file.c 69.9 KB
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/*
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 * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
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 *
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 * Copyright (c) 2001-2006 Anton Altaparmakov
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 *
 * 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>
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#include <linux/pagemap.h>
#include <linux/pagevec.h>
#include <linux/sched.h>
#include <linux/swap.h>
#include <linux/uio.h>
#include <linux/writeback.h>
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#include <asm/page.h>
#include <asm/uaccess.h>

#include "attrib.h"
#include "bitmap.h"
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#include "inode.h"
#include "debug.h"
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#include "lcnalloc.h"
#include "malloc.h"
#include "mft.h"
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#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) {
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		if (i_size_read(vi) > MAX_LFS_FILESIZE)
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			return -EFBIG;
	}
	return generic_file_open(vi, filp);
}

#ifdef NTFS_RW

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/**
 * 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
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 * disk (if relevant complete pages are already uptodate in the page cache then
 * these are simply marked dirty).
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 *
 * 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
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 * the page at all.  For a more detailed explanation see ntfs_truncate() in
 * fs/ntfs/inode.c.
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 *
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 * @cached_page and @lru_pvec are just optimizations for dealing with multiple
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 * pages.
 *
 * 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.
 *
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 * Locking: i_mutex on the vfs inode corrseponsind to the ntfs inode @ni must be
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 *	    held by the caller.
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 */
static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size,
		struct page **cached_page, struct pagevec *lru_pvec)
{
	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_cache_page(mapping, index,
				(filler_t*)mapping->a_ops->readpage, NULL);
		if (IS_ERR(page)) {
			err = PTR_ERR(page);
			goto init_err_out;
		}
		wait_on_page_locked(page);
		if (unlikely(!PageUptodate(page) || 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);
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		ni->initialized_size = (s64)(index + 1) << PAGE_CACHE_SHIFT;
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		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((ptrdiff_t __user)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 @maping and
 * starting at index @index.
 *
 * If a page is newly created, increment its refcount and add it to the
 * caller's lru-buffering pagevec @lru_pvec.
 *
 * This is the same as mm/filemap.c::__grab_cache_page(), except that @nr_pages
 * are obtained at once instead of just one page and that 0 is returned on
 * success and -errno on error.
 *
 * 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, struct pagevec *lru_pvec)
{
	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(*cached_page, mapping, index,
					GFP_KERNEL);
			if (unlikely(err)) {
				if (err == -EEXIST)
					continue;
				goto err_out;
			}
			pages[nr] = *cached_page;
			page_cache_get(*cached_page);
			if (unlikely(!pagevec_add(lru_pvec, *cached_page)))
				__pagevec_lru_add(lru_pvec);
			*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()
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 * with i_mutex held on the inode (@pages[0]->mapping->host).  There are
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 * @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 "
529
			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
530
531
			vi->i_ino, ni->type, pages[0]->index, nr_pages,
			(long long)pos, bytes);
532
533
	blocksize = vol->sb->s_blocksize;
	blocksize_bits = vol->sb->s_blocksize_bits;
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
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661
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664
665
666
667
668
669
670
	u = 0;
	do {
		struct page *page = pages[u];
		/*
		 * 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 {
					u8 *kaddr = kmap_atomic(page, KM_USER0);
					memset(kaddr + bh_offset(bh), 0,
							blocksize);
					kunmap_atomic(kaddr, KM_USER0);
					flush_dcache_page(page);
					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.
				 */
671
672
673
674
				if (!buffer_uptodate(bh) && bh_pos < end &&
						bh_end > pos &&
						(bh_pos < pos ||
						bh_end > end)) {
675
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681
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684
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687
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689
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728
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731
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741
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766
767
768
769
770
771
772
773
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775
776
777
778
779
780
781
782
783
784
					/*
					 * 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 {
						u8 *kaddr = kmap_atomic(page,
								KM_USER0);
						memset(kaddr + bh_offset(bh),
								0, blocksize);
						kunmap_atomic(kaddr, KM_USER0);
						flush_dcache_page(page);
						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)) {
					u8 *kaddr = kmap_atomic(page, KM_USER0);
					memset(kaddr + bh_offset(bh), 0,
							blocksize);
					kunmap_atomic(kaddr, KM_USER0);
					flush_dcache_page(page);
					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)) {
				u8 *kaddr = kmap_atomic(page, KM_USER0);
				memset(kaddr + bh_offset(bh), 0, blocksize);
				kunmap_atomic(kaddr, KM_USER0);
				flush_dcache_page(page);
				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);
785
				cdelta = 0;
786
				/*
787
788
789
790
791
				 * 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.
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
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885
886
887
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889
890
891
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893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
				 */
				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)) {
					u8 *kaddr = kmap_atomic(page, KM_USER0);
					memset(kaddr + bh_offset(bh), 0,
							blocksize);
					kunmap_atomic(kaddr, KM_USER0);
					flush_dcache_page(page);
					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;
946
947
		ntfs_debug("Allocated cluster, lcn 0x%llx.",
				(unsigned long long)lcn);
948
949
950
951
952
953
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955
956
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985
986
987
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989
990
991
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993
994
995
996
997
998
999
1000
		/* 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);
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