X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;ds=sidebyside;f=kernel%2Ffs%2Fntfs%2Ffile.c;fp=kernel%2Ffs%2Fntfs%2Ffile.c;h=7bb487e663b478ed52633e43ecc94feb2a636a7f;hb=9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00;hp=0000000000000000000000000000000000000000;hpb=98260f3884f4a202f9ca5eabed40b1354c489b29;p=kvmfornfv.git

diff --git a/kernel/fs/ntfs/file.c b/kernel/fs/ntfs/file.c
new file mode 100644
index 000000000..7bb487e66
--- /dev/null
+++ b/kernel/fs/ntfs/file.c
@@ -0,0 +1,2043 @@
+/*
+ * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
+ *
+ * Copyright (c) 2001-2015 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/backing-dev.h>
+#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
+ *
+ * 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;
+}
+
+static ssize_t ntfs_prepare_file_for_write(struct kiocb *iocb,
+		struct iov_iter *from)
+{
+	loff_t pos;
+	s64 end, ll;
+	ssize_t err;
+	unsigned long flags;
+	struct file *file = iocb->ki_filp;
+	struct inode *vi = file_inode(file);
+	ntfs_inode *base_ni, *ni = NTFS_I(vi);
+	ntfs_volume *vol = ni->vol;
+
+	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, pos "
+			"0x%llx, count 0x%zx.", vi->i_ino,
+			(unsigned)le32_to_cpu(ni->type),
+			(unsigned long long)iocb->ki_pos,
+			iov_iter_count(from));
+	err = generic_write_checks(iocb, from);
+	if (unlikely(err <= 0))
+		goto out;
+	/*
+	 * All checks have passed.  Before we start doing any writing we want
+	 * to abort any totally illegal writes.
+	 */
+	BUG_ON(NInoMstProtected(ni));
+	BUG_ON(ni->type != AT_DATA);
+	/* If file is encrypted, deny access, just like NT4. */
+	if (NInoEncrypted(ni)) {
+		/* Only $DATA attributes can be encrypted. */
+		/*
+		 * 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.");
+		err = -EACCES;
+		goto out;
+	}
+	if (NInoCompressed(ni)) {
+		/* Only unnamed $DATA attribute can be compressed. */
+		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.");
+		err = -EOPNOTSUPP;
+		goto out;
+	}
+	base_ni = ni;
+	if (NInoAttr(ni))
+		base_ni = ni->ext.base_ntfs_ino;
+	err = file_remove_suid(file);
+	if (unlikely(err))
+		goto out;
+	/*
+	 * Our ->update_time method always succeeds thus file_update_time()
+	 * cannot fail either so there is no need to check the return code.
+	 */
+	file_update_time(file);
+	pos = iocb->ki_pos;
+	/* The first byte after the last cluster being written to. */
+	end = (pos + iov_iter_count(from) + vol->cluster_size_mask) &
+			~(u64)vol->cluster_size_mask;
+	/*
+	 * 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.
+		 *
+		 * Note we ensure the allocation is big enough to at least
+		 * write some data but we do not require the allocation to be
+		 * complete, i.e. it may be partial.
+		 */
+		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));
+				iov_iter_truncate(from, 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 %d).",
+						vi->i_ino, (unsigned)
+						le32_to_cpu(ni->type),
+						(int)-err);
+				iov_iter_truncate(from, ll - pos);
+			} else {
+				if (err != -ENOSPC)
+					ntfs_error(vi->i_sb, "Cannot perform "
+							"write to inode "
+							"0x%lx, attribute "
+							"type 0x%x, because "
+							"extending the "
+							"allocation failed "
+							"(error %ld).",
+							vi->i_ino, (unsigned)
+							le32_to_cpu(ni->type),
+							(long)-err);
+				else
+					ntfs_debug("Cannot perform write to "
+							"inode 0x%lx, "
+							"attribute type 0x%x, "
+							"because there is not "
+							"space left.",
+							vi->i_ino, (unsigned)
+							le32_to_cpu(ni->type));
+				goto out;
+			}
+		}
+	}
+	/*
+	 * 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) {
+		/*
+		 * Wait for ongoing direct i/o to complete before proceeding.
+		 * New direct i/o cannot start as we hold i_mutex.
+		 */
+		inode_dio_wait(vi);
+		err = ntfs_attr_extend_initialized(ni, pos);
+		if (unlikely(err < 0))
+			ntfs_error(vi->i_sb, "Cannot perform write to inode "
+					"0x%lx, attribute type 0x%x, because "
+					"extending the initialized size "
+					"failed (error %d).", vi->i_ino,
+					(unsigned)le32_to_cpu(ni->type),
+					(int)-err);
+	}
+out:
+	return err;
+}
+
+/**
+ * __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
+ *
+ * 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_get_page_flags(mapping, index, FGP_LOCK |
+				FGP_ACCESSED);
+		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);
+				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);
+				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;
+}
+
+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);
+	/* 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);
+	/* 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;
+}
+
+/*
+ * 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 size_t ntfs_copy_from_user_iter(struct page **pages, unsigned nr_pages,
+		unsigned ofs, struct iov_iter *i, size_t bytes)
+{
+	struct page **last_page = pages + nr_pages;
+	size_t total = 0;
+	struct iov_iter data = *i;
+	unsigned len, copied;
+
+	do {
+		len = PAGE_CACHE_SIZE - ofs;
+		if (len > bytes)
+			len = bytes;
+		copied = iov_iter_copy_from_user_atomic(*pages, &data, ofs,
+				len);
+		total += copied;
+		bytes -= copied;
+		if (!bytes)
+			break;
+		iov_iter_advance(&data, copied);
+		if (copied < len)
+			goto err;
+		ofs = 0;
+	} while (++pages < last_page);
+out:
+	return total;
+err:
+	/* Zero the rest of the target like __copy_from_user(). */
+	len = PAGE_CACHE_SIZE - copied;
+	do {
+		if (len > bytes)
+			len = bytes;
+		zero_user(*pages, copied, len);
+		bytes -= len;
+		copied = 0;
+		len = PAGE_CACHE_SIZE;
+	} while (++pages < last_page);
+	goto out;
+}
+
+/**
+ * ntfs_perform_write - perform buffered write to a file
+ * @file:	file to write to
+ * @i:		iov_iter with data to write
+ * @pos:	byte offset in file at which to begin writing to
+ */
+static ssize_t ntfs_perform_write(struct file *file, struct iov_iter *i,
+		loff_t pos)
+{
+	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;
+	VCN last_vcn;
+	LCN lcn;
+	size_t bytes;
+	ssize_t status, written = 0;
+	unsigned nr_pages;
+
+	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)iov_iter_count(i));
+	/*
+	 * If a previous ntfs_truncate() failed, repeat it and abort if it
+	 * fails again.
+	 */
+	if (unlikely(NInoTruncateFailed(ni))) {
+		int err;
+
+		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;
+		}
+	}
+	/*
+	 * 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;
+	last_vcn = -1;
+	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)) {
+					if (lcn == LCN_ENOMEM)
+						status = -ENOMEM;
+					else {
+						status = -EIO;
+						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 > iov_iter_count(i))
+			bytes = iov_iter_count(i);
+again:
+		/*
+		 * 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 (unlikely(iov_iter_fault_in_multipages_readable(i, bytes))) {
+			status = -EFAULT;
+			break;
+		}
+		/* 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)) {
+				do {
+					unlock_page(pages[--do_pages]);
+					page_cache_release(pages[do_pages]);
+				} while (do_pages);
+				break;
+			}
+		}
+		u = (pos >> PAGE_CACHE_SHIFT) - pages[0]->index;
+		copied = ntfs_copy_from_user_iter(pages + u, do_pages - u, ofs,
+					i, bytes);
+		ntfs_flush_dcache_pages(pages + u, do_pages - u);
+		status = 0;
+		if (likely(copied == bytes)) {
+			status = ntfs_commit_pages_after_write(pages, do_pages,
+					pos, bytes);
+			if (!status)
+				status = bytes;
+		}
+		do {
+			unlock_page(pages[--do_pages]);
+			page_cache_release(pages[do_pages]);
+		} while (do_pages);
+		if (unlikely(status < 0))
+			break;
+		copied = status;
+		cond_resched();
+		if (unlikely(!copied)) {
+			size_t sc;
+
+			/*
+			 * We failed to copy anything.  Fall back to single
+			 * segment length write.
+			 *
+			 * This is needed to avoid possible livelock in the
+			 * case that all segments in the iov cannot be copied
+			 * at once without a pagefault.
+			 */
+			sc = iov_iter_single_seg_count(i);
+			if (bytes > sc)
+				bytes = sc;
+			goto again;
+		}
+		iov_iter_advance(i, copied);
+		pos += copied;
+		written += copied;
+		balance_dirty_pages_ratelimited(mapping);
+		if (fatal_signal_pending(current)) {
+			status = -EINTR;
+			break;
+		}
+	} while (iov_iter_count(i));
+	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_write_iter - simple wrapper for ntfs_file_write_iter_nolock()
+ * @iocb:	IO state structure
+ * @from:	iov_iter with data to write
+ *
+ * Basically the same as generic_file_write_iter() except that it ends up
+ * up calling ntfs_perform_write() instead of generic_perform_write() and that
+ * O_DIRECT is not implemented.
+ */
+static ssize_t ntfs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *vi = file_inode(file);
+	ssize_t written = 0;
+	ssize_t err;
+
+	mutex_lock(&vi->i_mutex);
+	/* We can write back this queue in page reclaim. */
+	current->backing_dev_info = inode_to_bdi(vi);
+	err = ntfs_prepare_file_for_write(iocb, from);
+	if (iov_iter_count(from) && !err)
+		written = ntfs_perform_write(file, from, iocb->ki_pos);
+	current->backing_dev_info = NULL;
+	mutex_unlock(&vi->i_mutex);
+	if (likely(written > 0)) {
+		err = generic_write_sync(file, iocb->ki_pos, written);
+		if (err < 0)
+			written = 0;
+	}
+	iocb->ki_pos += written;
+	return written ? written : err;
+}
+
+/**
+ * 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,
+	.read_iter	= generic_file_read_iter,
+#ifdef NTFS_RW
+	.write_iter	= ntfs_file_write_iter,
+	.fsync		= ntfs_file_fsync,
+#endif /* NTFS_RW */
+	.mmap		= generic_file_mmap,
+	.open		= ntfs_file_open,
+	.splice_read	= generic_file_splice_read,
+};
+
+const struct inode_operations ntfs_file_inode_ops = {
+#ifdef NTFS_RW
+	.setattr	= ntfs_setattr,
+#endif /* NTFS_RW */
+};
+
+const struct file_operations ntfs_empty_file_ops = {};
+
+const struct inode_operations ntfs_empty_inode_ops = {};