (unsigned long long)iblock);
        goto bail;
    }

    /* We don't use the page cache to create symlink data, so if
     * need be, copy it over from the buffer cache. */
    if (!buffer_uptodate(bh_result) && ocfs2_inode_is_new(inode)) {
        u64 blkno = le64_to_cpu(fe->id2.i_list.l_recs[0].e_blkno) +
                iblock;
        buffer_cache_bh = sb_getblk(osb->sb, blkno);
        if (!buffer_cache_bh) {
            mlog(ML_ERROR, "couldn't getblock for symlink!\n");
            goto bail;
        }

        /* we haven't locked out transactions, so a commit
         * could've happened. Since we've got a reference on
         * the bh, even if it commits while we're doing the
         * copy, the data is still good. */
        if (buffer_jbd(buffer_cache_bh)
            && ocfs2_inode_is_new(inode)) {
            kaddr = kmap_atomic(bh_result->b_page);
            if (!kaddr) {
                mlog(ML_ERROR, "couldn't kmap!\n");
                goto bail;
            }
            memcpy(kaddr + (bh_result->b_size * iblock),
                   buffer_cache_bh->b_data,
                   bh_result->b_size);
            kunmap_atomic(kaddr);
            set_buffer_uptodate(bh_result);
        }
        brelse(buffer_cache_bh);
    }

    map_bh(bh_result, inode->i_sb,
           le64_to_cpu(fe->id2.i_list.l_recs[0].e_blkno) + iblock);

    err = 0;

bail:
    brelse(bh);

    return err;
}

int ocfs2_get_block(struct inode *inode, sector_t iblock,
            struct buffer_head *bh_result, int create)
{
    int err = 0;
    unsigned int ext_flags;
    u64 max_blocks = bh_result->b_size >> inode->i_blkbits;
    u64 p_blkno, count, past_eof;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    trace_ocfs2_get_block((unsigned long long)OCFS2_I(inode)->ip_blkno,
                  (unsigned long long)iblock, bh_result, create);

    if (OCFS2_I(inode)->ip_flags & OCFS2_INODE_SYSTEM_FILE)
        mlog(ML_NOTICE, "get_block on system inode 0x%p (%lu)\n",
             inode, inode->i_ino);

    if (S_ISLNK(inode->i_mode)) {
        /* this always does I/O for some reason. */
        err = ocfs2_symlink_get_block(inode, iblock, bh_result, create);
        goto bail;
    }

    err = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno, &count,
                      &ext_flags);
    if (err) {
        mlog(ML_ERROR, "Error %d from get_blocks(0x%p, %llu, 1, "
             "%llu, NULL)\n", err, inode, (unsigned long long)iblock,
             (unsigned long long)p_blkno);
        goto bail;
    }

    if (max_blocks < count)
        count = max_blocks;

    /*
     * ocfs2 never allocates in this function - the only time we
     * need to use BH_New is when we're extending i_size on a file
     * system which doesn't support holes, in which case BH_New
     * allows __block_write_begin() to zero.
     *
     * If we see this on a sparse file system, then a truncate has
     * raced us and removed the cluster. In this case, we clear
     * the buffers dirty and uptodate bits and let the buffer code
     * ignore it as a hole.
     */
    if (create && p_blkno == 0 && ocfs2_sparse_alloc(osb)) {
        clear_buffer_dirty(bh_result);
        clear_buffer_uptodate(bh_result);
        goto bail;
    }

    /* Treat the unwritten extent as a hole for zeroing purposes. */
    if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
        map_bh(bh_result, inode->i_sb, p_blkno);

    bh_result->b_size = count << inode->i_blkbits;

    if (!ocfs2_sparse_alloc(osb)) {
        if (p_blkno == 0) {
            err = -EIO;
            mlog(ML_ERROR,
                 "iblock = %llu p_blkno = %llu blkno=(%llu)\n",
                 (unsigned long long)iblock,
                 (unsigned long long)p_blkno,
                 (unsigned long long)OCFS2_I(inode)->ip_blkno);
            mlog(ML_ERROR, "Size %llu, clusters %u\n", (unsigned long long)i_size_read(inode), OCFS2_I(inode)->ip_clusters);
            dump_stack();
            goto bail;
        }
    }

    past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));

    trace_ocfs2_get_block_end((unsigned long long)OCFS2_I(inode)->ip_blkno,
                  (unsigned long long)past_eof);
    if (create && (iblock >= past_eof))
        set_buffer_new(bh_result);

bail:
    if (err < 0)
        err = -EIO;

    return err;
}

int ocfs2_read_inline_data(struct inode *inode, struct page *page,
               struct buffer_head *di_bh)
{
    void *kaddr;
    loff_t size;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;

    if (!(le16_to_cpu(di->i_dyn_features) & OCFS2_INLINE_DATA_FL)) {
        ocfs2_error(inode->i_sb, "Inode %llu lost inline data flag",
                (unsigned long long)OCFS2_I(inode)->ip_blkno);
        return -EROFS;
    }

    size = i_size_read(inode);

    if (size > PAGE_CACHE_SIZE ||
        size > ocfs2_max_inline_data_with_xattr(inode->i_sb, di)) {
        ocfs2_error(inode->i_sb,
                "Inode %llu has with inline data has bad size: %Lu",
                (unsigned long long)OCFS2_I(inode)->ip_blkno,
                (unsigned long long)size);
        return -EROFS;
    }

    kaddr = kmap_atomic(page);
    if (size)
        memcpy(kaddr, di->id2.i_data.id_data, size);
    /* Clear the remaining part of the page */
    memset(kaddr + size, 0, PAGE_CACHE_SIZE - size);
    flush_dcache_page(page);
    kunmap_atomic(kaddr);

    SetPageUptodate(page);

    return 0;
}

static int ocfs2_readpage_inline(struct inode *inode, struct page *page)
{
    int ret;
    struct buffer_head *di_bh = NULL;

    BUG_ON(!PageLocked(page));
    BUG_ON(!(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL));

    ret = ocfs2_read_inode_block(inode, &di_bh);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_read_inline_data(inode, page, di_bh);
out:
    unlock_page(page);

    brelse(di_bh);
    return ret;
}

static int ocfs2_readpage(struct file *file, struct page *page)
{
    struct inode *inode = page->mapping->host;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    loff_t start = (loff_t)page->index << PAGE_CACHE_SHIFT;
    int ret, unlock = 1;

    trace_ocfs2_readpage((unsigned long long)oi->ip_blkno,
                 (page ? page->index : 0));

    ret = ocfs2_inode_lock_with_page(inode, NULL, 0, page);
    if (ret != 0) {
        if (ret == AOP_TRUNCATED_PAGE)
            unlock = 0;
        mlog_errno(ret);
        goto out;
    }

    if (down_read_trylock(&oi->ip_alloc_sem) == 0) {
        /*
         * Unlock the page and cycle ip_alloc_sem so that we don't
         * busyloop waiting for ip_alloc_sem to unlock
         */
        ret = AOP_TRUNCATED_PAGE;
        unlock_page(page);
        unlock = 0;
        down_read(&oi->ip_alloc_sem);
        up_read(&oi->ip_alloc_sem);
        goto out_inode_unlock;
    }

    /*
     * i_size might have just been updated as we grabed the meta lock.  We
     * might now be discovering a truncate that hit on another node.
     * block_read_full_page->get_block freaks out if it is asked to read
     * beyond the end of a file, so we check here.  Callers
     * (generic_file_read, vm_ops->fault) are clever enough to check i_size
     * and notice that the page they just read isn't needed.
     *
     * XXX sys_readahead() seems to get that wrong?
     */
    if (start >= i_size_read(inode)) {
        zero_user(page, 0, PAGE_SIZE);
        SetPageUptodate(page);
        ret = 0;
        goto out_alloc;
    }

    if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
        ret = ocfs2_readpage_inline(inode, page);
    else
        ret = block_read_full_page(page, ocfs2_get_block);
    unlock = 0;

out_alloc:
    up_read(&OCFS2_I(inode)->ip_alloc_sem);
out_inode_unlock:
    ocfs2_inode_unlock(inode, 0);
out:
    if (unlock)
        unlock_page(page);
    return ret;
}

/*
 * This is used only for read-ahead. Failures or difficult to handle
 * situations are safe to ignore.
 *
 * Right now, we don't bother with BH_Boundary - in-inode extent lists
 * are quite large (243 extents on 4k blocks), so most inodes don't
 * grow out to a tree. If need be, detecting boundary extents could
 * trivially be added in a future version of ocfs2_get_block().
 */
static int ocfs2_readpages(struct file *filp, struct address_space *mapping,
               struct list_head *pages, unsigned nr_pages)
{
    int ret, err = -EIO;
    struct inode *inode = mapping->host;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    loff_t start;
    struct page *last;

    /*
     * Use the nonblocking flag for the dlm code to avoid page
     * lock inversion, but don't bother with retrying.
     */
    ret = ocfs2_inode_lock_full(inode, NULL, 0, OCFS2_LOCK_NONBLOCK);
    if (ret)
        return err;

    if (down_read_trylock(&oi->ip_alloc_sem) == 0) {
        ocfs2_inode_unlock(inode, 0);
        return err;
    }

    /*
     * Don't bother with inline-data. There isn't anything
     * to read-ahead in that case anyway...
     */
    if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL)
        goto out_unlock;

    /*
     * Check whether a remote node truncated this file - we just
     * drop out in that case as it's not worth handling here.
     */
    last = list_entry(pages->prev, struct page, lru);
    start = (loff_t)last->index << PAGE_CACHE_SHIFT;
    if (start >= i_size_read(inode))
        goto out_unlock;

    err = mpage_readpages(mapping, pages, nr_pages, ocfs2_get_block);

out_unlock:
    up_read(&oi->ip_alloc_sem);
    ocfs2_inode_unlock(inode, 0);

    return err;
}

/* Note: Because we don't support holes, our allocation has
 * already happened (allocation writes zeros to the file data)
 * so we don't have to worry about ordered writes in
 * ocfs2_writepage.
 *
 * ->writepage is called during the process of invalidating the page cache
 * during blocked lock processing.  It can't block on any cluster locks
 * to during block mapping.  It's relying on the fact that the block
 * mapping can't have disappeared under the dirty pages that it is
 * being asked to write back.
 */
static int ocfs2_writepage(struct page *page, struct writeback_control *wbc)
{
    trace_ocfs2_writepage(
        (unsigned long long)OCFS2_I(page->mapping->host)->ip_blkno,
        page->index);

    return block_write_full_page(page, ocfs2_get_block, wbc);
}

/* Taken from ext3. We don't necessarily need the full blown
 * functionality yet, but IMHO it's better to cut and paste the whole
 * thing so we can avoid introducing our own bugs (and easily pick up
 * their fixes when they happen) --Mark */
int walk_page_buffers(  handle_t *handle,
            struct buffer_head *head,
            unsigned from,
            unsigned to,
            int *partial,
            int (*fn)(  handle_t *handle,
                    struct buffer_head *bh))
{
    struct buffer_head *bh;
    unsigned block_start, block_end;
    unsigned blocksize = head->b_size;
    int err, ret = 0;
    struct buffer_head *next;

    for (   bh = head, block_start = 0;
        ret == 0 && (bh != head || !block_start);
            block_start = block_end, bh = next)
    {
        next = bh->b_this_page;
        block_end = block_start + blocksize;
        if (block_end <= from || block_start >= to) {
            if (partial && !buffer_uptodate(bh))
                *partial = 1;
            continue;
        }
        err = (*fn)(handle, bh);
        if (!ret)
            ret = err;
    }
    return ret;
}

static sector_t ocfs2_bmap(struct address_space *mapping, sector_t block)
{
    sector_t status;
    u64 p_blkno = 0;
    int err = 0;
    struct inode *inode = mapping->host;

    trace_ocfs2_bmap((unsigned long long)OCFS2_I(inode)->ip_blkno,
             (unsigned long long)block);

    /* We don't need to lock journal system files, since they aren't
     * accessed concurrently from multiple nodes.
     */
    if (!INODE_JOURNAL(inode)) {
        err = ocfs2_inode_lock(inode, NULL, 0);
        if (err) {
            if (err != -ENOENT)
                mlog_errno(err);
            goto bail;
        }
        down_read(&OCFS2_I(inode)->ip_alloc_sem);
    }

    if (!(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL))
        err = ocfs2_extent_map_get_blocks(inode, block, &p_blkno, NULL,
                          NULL);

    if (!INODE_JOURNAL(inode)) {
        up_read(&OCFS2_I(inode)->ip_alloc_sem);
        ocfs2_inode_unlock(inode, 0);
    }

    if (err) {
        mlog(ML_ERROR, "get_blocks() failed, block = %llu\n",
             (unsigned long long)block);
        mlog_errno(err);
        goto bail;
    }

bail:
    status = err ? 0 : p_blkno;

    return status;
}

/*
 * TODO: Make this into a generic get_blocks function.
 *
 * From do_direct_io in direct-io.c:
 *  "So what we do is to permit the ->get_blocks function to populate
 *   bh.b_size with the size of IO which is permitted at this offset and
 *   this i_blkbits."
 *
 * This function is called directly from get_more_blocks in direct-io.c.
 *
 * called like this: dio->get_blocks(dio->inode, fs_startblk,
 *                  fs_count, map_bh, dio->rw == WRITE);
 *
 * Note that we never bother to allocate blocks here, and thus ignore the
 * create argument.
 */
static int ocfs2_direct_IO_get_blocks(struct inode *inode, sector_t iblock,
                     struct buffer_head *bh_result, int create)
{
    int ret;
    u64 p_blkno, inode_blocks, contig_blocks;
    unsigned int ext_flags;
    unsigned char blocksize_bits = inode->i_sb->s_blocksize_bits;
    unsigned long max_blocks = bh_result->b_size >> inode->i_blkbits;

    /* This function won't even be called if the request isn't all
     * nicely aligned and of the right size, so there's no need
     * for us to check any of that. */

    inode_blocks = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));

    /* This figures out the size of the next contiguous block, and
     * our logical offset */
    ret = ocfs2_extent_map_get_blocks(inode, iblock, &p_blkno,
                      &contig_blocks, &ext_flags);
    if (ret) {
        mlog(ML_ERROR, "get_blocks() failed iblock=%llu\n",
             (unsigned long long)iblock);
        ret = -EIO;
        goto bail;
    }

    /* We should already CoW the refcounted extent in case of create. */
    BUG_ON(create && (ext_flags & OCFS2_EXT_REFCOUNTED));

    /*
     * get_more_blocks() expects us to describe a hole by clearing
     * the mapped bit on bh_result().
     *
     * Consider an unwritten extent as a hole.
     */
    if (p_blkno && !(ext_flags & OCFS2_EXT_UNWRITTEN))
        map_bh(bh_result, inode->i_sb, p_blkno);
    else
        clear_buffer_mapped(bh_result);

    /* make sure we don't map more than max_blocks blocks here as
       that's all the kernel will handle at this point. */
    if (max_blocks < contig_blocks)
        contig_blocks = max_blocks;
    bh_result->b_size = contig_blocks << blocksize_bits;
bail:
    return ret;
}

/*
 * ocfs2_dio_end_io is called by the dio core when a dio is finished.  We're
 * particularly interested in the aio/dio case.  We use the rw_lock DLM lock
 * to protect io on one node from truncation on another.
 */
static void ocfs2_dio_end_io(struct kiocb *iocb,
                 loff_t offset,
                 ssize_t bytes,
                 void *private,
                 int ret,
                 bool is_async)
{
    struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
    int level;
    wait_queue_head_t *wq = ocfs2_ioend_wq(inode);

    /* this io's submitter should not have unlocked this before we could */
    BUG_ON(!ocfs2_iocb_is_rw_locked(iocb));

    if (ocfs2_iocb_is_sem_locked(iocb))
        ocfs2_iocb_clear_sem_locked(iocb);

    if (ocfs2_iocb_is_unaligned_aio(iocb)) {
        ocfs2_iocb_clear_unaligned_aio(iocb);

        if (atomic_dec_and_test(&OCFS2_I(inode)->ip_unaligned_aio) &&
            waitqueue_active(wq)) {
            wake_up_all(wq);
        }
    }

    ocfs2_iocb_clear_rw_locked(iocb);

    level = ocfs2_iocb_rw_locked_level(iocb);
    ocfs2_rw_unlock(inode, level);

    if (is_async)
        aio_complete(iocb, ret, 0);
    inode_dio_done(inode);
}

/*
 * ocfs2_invalidatepage() and ocfs2_releasepage() are shamelessly stolen
 * from ext3.  PageChecked() bits have been removed as OCFS2 does not
 * do journalled data.
 */
static void ocfs2_invalidatepage(struct page *page, unsigned long offset)
{
    journal_t *journal = OCFS2_SB(page->mapping->host->i_sb)->journal->j_journal;

    jbd2_journal_invalidatepage(journal, page, offset);
}

static int ocfs2_releasepage(struct page *page, gfp_t wait)
{
    journal_t *journal = OCFS2_SB(page->mapping->host->i_sb)->journal->j_journal;

    if (!page_has_buffers(page))
        return 0;
    return jbd2_journal_try_to_free_buffers(journal, page, wait);
}

static ssize_t ocfs2_direct_IO(int rw,
                   struct kiocb *iocb,
                   const struct iovec *iov,
                   loff_t offset,
                   unsigned long nr_segs)
{
    struct file *file = iocb->ki_filp;
    struct inode *inode = file->f_path.dentry->d_inode->i_mapping->host;

    /*
     * Fallback to buffered I/O if we see an inode without
     * extents.
     */
    if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL)
        return 0;

    /* Fallback to buffered I/O if we are appending. */
    if (i_size_read(inode) <= offset)
        return 0;

    return __blockdev_direct_IO(rw, iocb, inode, inode->i_sb->s_bdev,
                    iov, offset, nr_segs,
                    ocfs2_direct_IO_get_blocks,
                    ocfs2_dio_end_io, NULL, 0);
}

static void ocfs2_figure_cluster_boundaries(struct ocfs2_super *osb,
                        u32 cpos,
                        unsigned int *start,
                        unsigned int *end)
{
    unsigned int cluster_start = 0, cluster_end = PAGE_CACHE_SIZE;

    if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits)) {
        unsigned int cpp;

        cpp = 1 << (PAGE_CACHE_SHIFT - osb->s_clustersize_bits);

        cluster_start = cpos % cpp;
        cluster_start = cluster_start << osb->s_clustersize_bits;

        cluster_end = cluster_start + osb->s_clustersize;
    }

    BUG_ON(cluster_start > PAGE_SIZE);
    BUG_ON(cluster_end > PAGE_SIZE);

    if (start)
        *start = cluster_start;
    if (end)
        *end = cluster_end;
}

/*
 * 'from' and 'to' are the region in the page to avoid zeroing.
 *
 * If pagesize > clustersize, this function will avoid zeroing outside
 * of the cluster boundary.
 *
 * from == to == 0 is code for "zero the entire cluster region"
 */
static void ocfs2_clear_page_regions(struct page *page,
                     struct ocfs2_super *osb, u32 cpos,
                     unsigned from, unsigned to)
{
    void *kaddr;
    unsigned int cluster_start, cluster_end;

    ocfs2_figure_cluster_boundaries(osb, cpos, &cluster_start, &cluster_end);

    kaddr = kmap_atomic(page);

    if (from || to) {
        if (from > cluster_start)
            memset(kaddr + cluster_start, 0, from - cluster_start);
        if (to < cluster_end)
            memset(kaddr + to, 0, cluster_end - to);
    } else {
        memset(kaddr + cluster_start, 0, cluster_end - cluster_start);
    }

    kunmap_atomic(kaddr);
}

/*
 * Nonsparse file systems fully allocate before we get to the write
 * code. This prevents ocfs2_write() from tagging the write as an
 * allocating one, which means ocfs2_map_page_blocks() might try to
 * read-in the blocks at the tail of our file. Avoid reading them by
 * testing i_size against each block offset.
 */
static int ocfs2_should_read_blk(struct inode *inode, struct page *page,
                 unsigned int block_start)
{
    u64 offset = page_offset(page) + block_start;

    if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
        return 1;

    if (i_size_read(inode) > offset)
        return 1;

    return 0;
}

/*
 * Some of this taken from __block_write_begin(). We already have our
 * mapping by now though, and the entire write will be allocating or
 * it won't, so not much need to use BH_New.
 *
 * This will also skip zeroing, which is handled externally.
 */
int ocfs2_map_page_blocks(struct page *page, u64 *p_blkno,
              struct inode *inode, unsigned int from,
              unsigned int to, int new)
{
    int ret = 0;
    struct buffer_head *head, *bh, *wait[2], **wait_bh = wait;
    unsigned int block_end, block_start;
    unsigned int bsize = 1 << inode->i_blkbits;

    if (!page_has_buffers(page))
        create_empty_buffers(page, bsize, 0);

    head = page_buffers(page);
    for (bh = head, block_start = 0; bh != head || !block_start;
         bh = bh->b_this_page, block_start += bsize) {
        block_end = block_start + bsize;

        clear_buffer_new(bh);

        /*
         * Ignore blocks outside of our i/o range -
         * they may belong to unallocated clusters.
         */
        if (block_start >= to || block_end <= from) {
            if (PageUptodate(page))
                set_buffer_uptodate(bh);
            continue;
        }

        /*
         * For an allocating write with cluster size >= page
         * size, we always write the entire page.
         */
        if (new)
            set_buffer_new(bh);

        if (!buffer_mapped(bh)) {
            map_bh(bh, inode->i_sb, *p_blkno);
            unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
        }

        if (PageUptodate(page)) {
            if (!buffer_uptodate(bh))
                set_buffer_uptodate(bh);
        } else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
               !buffer_new(bh) &&
               ocfs2_should_read_blk(inode, page, block_start) &&
               (block_start < from || block_end > to)) {
            ll_rw_block(READ, 1, &bh);
            *wait_bh++=bh;
        }

        *p_blkno = *p_blkno + 1;
    }

    /*
     * If we issued read requests - let them complete.
     */
    while(wait_bh > wait) {
        wait_on_buffer(*--wait_bh);
        if (!buffer_uptodate(*wait_bh))
            ret = -EIO;
    }

    if (ret == 0 || !new)
        return ret;

    /*
     * If we get -EIO above, zero out any newly allocated blocks
     * to avoid exposing stale data.
     */
    bh = head;
    block_start = 0;
    do {
        block_end = block_start + bsize;
        if (block_end <= from)
            goto next_bh;
        if (block_start >= to)
            break;

        zero_user(page, block_start, bh->b_size);
        set_buffer_uptodate(bh);
        mark_buffer_dirty(bh);

next_bh:
        block_start = block_end;
        bh = bh->b_this_page;
    } while (bh != head);

    return ret;
}

#if (PAGE_CACHE_SIZE >= OCFS2_MAX_CLUSTERSIZE)
#define OCFS2_MAX_CTXT_PAGES    1
#else
#define OCFS2_MAX_CTXT_PAGES    (OCFS2_MAX_CLUSTERSIZE / PAGE_CACHE_SIZE)
#endif

#define OCFS2_MAX_CLUSTERS_PER_PAGE (PAGE_CACHE_SIZE / OCFS2_MIN_CLUSTERSIZE)

/*
 * Describe the state of a single cluster to be written to.
 */
struct ocfs2_write_cluster_desc {
    u32     c_cpos;
    u32     c_phys;
    /*
     * Give this a unique field because c_phys eventually gets
     * filled.
     */
    unsigned    c_new;
    unsigned    c_unwritten;
    unsigned    c_needs_zero;
};

struct ocfs2_write_ctxt {
    /* Logical cluster position / len of write */
    u32             w_cpos;
    u32             w_clen;

    /* First cluster allocated in a nonsparse extend */
    u32             w_first_new_cpos;

    struct ocfs2_write_cluster_desc w_desc[OCFS2_MAX_CLUSTERS_PER_PAGE];

    /*
     * This is true if page_size > cluster_size.
     *
     * It triggers a set of special cases during write which might
     * have to deal with allocating writes to partial pages.
     */
    unsigned int            w_large_pages;

    /*
     * Pages involved in this write.
     *
     * w_target_page is the page being written to by the user.
     *
     * w_pages is an array of pages which always contains
     * w_target_page, and in the case of an allocating write with
     * page_size < cluster size, it will contain zero'd and mapped
     * pages adjacent to w_target_page which need to be written
     * out in so that future reads from that region will get
     * zero's.
     */
    unsigned int            w_num_pages;
    struct page         *w_pages[OCFS2_MAX_CTXT_PAGES];
    struct page         *w_target_page;

    /*
     * w_target_locked is used for page_mkwrite path indicating no unlocking
     * against w_target_page in ocfs2_write_end_nolock.
     */
    unsigned int            w_target_locked:1;

    /*
     * ocfs2_write_end() uses this to know what the real range to
     * write in the target should be.
     */
    unsigned int            w_target_from;
    unsigned int            w_target_to;

    /*
     * We could use journal_current_handle() but this is cleaner,
     * IMHO -Mark
     */
    handle_t            *w_handle;

    struct buffer_head      *w_di_bh;

    struct ocfs2_cached_dealloc_ctxt w_dealloc;
};

void ocfs2_unlock_and_free_pages(struct page **pages, int num_pages)
{
    int i;

    for(i = 0; i < num_pages; i++) {
        if (pages[i]) {
            unlock_page(pages[i]);
            mark_page_accessed(pages[i]);
            page_cache_release(pages[i]);
        }
    }
}

static void ocfs2_free_write_ctxt(struct ocfs2_write_ctxt *wc)
{
    int i;

    /*
     * w_target_locked is only set to true in the page_mkwrite() case.
     * The intent is to allow us to lock the target page from write_begin()
     * to write_end(). The caller must hold a ref on w_target_page.
     */
    if (wc->w_target_locked) {
        BUG_ON(!wc->w_target_page);
        for (i = 0; i < wc->w_num_pages; i++) {
            if (wc->w_target_page == wc->w_pages[i]) {
                wc->w_pages[i] = NULL;
                break;
            }
        }
        mark_page_accessed(wc->w_target_page);
        page_cache_release(wc->w_target_page);
    }
    ocfs2_unlock_and_free_pages(wc->w_pages, wc->w_num_pages);

    brelse(wc->w_di_bh);
    kfree(wc);
}

static int ocfs2_alloc_write_ctxt(struct ocfs2_write_ctxt **wcp,
                  struct ocfs2_super *osb, loff_t pos,
                  unsigned len, struct buffer_head *di_bh)
{
    u32 cend;
    struct ocfs2_write_ctxt *wc;

    wc = kzalloc(sizeof(struct ocfs2_write_ctxt), GFP_NOFS);
    if (!wc)
        return -ENOMEM;

    wc->w_cpos = pos >> osb->s_clustersize_bits;
    wc->w_first_new_cpos = UINT_MAX;
    cend = (pos + len - 1) >> osb->s_clustersize_bits;
    wc->w_clen = cend - wc->w_cpos + 1;
    get_bh(di_bh);
    wc->w_di_bh = di_bh;

    if (unlikely(PAGE_CACHE_SHIFT > osb->s_clustersize_bits))
        wc->w_large_pages = 1;
    else
        wc->w_large_pages = 0;

    ocfs2_init_dealloc_ctxt(&wc->w_dealloc);

    *wcp = wc;

    return 0;
}

/*
 * If a page has any new buffers, zero them out here, and mark them uptodate
 * and dirty so they'll be written out (in order to prevent uninitialised
 * block data from leaking). And clear the new bit.
 */
static void ocfs2_zero_new_buffers(struct page *page, unsigned from, unsigned to)
{
    unsigned int block_start, block_end;
    struct buffer_head *head, *bh;

    BUG_ON(!PageLocked(page));
    if (!page_has_buffers(page))
        return;

    bh = head = page_buffers(page);
    block_start = 0;
    do {
        block_end = block_start + bh->b_size;

        if (buffer_new(bh)) {
            if (block_end > from && block_start < to) {
                if (!PageUptodate(page)) {
                    unsigned start, end;

                    start = max(from, block_start);
                    end = min(to, block_end);

                    zero_user_segment(page, start, end);
                    set_buffer_uptodate(bh);
                }

                clear_buffer_new(bh);
                mark_buffer_dirty(bh);
            }
        }

        block_start = block_end;
        bh = bh->b_this_page;
    } while (bh != head);
}

/*
 * Only called when we have a failure during allocating write to write
 * zero's to the newly allocated region.
 */
static void ocfs2_write_failure(struct inode *inode,
                struct ocfs2_write_ctxt *wc,
                loff_t user_pos, unsigned user_len)
{
    int i;
    unsigned from = user_pos & (PAGE_CACHE_SIZE - 1),
        to = user_pos + user_len;
    struct page *tmppage;

    ocfs2_zero_new_buffers(wc->w_target_page, from, to);

    for(i = 0; i < wc->w_num_pages; i++) {
        tmppage = wc->w_pages[i];

        if (page_has_buffers(tmppage)) {
            if (ocfs2_should_order_data(inode))
                ocfs2_jbd2_file_inode(wc->w_handle, inode);

            block_commit_write(tmppage, from, to);
        }
    }
}

static int ocfs2_prepare_page_for_write(struct inode *inode, u64 *p_blkno,
                    struct ocfs2_write_ctxt *wc,
                    struct page *page, u32 cpos,
                    loff_t user_pos, unsigned user_len,
                    int new)
{
    int ret;
    unsigned int map_from = 0, map_to = 0;
    unsigned int cluster_start, cluster_end;
    unsigned int user_data_from = 0, user_data_to = 0;

    ocfs2_figure_cluster_boundaries(OCFS2_SB(inode->i_sb), cpos,
                    &cluster_start, &cluster_end);

    /* treat the write as new if the a hole/lseek spanned across
     * the page boundary.
     */
    new = new | ((i_size_read(inode) <= page_offset(page)) &&
            (page_offset(page) <= user_pos));

    if (page == wc->w_target_page) {
        map_from = user_pos & (PAGE_CACHE_SIZE - 1);
        map_to = map_from + user_len;

        if (new)
            ret = ocfs2_map_page_blocks(page, p_blkno, inode,
                            cluster_start, cluster_end,
                            new);
        else
            ret = ocfs2_map_page_blocks(page, p_blkno, inode,
                            map_from, map_to, new);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        user_data_from = map_from;
        user_data_to = map_to;
        if (new) {
            map_from = cluster_start;
            map_to = cluster_end;
        }
    } else {
        /*
         * If we haven't allocated the new page yet, we
         * shouldn't be writing it out without copying user
         * data. This is likely a math error from the caller.
         */
        BUG_ON(!new);

        map_from = cluster_start;
        map_to = cluster_end;

        ret = ocfs2_map_page_blocks(page, p_blkno, inode,
                        cluster_start, cluster_end, new);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    /*
     * Parts of newly allocated pages need to be zero'd.
     *
     * Above, we have also rewritten 'to' and 'from' - as far as
     * the rest of the function is concerned, the entire cluster
     * range inside of a page needs to be written.
     *
     * We can skip this if the page is up to date - it's already
     * been zero'd from being read in as a hole.
     */
    if (new && !PageUptodate(page))
        ocfs2_clear_page_regions(page, OCFS2_SB(inode->i_sb),
                     cpos, user_data_from, user_data_to);

    flush_dcache_page(page);

out:
    return ret;
}

/*
 * This function will only grab one clusters worth of pages.
 */
static int ocfs2_grab_pages_for_write(struct address_space *mapping,
                      struct ocfs2_write_ctxt *wc,
                      u32 cpos, loff_t user_pos,
                      unsigned user_len, int new,
                      struct page *mmap_page)
{
    int ret = 0, i;
    unsigned long start, target_index, end_index, index;
    struct inode *inode = mapping->host;
    loff_t last_byte;

    target_index = user_pos >> PAGE_CACHE_SHIFT;

    /*
     * Figure out how many pages we'll be manipulating here. For
     * non allocating write, we just change the one
     * page. Otherwise, we'll need a whole clusters worth.  If we're
     * writing past i_size, we only need enough pages to cover the
     * last page of the write.
     */
    if (new) {
        wc->w_num_pages = ocfs2_pages_per_cluster(inode->i_sb);
        start = ocfs2_align_clusters_to_page_index(inode->i_sb, cpos);
        /*
         * We need the index *past* the last page we could possibly
         * touch.  This is the page past the end of the write or
         * i_size, whichever is greater.
         */
        last_byte = max(user_pos + user_len, i_size_read(inode));
        BUG_ON(last_byte < 1);
        end_index = ((last_byte - 1) >> PAGE_CACHE_SHIFT) + 1;
        if ((start + wc->w_num_pages) > end_index)
            wc->w_num_pages = end_index - start;
    } else {
        wc->w_num_pages = 1;
        start = target_index;
    }

    for(i = 0; i < wc->w_num_pages; i++) {
        index = start + i;

        if (index == target_index && mmap_page) {
            /*
             * ocfs2_pagemkwrite() is a little different
             * and wants us to directly use the page
             * passed in.
             */
            lock_page(mmap_page);

            /* Exit and let the caller retry */
            if (mmap_page->mapping != mapping) {
                WARN_ON(mmap_page->mapping);
                unlock_page(mmap_page);
                ret = -EAGAIN;
                goto out;
            }

            page_cache_get(mmap_page);
            wc->w_pages[i] = mmap_page;
            wc->w_target_locked = true;
        } else {
            wc->w_pages[i] = find_or_create_page(mapping, index,
                                 GFP_NOFS);
            if (!wc->w_pages[i]) {
                ret = -ENOMEM;
                mlog_errno(ret);
                goto out;
            }
        }

        if (index == target_index)
            wc->w_target_page = wc->w_pages[i];
    }
out:
    if (ret)
        wc->w_target_locked = false;
    return ret;
}

/*
 * Prepare a single cluster for write one cluster into the file.
 */
static int ocfs2_write_cluster(struct address_space *mapping,
                   u32 phys, unsigned int unwritten,
                   unsigned int should_zero,
                   struct ocfs2_alloc_context *data_ac,
                   struct ocfs2_alloc_context *meta_ac,
                   struct ocfs2_write_ctxt *wc, u32 cpos,
                   loff_t user_pos, unsigned user_len)
{
    int ret, i, new;
    u64 v_blkno, p_blkno;
    struct inode *inode = mapping->host;
    struct ocfs2_extent_tree et;

    new = phys == 0 ? 1 : 0;
    if (new) {
        u32 tmp_pos;

        /*
         * This is safe to call with the page locks - it won't take
         * any additional semaphores or cluster locks.
         */
        tmp_pos = cpos;
        ret = ocfs2_add_inode_data(OCFS2_SB(inode->i_sb), inode,
                       &tmp_pos, 1, 0, wc->w_di_bh,
                       wc->w_handle, data_ac,
                       meta_ac, NULL);
        /*
         * This shouldn't happen because we must have already
         * calculated the correct meta data allocation required. The
         * internal tree allocation code should know how to increase
         * transaction credits itself.
         *
         * If need be, we could handle -EAGAIN for a
         * RESTART_TRANS here.
         */
        mlog_bug_on_msg(ret == -EAGAIN,
                "Inode %llu: EAGAIN return during allocation.\n",
                (unsigned long long)OCFS2_I(inode)->ip_blkno);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    } else if (unwritten) {
        ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode),
                          wc->w_di_bh);
        ret = ocfs2_mark_extent_written(inode, &et,
                        wc->w_handle, cpos, 1, phys,
                        meta_ac, &wc->w_dealloc);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

    if (should_zero)
        v_blkno = ocfs2_clusters_to_blocks(inode->i_sb, cpos);
    else
        v_blkno = user_pos >> inode->i_sb->s_blocksize_bits;

    /*
     * The only reason this should fail is due to an inability to
     * find the extent added.
     */
    ret = ocfs2_extent_map_get_blocks(inode, v_blkno, &p_blkno, NULL,
                      NULL);
    if (ret < 0) {
        ocfs2_error(inode->i_sb, "Corrupting extend for inode %llu, "
                "at logical block %llu",
                (unsigned long long)OCFS2_I(inode)->ip_blkno,
                (unsigned long long)v_blkno);
        goto out;
    }

    BUG_ON(p_blkno == 0);

    for(i = 0; i < wc->w_num_pages; i++) {
        int tmpret;

        tmpret = ocfs2_prepare_page_for_write(inode, &p_blkno, wc,
                              wc->w_pages[i], cpos,
                              user_pos, user_len,
                              should_zero);
        if (tmpret) {
            mlog_errno(tmpret);
            if (ret == 0)
                ret = tmpret;
        }
    }

    /*
     * We only have cleanup to do in case of allocating write.
     */
    if (ret && new)
        ocfs2_write_failure(inode, wc, user_pos, user_len);

out:

    return ret;
}

static int ocfs2_write_cluster_by_desc(struct address_space *mapping,
                       struct ocfs2_alloc_context *data_ac,
                       struct ocfs2_alloc_context *meta_ac,
                       struct ocfs2_write_ctxt *wc,
                       loff_t pos, unsigned len)
{
    int ret, i;
    loff_t cluster_off;
    unsigned int local_len = len;
    struct ocfs2_write_cluster_desc *desc;
    struct ocfs2_super *osb = OCFS2_SB(mapping->host->i_sb);

    for (i = 0; i < wc->w_clen; i++) {
        desc = &wc->w_desc[i];

        /*
         * We have to make sure that the total write passed in
         * doesn't extend past a single cluster.
         */
        local_len = len;
        cluster_off = pos & (osb->s_clustersize - 1);
        if ((cluster_off + local_len) > osb->s_clustersize)
            local_len = osb->s_clustersize - cluster_off;

        ret = ocfs2_write_cluster(mapping, desc->c_phys,
                      desc->c_unwritten,
                      desc->c_needs_zero,
                      data_ac, meta_ac,
                      wc, desc->c_cpos, pos, local_len);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        len -= local_len;
        pos += local_len;
    }

    ret = 0;
out:
    return ret;
}

/*
 * ocfs2_write_end() wants to know which parts of the target page it
 * should complete the write on. It's easiest to compute them ahead of
 * time when a more complete view of the write is available.
 */
static void ocfs2_set_target_boundaries(struct ocfs2_super *osb,
                    struct ocfs2_write_ctxt *wc,
                    loff_t pos, unsigned len, int alloc)
{
    struct ocfs2_write_cluster_desc *desc;

    wc->w_target_from = pos & (PAGE_CACHE_SIZE - 1);
    wc->w_target_to = wc->w_target_from + len;

    if (alloc == 0)
        return;

    /*
     * Allocating write - we may have different boundaries based
     * on page size and cluster size.
     *
     * NOTE: We can no longer compute one value from the other as
     * the actual write length and user provided length may be
     * different.
     */

    if (wc->w_large_pages) {
        /*
         * We only care about the 1st and last cluster within
         * our range and whether they should be zero'd or not. Either
         * value may be extended out to the start/end of a
         * newly allocated cluster.
         */
        desc = &wc->w_desc[0];
        if (desc->c_needs_zero)
            ocfs2_figure_cluster_boundaries(osb,
                            desc->c_cpos,
                            &wc->w_target_from,
                            NULL);

        desc = &wc->w_desc[wc->w_clen - 1];
        if (desc->c_needs_zero)
            ocfs2_figure_cluster_boundaries(osb,
                            desc->c_cpos,
                            NULL,
                            &wc->w_target_to);
    } else {
        wc->w_target_from = 0;
        wc->w_target_to = PAGE_CACHE_SIZE;
    }
}

/*
 * Populate each single-cluster write descriptor in the write context
 * with information about the i/o to be done.
 *
 * Returns the number of clusters that will have to be allocated, as
 * well as a worst case estimate of the number of extent records that
 * would have to be created during a write to an unwritten region.
 */
static int ocfs2_populate_write_desc(struct inode *inode,
                     struct ocfs2_write_ctxt *wc,
                     unsigned int *clusters_to_alloc,
                     unsigned int *extents_to_split)
{
    int ret;
    struct ocfs2_write_cluster_desc *desc;
    unsigned int num_clusters = 0;
    unsigned int ext_flags = 0;
    u32 phys = 0;
    int i;

    *clusters_to_alloc = 0;
    *extents_to_split = 0;

    for (i = 0; i < wc->w_clen; i++) {
        desc = &wc->w_desc[i];
        desc->c_cpos = wc->w_cpos + i;

        if (num_clusters == 0) {
            /*
             * Need to look up the next extent record.
             */
            ret = ocfs2_get_clusters(inode, desc->c_cpos, &phys,
                         &num_clusters, &ext_flags);
            if (ret) {
                mlog_errno(ret);
                goto out;
            }

            /* We should already CoW the refcountd extent. */
            BUG_ON(ext_flags & OCFS2_EXT_REFCOUNTED);

            /*
             * Assume worst case - that we're writing in
             * the middle of the extent.
             *
             * We can assume that the write proceeds from
             * left to right, in which case the extent
             * insert code is smart enough to coalesce the
             * next splits into the previous records created.
             */
            if (ext_flags & OCFS2_EXT_UNWRITTEN)
                *extents_to_split = *extents_to_split + 2;
        } else if (phys) {
            /*
             * Only increment phys if it doesn't describe
             * a hole.
             */
            phys++;
        }

        /*
         * If w_first_new_cpos is < UINT_MAX, we have a non-sparse
         * file that got extended.  w_first_new_cpos tells us
         * where the newly allocated clusters are so we can
         * zero them.
         */
        if (desc->c_cpos >= wc->w_first_new_cpos) {
            BUG_ON(phys == 0);
            desc->c_needs_zero = 1;
        }

        desc->c_phys = phys;
        if (phys == 0) {
            desc->c_new = 1;
            desc->c_needs_zero = 1;
            *clusters_to_alloc = *clusters_to_alloc + 1;
        }

        if (ext_flags & OCFS2_EXT_UNWRITTEN) {
            desc->c_unwritten = 1;
            desc->c_needs_zero = 1;
        }

        num_clusters--;
    }

    ret = 0;
out:
    return ret;
}

static int ocfs2_write_begin_inline(struct address_space *mapping,
                    struct inode *inode,
                    struct ocfs2_write_ctxt *wc)
{
    int ret;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct page *page;
    handle_t *handle;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;

    page = find_or_create_page(mapping, 0, GFP_NOFS);
    if (!page) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }
    /*
     * If we don't set w_num_pages then this page won't get unlocked
     * and freed on cleanup of the write context.
     */
    wc->w_pages[0] = wc->w_target_page = page;
    wc->w_num_pages = 1;

    handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        ocfs2_commit_trans(osb, handle);

        mlog_errno(ret);
        goto out;
    }

    if (!(OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL))
        ocfs2_set_inode_data_inline(inode, di);

    if (!PageUptodate(page)) {
        ret = ocfs2_read_inline_data(inode, page, wc->w_di_bh);
        if (ret) {
            ocfs2_commit_trans(osb, handle);

            goto out;
        }
    }

    wc->w_handle = handle;
out:
    return ret;
}

int ocfs2_size_fits_inline_data(struct buffer_head *di_bh, u64 new_size)
{
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)di_bh->b_data;

    if (new_size <= le16_to_cpu(di->id2.i_data.id_count))
        return 1;
    return 0;
}

static int ocfs2_try_to_write_inline_data(struct address_space *mapping,
                      struct inode *inode, loff_t pos,
                      unsigned len, struct page *mmap_page,
                      struct ocfs2_write_ctxt *wc)
{
    int ret, written = 0;
    loff_t end = pos + len;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_dinode *di = NULL;

    trace_ocfs2_try_to_write_inline_data((unsigned long long)oi->ip_blkno,
                         len, (unsigned long long)pos,
                         oi->ip_dyn_features);

    /*
     * Handle inodes which already have inline data 1st.
     */
    if (oi->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
        if (mmap_page == NULL &&
            ocfs2_size_fits_inline_data(wc->w_di_bh, end))
            goto do_inline_write;

        /*
         * The write won't fit - we have to give this inode an
         * inline extent list now.
         */
        ret = ocfs2_convert_inline_data_to_extents(inode, wc->w_di_bh);
        if (ret)
            mlog_errno(ret);
        goto out;
    }

    /*
     * Check whether the inode can accept inline data.
     */
    if (oi->ip_clusters != 0 || i_size_read(inode) != 0)
        return 0;

    /*
     * Check whether the write can fit.
     */
    di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;
    if (mmap_page ||
        end > ocfs2_max_inline_data_with_xattr(inode->i_sb, di))
        return 0;

do_inline_write:
    ret = ocfs2_write_begin_inline(mapping, inode, wc);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /*
     * This signals to the caller that the data can be written
     * inline.
     */
    written = 1;
out:
    return written ? written : ret;
}

/*
 * This function only does anything for file systems which can't
 * handle sparse files.
 *
 * What we want to do here is fill in any hole between the current end
 * of allocation and the end of our write. That way the rest of the
 * write path can treat it as an non-allocating write, which has no
 * special case code for sparse/nonsparse files.
 */
static int ocfs2_expand_nonsparse_inode(struct inode *inode,
                    struct buffer_head *di_bh,
                    loff_t pos, unsigned len,
                    struct ocfs2_write_ctxt *wc)
{
    int ret;
    loff_t newsize = pos + len;

    BUG_ON(ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)));

    if (newsize <= i_size_read(inode))
        return 0;

    ret = ocfs2_extend_no_holes(inode, di_bh, newsize, pos);
    if (ret)
        mlog_errno(ret);

    wc->w_first_new_cpos =
        ocfs2_clusters_for_bytes(inode->i_sb, i_size_read(inode));

    return ret;
}

static int ocfs2_zero_tail(struct inode *inode, struct buffer_head *di_bh,
               loff_t pos)
{
    int ret = 0;

    BUG_ON(!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)));
    if (pos > i_size_read(inode))
        ret = ocfs2_zero_extend(inode, di_bh, pos);

    return ret;
}

/*
 * Try to flush truncate logs if we can free enough clusters from it.
 * As for return value, "< 0" means error, "0" no space and "1" means
 * we have freed enough spaces and let the caller try to allocate again.
 */
static int ocfs2_try_to_free_truncate_log(struct ocfs2_super *osb,
                      unsigned int needed)
{
    tid_t target;
    int ret = 0;
    unsigned int truncated_clusters;

    mutex_lock(&osb->osb_tl_inode->i_mutex);
    truncated_clusters = osb->truncated_clusters;
    mutex_unlock(&osb->osb_tl_inode->i_mutex);

    /*
     * Check whether we can succeed in allocating if we free
     * the truncate log.
     */
    if (truncated_clusters < needed)
        goto out;

    ret = ocfs2_flush_truncate_log(osb);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    if (jbd2_journal_start_commit(osb->journal->j_journal, &target)) {
        jbd2_log_wait_commit(osb->journal->j_journal, target);
        ret = 1;
    }
out:
    return ret;
}

int ocfs2_write_begin_nolock(struct file *filp,
                 struct address_space *mapping,
                 loff_t pos, unsigned len, unsigned flags,
                 struct page **pagep, void **fsdata,
                 struct buffer_head *di_bh, struct page *mmap_page)
{
    int ret, cluster_of_pages, credits = OCFS2_INODE_UPDATE_CREDITS;
    unsigned int clusters_to_alloc, extents_to_split, clusters_need = 0;
    struct ocfs2_write_ctxt *wc;
    struct inode *inode = mapping->host;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_dinode *di;
    struct ocfs2_alloc_context *data_ac = NULL;
    struct ocfs2_alloc_context *meta_ac = NULL;
    handle_t *handle;
    struct ocfs2_extent_tree et;
    int try_free = 1, ret1;

try_again:
    ret = ocfs2_alloc_write_ctxt(&wc, osb, pos, len, di_bh);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    if (ocfs2_supports_inline_data(osb)) {
        ret = ocfs2_try_to_write_inline_data(mapping, inode, pos, len,
                             mmap_page, wc);
        if (ret == 1) {
            ret = 0;
            goto success;
        }
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }
    }

    if (ocfs2_sparse_alloc(osb))
        ret = ocfs2_zero_tail(inode, di_bh, pos);
    else
        ret = ocfs2_expand_nonsparse_inode(inode, di_bh, pos, len,
                           wc);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    ret = ocfs2_check_range_for_refcount(inode, pos, len);
    if (ret < 0) {
        mlog_errno(ret);
        goto out;
    } else if (ret == 1) {
        clusters_need = wc->w_clen;
        ret = ocfs2_refcount_cow(inode, filp, di_bh,
                     wc->w_cpos, wc->w_clen, UINT_MAX);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    ret = ocfs2_populate_write_desc(inode, wc, &clusters_to_alloc,
                    &extents_to_split);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }
    clusters_need += clusters_to_alloc;

    di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;

    trace_ocfs2_write_begin_nolock(
            (unsigned long long)OCFS2_I(inode)->ip_blkno,
            (long long)i_size_read(inode),
            le32_to_cpu(di->i_clusters),
            pos, len, flags, mmap_page,
            clusters_to_alloc, extents_to_split);

    /*
     * We set w_target_from, w_target_to here so that
     * ocfs2_write_end() knows which range in the target page to
     * write out. An allocation requires that we write the entire
     * cluster range.
     */
    if (clusters_to_alloc || extents_to_split) {
        /*
         * XXX: We are stretching the limits of
         * ocfs2_lock_allocators(). It greatly over-estimates
         * the work to be done.
         */
        ocfs2_init_dinode_extent_tree(&et, INODE_CACHE(inode),
                          wc->w_di_bh);
        ret = ocfs2_lock_allocators(inode, &et,
                        clusters_to_alloc, extents_to_split,
                        &data_ac, &meta_ac);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }

        if (data_ac)
            data_ac->ac_resv = &OCFS2_I(inode)->ip_la_data_resv;

        credits = ocfs2_calc_extend_credits(inode->i_sb,
                            &di->id2.i_list,
                            clusters_to_alloc);

    }

    /*
     * We have to zero sparse allocated clusters, unwritten extent clusters,
     * and non-sparse clusters we just extended.  For non-sparse writes,
     * we know zeros will only be needed in the first and/or last cluster.
     */
    if (clusters_to_alloc || extents_to_split ||
        (wc->w_clen && (wc->w_desc[0].c_needs_zero ||
                wc->w_desc[wc->w_clen - 1].c_needs_zero)))
        cluster_of_pages = 1;
    else
        cluster_of_pages = 0;

    ocfs2_set_target_boundaries(osb, wc, pos, len, cluster_of_pages);

    handle = ocfs2_start_trans(osb, credits);
    if (IS_ERR(handle)) {
        ret = PTR_ERR(handle);
        mlog_errno(ret);
        goto out;
    }

    wc->w_handle = handle;

    if (clusters_to_alloc) {
        ret = dquot_alloc_space_nodirty(inode,
            ocfs2_clusters_to_bytes(osb->sb, clusters_to_alloc));
        if (ret)
            goto out_commit;
    }
    /*
     * We don't want this to fail in ocfs2_write_end(), so do it
     * here.
     */
    ret = ocfs2_journal_access_di(handle, INODE_CACHE(inode), wc->w_di_bh,
                      OCFS2_JOURNAL_ACCESS_WRITE);
    if (ret) {
        mlog_errno(ret);
        goto out_quota;
    }

    /*
     * Fill our page array first. That way we've grabbed enough so
     * that we can zero and flush if we error after adding the
     * extent.
     */
    ret = ocfs2_grab_pages_for_write(mapping, wc, wc->w_cpos, pos, len,
                     cluster_of_pages, mmap_page);
    if (ret && ret != -EAGAIN) {
        mlog_errno(ret);
        goto out_quota;
    }

    /*
     * ocfs2_grab_pages_for_write() returns -EAGAIN if it could not lock
     * the target page. In this case, we exit with no error and no target
     * page. This will trigger the caller, page_mkwrite(), to re-try
     * the operation.
     */
    if (ret == -EAGAIN) {
        BUG_ON(wc->w_target_page);
        ret = 0;
        goto out_quota;
    }

    ret = ocfs2_write_cluster_by_desc(mapping, data_ac, meta_ac, wc, pos,
                      len);
    if (ret) {
        mlog_errno(ret);
        goto out_quota;
    }

    if (data_ac)
        ocfs2_free_alloc_context(data_ac);
    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);

success:
    *pagep = wc->w_target_page;
    *fsdata = wc;
    return 0;
out_quota:
    if (clusters_to_alloc)
        dquot_free_space(inode,
              ocfs2_clusters_to_bytes(osb->sb, clusters_to_alloc));
out_commit:
    ocfs2_commit_trans(osb, handle);

out:
    ocfs2_free_write_ctxt(wc);

    if (data_ac)
        ocfs2_free_alloc_context(data_ac);
    if (meta_ac)
        ocfs2_free_alloc_context(meta_ac);

    if (ret == -ENOSPC && try_free) {
        /*
         * Try to free some truncate log so that we can have enough
         * clusters to allocate.
         */
        try_free = 0;

        ret1 = ocfs2_try_to_free_truncate_log(osb, clusters_need);
        if (ret1 == 1)
            goto try_again;

        if (ret1 < 0)
            mlog_errno(ret1);
    }

    return ret;
}

static int ocfs2_write_begin(struct file *file, struct address_space *mapping,
                 loff_t pos, unsigned len, unsigned flags,
                 struct page **pagep, void **fsdata)
{
    int ret;
    struct buffer_head *di_bh = NULL;
    struct inode *inode = mapping->host;

    ret = ocfs2_inode_lock(inode, &di_bh, 1);
    if (ret) {
        mlog_errno(ret);
        return ret;
    }

    /*
     * Take alloc sem here to prevent concurrent lookups. That way
     * the mapping, zeroing and tree manipulation within
     * ocfs2_write() will be safe against ->readpage(). This
     * should also serve to lock out allocation from a shared
     * writeable region.
     */
    down_write(&OCFS2_I(inode)->ip_alloc_sem);

    ret = ocfs2_write_begin_nolock(file, mapping, pos, len, flags, pagep,
                       fsdata, di_bh, NULL);
    if (ret) {
        mlog_errno(ret);
        goto out_fail;
    }

    brelse(di_bh);

    return 0;

out_fail:
    up_write(&OCFS2_I(inode)->ip_alloc_sem);

    brelse(di_bh);
    ocfs2_inode_unlock(inode, 1);

    return ret;
}

static void ocfs2_write_end_inline(struct inode *inode, loff_t pos,
                   unsigned len, unsigned *copied,
                   struct ocfs2_dinode *di,
                   struct ocfs2_write_ctxt *wc)
{
    void *kaddr;

    if (unlikely(*copied < len)) {
        if (!PageUptodate(wc->w_target_page)) {
            *copied = 0;
            return;
        }
    }

    kaddr = kmap_atomic(wc->w_target_page);
    memcpy(di->id2.i_data.id_data + pos, kaddr + pos, *copied);
    kunmap_atomic(kaddr);

    trace_ocfs2_write_end_inline(
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         (unsigned long long)pos, *copied,
         le16_to_cpu(di->id2.i_data.id_count),
         le16_to_cpu(di->i_dyn_features));
}

int ocfs2_write_end_nolock(struct address_space *mapping,
               loff_t pos, unsigned len, unsigned copied,
               struct page *page, void *fsdata)
{
    int i;
    unsigned from, to, start = pos & (PAGE_CACHE_SIZE - 1);
    struct inode *inode = mapping->host;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct ocfs2_write_ctxt *wc = fsdata;
    struct ocfs2_dinode *di = (struct ocfs2_dinode *)wc->w_di_bh->b_data;
    handle_t *handle = wc->w_handle;
    struct page *tmppage;

    if (OCFS2_I(inode)->ip_dyn_features & OCFS2_INLINE_DATA_FL) {
        ocfs2_write_end_inline(inode, pos, len, &copied, di, wc);
        goto out_write_size;
    }

    if (unlikely(copied < len)) {
        if (!PageUptodate(wc->w_target_page))
            copied = 0;

        ocfs2_zero_new_buffers(wc->w_target_page, start+copied,
                       start+len);
    }
    flush_dcache_page(wc->w_target_page);

    for(i = 0; i < wc->w_num_pages; i++) {
        tmppage = wc->w_pages[i];

        if (tmppage == wc->w_target_page) {
            from = wc->w_target_from;
            to = wc->w_target_to;

            BUG_ON(from > PAGE_CACHE_SIZE ||
                   to > PAGE_CACHE_SIZE ||
                   to < from);
        } else {
            /*
             * Pages adjacent to the target (if any) imply
             * a hole-filling write in which case we want
             * to flush their entire range.
             */
            from = 0;
            to = PAGE_CACHE_SIZE;
        }

        if (page_has_buffers(tmppage)) {
            if (ocfs2_should_order_data(inode))
                ocfs2_jbd2_file_inode(wc->w_handle, inode);
            block_commit_write(tmppage, from, to);
        }
    }

out_write_size:
    pos += copied;
    if (pos > inode->i_size) {
        i_size_write(inode, pos);
        mark_inode_dirty(inode);
    }
    inode->i_blocks = ocfs2_inode_sector_count(inode);
    di->i_size = cpu_to_le64((u64)i_size_read(inode));
    inode->i_mtime = inode->i_ctime = CURRENT_TIME;
    di->i_mtime = di->i_ctime = cpu_to_le64(inode->i_mtime.tv_sec);
    di->i_mtime_nsec = di->i_ctime_nsec = cpu_to_le32(inode->i_mtime.tv_nsec);
    ocfs2_journal_dirty(handle, wc->w_di_bh);

    ocfs2_commit_trans(osb, handle);

    ocfs2_run_deallocs(osb, &wc->w_dealloc);

    ocfs2_free_write_ctxt(wc);

    return copied;
}

static int ocfs2_write_end(struct file *file, struct address_space *mapping,
               loff_t pos, unsigned len, unsigned copied,
               struct page *page, void *fsdata)
{
    int ret;
    struct inode *inode = mapping->host;

    ret = ocfs2_write_end_nolock(mapping, pos, len, copied, page, fsdata);

    up_write(&OCFS2_I(inode)->ip_alloc_sem);
    ocfs2_inode_unlock(inode, 1);

    return ret;
}

const struct address_space_operations ocfs2_aops = {
    .readpage       = ocfs2_readpage,
    .readpages      = ocfs2_readpages,
    .writepage      = ocfs2_writepage,
    .write_begin        = ocfs2_write_begin,
    .write_end      = ocfs2_write_end,
    .bmap           = ocfs2_bmap,
    .direct_IO      = ocfs2_direct_IO,
    .invalidatepage     = ocfs2_invalidatepage,
    .releasepage        = ocfs2_releasepage,
    .migratepage        = buffer_migrate_page,
    .is_partially_uptodate  = block_is_partially_uptodate,
    .error_remove_page  = generic_error_remove_page,
};