/*

   * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.

   *

   * Copyright (c) 2001-2011 Anton Altaparmakov and Tuxera Inc.

   *
   * This program/include file 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/include file 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 (in the main directory of the Linux-NTFS
   * distribution in the file COPYING); if not, write to the Free Software
   * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */

  #include <linux/buffer_head.h>

  #include <linux/gfp.h>

  #include <linux/pagemap.h>
  #include <linux/pagevec.h>
  #include <linux/sched.h>
  #include <linux/swap.h>
  #include <linux/uio.h>
  #include <linux/writeback.h>

  #include <asm/page.h>
  #include <asm/uaccess.h>
  
  #include "attrib.h"
  #include "bitmap.h"

  #include "inode.h"
  #include "debug.h"

  #include "lcnalloc.h"
  #include "malloc.h"
  #include "mft.h"

  #include "ntfs.h"
  
  /**
   * ntfs_file_open - called when an inode is about to be opened
   * @vi:		inode to be opened
   * @filp:	file structure describing the inode
   *
   * Limit file size to the page cache limit on architectures where unsigned long
   * is 32-bits. This is the most we can do for now without overflowing the page
   * cache page index. Doing it this way means we don't run into problems because
   * of existing too large files. It would be better to allow the user to read
   * the beginning of the file but I doubt very much anyone is going to hit this
   * check on a 32-bit architecture, so there is no point in adding the extra
   * complexity required to support this.
   *
   * On 64-bit architectures, the check is hopefully optimized away by the
   * compiler.
   *
   * After the check passes, just call generic_file_open() to do its work.
   */
  static int ntfs_file_open(struct inode *vi, struct file *filp)
  {
  	if (sizeof(unsigned long) < 8) {

  		if (i_size_read(vi) > MAX_LFS_FILESIZE)

  			return -EOVERFLOW;

  	}
  	return generic_file_open(vi, filp);
  }
  
  #ifdef NTFS_RW
  
  /**

   * ntfs_attr_extend_initialized - extend the initialized size of an attribute
   * @ni:			ntfs inode of the attribute to extend
   * @new_init_size:	requested new initialized size in bytes
   * @cached_page:	store any allocated but unused page here
   * @lru_pvec:		lru-buffering pagevec of the caller
   *
   * Extend the initialized size of an attribute described by the ntfs inode @ni
   * to @new_init_size bytes.  This involves zeroing any non-sparse space between
   * the old initialized size and @new_init_size both in the page cache and on

   * disk (if relevant complete pages are already uptodate in the page cache then
   * these are simply marked dirty).

   *
   * As a side-effect, the file size (vfs inode->i_size) may be incremented as,
   * in the resident attribute case, it is tied to the initialized size and, in
   * the non-resident attribute case, it may not fall below the initialized size.
   *
   * Note that if the attribute is resident, we do not need to touch the page
   * cache at all.  This is because if the page cache page is not uptodate we
   * bring it uptodate later, when doing the write to the mft record since we
   * then already have the page mapped.  And if the page is uptodate, the
   * non-initialized region will already have been zeroed when the page was
   * brought uptodate and the region may in fact already have been overwritten
   * with new data via mmap() based writes, so we cannot just zero it.  And since
   * POSIX specifies that the behaviour of resizing a file whilst it is mmap()ped
   * is unspecified, we choose not to do zeroing and thus we do not need to touch

   * the page at all.  For a more detailed explanation see ntfs_truncate() in
   * fs/ntfs/inode.c.

   *

   * Return 0 on success and -errno on error.  In the case that an error is
   * encountered it is possible that the initialized size will already have been
   * incremented some way towards @new_init_size but it is guaranteed that if
   * this is the case, the necessary zeroing will also have happened and that all
   * metadata is self-consistent.
   *

   * Locking: i_mutex on the vfs inode corrseponsind to the ntfs inode @ni must be

   *	    held by the caller.

   */

  static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size)

  {
  	s64 old_init_size;
  	loff_t old_i_size;
  	pgoff_t index, end_index;
  	unsigned long flags;
  	struct inode *vi = VFS_I(ni);
  	ntfs_inode *base_ni;
  	MFT_RECORD *m = NULL;
  	ATTR_RECORD *a;
  	ntfs_attr_search_ctx *ctx = NULL;
  	struct address_space *mapping;
  	struct page *page = NULL;
  	u8 *kattr;
  	int err;
  	u32 attr_len;
  
  	read_lock_irqsave(&ni->size_lock, flags);
  	old_init_size = ni->initialized_size;
  	old_i_size = i_size_read(vi);
  	BUG_ON(new_init_size > ni->allocated_size);
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
  			"old_initialized_size 0x%llx, "
  			"new_initialized_size 0x%llx, i_size 0x%llx.",
  			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
  			(unsigned long long)old_init_size,
  			(unsigned long long)new_init_size, old_i_size);
  	if (!NInoAttr(ni))
  		base_ni = ni;
  	else
  		base_ni = ni->ext.base_ntfs_ino;
  	/* Use goto to reduce indentation and we need the label below anyway. */
  	if (NInoNonResident(ni))
  		goto do_non_resident_extend;
  	BUG_ON(old_init_size != old_i_size);
  	m = map_mft_record(base_ni);
  	if (IS_ERR(m)) {
  		err = PTR_ERR(m);
  		m = NULL;
  		goto err_out;
  	}
  	ctx = ntfs_attr_get_search_ctx(base_ni, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  			CASE_SENSITIVE, 0, NULL, 0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT)
  			err = -EIO;
  		goto err_out;
  	}
  	m = ctx->mrec;
  	a = ctx->attr;
  	BUG_ON(a->non_resident);
  	/* The total length of the attribute value. */
  	attr_len = le32_to_cpu(a->data.resident.value_length);
  	BUG_ON(old_i_size != (loff_t)attr_len);
  	/*
  	 * Do the zeroing in the mft record and update the attribute size in
  	 * the mft record.
  	 */
  	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
  	memset(kattr + attr_len, 0, new_init_size - attr_len);
  	a->data.resident.value_length = cpu_to_le32((u32)new_init_size);
  	/* Finally, update the sizes in the vfs and ntfs inodes. */
  	write_lock_irqsave(&ni->size_lock, flags);
  	i_size_write(vi, new_init_size);
  	ni->initialized_size = new_init_size;
  	write_unlock_irqrestore(&ni->size_lock, flags);
  	goto done;
  do_non_resident_extend:
  	/*
  	 * If the new initialized size @new_init_size exceeds the current file
  	 * size (vfs inode->i_size), we need to extend the file size to the
  	 * new initialized size.
  	 */
  	if (new_init_size > old_i_size) {
  		m = map_mft_record(base_ni);
  		if (IS_ERR(m)) {
  			err = PTR_ERR(m);
  			m = NULL;
  			goto err_out;
  		}
  		ctx = ntfs_attr_get_search_ctx(base_ni, m);
  		if (unlikely(!ctx)) {
  			err = -ENOMEM;
  			goto err_out;
  		}
  		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  				CASE_SENSITIVE, 0, NULL, 0, ctx);
  		if (unlikely(err)) {
  			if (err == -ENOENT)
  				err = -EIO;
  			goto err_out;
  		}
  		m = ctx->mrec;
  		a = ctx->attr;
  		BUG_ON(!a->non_resident);
  		BUG_ON(old_i_size != (loff_t)
  				sle64_to_cpu(a->data.non_resident.data_size));
  		a->data.non_resident.data_size = cpu_to_sle64(new_init_size);
  		flush_dcache_mft_record_page(ctx->ntfs_ino);
  		mark_mft_record_dirty(ctx->ntfs_ino);
  		/* Update the file size in the vfs inode. */
  		i_size_write(vi, new_init_size);
  		ntfs_attr_put_search_ctx(ctx);
  		ctx = NULL;
  		unmap_mft_record(base_ni);
  		m = NULL;
  	}
  	mapping = vi->i_mapping;
  	index = old_init_size >> PAGE_CACHE_SHIFT;
  	end_index = (new_init_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
  	do {
  		/*
  		 * Read the page.  If the page is not present, this will zero
  		 * the uninitialized regions for us.
  		 */

  		page = read_mapping_page(mapping, index, NULL);

  		if (IS_ERR(page)) {
  			err = PTR_ERR(page);
  			goto init_err_out;
  		}

  		if (unlikely(PageError(page))) {

  			page_cache_release(page);
  			err = -EIO;
  			goto init_err_out;
  		}
  		/*
  		 * Update the initialized size in the ntfs inode.  This is
  		 * enough to make ntfs_writepage() work.
  		 */
  		write_lock_irqsave(&ni->size_lock, flags);

  		ni->initialized_size = (s64)(index + 1) << PAGE_CACHE_SHIFT;

  		if (ni->initialized_size > new_init_size)
  			ni->initialized_size = new_init_size;
  		write_unlock_irqrestore(&ni->size_lock, flags);
  		/* Set the page dirty so it gets written out. */
  		set_page_dirty(page);
  		page_cache_release(page);
  		/*
  		 * Play nice with the vm and the rest of the system.  This is
  		 * very much needed as we can potentially be modifying the
  		 * initialised size from a very small value to a really huge
  		 * value, e.g.
  		 *	f = open(somefile, O_TRUNC);
  		 *	truncate(f, 10GiB);
  		 *	seek(f, 10GiB);
  		 *	write(f, 1);
  		 * And this would mean we would be marking dirty hundreds of
  		 * thousands of pages or as in the above example more than
  		 * two and a half million pages!
  		 *
  		 * TODO: For sparse pages could optimize this workload by using
  		 * the FsMisc / MiscFs page bit as a "PageIsSparse" bit.  This
  		 * would be set in readpage for sparse pages and here we would
  		 * not need to mark dirty any pages which have this bit set.
  		 * The only caveat is that we have to clear the bit everywhere
  		 * where we allocate any clusters that lie in the page or that
  		 * contain the page.
  		 *
  		 * TODO: An even greater optimization would be for us to only
  		 * call readpage() on pages which are not in sparse regions as
  		 * determined from the runlist.  This would greatly reduce the
  		 * number of pages we read and make dirty in the case of sparse
  		 * files.
  		 */
  		balance_dirty_pages_ratelimited(mapping);
  		cond_resched();
  	} while (++index < end_index);
  	read_lock_irqsave(&ni->size_lock, flags);
  	BUG_ON(ni->initialized_size != new_init_size);
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	/* Now bring in sync the initialized_size in the mft record. */
  	m = map_mft_record(base_ni);
  	if (IS_ERR(m)) {
  		err = PTR_ERR(m);
  		m = NULL;
  		goto init_err_out;
  	}
  	ctx = ntfs_attr_get_search_ctx(base_ni, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto init_err_out;
  	}
  	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  			CASE_SENSITIVE, 0, NULL, 0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT)
  			err = -EIO;
  		goto init_err_out;
  	}
  	m = ctx->mrec;
  	a = ctx->attr;
  	BUG_ON(!a->non_resident);
  	a->data.non_resident.initialized_size = cpu_to_sle64(new_init_size);
  done:
  	flush_dcache_mft_record_page(ctx->ntfs_ino);
  	mark_mft_record_dirty(ctx->ntfs_ino);
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(base_ni);
  	ntfs_debug("Done, initialized_size 0x%llx, i_size 0x%llx.",
  			(unsigned long long)new_init_size, i_size_read(vi));
  	return 0;
  init_err_out:
  	write_lock_irqsave(&ni->size_lock, flags);
  	ni->initialized_size = old_init_size;
  	write_unlock_irqrestore(&ni->size_lock, flags);
  err_out:
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(base_ni);
  	ntfs_debug("Failed.  Returning error code %i.", err);
  	return err;
  }
  
  /**
   * ntfs_fault_in_pages_readable -
   *
   * Fault a number of userspace pages into pagetables.
   *
   * Unlike include/linux/pagemap.h::fault_in_pages_readable(), this one copes
   * with more than two userspace pages as well as handling the single page case
   * elegantly.
   *
   * If you find this difficult to understand, then think of the while loop being
   * the following code, except that we do without the integer variable ret:
   *
   *	do {
   *		ret = __get_user(c, uaddr);
   *		uaddr += PAGE_SIZE;
   *	} while (!ret && uaddr < end);
   *
   * Note, the final __get_user() may well run out-of-bounds of the user buffer,
   * but _not_ out-of-bounds of the page the user buffer belongs to, and since
   * this is only a read and not a write, and since it is still in the same page,
   * it should not matter and this makes the code much simpler.
   */
  static inline void ntfs_fault_in_pages_readable(const char __user *uaddr,
  		int bytes)
  {
  	const char __user *end;
  	volatile char c;
  
  	/* Set @end to the first byte outside the last page we care about. */

  	end = (const char __user*)PAGE_ALIGN((unsigned long)uaddr + bytes);

  
  	while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
  		;
  }
  
  /**
   * ntfs_fault_in_pages_readable_iovec -
   *
   * Same as ntfs_fault_in_pages_readable() but operates on an array of iovecs.
   */
  static inline void ntfs_fault_in_pages_readable_iovec(const struct iovec *iov,
  		size_t iov_ofs, int bytes)
  {
  	do {
  		const char __user *buf;
  		unsigned len;
  
  		buf = iov->iov_base + iov_ofs;
  		len = iov->iov_len - iov_ofs;
  		if (len > bytes)
  			len = bytes;
  		ntfs_fault_in_pages_readable(buf, len);
  		bytes -= len;
  		iov++;
  		iov_ofs = 0;
  	} while (bytes);
  }
  
  /**
   * __ntfs_grab_cache_pages - obtain a number of locked pages
   * @mapping:	address space mapping from which to obtain page cache pages
   * @index:	starting index in @mapping at which to begin obtaining pages
   * @nr_pages:	number of page cache pages to obtain
   * @pages:	array of pages in which to return the obtained page cache pages
   * @cached_page: allocated but as yet unused page
   * @lru_pvec:	lru-buffering pagevec of caller
   *

   * Obtain @nr_pages locked page cache pages from the mapping @mapping and

   * starting at index @index.
   *

   * If a page is newly created, add it to lru list

   *
   * Note, the page locks are obtained in ascending page index order.
   */
  static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
  		pgoff_t index, const unsigned nr_pages, struct page **pages,

  		struct page **cached_page)

  {
  	int err, nr;
  
  	BUG_ON(!nr_pages);
  	err = nr = 0;
  	do {
  		pages[nr] = find_lock_page(mapping, index);
  		if (!pages[nr]) {
  			if (!*cached_page) {
  				*cached_page = page_cache_alloc(mapping);
  				if (unlikely(!*cached_page)) {
  					err = -ENOMEM;
  					goto err_out;
  				}
  			}

  			err = add_to_page_cache_lru(*cached_page, mapping, index,

  					GFP_KERNEL);
  			if (unlikely(err)) {
  				if (err == -EEXIST)
  					continue;
  				goto err_out;
  			}
  			pages[nr] = *cached_page;

  			*cached_page = NULL;
  		}
  		index++;
  		nr++;
  	} while (nr < nr_pages);
  out:
  	return err;
  err_out:
  	while (nr > 0) {
  		unlock_page(pages[--nr]);
  		page_cache_release(pages[nr]);
  	}
  	goto out;
  }
  
  static inline int ntfs_submit_bh_for_read(struct buffer_head *bh)
  {
  	lock_buffer(bh);
  	get_bh(bh);
  	bh->b_end_io = end_buffer_read_sync;
  	return submit_bh(READ, bh);
  }
  
  /**
   * ntfs_prepare_pages_for_non_resident_write - prepare pages for receiving data
   * @pages:	array of destination pages
   * @nr_pages:	number of pages in @pages
   * @pos:	byte position in file at which the write begins
   * @bytes:	number of bytes to be written
   *
   * This is called for non-resident attributes from ntfs_file_buffered_write()

   * with i_mutex held on the inode (@pages[0]->mapping->host).  There are

   * @nr_pages pages in @pages which are locked but not kmap()ped.  The source
   * data has not yet been copied into the @pages.
   * 
   * Need to fill any holes with actual clusters, allocate buffers if necessary,
   * ensure all the buffers are mapped, and bring uptodate any buffers that are
   * only partially being written to.
   *
   * If @nr_pages is greater than one, we are guaranteed that the cluster size is
   * greater than PAGE_CACHE_SIZE, that all pages in @pages are entirely inside
   * the same cluster and that they are the entirety of that cluster, and that
   * the cluster is sparse, i.e. we need to allocate a cluster to fill the hole.
   *
   * i_size is not to be modified yet.
   *
   * Return 0 on success or -errno on error.
   */
  static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
  		unsigned nr_pages, s64 pos, size_t bytes)
  {
  	VCN vcn, highest_vcn = 0, cpos, cend, bh_cpos, bh_cend;
  	LCN lcn;
  	s64 bh_pos, vcn_len, end, initialized_size;
  	sector_t lcn_block;
  	struct page *page;
  	struct inode *vi;
  	ntfs_inode *ni, *base_ni = NULL;
  	ntfs_volume *vol;
  	runlist_element *rl, *rl2;
  	struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
  	ntfs_attr_search_ctx *ctx = NULL;
  	MFT_RECORD *m = NULL;
  	ATTR_RECORD *a = NULL;
  	unsigned long flags;
  	u32 attr_rec_len = 0;
  	unsigned blocksize, u;
  	int err, mp_size;

  	bool rl_write_locked, was_hole, is_retry;

  	unsigned char blocksize_bits;
  	struct {
  		u8 runlist_merged:1;
  		u8 mft_attr_mapped:1;
  		u8 mp_rebuilt:1;
  		u8 attr_switched:1;
  	} status = { 0, 0, 0, 0 };
  
  	BUG_ON(!nr_pages);
  	BUG_ON(!pages);
  	BUG_ON(!*pages);
  	vi = pages[0]->mapping->host;
  	ni = NTFS_I(vi);
  	vol = ni->vol;
  	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "

  			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",

  			vi->i_ino, ni->type, pages[0]->index, nr_pages,
  			(long long)pos, bytes);

  	blocksize = vol->sb->s_blocksize;
  	blocksize_bits = vol->sb->s_blocksize_bits;

  	u = 0;
  	do {

  		page = pages[u];
  		BUG_ON(!page);

  		/*
  		 * create_empty_buffers() will create uptodate/dirty buffers if
  		 * the page is uptodate/dirty.
  		 */
  		if (!page_has_buffers(page)) {
  			create_empty_buffers(page, blocksize, 0);
  			if (unlikely(!page_has_buffers(page)))
  				return -ENOMEM;
  		}
  	} while (++u < nr_pages);

  	rl_write_locked = false;

  	rl = NULL;
  	err = 0;
  	vcn = lcn = -1;
  	vcn_len = 0;
  	lcn_block = -1;

  	was_hole = false;

  	cpos = pos >> vol->cluster_size_bits;
  	end = pos + bytes;
  	cend = (end + vol->cluster_size - 1) >> vol->cluster_size_bits;
  	/*
  	 * Loop over each page and for each page over each buffer.  Use goto to
  	 * reduce indentation.
  	 */
  	u = 0;
  do_next_page:
  	page = pages[u];
  	bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
  	bh = head = page_buffers(page);
  	do {
  		VCN cdelta;
  		s64 bh_end;
  		unsigned bh_cofs;
  
  		/* Clear buffer_new on all buffers to reinitialise state. */
  		if (buffer_new(bh))
  			clear_buffer_new(bh);
  		bh_end = bh_pos + blocksize;
  		bh_cpos = bh_pos >> vol->cluster_size_bits;
  		bh_cofs = bh_pos & vol->cluster_size_mask;
  		if (buffer_mapped(bh)) {
  			/*
  			 * The buffer is already mapped.  If it is uptodate,
  			 * ignore it.
  			 */
  			if (buffer_uptodate(bh))
  				continue;
  			/*
  			 * The buffer is not uptodate.  If the page is uptodate
  			 * set the buffer uptodate and otherwise ignore it.
  			 */
  			if (PageUptodate(page)) {
  				set_buffer_uptodate(bh);
  				continue;
  			}
  			/*
  			 * Neither the page nor the buffer are uptodate.  If
  			 * the buffer is only partially being written to, we
  			 * need to read it in before the write, i.e. now.
  			 */
  			if ((bh_pos < pos && bh_end > pos) ||
  					(bh_pos < end && bh_end > end)) {
  				/*
  				 * If the buffer is fully or partially within
  				 * the initialized size, do an actual read.
  				 * Otherwise, simply zero the buffer.
  				 */
  				read_lock_irqsave(&ni->size_lock, flags);
  				initialized_size = ni->initialized_size;
  				read_unlock_irqrestore(&ni->size_lock, flags);
  				if (bh_pos < initialized_size) {
  					ntfs_submit_bh_for_read(bh);
  					*wait_bh++ = bh;
  				} else {

  					zero_user(page, bh_offset(bh),
  							blocksize);

  					set_buffer_uptodate(bh);
  				}
  			}
  			continue;
  		}
  		/* Unmapped buffer.  Need to map it. */
  		bh->b_bdev = vol->sb->s_bdev;
  		/*
  		 * If the current buffer is in the same clusters as the map
  		 * cache, there is no need to check the runlist again.  The
  		 * map cache is made up of @vcn, which is the first cached file
  		 * cluster, @vcn_len which is the number of cached file
  		 * clusters, @lcn is the device cluster corresponding to @vcn,
  		 * and @lcn_block is the block number corresponding to @lcn.
  		 */
  		cdelta = bh_cpos - vcn;
  		if (likely(!cdelta || (cdelta > 0 && cdelta < vcn_len))) {
  map_buffer_cached:
  			BUG_ON(lcn < 0);
  			bh->b_blocknr = lcn_block +
  					(cdelta << (vol->cluster_size_bits -
  					blocksize_bits)) +
  					(bh_cofs >> blocksize_bits);
  			set_buffer_mapped(bh);
  			/*
  			 * If the page is uptodate so is the buffer.  If the
  			 * buffer is fully outside the write, we ignore it if
  			 * it was already allocated and we mark it dirty so it
  			 * gets written out if we allocated it.  On the other
  			 * hand, if we allocated the buffer but we are not
  			 * marking it dirty we set buffer_new so we can do
  			 * error recovery.
  			 */
  			if (PageUptodate(page)) {
  				if (!buffer_uptodate(bh))
  					set_buffer_uptodate(bh);
  				if (unlikely(was_hole)) {
  					/* We allocated the buffer. */
  					unmap_underlying_metadata(bh->b_bdev,
  							bh->b_blocknr);
  					if (bh_end <= pos || bh_pos >= end)
  						mark_buffer_dirty(bh);
  					else
  						set_buffer_new(bh);
  				}
  				continue;
  			}
  			/* Page is _not_ uptodate. */
  			if (likely(!was_hole)) {
  				/*
  				 * Buffer was already allocated.  If it is not
  				 * uptodate and is only partially being written
  				 * to, we need to read it in before the write,
  				 * i.e. now.
  				 */

  				if (!buffer_uptodate(bh) && bh_pos < end &&
  						bh_end > pos &&
  						(bh_pos < pos ||
  						bh_end > end)) {

  					/*
  					 * If the buffer is fully or partially
  					 * within the initialized size, do an
  					 * actual read.  Otherwise, simply zero
  					 * the buffer.
  					 */
  					read_lock_irqsave(&ni->size_lock,
  							flags);
  					initialized_size = ni->initialized_size;
  					read_unlock_irqrestore(&ni->size_lock,
  							flags);
  					if (bh_pos < initialized_size) {
  						ntfs_submit_bh_for_read(bh);
  						*wait_bh++ = bh;
  					} else {

  						zero_user(page, bh_offset(bh),
  								blocksize);

  						set_buffer_uptodate(bh);
  					}
  				}
  				continue;
  			}
  			/* We allocated the buffer. */
  			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
  			/*
  			 * If the buffer is fully outside the write, zero it,
  			 * set it uptodate, and mark it dirty so it gets
  			 * written out.  If it is partially being written to,
  			 * zero region surrounding the write but leave it to
  			 * commit write to do anything else.  Finally, if the
  			 * buffer is fully being overwritten, do nothing.
  			 */
  			if (bh_end <= pos || bh_pos >= end) {
  				if (!buffer_uptodate(bh)) {

  					zero_user(page, bh_offset(bh),
  							blocksize);

  					set_buffer_uptodate(bh);
  				}
  				mark_buffer_dirty(bh);
  				continue;
  			}
  			set_buffer_new(bh);
  			if (!buffer_uptodate(bh) &&
  					(bh_pos < pos || bh_end > end)) {
  				u8 *kaddr;
  				unsigned pofs;
  					
  				kaddr = kmap_atomic(page, KM_USER0);
  				if (bh_pos < pos) {
  					pofs = bh_pos & ~PAGE_CACHE_MASK;
  					memset(kaddr + pofs, 0, pos - bh_pos);
  				}
  				if (bh_end > end) {
  					pofs = end & ~PAGE_CACHE_MASK;
  					memset(kaddr + pofs, 0, bh_end - end);
  				}
  				kunmap_atomic(kaddr, KM_USER0);
  				flush_dcache_page(page);
  			}
  			continue;
  		}
  		/*
  		 * Slow path: this is the first buffer in the cluster.  If it
  		 * is outside allocated size and is not uptodate, zero it and
  		 * set it uptodate.
  		 */
  		read_lock_irqsave(&ni->size_lock, flags);
  		initialized_size = ni->allocated_size;
  		read_unlock_irqrestore(&ni->size_lock, flags);
  		if (bh_pos > initialized_size) {
  			if (PageUptodate(page)) {
  				if (!buffer_uptodate(bh))
  					set_buffer_uptodate(bh);
  			} else if (!buffer_uptodate(bh)) {

  				zero_user(page, bh_offset(bh), blocksize);

  				set_buffer_uptodate(bh);
  			}
  			continue;
  		}

  		is_retry = false;

  		if (!rl) {
  			down_read(&ni->runlist.lock);
  retry_remap:
  			rl = ni->runlist.rl;
  		}
  		if (likely(rl != NULL)) {
  			/* Seek to element containing target cluster. */
  			while (rl->length && rl[1].vcn <= bh_cpos)
  				rl++;
  			lcn = ntfs_rl_vcn_to_lcn(rl, bh_cpos);
  			if (likely(lcn >= 0)) {
  				/*
  				 * Successful remap, setup the map cache and
  				 * use that to deal with the buffer.
  				 */

  				was_hole = false;

  				vcn = bh_cpos;
  				vcn_len = rl[1].vcn - vcn;
  				lcn_block = lcn << (vol->cluster_size_bits -
  						blocksize_bits);

  				cdelta = 0;

  				/*

  				 * If the number of remaining clusters touched
  				 * by the write is smaller or equal to the
  				 * number of cached clusters, unlock the
  				 * runlist as the map cache will be used from
  				 * now on.

  				 */
  				if (likely(vcn + vcn_len >= cend)) {
  					if (rl_write_locked) {
  						up_write(&ni->runlist.lock);

  						rl_write_locked = false;

  					} else
  						up_read(&ni->runlist.lock);
  					rl = NULL;
  				}
  				goto map_buffer_cached;
  			}
  		} else
  			lcn = LCN_RL_NOT_MAPPED;
  		/*
  		 * If it is not a hole and not out of bounds, the runlist is
  		 * probably unmapped so try to map it now.
  		 */
  		if (unlikely(lcn != LCN_HOLE && lcn != LCN_ENOENT)) {
  			if (likely(!is_retry && lcn == LCN_RL_NOT_MAPPED)) {
  				/* Attempt to map runlist. */
  				if (!rl_write_locked) {
  					/*
  					 * We need the runlist locked for
  					 * writing, so if it is locked for
  					 * reading relock it now and retry in
  					 * case it changed whilst we dropped
  					 * the lock.
  					 */
  					up_read(&ni->runlist.lock);
  					down_write(&ni->runlist.lock);

  					rl_write_locked = true;

  					goto retry_remap;
  				}
  				err = ntfs_map_runlist_nolock(ni, bh_cpos,
  						NULL);
  				if (likely(!err)) {

  					is_retry = true;

  					goto retry_remap;
  				}
  				/*
  				 * If @vcn is out of bounds, pretend @lcn is
  				 * LCN_ENOENT.  As long as the buffer is out
  				 * of bounds this will work fine.
  				 */
  				if (err == -ENOENT) {
  					lcn = LCN_ENOENT;
  					err = 0;
  					goto rl_not_mapped_enoent;
  				}
  			} else
  				err = -EIO;
  			/* Failed to map the buffer, even after retrying. */
  			bh->b_blocknr = -1;
  			ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
  					"attribute type 0x%x, vcn 0x%llx, "
  					"vcn offset 0x%x, because its "
  					"location on disk could not be "
  					"determined%s (error code %i).",
  					ni->mft_no, ni->type,
  					(unsigned long long)bh_cpos,
  					(unsigned)bh_pos &
  					vol->cluster_size_mask,
  					is_retry ? " even after retrying" : "",
  					err);
  			break;
  		}
  rl_not_mapped_enoent:
  		/*
  		 * The buffer is in a hole or out of bounds.  We need to fill
  		 * the hole, unless the buffer is in a cluster which is not
  		 * touched by the write, in which case we just leave the buffer
  		 * unmapped.  This can only happen when the cluster size is
  		 * less than the page cache size.
  		 */
  		if (unlikely(vol->cluster_size < PAGE_CACHE_SIZE)) {
  			bh_cend = (bh_end + vol->cluster_size - 1) >>
  					vol->cluster_size_bits;
  			if ((bh_cend <= cpos || bh_cpos >= cend)) {
  				bh->b_blocknr = -1;
  				/*
  				 * If the buffer is uptodate we skip it.  If it
  				 * is not but the page is uptodate, we can set
  				 * the buffer uptodate.  If the page is not
  				 * uptodate, we can clear the buffer and set it
  				 * uptodate.  Whether this is worthwhile is
  				 * debatable and this could be removed.
  				 */
  				if (PageUptodate(page)) {
  					if (!buffer_uptodate(bh))
  						set_buffer_uptodate(bh);
  				} else if (!buffer_uptodate(bh)) {

  					zero_user(page, bh_offset(bh),
  						blocksize);

  					set_buffer_uptodate(bh);
  				}
  				continue;
  			}
  		}
  		/*
  		 * Out of bounds buffer is invalid if it was not really out of
  		 * bounds.
  		 */
  		BUG_ON(lcn != LCN_HOLE);
  		/*
  		 * We need the runlist locked for writing, so if it is locked
  		 * for reading relock it now and retry in case it changed
  		 * whilst we dropped the lock.
  		 */
  		BUG_ON(!rl);
  		if (!rl_write_locked) {
  			up_read(&ni->runlist.lock);
  			down_write(&ni->runlist.lock);

  			rl_write_locked = true;

  			goto retry_remap;
  		}
  		/* Find the previous last allocated cluster. */
  		BUG_ON(rl->lcn != LCN_HOLE);
  		lcn = -1;
  		rl2 = rl;
  		while (--rl2 >= ni->runlist.rl) {
  			if (rl2->lcn >= 0) {
  				lcn = rl2->lcn + rl2->length;
  				break;
  			}
  		}
  		rl2 = ntfs_cluster_alloc(vol, bh_cpos, 1, lcn, DATA_ZONE,

  				false);

  		if (IS_ERR(rl2)) {
  			err = PTR_ERR(rl2);
  			ntfs_debug("Failed to allocate cluster, error code %i.",
  					err);
  			break;
  		}
  		lcn = rl2->lcn;
  		rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
  		if (IS_ERR(rl)) {
  			err = PTR_ERR(rl);
  			if (err != -ENOMEM)
  				err = -EIO;
  			if (ntfs_cluster_free_from_rl(vol, rl2)) {
  				ntfs_error(vol->sb, "Failed to release "
  						"allocated cluster in error "
  						"code path.  Run chkdsk to "
  						"recover the lost cluster.");
  				NVolSetErrors(vol);
  			}
  			ntfs_free(rl2);
  			break;
  		}
  		ni->runlist.rl = rl;
  		status.runlist_merged = 1;

  		ntfs_debug("Allocated cluster, lcn 0x%llx.",
  				(unsigned long long)lcn);

  		/* Map and lock the mft record and get the attribute record. */
  		if (!NInoAttr(ni))
  			base_ni = ni;
  		else
  			base_ni = ni->ext.base_ntfs_ino;
  		m = map_mft_record(base_ni);
  		if (IS_ERR(m)) {
  			err = PTR_ERR(m);
  			break;
  		}
  		ctx = ntfs_attr_get_search_ctx(base_ni, m);
  		if (unlikely(!ctx)) {
  			err = -ENOMEM;
  			unmap_mft_record(base_ni);
  			break;
  		}
  		status.mft_attr_mapped = 1;
  		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx);
  		if (unlikely(err)) {
  			if (err == -ENOENT)
  				err = -EIO;
  			break;
  		}
  		m = ctx->mrec;
  		a = ctx->attr;
  		/*
  		 * Find the runlist element with which the attribute extent
  		 * starts.  Note, we cannot use the _attr_ version because we
  		 * have mapped the mft record.  That is ok because we know the
  		 * runlist fragment must be mapped already to have ever gotten
  		 * here, so we can just use the _rl_ version.
  		 */
  		vcn = sle64_to_cpu(a->data.non_resident.lowest_vcn);
  		rl2 = ntfs_rl_find_vcn_nolock(rl, vcn);
  		BUG_ON(!rl2);
  		BUG_ON(!rl2->length);
  		BUG_ON(rl2->lcn < LCN_HOLE);
  		highest_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
  		/*
  		 * If @highest_vcn is zero, calculate the real highest_vcn
  		 * (which can really be zero).
  		 */
  		if (!highest_vcn)
  			highest_vcn = (sle64_to_cpu(
  					a->data.non_resident.allocated_size) >>
  					vol->cluster_size_bits) - 1;
  		/*
  		 * Determine the size of the mapping pairs array for the new
  		 * extent, i.e. the old extent with the hole filled.
  		 */
  		mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, vcn,
  				highest_vcn);
  		if (unlikely(mp_size <= 0)) {
  			if (!(err = mp_size))
  				err = -EIO;
  			ntfs_debug("Failed to get size for mapping pairs "
  					"array, error code %i.", err);
  			break;
  		}
  		/*
  		 * Resize the attribute record to fit the new mapping pairs
  		 * array.
  		 */
  		attr_rec_len = le32_to_cpu(a->length);
  		err = ntfs_attr_record_resize(m, a, mp_size + le16_to_cpu(
  				a->data.non_resident.mapping_pairs_offset));
  		if (unlikely(err)) {
  			BUG_ON(err != -ENOSPC);
  			// TODO: Deal with this by using the current attribute
  			// and fill it with as much of the mapping pairs
  			// array as possible.  Then loop over each attribute
  			// extent rewriting the mapping pairs arrays as we go
  			// along and if when we reach the end we have not
  			// enough space, try to resize the last attribute
  			// extent and if even that fails, add a new attribute
  			// extent.
  			// We could also try to resize at each step in the hope
  			// that we will not need to rewrite every single extent.
  			// Note, we may need to decompress some extents to fill
  			// the runlist as we are walking the extents...
  			ntfs_error(vol->sb, "Not enough space in the mft "
  					"record for the extended attribute "
  					"record.  This case is not "
  					"implemented yet.");
  			err = -EOPNOTSUPP;
  			break ;
  		}
  		status.mp_rebuilt = 1;
  		/*
  		 * Generate the mapping pairs array directly into the attribute
  		 * record.
  		 */
  		err = ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
  				a->data.non_resident.mapping_pairs_offset),
  				mp_size, rl2, vcn, highest_vcn, NULL);
  		if (unlikely(err)) {
  			ntfs_error(vol->sb, "Cannot fill hole in inode 0x%lx, "
  					"attribute type 0x%x, because building "
  					"the mapping pairs failed with error "
  					"code %i.", vi->i_ino,
  					(unsigned)le32_to_cpu(ni->type), err);
  			err = -EIO;
  			break;
  		}
  		/* Update the highest_vcn but only if it was not set. */
  		if (unlikely(!a->data.non_resident.highest_vcn))
  			a->data.non_resident.highest_vcn =
  					cpu_to_sle64(highest_vcn);
  		/*
  		 * If the attribute is sparse/compressed, update the compressed
  		 * size in the ntfs_inode structure and the attribute record.
  		 */
  		if (likely(NInoSparse(ni) || NInoCompressed(ni))) {
  			/*
  			 * If we are not in the first attribute extent, switch
  			 * to it, but first ensure the changes will make it to
  			 * disk later.
  			 */
  			if (a->data.non_resident.lowest_vcn) {
  				flush_dcache_mft_record_page(ctx->ntfs_ino);
  				mark_mft_record_dirty(ctx->ntfs_ino);
  				ntfs_attr_reinit_search_ctx(ctx);
  				err = ntfs_attr_lookup(ni->type, ni->name,
  						ni->name_len, CASE_SENSITIVE,
  						0, NULL, 0, ctx);
  				if (unlikely(err)) {
  					status.attr_switched = 1;
  					break;
  				}
  				/* @m is not used any more so do not set it. */
  				a = ctx->attr;
  			}
  			write_lock_irqsave(&ni->size_lock, flags);
  			ni->itype.compressed.size += vol->cluster_size;
  			a->data.non_resident.compressed_size =
  					cpu_to_sle64(ni->itype.compressed.size);
  			write_unlock_irqrestore(&ni->size_lock, flags);
  		}
  		/* Ensure the changes make it to disk. */
  		flush_dcache_mft_record_page(ctx->ntfs_ino);
  		mark_mft_record_dirty(ctx->ntfs_ino);
  		ntfs_attr_put_search_ctx(ctx);
  		unmap_mft_record(base_ni);
  		/* Successfully filled the hole. */
  		status.runlist_merged = 0;
  		status.mft_attr_mapped = 0;
  		status.mp_rebuilt = 0;
  		/* Setup the map cache and use that to deal with the buffer. */

  		was_hole = true;

  		vcn = bh_cpos;
  		vcn_len = 1;
  		lcn_block = lcn << (vol->cluster_size_bits - blocksize_bits);
  		cdelta = 0;
  		/*
  		 * If the number of remaining clusters in the @pages is smaller
  		 * or equal to the number of cached clusters, unlock the
  		 * runlist as the map cache will be used from now on.
  		 */
  		if (likely(vcn + vcn_len >= cend)) {
  			up_write(&ni->runlist.lock);

  			rl_write_locked = false;

  			rl = NULL;
  		}
  		goto map_buffer_cached;
  	} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
  	/* If there are no errors, do the next page. */
  	if (likely(!err && ++u < nr_pages))
  		goto do_next_page;
  	/* If there are no errors, release the runlist lock if we took it. */
  	if (likely(!err)) {
  		if (unlikely(rl_write_locked)) {
  			up_write(&ni->runlist.lock);

  			rl_write_locked = false;

  		} else if (unlikely(rl))
  			up_read(&ni->runlist.lock);
  		rl = NULL;
  	}
  	/* If we issued read requests, let them complete. */
  	read_lock_irqsave(&ni->size_lock, flags);
  	initialized_size = ni->initialized_size;
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	while (wait_bh > wait) {
  		bh = *--wait_bh;
  		wait_on_buffer(bh);
  		if (likely(buffer_uptodate(bh))) {
  			page = bh->b_page;
  			bh_pos = ((s64)page->index << PAGE_CACHE_SHIFT) +
  					bh_offset(bh);
  			/*
  			 * If the buffer overflows the initialized size, need
  			 * to zero the overflowing region.
  			 */
  			if (unlikely(bh_pos + blocksize > initialized_size)) {

  				int ofs = 0;
  
  				if (likely(bh_pos < initialized_size))
  					ofs = initialized_size - bh_pos;

  				zero_user_segment(page, bh_offset(bh) + ofs,
  						blocksize);

  			}
  		} else /* if (unlikely(!buffer_uptodate(bh))) */
  			err = -EIO;
  	}
  	if (likely(!err)) {
  		/* Clear buffer_new on all buffers. */
  		u = 0;
  		do {
  			bh = head = page_buffers(pages[u]);
  			do {
  				if (buffer_new(bh))
  					clear_buffer_new(bh);
  			} while ((bh = bh->b_this_page) != head);
  		} while (++u < nr_pages);
  		ntfs_debug("Done.");
  		return err;
  	}
  	if (status.attr_switched) {
  		/* Get back to the attribute extent we modified. */
  		ntfs_attr_reinit_search_ctx(ctx);
  		if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx)) {
  			ntfs_error(vol->sb, "Failed to find required "
  					"attribute extent of attribute in "
  					"error code path.  Run chkdsk to "
  					"recover.");
  			write_lock_irqsave(&ni->size_lock, flags);
  			ni->itype.compressed.size += vol->cluster_size;
  			write_unlock_irqrestore(&ni->size_lock, flags);
  			flush_dcache_mft_record_page(ctx->ntfs_ino);
  			mark_mft_record_dirty(ctx->ntfs_ino);
  			/*
  			 * The only thing that is now wrong is the compressed
  			 * size of the base attribute extent which chkdsk
  			 * should be able to fix.
  			 */
  			NVolSetErrors(vol);
  		} else {
  			m = ctx->mrec;
  			a = ctx->attr;
  			status.attr_switched = 0;
  		}
  	}
  	/*
  	 * If the runlist has been modified, need to restore it by punching a
  	 * hole into it and we then need to deallocate the on-disk cluster as
  	 * well.  Note, we only modify the runlist if we are able to generate a
  	 * new mapping pairs array, i.e. only when the mapped attribute extent
  	 * is not switched.
  	 */
  	if (status.runlist_merged && !status.attr_switched) {
  		BUG_ON(!rl_write_locked);
  		/* Make the file cluster we allocated sparse in the runlist. */
  		if (ntfs_rl_punch_nolock(vol, &ni->runlist, bh_cpos, 1)) {
  			ntfs_error(vol->sb, "Failed to punch hole into "
  					"attribute runlist in error code "
  					"path.  Run chkdsk to recover the "
  					"lost cluster.");

  			NVolSetErrors(vol);
  		} else /* if (success) */ {
  			status.runlist_merged = 0;
  			/*
  			 * Deallocate the on-disk cluster we allocated but only
  			 * if we succeeded in punching its vcn out of the
  			 * runlist.
  			 */
  			down_write(&vol->lcnbmp_lock);
  			if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
  				ntfs_error(vol->sb, "Failed to release "
  						"allocated cluster in error "
  						"code path.  Run chkdsk to "
  						"recover the lost cluster.");
  				NVolSetErrors(vol);
  			}
  			up_write(&vol->lcnbmp_lock);
  		}
  	}
  	/*
  	 * Resize the attribute record to its old size and rebuild the mapping
  	 * pairs array.  Note, we only can do this if the runlist has been
  	 * restored to its old state which also implies that the mapped
  	 * attribute extent is not switched.
  	 */
  	if (status.mp_rebuilt && !status.runlist_merged) {
  		if (ntfs_attr_record_resize(m, a, attr_rec_len)) {
  			ntfs_error(vol->sb, "Failed to restore attribute "
  					"record in error code path.  Run "
  					"chkdsk to recover.");

  			NVolSetErrors(vol);
  		} else /* if (success) */ {
  			if (ntfs_mapping_pairs_build(vol, (u8*)a +
  					le16_to_cpu(a->data.non_resident.
  					mapping_pairs_offset), attr_rec_len -
  					le16_to_cpu(a->data.non_resident.
  					mapping_pairs_offset), ni->runlist.rl,
  					vcn, highest_vcn, NULL)) {
  				ntfs_error(vol->sb, "Failed to restore "
  						"mapping pairs array in error "
  						"code path.  Run chkdsk to "
  						"recover.");

  				NVolSetErrors(vol);
  			}
  			flush_dcache_mft_record_page(ctx->ntfs_ino);
  			mark_mft_record_dirty(ctx->ntfs_ino);
  		}
  	}
  	/* Release the mft record and the attribute. */
  	if (status.mft_attr_mapped) {
  		ntfs_attr_put_search_ctx(ctx);
  		unmap_mft_record(base_ni);
  	}
  	/* Release the runlist lock. */
  	if (rl_write_locked)
  		up_write(&ni->runlist.lock);
  	else if (rl)
  		up_read(&ni->runlist.lock);
  	/*
  	 * Zero out any newly allocated blocks to avoid exposing stale data.
  	 * If BH_New is set, we know that the block was newly allocated above
  	 * and that it has not been fully zeroed and marked dirty yet.
  	 */
  	nr_pages = u;
  	u = 0;
  	end = bh_cpos << vol->cluster_size_bits;
  	do {
  		page = pages[u];
  		bh = head = page_buffers(page);
  		do {
  			if (u == nr_pages &&
  					((s64)page->index << PAGE_CACHE_SHIFT) +
  					bh_offset(bh) >= end)
  				break;
  			if (!buffer_new(bh))
  				continue;
  			clear_buffer_new(bh);
  			if (!buffer_uptodate(bh)) {
  				if (PageUptodate(page))
  					set_buffer_uptodate(bh);
  				else {

  					zero_user(page, bh_offset(bh),
  							blocksize);

  					set_buffer_uptodate(bh);
  				}
  			}
  			mark_buffer_dirty(bh);
  		} while ((bh = bh->b_this_page) != head);
  	} while (++u <= nr_pages);
  	ntfs_error(vol->sb, "Failed.  Returning error code %i.", err);
  	return err;
  }
  
  /*
   * Copy as much as we can into the pages and return the number of bytes which

   * were successfully copied.  If a fault is encountered then clear the pages

   * out to (ofs + bytes) and return the number of bytes which were copied.
   */
  static inline size_t ntfs_copy_from_user(struct page **pages,
  		unsigned nr_pages, unsigned ofs, const char __user *buf,
  		size_t bytes)
  {
  	struct page **last_page = pages + nr_pages;

  	char *addr;

  	size_t total = 0;
  	unsigned len;
  	int left;
  
  	do {
  		len = PAGE_CACHE_SIZE - ofs;
  		if (len > bytes)
  			len = bytes;

  		addr = kmap_atomic(*pages, KM_USER0);
  		left = __copy_from_user_inatomic(addr + ofs, buf, len);
  		kunmap_atomic(addr, KM_USER0);

  		if (unlikely(left)) {
  			/* Do it the slow way. */

  			addr = kmap(*pages);
  			left = __copy_from_user(addr + ofs, buf, len);

  			kunmap(*pages);
  			if (unlikely(left))
  				goto err_out;
  		}
  		total += len;
  		bytes -= len;
  		if (!bytes)
  			break;
  		buf += len;
  		ofs = 0;
  	} while (++pages < last_page);
  out:
  	return total;
  err_out:
  	total += len - left;
  	/* Zero the rest of the target like __copy_from_user(). */
  	while (++pages < last_page) {
  		bytes -= len;
  		if (!bytes)
  			break;
  		len = PAGE_CACHE_SIZE;
  		if (len > bytes)
  			len = bytes;

  		zero_user(*pages, 0, len);

  	}
  	goto out;
  }

  static size_t __ntfs_copy_from_user_iovec_inatomic(char *vaddr,

  		const struct iovec *iov, size_t iov_ofs, size_t bytes)
  {
  	size_t total = 0;
  
  	while (1) {
  		const char __user *buf = iov->iov_base + iov_ofs;
  		unsigned len;
  		size_t left;
  
  		len = iov->iov_len - iov_ofs;
  		if (len > bytes)
  			len = bytes;
  		left = __copy_from_user_inatomic(vaddr, buf, len);
  		total += len;
  		bytes -= len;
  		vaddr += len;
  		if (unlikely(left)) {

  			total -= left;
  			break;
  		}
  		if (!bytes)
  			break;
  		iov++;
  		iov_ofs = 0;
  	}
  	return total;
  }
  
  static inline void ntfs_set_next_iovec(const struct iovec **iovp,
  		size_t *iov_ofsp, size_t bytes)
  {
  	const struct iovec *iov = *iovp;
  	size_t iov_ofs = *iov_ofsp;
  
  	while (bytes) {
  		unsigned len;
  
  		len = iov->iov_len - iov_ofs;
  		if (len > bytes)
  			len = bytes;
  		bytes -= len;
  		iov_ofs += len;
  		if (iov->iov_len == iov_ofs) {
  			iov++;
  			iov_ofs = 0;
  		}
  	}
  	*iovp = iov;
  	*iov_ofsp = iov_ofs;
  }
  
  /*
   * This has the same side-effects and return value as ntfs_copy_from_user().
   * The difference is that on a fault we need to memset the remainder of the
   * pages (out to offset + bytes), to emulate ntfs_copy_from_user()'s
   * single-segment behaviour.
   *

   * We call the same helper (__ntfs_copy_from_user_iovec_inatomic()) both when
   * atomic and when not atomic.  This is ok because it calls
   * __copy_from_user_inatomic() and it is ok to call this when non-atomic.  In
   * fact, the only difference between __copy_from_user_inatomic() and

   * __copy_from_user() is that the latter calls might_sleep() and the former

   * should not zero the tail of the buffer on error.  And on many architectures
   * __copy_from_user_inatomic() is just defined to __copy_from_user() so it
   * makes no difference at all on those architectures.

   */
  static inline size_t ntfs_copy_from_user_iovec(struct page **pages,
  		unsigned nr_pages, unsigned ofs, const struct iovec **iov,
  		size_t *iov_ofs, size_t bytes)
  {
  	struct page **last_page = pages + nr_pages;

  	char *addr;

  	size_t copied, len, total = 0;
  
  	do {
  		len = PAGE_CACHE_SIZE - ofs;
  		if (len > bytes)
  			len = bytes;

  		addr = kmap_atomic(*pages, KM_USER0);
  		copied = __ntfs_copy_from_user_iovec_inatomic(addr + ofs,

  				*iov, *iov_ofs, len);

  		kunmap_atomic(addr, KM_USER0);

  		if (unlikely(copied != len)) {
  			/* Do it the slow way. */

  			addr = kmap(*pages);

  			copied = __ntfs_copy_from_user_iovec_inatomic(addr +
  					ofs, *iov, *iov_ofs, len);

  			if (unlikely(copied != len))
  				goto err_out;

  			kunmap(*pages);

  		}
  		total += len;

  		ntfs_set_next_iovec(iov, iov_ofs, len);

  		bytes -= len;
  		if (!bytes)
  			break;

  		ofs = 0;
  	} while (++pages < last_page);
  out:
  	return total;
  err_out:

  	BUG_ON(copied > len);

  	/* Zero the rest of the target like __copy_from_user(). */

  	memset(addr + ofs + copied, 0, len - copied);
  	kunmap(*pages);
  	total += copied;
  	ntfs_set_next_iovec(iov, iov_ofs, copied);

  	while (++pages < last_page) {
  		bytes -= len;
  		if (!bytes)
  			break;
  		len = PAGE_CACHE_SIZE;
  		if (len > bytes)
  			len = bytes;

  		zero_user(*pages, 0, len);

  	}
  	goto out;
  }
  
  static inline void ntfs_flush_dcache_pages(struct page **pages,
  		unsigned nr_pages)
  {
  	BUG_ON(!nr_pages);

  	/*
  	 * Warning: Do not do the decrement at the same time as the call to
  	 * flush_dcache_page() because it is a NULL macro on i386 and hence the
  	 * decrement never happens so the loop never terminates.
  	 */

  	do {

  		--nr_pages;

  		flush_dcache_page(pages[nr_pages]);

  	} while (nr_pages > 0);

  }
  
  /**
   * ntfs_commit_pages_after_non_resident_write - commit the received data
   * @pages:	array of destination pages
   * @nr_pages:	number of pages in @pages
   * @pos:	byte position in file at which the write begins
   * @bytes:	number of bytes to be written
   *
   * See description of ntfs_commit_pages_after_write(), below.
   */
  static inline int ntfs_commit_pages_after_non_resident_write(
  		struct page **pages, const unsigned nr_pages,
  		s64 pos, size_t bytes)
  {
  	s64 end, initialized_size;
  	struct inode *vi;
  	ntfs_inode *ni, *base_ni;
  	struct buffer_head *bh, *head;
  	ntfs_attr_search_ctx *ctx;
  	MFT_RECORD *m;
  	ATTR_RECORD *a;
  	unsigned long flags;
  	unsigned blocksize, u;
  	int err;
  
  	vi = pages[0]->mapping->host;
  	ni = NTFS_I(vi);

  	blocksize = vi->i_sb->s_blocksize;

  	end = pos + bytes;
  	u = 0;
  	do {
  		s64 bh_pos;
  		struct page *page;

  		bool partial;

  
  		page = pages[u];
  		bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
  		bh = head = page_buffers(page);

  		partial = false;

  		do {
  			s64 bh_end;
  
  			bh_end = bh_pos + blocksize;
  			if (bh_end <= pos || bh_pos >= end) {
  				if (!buffer_uptodate(bh))

  					partial = true;

  			} else {
  				set_buffer_uptodate(bh);
  				mark_buffer_dirty(bh);
  			}
  		} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
  		/*
  		 * If all buffers are now uptodate but the page is not, set the
  		 * page uptodate.
  		 */
  		if (!partial && !PageUptodate(page))
  			SetPageUptodate(page);
  	} while (++u < nr_pages);
  	/*
  	 * Finally, if we do not need to update initialized_size or i_size we
  	 * are finished.
  	 */
  	read_lock_irqsave(&ni->size_lock, flags);
  	initialized_size = ni->initialized_size;
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	if (end <= initialized_size) {
  		ntfs_debug("Done.");
  		return 0;
  	}
  	/*
  	 * Update initialized_size/i_size as appropriate, both in the inode and
  	 * the mft record.
  	 */
  	if (!NInoAttr(ni))
  		base_ni = ni;
  	else
  		base_ni = ni->ext.base_ntfs_ino;
  	/* Map, pin, and lock the mft record. */
  	m = map_mft_record(base_ni);
  	if (IS_ERR(m)) {
  		err = PTR_ERR(m);
  		m = NULL;
  		ctx = NULL;
  		goto err_out;
  	}
  	BUG_ON(!NInoNonResident(ni));
  	ctx = ntfs_attr_get_search_ctx(base_ni, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  			CASE_SENSITIVE, 0, NULL, 0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT)
  			err = -EIO;
  		goto err_out;
  	}
  	a = ctx->attr;
  	BUG_ON(!a->non_resident);
  	write_lock_irqsave(&ni->size_lock, flags);
  	BUG_ON(end > ni->allocated_size);
  	ni->initialized_size = end;
  	a->data.non_resident.initialized_size = cpu_to_sle64(end);
  	if (end > i_size_read(vi)) {
  		i_size_write(vi, end);
  		a->data.non_resident.data_size =
  				a->data.non_resident.initialized_size;
  	}
  	write_unlock_irqrestore(&ni->size_lock, flags);
  	/* Mark the mft record dirty, so it gets written back. */
  	flush_dcache_mft_record_page(ctx->ntfs_ino);
  	mark_mft_record_dirty(ctx->ntfs_ino);
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(base_ni);
  	ntfs_debug("Done.");
  	return 0;
  err_out:
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(base_ni);
  	ntfs_error(vi->i_sb, "Failed to update initialized_size/i_size (error "
  			"code %i).", err);

  	if (err != -ENOMEM)

  		NVolSetErrors(ni->vol);

  	return err;
  }
  
  /**
   * ntfs_commit_pages_after_write - commit the received data
   * @pages:	array of destination pages
   * @nr_pages:	number of pages in @pages
   * @pos:	byte position in file at which the write begins
   * @bytes:	number of bytes to be written
   *

   * This is called from ntfs_file_buffered_write() with i_mutex held on the inode

   * (@pages[0]->mapping->host).  There are @nr_pages pages in @pages which are
   * locked but not kmap()ped.  The source data has already been copied into the
   * @page.  ntfs_prepare_pages_for_non_resident_write() has been called before
   * the data was copied (for non-resident attributes only) and it returned
   * success.
   *
   * Need to set uptodate and mark dirty all buffers within the boundary of the
   * write.  If all buffers in a page are uptodate we set the page uptodate, too.
   *
   * Setting the buffers dirty ensures that they get written out later when
   * ntfs_writepage() is invoked by the VM.
   *
   * Finally, we need to update i_size and initialized_size as appropriate both
   * in the inode and the mft record.
   *
   * This is modelled after fs/buffer.c::generic_commit_write(), which marks
   * buffers uptodate and dirty, sets the page uptodate if all buffers in the
   * page are uptodate, and updates i_size if the end of io is beyond i_size.  In
   * that case, it also marks the inode dirty.
   *
   * If things have gone as outlined in
   * ntfs_prepare_pages_for_non_resident_write(), we do not need to do any page
   * content modifications here for non-resident attributes.  For resident
   * attributes we need to do the uptodate bringing here which we combine with
   * the copying into the mft record which means we save one atomic kmap.
   *
   * Return 0 on success or -errno on error.
   */
  static int ntfs_commit_pages_after_write(struct page **pages,
  		const unsigned nr_pages, s64 pos, size_t bytes)
  {
  	s64 end, initialized_size;
  	loff_t i_size;
  	struct inode *vi;
  	ntfs_inode *ni, *base_ni;
  	struct page *page;
  	ntfs_attr_search_ctx *ctx;
  	MFT_RECORD *m;
  	ATTR_RECORD *a;
  	char *kattr, *kaddr;
  	unsigned long flags;
  	u32 attr_len;
  	int err;
  
  	BUG_ON(!nr_pages);
  	BUG_ON(!pages);
  	page = pages[0];
  	BUG_ON(!page);
  	vi = page->mapping->host;
  	ni = NTFS_I(vi);
  	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "

  			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",

  			vi->i_ino, ni->type, page->index, nr_pages,
  			(long long)pos, bytes);
  	if (NInoNonResident(ni))
  		return ntfs_commit_pages_after_non_resident_write(pages,
  				nr_pages, pos, bytes);
  	BUG_ON(nr_pages > 1);
  	/*
  	 * Attribute is resident, implying it is not compressed, encrypted, or
  	 * sparse.
  	 */
  	if (!NInoAttr(ni))
  		base_ni = ni;
  	else
  		base_ni = ni->ext.base_ntfs_ino;
  	BUG_ON(NInoNonResident(ni));
  	/* Map, pin, and lock the mft record. */
  	m = map_mft_record(base_ni);
  	if (IS_ERR(m)) {
  		err = PTR_ERR(m);
  		m = NULL;
  		ctx = NULL;
  		goto err_out;
  	}
  	ctx = ntfs_attr_get_search_ctx(base_ni, m);
  	if (unlikely(!ctx)) {
  		err = -ENOMEM;
  		goto err_out;
  	}
  	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
  			CASE_SENSITIVE, 0, NULL, 0, ctx);
  	if (unlikely(err)) {
  		if (err == -ENOENT)
  			err = -EIO;
  		goto err_out;
  	}
  	a = ctx->attr;
  	BUG_ON(a->non_resident);
  	/* The total length of the attribute value. */
  	attr_len = le32_to_cpu(a->data.resident.value_length);
  	i_size = i_size_read(vi);
  	BUG_ON(attr_len != i_size);
  	BUG_ON(pos > attr_len);
  	end = pos + bytes;
  	BUG_ON(end > le32_to_cpu(a->length) -
  			le16_to_cpu(a->data.resident.value_offset));
  	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
  	kaddr = kmap_atomic(page, KM_USER0);
  	/* Copy the received data from the page to the mft record. */
  	memcpy(kattr + pos, kaddr + pos, bytes);
  	/* Update the attribute length if necessary. */
  	if (end > attr_len) {
  		attr_len = end;
  		a->data.resident.value_length = cpu_to_le32(attr_len);
  	}
  	/*
  	 * If the page is not uptodate, bring the out of bounds area(s)
  	 * uptodate by copying data from the mft record to the page.
  	 */
  	if (!PageUptodate(page)) {
  		if (pos > 0)
  			memcpy(kaddr, kattr, pos);
  		if (end < attr_len)
  			memcpy(kaddr + end, kattr + end, attr_len - end);
  		/* Zero the region outside the end of the attribute value. */
  		memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
  		flush_dcache_page(page);
  		SetPageUptodate(page);
  	}
  	kunmap_atomic(kaddr, KM_USER0);
  	/* Update initialized_size/i_size if necessary. */
  	read_lock_irqsave(&ni->size_lock, flags);
  	initialized_size = ni->initialized_size;
  	BUG_ON(end > ni->allocated_size);
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	BUG_ON(initialized_size != i_size);
  	if (end > initialized_size) {

  		write_lock_irqsave(&ni->size_lock, flags);
  		ni->initialized_size = end;
  		i_size_write(vi, end);
  		write_unlock_irqrestore(&ni->size_lock, flags);
  	}
  	/* Mark the mft record dirty, so it gets written back. */
  	flush_dcache_mft_record_page(ctx->ntfs_ino);
  	mark_mft_record_dirty(ctx->ntfs_ino);
  	ntfs_attr_put_search_ctx(ctx);
  	unmap_mft_record(base_ni);
  	ntfs_debug("Done.");
  	return 0;
  err_out:
  	if (err == -ENOMEM) {
  		ntfs_warning(vi->i_sb, "Error allocating memory required to "
  				"commit the write.");
  		if (PageUptodate(page)) {
  			ntfs_warning(vi->i_sb, "Page is uptodate, setting "
  					"dirty so the write will be retried "
  					"later on by the VM.");
  			/*
  			 * Put the page on mapping->dirty_pages, but leave its
  			 * buffers' dirty state as-is.
  			 */
  			__set_page_dirty_nobuffers(page);
  			err = 0;
  		} else
  			ntfs_error(vi->i_sb, "Page is not uptodate.  Written "
  					"data has been lost.");
  	} else {
  		ntfs_error(vi->i_sb, "Resident attribute commit write failed "
  				"with error %i.", err);
  		NVolSetErrors(ni->vol);

  	}
  	if (ctx)
  		ntfs_attr_put_search_ctx(ctx);
  	if (m)
  		unmap_mft_record(base_ni);
  	return err;
  }
  
  /**
   * ntfs_file_buffered_write -
   *

   * Locking: The vfs is holding ->i_mutex on the inode.

   */
  static ssize_t ntfs_file_buffered_write(struct kiocb *iocb,
  		const struct iovec *iov, unsigned long nr_segs,
  		loff_t pos, loff_t *ppos, size_t count)
  {
  	struct file *file = iocb->ki_filp;
  	struct address_space *mapping = file->f_mapping;
  	struct inode *vi = mapping->host;
  	ntfs_inode *ni = NTFS_I(vi);
  	ntfs_volume *vol = ni->vol;
  	struct page *pages[NTFS_MAX_PAGES_PER_CLUSTER];
  	struct page *cached_page = NULL;
  	char __user *buf = NULL;
  	s64 end, ll;
  	VCN last_vcn;
  	LCN lcn;
  	unsigned long flags;

  	size_t bytes, iov_ofs = 0;	/* Offset in the current iovec. */

  	ssize_t status, written;
  	unsigned nr_pages;
  	int err;

  
  	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
  			"pos 0x%llx, count 0x%lx.",
  			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
  			(unsigned long long)pos, (unsigned long)count);
  	if (unlikely(!count))
  		return 0;
  	BUG_ON(NInoMstProtected(ni));
  	/*
  	 * If the attribute is not an index root and it is encrypted or
  	 * compressed, we cannot write to it yet.  Note we need to check for
  	 * AT_INDEX_ALLOCATION since this is the type of both directory and
  	 * index inodes.
  	 */
  	if (ni->type != AT_INDEX_ALLOCATION) {
  		/* If file is encrypted, deny access, just like NT4. */
  		if (NInoEncrypted(ni)) {

  			/*
  			 * Reminder for later: Encrypted files are _always_
  			 * non-resident so that the content can always be
  			 * encrypted.
  			 */

  			ntfs_debug("Denying write access to encrypted file.");
  			return -EACCES;
  		}
  		if (NInoCompressed(ni)) {

  			/* Only unnamed $DATA attribute can be compressed. */
  			BUG_ON(ni->type != AT_DATA);
  			BUG_ON(ni->name_len);
  			/*
  			 * Reminder for later: If resident, the data is not
  			 * actually compressed.  Only on the switch to non-
  			 * resident does compression kick in.  This is in
  			 * contrast to encrypted files (see above).
  			 */

  			ntfs_error(vi->i_sb, "Writing to compressed files is "
  					"not implemented yet.  Sorry.");
  			return -EOPNOTSUPP;
  		}
  	}
  	/*
  	 * If a previous ntfs_truncate() failed, repeat it and abort if it
  	 * fails again.
  	 */
  	if (unlikely(NInoTruncateFailed(ni))) {

  		inode_dio_wait(vi);

  		err = ntfs_truncate(vi);

  		if (err || NInoTruncateFailed(ni)) {
  			if (!err)
  				err = -EIO;
  			ntfs_error(vol->sb, "Cannot perform write to inode "
  					"0x%lx, attribute type 0x%x, because "
  					"ntfs_truncate() failed (error code "
  					"%i).", vi->i_ino,
  					(unsigned)le32_to_cpu(ni->type), err);
  			return err;
  		}
  	}
  	/* The first byte after the write. */
  	end = pos + count;
  	/*
  	 * If the write goes beyond the allocated size, extend the allocation
  	 * to cover the whole of the write, rounded up to the nearest cluster.
  	 */
  	read_lock_irqsave(&ni->size_lock, flags);
  	ll = ni->allocated_size;
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	if (end > ll) {
  		/* Extend the allocation without changing the data size. */
  		ll = ntfs_attr_extend_allocation(ni, end, -1, pos);
  		if (likely(ll >= 0)) {
  			BUG_ON(pos >= ll);
  			/* If the extension was partial truncate the write. */
  			if (end > ll) {
  				ntfs_debug("Truncating write to inode 0x%lx, "
  						"attribute type 0x%x, because "
  						"the allocation was only "
  						"partially extended.",
  						vi->i_ino, (unsigned)
  						le32_to_cpu(ni->type));
  				end = ll;
  				count = ll - pos;
  			}
  		} else {
  			err = ll;
  			read_lock_irqsave(&ni->size_lock, flags);
  			ll = ni->allocated_size;
  			read_unlock_irqrestore(&ni->size_lock, flags);
  			/* Perform a partial write if possible or fail. */
  			if (pos < ll) {
  				ntfs_debug("Truncating write to inode 0x%lx, "
  						"attribute type 0x%x, because "
  						"extending the allocation "
  						"failed (error code %i).",
  						vi->i_ino, (unsigned)
  						le32_to_cpu(ni->type), err);
  				end = ll;
  				count = ll - pos;
  			} else {
  				ntfs_error(vol->sb, "Cannot perform write to "
  						"inode 0x%lx, attribute type "
  						"0x%x, because extending the "
  						"allocation failed (error "
  						"code %i).", vi->i_ino,
  						(unsigned)
  						le32_to_cpu(ni->type), err);
  				return err;
  			}
  		}
  	}

  	written = 0;
  	/*
  	 * If the write starts beyond the initialized size, extend it up to the
  	 * beginning of the write and initialize all non-sparse space between
  	 * the old initialized size and the new one.  This automatically also
  	 * increments the vfs inode->i_size to keep it above or equal to the
  	 * initialized_size.
  	 */
  	read_lock_irqsave(&ni->size_lock, flags);
  	ll = ni->initialized_size;
  	read_unlock_irqrestore(&ni->size_lock, flags);
  	if (pos > ll) {

  		err = ntfs_attr_extend_initialized(ni, pos);

  		if (err < 0) {
  			ntfs_error(vol->sb, "Cannot perform write to inode "
  					"0x%lx, attribute type 0x%x, because "
  					"extending the initialized size "
  					"failed (error code %i).", vi->i_ino,
  					(unsigned)le32_to_cpu(ni->type), err);
  			status = err;
  			goto err_out;
  		}
  	}
  	/*
  	 * Determine the number of pages per cluster for non-resident
  	 * attributes.
  	 */
  	nr_pages = 1;
  	if (vol->cluster_size > PAGE_CACHE_SIZE && NInoNonResident(ni))
  		nr_pages = vol->cluster_size >> PAGE_CACHE_SHIFT;
  	/* Finally, perform the actual write. */
  	last_vcn = -1;
  	if (likely(nr_segs == 1))
  		buf = iov->iov_base;

  	do {
  		VCN vcn;
  		pgoff_t idx, start_idx;
  		unsigned ofs, do_pages, u;
  		size_t copied;
  
  		start_idx = idx = pos >> PAGE_CACHE_SHIFT;
  		ofs = pos & ~PAGE_CACHE_MASK;
  		bytes = PAGE_CACHE_SIZE - ofs;
  		do_pages = 1;
  		if (nr_pages > 1) {
  			vcn = pos >> vol->cluster_size_bits;
  			if (vcn != last_vcn) {
  				last_vcn = vcn;
  				/*
  				 * Get the lcn of the vcn the write is in.  If
  				 * it is a hole, need to lock down all pages in
  				 * the cluster.
  				 */
  				down_read(&ni->runlist.lock);
  				lcn = ntfs_attr_vcn_to_lcn_nolock(ni, pos >>

  						vol->cluster_size_bits, false);

  				up_read(&ni->runlist.lock);
  				if (unlikely(lcn < LCN_HOLE)) {
  					status = -EIO;
  					if (lcn == LCN_ENOMEM)
  						status = -ENOMEM;
  					else
  						ntfs_error(vol->sb, "Cannot "
  							"perform write to "
  							"inode 0x%lx, "
  							"attribute type 0x%x, "
  							"because the attribute "
  							"is corrupt.",
  							vi->i_ino, (unsigned)
  							le32_to_cpu(ni->type));
  					break;
  				}
  				if (lcn == LCN_HOLE) {
  					start_idx = (pos & ~(s64)
  							vol->cluster_size_mask)
  							>> PAGE_CACHE_SHIFT;
  					bytes = vol->cluster_size - (pos &
  							vol->cluster_size_mask);
  					do_pages = nr_pages;
  				}
  			}
  		}
  		if (bytes > count)
  			bytes = count;
  		/*
  		 * Bring in the user page(s) that we will copy from _first_.
  		 * Otherwise there is a nasty deadlock on copying from the same
  		 * page(s) as we are writing to, without it/them being marked
  		 * up-to-date.  Note, at present there is nothing to stop the
  		 * pages being swapped out between us bringing them into memory
  		 * and doing the actual copying.
  		 */
  		if (likely(nr_segs == 1))
  			ntfs_fault_in_pages_readable(buf, bytes);
  		else
  			ntfs_fault_in_pages_readable_iovec(iov, iov_ofs, bytes);
  		/* Get and lock @do_pages starting at index @start_idx. */
  		status = __ntfs_grab_cache_pages(mapping, start_idx, do_pages,

  				pages, &cached_page);

  		if (unlikely(status))
  			break;
  		/*
  		 * For non-resident attributes, we need to fill any holes with
  		 * actual clusters and ensure all bufferes are mapped.  We also
  		 * need to bring uptodate any buffers that are only partially
  		 * being written to.
  		 */
  		if (NInoNonResident(ni)) {
  			status = ntfs_prepare_pages_for_non_resident_write(
  					pages, do_pages, pos, bytes);
  			if (unlikely(status)) {
  				loff_t i_size;
  
  				do {
  					unlock_page(pages[--do_pages]);
  					page_cache_release(pages[do_pages]);
  				} while (do_pages);
  				/*
  				 * The write preparation may have instantiated
  				 * allocated space outside i_size.  Trim this
  				 * off again.  We can ignore any errors in this
  				 * case as we will just be waisting a bit of
  				 * allocated space, which is not a disaster.
  				 */
  				i_size = i_size_read(vi);
  				if (pos + bytes > i_size)
  					vmtruncate(vi, i_size);
  				break;
  			}
  		}
  		u = (pos >> PAGE_CACHE_SHIFT) - pages[0]->index;
  		if (likely(nr_segs == 1)) {
  			copied = ntfs_copy_from_user(pages + u, do_pages - u,
  					ofs, buf, bytes);
  			buf += copied;
  		} else
  			copied = ntfs_copy_from_user_iovec(pages + u,
  					do_pages - u, ofs, &iov, &iov_ofs,
  					bytes);
  		ntfs_flush_dcache_pages(pages + u, do_pages - u);
  		status = ntfs_commit_pages_after_write(pages, do_pages, pos,
  				bytes);
  		if (likely(!status)) {
  			written += copied;
  			count -= copied;
  			pos += copied;
  			if (unlikely(copied != bytes))
  				status = -EFAULT;
  		}
  		do {
  			unlock_page(pages[--do_pages]);
  			mark_page_accessed(pages[do_pages]);
  			page_cache_release(pages[do_pages]);
  		} while (do_pages);
  		if (unlikely(status))
  			break;
  		balance_dirty_pages_ratelimited(mapping);
  		cond_resched();
  	} while (count);
  err_out:
  	*ppos = pos;
  	if (cached_page)
  		page_cache_release(cached_page);

  	ntfs_debug("Done.  Returning %s (written 0x%lx, status %li).",
  			written ? "written" : "status", (unsigned long)written,
  			(long)status);
  	return written ? written : status;
  }
  
  /**
   * ntfs_file_aio_write_nolock -
   */
  static ssize_t ntfs_file_aio_write_nolock(struct kiocb *iocb,
  		const struct iovec *iov, unsigned long nr_segs, loff_t *ppos)
  {
  	struct file *file = iocb->ki_filp;
  	struct address_space *mapping = file->f_mapping;
  	struct inode *inode = mapping->host;
  	loff_t pos;

  	size_t count;		/* after file limit checks */
  	ssize_t written, err;
  
  	count = 0;

  	err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
  	if (err)
  		return err;

  	pos = *ppos;
  	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
  	/* We can write back this queue in page reclaim. */
  	current->backing_dev_info = mapping->backing_dev_info;
  	written = 0;
  	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
  	if (err)
  		goto out;
  	if (!count)
  		goto out;

  	err = file_remove_suid(file);

  	if (err)
  		goto out;

  	file_update_time(file);

  	written = ntfs_file_buffered_write(iocb, iov, nr_segs, pos, ppos,
  			count);
  out:
  	current->backing_dev_info = NULL;
  	return written ? written : err;
  }
  
  /**
   * ntfs_file_aio_write -
   */

  static ssize_t ntfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
  		unsigned long nr_segs, loff_t pos)

  {
  	struct file *file = iocb->ki_filp;
  	struct address_space *mapping = file->f_mapping;
  	struct inode *inode = mapping->host;
  	ssize_t ret;

  
  	BUG_ON(iocb->ki_pos != pos);

  	mutex_lock(&inode->i_mutex);

  	ret = ntfs_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos);

  	mutex_unlock(&inode->i_mutex);

  	if (ret > 0) {
  		int err = generic_write_sync(file, pos, ret);

  		if (err < 0)
  			ret = err;
  	}
  	return ret;
  }
  
  /**

   * ntfs_file_fsync - sync a file to disk
   * @filp:	file to be synced

   * @datasync:	if non-zero only flush user data and not metadata
   *
   * Data integrity sync of a file to disk.  Used for fsync, fdatasync, and msync
   * system calls.  This function is inspired by fs/buffer.c::file_fsync().
   *
   * If @datasync is false, write the mft record and all associated extent mft
   * records as well as the $DATA attribute and then sync the block device.
   *
   * If @datasync is true and the attribute is non-resident, we skip the writing
   * of the mft record and all associated extent mft records (this might still
   * happen due to the write_inode_now() call).
   *
   * Also, if @datasync is true, we do not wait on the inode to be written out
   * but we always wait on the page cache pages to be written out.
   *

   * Locking: Caller must hold i_mutex on the inode.

   *
   * TODO: We should probably also write all attribute/index inodes associated
   * with this inode but since we have no simple way of getting to them we ignore
   * this problem for now.
   */

  static int ntfs_file_fsync(struct file *filp, loff_t start, loff_t end,
  			   int datasync)

  {

  	struct inode *vi = filp->f_mapping->host;

  	int err, ret = 0;
  
  	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);

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

  	BUG_ON(S_ISDIR(vi->i_mode));
  	if (!datasync || !NInoNonResident(NTFS_I(vi)))

  		ret = __ntfs_write_inode(vi, 1);

  	write_inode_now(vi, !datasync);

  	/*
  	 * NOTE: If we were to use mapping->private_list (see ext2 and
  	 * fs/buffer.c) for dirty blocks then we could optimize the below to be
  	 * sync_mapping_buffers(vi->i_mapping).
  	 */

  	err = sync_blockdev(vi->i_sb->s_bdev);
  	if (unlikely(err && !ret))
  		ret = err;
  	if (likely(!ret))
  		ntfs_debug("Done.");
  	else
  		ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
  				"%u.", datasync ? "data" : "", vi->i_ino, -ret);

  	mutex_unlock(&vi->i_mutex);

  	return ret;
  }
  
  #endif /* NTFS_RW */

  const struct file_operations ntfs_file_ops = {

  	.llseek		= generic_file_llseek,	 /* Seek inside file. */

  	.read		= do_sync_read,		 /* Read from file. */

  	.aio_read	= generic_file_aio_read, /* Async read from file. */

  #ifdef NTFS_RW

  	.write		= do_sync_write,	 /* Write to file. */

  	.aio_write	= ntfs_file_aio_write,	 /* Async write to file. */

  	/*.release	= ,*/			 /* Last file is closed.  See
  						    fs/ext2/file.c::
  						    ext2_release_file() for
  						    how to use this to discard
  						    preallocated space for
  						    write opened files. */
  	.fsync		= ntfs_file_fsync,	 /* Sync a file to disk. */
  	/*.aio_fsync	= ,*/			 /* Sync all outstanding async
  						    i/o operations on a
  						    kiocb. */

  #endif /* NTFS_RW */

  	/*.ioctl	= ,*/			 /* Perform function on the
  						    mounted filesystem. */
  	.mmap		= generic_file_mmap,	 /* Mmap file. */
  	.open		= ntfs_file_open,	 /* Open file. */

  	.splice_read	= generic_file_splice_read /* Zero-copy data send with

  						    the data source being on
  						    the ntfs partition.  We do
  						    not need to care about the
  						    data destination. */
  	/*.sendpage	= ,*/			 /* Zero-copy data send with
  						    the data destination being
  						    on the ntfs partition.  We
  						    do not need to care about
  						    the data source. */

  };

  const struct inode_operations ntfs_file_inode_ops = {

  #ifdef NTFS_RW
  	.truncate	= ntfs_truncate_vfs,
  	.setattr	= ntfs_setattr,
  #endif /* NTFS_RW */
  };

  const struct file_operations ntfs_empty_file_ops = {};

  const struct inode_operations ntfs_empty_inode_ops = {};