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Linux/fs/btrfs/compression.c

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  1 /*
  2  * Copyright (C) 2008 Oracle.  All rights reserved.
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public
  6  * License v2 as published by the Free Software Foundation.
  7  *
  8  * This program is distributed in the hope that it will be useful,
  9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 11  * General Public License for more details.
 12  *
 13  * You should have received a copy of the GNU General Public
 14  * License along with this program; if not, write to the
 15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 16  * Boston, MA 021110-1307, USA.
 17  */
 18 
 19 #include <linux/kernel.h>
 20 #include <linux/bio.h>
 21 #include <linux/buffer_head.h>
 22 #include <linux/file.h>
 23 #include <linux/fs.h>
 24 #include <linux/pagemap.h>
 25 #include <linux/highmem.h>
 26 #include <linux/time.h>
 27 #include <linux/init.h>
 28 #include <linux/string.h>
 29 #include <linux/backing-dev.h>
 30 #include <linux/mpage.h>
 31 #include <linux/swap.h>
 32 #include <linux/writeback.h>
 33 #include <linux/bit_spinlock.h>
 34 #include <linux/slab.h>
 35 #include "ctree.h"
 36 #include "disk-io.h"
 37 #include "transaction.h"
 38 #include "btrfs_inode.h"
 39 #include "volumes.h"
 40 #include "ordered-data.h"
 41 #include "compression.h"
 42 #include "extent_io.h"
 43 #include "extent_map.h"
 44 
 45 struct compressed_bio {
 46         /* number of bios pending for this compressed extent */
 47         atomic_t pending_bios;
 48 
 49         /* the pages with the compressed data on them */
 50         struct page **compressed_pages;
 51 
 52         /* inode that owns this data */
 53         struct inode *inode;
 54 
 55         /* starting offset in the inode for our pages */
 56         u64 start;
 57 
 58         /* number of bytes in the inode we're working on */
 59         unsigned long len;
 60 
 61         /* number of bytes on disk */
 62         unsigned long compressed_len;
 63 
 64         /* the compression algorithm for this bio */
 65         int compress_type;
 66 
 67         /* number of compressed pages in the array */
 68         unsigned long nr_pages;
 69 
 70         /* IO errors */
 71         int errors;
 72         int mirror_num;
 73 
 74         /* for reads, this is the bio we are copying the data into */
 75         struct bio *orig_bio;
 76 
 77         /*
 78          * the start of a variable length array of checksums only
 79          * used by reads
 80          */
 81         u32 sums;
 82 };
 83 
 84 static int btrfs_decompress_biovec(int type, struct page **pages_in,
 85                                    u64 disk_start, struct bio_vec *bvec,
 86                                    int vcnt, size_t srclen);
 87 
 88 static inline int compressed_bio_size(struct btrfs_root *root,
 89                                       unsigned long disk_size)
 90 {
 91         u16 csum_size = btrfs_super_csum_size(root->fs_info->super_copy);
 92 
 93         return sizeof(struct compressed_bio) +
 94                 (DIV_ROUND_UP(disk_size, root->sectorsize)) * csum_size;
 95 }
 96 
 97 static struct bio *compressed_bio_alloc(struct block_device *bdev,
 98                                         u64 first_byte, gfp_t gfp_flags)
 99 {
100         int nr_vecs;
101 
102         nr_vecs = bio_get_nr_vecs(bdev);
103         return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
104 }
105 
106 static int check_compressed_csum(struct inode *inode,
107                                  struct compressed_bio *cb,
108                                  u64 disk_start)
109 {
110         int ret;
111         struct page *page;
112         unsigned long i;
113         char *kaddr;
114         u32 csum;
115         u32 *cb_sum = &cb->sums;
116 
117         if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
118                 return 0;
119 
120         for (i = 0; i < cb->nr_pages; i++) {
121                 page = cb->compressed_pages[i];
122                 csum = ~(u32)0;
123 
124                 kaddr = kmap_atomic(page);
125                 csum = btrfs_csum_data(kaddr, csum, PAGE_CACHE_SIZE);
126                 btrfs_csum_final(csum, (char *)&csum);
127                 kunmap_atomic(kaddr);
128 
129                 if (csum != *cb_sum) {
130                         btrfs_info(BTRFS_I(inode)->root->fs_info,
131                            "csum failed ino %llu extent %llu csum %u wanted %u mirror %d",
132                            btrfs_ino(inode), disk_start, csum, *cb_sum,
133                            cb->mirror_num);
134                         ret = -EIO;
135                         goto fail;
136                 }
137                 cb_sum++;
138 
139         }
140         ret = 0;
141 fail:
142         return ret;
143 }
144 
145 /* when we finish reading compressed pages from the disk, we
146  * decompress them and then run the bio end_io routines on the
147  * decompressed pages (in the inode address space).
148  *
149  * This allows the checksumming and other IO error handling routines
150  * to work normally
151  *
152  * The compressed pages are freed here, and it must be run
153  * in process context
154  */
155 static void end_compressed_bio_read(struct bio *bio, int err)
156 {
157         struct compressed_bio *cb = bio->bi_private;
158         struct inode *inode;
159         struct page *page;
160         unsigned long index;
161         int ret;
162 
163         if (err)
164                 cb->errors = 1;
165 
166         /* if there are more bios still pending for this compressed
167          * extent, just exit
168          */
169         if (!atomic_dec_and_test(&cb->pending_bios))
170                 goto out;
171 
172         inode = cb->inode;
173         ret = check_compressed_csum(inode, cb,
174                                     (u64)bio->bi_iter.bi_sector << 9);
175         if (ret)
176                 goto csum_failed;
177 
178         /* ok, we're the last bio for this extent, lets start
179          * the decompression.
180          */
181         ret = btrfs_decompress_biovec(cb->compress_type,
182                                       cb->compressed_pages,
183                                       cb->start,
184                                       cb->orig_bio->bi_io_vec,
185                                       cb->orig_bio->bi_vcnt,
186                                       cb->compressed_len);
187 csum_failed:
188         if (ret)
189                 cb->errors = 1;
190 
191         /* release the compressed pages */
192         index = 0;
193         for (index = 0; index < cb->nr_pages; index++) {
194                 page = cb->compressed_pages[index];
195                 page->mapping = NULL;
196                 page_cache_release(page);
197         }
198 
199         /* do io completion on the original bio */
200         if (cb->errors) {
201                 bio_io_error(cb->orig_bio);
202         } else {
203                 int i;
204                 struct bio_vec *bvec;
205 
206                 /*
207                  * we have verified the checksum already, set page
208                  * checked so the end_io handlers know about it
209                  */
210                 bio_for_each_segment_all(bvec, cb->orig_bio, i)
211                         SetPageChecked(bvec->bv_page);
212 
213                 bio_endio(cb->orig_bio, 0);
214         }
215 
216         /* finally free the cb struct */
217         kfree(cb->compressed_pages);
218         kfree(cb);
219 out:
220         bio_put(bio);
221 }
222 
223 /*
224  * Clear the writeback bits on all of the file
225  * pages for a compressed write
226  */
227 static noinline void end_compressed_writeback(struct inode *inode,
228                                               const struct compressed_bio *cb)
229 {
230         unsigned long index = cb->start >> PAGE_CACHE_SHIFT;
231         unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_CACHE_SHIFT;
232         struct page *pages[16];
233         unsigned long nr_pages = end_index - index + 1;
234         int i;
235         int ret;
236 
237         if (cb->errors)
238                 mapping_set_error(inode->i_mapping, -EIO);
239 
240         while (nr_pages > 0) {
241                 ret = find_get_pages_contig(inode->i_mapping, index,
242                                      min_t(unsigned long,
243                                      nr_pages, ARRAY_SIZE(pages)), pages);
244                 if (ret == 0) {
245                         nr_pages -= 1;
246                         index += 1;
247                         continue;
248                 }
249                 for (i = 0; i < ret; i++) {
250                         if (cb->errors)
251                                 SetPageError(pages[i]);
252                         end_page_writeback(pages[i]);
253                         page_cache_release(pages[i]);
254                 }
255                 nr_pages -= ret;
256                 index += ret;
257         }
258         /* the inode may be gone now */
259 }
260 
261 /*
262  * do the cleanup once all the compressed pages hit the disk.
263  * This will clear writeback on the file pages and free the compressed
264  * pages.
265  *
266  * This also calls the writeback end hooks for the file pages so that
267  * metadata and checksums can be updated in the file.
268  */
269 static void end_compressed_bio_write(struct bio *bio, int err)
270 {
271         struct extent_io_tree *tree;
272         struct compressed_bio *cb = bio->bi_private;
273         struct inode *inode;
274         struct page *page;
275         unsigned long index;
276 
277         if (err)
278                 cb->errors = 1;
279 
280         /* if there are more bios still pending for this compressed
281          * extent, just exit
282          */
283         if (!atomic_dec_and_test(&cb->pending_bios))
284                 goto out;
285 
286         /* ok, we're the last bio for this extent, step one is to
287          * call back into the FS and do all the end_io operations
288          */
289         inode = cb->inode;
290         tree = &BTRFS_I(inode)->io_tree;
291         cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
292         tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
293                                          cb->start,
294                                          cb->start + cb->len - 1,
295                                          NULL,
296                                          err ? 0 : 1);
297         cb->compressed_pages[0]->mapping = NULL;
298 
299         end_compressed_writeback(inode, cb);
300         /* note, our inode could be gone now */
301 
302         /*
303          * release the compressed pages, these came from alloc_page and
304          * are not attached to the inode at all
305          */
306         index = 0;
307         for (index = 0; index < cb->nr_pages; index++) {
308                 page = cb->compressed_pages[index];
309                 page->mapping = NULL;
310                 page_cache_release(page);
311         }
312 
313         /* finally free the cb struct */
314         kfree(cb->compressed_pages);
315         kfree(cb);
316 out:
317         bio_put(bio);
318 }
319 
320 /*
321  * worker function to build and submit bios for previously compressed pages.
322  * The corresponding pages in the inode should be marked for writeback
323  * and the compressed pages should have a reference on them for dropping
324  * when the IO is complete.
325  *
326  * This also checksums the file bytes and gets things ready for
327  * the end io hooks.
328  */
329 int btrfs_submit_compressed_write(struct inode *inode, u64 start,
330                                  unsigned long len, u64 disk_start,
331                                  unsigned long compressed_len,
332                                  struct page **compressed_pages,
333                                  unsigned long nr_pages)
334 {
335         struct bio *bio = NULL;
336         struct btrfs_root *root = BTRFS_I(inode)->root;
337         struct compressed_bio *cb;
338         unsigned long bytes_left;
339         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
340         int pg_index = 0;
341         struct page *page;
342         u64 first_byte = disk_start;
343         struct block_device *bdev;
344         int ret;
345         int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
346 
347         WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
348         cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
349         if (!cb)
350                 return -ENOMEM;
351         atomic_set(&cb->pending_bios, 0);
352         cb->errors = 0;
353         cb->inode = inode;
354         cb->start = start;
355         cb->len = len;
356         cb->mirror_num = 0;
357         cb->compressed_pages = compressed_pages;
358         cb->compressed_len = compressed_len;
359         cb->orig_bio = NULL;
360         cb->nr_pages = nr_pages;
361 
362         bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
363 
364         bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
365         if (!bio) {
366                 kfree(cb);
367                 return -ENOMEM;
368         }
369         bio->bi_private = cb;
370         bio->bi_end_io = end_compressed_bio_write;
371         atomic_inc(&cb->pending_bios);
372 
373         /* create and submit bios for the compressed pages */
374         bytes_left = compressed_len;
375         for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
376                 page = compressed_pages[pg_index];
377                 page->mapping = inode->i_mapping;
378                 if (bio->bi_iter.bi_size)
379                         ret = io_tree->ops->merge_bio_hook(WRITE, page, 0,
380                                                            PAGE_CACHE_SIZE,
381                                                            bio, 0);
382                 else
383                         ret = 0;
384 
385                 page->mapping = NULL;
386                 if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
387                     PAGE_CACHE_SIZE) {
388                         bio_get(bio);
389 
390                         /*
391                          * inc the count before we submit the bio so
392                          * we know the end IO handler won't happen before
393                          * we inc the count.  Otherwise, the cb might get
394                          * freed before we're done setting it up
395                          */
396                         atomic_inc(&cb->pending_bios);
397                         ret = btrfs_bio_wq_end_io(root->fs_info, bio,
398                                         BTRFS_WQ_ENDIO_DATA);
399                         BUG_ON(ret); /* -ENOMEM */
400 
401                         if (!skip_sum) {
402                                 ret = btrfs_csum_one_bio(root, inode, bio,
403                                                          start, 1);
404                                 BUG_ON(ret); /* -ENOMEM */
405                         }
406 
407                         ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
408                         BUG_ON(ret); /* -ENOMEM */
409 
410                         bio_put(bio);
411 
412                         bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
413                         BUG_ON(!bio);
414                         bio->bi_private = cb;
415                         bio->bi_end_io = end_compressed_bio_write;
416                         bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
417                 }
418                 if (bytes_left < PAGE_CACHE_SIZE) {
419                         btrfs_info(BTRFS_I(inode)->root->fs_info,
420                                         "bytes left %lu compress len %lu nr %lu",
421                                bytes_left, cb->compressed_len, cb->nr_pages);
422                 }
423                 bytes_left -= PAGE_CACHE_SIZE;
424                 first_byte += PAGE_CACHE_SIZE;
425                 cond_resched();
426         }
427         bio_get(bio);
428 
429         ret = btrfs_bio_wq_end_io(root->fs_info, bio, BTRFS_WQ_ENDIO_DATA);
430         BUG_ON(ret); /* -ENOMEM */
431 
432         if (!skip_sum) {
433                 ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
434                 BUG_ON(ret); /* -ENOMEM */
435         }
436 
437         ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
438         BUG_ON(ret); /* -ENOMEM */
439 
440         bio_put(bio);
441         return 0;
442 }
443 
444 static noinline int add_ra_bio_pages(struct inode *inode,
445                                      u64 compressed_end,
446                                      struct compressed_bio *cb)
447 {
448         unsigned long end_index;
449         unsigned long pg_index;
450         u64 last_offset;
451         u64 isize = i_size_read(inode);
452         int ret;
453         struct page *page;
454         unsigned long nr_pages = 0;
455         struct extent_map *em;
456         struct address_space *mapping = inode->i_mapping;
457         struct extent_map_tree *em_tree;
458         struct extent_io_tree *tree;
459         u64 end;
460         int misses = 0;
461 
462         page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
463         last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
464         em_tree = &BTRFS_I(inode)->extent_tree;
465         tree = &BTRFS_I(inode)->io_tree;
466 
467         if (isize == 0)
468                 return 0;
469 
470         end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
471 
472         while (last_offset < compressed_end) {
473                 pg_index = last_offset >> PAGE_CACHE_SHIFT;
474 
475                 if (pg_index > end_index)
476                         break;
477 
478                 rcu_read_lock();
479                 page = radix_tree_lookup(&mapping->page_tree, pg_index);
480                 rcu_read_unlock();
481                 if (page && !radix_tree_exceptional_entry(page)) {
482                         misses++;
483                         if (misses > 4)
484                                 break;
485                         goto next;
486                 }
487 
488                 page = __page_cache_alloc(mapping_gfp_mask(mapping) &
489                                                                 ~__GFP_FS);
490                 if (!page)
491                         break;
492 
493                 if (add_to_page_cache_lru(page, mapping, pg_index,
494                                                                 GFP_NOFS)) {
495                         page_cache_release(page);
496                         goto next;
497                 }
498 
499                 end = last_offset + PAGE_CACHE_SIZE - 1;
500                 /*
501                  * at this point, we have a locked page in the page cache
502                  * for these bytes in the file.  But, we have to make
503                  * sure they map to this compressed extent on disk.
504                  */
505                 set_page_extent_mapped(page);
506                 lock_extent(tree, last_offset, end);
507                 read_lock(&em_tree->lock);
508                 em = lookup_extent_mapping(em_tree, last_offset,
509                                            PAGE_CACHE_SIZE);
510                 read_unlock(&em_tree->lock);
511 
512                 if (!em || last_offset < em->start ||
513                     (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
514                     (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
515                         free_extent_map(em);
516                         unlock_extent(tree, last_offset, end);
517                         unlock_page(page);
518                         page_cache_release(page);
519                         break;
520                 }
521                 free_extent_map(em);
522 
523                 if (page->index == end_index) {
524                         char *userpage;
525                         size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
526 
527                         if (zero_offset) {
528                                 int zeros;
529                                 zeros = PAGE_CACHE_SIZE - zero_offset;
530                                 userpage = kmap_atomic(page);
531                                 memset(userpage + zero_offset, 0, zeros);
532                                 flush_dcache_page(page);
533                                 kunmap_atomic(userpage);
534                         }
535                 }
536 
537                 ret = bio_add_page(cb->orig_bio, page,
538                                    PAGE_CACHE_SIZE, 0);
539 
540                 if (ret == PAGE_CACHE_SIZE) {
541                         nr_pages++;
542                         page_cache_release(page);
543                 } else {
544                         unlock_extent(tree, last_offset, end);
545                         unlock_page(page);
546                         page_cache_release(page);
547                         break;
548                 }
549 next:
550                 last_offset += PAGE_CACHE_SIZE;
551         }
552         return 0;
553 }
554 
555 /*
556  * for a compressed read, the bio we get passed has all the inode pages
557  * in it.  We don't actually do IO on those pages but allocate new ones
558  * to hold the compressed pages on disk.
559  *
560  * bio->bi_iter.bi_sector points to the compressed extent on disk
561  * bio->bi_io_vec points to all of the inode pages
562  * bio->bi_vcnt is a count of pages
563  *
564  * After the compressed pages are read, we copy the bytes into the
565  * bio we were passed and then call the bio end_io calls
566  */
567 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
568                                  int mirror_num, unsigned long bio_flags)
569 {
570         struct extent_io_tree *tree;
571         struct extent_map_tree *em_tree;
572         struct compressed_bio *cb;
573         struct btrfs_root *root = BTRFS_I(inode)->root;
574         unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
575         unsigned long compressed_len;
576         unsigned long nr_pages;
577         unsigned long pg_index;
578         struct page *page;
579         struct block_device *bdev;
580         struct bio *comp_bio;
581         u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
582         u64 em_len;
583         u64 em_start;
584         struct extent_map *em;
585         int ret = -ENOMEM;
586         int faili = 0;
587         u32 *sums;
588 
589         tree = &BTRFS_I(inode)->io_tree;
590         em_tree = &BTRFS_I(inode)->extent_tree;
591 
592         /* we need the actual starting offset of this extent in the file */
593         read_lock(&em_tree->lock);
594         em = lookup_extent_mapping(em_tree,
595                                    page_offset(bio->bi_io_vec->bv_page),
596                                    PAGE_CACHE_SIZE);
597         read_unlock(&em_tree->lock);
598         if (!em)
599                 return -EIO;
600 
601         compressed_len = em->block_len;
602         cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
603         if (!cb)
604                 goto out;
605 
606         atomic_set(&cb->pending_bios, 0);
607         cb->errors = 0;
608         cb->inode = inode;
609         cb->mirror_num = mirror_num;
610         sums = &cb->sums;
611 
612         cb->start = em->orig_start;
613         em_len = em->len;
614         em_start = em->start;
615 
616         free_extent_map(em);
617         em = NULL;
618 
619         cb->len = uncompressed_len;
620         cb->compressed_len = compressed_len;
621         cb->compress_type = extent_compress_type(bio_flags);
622         cb->orig_bio = bio;
623 
624         nr_pages = DIV_ROUND_UP(compressed_len, PAGE_CACHE_SIZE);
625         cb->compressed_pages = kzalloc(sizeof(struct page *) * nr_pages,
626                                        GFP_NOFS);
627         if (!cb->compressed_pages)
628                 goto fail1;
629 
630         bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
631 
632         for (pg_index = 0; pg_index < nr_pages; pg_index++) {
633                 cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
634                                                               __GFP_HIGHMEM);
635                 if (!cb->compressed_pages[pg_index]) {
636                         faili = pg_index - 1;
637                         ret = -ENOMEM;
638                         goto fail2;
639                 }
640         }
641         faili = nr_pages - 1;
642         cb->nr_pages = nr_pages;
643 
644         /* In the parent-locked case, we only locked the range we are
645          * interested in.  In all other cases, we can opportunistically
646          * cache decompressed data that goes beyond the requested range. */
647         if (!(bio_flags & EXTENT_BIO_PARENT_LOCKED))
648                 add_ra_bio_pages(inode, em_start + em_len, cb);
649 
650         /* include any pages we added in add_ra-bio_pages */
651         uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
652         cb->len = uncompressed_len;
653 
654         comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
655         if (!comp_bio)
656                 goto fail2;
657         comp_bio->bi_private = cb;
658         comp_bio->bi_end_io = end_compressed_bio_read;
659         atomic_inc(&cb->pending_bios);
660 
661         for (pg_index = 0; pg_index < nr_pages; pg_index++) {
662                 page = cb->compressed_pages[pg_index];
663                 page->mapping = inode->i_mapping;
664                 page->index = em_start >> PAGE_CACHE_SHIFT;
665 
666                 if (comp_bio->bi_iter.bi_size)
667                         ret = tree->ops->merge_bio_hook(READ, page, 0,
668                                                         PAGE_CACHE_SIZE,
669                                                         comp_bio, 0);
670                 else
671                         ret = 0;
672 
673                 page->mapping = NULL;
674                 if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
675                     PAGE_CACHE_SIZE) {
676                         bio_get(comp_bio);
677 
678                         ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
679                                         BTRFS_WQ_ENDIO_DATA);
680                         BUG_ON(ret); /* -ENOMEM */
681 
682                         /*
683                          * inc the count before we submit the bio so
684                          * we know the end IO handler won't happen before
685                          * we inc the count.  Otherwise, the cb might get
686                          * freed before we're done setting it up
687                          */
688                         atomic_inc(&cb->pending_bios);
689 
690                         if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
691                                 ret = btrfs_lookup_bio_sums(root, inode,
692                                                         comp_bio, sums);
693                                 BUG_ON(ret); /* -ENOMEM */
694                         }
695                         sums += DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
696                                              root->sectorsize);
697 
698                         ret = btrfs_map_bio(root, READ, comp_bio,
699                                             mirror_num, 0);
700                         if (ret)
701                                 bio_endio(comp_bio, ret);
702 
703                         bio_put(comp_bio);
704 
705                         comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
706                                                         GFP_NOFS);
707                         BUG_ON(!comp_bio);
708                         comp_bio->bi_private = cb;
709                         comp_bio->bi_end_io = end_compressed_bio_read;
710 
711                         bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
712                 }
713                 cur_disk_byte += PAGE_CACHE_SIZE;
714         }
715         bio_get(comp_bio);
716 
717         ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio,
718                         BTRFS_WQ_ENDIO_DATA);
719         BUG_ON(ret); /* -ENOMEM */
720 
721         if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
722                 ret = btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
723                 BUG_ON(ret); /* -ENOMEM */
724         }
725 
726         ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
727         if (ret)
728                 bio_endio(comp_bio, ret);
729 
730         bio_put(comp_bio);
731         return 0;
732 
733 fail2:
734         while (faili >= 0) {
735                 __free_page(cb->compressed_pages[faili]);
736                 faili--;
737         }
738 
739         kfree(cb->compressed_pages);
740 fail1:
741         kfree(cb);
742 out:
743         free_extent_map(em);
744         return ret;
745 }
746 
747 static struct list_head comp_idle_workspace[BTRFS_COMPRESS_TYPES];
748 static spinlock_t comp_workspace_lock[BTRFS_COMPRESS_TYPES];
749 static int comp_num_workspace[BTRFS_COMPRESS_TYPES];
750 static atomic_t comp_alloc_workspace[BTRFS_COMPRESS_TYPES];
751 static wait_queue_head_t comp_workspace_wait[BTRFS_COMPRESS_TYPES];
752 
753 static struct btrfs_compress_op *btrfs_compress_op[] = {
754         &btrfs_zlib_compress,
755         &btrfs_lzo_compress,
756 };
757 
758 void __init btrfs_init_compress(void)
759 {
760         int i;
761 
762         for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
763                 INIT_LIST_HEAD(&comp_idle_workspace[i]);
764                 spin_lock_init(&comp_workspace_lock[i]);
765                 atomic_set(&comp_alloc_workspace[i], 0);
766                 init_waitqueue_head(&comp_workspace_wait[i]);
767         }
768 }
769 
770 /*
771  * this finds an available workspace or allocates a new one
772  * ERR_PTR is returned if things go bad.
773  */
774 static struct list_head *find_workspace(int type)
775 {
776         struct list_head *workspace;
777         int cpus = num_online_cpus();
778         int idx = type - 1;
779 
780         struct list_head *idle_workspace        = &comp_idle_workspace[idx];
781         spinlock_t *workspace_lock              = &comp_workspace_lock[idx];
782         atomic_t *alloc_workspace               = &comp_alloc_workspace[idx];
783         wait_queue_head_t *workspace_wait       = &comp_workspace_wait[idx];
784         int *num_workspace                      = &comp_num_workspace[idx];
785 again:
786         spin_lock(workspace_lock);
787         if (!list_empty(idle_workspace)) {
788                 workspace = idle_workspace->next;
789                 list_del(workspace);
790                 (*num_workspace)--;
791                 spin_unlock(workspace_lock);
792                 return workspace;
793 
794         }
795         if (atomic_read(alloc_workspace) > cpus) {
796                 DEFINE_WAIT(wait);
797 
798                 spin_unlock(workspace_lock);
799                 prepare_to_wait(workspace_wait, &wait, TASK_UNINTERRUPTIBLE);
800                 if (atomic_read(alloc_workspace) > cpus && !*num_workspace)
801                         schedule();
802                 finish_wait(workspace_wait, &wait);
803                 goto again;
804         }
805         atomic_inc(alloc_workspace);
806         spin_unlock(workspace_lock);
807 
808         workspace = btrfs_compress_op[idx]->alloc_workspace();
809         if (IS_ERR(workspace)) {
810                 atomic_dec(alloc_workspace);
811                 wake_up(workspace_wait);
812         }
813         return workspace;
814 }
815 
816 /*
817  * put a workspace struct back on the list or free it if we have enough
818  * idle ones sitting around
819  */
820 static void free_workspace(int type, struct list_head *workspace)
821 {
822         int idx = type - 1;
823         struct list_head *idle_workspace        = &comp_idle_workspace[idx];
824         spinlock_t *workspace_lock              = &comp_workspace_lock[idx];
825         atomic_t *alloc_workspace               = &comp_alloc_workspace[idx];
826         wait_queue_head_t *workspace_wait       = &comp_workspace_wait[idx];
827         int *num_workspace                      = &comp_num_workspace[idx];
828 
829         spin_lock(workspace_lock);
830         if (*num_workspace < num_online_cpus()) {
831                 list_add(workspace, idle_workspace);
832                 (*num_workspace)++;
833                 spin_unlock(workspace_lock);
834                 goto wake;
835         }
836         spin_unlock(workspace_lock);
837 
838         btrfs_compress_op[idx]->free_workspace(workspace);
839         atomic_dec(alloc_workspace);
840 wake:
841         smp_mb();
842         if (waitqueue_active(workspace_wait))
843                 wake_up(workspace_wait);
844 }
845 
846 /*
847  * cleanup function for module exit
848  */
849 static void free_workspaces(void)
850 {
851         struct list_head *workspace;
852         int i;
853 
854         for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
855                 while (!list_empty(&comp_idle_workspace[i])) {
856                         workspace = comp_idle_workspace[i].next;
857                         list_del(workspace);
858                         btrfs_compress_op[i]->free_workspace(workspace);
859                         atomic_dec(&comp_alloc_workspace[i]);
860                 }
861         }
862 }
863 
864 /*
865  * given an address space and start/len, compress the bytes.
866  *
867  * pages are allocated to hold the compressed result and stored
868  * in 'pages'
869  *
870  * out_pages is used to return the number of pages allocated.  There
871  * may be pages allocated even if we return an error
872  *
873  * total_in is used to return the number of bytes actually read.  It
874  * may be smaller then len if we had to exit early because we
875  * ran out of room in the pages array or because we cross the
876  * max_out threshold.
877  *
878  * total_out is used to return the total number of compressed bytes
879  *
880  * max_out tells us the max number of bytes that we're allowed to
881  * stuff into pages
882  */
883 int btrfs_compress_pages(int type, struct address_space *mapping,
884                          u64 start, unsigned long len,
885                          struct page **pages,
886                          unsigned long nr_dest_pages,
887                          unsigned long *out_pages,
888                          unsigned long *total_in,
889                          unsigned long *total_out,
890                          unsigned long max_out)
891 {
892         struct list_head *workspace;
893         int ret;
894 
895         workspace = find_workspace(type);
896         if (IS_ERR(workspace))
897                 return PTR_ERR(workspace);
898 
899         ret = btrfs_compress_op[type-1]->compress_pages(workspace, mapping,
900                                                       start, len, pages,
901                                                       nr_dest_pages, out_pages,
902                                                       total_in, total_out,
903                                                       max_out);
904         free_workspace(type, workspace);
905         return ret;
906 }
907 
908 /*
909  * pages_in is an array of pages with compressed data.
910  *
911  * disk_start is the starting logical offset of this array in the file
912  *
913  * bvec is a bio_vec of pages from the file that we want to decompress into
914  *
915  * vcnt is the count of pages in the biovec
916  *
917  * srclen is the number of bytes in pages_in
918  *
919  * The basic idea is that we have a bio that was created by readpages.
920  * The pages in the bio are for the uncompressed data, and they may not
921  * be contiguous.  They all correspond to the range of bytes covered by
922  * the compressed extent.
923  */
924 static int btrfs_decompress_biovec(int type, struct page **pages_in,
925                                    u64 disk_start, struct bio_vec *bvec,
926                                    int vcnt, size_t srclen)
927 {
928         struct list_head *workspace;
929         int ret;
930 
931         workspace = find_workspace(type);
932         if (IS_ERR(workspace))
933                 return PTR_ERR(workspace);
934 
935         ret = btrfs_compress_op[type-1]->decompress_biovec(workspace, pages_in,
936                                                          disk_start,
937                                                          bvec, vcnt, srclen);
938         free_workspace(type, workspace);
939         return ret;
940 }
941 
942 /*
943  * a less complex decompression routine.  Our compressed data fits in a
944  * single page, and we want to read a single page out of it.
945  * start_byte tells us the offset into the compressed data we're interested in
946  */
947 int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
948                      unsigned long start_byte, size_t srclen, size_t destlen)
949 {
950         struct list_head *workspace;
951         int ret;
952 
953         workspace = find_workspace(type);
954         if (IS_ERR(workspace))
955                 return PTR_ERR(workspace);
956 
957         ret = btrfs_compress_op[type-1]->decompress(workspace, data_in,
958                                                   dest_page, start_byte,
959                                                   srclen, destlen);
960 
961         free_workspace(type, workspace);
962         return ret;
963 }
964 
965 void btrfs_exit_compress(void)
966 {
967         free_workspaces();
968 }
969 
970 /*
971  * Copy uncompressed data from working buffer to pages.
972  *
973  * buf_start is the byte offset we're of the start of our workspace buffer.
974  *
975  * total_out is the last byte of the buffer
976  */
977 int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
978                               unsigned long total_out, u64 disk_start,
979                               struct bio_vec *bvec, int vcnt,
980                               unsigned long *pg_index,
981                               unsigned long *pg_offset)
982 {
983         unsigned long buf_offset;
984         unsigned long current_buf_start;
985         unsigned long start_byte;
986         unsigned long working_bytes = total_out - buf_start;
987         unsigned long bytes;
988         char *kaddr;
989         struct page *page_out = bvec[*pg_index].bv_page;
990 
991         /*
992          * start byte is the first byte of the page we're currently
993          * copying into relative to the start of the compressed data.
994          */
995         start_byte = page_offset(page_out) - disk_start;
996 
997         /* we haven't yet hit data corresponding to this page */
998         if (total_out <= start_byte)
999                 return 1;
1000 
1001         /*
1002          * the start of the data we care about is offset into
1003          * the middle of our working buffer
1004          */
1005         if (total_out > start_byte && buf_start < start_byte) {
1006                 buf_offset = start_byte - buf_start;
1007                 working_bytes -= buf_offset;
1008         } else {
1009                 buf_offset = 0;
1010         }
1011         current_buf_start = buf_start;
1012 
1013         /* copy bytes from the working buffer into the pages */
1014         while (working_bytes > 0) {
1015                 bytes = min(PAGE_CACHE_SIZE - *pg_offset,
1016                             PAGE_CACHE_SIZE - buf_offset);
1017                 bytes = min(bytes, working_bytes);
1018                 kaddr = kmap_atomic(page_out);
1019                 memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
1020                 kunmap_atomic(kaddr);
1021                 flush_dcache_page(page_out);
1022 
1023                 *pg_offset += bytes;
1024                 buf_offset += bytes;
1025                 working_bytes -= bytes;
1026                 current_buf_start += bytes;
1027 
1028                 /* check if we need to pick another page */
1029                 if (*pg_offset == PAGE_CACHE_SIZE) {
1030                         (*pg_index)++;
1031                         if (*pg_index >= vcnt)
1032                                 return 0;
1033 
1034                         page_out = bvec[*pg_index].bv_page;
1035                         *pg_offset = 0;
1036                         start_byte = page_offset(page_out) - disk_start;
1037 
1038                         /*
1039                          * make sure our new page is covered by this
1040                          * working buffer
1041                          */
1042                         if (total_out <= start_byte)
1043                                 return 1;
1044 
1045                         /*
1046                          * the next page in the biovec might not be adjacent
1047                          * to the last page, but it might still be found
1048                          * inside this working buffer. bump our offset pointer
1049                          */
1050                         if (total_out > start_byte &&
1051                             current_buf_start < start_byte) {
1052                                 buf_offset = start_byte - buf_start;
1053                                 working_bytes = total_out - start_byte;
1054                                 current_buf_start = buf_start + buf_offset;
1055                         }
1056                 }
1057         }
1058 
1059         return 1;
1060 }
1061 
1062 /*
1063  * When uncompressing data, we need to make sure and zero any parts of
1064  * the biovec that were not filled in by the decompression code.  pg_index
1065  * and pg_offset indicate the last page and the last offset of that page
1066  * that have been filled in.  This will zero everything remaining in the
1067  * biovec.
1068  */
1069 void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
1070                                    unsigned long pg_index,
1071                                    unsigned long pg_offset)
1072 {
1073         while (pg_index < vcnt) {
1074                 struct page *page = bvec[pg_index].bv_page;
1075                 unsigned long off = bvec[pg_index].bv_offset;
1076                 unsigned long len = bvec[pg_index].bv_len;
1077 
1078                 if (pg_offset < off)
1079                         pg_offset = off;
1080                 if (pg_offset < off + len) {
1081                         unsigned long bytes = off + len - pg_offset;
1082                         char *kaddr;
1083 
1084                         kaddr = kmap_atomic(page);
1085                         memset(kaddr + pg_offset, 0, bytes);
1086                         kunmap_atomic(kaddr);
1087                 }
1088                 pg_index++;
1089                 pg_offset = 0;
1090         }
1091 }
1092 

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