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aops.c

/* -*- 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>

#define MLOG_MASK_PREFIX ML_FILE_IO
#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 "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;

      mlog_entry("(0x%p, %llu, 0x%p, %d)\n", inode,
               (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_block(OCFS2_SB(inode->i_sb),
                          OCFS2_I(inode)->ip_blkno,
                          &bh, OCFS2_BH_CACHED, inode);
      if (status < 0) {
            mlog_errno(status);
            goto bail;
      }
      fe = (struct ocfs2_dinode *) bh->b_data;

      if (!OCFS2_IS_VALID_DINODE(fe)) {
            mlog(ML_ERROR, "Invalid dinode #%llu: signature = %.*s\n",
                 (unsigned long long)le64_to_cpu(fe->i_blkno), 7,
                 fe->i_signature);
            goto bail;
      }

      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, KM_USER0);
                  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, KM_USER0);
                  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:
      if (bh)
            brelse(bh);

      mlog_exit(err);
      return err;
}

static 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 p_blkno, past_eof;
      struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

      mlog_entry("(0x%p, %llu, 0x%p, %d)\n", inode,
               (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, NULL,
                                &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;
      }

      /*
       * 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_prepare_write() to zero.
       */
      mlog_bug_on_msg(create && p_blkno == 0 && ocfs2_sparse_alloc(osb),
                  "ino %lu, iblock %llu\n", inode->i_ino,
                  (unsigned long long)iblock);

      /* 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);

      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();
            }

            past_eof = ocfs2_blocks_for_bytes(inode->i_sb, i_size_read(inode));
            mlog(0, "Inode %lu, past_eof = %llu\n", inode->i_ino,
                 (unsigned long long)past_eof);

            if (create && (iblock >= past_eof))
                  set_buffer_new(bh_result);
      }

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

      mlog_exit(err);
      return err;
}

int ocfs2_read_inline_data(struct inode *inode, struct page *page,
                     struct buffer_head *di_bh)
{
      void *kaddr;
      unsigned int 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(inode->i_sb)) {
            ocfs2_error(inode->i_sb,
                      "Inode %llu has with inline data has bad size: %u",
                      (unsigned long long)OCFS2_I(inode)->ip_blkno, size);
            return -EROFS;
      }

      kaddr = kmap_atomic(page, KM_USER0);
      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, KM_USER0);

      SetPageUptodate(page);

      return 0;
}

static int ocfs2_readpage_inline(struct inode *inode, struct page *page)
{
      int ret;
      struct buffer_head *di_bh = NULL;
      struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

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

      ret = ocfs2_read_block(osb, OCFS2_I(inode)->ip_blkno, &di_bh,
                         OCFS2_BH_CACHED, inode);
      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;

      mlog_entry("(0x%p, %lu)\n", file, (page ? page->index : 0));

      ret = ocfs2_meta_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) {
            ret = AOP_TRUNCATED_PAGE;
            goto out_meta_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(page, 0, PAGE_SIZE, KM_USER0);
            SetPageUptodate(page);
            ret = 0;
            goto out_alloc;
      }

      ret = ocfs2_data_lock_with_page(inode, 0, page);
      if (ret != 0) {
            if (ret == AOP_TRUNCATED_PAGE)
                  unlock = 0;
            mlog_errno(ret);
            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;

      ocfs2_data_unlock(inode, 0);
out_alloc:
      up_read(&OCFS2_I(inode)->ip_alloc_sem);
out_meta_unlock:
      ocfs2_meta_unlock(inode, 0);
out:
      if (unlock)
            unlock_page(page);
      mlog_exit(ret);
      return ret;
}

/* 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)
{
      int ret;

      mlog_entry("(0x%p)\n", page);

      ret = block_write_full_page(page, ocfs2_get_block, wbc);

      mlog_exit(ret);

      return ret;
}

/*
 * This is called from ocfs2_write_zero_page() which has handled it's
 * own cluster locking and has ensured allocation exists for those
 * blocks to be written.
 */
int ocfs2_prepare_write_nolock(struct inode *inode, struct page *page,
                         unsigned from, unsigned to)
{
      int ret;

      ret = block_prepare_write(page, from, to, ocfs2_get_block);

      return ret;
}

/* 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;
}

handle_t *ocfs2_start_walk_page_trans(struct inode *inode,
                                           struct page *page,
                                           unsigned from,
                                           unsigned to)
{
      struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
      handle_t *handle = NULL;
      int ret = 0;

      handle = ocfs2_start_trans(osb, OCFS2_INODE_UPDATE_CREDITS);
      if (!handle) {
            ret = -ENOMEM;
            mlog_errno(ret);
            goto out;
      }

      if (ocfs2_should_order_data(inode)) {
            ret = walk_page_buffers(handle,
                              page_buffers(page),
                              from, to, NULL,
                              ocfs2_journal_dirty_data);
            if (ret < 0) 
                  mlog_errno(ret);
      }
out:
      if (ret) {
            if (handle)
                  ocfs2_commit_trans(osb, handle);
            handle = ERR_PTR(ret);
      }
      return handle;
}

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;

      mlog_entry("(block = %llu)\n", (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_meta_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_meta_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;

      mlog_exit((int)status);

      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);
 */
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));

      /*
       * Any write past EOF is not allowed because we'd be extending.
       */
      if (create && (iblock + max_blocks) > inode_blocks) {
            ret = -EIO;
            goto bail;
      }

      /* 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;
      }

      if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)) && !p_blkno) {
            ocfs2_error(inode->i_sb,
                      "Inode %llu has a hole at block %llu\n",
                      (unsigned long long)OCFS2_I(inode)->ip_blkno,
                      (unsigned long long)iblock);
            ret = -EROFS;
            goto bail;
      }

      /*
       * 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 {
            /*
             * ocfs2_prepare_inode_for_write() should have caught
             * the case where we'd be filling a hole and triggered
             * a buffered write instead.
             */
            if (create) {
                  ret = -EIO;
                  mlog_errno(ret);
                  goto bail;
            }

            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.  Like the core uses
 * i_alloc_sem, 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)
{
      struct inode *inode = iocb->ki_filp->f_path.dentry->d_inode;
      int level;

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

      ocfs2_iocb_clear_rw_locked(iocb);

      level = ocfs2_iocb_rw_locked_level(iocb);
      if (!level)
            up_read(&inode->i_alloc_sem);
      ocfs2_rw_unlock(inode, level);
}

/*
 * 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;

      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 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;
      int ret;

      mlog_entry_void();

      /*
       * 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;

      if (!ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb))) {
            /*
             * We get PR data locks even for O_DIRECT.  This
             * allows concurrent O_DIRECT I/O but doesn't let
             * O_DIRECT with extending and buffered zeroing writes
             * race.  If they did race then the buffered zeroing
             * could be written back after the O_DIRECT I/O.  It's
             * one thing to tell people not to mix buffered and
             * O_DIRECT writes, but expecting them to understand
             * that file extension is also an implicit buffered
             * write is too much.  By getting the PR we force
             * writeback of the buffered zeroing before
             * proceeding.
             */
            ret = ocfs2_data_lock(inode, 0);
            if (ret < 0) {
                  mlog_errno(ret);
                  goto out;
            }
            ocfs2_data_unlock(inode, 0);
      }

      ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
                                  inode->i_sb->s_bdev, iov, offset,
                                  nr_segs, 
                                  ocfs2_direct_IO_get_blocks,
                                  ocfs2_dio_end_io);
out:
      mlog_exit(ret);
      return ret;
}

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, KM_USER0);

      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, KM_USER0);
}

/*
 * 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_prepare_write(). 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(page, block_start, bh->b_size, KM_USER0);
            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;
};

static inline int ocfs2_should_zero_cluster(struct ocfs2_write_cluster_desc *d)
{
      return d->c_new || d->c_unwritten;
}

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

      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.
       */
      struct page             *w_pages[OCFS2_MAX_CTXT_PAGES];
      unsigned int                  w_num_pages;
      struct page             *w_target_page;

      /*
       * 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)
{
      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;
      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_page(page, start, end - start, KM_USER0);
                              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 (ocfs2_should_order_data(inode))
                  walk_page_buffers(wc->w_handle, page_buffers(tmppage),
                                from, to, NULL,
                                ocfs2_journal_dirty_data);

            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);

      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, int new,
                              struct page *mmap_page)
{
      int ret = 0, i;
      unsigned long start, target_index, index;
      struct inode *inode = mapping->host;

      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 (new) {
            wc->w_num_pages = ocfs2_pages_per_cluster(inode->i_sb);
            start = ocfs2_align_clusters_to_page_index(inode->i_sb, cpos);
      } 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);

                  if (mmap_page->mapping != mapping) {
                        unlock_page(mmap_page);
                        /*
                         * Sanity check - the locking in
                         * ocfs2_pagemkwrite() should ensure
                         * that this code doesn't trigger.
                         */
                        ret = -EINVAL;
                        mlog_errno(ret);
                        goto out;
                  }

                  page_cache_get(mmap_page);
                  wc->w_pages[i] = mmap_page;
            } 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:
      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,
                         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, should_zero = 0;
      u64 v_blkno, p_blkno;
      struct inode *inode = mapping->host;

      new = phys == 0 ? 1 : 0;
      if (new || unwritten)
            should_zero = 1;

      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_do_extend_allocation(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) {
            ret = ocfs2_mark_extent_written(inode, wc->w_di_bh,
                                    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)
                        tmpret = ret;
            }
      }

      /*
       * 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, 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 (ocfs2_should_zero_cluster(desc))
                  ocfs2_figure_cluster_boundaries(osb,
                                          desc->c_cpos,
                                          &wc->w_target_from,
                                          NULL);

            desc = &wc->w_desc[wc->w_clen - 1];
            if (ocfs2_should_zero_cluster(desc))
                  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;
                  }

                  /*
                   * 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++;
            }

            desc->c_phys = phys;
            if (phys == 0) {
                  desc->c_new = 1;
                  *clusters_to_alloc = *clusters_to_alloc + 1;
            }
            if (ext_flags & OCFS2_EXT_UNWRITTEN)
                  desc->c_unwritten = 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(handle, 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);

      mlog(0, "Inode %llu, write of %u bytes at off %llu. features: 0x%x\n",
           (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.
       */
      if (mmap_page || end > ocfs2_max_inline_data(inode->i_sb))
            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, loff_t pos,
                              unsigned len,
                              struct ocfs2_write_ctxt *wc)
{
      int ret;
      struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
      loff_t newsize = pos + len;

      if (ocfs2_sparse_alloc(osb))
            return 0;

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

      ret = ocfs2_extend_no_holes(inode, newsize, newsize - len);
      if (ret)
            mlog_errno(ret);

      return ret;
}

int ocfs2_write_begin_nolock(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, credits = OCFS2_INODE_UPDATE_CREDITS;
      unsigned int clusters_to_alloc, extents_to_split;
      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;

      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;
            }
      }

      ret = ocfs2_expand_nonsparse_inode(inode, pos, len, wc);
      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;
      }

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

      /*
       * 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.
             */
            ret = ocfs2_lock_allocators(inode, di, clusters_to_alloc,
                                  extents_to_split, &data_ac, &meta_ac);
            if (ret) {
                  mlog_errno(ret);
                  goto out;
            }

            credits = ocfs2_calc_extend_credits(inode->i_sb, di,
                                        clusters_to_alloc);

      }

      ocfs2_set_target_boundaries(osb, wc, pos, len,
                            clusters_to_alloc + extents_to_split);

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

      wc->w_handle = handle;

      /*
       * We don't want this to fail in ocfs2_write_end(), so do it
       * here.
       */
      ret = ocfs2_journal_access(handle, inode, wc->w_di_bh,
                           OCFS2_JOURNAL_ACCESS_WRITE);
      if (ret) {
            mlog_errno(ret);
            goto out_commit;
      }

      /*
       * 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,
                               clusters_to_alloc + extents_to_split,
                               mmap_page);
      if (ret) {
            mlog_errno(ret);
            goto out_commit;
      }

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

      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_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);
      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_meta_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_data_lock(inode, 1);
      if (ret) {
            mlog_errno(ret);
            goto out_fail;
      }

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

      brelse(di_bh);

      return 0;

out_fail_data:
      ocfs2_data_unlock(inode, 1);
out_fail:
      up_write(&OCFS2_I(inode)->ip_alloc_sem);

      brelse(di_bh);
      ocfs2_meta_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, KM_USER0);
      memcpy(di->id2.i_data.id_data + pos, kaddr + pos, *copied);
      kunmap_atomic(kaddr, KM_USER0);

      mlog(0, "Data written to inode at offset %llu. "
           "id_count = %u, copied = %u, i_dyn_features = 0x%x\n",
           (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 (ocfs2_should_order_data(inode))
                  walk_page_buffers(wc->w_handle, page_buffers(tmppage),
                                from, to, NULL,
                                ocfs2_journal_dirty_data);

            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);

      ocfs2_data_unlock(inode, 1);
      up_write(&OCFS2_I(inode)->ip_alloc_sem);
      ocfs2_meta_unlock(inode, 1);

      return ret;
}

const struct address_space_operations ocfs2_aops = {
      .readpage   = ocfs2_readpage,
      .writepage  = ocfs2_writepage,
      .write_begin      = ocfs2_write_begin,
      .write_end  = ocfs2_write_end,
      .bmap       = ocfs2_bmap,
      .sync_page  = block_sync_page,
      .direct_IO  = ocfs2_direct_IO,
      .invalidatepage   = ocfs2_invalidatepage,
      .releasepage      = ocfs2_releasepage,
      .migratepage      = buffer_migrate_page,
};

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