xref: /openbmc/linux/fs/ntfs/file.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * file.c - NTFS kernel file operations.  Part of the Linux-NTFS project.
3  *
4  * Copyright (c) 2001-2006 Anton Altaparmakov
5  *
6  * This program/include file is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as published
8  * by the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program/include file is distributed in the hope that it will be
12  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
13  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program (in the main directory of the Linux-NTFS
18  * distribution in the file COPYING); if not, write to the Free Software
19  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20  */
21 
22 #include <linux/buffer_head.h>
23 #include <linux/pagemap.h>
24 #include <linux/pagevec.h>
25 #include <linux/sched.h>
26 #include <linux/swap.h>
27 #include <linux/uio.h>
28 #include <linux/writeback.h>
29 
30 #include <asm/page.h>
31 #include <asm/uaccess.h>
32 
33 #include "attrib.h"
34 #include "bitmap.h"
35 #include "inode.h"
36 #include "debug.h"
37 #include "lcnalloc.h"
38 #include "malloc.h"
39 #include "mft.h"
40 #include "ntfs.h"
41 
42 /**
43  * ntfs_file_open - called when an inode is about to be opened
44  * @vi:		inode to be opened
45  * @filp:	file structure describing the inode
46  *
47  * Limit file size to the page cache limit on architectures where unsigned long
48  * is 32-bits. This is the most we can do for now without overflowing the page
49  * cache page index. Doing it this way means we don't run into problems because
50  * of existing too large files. It would be better to allow the user to read
51  * the beginning of the file but I doubt very much anyone is going to hit this
52  * check on a 32-bit architecture, so there is no point in adding the extra
53  * complexity required to support this.
54  *
55  * On 64-bit architectures, the check is hopefully optimized away by the
56  * compiler.
57  *
58  * After the check passes, just call generic_file_open() to do its work.
59  */
60 static int ntfs_file_open(struct inode *vi, struct file *filp)
61 {
62 	if (sizeof(unsigned long) < 8) {
63 		if (i_size_read(vi) > MAX_LFS_FILESIZE)
64 			return -EFBIG;
65 	}
66 	return generic_file_open(vi, filp);
67 }
68 
69 #ifdef NTFS_RW
70 
71 /**
72  * ntfs_attr_extend_initialized - extend the initialized size of an attribute
73  * @ni:			ntfs inode of the attribute to extend
74  * @new_init_size:	requested new initialized size in bytes
75  * @cached_page:	store any allocated but unused page here
76  * @lru_pvec:		lru-buffering pagevec of the caller
77  *
78  * Extend the initialized size of an attribute described by the ntfs inode @ni
79  * to @new_init_size bytes.  This involves zeroing any non-sparse space between
80  * the old initialized size and @new_init_size both in the page cache and on
81  * disk (if relevant complete pages are already uptodate in the page cache then
82  * these are simply marked dirty).
83  *
84  * As a side-effect, the file size (vfs inode->i_size) may be incremented as,
85  * in the resident attribute case, it is tied to the initialized size and, in
86  * the non-resident attribute case, it may not fall below the initialized size.
87  *
88  * Note that if the attribute is resident, we do not need to touch the page
89  * cache at all.  This is because if the page cache page is not uptodate we
90  * bring it uptodate later, when doing the write to the mft record since we
91  * then already have the page mapped.  And if the page is uptodate, the
92  * non-initialized region will already have been zeroed when the page was
93  * brought uptodate and the region may in fact already have been overwritten
94  * with new data via mmap() based writes, so we cannot just zero it.  And since
95  * POSIX specifies that the behaviour of resizing a file whilst it is mmap()ped
96  * is unspecified, we choose not to do zeroing and thus we do not need to touch
97  * the page at all.  For a more detailed explanation see ntfs_truncate() in
98  * fs/ntfs/inode.c.
99  *
100  * @cached_page and @lru_pvec are just optimizations for dealing with multiple
101  * pages.
102  *
103  * Return 0 on success and -errno on error.  In the case that an error is
104  * encountered it is possible that the initialized size will already have been
105  * incremented some way towards @new_init_size but it is guaranteed that if
106  * this is the case, the necessary zeroing will also have happened and that all
107  * metadata is self-consistent.
108  *
109  * Locking: i_mutex on the vfs inode corrseponsind to the ntfs inode @ni must be
110  *	    held by the caller.
111  */
112 static int ntfs_attr_extend_initialized(ntfs_inode *ni, const s64 new_init_size,
113 		struct page **cached_page, struct pagevec *lru_pvec)
114 {
115 	s64 old_init_size;
116 	loff_t old_i_size;
117 	pgoff_t index, end_index;
118 	unsigned long flags;
119 	struct inode *vi = VFS_I(ni);
120 	ntfs_inode *base_ni;
121 	MFT_RECORD *m = NULL;
122 	ATTR_RECORD *a;
123 	ntfs_attr_search_ctx *ctx = NULL;
124 	struct address_space *mapping;
125 	struct page *page = NULL;
126 	u8 *kattr;
127 	int err;
128 	u32 attr_len;
129 
130 	read_lock_irqsave(&ni->size_lock, flags);
131 	old_init_size = ni->initialized_size;
132 	old_i_size = i_size_read(vi);
133 	BUG_ON(new_init_size > ni->allocated_size);
134 	read_unlock_irqrestore(&ni->size_lock, flags);
135 	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
136 			"old_initialized_size 0x%llx, "
137 			"new_initialized_size 0x%llx, i_size 0x%llx.",
138 			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
139 			(unsigned long long)old_init_size,
140 			(unsigned long long)new_init_size, old_i_size);
141 	if (!NInoAttr(ni))
142 		base_ni = ni;
143 	else
144 		base_ni = ni->ext.base_ntfs_ino;
145 	/* Use goto to reduce indentation and we need the label below anyway. */
146 	if (NInoNonResident(ni))
147 		goto do_non_resident_extend;
148 	BUG_ON(old_init_size != old_i_size);
149 	m = map_mft_record(base_ni);
150 	if (IS_ERR(m)) {
151 		err = PTR_ERR(m);
152 		m = NULL;
153 		goto err_out;
154 	}
155 	ctx = ntfs_attr_get_search_ctx(base_ni, m);
156 	if (unlikely(!ctx)) {
157 		err = -ENOMEM;
158 		goto err_out;
159 	}
160 	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
161 			CASE_SENSITIVE, 0, NULL, 0, ctx);
162 	if (unlikely(err)) {
163 		if (err == -ENOENT)
164 			err = -EIO;
165 		goto err_out;
166 	}
167 	m = ctx->mrec;
168 	a = ctx->attr;
169 	BUG_ON(a->non_resident);
170 	/* The total length of the attribute value. */
171 	attr_len = le32_to_cpu(a->data.resident.value_length);
172 	BUG_ON(old_i_size != (loff_t)attr_len);
173 	/*
174 	 * Do the zeroing in the mft record and update the attribute size in
175 	 * the mft record.
176 	 */
177 	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
178 	memset(kattr + attr_len, 0, new_init_size - attr_len);
179 	a->data.resident.value_length = cpu_to_le32((u32)new_init_size);
180 	/* Finally, update the sizes in the vfs and ntfs inodes. */
181 	write_lock_irqsave(&ni->size_lock, flags);
182 	i_size_write(vi, new_init_size);
183 	ni->initialized_size = new_init_size;
184 	write_unlock_irqrestore(&ni->size_lock, flags);
185 	goto done;
186 do_non_resident_extend:
187 	/*
188 	 * If the new initialized size @new_init_size exceeds the current file
189 	 * size (vfs inode->i_size), we need to extend the file size to the
190 	 * new initialized size.
191 	 */
192 	if (new_init_size > old_i_size) {
193 		m = map_mft_record(base_ni);
194 		if (IS_ERR(m)) {
195 			err = PTR_ERR(m);
196 			m = NULL;
197 			goto err_out;
198 		}
199 		ctx = ntfs_attr_get_search_ctx(base_ni, m);
200 		if (unlikely(!ctx)) {
201 			err = -ENOMEM;
202 			goto err_out;
203 		}
204 		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
205 				CASE_SENSITIVE, 0, NULL, 0, ctx);
206 		if (unlikely(err)) {
207 			if (err == -ENOENT)
208 				err = -EIO;
209 			goto err_out;
210 		}
211 		m = ctx->mrec;
212 		a = ctx->attr;
213 		BUG_ON(!a->non_resident);
214 		BUG_ON(old_i_size != (loff_t)
215 				sle64_to_cpu(a->data.non_resident.data_size));
216 		a->data.non_resident.data_size = cpu_to_sle64(new_init_size);
217 		flush_dcache_mft_record_page(ctx->ntfs_ino);
218 		mark_mft_record_dirty(ctx->ntfs_ino);
219 		/* Update the file size in the vfs inode. */
220 		i_size_write(vi, new_init_size);
221 		ntfs_attr_put_search_ctx(ctx);
222 		ctx = NULL;
223 		unmap_mft_record(base_ni);
224 		m = NULL;
225 	}
226 	mapping = vi->i_mapping;
227 	index = old_init_size >> PAGE_CACHE_SHIFT;
228 	end_index = (new_init_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
229 	do {
230 		/*
231 		 * Read the page.  If the page is not present, this will zero
232 		 * the uninitialized regions for us.
233 		 */
234 		page = read_mapping_page(mapping, index, NULL);
235 		if (IS_ERR(page)) {
236 			err = PTR_ERR(page);
237 			goto init_err_out;
238 		}
239 		if (unlikely(PageError(page))) {
240 			page_cache_release(page);
241 			err = -EIO;
242 			goto init_err_out;
243 		}
244 		/*
245 		 * Update the initialized size in the ntfs inode.  This is
246 		 * enough to make ntfs_writepage() work.
247 		 */
248 		write_lock_irqsave(&ni->size_lock, flags);
249 		ni->initialized_size = (s64)(index + 1) << PAGE_CACHE_SHIFT;
250 		if (ni->initialized_size > new_init_size)
251 			ni->initialized_size = new_init_size;
252 		write_unlock_irqrestore(&ni->size_lock, flags);
253 		/* Set the page dirty so it gets written out. */
254 		set_page_dirty(page);
255 		page_cache_release(page);
256 		/*
257 		 * Play nice with the vm and the rest of the system.  This is
258 		 * very much needed as we can potentially be modifying the
259 		 * initialised size from a very small value to a really huge
260 		 * value, e.g.
261 		 *	f = open(somefile, O_TRUNC);
262 		 *	truncate(f, 10GiB);
263 		 *	seek(f, 10GiB);
264 		 *	write(f, 1);
265 		 * And this would mean we would be marking dirty hundreds of
266 		 * thousands of pages or as in the above example more than
267 		 * two and a half million pages!
268 		 *
269 		 * TODO: For sparse pages could optimize this workload by using
270 		 * the FsMisc / MiscFs page bit as a "PageIsSparse" bit.  This
271 		 * would be set in readpage for sparse pages and here we would
272 		 * not need to mark dirty any pages which have this bit set.
273 		 * The only caveat is that we have to clear the bit everywhere
274 		 * where we allocate any clusters that lie in the page or that
275 		 * contain the page.
276 		 *
277 		 * TODO: An even greater optimization would be for us to only
278 		 * call readpage() on pages which are not in sparse regions as
279 		 * determined from the runlist.  This would greatly reduce the
280 		 * number of pages we read and make dirty in the case of sparse
281 		 * files.
282 		 */
283 		balance_dirty_pages_ratelimited(mapping);
284 		cond_resched();
285 	} while (++index < end_index);
286 	read_lock_irqsave(&ni->size_lock, flags);
287 	BUG_ON(ni->initialized_size != new_init_size);
288 	read_unlock_irqrestore(&ni->size_lock, flags);
289 	/* Now bring in sync the initialized_size in the mft record. */
290 	m = map_mft_record(base_ni);
291 	if (IS_ERR(m)) {
292 		err = PTR_ERR(m);
293 		m = NULL;
294 		goto init_err_out;
295 	}
296 	ctx = ntfs_attr_get_search_ctx(base_ni, m);
297 	if (unlikely(!ctx)) {
298 		err = -ENOMEM;
299 		goto init_err_out;
300 	}
301 	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
302 			CASE_SENSITIVE, 0, NULL, 0, ctx);
303 	if (unlikely(err)) {
304 		if (err == -ENOENT)
305 			err = -EIO;
306 		goto init_err_out;
307 	}
308 	m = ctx->mrec;
309 	a = ctx->attr;
310 	BUG_ON(!a->non_resident);
311 	a->data.non_resident.initialized_size = cpu_to_sle64(new_init_size);
312 done:
313 	flush_dcache_mft_record_page(ctx->ntfs_ino);
314 	mark_mft_record_dirty(ctx->ntfs_ino);
315 	if (ctx)
316 		ntfs_attr_put_search_ctx(ctx);
317 	if (m)
318 		unmap_mft_record(base_ni);
319 	ntfs_debug("Done, initialized_size 0x%llx, i_size 0x%llx.",
320 			(unsigned long long)new_init_size, i_size_read(vi));
321 	return 0;
322 init_err_out:
323 	write_lock_irqsave(&ni->size_lock, flags);
324 	ni->initialized_size = old_init_size;
325 	write_unlock_irqrestore(&ni->size_lock, flags);
326 err_out:
327 	if (ctx)
328 		ntfs_attr_put_search_ctx(ctx);
329 	if (m)
330 		unmap_mft_record(base_ni);
331 	ntfs_debug("Failed.  Returning error code %i.", err);
332 	return err;
333 }
334 
335 /**
336  * ntfs_fault_in_pages_readable -
337  *
338  * Fault a number of userspace pages into pagetables.
339  *
340  * Unlike include/linux/pagemap.h::fault_in_pages_readable(), this one copes
341  * with more than two userspace pages as well as handling the single page case
342  * elegantly.
343  *
344  * If you find this difficult to understand, then think of the while loop being
345  * the following code, except that we do without the integer variable ret:
346  *
347  *	do {
348  *		ret = __get_user(c, uaddr);
349  *		uaddr += PAGE_SIZE;
350  *	} while (!ret && uaddr < end);
351  *
352  * Note, the final __get_user() may well run out-of-bounds of the user buffer,
353  * but _not_ out-of-bounds of the page the user buffer belongs to, and since
354  * this is only a read and not a write, and since it is still in the same page,
355  * it should not matter and this makes the code much simpler.
356  */
357 static inline void ntfs_fault_in_pages_readable(const char __user *uaddr,
358 		int bytes)
359 {
360 	const char __user *end;
361 	volatile char c;
362 
363 	/* Set @end to the first byte outside the last page we care about. */
364 	end = (const char __user*)PAGE_ALIGN((ptrdiff_t __user)uaddr + bytes);
365 
366 	while (!__get_user(c, uaddr) && (uaddr += PAGE_SIZE, uaddr < end))
367 		;
368 }
369 
370 /**
371  * ntfs_fault_in_pages_readable_iovec -
372  *
373  * Same as ntfs_fault_in_pages_readable() but operates on an array of iovecs.
374  */
375 static inline void ntfs_fault_in_pages_readable_iovec(const struct iovec *iov,
376 		size_t iov_ofs, int bytes)
377 {
378 	do {
379 		const char __user *buf;
380 		unsigned len;
381 
382 		buf = iov->iov_base + iov_ofs;
383 		len = iov->iov_len - iov_ofs;
384 		if (len > bytes)
385 			len = bytes;
386 		ntfs_fault_in_pages_readable(buf, len);
387 		bytes -= len;
388 		iov++;
389 		iov_ofs = 0;
390 	} while (bytes);
391 }
392 
393 /**
394  * __ntfs_grab_cache_pages - obtain a number of locked pages
395  * @mapping:	address space mapping from which to obtain page cache pages
396  * @index:	starting index in @mapping at which to begin obtaining pages
397  * @nr_pages:	number of page cache pages to obtain
398  * @pages:	array of pages in which to return the obtained page cache pages
399  * @cached_page: allocated but as yet unused page
400  * @lru_pvec:	lru-buffering pagevec of caller
401  *
402  * Obtain @nr_pages locked page cache pages from the mapping @maping and
403  * starting at index @index.
404  *
405  * If a page is newly created, increment its refcount and add it to the
406  * caller's lru-buffering pagevec @lru_pvec.
407  *
408  * This is the same as mm/filemap.c::__grab_cache_page(), except that @nr_pages
409  * are obtained at once instead of just one page and that 0 is returned on
410  * success and -errno on error.
411  *
412  * Note, the page locks are obtained in ascending page index order.
413  */
414 static inline int __ntfs_grab_cache_pages(struct address_space *mapping,
415 		pgoff_t index, const unsigned nr_pages, struct page **pages,
416 		struct page **cached_page, struct pagevec *lru_pvec)
417 {
418 	int err, nr;
419 
420 	BUG_ON(!nr_pages);
421 	err = nr = 0;
422 	do {
423 		pages[nr] = find_lock_page(mapping, index);
424 		if (!pages[nr]) {
425 			if (!*cached_page) {
426 				*cached_page = page_cache_alloc(mapping);
427 				if (unlikely(!*cached_page)) {
428 					err = -ENOMEM;
429 					goto err_out;
430 				}
431 			}
432 			err = add_to_page_cache(*cached_page, mapping, index,
433 					GFP_KERNEL);
434 			if (unlikely(err)) {
435 				if (err == -EEXIST)
436 					continue;
437 				goto err_out;
438 			}
439 			pages[nr] = *cached_page;
440 			page_cache_get(*cached_page);
441 			if (unlikely(!pagevec_add(lru_pvec, *cached_page)))
442 				__pagevec_lru_add(lru_pvec);
443 			*cached_page = NULL;
444 		}
445 		index++;
446 		nr++;
447 	} while (nr < nr_pages);
448 out:
449 	return err;
450 err_out:
451 	while (nr > 0) {
452 		unlock_page(pages[--nr]);
453 		page_cache_release(pages[nr]);
454 	}
455 	goto out;
456 }
457 
458 static inline int ntfs_submit_bh_for_read(struct buffer_head *bh)
459 {
460 	lock_buffer(bh);
461 	get_bh(bh);
462 	bh->b_end_io = end_buffer_read_sync;
463 	return submit_bh(READ, bh);
464 }
465 
466 /**
467  * ntfs_prepare_pages_for_non_resident_write - prepare pages for receiving data
468  * @pages:	array of destination pages
469  * @nr_pages:	number of pages in @pages
470  * @pos:	byte position in file at which the write begins
471  * @bytes:	number of bytes to be written
472  *
473  * This is called for non-resident attributes from ntfs_file_buffered_write()
474  * with i_mutex held on the inode (@pages[0]->mapping->host).  There are
475  * @nr_pages pages in @pages which are locked but not kmap()ped.  The source
476  * data has not yet been copied into the @pages.
477  *
478  * Need to fill any holes with actual clusters, allocate buffers if necessary,
479  * ensure all the buffers are mapped, and bring uptodate any buffers that are
480  * only partially being written to.
481  *
482  * If @nr_pages is greater than one, we are guaranteed that the cluster size is
483  * greater than PAGE_CACHE_SIZE, that all pages in @pages are entirely inside
484  * the same cluster and that they are the entirety of that cluster, and that
485  * the cluster is sparse, i.e. we need to allocate a cluster to fill the hole.
486  *
487  * i_size is not to be modified yet.
488  *
489  * Return 0 on success or -errno on error.
490  */
491 static int ntfs_prepare_pages_for_non_resident_write(struct page **pages,
492 		unsigned nr_pages, s64 pos, size_t bytes)
493 {
494 	VCN vcn, highest_vcn = 0, cpos, cend, bh_cpos, bh_cend;
495 	LCN lcn;
496 	s64 bh_pos, vcn_len, end, initialized_size;
497 	sector_t lcn_block;
498 	struct page *page;
499 	struct inode *vi;
500 	ntfs_inode *ni, *base_ni = NULL;
501 	ntfs_volume *vol;
502 	runlist_element *rl, *rl2;
503 	struct buffer_head *bh, *head, *wait[2], **wait_bh = wait;
504 	ntfs_attr_search_ctx *ctx = NULL;
505 	MFT_RECORD *m = NULL;
506 	ATTR_RECORD *a = NULL;
507 	unsigned long flags;
508 	u32 attr_rec_len = 0;
509 	unsigned blocksize, u;
510 	int err, mp_size;
511 	bool rl_write_locked, was_hole, is_retry;
512 	unsigned char blocksize_bits;
513 	struct {
514 		u8 runlist_merged:1;
515 		u8 mft_attr_mapped:1;
516 		u8 mp_rebuilt:1;
517 		u8 attr_switched:1;
518 	} status = { 0, 0, 0, 0 };
519 
520 	BUG_ON(!nr_pages);
521 	BUG_ON(!pages);
522 	BUG_ON(!*pages);
523 	vi = pages[0]->mapping->host;
524 	ni = NTFS_I(vi);
525 	vol = ni->vol;
526 	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
527 			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
528 			vi->i_ino, ni->type, pages[0]->index, nr_pages,
529 			(long long)pos, bytes);
530 	blocksize = vol->sb->s_blocksize;
531 	blocksize_bits = vol->sb->s_blocksize_bits;
532 	u = 0;
533 	do {
534 		struct page *page = pages[u];
535 		/*
536 		 * create_empty_buffers() will create uptodate/dirty buffers if
537 		 * the page is uptodate/dirty.
538 		 */
539 		if (!page_has_buffers(page)) {
540 			create_empty_buffers(page, blocksize, 0);
541 			if (unlikely(!page_has_buffers(page)))
542 				return -ENOMEM;
543 		}
544 	} while (++u < nr_pages);
545 	rl_write_locked = false;
546 	rl = NULL;
547 	err = 0;
548 	vcn = lcn = -1;
549 	vcn_len = 0;
550 	lcn_block = -1;
551 	was_hole = false;
552 	cpos = pos >> vol->cluster_size_bits;
553 	end = pos + bytes;
554 	cend = (end + vol->cluster_size - 1) >> vol->cluster_size_bits;
555 	/*
556 	 * Loop over each page and for each page over each buffer.  Use goto to
557 	 * reduce indentation.
558 	 */
559 	u = 0;
560 do_next_page:
561 	page = pages[u];
562 	bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
563 	bh = head = page_buffers(page);
564 	do {
565 		VCN cdelta;
566 		s64 bh_end;
567 		unsigned bh_cofs;
568 
569 		/* Clear buffer_new on all buffers to reinitialise state. */
570 		if (buffer_new(bh))
571 			clear_buffer_new(bh);
572 		bh_end = bh_pos + blocksize;
573 		bh_cpos = bh_pos >> vol->cluster_size_bits;
574 		bh_cofs = bh_pos & vol->cluster_size_mask;
575 		if (buffer_mapped(bh)) {
576 			/*
577 			 * The buffer is already mapped.  If it is uptodate,
578 			 * ignore it.
579 			 */
580 			if (buffer_uptodate(bh))
581 				continue;
582 			/*
583 			 * The buffer is not uptodate.  If the page is uptodate
584 			 * set the buffer uptodate and otherwise ignore it.
585 			 */
586 			if (PageUptodate(page)) {
587 				set_buffer_uptodate(bh);
588 				continue;
589 			}
590 			/*
591 			 * Neither the page nor the buffer are uptodate.  If
592 			 * the buffer is only partially being written to, we
593 			 * need to read it in before the write, i.e. now.
594 			 */
595 			if ((bh_pos < pos && bh_end > pos) ||
596 					(bh_pos < end && bh_end > end)) {
597 				/*
598 				 * If the buffer is fully or partially within
599 				 * the initialized size, do an actual read.
600 				 * Otherwise, simply zero the buffer.
601 				 */
602 				read_lock_irqsave(&ni->size_lock, flags);
603 				initialized_size = ni->initialized_size;
604 				read_unlock_irqrestore(&ni->size_lock, flags);
605 				if (bh_pos < initialized_size) {
606 					ntfs_submit_bh_for_read(bh);
607 					*wait_bh++ = bh;
608 				} else {
609 					zero_user_page(page, bh_offset(bh),
610 							blocksize, KM_USER0);
611 					set_buffer_uptodate(bh);
612 				}
613 			}
614 			continue;
615 		}
616 		/* Unmapped buffer.  Need to map it. */
617 		bh->b_bdev = vol->sb->s_bdev;
618 		/*
619 		 * If the current buffer is in the same clusters as the map
620 		 * cache, there is no need to check the runlist again.  The
621 		 * map cache is made up of @vcn, which is the first cached file
622 		 * cluster, @vcn_len which is the number of cached file
623 		 * clusters, @lcn is the device cluster corresponding to @vcn,
624 		 * and @lcn_block is the block number corresponding to @lcn.
625 		 */
626 		cdelta = bh_cpos - vcn;
627 		if (likely(!cdelta || (cdelta > 0 && cdelta < vcn_len))) {
628 map_buffer_cached:
629 			BUG_ON(lcn < 0);
630 			bh->b_blocknr = lcn_block +
631 					(cdelta << (vol->cluster_size_bits -
632 					blocksize_bits)) +
633 					(bh_cofs >> blocksize_bits);
634 			set_buffer_mapped(bh);
635 			/*
636 			 * If the page is uptodate so is the buffer.  If the
637 			 * buffer is fully outside the write, we ignore it if
638 			 * it was already allocated and we mark it dirty so it
639 			 * gets written out if we allocated it.  On the other
640 			 * hand, if we allocated the buffer but we are not
641 			 * marking it dirty we set buffer_new so we can do
642 			 * error recovery.
643 			 */
644 			if (PageUptodate(page)) {
645 				if (!buffer_uptodate(bh))
646 					set_buffer_uptodate(bh);
647 				if (unlikely(was_hole)) {
648 					/* We allocated the buffer. */
649 					unmap_underlying_metadata(bh->b_bdev,
650 							bh->b_blocknr);
651 					if (bh_end <= pos || bh_pos >= end)
652 						mark_buffer_dirty(bh);
653 					else
654 						set_buffer_new(bh);
655 				}
656 				continue;
657 			}
658 			/* Page is _not_ uptodate. */
659 			if (likely(!was_hole)) {
660 				/*
661 				 * Buffer was already allocated.  If it is not
662 				 * uptodate and is only partially being written
663 				 * to, we need to read it in before the write,
664 				 * i.e. now.
665 				 */
666 				if (!buffer_uptodate(bh) && bh_pos < end &&
667 						bh_end > pos &&
668 						(bh_pos < pos ||
669 						bh_end > end)) {
670 					/*
671 					 * If the buffer is fully or partially
672 					 * within the initialized size, do an
673 					 * actual read.  Otherwise, simply zero
674 					 * the buffer.
675 					 */
676 					read_lock_irqsave(&ni->size_lock,
677 							flags);
678 					initialized_size = ni->initialized_size;
679 					read_unlock_irqrestore(&ni->size_lock,
680 							flags);
681 					if (bh_pos < initialized_size) {
682 						ntfs_submit_bh_for_read(bh);
683 						*wait_bh++ = bh;
684 					} else {
685 						zero_user_page(page,
686 							bh_offset(bh),
687 							blocksize, KM_USER0);
688 						set_buffer_uptodate(bh);
689 					}
690 				}
691 				continue;
692 			}
693 			/* We allocated the buffer. */
694 			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
695 			/*
696 			 * If the buffer is fully outside the write, zero it,
697 			 * set it uptodate, and mark it dirty so it gets
698 			 * written out.  If it is partially being written to,
699 			 * zero region surrounding the write but leave it to
700 			 * commit write to do anything else.  Finally, if the
701 			 * buffer is fully being overwritten, do nothing.
702 			 */
703 			if (bh_end <= pos || bh_pos >= end) {
704 				if (!buffer_uptodate(bh)) {
705 					zero_user_page(page, bh_offset(bh),
706 							blocksize, KM_USER0);
707 					set_buffer_uptodate(bh);
708 				}
709 				mark_buffer_dirty(bh);
710 				continue;
711 			}
712 			set_buffer_new(bh);
713 			if (!buffer_uptodate(bh) &&
714 					(bh_pos < pos || bh_end > end)) {
715 				u8 *kaddr;
716 				unsigned pofs;
717 
718 				kaddr = kmap_atomic(page, KM_USER0);
719 				if (bh_pos < pos) {
720 					pofs = bh_pos & ~PAGE_CACHE_MASK;
721 					memset(kaddr + pofs, 0, pos - bh_pos);
722 				}
723 				if (bh_end > end) {
724 					pofs = end & ~PAGE_CACHE_MASK;
725 					memset(kaddr + pofs, 0, bh_end - end);
726 				}
727 				kunmap_atomic(kaddr, KM_USER0);
728 				flush_dcache_page(page);
729 			}
730 			continue;
731 		}
732 		/*
733 		 * Slow path: this is the first buffer in the cluster.  If it
734 		 * is outside allocated size and is not uptodate, zero it and
735 		 * set it uptodate.
736 		 */
737 		read_lock_irqsave(&ni->size_lock, flags);
738 		initialized_size = ni->allocated_size;
739 		read_unlock_irqrestore(&ni->size_lock, flags);
740 		if (bh_pos > initialized_size) {
741 			if (PageUptodate(page)) {
742 				if (!buffer_uptodate(bh))
743 					set_buffer_uptodate(bh);
744 			} else if (!buffer_uptodate(bh)) {
745 				zero_user_page(page, bh_offset(bh), blocksize,
746 						KM_USER0);
747 				set_buffer_uptodate(bh);
748 			}
749 			continue;
750 		}
751 		is_retry = false;
752 		if (!rl) {
753 			down_read(&ni->runlist.lock);
754 retry_remap:
755 			rl = ni->runlist.rl;
756 		}
757 		if (likely(rl != NULL)) {
758 			/* Seek to element containing target cluster. */
759 			while (rl->length && rl[1].vcn <= bh_cpos)
760 				rl++;
761 			lcn = ntfs_rl_vcn_to_lcn(rl, bh_cpos);
762 			if (likely(lcn >= 0)) {
763 				/*
764 				 * Successful remap, setup the map cache and
765 				 * use that to deal with the buffer.
766 				 */
767 				was_hole = false;
768 				vcn = bh_cpos;
769 				vcn_len = rl[1].vcn - vcn;
770 				lcn_block = lcn << (vol->cluster_size_bits -
771 						blocksize_bits);
772 				cdelta = 0;
773 				/*
774 				 * If the number of remaining clusters touched
775 				 * by the write is smaller or equal to the
776 				 * number of cached clusters, unlock the
777 				 * runlist as the map cache will be used from
778 				 * now on.
779 				 */
780 				if (likely(vcn + vcn_len >= cend)) {
781 					if (rl_write_locked) {
782 						up_write(&ni->runlist.lock);
783 						rl_write_locked = false;
784 					} else
785 						up_read(&ni->runlist.lock);
786 					rl = NULL;
787 				}
788 				goto map_buffer_cached;
789 			}
790 		} else
791 			lcn = LCN_RL_NOT_MAPPED;
792 		/*
793 		 * If it is not a hole and not out of bounds, the runlist is
794 		 * probably unmapped so try to map it now.
795 		 */
796 		if (unlikely(lcn != LCN_HOLE && lcn != LCN_ENOENT)) {
797 			if (likely(!is_retry && lcn == LCN_RL_NOT_MAPPED)) {
798 				/* Attempt to map runlist. */
799 				if (!rl_write_locked) {
800 					/*
801 					 * We need the runlist locked for
802 					 * writing, so if it is locked for
803 					 * reading relock it now and retry in
804 					 * case it changed whilst we dropped
805 					 * the lock.
806 					 */
807 					up_read(&ni->runlist.lock);
808 					down_write(&ni->runlist.lock);
809 					rl_write_locked = true;
810 					goto retry_remap;
811 				}
812 				err = ntfs_map_runlist_nolock(ni, bh_cpos,
813 						NULL);
814 				if (likely(!err)) {
815 					is_retry = true;
816 					goto retry_remap;
817 				}
818 				/*
819 				 * If @vcn is out of bounds, pretend @lcn is
820 				 * LCN_ENOENT.  As long as the buffer is out
821 				 * of bounds this will work fine.
822 				 */
823 				if (err == -ENOENT) {
824 					lcn = LCN_ENOENT;
825 					err = 0;
826 					goto rl_not_mapped_enoent;
827 				}
828 			} else
829 				err = -EIO;
830 			/* Failed to map the buffer, even after retrying. */
831 			bh->b_blocknr = -1;
832 			ntfs_error(vol->sb, "Failed to write to inode 0x%lx, "
833 					"attribute type 0x%x, vcn 0x%llx, "
834 					"vcn offset 0x%x, because its "
835 					"location on disk could not be "
836 					"determined%s (error code %i).",
837 					ni->mft_no, ni->type,
838 					(unsigned long long)bh_cpos,
839 					(unsigned)bh_pos &
840 					vol->cluster_size_mask,
841 					is_retry ? " even after retrying" : "",
842 					err);
843 			break;
844 		}
845 rl_not_mapped_enoent:
846 		/*
847 		 * The buffer is in a hole or out of bounds.  We need to fill
848 		 * the hole, unless the buffer is in a cluster which is not
849 		 * touched by the write, in which case we just leave the buffer
850 		 * unmapped.  This can only happen when the cluster size is
851 		 * less than the page cache size.
852 		 */
853 		if (unlikely(vol->cluster_size < PAGE_CACHE_SIZE)) {
854 			bh_cend = (bh_end + vol->cluster_size - 1) >>
855 					vol->cluster_size_bits;
856 			if ((bh_cend <= cpos || bh_cpos >= cend)) {
857 				bh->b_blocknr = -1;
858 				/*
859 				 * If the buffer is uptodate we skip it.  If it
860 				 * is not but the page is uptodate, we can set
861 				 * the buffer uptodate.  If the page is not
862 				 * uptodate, we can clear the buffer and set it
863 				 * uptodate.  Whether this is worthwhile is
864 				 * debatable and this could be removed.
865 				 */
866 				if (PageUptodate(page)) {
867 					if (!buffer_uptodate(bh))
868 						set_buffer_uptodate(bh);
869 				} else if (!buffer_uptodate(bh)) {
870 					zero_user_page(page, bh_offset(bh),
871 							blocksize, KM_USER0);
872 					set_buffer_uptodate(bh);
873 				}
874 				continue;
875 			}
876 		}
877 		/*
878 		 * Out of bounds buffer is invalid if it was not really out of
879 		 * bounds.
880 		 */
881 		BUG_ON(lcn != LCN_HOLE);
882 		/*
883 		 * We need the runlist locked for writing, so if it is locked
884 		 * for reading relock it now and retry in case it changed
885 		 * whilst we dropped the lock.
886 		 */
887 		BUG_ON(!rl);
888 		if (!rl_write_locked) {
889 			up_read(&ni->runlist.lock);
890 			down_write(&ni->runlist.lock);
891 			rl_write_locked = true;
892 			goto retry_remap;
893 		}
894 		/* Find the previous last allocated cluster. */
895 		BUG_ON(rl->lcn != LCN_HOLE);
896 		lcn = -1;
897 		rl2 = rl;
898 		while (--rl2 >= ni->runlist.rl) {
899 			if (rl2->lcn >= 0) {
900 				lcn = rl2->lcn + rl2->length;
901 				break;
902 			}
903 		}
904 		rl2 = ntfs_cluster_alloc(vol, bh_cpos, 1, lcn, DATA_ZONE,
905 				false);
906 		if (IS_ERR(rl2)) {
907 			err = PTR_ERR(rl2);
908 			ntfs_debug("Failed to allocate cluster, error code %i.",
909 					err);
910 			break;
911 		}
912 		lcn = rl2->lcn;
913 		rl = ntfs_runlists_merge(ni->runlist.rl, rl2);
914 		if (IS_ERR(rl)) {
915 			err = PTR_ERR(rl);
916 			if (err != -ENOMEM)
917 				err = -EIO;
918 			if (ntfs_cluster_free_from_rl(vol, rl2)) {
919 				ntfs_error(vol->sb, "Failed to release "
920 						"allocated cluster in error "
921 						"code path.  Run chkdsk to "
922 						"recover the lost cluster.");
923 				NVolSetErrors(vol);
924 			}
925 			ntfs_free(rl2);
926 			break;
927 		}
928 		ni->runlist.rl = rl;
929 		status.runlist_merged = 1;
930 		ntfs_debug("Allocated cluster, lcn 0x%llx.",
931 				(unsigned long long)lcn);
932 		/* Map and lock the mft record and get the attribute record. */
933 		if (!NInoAttr(ni))
934 			base_ni = ni;
935 		else
936 			base_ni = ni->ext.base_ntfs_ino;
937 		m = map_mft_record(base_ni);
938 		if (IS_ERR(m)) {
939 			err = PTR_ERR(m);
940 			break;
941 		}
942 		ctx = ntfs_attr_get_search_ctx(base_ni, m);
943 		if (unlikely(!ctx)) {
944 			err = -ENOMEM;
945 			unmap_mft_record(base_ni);
946 			break;
947 		}
948 		status.mft_attr_mapped = 1;
949 		err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
950 				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx);
951 		if (unlikely(err)) {
952 			if (err == -ENOENT)
953 				err = -EIO;
954 			break;
955 		}
956 		m = ctx->mrec;
957 		a = ctx->attr;
958 		/*
959 		 * Find the runlist element with which the attribute extent
960 		 * starts.  Note, we cannot use the _attr_ version because we
961 		 * have mapped the mft record.  That is ok because we know the
962 		 * runlist fragment must be mapped already to have ever gotten
963 		 * here, so we can just use the _rl_ version.
964 		 */
965 		vcn = sle64_to_cpu(a->data.non_resident.lowest_vcn);
966 		rl2 = ntfs_rl_find_vcn_nolock(rl, vcn);
967 		BUG_ON(!rl2);
968 		BUG_ON(!rl2->length);
969 		BUG_ON(rl2->lcn < LCN_HOLE);
970 		highest_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
971 		/*
972 		 * If @highest_vcn is zero, calculate the real highest_vcn
973 		 * (which can really be zero).
974 		 */
975 		if (!highest_vcn)
976 			highest_vcn = (sle64_to_cpu(
977 					a->data.non_resident.allocated_size) >>
978 					vol->cluster_size_bits) - 1;
979 		/*
980 		 * Determine the size of the mapping pairs array for the new
981 		 * extent, i.e. the old extent with the hole filled.
982 		 */
983 		mp_size = ntfs_get_size_for_mapping_pairs(vol, rl2, vcn,
984 				highest_vcn);
985 		if (unlikely(mp_size <= 0)) {
986 			if (!(err = mp_size))
987 				err = -EIO;
988 			ntfs_debug("Failed to get size for mapping pairs "
989 					"array, error code %i.", err);
990 			break;
991 		}
992 		/*
993 		 * Resize the attribute record to fit the new mapping pairs
994 		 * array.
995 		 */
996 		attr_rec_len = le32_to_cpu(a->length);
997 		err = ntfs_attr_record_resize(m, a, mp_size + le16_to_cpu(
998 				a->data.non_resident.mapping_pairs_offset));
999 		if (unlikely(err)) {
1000 			BUG_ON(err != -ENOSPC);
1001 			// TODO: Deal with this by using the current attribute
1002 			// and fill it with as much of the mapping pairs
1003 			// array as possible.  Then loop over each attribute
1004 			// extent rewriting the mapping pairs arrays as we go
1005 			// along and if when we reach the end we have not
1006 			// enough space, try to resize the last attribute
1007 			// extent and if even that fails, add a new attribute
1008 			// extent.
1009 			// We could also try to resize at each step in the hope
1010 			// that we will not need to rewrite every single extent.
1011 			// Note, we may need to decompress some extents to fill
1012 			// the runlist as we are walking the extents...
1013 			ntfs_error(vol->sb, "Not enough space in the mft "
1014 					"record for the extended attribute "
1015 					"record.  This case is not "
1016 					"implemented yet.");
1017 			err = -EOPNOTSUPP;
1018 			break ;
1019 		}
1020 		status.mp_rebuilt = 1;
1021 		/*
1022 		 * Generate the mapping pairs array directly into the attribute
1023 		 * record.
1024 		 */
1025 		err = ntfs_mapping_pairs_build(vol, (u8*)a + le16_to_cpu(
1026 				a->data.non_resident.mapping_pairs_offset),
1027 				mp_size, rl2, vcn, highest_vcn, NULL);
1028 		if (unlikely(err)) {
1029 			ntfs_error(vol->sb, "Cannot fill hole in inode 0x%lx, "
1030 					"attribute type 0x%x, because building "
1031 					"the mapping pairs failed with error "
1032 					"code %i.", vi->i_ino,
1033 					(unsigned)le32_to_cpu(ni->type), err);
1034 			err = -EIO;
1035 			break;
1036 		}
1037 		/* Update the highest_vcn but only if it was not set. */
1038 		if (unlikely(!a->data.non_resident.highest_vcn))
1039 			a->data.non_resident.highest_vcn =
1040 					cpu_to_sle64(highest_vcn);
1041 		/*
1042 		 * If the attribute is sparse/compressed, update the compressed
1043 		 * size in the ntfs_inode structure and the attribute record.
1044 		 */
1045 		if (likely(NInoSparse(ni) || NInoCompressed(ni))) {
1046 			/*
1047 			 * If we are not in the first attribute extent, switch
1048 			 * to it, but first ensure the changes will make it to
1049 			 * disk later.
1050 			 */
1051 			if (a->data.non_resident.lowest_vcn) {
1052 				flush_dcache_mft_record_page(ctx->ntfs_ino);
1053 				mark_mft_record_dirty(ctx->ntfs_ino);
1054 				ntfs_attr_reinit_search_ctx(ctx);
1055 				err = ntfs_attr_lookup(ni->type, ni->name,
1056 						ni->name_len, CASE_SENSITIVE,
1057 						0, NULL, 0, ctx);
1058 				if (unlikely(err)) {
1059 					status.attr_switched = 1;
1060 					break;
1061 				}
1062 				/* @m is not used any more so do not set it. */
1063 				a = ctx->attr;
1064 			}
1065 			write_lock_irqsave(&ni->size_lock, flags);
1066 			ni->itype.compressed.size += vol->cluster_size;
1067 			a->data.non_resident.compressed_size =
1068 					cpu_to_sle64(ni->itype.compressed.size);
1069 			write_unlock_irqrestore(&ni->size_lock, flags);
1070 		}
1071 		/* Ensure the changes make it to disk. */
1072 		flush_dcache_mft_record_page(ctx->ntfs_ino);
1073 		mark_mft_record_dirty(ctx->ntfs_ino);
1074 		ntfs_attr_put_search_ctx(ctx);
1075 		unmap_mft_record(base_ni);
1076 		/* Successfully filled the hole. */
1077 		status.runlist_merged = 0;
1078 		status.mft_attr_mapped = 0;
1079 		status.mp_rebuilt = 0;
1080 		/* Setup the map cache and use that to deal with the buffer. */
1081 		was_hole = true;
1082 		vcn = bh_cpos;
1083 		vcn_len = 1;
1084 		lcn_block = lcn << (vol->cluster_size_bits - blocksize_bits);
1085 		cdelta = 0;
1086 		/*
1087 		 * If the number of remaining clusters in the @pages is smaller
1088 		 * or equal to the number of cached clusters, unlock the
1089 		 * runlist as the map cache will be used from now on.
1090 		 */
1091 		if (likely(vcn + vcn_len >= cend)) {
1092 			up_write(&ni->runlist.lock);
1093 			rl_write_locked = false;
1094 			rl = NULL;
1095 		}
1096 		goto map_buffer_cached;
1097 	} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
1098 	/* If there are no errors, do the next page. */
1099 	if (likely(!err && ++u < nr_pages))
1100 		goto do_next_page;
1101 	/* If there are no errors, release the runlist lock if we took it. */
1102 	if (likely(!err)) {
1103 		if (unlikely(rl_write_locked)) {
1104 			up_write(&ni->runlist.lock);
1105 			rl_write_locked = false;
1106 		} else if (unlikely(rl))
1107 			up_read(&ni->runlist.lock);
1108 		rl = NULL;
1109 	}
1110 	/* If we issued read requests, let them complete. */
1111 	read_lock_irqsave(&ni->size_lock, flags);
1112 	initialized_size = ni->initialized_size;
1113 	read_unlock_irqrestore(&ni->size_lock, flags);
1114 	while (wait_bh > wait) {
1115 		bh = *--wait_bh;
1116 		wait_on_buffer(bh);
1117 		if (likely(buffer_uptodate(bh))) {
1118 			page = bh->b_page;
1119 			bh_pos = ((s64)page->index << PAGE_CACHE_SHIFT) +
1120 					bh_offset(bh);
1121 			/*
1122 			 * If the buffer overflows the initialized size, need
1123 			 * to zero the overflowing region.
1124 			 */
1125 			if (unlikely(bh_pos + blocksize > initialized_size)) {
1126 				int ofs = 0;
1127 
1128 				if (likely(bh_pos < initialized_size))
1129 					ofs = initialized_size - bh_pos;
1130 				zero_user_page(page, bh_offset(bh) + ofs,
1131 						blocksize - ofs, KM_USER0);
1132 			}
1133 		} else /* if (unlikely(!buffer_uptodate(bh))) */
1134 			err = -EIO;
1135 	}
1136 	if (likely(!err)) {
1137 		/* Clear buffer_new on all buffers. */
1138 		u = 0;
1139 		do {
1140 			bh = head = page_buffers(pages[u]);
1141 			do {
1142 				if (buffer_new(bh))
1143 					clear_buffer_new(bh);
1144 			} while ((bh = bh->b_this_page) != head);
1145 		} while (++u < nr_pages);
1146 		ntfs_debug("Done.");
1147 		return err;
1148 	}
1149 	if (status.attr_switched) {
1150 		/* Get back to the attribute extent we modified. */
1151 		ntfs_attr_reinit_search_ctx(ctx);
1152 		if (ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
1153 				CASE_SENSITIVE, bh_cpos, NULL, 0, ctx)) {
1154 			ntfs_error(vol->sb, "Failed to find required "
1155 					"attribute extent of attribute in "
1156 					"error code path.  Run chkdsk to "
1157 					"recover.");
1158 			write_lock_irqsave(&ni->size_lock, flags);
1159 			ni->itype.compressed.size += vol->cluster_size;
1160 			write_unlock_irqrestore(&ni->size_lock, flags);
1161 			flush_dcache_mft_record_page(ctx->ntfs_ino);
1162 			mark_mft_record_dirty(ctx->ntfs_ino);
1163 			/*
1164 			 * The only thing that is now wrong is the compressed
1165 			 * size of the base attribute extent which chkdsk
1166 			 * should be able to fix.
1167 			 */
1168 			NVolSetErrors(vol);
1169 		} else {
1170 			m = ctx->mrec;
1171 			a = ctx->attr;
1172 			status.attr_switched = 0;
1173 		}
1174 	}
1175 	/*
1176 	 * If the runlist has been modified, need to restore it by punching a
1177 	 * hole into it and we then need to deallocate the on-disk cluster as
1178 	 * well.  Note, we only modify the runlist if we are able to generate a
1179 	 * new mapping pairs array, i.e. only when the mapped attribute extent
1180 	 * is not switched.
1181 	 */
1182 	if (status.runlist_merged && !status.attr_switched) {
1183 		BUG_ON(!rl_write_locked);
1184 		/* Make the file cluster we allocated sparse in the runlist. */
1185 		if (ntfs_rl_punch_nolock(vol, &ni->runlist, bh_cpos, 1)) {
1186 			ntfs_error(vol->sb, "Failed to punch hole into "
1187 					"attribute runlist in error code "
1188 					"path.  Run chkdsk to recover the "
1189 					"lost cluster.");
1190 			NVolSetErrors(vol);
1191 		} else /* if (success) */ {
1192 			status.runlist_merged = 0;
1193 			/*
1194 			 * Deallocate the on-disk cluster we allocated but only
1195 			 * if we succeeded in punching its vcn out of the
1196 			 * runlist.
1197 			 */
1198 			down_write(&vol->lcnbmp_lock);
1199 			if (ntfs_bitmap_clear_bit(vol->lcnbmp_ino, lcn)) {
1200 				ntfs_error(vol->sb, "Failed to release "
1201 						"allocated cluster in error "
1202 						"code path.  Run chkdsk to "
1203 						"recover the lost cluster.");
1204 				NVolSetErrors(vol);
1205 			}
1206 			up_write(&vol->lcnbmp_lock);
1207 		}
1208 	}
1209 	/*
1210 	 * Resize the attribute record to its old size and rebuild the mapping
1211 	 * pairs array.  Note, we only can do this if the runlist has been
1212 	 * restored to its old state which also implies that the mapped
1213 	 * attribute extent is not switched.
1214 	 */
1215 	if (status.mp_rebuilt && !status.runlist_merged) {
1216 		if (ntfs_attr_record_resize(m, a, attr_rec_len)) {
1217 			ntfs_error(vol->sb, "Failed to restore attribute "
1218 					"record in error code path.  Run "
1219 					"chkdsk to recover.");
1220 			NVolSetErrors(vol);
1221 		} else /* if (success) */ {
1222 			if (ntfs_mapping_pairs_build(vol, (u8*)a +
1223 					le16_to_cpu(a->data.non_resident.
1224 					mapping_pairs_offset), attr_rec_len -
1225 					le16_to_cpu(a->data.non_resident.
1226 					mapping_pairs_offset), ni->runlist.rl,
1227 					vcn, highest_vcn, NULL)) {
1228 				ntfs_error(vol->sb, "Failed to restore "
1229 						"mapping pairs array in error "
1230 						"code path.  Run chkdsk to "
1231 						"recover.");
1232 				NVolSetErrors(vol);
1233 			}
1234 			flush_dcache_mft_record_page(ctx->ntfs_ino);
1235 			mark_mft_record_dirty(ctx->ntfs_ino);
1236 		}
1237 	}
1238 	/* Release the mft record and the attribute. */
1239 	if (status.mft_attr_mapped) {
1240 		ntfs_attr_put_search_ctx(ctx);
1241 		unmap_mft_record(base_ni);
1242 	}
1243 	/* Release the runlist lock. */
1244 	if (rl_write_locked)
1245 		up_write(&ni->runlist.lock);
1246 	else if (rl)
1247 		up_read(&ni->runlist.lock);
1248 	/*
1249 	 * Zero out any newly allocated blocks to avoid exposing stale data.
1250 	 * If BH_New is set, we know that the block was newly allocated above
1251 	 * and that it has not been fully zeroed and marked dirty yet.
1252 	 */
1253 	nr_pages = u;
1254 	u = 0;
1255 	end = bh_cpos << vol->cluster_size_bits;
1256 	do {
1257 		page = pages[u];
1258 		bh = head = page_buffers(page);
1259 		do {
1260 			if (u == nr_pages &&
1261 					((s64)page->index << PAGE_CACHE_SHIFT) +
1262 					bh_offset(bh) >= end)
1263 				break;
1264 			if (!buffer_new(bh))
1265 				continue;
1266 			clear_buffer_new(bh);
1267 			if (!buffer_uptodate(bh)) {
1268 				if (PageUptodate(page))
1269 					set_buffer_uptodate(bh);
1270 				else {
1271 					zero_user_page(page, bh_offset(bh),
1272 							blocksize, KM_USER0);
1273 					set_buffer_uptodate(bh);
1274 				}
1275 			}
1276 			mark_buffer_dirty(bh);
1277 		} while ((bh = bh->b_this_page) != head);
1278 	} while (++u <= nr_pages);
1279 	ntfs_error(vol->sb, "Failed.  Returning error code %i.", err);
1280 	return err;
1281 }
1282 
1283 /*
1284  * Copy as much as we can into the pages and return the number of bytes which
1285  * were sucessfully copied.  If a fault is encountered then clear the pages
1286  * out to (ofs + bytes) and return the number of bytes which were copied.
1287  */
1288 static inline size_t ntfs_copy_from_user(struct page **pages,
1289 		unsigned nr_pages, unsigned ofs, const char __user *buf,
1290 		size_t bytes)
1291 {
1292 	struct page **last_page = pages + nr_pages;
1293 	char *kaddr;
1294 	size_t total = 0;
1295 	unsigned len;
1296 	int left;
1297 
1298 	do {
1299 		len = PAGE_CACHE_SIZE - ofs;
1300 		if (len > bytes)
1301 			len = bytes;
1302 		kaddr = kmap_atomic(*pages, KM_USER0);
1303 		left = __copy_from_user_inatomic(kaddr + ofs, buf, len);
1304 		kunmap_atomic(kaddr, KM_USER0);
1305 		if (unlikely(left)) {
1306 			/* Do it the slow way. */
1307 			kaddr = kmap(*pages);
1308 			left = __copy_from_user(kaddr + ofs, buf, len);
1309 			kunmap(*pages);
1310 			if (unlikely(left))
1311 				goto err_out;
1312 		}
1313 		total += len;
1314 		bytes -= len;
1315 		if (!bytes)
1316 			break;
1317 		buf += len;
1318 		ofs = 0;
1319 	} while (++pages < last_page);
1320 out:
1321 	return total;
1322 err_out:
1323 	total += len - left;
1324 	/* Zero the rest of the target like __copy_from_user(). */
1325 	while (++pages < last_page) {
1326 		bytes -= len;
1327 		if (!bytes)
1328 			break;
1329 		len = PAGE_CACHE_SIZE;
1330 		if (len > bytes)
1331 			len = bytes;
1332 		zero_user_page(*pages, 0, len, KM_USER0);
1333 	}
1334 	goto out;
1335 }
1336 
1337 static size_t __ntfs_copy_from_user_iovec_inatomic(char *vaddr,
1338 		const struct iovec *iov, size_t iov_ofs, size_t bytes)
1339 {
1340 	size_t total = 0;
1341 
1342 	while (1) {
1343 		const char __user *buf = iov->iov_base + iov_ofs;
1344 		unsigned len;
1345 		size_t left;
1346 
1347 		len = iov->iov_len - iov_ofs;
1348 		if (len > bytes)
1349 			len = bytes;
1350 		left = __copy_from_user_inatomic(vaddr, buf, len);
1351 		total += len;
1352 		bytes -= len;
1353 		vaddr += len;
1354 		if (unlikely(left)) {
1355 			total -= left;
1356 			break;
1357 		}
1358 		if (!bytes)
1359 			break;
1360 		iov++;
1361 		iov_ofs = 0;
1362 	}
1363 	return total;
1364 }
1365 
1366 static inline void ntfs_set_next_iovec(const struct iovec **iovp,
1367 		size_t *iov_ofsp, size_t bytes)
1368 {
1369 	const struct iovec *iov = *iovp;
1370 	size_t iov_ofs = *iov_ofsp;
1371 
1372 	while (bytes) {
1373 		unsigned len;
1374 
1375 		len = iov->iov_len - iov_ofs;
1376 		if (len > bytes)
1377 			len = bytes;
1378 		bytes -= len;
1379 		iov_ofs += len;
1380 		if (iov->iov_len == iov_ofs) {
1381 			iov++;
1382 			iov_ofs = 0;
1383 		}
1384 	}
1385 	*iovp = iov;
1386 	*iov_ofsp = iov_ofs;
1387 }
1388 
1389 /*
1390  * This has the same side-effects and return value as ntfs_copy_from_user().
1391  * The difference is that on a fault we need to memset the remainder of the
1392  * pages (out to offset + bytes), to emulate ntfs_copy_from_user()'s
1393  * single-segment behaviour.
1394  *
1395  * We call the same helper (__ntfs_copy_from_user_iovec_inatomic()) both
1396  * when atomic and when not atomic.  This is ok because
1397  * __ntfs_copy_from_user_iovec_inatomic() calls __copy_from_user_inatomic()
1398  * and it is ok to call this when non-atomic.
1399  * Infact, the only difference between __copy_from_user_inatomic() and
1400  * __copy_from_user() is that the latter calls might_sleep() and the former
1401  * should not zero the tail of the buffer on error.  And on many
1402  * architectures __copy_from_user_inatomic() is just defined to
1403  * __copy_from_user() so it makes no difference at all on those architectures.
1404  */
1405 static inline size_t ntfs_copy_from_user_iovec(struct page **pages,
1406 		unsigned nr_pages, unsigned ofs, const struct iovec **iov,
1407 		size_t *iov_ofs, size_t bytes)
1408 {
1409 	struct page **last_page = pages + nr_pages;
1410 	char *kaddr;
1411 	size_t copied, len, total = 0;
1412 
1413 	do {
1414 		len = PAGE_CACHE_SIZE - ofs;
1415 		if (len > bytes)
1416 			len = bytes;
1417 		kaddr = kmap_atomic(*pages, KM_USER0);
1418 		copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
1419 				*iov, *iov_ofs, len);
1420 		kunmap_atomic(kaddr, KM_USER0);
1421 		if (unlikely(copied != len)) {
1422 			/* Do it the slow way. */
1423 			kaddr = kmap(*pages);
1424 			copied = __ntfs_copy_from_user_iovec_inatomic(kaddr + ofs,
1425 					*iov, *iov_ofs, len);
1426 			/*
1427 			 * Zero the rest of the target like __copy_from_user().
1428 			 */
1429 			memset(kaddr + ofs + copied, 0, len - copied);
1430 			kunmap(*pages);
1431 			if (unlikely(copied != len))
1432 				goto err_out;
1433 		}
1434 		total += len;
1435 		bytes -= len;
1436 		if (!bytes)
1437 			break;
1438 		ntfs_set_next_iovec(iov, iov_ofs, len);
1439 		ofs = 0;
1440 	} while (++pages < last_page);
1441 out:
1442 	return total;
1443 err_out:
1444 	total += copied;
1445 	/* Zero the rest of the target like __copy_from_user(). */
1446 	while (++pages < last_page) {
1447 		bytes -= len;
1448 		if (!bytes)
1449 			break;
1450 		len = PAGE_CACHE_SIZE;
1451 		if (len > bytes)
1452 			len = bytes;
1453 		zero_user_page(*pages, 0, len, KM_USER0);
1454 	}
1455 	goto out;
1456 }
1457 
1458 static inline void ntfs_flush_dcache_pages(struct page **pages,
1459 		unsigned nr_pages)
1460 {
1461 	BUG_ON(!nr_pages);
1462 	/*
1463 	 * Warning: Do not do the decrement at the same time as the call to
1464 	 * flush_dcache_page() because it is a NULL macro on i386 and hence the
1465 	 * decrement never happens so the loop never terminates.
1466 	 */
1467 	do {
1468 		--nr_pages;
1469 		flush_dcache_page(pages[nr_pages]);
1470 	} while (nr_pages > 0);
1471 }
1472 
1473 /**
1474  * ntfs_commit_pages_after_non_resident_write - commit the received data
1475  * @pages:	array of destination pages
1476  * @nr_pages:	number of pages in @pages
1477  * @pos:	byte position in file at which the write begins
1478  * @bytes:	number of bytes to be written
1479  *
1480  * See description of ntfs_commit_pages_after_write(), below.
1481  */
1482 static inline int ntfs_commit_pages_after_non_resident_write(
1483 		struct page **pages, const unsigned nr_pages,
1484 		s64 pos, size_t bytes)
1485 {
1486 	s64 end, initialized_size;
1487 	struct inode *vi;
1488 	ntfs_inode *ni, *base_ni;
1489 	struct buffer_head *bh, *head;
1490 	ntfs_attr_search_ctx *ctx;
1491 	MFT_RECORD *m;
1492 	ATTR_RECORD *a;
1493 	unsigned long flags;
1494 	unsigned blocksize, u;
1495 	int err;
1496 
1497 	vi = pages[0]->mapping->host;
1498 	ni = NTFS_I(vi);
1499 	blocksize = vi->i_sb->s_blocksize;
1500 	end = pos + bytes;
1501 	u = 0;
1502 	do {
1503 		s64 bh_pos;
1504 		struct page *page;
1505 		bool partial;
1506 
1507 		page = pages[u];
1508 		bh_pos = (s64)page->index << PAGE_CACHE_SHIFT;
1509 		bh = head = page_buffers(page);
1510 		partial = false;
1511 		do {
1512 			s64 bh_end;
1513 
1514 			bh_end = bh_pos + blocksize;
1515 			if (bh_end <= pos || bh_pos >= end) {
1516 				if (!buffer_uptodate(bh))
1517 					partial = true;
1518 			} else {
1519 				set_buffer_uptodate(bh);
1520 				mark_buffer_dirty(bh);
1521 			}
1522 		} while (bh_pos += blocksize, (bh = bh->b_this_page) != head);
1523 		/*
1524 		 * If all buffers are now uptodate but the page is not, set the
1525 		 * page uptodate.
1526 		 */
1527 		if (!partial && !PageUptodate(page))
1528 			SetPageUptodate(page);
1529 	} while (++u < nr_pages);
1530 	/*
1531 	 * Finally, if we do not need to update initialized_size or i_size we
1532 	 * are finished.
1533 	 */
1534 	read_lock_irqsave(&ni->size_lock, flags);
1535 	initialized_size = ni->initialized_size;
1536 	read_unlock_irqrestore(&ni->size_lock, flags);
1537 	if (end <= initialized_size) {
1538 		ntfs_debug("Done.");
1539 		return 0;
1540 	}
1541 	/*
1542 	 * Update initialized_size/i_size as appropriate, both in the inode and
1543 	 * the mft record.
1544 	 */
1545 	if (!NInoAttr(ni))
1546 		base_ni = ni;
1547 	else
1548 		base_ni = ni->ext.base_ntfs_ino;
1549 	/* Map, pin, and lock the mft record. */
1550 	m = map_mft_record(base_ni);
1551 	if (IS_ERR(m)) {
1552 		err = PTR_ERR(m);
1553 		m = NULL;
1554 		ctx = NULL;
1555 		goto err_out;
1556 	}
1557 	BUG_ON(!NInoNonResident(ni));
1558 	ctx = ntfs_attr_get_search_ctx(base_ni, m);
1559 	if (unlikely(!ctx)) {
1560 		err = -ENOMEM;
1561 		goto err_out;
1562 	}
1563 	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
1564 			CASE_SENSITIVE, 0, NULL, 0, ctx);
1565 	if (unlikely(err)) {
1566 		if (err == -ENOENT)
1567 			err = -EIO;
1568 		goto err_out;
1569 	}
1570 	a = ctx->attr;
1571 	BUG_ON(!a->non_resident);
1572 	write_lock_irqsave(&ni->size_lock, flags);
1573 	BUG_ON(end > ni->allocated_size);
1574 	ni->initialized_size = end;
1575 	a->data.non_resident.initialized_size = cpu_to_sle64(end);
1576 	if (end > i_size_read(vi)) {
1577 		i_size_write(vi, end);
1578 		a->data.non_resident.data_size =
1579 				a->data.non_resident.initialized_size;
1580 	}
1581 	write_unlock_irqrestore(&ni->size_lock, flags);
1582 	/* Mark the mft record dirty, so it gets written back. */
1583 	flush_dcache_mft_record_page(ctx->ntfs_ino);
1584 	mark_mft_record_dirty(ctx->ntfs_ino);
1585 	ntfs_attr_put_search_ctx(ctx);
1586 	unmap_mft_record(base_ni);
1587 	ntfs_debug("Done.");
1588 	return 0;
1589 err_out:
1590 	if (ctx)
1591 		ntfs_attr_put_search_ctx(ctx);
1592 	if (m)
1593 		unmap_mft_record(base_ni);
1594 	ntfs_error(vi->i_sb, "Failed to update initialized_size/i_size (error "
1595 			"code %i).", err);
1596 	if (err != -ENOMEM)
1597 		NVolSetErrors(ni->vol);
1598 	return err;
1599 }
1600 
1601 /**
1602  * ntfs_commit_pages_after_write - commit the received data
1603  * @pages:	array of destination pages
1604  * @nr_pages:	number of pages in @pages
1605  * @pos:	byte position in file at which the write begins
1606  * @bytes:	number of bytes to be written
1607  *
1608  * This is called from ntfs_file_buffered_write() with i_mutex held on the inode
1609  * (@pages[0]->mapping->host).  There are @nr_pages pages in @pages which are
1610  * locked but not kmap()ped.  The source data has already been copied into the
1611  * @page.  ntfs_prepare_pages_for_non_resident_write() has been called before
1612  * the data was copied (for non-resident attributes only) and it returned
1613  * success.
1614  *
1615  * Need to set uptodate and mark dirty all buffers within the boundary of the
1616  * write.  If all buffers in a page are uptodate we set the page uptodate, too.
1617  *
1618  * Setting the buffers dirty ensures that they get written out later when
1619  * ntfs_writepage() is invoked by the VM.
1620  *
1621  * Finally, we need to update i_size and initialized_size as appropriate both
1622  * in the inode and the mft record.
1623  *
1624  * This is modelled after fs/buffer.c::generic_commit_write(), which marks
1625  * buffers uptodate and dirty, sets the page uptodate if all buffers in the
1626  * page are uptodate, and updates i_size if the end of io is beyond i_size.  In
1627  * that case, it also marks the inode dirty.
1628  *
1629  * If things have gone as outlined in
1630  * ntfs_prepare_pages_for_non_resident_write(), we do not need to do any page
1631  * content modifications here for non-resident attributes.  For resident
1632  * attributes we need to do the uptodate bringing here which we combine with
1633  * the copying into the mft record which means we save one atomic kmap.
1634  *
1635  * Return 0 on success or -errno on error.
1636  */
1637 static int ntfs_commit_pages_after_write(struct page **pages,
1638 		const unsigned nr_pages, s64 pos, size_t bytes)
1639 {
1640 	s64 end, initialized_size;
1641 	loff_t i_size;
1642 	struct inode *vi;
1643 	ntfs_inode *ni, *base_ni;
1644 	struct page *page;
1645 	ntfs_attr_search_ctx *ctx;
1646 	MFT_RECORD *m;
1647 	ATTR_RECORD *a;
1648 	char *kattr, *kaddr;
1649 	unsigned long flags;
1650 	u32 attr_len;
1651 	int err;
1652 
1653 	BUG_ON(!nr_pages);
1654 	BUG_ON(!pages);
1655 	page = pages[0];
1656 	BUG_ON(!page);
1657 	vi = page->mapping->host;
1658 	ni = NTFS_I(vi);
1659 	ntfs_debug("Entering for inode 0x%lx, attribute type 0x%x, start page "
1660 			"index 0x%lx, nr_pages 0x%x, pos 0x%llx, bytes 0x%zx.",
1661 			vi->i_ino, ni->type, page->index, nr_pages,
1662 			(long long)pos, bytes);
1663 	if (NInoNonResident(ni))
1664 		return ntfs_commit_pages_after_non_resident_write(pages,
1665 				nr_pages, pos, bytes);
1666 	BUG_ON(nr_pages > 1);
1667 	/*
1668 	 * Attribute is resident, implying it is not compressed, encrypted, or
1669 	 * sparse.
1670 	 */
1671 	if (!NInoAttr(ni))
1672 		base_ni = ni;
1673 	else
1674 		base_ni = ni->ext.base_ntfs_ino;
1675 	BUG_ON(NInoNonResident(ni));
1676 	/* Map, pin, and lock the mft record. */
1677 	m = map_mft_record(base_ni);
1678 	if (IS_ERR(m)) {
1679 		err = PTR_ERR(m);
1680 		m = NULL;
1681 		ctx = NULL;
1682 		goto err_out;
1683 	}
1684 	ctx = ntfs_attr_get_search_ctx(base_ni, m);
1685 	if (unlikely(!ctx)) {
1686 		err = -ENOMEM;
1687 		goto err_out;
1688 	}
1689 	err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
1690 			CASE_SENSITIVE, 0, NULL, 0, ctx);
1691 	if (unlikely(err)) {
1692 		if (err == -ENOENT)
1693 			err = -EIO;
1694 		goto err_out;
1695 	}
1696 	a = ctx->attr;
1697 	BUG_ON(a->non_resident);
1698 	/* The total length of the attribute value. */
1699 	attr_len = le32_to_cpu(a->data.resident.value_length);
1700 	i_size = i_size_read(vi);
1701 	BUG_ON(attr_len != i_size);
1702 	BUG_ON(pos > attr_len);
1703 	end = pos + bytes;
1704 	BUG_ON(end > le32_to_cpu(a->length) -
1705 			le16_to_cpu(a->data.resident.value_offset));
1706 	kattr = (u8*)a + le16_to_cpu(a->data.resident.value_offset);
1707 	kaddr = kmap_atomic(page, KM_USER0);
1708 	/* Copy the received data from the page to the mft record. */
1709 	memcpy(kattr + pos, kaddr + pos, bytes);
1710 	/* Update the attribute length if necessary. */
1711 	if (end > attr_len) {
1712 		attr_len = end;
1713 		a->data.resident.value_length = cpu_to_le32(attr_len);
1714 	}
1715 	/*
1716 	 * If the page is not uptodate, bring the out of bounds area(s)
1717 	 * uptodate by copying data from the mft record to the page.
1718 	 */
1719 	if (!PageUptodate(page)) {
1720 		if (pos > 0)
1721 			memcpy(kaddr, kattr, pos);
1722 		if (end < attr_len)
1723 			memcpy(kaddr + end, kattr + end, attr_len - end);
1724 		/* Zero the region outside the end of the attribute value. */
1725 		memset(kaddr + attr_len, 0, PAGE_CACHE_SIZE - attr_len);
1726 		flush_dcache_page(page);
1727 		SetPageUptodate(page);
1728 	}
1729 	kunmap_atomic(kaddr, KM_USER0);
1730 	/* Update initialized_size/i_size if necessary. */
1731 	read_lock_irqsave(&ni->size_lock, flags);
1732 	initialized_size = ni->initialized_size;
1733 	BUG_ON(end > ni->allocated_size);
1734 	read_unlock_irqrestore(&ni->size_lock, flags);
1735 	BUG_ON(initialized_size != i_size);
1736 	if (end > initialized_size) {
1737 		unsigned long flags;
1738 
1739 		write_lock_irqsave(&ni->size_lock, flags);
1740 		ni->initialized_size = end;
1741 		i_size_write(vi, end);
1742 		write_unlock_irqrestore(&ni->size_lock, flags);
1743 	}
1744 	/* Mark the mft record dirty, so it gets written back. */
1745 	flush_dcache_mft_record_page(ctx->ntfs_ino);
1746 	mark_mft_record_dirty(ctx->ntfs_ino);
1747 	ntfs_attr_put_search_ctx(ctx);
1748 	unmap_mft_record(base_ni);
1749 	ntfs_debug("Done.");
1750 	return 0;
1751 err_out:
1752 	if (err == -ENOMEM) {
1753 		ntfs_warning(vi->i_sb, "Error allocating memory required to "
1754 				"commit the write.");
1755 		if (PageUptodate(page)) {
1756 			ntfs_warning(vi->i_sb, "Page is uptodate, setting "
1757 					"dirty so the write will be retried "
1758 					"later on by the VM.");
1759 			/*
1760 			 * Put the page on mapping->dirty_pages, but leave its
1761 			 * buffers' dirty state as-is.
1762 			 */
1763 			__set_page_dirty_nobuffers(page);
1764 			err = 0;
1765 		} else
1766 			ntfs_error(vi->i_sb, "Page is not uptodate.  Written "
1767 					"data has been lost.");
1768 	} else {
1769 		ntfs_error(vi->i_sb, "Resident attribute commit write failed "
1770 				"with error %i.", err);
1771 		NVolSetErrors(ni->vol);
1772 	}
1773 	if (ctx)
1774 		ntfs_attr_put_search_ctx(ctx);
1775 	if (m)
1776 		unmap_mft_record(base_ni);
1777 	return err;
1778 }
1779 
1780 /**
1781  * ntfs_file_buffered_write -
1782  *
1783  * Locking: The vfs is holding ->i_mutex on the inode.
1784  */
1785 static ssize_t ntfs_file_buffered_write(struct kiocb *iocb,
1786 		const struct iovec *iov, unsigned long nr_segs,
1787 		loff_t pos, loff_t *ppos, size_t count)
1788 {
1789 	struct file *file = iocb->ki_filp;
1790 	struct address_space *mapping = file->f_mapping;
1791 	struct inode *vi = mapping->host;
1792 	ntfs_inode *ni = NTFS_I(vi);
1793 	ntfs_volume *vol = ni->vol;
1794 	struct page *pages[NTFS_MAX_PAGES_PER_CLUSTER];
1795 	struct page *cached_page = NULL;
1796 	char __user *buf = NULL;
1797 	s64 end, ll;
1798 	VCN last_vcn;
1799 	LCN lcn;
1800 	unsigned long flags;
1801 	size_t bytes, iov_ofs = 0;	/* Offset in the current iovec. */
1802 	ssize_t status, written;
1803 	unsigned nr_pages;
1804 	int err;
1805 	struct pagevec lru_pvec;
1806 
1807 	ntfs_debug("Entering for i_ino 0x%lx, attribute type 0x%x, "
1808 			"pos 0x%llx, count 0x%lx.",
1809 			vi->i_ino, (unsigned)le32_to_cpu(ni->type),
1810 			(unsigned long long)pos, (unsigned long)count);
1811 	if (unlikely(!count))
1812 		return 0;
1813 	BUG_ON(NInoMstProtected(ni));
1814 	/*
1815 	 * If the attribute is not an index root and it is encrypted or
1816 	 * compressed, we cannot write to it yet.  Note we need to check for
1817 	 * AT_INDEX_ALLOCATION since this is the type of both directory and
1818 	 * index inodes.
1819 	 */
1820 	if (ni->type != AT_INDEX_ALLOCATION) {
1821 		/* If file is encrypted, deny access, just like NT4. */
1822 		if (NInoEncrypted(ni)) {
1823 			/*
1824 			 * Reminder for later: Encrypted files are _always_
1825 			 * non-resident so that the content can always be
1826 			 * encrypted.
1827 			 */
1828 			ntfs_debug("Denying write access to encrypted file.");
1829 			return -EACCES;
1830 		}
1831 		if (NInoCompressed(ni)) {
1832 			/* Only unnamed $DATA attribute can be compressed. */
1833 			BUG_ON(ni->type != AT_DATA);
1834 			BUG_ON(ni->name_len);
1835 			/*
1836 			 * Reminder for later: If resident, the data is not
1837 			 * actually compressed.  Only on the switch to non-
1838 			 * resident does compression kick in.  This is in
1839 			 * contrast to encrypted files (see above).
1840 			 */
1841 			ntfs_error(vi->i_sb, "Writing to compressed files is "
1842 					"not implemented yet.  Sorry.");
1843 			return -EOPNOTSUPP;
1844 		}
1845 	}
1846 	/*
1847 	 * If a previous ntfs_truncate() failed, repeat it and abort if it
1848 	 * fails again.
1849 	 */
1850 	if (unlikely(NInoTruncateFailed(ni))) {
1851 		down_write(&vi->i_alloc_sem);
1852 		err = ntfs_truncate(vi);
1853 		up_write(&vi->i_alloc_sem);
1854 		if (err || NInoTruncateFailed(ni)) {
1855 			if (!err)
1856 				err = -EIO;
1857 			ntfs_error(vol->sb, "Cannot perform write to inode "
1858 					"0x%lx, attribute type 0x%x, because "
1859 					"ntfs_truncate() failed (error code "
1860 					"%i).", vi->i_ino,
1861 					(unsigned)le32_to_cpu(ni->type), err);
1862 			return err;
1863 		}
1864 	}
1865 	/* The first byte after the write. */
1866 	end = pos + count;
1867 	/*
1868 	 * If the write goes beyond the allocated size, extend the allocation
1869 	 * to cover the whole of the write, rounded up to the nearest cluster.
1870 	 */
1871 	read_lock_irqsave(&ni->size_lock, flags);
1872 	ll = ni->allocated_size;
1873 	read_unlock_irqrestore(&ni->size_lock, flags);
1874 	if (end > ll) {
1875 		/* Extend the allocation without changing the data size. */
1876 		ll = ntfs_attr_extend_allocation(ni, end, -1, pos);
1877 		if (likely(ll >= 0)) {
1878 			BUG_ON(pos >= ll);
1879 			/* If the extension was partial truncate the write. */
1880 			if (end > ll) {
1881 				ntfs_debug("Truncating write to inode 0x%lx, "
1882 						"attribute type 0x%x, because "
1883 						"the allocation was only "
1884 						"partially extended.",
1885 						vi->i_ino, (unsigned)
1886 						le32_to_cpu(ni->type));
1887 				end = ll;
1888 				count = ll - pos;
1889 			}
1890 		} else {
1891 			err = ll;
1892 			read_lock_irqsave(&ni->size_lock, flags);
1893 			ll = ni->allocated_size;
1894 			read_unlock_irqrestore(&ni->size_lock, flags);
1895 			/* Perform a partial write if possible or fail. */
1896 			if (pos < ll) {
1897 				ntfs_debug("Truncating write to inode 0x%lx, "
1898 						"attribute type 0x%x, because "
1899 						"extending the allocation "
1900 						"failed (error code %i).",
1901 						vi->i_ino, (unsigned)
1902 						le32_to_cpu(ni->type), err);
1903 				end = ll;
1904 				count = ll - pos;
1905 			} else {
1906 				ntfs_error(vol->sb, "Cannot perform write to "
1907 						"inode 0x%lx, attribute type "
1908 						"0x%x, because extending the "
1909 						"allocation failed (error "
1910 						"code %i).", vi->i_ino,
1911 						(unsigned)
1912 						le32_to_cpu(ni->type), err);
1913 				return err;
1914 			}
1915 		}
1916 	}
1917 	pagevec_init(&lru_pvec, 0);
1918 	written = 0;
1919 	/*
1920 	 * If the write starts beyond the initialized size, extend it up to the
1921 	 * beginning of the write and initialize all non-sparse space between
1922 	 * the old initialized size and the new one.  This automatically also
1923 	 * increments the vfs inode->i_size to keep it above or equal to the
1924 	 * initialized_size.
1925 	 */
1926 	read_lock_irqsave(&ni->size_lock, flags);
1927 	ll = ni->initialized_size;
1928 	read_unlock_irqrestore(&ni->size_lock, flags);
1929 	if (pos > ll) {
1930 		err = ntfs_attr_extend_initialized(ni, pos, &cached_page,
1931 				&lru_pvec);
1932 		if (err < 0) {
1933 			ntfs_error(vol->sb, "Cannot perform write to inode "
1934 					"0x%lx, attribute type 0x%x, because "
1935 					"extending the initialized size "
1936 					"failed (error code %i).", vi->i_ino,
1937 					(unsigned)le32_to_cpu(ni->type), err);
1938 			status = err;
1939 			goto err_out;
1940 		}
1941 	}
1942 	/*
1943 	 * Determine the number of pages per cluster for non-resident
1944 	 * attributes.
1945 	 */
1946 	nr_pages = 1;
1947 	if (vol->cluster_size > PAGE_CACHE_SIZE && NInoNonResident(ni))
1948 		nr_pages = vol->cluster_size >> PAGE_CACHE_SHIFT;
1949 	/* Finally, perform the actual write. */
1950 	last_vcn = -1;
1951 	if (likely(nr_segs == 1))
1952 		buf = iov->iov_base;
1953 	do {
1954 		VCN vcn;
1955 		pgoff_t idx, start_idx;
1956 		unsigned ofs, do_pages, u;
1957 		size_t copied;
1958 
1959 		start_idx = idx = pos >> PAGE_CACHE_SHIFT;
1960 		ofs = pos & ~PAGE_CACHE_MASK;
1961 		bytes = PAGE_CACHE_SIZE - ofs;
1962 		do_pages = 1;
1963 		if (nr_pages > 1) {
1964 			vcn = pos >> vol->cluster_size_bits;
1965 			if (vcn != last_vcn) {
1966 				last_vcn = vcn;
1967 				/*
1968 				 * Get the lcn of the vcn the write is in.  If
1969 				 * it is a hole, need to lock down all pages in
1970 				 * the cluster.
1971 				 */
1972 				down_read(&ni->runlist.lock);
1973 				lcn = ntfs_attr_vcn_to_lcn_nolock(ni, pos >>
1974 						vol->cluster_size_bits, false);
1975 				up_read(&ni->runlist.lock);
1976 				if (unlikely(lcn < LCN_HOLE)) {
1977 					status = -EIO;
1978 					if (lcn == LCN_ENOMEM)
1979 						status = -ENOMEM;
1980 					else
1981 						ntfs_error(vol->sb, "Cannot "
1982 							"perform write to "
1983 							"inode 0x%lx, "
1984 							"attribute type 0x%x, "
1985 							"because the attribute "
1986 							"is corrupt.",
1987 							vi->i_ino, (unsigned)
1988 							le32_to_cpu(ni->type));
1989 					break;
1990 				}
1991 				if (lcn == LCN_HOLE) {
1992 					start_idx = (pos & ~(s64)
1993 							vol->cluster_size_mask)
1994 							>> PAGE_CACHE_SHIFT;
1995 					bytes = vol->cluster_size - (pos &
1996 							vol->cluster_size_mask);
1997 					do_pages = nr_pages;
1998 				}
1999 			}
2000 		}
2001 		if (bytes > count)
2002 			bytes = count;
2003 		/*
2004 		 * Bring in the user page(s) that we will copy from _first_.
2005 		 * Otherwise there is a nasty deadlock on copying from the same
2006 		 * page(s) as we are writing to, without it/them being marked
2007 		 * up-to-date.  Note, at present there is nothing to stop the
2008 		 * pages being swapped out between us bringing them into memory
2009 		 * and doing the actual copying.
2010 		 */
2011 		if (likely(nr_segs == 1))
2012 			ntfs_fault_in_pages_readable(buf, bytes);
2013 		else
2014 			ntfs_fault_in_pages_readable_iovec(iov, iov_ofs, bytes);
2015 		/* Get and lock @do_pages starting at index @start_idx. */
2016 		status = __ntfs_grab_cache_pages(mapping, start_idx, do_pages,
2017 				pages, &cached_page, &lru_pvec);
2018 		if (unlikely(status))
2019 			break;
2020 		/*
2021 		 * For non-resident attributes, we need to fill any holes with
2022 		 * actual clusters and ensure all bufferes are mapped.  We also
2023 		 * need to bring uptodate any buffers that are only partially
2024 		 * being written to.
2025 		 */
2026 		if (NInoNonResident(ni)) {
2027 			status = ntfs_prepare_pages_for_non_resident_write(
2028 					pages, do_pages, pos, bytes);
2029 			if (unlikely(status)) {
2030 				loff_t i_size;
2031 
2032 				do {
2033 					unlock_page(pages[--do_pages]);
2034 					page_cache_release(pages[do_pages]);
2035 				} while (do_pages);
2036 				/*
2037 				 * The write preparation may have instantiated
2038 				 * allocated space outside i_size.  Trim this
2039 				 * off again.  We can ignore any errors in this
2040 				 * case as we will just be waisting a bit of
2041 				 * allocated space, which is not a disaster.
2042 				 */
2043 				i_size = i_size_read(vi);
2044 				if (pos + bytes > i_size)
2045 					vmtruncate(vi, i_size);
2046 				break;
2047 			}
2048 		}
2049 		u = (pos >> PAGE_CACHE_SHIFT) - pages[0]->index;
2050 		if (likely(nr_segs == 1)) {
2051 			copied = ntfs_copy_from_user(pages + u, do_pages - u,
2052 					ofs, buf, bytes);
2053 			buf += copied;
2054 		} else
2055 			copied = ntfs_copy_from_user_iovec(pages + u,
2056 					do_pages - u, ofs, &iov, &iov_ofs,
2057 					bytes);
2058 		ntfs_flush_dcache_pages(pages + u, do_pages - u);
2059 		status = ntfs_commit_pages_after_write(pages, do_pages, pos,
2060 				bytes);
2061 		if (likely(!status)) {
2062 			written += copied;
2063 			count -= copied;
2064 			pos += copied;
2065 			if (unlikely(copied != bytes))
2066 				status = -EFAULT;
2067 		}
2068 		do {
2069 			unlock_page(pages[--do_pages]);
2070 			mark_page_accessed(pages[do_pages]);
2071 			page_cache_release(pages[do_pages]);
2072 		} while (do_pages);
2073 		if (unlikely(status))
2074 			break;
2075 		balance_dirty_pages_ratelimited(mapping);
2076 		cond_resched();
2077 	} while (count);
2078 err_out:
2079 	*ppos = pos;
2080 	if (cached_page)
2081 		page_cache_release(cached_page);
2082 	/* For now, when the user asks for O_SYNC, we actually give O_DSYNC. */
2083 	if (likely(!status)) {
2084 		if (unlikely((file->f_flags & O_SYNC) || IS_SYNC(vi))) {
2085 			if (!mapping->a_ops->writepage || !is_sync_kiocb(iocb))
2086 				status = generic_osync_inode(vi, mapping,
2087 						OSYNC_METADATA|OSYNC_DATA);
2088 		}
2089   	}
2090 	pagevec_lru_add(&lru_pvec);
2091 	ntfs_debug("Done.  Returning %s (written 0x%lx, status %li).",
2092 			written ? "written" : "status", (unsigned long)written,
2093 			(long)status);
2094 	return written ? written : status;
2095 }
2096 
2097 /**
2098  * ntfs_file_aio_write_nolock -
2099  */
2100 static ssize_t ntfs_file_aio_write_nolock(struct kiocb *iocb,
2101 		const struct iovec *iov, unsigned long nr_segs, loff_t *ppos)
2102 {
2103 	struct file *file = iocb->ki_filp;
2104 	struct address_space *mapping = file->f_mapping;
2105 	struct inode *inode = mapping->host;
2106 	loff_t pos;
2107 	size_t count;		/* after file limit checks */
2108 	ssize_t written, err;
2109 
2110 	count = 0;
2111 	err = generic_segment_checks(iov, &nr_segs, &count, VERIFY_READ);
2112 	if (err)
2113 		return err;
2114 	pos = *ppos;
2115 	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
2116 	/* We can write back this queue in page reclaim. */
2117 	current->backing_dev_info = mapping->backing_dev_info;
2118 	written = 0;
2119 	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
2120 	if (err)
2121 		goto out;
2122 	if (!count)
2123 		goto out;
2124 	err = remove_suid(file->f_path.dentry);
2125 	if (err)
2126 		goto out;
2127 	file_update_time(file);
2128 	written = ntfs_file_buffered_write(iocb, iov, nr_segs, pos, ppos,
2129 			count);
2130 out:
2131 	current->backing_dev_info = NULL;
2132 	return written ? written : err;
2133 }
2134 
2135 /**
2136  * ntfs_file_aio_write -
2137  */
2138 static ssize_t ntfs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
2139 		unsigned long nr_segs, loff_t pos)
2140 {
2141 	struct file *file = iocb->ki_filp;
2142 	struct address_space *mapping = file->f_mapping;
2143 	struct inode *inode = mapping->host;
2144 	ssize_t ret;
2145 
2146 	BUG_ON(iocb->ki_pos != pos);
2147 
2148 	mutex_lock(&inode->i_mutex);
2149 	ret = ntfs_file_aio_write_nolock(iocb, iov, nr_segs, &iocb->ki_pos);
2150 	mutex_unlock(&inode->i_mutex);
2151 	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2152 		int err = sync_page_range(inode, mapping, pos, ret);
2153 		if (err < 0)
2154 			ret = err;
2155 	}
2156 	return ret;
2157 }
2158 
2159 /**
2160  * ntfs_file_writev -
2161  *
2162  * Basically the same as generic_file_writev() except that it ends up calling
2163  * ntfs_file_aio_write_nolock() instead of __generic_file_aio_write_nolock().
2164  */
2165 static ssize_t ntfs_file_writev(struct file *file, const struct iovec *iov,
2166 		unsigned long nr_segs, loff_t *ppos)
2167 {
2168 	struct address_space *mapping = file->f_mapping;
2169 	struct inode *inode = mapping->host;
2170 	struct kiocb kiocb;
2171 	ssize_t ret;
2172 
2173 	mutex_lock(&inode->i_mutex);
2174 	init_sync_kiocb(&kiocb, file);
2175 	ret = ntfs_file_aio_write_nolock(&kiocb, iov, nr_segs, ppos);
2176 	if (ret == -EIOCBQUEUED)
2177 		ret = wait_on_sync_kiocb(&kiocb);
2178 	mutex_unlock(&inode->i_mutex);
2179 	if (ret > 0 && ((file->f_flags & O_SYNC) || IS_SYNC(inode))) {
2180 		int err = sync_page_range(inode, mapping, *ppos - ret, ret);
2181 		if (err < 0)
2182 			ret = err;
2183 	}
2184 	return ret;
2185 }
2186 
2187 /**
2188  * ntfs_file_write - simple wrapper for ntfs_file_writev()
2189  */
2190 static ssize_t ntfs_file_write(struct file *file, const char __user *buf,
2191 		size_t count, loff_t *ppos)
2192 {
2193 	struct iovec local_iov = { .iov_base = (void __user *)buf,
2194 				   .iov_len = count };
2195 
2196 	return ntfs_file_writev(file, &local_iov, 1, ppos);
2197 }
2198 
2199 /**
2200  * ntfs_file_fsync - sync a file to disk
2201  * @filp:	file to be synced
2202  * @dentry:	dentry describing the file to sync
2203  * @datasync:	if non-zero only flush user data and not metadata
2204  *
2205  * Data integrity sync of a file to disk.  Used for fsync, fdatasync, and msync
2206  * system calls.  This function is inspired by fs/buffer.c::file_fsync().
2207  *
2208  * If @datasync is false, write the mft record and all associated extent mft
2209  * records as well as the $DATA attribute and then sync the block device.
2210  *
2211  * If @datasync is true and the attribute is non-resident, we skip the writing
2212  * of the mft record and all associated extent mft records (this might still
2213  * happen due to the write_inode_now() call).
2214  *
2215  * Also, if @datasync is true, we do not wait on the inode to be written out
2216  * but we always wait on the page cache pages to be written out.
2217  *
2218  * Note: In the past @filp could be NULL so we ignore it as we don't need it
2219  * anyway.
2220  *
2221  * Locking: Caller must hold i_mutex on the inode.
2222  *
2223  * TODO: We should probably also write all attribute/index inodes associated
2224  * with this inode but since we have no simple way of getting to them we ignore
2225  * this problem for now.
2226  */
2227 static int ntfs_file_fsync(struct file *filp, struct dentry *dentry,
2228 		int datasync)
2229 {
2230 	struct inode *vi = dentry->d_inode;
2231 	int err, ret = 0;
2232 
2233 	ntfs_debug("Entering for inode 0x%lx.", vi->i_ino);
2234 	BUG_ON(S_ISDIR(vi->i_mode));
2235 	if (!datasync || !NInoNonResident(NTFS_I(vi)))
2236 		ret = ntfs_write_inode(vi, 1);
2237 	write_inode_now(vi, !datasync);
2238 	/*
2239 	 * NOTE: If we were to use mapping->private_list (see ext2 and
2240 	 * fs/buffer.c) for dirty blocks then we could optimize the below to be
2241 	 * sync_mapping_buffers(vi->i_mapping).
2242 	 */
2243 	err = sync_blockdev(vi->i_sb->s_bdev);
2244 	if (unlikely(err && !ret))
2245 		ret = err;
2246 	if (likely(!ret))
2247 		ntfs_debug("Done.");
2248 	else
2249 		ntfs_warning(vi->i_sb, "Failed to f%ssync inode 0x%lx.  Error "
2250 				"%u.", datasync ? "data" : "", vi->i_ino, -ret);
2251 	return ret;
2252 }
2253 
2254 #endif /* NTFS_RW */
2255 
2256 const struct file_operations ntfs_file_ops = {
2257 	.llseek		= generic_file_llseek,	 /* Seek inside file. */
2258 	.read		= do_sync_read,		 /* Read from file. */
2259 	.aio_read	= generic_file_aio_read, /* Async read from file. */
2260 #ifdef NTFS_RW
2261 	.write		= ntfs_file_write,	 /* Write to file. */
2262 	.aio_write	= ntfs_file_aio_write,	 /* Async write to file. */
2263 	/*.release	= ,*/			 /* Last file is closed.  See
2264 						    fs/ext2/file.c::
2265 						    ext2_release_file() for
2266 						    how to use this to discard
2267 						    preallocated space for
2268 						    write opened files. */
2269 	.fsync		= ntfs_file_fsync,	 /* Sync a file to disk. */
2270 	/*.aio_fsync	= ,*/			 /* Sync all outstanding async
2271 						    i/o operations on a
2272 						    kiocb. */
2273 #endif /* NTFS_RW */
2274 	/*.ioctl	= ,*/			 /* Perform function on the
2275 						    mounted filesystem. */
2276 	.mmap		= generic_file_mmap,	 /* Mmap file. */
2277 	.open		= ntfs_file_open,	 /* Open file. */
2278 	.sendfile	= generic_file_sendfile, /* Zero-copy data send with
2279 						    the data source being on
2280 						    the ntfs partition.  We do
2281 						    not need to care about the
2282 						    data destination. */
2283 	/*.sendpage	= ,*/			 /* Zero-copy data send with
2284 						    the data destination being
2285 						    on the ntfs partition.  We
2286 						    do not need to care about
2287 						    the data source. */
2288 };
2289 
2290 const struct inode_operations ntfs_file_inode_ops = {
2291 #ifdef NTFS_RW
2292 	.truncate	= ntfs_truncate_vfs,
2293 	.setattr	= ntfs_setattr,
2294 #endif /* NTFS_RW */
2295 };
2296 
2297 const struct file_operations ntfs_empty_file_ops = {};
2298 
2299 const struct inode_operations ntfs_empty_inode_ops = {};
2300