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1// SPDX-License-Identifier: GPL-2.0-or-later
2/**
3 * compress.c - NTFS kernel compressed attributes handling.
4 * Part of the Linux-NTFS project.
5 *
6 * Copyright (c) 2001-2004 Anton Altaparmakov
7 * Copyright (c) 2002 Richard Russon
8 */
9
10#include <linux/fs.h>
11#include <linux/buffer_head.h>
12#include <linux/blkdev.h>
13#include <linux/vmalloc.h>
14#include <linux/slab.h>
15
16#include "attrib.h"
17#include "inode.h"
18#include "debug.h"
19#include "ntfs.h"
20
21/**
22 * ntfs_compression_constants - enum of constants used in the compression code
23 */
24typedef enum {
25 /* Token types and access mask. */
26 NTFS_SYMBOL_TOKEN = 0,
27 NTFS_PHRASE_TOKEN = 1,
28 NTFS_TOKEN_MASK = 1,
29
30 /* Compression sub-block constants. */
31 NTFS_SB_SIZE_MASK = 0x0fff,
32 NTFS_SB_SIZE = 0x1000,
33 NTFS_SB_IS_COMPRESSED = 0x8000,
34
35 /*
36 * The maximum compression block size is by definition 16 * the cluster
37 * size, with the maximum supported cluster size being 4kiB. Thus the
38 * maximum compression buffer size is 64kiB, so we use this when
39 * initializing the compression buffer.
40 */
41 NTFS_MAX_CB_SIZE = 64 * 1024,
42} ntfs_compression_constants;
43
44/**
45 * ntfs_compression_buffer - one buffer for the decompression engine
46 */
47static u8 *ntfs_compression_buffer;
48
49/**
50 * ntfs_cb_lock - spinlock which protects ntfs_compression_buffer
51 */
52static DEFINE_SPINLOCK(ntfs_cb_lock);
53
54/**
55 * allocate_compression_buffers - allocate the decompression buffers
56 *
57 * Caller has to hold the ntfs_lock mutex.
58 *
59 * Return 0 on success or -ENOMEM if the allocations failed.
60 */
61int allocate_compression_buffers(void)
62{
63 BUG_ON(ntfs_compression_buffer);
64
65 ntfs_compression_buffer = vmalloc(NTFS_MAX_CB_SIZE);
66 if (!ntfs_compression_buffer)
67 return -ENOMEM;
68 return 0;
69}
70
71/**
72 * free_compression_buffers - free the decompression buffers
73 *
74 * Caller has to hold the ntfs_lock mutex.
75 */
76void free_compression_buffers(void)
77{
78 BUG_ON(!ntfs_compression_buffer);
79 vfree(ntfs_compression_buffer);
80 ntfs_compression_buffer = NULL;
81}
82
83/**
84 * zero_partial_compressed_page - zero out of bounds compressed page region
85 */
86static void zero_partial_compressed_page(struct page *page,
87 const s64 initialized_size)
88{
89 u8 *kp = page_address(page);
90 unsigned int kp_ofs;
91
92 ntfs_debug("Zeroing page region outside initialized size.");
93 if (((s64)page->index << PAGE_SHIFT) >= initialized_size) {
94 clear_page(kp);
95 return;
96 }
97 kp_ofs = initialized_size & ~PAGE_MASK;
98 memset(kp + kp_ofs, 0, PAGE_SIZE - kp_ofs);
99 return;
100}
101
102/**
103 * handle_bounds_compressed_page - test for&handle out of bounds compressed page
104 */
105static inline void handle_bounds_compressed_page(struct page *page,
106 const loff_t i_size, const s64 initialized_size)
107{
108 if ((page->index >= (initialized_size >> PAGE_SHIFT)) &&
109 (initialized_size < i_size))
110 zero_partial_compressed_page(page, initialized_size);
111 return;
112}
113
114/**
115 * ntfs_decompress - decompress a compression block into an array of pages
116 * @dest_pages: destination array of pages
117 * @completed_pages: scratch space to track completed pages
118 * @dest_index: current index into @dest_pages (IN/OUT)
119 * @dest_ofs: current offset within @dest_pages[@dest_index] (IN/OUT)
120 * @dest_max_index: maximum index into @dest_pages (IN)
121 * @dest_max_ofs: maximum offset within @dest_pages[@dest_max_index] (IN)
122 * @xpage: the target page (-1 if none) (IN)
123 * @xpage_done: set to 1 if xpage was completed successfully (IN/OUT)
124 * @cb_start: compression block to decompress (IN)
125 * @cb_size: size of compression block @cb_start in bytes (IN)
126 * @i_size: file size when we started the read (IN)
127 * @initialized_size: initialized file size when we started the read (IN)
128 *
129 * The caller must have disabled preemption. ntfs_decompress() reenables it when
130 * the critical section is finished.
131 *
132 * This decompresses the compression block @cb_start into the array of
133 * destination pages @dest_pages starting at index @dest_index into @dest_pages
134 * and at offset @dest_pos into the page @dest_pages[@dest_index].
135 *
136 * When the page @dest_pages[@xpage] is completed, @xpage_done is set to 1.
137 * If xpage is -1 or @xpage has not been completed, @xpage_done is not modified.
138 *
139 * @cb_start is a pointer to the compression block which needs decompressing
140 * and @cb_size is the size of @cb_start in bytes (8-64kiB).
141 *
142 * Return 0 if success or -EOVERFLOW on error in the compressed stream.
143 * @xpage_done indicates whether the target page (@dest_pages[@xpage]) was
144 * completed during the decompression of the compression block (@cb_start).
145 *
146 * Warning: This function *REQUIRES* PAGE_SIZE >= 4096 or it will blow up
147 * unpredicatbly! You have been warned!
148 *
149 * Note to hackers: This function may not sleep until it has finished accessing
150 * the compression block @cb_start as it is a per-CPU buffer.
151 */
152static int ntfs_decompress(struct page *dest_pages[], int completed_pages[],
153 int *dest_index, int *dest_ofs, const int dest_max_index,
154 const int dest_max_ofs, const int xpage, char *xpage_done,
155 u8 *const cb_start, const u32 cb_size, const loff_t i_size,
156 const s64 initialized_size)
157{
158 /*
159 * Pointers into the compressed data, i.e. the compression block (cb),
160 * and the therein contained sub-blocks (sb).
161 */
162 u8 *cb_end = cb_start + cb_size; /* End of cb. */
163 u8 *cb = cb_start; /* Current position in cb. */
164 u8 *cb_sb_start = cb; /* Beginning of the current sb in the cb. */
165 u8 *cb_sb_end; /* End of current sb / beginning of next sb. */
166
167 /* Variables for uncompressed data / destination. */
168 struct page *dp; /* Current destination page being worked on. */
169 u8 *dp_addr; /* Current pointer into dp. */
170 u8 *dp_sb_start; /* Start of current sub-block in dp. */
171 u8 *dp_sb_end; /* End of current sb in dp (dp_sb_start +
172 NTFS_SB_SIZE). */
173 u16 do_sb_start; /* @dest_ofs when starting this sub-block. */
174 u16 do_sb_end; /* @dest_ofs of end of this sb (do_sb_start +
175 NTFS_SB_SIZE). */
176
177 /* Variables for tag and token parsing. */
178 u8 tag; /* Current tag. */
179 int token; /* Loop counter for the eight tokens in tag. */
180 int nr_completed_pages = 0;
181
182 /* Default error code. */
183 int err = -EOVERFLOW;
184
185 ntfs_debug("Entering, cb_size = 0x%x.", cb_size);
186do_next_sb:
187 ntfs_debug("Beginning sub-block at offset = 0x%zx in the cb.",
188 cb - cb_start);
189 /*
190 * Have we reached the end of the compression block or the end of the
191 * decompressed data? The latter can happen for example if the current
192 * position in the compression block is one byte before its end so the
193 * first two checks do not detect it.
194 */
195 if (cb == cb_end || !le16_to_cpup((le16*)cb) ||
196 (*dest_index == dest_max_index &&
197 *dest_ofs == dest_max_ofs)) {
198 int i;
199
200 ntfs_debug("Completed. Returning success (0).");
201 err = 0;
202return_error:
203 /* We can sleep from now on, so we drop lock. */
204 spin_unlock(&ntfs_cb_lock);
205 /* Second stage: finalize completed pages. */
206 if (nr_completed_pages > 0) {
207 for (i = 0; i < nr_completed_pages; i++) {
208 int di = completed_pages[i];
209
210 dp = dest_pages[di];
211 /*
212 * If we are outside the initialized size, zero
213 * the out of bounds page range.
214 */
215 handle_bounds_compressed_page(dp, i_size,
216 initialized_size);
217 flush_dcache_page(dp);
218 kunmap(dp);
219 SetPageUptodate(dp);
220 unlock_page(dp);
221 if (di == xpage)
222 *xpage_done = 1;
223 else
224 put_page(dp);
225 dest_pages[di] = NULL;
226 }
227 }
228 return err;
229 }
230
231 /* Setup offsets for the current sub-block destination. */
232 do_sb_start = *dest_ofs;
233 do_sb_end = do_sb_start + NTFS_SB_SIZE;
234
235 /* Check that we are still within allowed boundaries. */
236 if (*dest_index == dest_max_index && do_sb_end > dest_max_ofs)
237 goto return_overflow;
238
239 /* Does the minimum size of a compressed sb overflow valid range? */
240 if (cb + 6 > cb_end)
241 goto return_overflow;
242
243 /* Setup the current sub-block source pointers and validate range. */
244 cb_sb_start = cb;
245 cb_sb_end = cb_sb_start + (le16_to_cpup((le16*)cb) & NTFS_SB_SIZE_MASK)
246 + 3;
247 if (cb_sb_end > cb_end)
248 goto return_overflow;
249
250 /* Get the current destination page. */
251 dp = dest_pages[*dest_index];
252 if (!dp) {
253 /* No page present. Skip decompression of this sub-block. */
254 cb = cb_sb_end;
255
256 /* Advance destination position to next sub-block. */
257 *dest_ofs = (*dest_ofs + NTFS_SB_SIZE) & ~PAGE_MASK;
258 if (!*dest_ofs && (++*dest_index > dest_max_index))
259 goto return_overflow;
260 goto do_next_sb;
261 }
262
263 /* We have a valid destination page. Setup the destination pointers. */
264 dp_addr = (u8*)page_address(dp) + do_sb_start;
265
266 /* Now, we are ready to process the current sub-block (sb). */
267 if (!(le16_to_cpup((le16*)cb) & NTFS_SB_IS_COMPRESSED)) {
268 ntfs_debug("Found uncompressed sub-block.");
269 /* This sb is not compressed, just copy it into destination. */
270
271 /* Advance source position to first data byte. */
272 cb += 2;
273
274 /* An uncompressed sb must be full size. */
275 if (cb_sb_end - cb != NTFS_SB_SIZE)
276 goto return_overflow;
277
278 /* Copy the block and advance the source position. */
279 memcpy(dp_addr, cb, NTFS_SB_SIZE);
280 cb += NTFS_SB_SIZE;
281
282 /* Advance destination position to next sub-block. */
283 *dest_ofs += NTFS_SB_SIZE;
284 if (!(*dest_ofs &= ~PAGE_MASK)) {
285finalize_page:
286 /*
287 * First stage: add current page index to array of
288 * completed pages.
289 */
290 completed_pages[nr_completed_pages++] = *dest_index;
291 if (++*dest_index > dest_max_index)
292 goto return_overflow;
293 }
294 goto do_next_sb;
295 }
296 ntfs_debug("Found compressed sub-block.");
297 /* This sb is compressed, decompress it into destination. */
298
299 /* Setup destination pointers. */
300 dp_sb_start = dp_addr;
301 dp_sb_end = dp_sb_start + NTFS_SB_SIZE;
302
303 /* Forward to the first tag in the sub-block. */
304 cb += 2;
305do_next_tag:
306 if (cb == cb_sb_end) {
307 /* Check if the decompressed sub-block was not full-length. */
308 if (dp_addr < dp_sb_end) {
309 int nr_bytes = do_sb_end - *dest_ofs;
310
311 ntfs_debug("Filling incomplete sub-block with "
312 "zeroes.");
313 /* Zero remainder and update destination position. */
314 memset(dp_addr, 0, nr_bytes);
315 *dest_ofs += nr_bytes;
316 }
317 /* We have finished the current sub-block. */
318 if (!(*dest_ofs &= ~PAGE_MASK))
319 goto finalize_page;
320 goto do_next_sb;
321 }
322
323 /* Check we are still in range. */
324 if (cb > cb_sb_end || dp_addr > dp_sb_end)
325 goto return_overflow;
326
327 /* Get the next tag and advance to first token. */
328 tag = *cb++;
329
330 /* Parse the eight tokens described by the tag. */
331 for (token = 0; token < 8; token++, tag >>= 1) {
332 u16 lg, pt, length, max_non_overlap;
333 register u16 i;
334 u8 *dp_back_addr;
335
336 /* Check if we are done / still in range. */
337 if (cb >= cb_sb_end || dp_addr > dp_sb_end)
338 break;
339
340 /* Determine token type and parse appropriately.*/
341 if ((tag & NTFS_TOKEN_MASK) == NTFS_SYMBOL_TOKEN) {
342 /*
343 * We have a symbol token, copy the symbol across, and
344 * advance the source and destination positions.
345 */
346 *dp_addr++ = *cb++;
347 ++*dest_ofs;
348
349 /* Continue with the next token. */
350 continue;
351 }
352
353 /*
354 * We have a phrase token. Make sure it is not the first tag in
355 * the sb as this is illegal and would confuse the code below.
356 */
357 if (dp_addr == dp_sb_start)
358 goto return_overflow;
359
360 /*
361 * Determine the number of bytes to go back (p) and the number
362 * of bytes to copy (l). We use an optimized algorithm in which
363 * we first calculate log2(current destination position in sb),
364 * which allows determination of l and p in O(1) rather than
365 * O(n). We just need an arch-optimized log2() function now.
366 */
367 lg = 0;
368 for (i = *dest_ofs - do_sb_start - 1; i >= 0x10; i >>= 1)
369 lg++;
370
371 /* Get the phrase token into i. */
372 pt = le16_to_cpup((le16*)cb);
373
374 /*
375 * Calculate starting position of the byte sequence in
376 * the destination using the fact that p = (pt >> (12 - lg)) + 1
377 * and make sure we don't go too far back.
378 */
379 dp_back_addr = dp_addr - (pt >> (12 - lg)) - 1;
380 if (dp_back_addr < dp_sb_start)
381 goto return_overflow;
382
383 /* Now calculate the length of the byte sequence. */
384 length = (pt & (0xfff >> lg)) + 3;
385
386 /* Advance destination position and verify it is in range. */
387 *dest_ofs += length;
388 if (*dest_ofs > do_sb_end)
389 goto return_overflow;
390
391 /* The number of non-overlapping bytes. */
392 max_non_overlap = dp_addr - dp_back_addr;
393
394 if (length <= max_non_overlap) {
395 /* The byte sequence doesn't overlap, just copy it. */
396 memcpy(dp_addr, dp_back_addr, length);
397
398 /* Advance destination pointer. */
399 dp_addr += length;
400 } else {
401 /*
402 * The byte sequence does overlap, copy non-overlapping
403 * part and then do a slow byte by byte copy for the
404 * overlapping part. Also, advance the destination
405 * pointer.
406 */
407 memcpy(dp_addr, dp_back_addr, max_non_overlap);
408 dp_addr += max_non_overlap;
409 dp_back_addr += max_non_overlap;
410 length -= max_non_overlap;
411 while (length--)
412 *dp_addr++ = *dp_back_addr++;
413 }
414
415 /* Advance source position and continue with the next token. */
416 cb += 2;
417 }
418
419 /* No tokens left in the current tag. Continue with the next tag. */
420 goto do_next_tag;
421
422return_overflow:
423 ntfs_error(NULL, "Failed. Returning -EOVERFLOW.");
424 goto return_error;
425}
426
427/**
428 * ntfs_read_compressed_block - read a compressed block into the page cache
429 * @page: locked page in the compression block(s) we need to read
430 *
431 * When we are called the page has already been verified to be locked and the
432 * attribute is known to be non-resident, not encrypted, but compressed.
433 *
434 * 1. Determine which compression block(s) @page is in.
435 * 2. Get hold of all pages corresponding to this/these compression block(s).
436 * 3. Read the (first) compression block.
437 * 4. Decompress it into the corresponding pages.
438 * 5. Throw the compressed data away and proceed to 3. for the next compression
439 * block or return success if no more compression blocks left.
440 *
441 * Warning: We have to be careful what we do about existing pages. They might
442 * have been written to so that we would lose data if we were to just overwrite
443 * them with the out-of-date uncompressed data.
444 *
445 * FIXME: For PAGE_SIZE > cb_size we are not doing the Right Thing(TM) at
446 * the end of the file I think. We need to detect this case and zero the out
447 * of bounds remainder of the page in question and mark it as handled. At the
448 * moment we would just return -EIO on such a page. This bug will only become
449 * apparent if pages are above 8kiB and the NTFS volume only uses 512 byte
450 * clusters so is probably not going to be seen by anyone. Still this should
451 * be fixed. (AIA)
452 *
453 * FIXME: Again for PAGE_SIZE > cb_size we are screwing up both in
454 * handling sparse and compressed cbs. (AIA)
455 *
456 * FIXME: At the moment we don't do any zeroing out in the case that
457 * initialized_size is less than data_size. This should be safe because of the
458 * nature of the compression algorithm used. Just in case we check and output
459 * an error message in read inode if the two sizes are not equal for a
460 * compressed file. (AIA)
461 */
462int ntfs_read_compressed_block(struct page *page)
463{
464 loff_t i_size;
465 s64 initialized_size;
466 struct address_space *mapping = page->mapping;
467 ntfs_inode *ni = NTFS_I(mapping->host);
468 ntfs_volume *vol = ni->vol;
469 struct super_block *sb = vol->sb;
470 runlist_element *rl;
471 unsigned long flags, block_size = sb->s_blocksize;
472 unsigned char block_size_bits = sb->s_blocksize_bits;
473 u8 *cb, *cb_pos, *cb_end;
474 struct buffer_head **bhs;
475 unsigned long offset, index = page->index;
476 u32 cb_size = ni->itype.compressed.block_size;
477 u64 cb_size_mask = cb_size - 1UL;
478 VCN vcn;
479 LCN lcn;
480 /* The first wanted vcn (minimum alignment is PAGE_SIZE). */
481 VCN start_vcn = (((s64)index << PAGE_SHIFT) & ~cb_size_mask) >>
482 vol->cluster_size_bits;
483 /*
484 * The first vcn after the last wanted vcn (minimum alignment is again
485 * PAGE_SIZE.
486 */
487 VCN end_vcn = ((((s64)(index + 1UL) << PAGE_SHIFT) + cb_size - 1)
488 & ~cb_size_mask) >> vol->cluster_size_bits;
489 /* Number of compression blocks (cbs) in the wanted vcn range. */
490 unsigned int nr_cbs = (end_vcn - start_vcn) << vol->cluster_size_bits
491 >> ni->itype.compressed.block_size_bits;
492 /*
493 * Number of pages required to store the uncompressed data from all
494 * compression blocks (cbs) overlapping @page. Due to alignment
495 * guarantees of start_vcn and end_vcn, no need to round up here.
496 */
497 unsigned int nr_pages = (end_vcn - start_vcn) <<
498 vol->cluster_size_bits >> PAGE_SHIFT;
499 unsigned int xpage, max_page, cur_page, cur_ofs, i;
500 unsigned int cb_clusters, cb_max_ofs;
501 int block, max_block, cb_max_page, bhs_size, nr_bhs, err = 0;
502 struct page **pages;
503 int *completed_pages;
504 unsigned char xpage_done = 0;
505
506 ntfs_debug("Entering, page->index = 0x%lx, cb_size = 0x%x, nr_pages = "
507 "%i.", index, cb_size, nr_pages);
508 /*
509 * Bad things happen if we get here for anything that is not an
510 * unnamed $DATA attribute.
511 */
512 BUG_ON(ni->type != AT_DATA);
513 BUG_ON(ni->name_len);
514
515 pages = kmalloc_array(nr_pages, sizeof(struct page *), GFP_NOFS);
516 completed_pages = kmalloc_array(nr_pages + 1, sizeof(int), GFP_NOFS);
517
518 /* Allocate memory to store the buffer heads we need. */
519 bhs_size = cb_size / block_size * sizeof(struct buffer_head *);
520 bhs = kmalloc(bhs_size, GFP_NOFS);
521
522 if (unlikely(!pages || !bhs || !completed_pages)) {
523 kfree(bhs);
524 kfree(pages);
525 kfree(completed_pages);
526 unlock_page(page);
527 ntfs_error(vol->sb, "Failed to allocate internal buffers.");
528 return -ENOMEM;
529 }
530
531 /*
532 * We have already been given one page, this is the one we must do.
533 * Once again, the alignment guarantees keep it simple.
534 */
535 offset = start_vcn << vol->cluster_size_bits >> PAGE_SHIFT;
536 xpage = index - offset;
537 pages[xpage] = page;
538 /*
539 * The remaining pages need to be allocated and inserted into the page
540 * cache, alignment guarantees keep all the below much simpler. (-8
541 */
542 read_lock_irqsave(&ni->size_lock, flags);
543 i_size = i_size_read(VFS_I(ni));
544 initialized_size = ni->initialized_size;
545 read_unlock_irqrestore(&ni->size_lock, flags);
546 max_page = ((i_size + PAGE_SIZE - 1) >> PAGE_SHIFT) -
547 offset;
548 /* Is the page fully outside i_size? (truncate in progress) */
549 if (xpage >= max_page) {
550 kfree(bhs);
551 kfree(pages);
552 kfree(completed_pages);
553 zero_user(page, 0, PAGE_SIZE);
554 ntfs_debug("Compressed read outside i_size - truncated?");
555 SetPageUptodate(page);
556 unlock_page(page);
557 return 0;
558 }
559 if (nr_pages < max_page)
560 max_page = nr_pages;
561 for (i = 0; i < max_page; i++, offset++) {
562 if (i != xpage)
563 pages[i] = grab_cache_page_nowait(mapping, offset);
564 page = pages[i];
565 if (page) {
566 /*
567 * We only (re)read the page if it isn't already read
568 * in and/or dirty or we would be losing data or at
569 * least wasting our time.
570 */
571 if (!PageDirty(page) && (!PageUptodate(page) ||
572 PageError(page))) {
573 ClearPageError(page);
574 kmap(page);
575 continue;
576 }
577 unlock_page(page);
578 put_page(page);
579 pages[i] = NULL;
580 }
581 }
582
583 /*
584 * We have the runlist, and all the destination pages we need to fill.
585 * Now read the first compression block.
586 */
587 cur_page = 0;
588 cur_ofs = 0;
589 cb_clusters = ni->itype.compressed.block_clusters;
590do_next_cb:
591 nr_cbs--;
592 nr_bhs = 0;
593
594 /* Read all cb buffer heads one cluster at a time. */
595 rl = NULL;
596 for (vcn = start_vcn, start_vcn += cb_clusters; vcn < start_vcn;
597 vcn++) {
598 bool is_retry = false;
599
600 if (!rl) {
601lock_retry_remap:
602 down_read(&ni->runlist.lock);
603 rl = ni->runlist.rl;
604 }
605 if (likely(rl != NULL)) {
606 /* Seek to element containing target vcn. */
607 while (rl->length && rl[1].vcn <= vcn)
608 rl++;
609 lcn = ntfs_rl_vcn_to_lcn(rl, vcn);
610 } else
611 lcn = LCN_RL_NOT_MAPPED;
612 ntfs_debug("Reading vcn = 0x%llx, lcn = 0x%llx.",
613 (unsigned long long)vcn,
614 (unsigned long long)lcn);
615 if (lcn < 0) {
616 /*
617 * When we reach the first sparse cluster we have
618 * finished with the cb.
619 */
620 if (lcn == LCN_HOLE)
621 break;
622 if (is_retry || lcn != LCN_RL_NOT_MAPPED)
623 goto rl_err;
624 is_retry = true;
625 /*
626 * Attempt to map runlist, dropping lock for the
627 * duration.
628 */
629 up_read(&ni->runlist.lock);
630 if (!ntfs_map_runlist(ni, vcn))
631 goto lock_retry_remap;
632 goto map_rl_err;
633 }
634 block = lcn << vol->cluster_size_bits >> block_size_bits;
635 /* Read the lcn from device in chunks of block_size bytes. */
636 max_block = block + (vol->cluster_size >> block_size_bits);
637 do {
638 ntfs_debug("block = 0x%x.", block);
639 if (unlikely(!(bhs[nr_bhs] = sb_getblk(sb, block))))
640 goto getblk_err;
641 nr_bhs++;
642 } while (++block < max_block);
643 }
644
645 /* Release the lock if we took it. */
646 if (rl)
647 up_read(&ni->runlist.lock);
648
649 /* Setup and initiate io on all buffer heads. */
650 for (i = 0; i < nr_bhs; i++) {
651 struct buffer_head *tbh = bhs[i];
652
653 if (!trylock_buffer(tbh))
654 continue;
655 if (unlikely(buffer_uptodate(tbh))) {
656 unlock_buffer(tbh);
657 continue;
658 }
659 get_bh(tbh);
660 tbh->b_end_io = end_buffer_read_sync;
661 submit_bh(REQ_OP_READ, tbh);
662 }
663
664 /* Wait for io completion on all buffer heads. */
665 for (i = 0; i < nr_bhs; i++) {
666 struct buffer_head *tbh = bhs[i];
667
668 if (buffer_uptodate(tbh))
669 continue;
670 wait_on_buffer(tbh);
671 /*
672 * We need an optimization barrier here, otherwise we start
673 * hitting the below fixup code when accessing a loopback
674 * mounted ntfs partition. This indicates either there is a
675 * race condition in the loop driver or, more likely, gcc
676 * overoptimises the code without the barrier and it doesn't
677 * do the Right Thing(TM).
678 */
679 barrier();
680 if (unlikely(!buffer_uptodate(tbh))) {
681 ntfs_warning(vol->sb, "Buffer is unlocked but not "
682 "uptodate! Unplugging the disk queue "
683 "and rescheduling.");
684 get_bh(tbh);
685 io_schedule();
686 put_bh(tbh);
687 if (unlikely(!buffer_uptodate(tbh)))
688 goto read_err;
689 ntfs_warning(vol->sb, "Buffer is now uptodate. Good.");
690 }
691 }
692
693 /*
694 * Get the compression buffer. We must not sleep any more
695 * until we are finished with it.
696 */
697 spin_lock(&ntfs_cb_lock);
698 cb = ntfs_compression_buffer;
699
700 BUG_ON(!cb);
701
702 cb_pos = cb;
703 cb_end = cb + cb_size;
704
705 /* Copy the buffer heads into the contiguous buffer. */
706 for (i = 0; i < nr_bhs; i++) {
707 memcpy(cb_pos, bhs[i]->b_data, block_size);
708 cb_pos += block_size;
709 }
710
711 /* Just a precaution. */
712 if (cb_pos + 2 <= cb + cb_size)
713 *(u16*)cb_pos = 0;
714
715 /* Reset cb_pos back to the beginning. */
716 cb_pos = cb;
717
718 /* We now have both source (if present) and destination. */
719 ntfs_debug("Successfully read the compression block.");
720
721 /* The last page and maximum offset within it for the current cb. */
722 cb_max_page = (cur_page << PAGE_SHIFT) + cur_ofs + cb_size;
723 cb_max_ofs = cb_max_page & ~PAGE_MASK;
724 cb_max_page >>= PAGE_SHIFT;
725
726 /* Catch end of file inside a compression block. */
727 if (cb_max_page > max_page)
728 cb_max_page = max_page;
729
730 if (vcn == start_vcn - cb_clusters) {
731 /* Sparse cb, zero out page range overlapping the cb. */
732 ntfs_debug("Found sparse compression block.");
733 /* We can sleep from now on, so we drop lock. */
734 spin_unlock(&ntfs_cb_lock);
735 if (cb_max_ofs)
736 cb_max_page--;
737 for (; cur_page < cb_max_page; cur_page++) {
738 page = pages[cur_page];
739 if (page) {
740 if (likely(!cur_ofs))
741 clear_page(page_address(page));
742 else
743 memset(page_address(page) + cur_ofs, 0,
744 PAGE_SIZE -
745 cur_ofs);
746 flush_dcache_page(page);
747 kunmap(page);
748 SetPageUptodate(page);
749 unlock_page(page);
750 if (cur_page == xpage)
751 xpage_done = 1;
752 else
753 put_page(page);
754 pages[cur_page] = NULL;
755 }
756 cb_pos += PAGE_SIZE - cur_ofs;
757 cur_ofs = 0;
758 if (cb_pos >= cb_end)
759 break;
760 }
761 /* If we have a partial final page, deal with it now. */
762 if (cb_max_ofs && cb_pos < cb_end) {
763 page = pages[cur_page];
764 if (page)
765 memset(page_address(page) + cur_ofs, 0,
766 cb_max_ofs - cur_ofs);
767 /*
768 * No need to update cb_pos at this stage:
769 * cb_pos += cb_max_ofs - cur_ofs;
770 */
771 cur_ofs = cb_max_ofs;
772 }
773 } else if (vcn == start_vcn) {
774 /* We can't sleep so we need two stages. */
775 unsigned int cur2_page = cur_page;
776 unsigned int cur_ofs2 = cur_ofs;
777 u8 *cb_pos2 = cb_pos;
778
779 ntfs_debug("Found uncompressed compression block.");
780 /* Uncompressed cb, copy it to the destination pages. */
781 /*
782 * TODO: As a big optimization, we could detect this case
783 * before we read all the pages and use block_read_full_folio()
784 * on all full pages instead (we still have to treat partial
785 * pages especially but at least we are getting rid of the
786 * synchronous io for the majority of pages.
787 * Or if we choose not to do the read-ahead/-behind stuff, we
788 * could just return block_read_full_folio(pages[xpage]) as long
789 * as PAGE_SIZE <= cb_size.
790 */
791 if (cb_max_ofs)
792 cb_max_page--;
793 /* First stage: copy data into destination pages. */
794 for (; cur_page < cb_max_page; cur_page++) {
795 page = pages[cur_page];
796 if (page)
797 memcpy(page_address(page) + cur_ofs, cb_pos,
798 PAGE_SIZE - cur_ofs);
799 cb_pos += PAGE_SIZE - cur_ofs;
800 cur_ofs = 0;
801 if (cb_pos >= cb_end)
802 break;
803 }
804 /* If we have a partial final page, deal with it now. */
805 if (cb_max_ofs && cb_pos < cb_end) {
806 page = pages[cur_page];
807 if (page)
808 memcpy(page_address(page) + cur_ofs, cb_pos,
809 cb_max_ofs - cur_ofs);
810 cb_pos += cb_max_ofs - cur_ofs;
811 cur_ofs = cb_max_ofs;
812 }
813 /* We can sleep from now on, so drop lock. */
814 spin_unlock(&ntfs_cb_lock);
815 /* Second stage: finalize pages. */
816 for (; cur2_page < cb_max_page; cur2_page++) {
817 page = pages[cur2_page];
818 if (page) {
819 /*
820 * If we are outside the initialized size, zero
821 * the out of bounds page range.
822 */
823 handle_bounds_compressed_page(page, i_size,
824 initialized_size);
825 flush_dcache_page(page);
826 kunmap(page);
827 SetPageUptodate(page);
828 unlock_page(page);
829 if (cur2_page == xpage)
830 xpage_done = 1;
831 else
832 put_page(page);
833 pages[cur2_page] = NULL;
834 }
835 cb_pos2 += PAGE_SIZE - cur_ofs2;
836 cur_ofs2 = 0;
837 if (cb_pos2 >= cb_end)
838 break;
839 }
840 } else {
841 /* Compressed cb, decompress it into the destination page(s). */
842 unsigned int prev_cur_page = cur_page;
843
844 ntfs_debug("Found compressed compression block.");
845 err = ntfs_decompress(pages, completed_pages, &cur_page,
846 &cur_ofs, cb_max_page, cb_max_ofs, xpage,
847 &xpage_done, cb_pos, cb_size - (cb_pos - cb),
848 i_size, initialized_size);
849 /*
850 * We can sleep from now on, lock already dropped by
851 * ntfs_decompress().
852 */
853 if (err) {
854 ntfs_error(vol->sb, "ntfs_decompress() failed in inode "
855 "0x%lx with error code %i. Skipping "
856 "this compression block.",
857 ni->mft_no, -err);
858 /* Release the unfinished pages. */
859 for (; prev_cur_page < cur_page; prev_cur_page++) {
860 page = pages[prev_cur_page];
861 if (page) {
862 flush_dcache_page(page);
863 kunmap(page);
864 unlock_page(page);
865 if (prev_cur_page != xpage)
866 put_page(page);
867 pages[prev_cur_page] = NULL;
868 }
869 }
870 }
871 }
872
873 /* Release the buffer heads. */
874 for (i = 0; i < nr_bhs; i++)
875 brelse(bhs[i]);
876
877 /* Do we have more work to do? */
878 if (nr_cbs)
879 goto do_next_cb;
880
881 /* We no longer need the list of buffer heads. */
882 kfree(bhs);
883
884 /* Clean up if we have any pages left. Should never happen. */
885 for (cur_page = 0; cur_page < max_page; cur_page++) {
886 page = pages[cur_page];
887 if (page) {
888 ntfs_error(vol->sb, "Still have pages left! "
889 "Terminating them with extreme "
890 "prejudice. Inode 0x%lx, page index "
891 "0x%lx.", ni->mft_no, page->index);
892 flush_dcache_page(page);
893 kunmap(page);
894 unlock_page(page);
895 if (cur_page != xpage)
896 put_page(page);
897 pages[cur_page] = NULL;
898 }
899 }
900
901 /* We no longer need the list of pages. */
902 kfree(pages);
903 kfree(completed_pages);
904
905 /* If we have completed the requested page, we return success. */
906 if (likely(xpage_done))
907 return 0;
908
909 ntfs_debug("Failed. Returning error code %s.", err == -EOVERFLOW ?
910 "EOVERFLOW" : (!err ? "EIO" : "unknown error"));
911 return err < 0 ? err : -EIO;
912
913read_err:
914 ntfs_error(vol->sb, "IO error while reading compressed data.");
915 /* Release the buffer heads. */
916 for (i = 0; i < nr_bhs; i++)
917 brelse(bhs[i]);
918 goto err_out;
919
920map_rl_err:
921 ntfs_error(vol->sb, "ntfs_map_runlist() failed. Cannot read "
922 "compression block.");
923 goto err_out;
924
925rl_err:
926 up_read(&ni->runlist.lock);
927 ntfs_error(vol->sb, "ntfs_rl_vcn_to_lcn() failed. Cannot read "
928 "compression block.");
929 goto err_out;
930
931getblk_err:
932 up_read(&ni->runlist.lock);
933 ntfs_error(vol->sb, "getblk() failed. Cannot read compression block.");
934
935err_out:
936 kfree(bhs);
937 for (i = cur_page; i < max_page; i++) {
938 page = pages[i];
939 if (page) {
940 flush_dcache_page(page);
941 kunmap(page);
942 unlock_page(page);
943 if (i != xpage)
944 put_page(page);
945 }
946 }
947 kfree(pages);
948 kfree(completed_pages);
949 return -EIO;
950}