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1/**
2 * compress.c - NTFS kernel compressed attributes handling.
3 * Part of the Linux-NTFS project.
4 *
5 * Copyright (c) 2001-2004 Anton Altaparmakov
6 * Copyright (c) 2002 Richard Russon
7 *
8 * This program/include file is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License as published
10 * by the Free Software Foundation; either version 2 of the License, or
11 * (at your option) any later version.
12 *
13 * This program/include file is distributed in the hope that it will be
14 * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
15 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 * GNU General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public License
19 * along with this program (in the main directory of the Linux-NTFS
20 * distribution in the file COPYING); if not, write to the Free Software
21 * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22 */
23
24#include <linux/fs.h>
25#include <linux/buffer_head.h>
26#include <linux/blkdev.h>
27#include <linux/vmalloc.h>
28
29#include "attrib.h"
30#include "inode.h"
31#include "debug.h"
32#include "ntfs.h"
33
34/**
35 * ntfs_compression_constants - enum of constants used in the compression code
36 */
37typedef enum {
38 /* Token types and access mask. */
39 NTFS_SYMBOL_TOKEN = 0,
40 NTFS_PHRASE_TOKEN = 1,
41 NTFS_TOKEN_MASK = 1,
42
43 /* Compression sub-block constants. */
44 NTFS_SB_SIZE_MASK = 0x0fff,
45 NTFS_SB_SIZE = 0x1000,
46 NTFS_SB_IS_COMPRESSED = 0x8000,
47
48 /*
49 * The maximum compression block size is by definition 16 * the cluster
50 * size, with the maximum supported cluster size being 4kiB. Thus the
51 * maximum compression buffer size is 64kiB, so we use this when
52 * initializing the compression buffer.
53 */
54 NTFS_MAX_CB_SIZE = 64 * 1024,
55} ntfs_compression_constants;
56
57/**
58 * ntfs_compression_buffer - one buffer for the decompression engine
59 */
60static u8 *ntfs_compression_buffer = NULL;
61
62/**
63 * ntfs_cb_lock - spinlock which protects ntfs_compression_buffer
64 */
65static DEFINE_SPINLOCK(ntfs_cb_lock);
66
67/**
68 * allocate_compression_buffers - allocate the decompression buffers
69 *
70 * Caller has to hold the ntfs_lock semaphore.
71 *
72 * Return 0 on success or -ENOMEM if the allocations failed.
73 */
74int allocate_compression_buffers(void)
75{
76 BUG_ON(ntfs_compression_buffer);
77
78 ntfs_compression_buffer = vmalloc(NTFS_MAX_CB_SIZE);
79 if (!ntfs_compression_buffer)
80 return -ENOMEM;
81 return 0;
82}
83
84/**
85 * free_compression_buffers - free the decompression buffers
86 *
87 * Caller has to hold the ntfs_lock semaphore.
88 */
89void free_compression_buffers(void)
90{
91 BUG_ON(!ntfs_compression_buffer);
92 vfree(ntfs_compression_buffer);
93 ntfs_compression_buffer = NULL;
94}
95
96/**
97 * zero_partial_compressed_page - zero out of bounds compressed page region
98 */
99static void zero_partial_compressed_page(ntfs_inode *ni, struct page *page)
100{
101 u8 *kp = page_address(page);
102 unsigned int kp_ofs;
103
104 ntfs_debug("Zeroing page region outside initialized size.");
105 if (((s64)page->index << PAGE_CACHE_SHIFT) >= ni->initialized_size) {
106 /*
107 * FIXME: Using clear_page() will become wrong when we get
108 * PAGE_CACHE_SIZE != PAGE_SIZE but for now there is no problem.
109 */
110 clear_page(kp);
111 return;
112 }
113 kp_ofs = ni->initialized_size & ~PAGE_CACHE_MASK;
114 memset(kp + kp_ofs, 0, PAGE_CACHE_SIZE - kp_ofs);
115 return;
116}
117
118/**
119 * handle_bounds_compressed_page - test for&handle out of bounds compressed page
120 */
121static inline void handle_bounds_compressed_page(ntfs_inode *ni,
122 struct page *page)
123{
124 if ((page->index >= (ni->initialized_size >> PAGE_CACHE_SHIFT)) &&
125 (ni->initialized_size < VFS_I(ni)->i_size))
126 zero_partial_compressed_page(ni, page);
127 return;
128}
129
130/**
131 * ntfs_decompress - decompress a compression block into an array of pages
132 * @dest_pages: destination array of pages
133 * @dest_index: current index into @dest_pages (IN/OUT)
134 * @dest_ofs: current offset within @dest_pages[@dest_index] (IN/OUT)
135 * @dest_max_index: maximum index into @dest_pages (IN)
136 * @dest_max_ofs: maximum offset within @dest_pages[@dest_max_index] (IN)
137 * @xpage: the target page (-1 if none) (IN)
138 * @xpage_done: set to 1 if xpage was completed successfully (IN/OUT)
139 * @cb_start: compression block to decompress (IN)
140 * @cb_size: size of compression block @cb_start in bytes (IN)
141 *
142 * The caller must have disabled preemption. ntfs_decompress() reenables it when
143 * the critical section is finished.
144 *
145 * This decompresses the compression block @cb_start into the array of
146 * destination pages @dest_pages starting at index @dest_index into @dest_pages
147 * and at offset @dest_pos into the page @dest_pages[@dest_index].
148 *
149 * When the page @dest_pages[@xpage] is completed, @xpage_done is set to 1.
150 * If xpage is -1 or @xpage has not been completed, @xpage_done is not modified.
151 *
152 * @cb_start is a pointer to the compression block which needs decompressing
153 * and @cb_size is the size of @cb_start in bytes (8-64kiB).
154 *
155 * Return 0 if success or -EOVERFLOW on error in the compressed stream.
156 * @xpage_done indicates whether the target page (@dest_pages[@xpage]) was
157 * completed during the decompression of the compression block (@cb_start).
158 *
159 * Warning: This function *REQUIRES* PAGE_CACHE_SIZE >= 4096 or it will blow up
160 * unpredicatbly! You have been warned!
161 *
162 * Note to hackers: This function may not sleep until it has finished accessing
163 * the compression block @cb_start as it is a per-CPU buffer.
164 */
165static int ntfs_decompress(struct page *dest_pages[], int *dest_index,
166 int *dest_ofs, const int dest_max_index, const int dest_max_ofs,
167 const int xpage, char *xpage_done, u8 *const cb_start,
168 const u32 cb_size)
169{
170 /*
171 * Pointers into the compressed data, i.e. the compression block (cb),
172 * and the therein contained sub-blocks (sb).
173 */
174 u8 *cb_end = cb_start + cb_size; /* End of cb. */
175 u8 *cb = cb_start; /* Current position in cb. */
176 u8 *cb_sb_start = cb; /* Beginning of the current sb in the cb. */
177 u8 *cb_sb_end; /* End of current sb / beginning of next sb. */
178
179 /* Variables for uncompressed data / destination. */
180 struct page *dp; /* Current destination page being worked on. */
181 u8 *dp_addr; /* Current pointer into dp. */
182 u8 *dp_sb_start; /* Start of current sub-block in dp. */
183 u8 *dp_sb_end; /* End of current sb in dp (dp_sb_start +
184 NTFS_SB_SIZE). */
185 u16 do_sb_start; /* @dest_ofs when starting this sub-block. */
186 u16 do_sb_end; /* @dest_ofs of end of this sb (do_sb_start +
187 NTFS_SB_SIZE). */
188
189 /* Variables for tag and token parsing. */
190 u8 tag; /* Current tag. */
191 int token; /* Loop counter for the eight tokens in tag. */
192
193 /* Need this because we can't sleep, so need two stages. */
194 int completed_pages[dest_max_index - *dest_index + 1];
195 int nr_completed_pages = 0;
196
197 /* Default error code. */
198 int err = -EOVERFLOW;
199
200 ntfs_debug("Entering, cb_size = 0x%x.", cb_size);
201do_next_sb:
202 ntfs_debug("Beginning sub-block at offset = 0x%zx in the cb.",
203 cb - cb_start);
204 /*
205 * Have we reached the end of the compression block or the end of the
206 * decompressed data? The latter can happen for example if the current
207 * position in the compression block is one byte before its end so the
208 * first two checks do not detect it.
209 */
210 if (cb == cb_end || !le16_to_cpup((le16*)cb) ||
211 (*dest_index == dest_max_index &&
212 *dest_ofs == dest_max_ofs)) {
213 int i;
214
215 ntfs_debug("Completed. Returning success (0).");
216 err = 0;
217return_error:
218 /* We can sleep from now on, so we drop lock. */
219 spin_unlock(&ntfs_cb_lock);
220 /* Second stage: finalize completed pages. */
221 if (nr_completed_pages > 0) {
222 struct page *page = dest_pages[completed_pages[0]];
223 ntfs_inode *ni = NTFS_I(page->mapping->host);
224
225 for (i = 0; i < nr_completed_pages; i++) {
226 int di = completed_pages[i];
227
228 dp = dest_pages[di];
229 /*
230 * If we are outside the initialized size, zero
231 * the out of bounds page range.
232 */
233 handle_bounds_compressed_page(ni, dp);
234 flush_dcache_page(dp);
235 kunmap(dp);
236 SetPageUptodate(dp);
237 unlock_page(dp);
238 if (di == xpage)
239 *xpage_done = 1;
240 else
241 page_cache_release(dp);
242 dest_pages[di] = NULL;
243 }
244 }
245 return err;
246 }
247
248 /* Setup offsets for the current sub-block destination. */
249 do_sb_start = *dest_ofs;
250 do_sb_end = do_sb_start + NTFS_SB_SIZE;
251
252 /* Check that we are still within allowed boundaries. */
253 if (*dest_index == dest_max_index && do_sb_end > dest_max_ofs)
254 goto return_overflow;
255
256 /* Does the minimum size of a compressed sb overflow valid range? */
257 if (cb + 6 > cb_end)
258 goto return_overflow;
259
260 /* Setup the current sub-block source pointers and validate range. */
261 cb_sb_start = cb;
262 cb_sb_end = cb_sb_start + (le16_to_cpup((le16*)cb) & NTFS_SB_SIZE_MASK)
263 + 3;
264 if (cb_sb_end > cb_end)
265 goto return_overflow;
266
267 /* Get the current destination page. */
268 dp = dest_pages[*dest_index];
269 if (!dp) {
270 /* No page present. Skip decompression of this sub-block. */
271 cb = cb_sb_end;
272
273 /* Advance destination position to next sub-block. */
274 *dest_ofs = (*dest_ofs + NTFS_SB_SIZE) & ~PAGE_CACHE_MASK;
275 if (!*dest_ofs && (++*dest_index > dest_max_index))
276 goto return_overflow;
277 goto do_next_sb;
278 }
279
280 /* We have a valid destination page. Setup the destination pointers. */
281 dp_addr = (u8*)page_address(dp) + do_sb_start;
282
283 /* Now, we are ready to process the current sub-block (sb). */
284 if (!(le16_to_cpup((le16*)cb) & NTFS_SB_IS_COMPRESSED)) {
285 ntfs_debug("Found uncompressed sub-block.");
286 /* This sb is not compressed, just copy it into destination. */
287
288 /* Advance source position to first data byte. */
289 cb += 2;
290
291 /* An uncompressed sb must be full size. */
292 if (cb_sb_end - cb != NTFS_SB_SIZE)
293 goto return_overflow;
294
295 /* Copy the block and advance the source position. */
296 memcpy(dp_addr, cb, NTFS_SB_SIZE);
297 cb += NTFS_SB_SIZE;
298
299 /* Advance destination position to next sub-block. */
300 *dest_ofs += NTFS_SB_SIZE;
301 if (!(*dest_ofs &= ~PAGE_CACHE_MASK)) {
302finalize_page:
303 /*
304 * First stage: add current page index to array of
305 * completed pages.
306 */
307 completed_pages[nr_completed_pages++] = *dest_index;
308 if (++*dest_index > dest_max_index)
309 goto return_overflow;
310 }
311 goto do_next_sb;
312 }
313 ntfs_debug("Found compressed sub-block.");
314 /* This sb is compressed, decompress it into destination. */
315
316 /* Setup destination pointers. */
317 dp_sb_start = dp_addr;
318 dp_sb_end = dp_sb_start + NTFS_SB_SIZE;
319
320 /* Forward to the first tag in the sub-block. */
321 cb += 2;
322do_next_tag:
323 if (cb == cb_sb_end) {
324 /* Check if the decompressed sub-block was not full-length. */
325 if (dp_addr < dp_sb_end) {
326 int nr_bytes = do_sb_end - *dest_ofs;
327
328 ntfs_debug("Filling incomplete sub-block with "
329 "zeroes.");
330 /* Zero remainder and update destination position. */
331 memset(dp_addr, 0, nr_bytes);
332 *dest_ofs += nr_bytes;
333 }
334 /* We have finished the current sub-block. */
335 if (!(*dest_ofs &= ~PAGE_CACHE_MASK))
336 goto finalize_page;
337 goto do_next_sb;
338 }
339
340 /* Check we are still in range. */
341 if (cb > cb_sb_end || dp_addr > dp_sb_end)
342 goto return_overflow;
343
344 /* Get the next tag and advance to first token. */
345 tag = *cb++;
346
347 /* Parse the eight tokens described by the tag. */
348 for (token = 0; token < 8; token++, tag >>= 1) {
349 u16 lg, pt, length, max_non_overlap;
350 register u16 i;
351 u8 *dp_back_addr;
352
353 /* Check if we are done / still in range. */
354 if (cb >= cb_sb_end || dp_addr > dp_sb_end)
355 break;
356
357 /* Determine token type and parse appropriately.*/
358 if ((tag & NTFS_TOKEN_MASK) == NTFS_SYMBOL_TOKEN) {
359 /*
360 * We have a symbol token, copy the symbol across, and
361 * advance the source and destination positions.
362 */
363 *dp_addr++ = *cb++;
364 ++*dest_ofs;
365
366 /* Continue with the next token. */
367 continue;
368 }
369
370 /*
371 * We have a phrase token. Make sure it is not the first tag in
372 * the sb as this is illegal and would confuse the code below.
373 */
374 if (dp_addr == dp_sb_start)
375 goto return_overflow;
376
377 /*
378 * Determine the number of bytes to go back (p) and the number
379 * of bytes to copy (l). We use an optimized algorithm in which
380 * we first calculate log2(current destination position in sb),
381 * which allows determination of l and p in O(1) rather than
382 * O(n). We just need an arch-optimized log2() function now.
383 */
384 lg = 0;
385 for (i = *dest_ofs - do_sb_start - 1; i >= 0x10; i >>= 1)
386 lg++;
387
388 /* Get the phrase token into i. */
389 pt = le16_to_cpup((le16*)cb);
390
391 /*
392 * Calculate starting position of the byte sequence in
393 * the destination using the fact that p = (pt >> (12 - lg)) + 1
394 * and make sure we don't go too far back.
395 */
396 dp_back_addr = dp_addr - (pt >> (12 - lg)) - 1;
397 if (dp_back_addr < dp_sb_start)
398 goto return_overflow;
399
400 /* Now calculate the length of the byte sequence. */
401 length = (pt & (0xfff >> lg)) + 3;
402
403 /* Advance destination position and verify it is in range. */
404 *dest_ofs += length;
405 if (*dest_ofs > do_sb_end)
406 goto return_overflow;
407
408 /* The number of non-overlapping bytes. */
409 max_non_overlap = dp_addr - dp_back_addr;
410
411 if (length <= max_non_overlap) {
412 /* The byte sequence doesn't overlap, just copy it. */
413 memcpy(dp_addr, dp_back_addr, length);
414
415 /* Advance destination pointer. */
416 dp_addr += length;
417 } else {
418 /*
419 * The byte sequence does overlap, copy non-overlapping
420 * part and then do a slow byte by byte copy for the
421 * overlapping part. Also, advance the destination
422 * pointer.
423 */
424 memcpy(dp_addr, dp_back_addr, max_non_overlap);
425 dp_addr += max_non_overlap;
426 dp_back_addr += max_non_overlap;
427 length -= max_non_overlap;
428 while (length--)
429 *dp_addr++ = *dp_back_addr++;
430 }
431
432 /* Advance source position and continue with the next token. */
433 cb += 2;
434 }
435
436 /* No tokens left in the current tag. Continue with the next tag. */
437 goto do_next_tag;
438
439return_overflow:
440 ntfs_error(NULL, "Failed. Returning -EOVERFLOW.");
441 goto return_error;
442}
443
444/**
445 * ntfs_read_compressed_block - read a compressed block into the page cache
446 * @page: locked page in the compression block(s) we need to read
447 *
448 * When we are called the page has already been verified to be locked and the
449 * attribute is known to be non-resident, not encrypted, but compressed.
450 *
451 * 1. Determine which compression block(s) @page is in.
452 * 2. Get hold of all pages corresponding to this/these compression block(s).
453 * 3. Read the (first) compression block.
454 * 4. Decompress it into the corresponding pages.
455 * 5. Throw the compressed data away and proceed to 3. for the next compression
456 * block or return success if no more compression blocks left.
457 *
458 * Warning: We have to be careful what we do about existing pages. They might
459 * have been written to so that we would lose data if we were to just overwrite
460 * them with the out-of-date uncompressed data.
461 *
462 * FIXME: For PAGE_CACHE_SIZE > cb_size we are not doing the Right Thing(TM) at
463 * the end of the file I think. We need to detect this case and zero the out
464 * of bounds remainder of the page in question and mark it as handled. At the
465 * moment we would just return -EIO on such a page. This bug will only become
466 * apparent if pages are above 8kiB and the NTFS volume only uses 512 byte
467 * clusters so is probably not going to be seen by anyone. Still this should
468 * be fixed. (AIA)
469 *
470 * FIXME: Again for PAGE_CACHE_SIZE > cb_size we are screwing up both in
471 * handling sparse and compressed cbs. (AIA)
472 *
473 * FIXME: At the moment we don't do any zeroing out in the case that
474 * initialized_size is less than data_size. This should be safe because of the
475 * nature of the compression algorithm used. Just in case we check and output
476 * an error message in read inode if the two sizes are not equal for a
477 * compressed file. (AIA)
478 */
479int ntfs_read_compressed_block(struct page *page)
480{
481 struct address_space *mapping = page->mapping;
482 ntfs_inode *ni = NTFS_I(mapping->host);
483 ntfs_volume *vol = ni->vol;
484 struct super_block *sb = vol->sb;
485 runlist_element *rl;
486 unsigned long block_size = sb->s_blocksize;
487 unsigned char block_size_bits = sb->s_blocksize_bits;
488 u8 *cb, *cb_pos, *cb_end;
489 struct buffer_head **bhs;
490 unsigned long offset, index = page->index;
491 u32 cb_size = ni->itype.compressed.block_size;
492 u64 cb_size_mask = cb_size - 1UL;
493 VCN vcn;
494 LCN lcn;
495 /* The first wanted vcn (minimum alignment is PAGE_CACHE_SIZE). */
496 VCN start_vcn = (((s64)index << PAGE_CACHE_SHIFT) & ~cb_size_mask) >>
497 vol->cluster_size_bits;
498 /*
499 * The first vcn after the last wanted vcn (minumum alignment is again
500 * PAGE_CACHE_SIZE.
501 */
502 VCN end_vcn = ((((s64)(index + 1UL) << PAGE_CACHE_SHIFT) + cb_size - 1)
503 & ~cb_size_mask) >> vol->cluster_size_bits;
504 /* Number of compression blocks (cbs) in the wanted vcn range. */
505 unsigned int nr_cbs = (end_vcn - start_vcn) << vol->cluster_size_bits
506 >> ni->itype.compressed.block_size_bits;
507 /*
508 * Number of pages required to store the uncompressed data from all
509 * compression blocks (cbs) overlapping @page. Due to alignment
510 * guarantees of start_vcn and end_vcn, no need to round up here.
511 */
512 unsigned int nr_pages = (end_vcn - start_vcn) <<
513 vol->cluster_size_bits >> PAGE_CACHE_SHIFT;
514 unsigned int xpage, max_page, cur_page, cur_ofs, i;
515 unsigned int cb_clusters, cb_max_ofs;
516 int block, max_block, cb_max_page, bhs_size, nr_bhs, err = 0;
517 struct page **pages;
518 unsigned char xpage_done = 0;
519
520 ntfs_debug("Entering, page->index = 0x%lx, cb_size = 0x%x, nr_pages = "
521 "%i.", index, cb_size, nr_pages);
522 /*
523 * Bad things happen if we get here for anything that is not an
524 * unnamed $DATA attribute.
525 */
526 BUG_ON(ni->type != AT_DATA);
527 BUG_ON(ni->name_len);
528
529 pages = kmalloc(nr_pages * sizeof(struct page *), GFP_NOFS);
530
531 /* Allocate memory to store the buffer heads we need. */
532 bhs_size = cb_size / block_size * sizeof(struct buffer_head *);
533 bhs = kmalloc(bhs_size, GFP_NOFS);
534
535 if (unlikely(!pages || !bhs)) {
536 kfree(bhs);
537 kfree(pages);
538 SetPageError(page);
539 unlock_page(page);
540 ntfs_error(vol->sb, "Failed to allocate internal buffers.");
541 return -ENOMEM;
542 }
543
544 /*
545 * We have already been given one page, this is the one we must do.
546 * Once again, the alignment guarantees keep it simple.
547 */
548 offset = start_vcn << vol->cluster_size_bits >> PAGE_CACHE_SHIFT;
549 xpage = index - offset;
550 pages[xpage] = page;
551 /*
552 * The remaining pages need to be allocated and inserted into the page
553 * cache, alignment guarantees keep all the below much simpler. (-8
554 */
555 max_page = ((VFS_I(ni)->i_size + PAGE_CACHE_SIZE - 1) >>
556 PAGE_CACHE_SHIFT) - offset;
557 if (nr_pages < max_page)
558 max_page = nr_pages;
559 for (i = 0; i < max_page; i++, offset++) {
560 if (i != xpage)
561 pages[i] = grab_cache_page_nowait(mapping, offset);
562 page = pages[i];
563 if (page) {
564 /*
565 * We only (re)read the page if it isn't already read
566 * in and/or dirty or we would be losing data or at
567 * least wasting our time.
568 */
569 if (!PageDirty(page) && (!PageUptodate(page) ||
570 PageError(page))) {
571 ClearPageError(page);
572 kmap(page);
573 continue;
574 }
575 unlock_page(page);
576 page_cache_release(page);
577 pages[i] = NULL;
578 }
579 }
580
581 /*
582 * We have the runlist, and all the destination pages we need to fill.
583 * Now read the first compression block.
584 */
585 cur_page = 0;
586 cur_ofs = 0;
587 cb_clusters = ni->itype.compressed.block_clusters;
588do_next_cb:
589 nr_cbs--;
590 nr_bhs = 0;
591
592 /* Read all cb buffer heads one cluster at a time. */
593 rl = NULL;
594 for (vcn = start_vcn, start_vcn += cb_clusters; vcn < start_vcn;
595 vcn++) {
596 BOOL is_retry = FALSE;
597
598 if (!rl) {
599lock_retry_remap:
600 down_read(&ni->runlist.lock);
601 rl = ni->runlist.rl;
602 }
603 if (likely(rl != NULL)) {
604 /* Seek to element containing target vcn. */
605 while (rl->length && rl[1].vcn <= vcn)
606 rl++;
607 lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
608 } else
609 lcn = LCN_RL_NOT_MAPPED;
610 ntfs_debug("Reading vcn = 0x%llx, lcn = 0x%llx.",
611 (unsigned long long)vcn,
612 (unsigned long long)lcn);
613 if (lcn < 0) {
614 /*
615 * When we reach the first sparse cluster we have
616 * finished with the cb.
617 */
618 if (lcn == LCN_HOLE)
619 break;
620 if (is_retry || lcn != LCN_RL_NOT_MAPPED)
621 goto rl_err;
622 is_retry = TRUE;
623 /*
624 * Attempt to map runlist, dropping lock for the
625 * duration.
626 */
627 up_read(&ni->runlist.lock);
628 if (!ntfs_map_runlist(ni, vcn))
629 goto lock_retry_remap;
630 goto map_rl_err;
631 }
632 block = lcn << vol->cluster_size_bits >> block_size_bits;
633 /* Read the lcn from device in chunks of block_size bytes. */
634 max_block = block + (vol->cluster_size >> block_size_bits);
635 do {
636 ntfs_debug("block = 0x%x.", block);
637 if (unlikely(!(bhs[nr_bhs] = sb_getblk(sb, block))))
638 goto getblk_err;
639 nr_bhs++;
640 } while (++block < max_block);
641 }
642
643 /* Release the lock if we took it. */
644 if (rl)
645 up_read(&ni->runlist.lock);
646
647 /* Setup and initiate io on all buffer heads. */
648 for (i = 0; i < nr_bhs; i++) {
649 struct buffer_head *tbh = bhs[i];
650
651 if (unlikely(test_set_buffer_locked(tbh)))
652 continue;
653 if (unlikely(buffer_uptodate(tbh))) {
654 unlock_buffer(tbh);
655 continue;
656 }
657 get_bh(tbh);
658 tbh->b_end_io = end_buffer_read_sync;
659 submit_bh(READ, tbh);
660 }
661
662 /* Wait for io completion on all buffer heads. */
663 for (i = 0; i < nr_bhs; i++) {
664 struct buffer_head *tbh = bhs[i];
665
666 if (buffer_uptodate(tbh))
667 continue;
668 wait_on_buffer(tbh);
669 /*
670 * We need an optimization barrier here, otherwise we start
671 * hitting the below fixup code when accessing a loopback
672 * mounted ntfs partition. This indicates either there is a
673 * race condition in the loop driver or, more likely, gcc
674 * overoptimises the code without the barrier and it doesn't
675 * do the Right Thing(TM).
676 */
677 barrier();
678 if (unlikely(!buffer_uptodate(tbh))) {
679 ntfs_warning(vol->sb, "Buffer is unlocked but not "
680 "uptodate! Unplugging the disk queue "
681 "and rescheduling.");
682 get_bh(tbh);
683 blk_run_address_space(mapping);
684 schedule();
685 put_bh(tbh);
686 if (unlikely(!buffer_uptodate(tbh)))
687 goto read_err;
688 ntfs_warning(vol->sb, "Buffer is now uptodate. Good.");
689 }
690 }
691
692 /*
693 * Get the compression buffer. We must not sleep any more
694 * until we are finished with it.
695 */
696 spin_lock(&ntfs_cb_lock);
697 cb = ntfs_compression_buffer;
698
699 BUG_ON(!cb);
700
701 cb_pos = cb;
702 cb_end = cb + cb_size;
703
704 /* Copy the buffer heads into the contiguous buffer. */
705 for (i = 0; i < nr_bhs; i++) {
706 memcpy(cb_pos, bhs[i]->b_data, block_size);
707 cb_pos += block_size;
708 }
709
710 /* Just a precaution. */
711 if (cb_pos + 2 <= cb + cb_size)
712 *(u16*)cb_pos = 0;
713
714 /* Reset cb_pos back to the beginning. */
715 cb_pos = cb;
716
717 /* We now have both source (if present) and destination. */
718 ntfs_debug("Successfully read the compression block.");
719
720 /* The last page and maximum offset within it for the current cb. */
721 cb_max_page = (cur_page << PAGE_CACHE_SHIFT) + cur_ofs + cb_size;
722 cb_max_ofs = cb_max_page & ~PAGE_CACHE_MASK;
723 cb_max_page >>= PAGE_CACHE_SHIFT;
724
725 /* Catch end of file inside a compression block. */
726 if (cb_max_page > max_page)
727 cb_max_page = max_page;
728
729 if (vcn == start_vcn - cb_clusters) {
730 /* Sparse cb, zero out page range overlapping the cb. */
731 ntfs_debug("Found sparse compression block.");
732 /* We can sleep from now on, so we drop lock. */
733 spin_unlock(&ntfs_cb_lock);
734 if (cb_max_ofs)
735 cb_max_page--;
736 for (; cur_page < cb_max_page; cur_page++) {
737 page = pages[cur_page];
738 if (page) {
739 /*
740 * FIXME: Using clear_page() will become wrong
741 * when we get PAGE_CACHE_SIZE != PAGE_SIZE but
742 * for now there is no problem.
743 */
744 if (likely(!cur_ofs))
745 clear_page(page_address(page));
746 else
747 memset(page_address(page) + cur_ofs, 0,
748 PAGE_CACHE_SIZE -
749 cur_ofs);
750 flush_dcache_page(page);
751 kunmap(page);
752 SetPageUptodate(page);
753 unlock_page(page);
754 if (cur_page == xpage)
755 xpage_done = 1;
756 else
757 page_cache_release(page);
758 pages[cur_page] = NULL;
759 }
760 cb_pos += PAGE_CACHE_SIZE - cur_ofs;
761 cur_ofs = 0;
762 if (cb_pos >= cb_end)
763 break;
764 }
765 /* If we have a partial final page, deal with it now. */
766 if (cb_max_ofs && cb_pos < cb_end) {
767 page = pages[cur_page];
768 if (page)
769 memset(page_address(page) + cur_ofs, 0,
770 cb_max_ofs - cur_ofs);
771 /*
772 * No need to update cb_pos at this stage:
773 * cb_pos += cb_max_ofs - cur_ofs;
774 */
775 cur_ofs = cb_max_ofs;
776 }
777 } else if (vcn == start_vcn) {
778 /* We can't sleep so we need two stages. */
779 unsigned int cur2_page = cur_page;
780 unsigned int cur_ofs2 = cur_ofs;
781 u8 *cb_pos2 = cb_pos;
782
783 ntfs_debug("Found uncompressed compression block.");
784 /* Uncompressed cb, copy it to the destination pages. */
785 /*
786 * TODO: As a big optimization, we could detect this case
787 * before we read all the pages and use block_read_full_page()
788 * on all full pages instead (we still have to treat partial
789 * pages especially but at least we are getting rid of the
790 * synchronous io for the majority of pages.
791 * Or if we choose not to do the read-ahead/-behind stuff, we
792 * could just return block_read_full_page(pages[xpage]) as long
793 * as PAGE_CACHE_SIZE <= cb_size.
794 */
795 if (cb_max_ofs)
796 cb_max_page--;
797 /* First stage: copy data into destination pages. */
798 for (; cur_page < cb_max_page; cur_page++) {
799 page = pages[cur_page];
800 if (page)
801 memcpy(page_address(page) + cur_ofs, cb_pos,
802 PAGE_CACHE_SIZE - cur_ofs);
803 cb_pos += PAGE_CACHE_SIZE - cur_ofs;
804 cur_ofs = 0;
805 if (cb_pos >= cb_end)
806 break;
807 }
808 /* If we have a partial final page, deal with it now. */
809 if (cb_max_ofs && cb_pos < cb_end) {
810 page = pages[cur_page];
811 if (page)
812 memcpy(page_address(page) + cur_ofs, cb_pos,
813 cb_max_ofs - cur_ofs);
814 cb_pos += cb_max_ofs - cur_ofs;
815 cur_ofs = cb_max_ofs;
816 }
817 /* We can sleep from now on, so drop lock. */
818 spin_unlock(&ntfs_cb_lock);
819 /* Second stage: finalize pages. */
820 for (; cur2_page < cb_max_page; cur2_page++) {
821 page = pages[cur2_page];
822 if (page) {
823 /*
824 * If we are outside the initialized size, zero
825 * the out of bounds page range.
826 */
827 handle_bounds_compressed_page(ni, page);
828 flush_dcache_page(page);
829 kunmap(page);
830 SetPageUptodate(page);
831 unlock_page(page);
832 if (cur2_page == xpage)
833 xpage_done = 1;
834 else
835 page_cache_release(page);
836 pages[cur2_page] = NULL;
837 }
838 cb_pos2 += PAGE_CACHE_SIZE - cur_ofs2;
839 cur_ofs2 = 0;
840 if (cb_pos2 >= cb_end)
841 break;
842 }
843 } else {
844 /* Compressed cb, decompress it into the destination page(s). */
845 unsigned int prev_cur_page = cur_page;
846
847 ntfs_debug("Found compressed compression block.");
848 err = ntfs_decompress(pages, &cur_page, &cur_ofs,
849 cb_max_page, cb_max_ofs, xpage, &xpage_done,
850 cb_pos, cb_size - (cb_pos - cb));
851 /*
852 * We can sleep from now on, lock already dropped by
853 * ntfs_decompress().
854 */
855 if (err) {
856 ntfs_error(vol->sb, "ntfs_decompress() failed in inode "
857 "0x%lx with error code %i. Skipping "
858 "this compression block.",
859 ni->mft_no, -err);
860 /* Release the unfinished pages. */
861 for (; prev_cur_page < cur_page; prev_cur_page++) {
862 page = pages[prev_cur_page];
863 if (page) {
864 if (prev_cur_page == xpage &&
865 !xpage_done)
866 SetPageError(page);
867 flush_dcache_page(page);
868 kunmap(page);
869 unlock_page(page);
870 if (prev_cur_page != xpage)
871 page_cache_release(page);
872 pages[prev_cur_page] = NULL;
873 }
874 }
875 }
876 }
877
878 /* Release the buffer heads. */
879 for (i = 0; i < nr_bhs; i++)
880 brelse(bhs[i]);
881
882 /* Do we have more work to do? */
883 if (nr_cbs)
884 goto do_next_cb;
885
886 /* We no longer need the list of buffer heads. */
887 kfree(bhs);
888
889 /* Clean up if we have any pages left. Should never happen. */
890 for (cur_page = 0; cur_page < max_page; cur_page++) {
891 page = pages[cur_page];
892 if (page) {
893 ntfs_error(vol->sb, "Still have pages left! "
894 "Terminating them with extreme "
895 "prejudice. Inode 0x%lx, page index "
896 "0x%lx.", ni->mft_no, page->index);
897 if (cur_page == xpage && !xpage_done)
898 SetPageError(page);
899 flush_dcache_page(page);
900 kunmap(page);
901 unlock_page(page);
902 if (cur_page != xpage)
903 page_cache_release(page);
904 pages[cur_page] = NULL;
905 }
906 }
907
908 /* We no longer need the list of pages. */
909 kfree(pages);
910
911 /* If we have completed the requested page, we return success. */
912 if (likely(xpage_done))
913 return 0;
914
915 ntfs_debug("Failed. Returning error code %s.", err == -EOVERFLOW ?
916 "EOVERFLOW" : (!err ? "EIO" : "unkown error"));
917 return err < 0 ? err : -EIO;
918
919read_err:
920 ntfs_error(vol->sb, "IO error while reading compressed data.");
921 /* Release the buffer heads. */
922 for (i = 0; i < nr_bhs; i++)
923 brelse(bhs[i]);
924 goto err_out;
925
926map_rl_err:
927 ntfs_error(vol->sb, "ntfs_map_runlist() failed. Cannot read "
928 "compression block.");
929 goto err_out;
930
931rl_err:
932 up_read(&ni->runlist.lock);
933 ntfs_error(vol->sb, "ntfs_rl_vcn_to_lcn() failed. Cannot read "
934 "compression block.");
935 goto err_out;
936
937getblk_err:
938 up_read(&ni->runlist.lock);
939 ntfs_error(vol->sb, "getblk() failed. Cannot read compression block.");
940
941err_out:
942 kfree(bhs);
943 for (i = cur_page; i < max_page; i++) {
944 page = pages[i];
945 if (page) {
946 if (i == xpage && !xpage_done)
947 SetPageError(page);
948 flush_dcache_page(page);
949 kunmap(page);
950 unlock_page(page);
951 if (i != xpage)
952 page_cache_release(page);
953 }
954 }
955 kfree(pages);
956 return -EIO;
957}