Root/fs/btrfs/compression.c

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 "compat.h"
36#include "ctree.h"
37#include "disk-io.h"
38#include "transaction.h"
39#include "btrfs_inode.h"
40#include "volumes.h"
41#include "ordered-data.h"
42#include "compression.h"
43#include "extent_io.h"
44#include "extent_map.h"
45
46struct compressed_bio {
47    /* number of bios pending for this compressed extent */
48    atomic_t pending_bios;
49
50    /* the pages with the compressed data on them */
51    struct page **compressed_pages;
52
53    /* inode that owns this data */
54    struct inode *inode;
55
56    /* starting offset in the inode for our pages */
57    u64 start;
58
59    /* number of bytes in the inode we're working on */
60    unsigned long len;
61
62    /* number of bytes on disk */
63    unsigned long compressed_len;
64
65    /* number of compressed pages in the array */
66    unsigned long nr_pages;
67
68    /* IO errors */
69    int errors;
70    int mirror_num;
71
72    /* for reads, this is the bio we are copying the data into */
73    struct bio *orig_bio;
74
75    /*
76     * the start of a variable length array of checksums only
77     * used by reads
78     */
79    u32 sums;
80};
81
82static inline int compressed_bio_size(struct btrfs_root *root,
83                      unsigned long disk_size)
84{
85    u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
86    return sizeof(struct compressed_bio) +
87        ((disk_size + root->sectorsize - 1) / root->sectorsize) *
88        csum_size;
89}
90
91static struct bio *compressed_bio_alloc(struct block_device *bdev,
92                    u64 first_byte, gfp_t gfp_flags)
93{
94    struct bio *bio;
95    int nr_vecs;
96
97    nr_vecs = bio_get_nr_vecs(bdev);
98    bio = bio_alloc(gfp_flags, nr_vecs);
99
100    if (bio == NULL && (current->flags & PF_MEMALLOC)) {
101        while (!bio && (nr_vecs /= 2))
102            bio = bio_alloc(gfp_flags, nr_vecs);
103    }
104
105    if (bio) {
106        bio->bi_size = 0;
107        bio->bi_bdev = bdev;
108        bio->bi_sector = first_byte >> 9;
109    }
110    return bio;
111}
112
113static int check_compressed_csum(struct inode *inode,
114                 struct compressed_bio *cb,
115                 u64 disk_start)
116{
117    int ret;
118    struct btrfs_root *root = BTRFS_I(inode)->root;
119    struct page *page;
120    unsigned long i;
121    char *kaddr;
122    u32 csum;
123    u32 *cb_sum = &cb->sums;
124
125    if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
126        return 0;
127
128    for (i = 0; i < cb->nr_pages; i++) {
129        page = cb->compressed_pages[i];
130        csum = ~(u32)0;
131
132        kaddr = kmap_atomic(page, KM_USER0);
133        csum = btrfs_csum_data(root, kaddr, csum, PAGE_CACHE_SIZE);
134        btrfs_csum_final(csum, (char *)&csum);
135        kunmap_atomic(kaddr, KM_USER0);
136
137        if (csum != *cb_sum) {
138            printk(KERN_INFO "btrfs csum failed ino %lu "
139                   "extent %llu csum %u "
140                   "wanted %u mirror %d\n", inode->i_ino,
141                   (unsigned long long)disk_start,
142                   csum, *cb_sum, cb->mirror_num);
143            ret = -EIO;
144            goto fail;
145        }
146        cb_sum++;
147
148    }
149    ret = 0;
150fail:
151    return ret;
152}
153
154/* when we finish reading compressed pages from the disk, we
155 * decompress them and then run the bio end_io routines on the
156 * decompressed pages (in the inode address space).
157 *
158 * This allows the checksumming and other IO error handling routines
159 * to work normally
160 *
161 * The compressed pages are freed here, and it must be run
162 * in process context
163 */
164static void end_compressed_bio_read(struct bio *bio, int err)
165{
166    struct extent_io_tree *tree;
167    struct compressed_bio *cb = bio->bi_private;
168    struct inode *inode;
169    struct page *page;
170    unsigned long index;
171    int ret;
172
173    if (err)
174        cb->errors = 1;
175
176    /* if there are more bios still pending for this compressed
177     * extent, just exit
178     */
179    if (!atomic_dec_and_test(&cb->pending_bios))
180        goto out;
181
182    inode = cb->inode;
183    ret = check_compressed_csum(inode, cb, (u64)bio->bi_sector << 9);
184    if (ret)
185        goto csum_failed;
186
187    /* ok, we're the last bio for this extent, lets start
188     * the decompression.
189     */
190    tree = &BTRFS_I(inode)->io_tree;
191    ret = btrfs_zlib_decompress_biovec(cb->compressed_pages,
192                    cb->start,
193                    cb->orig_bio->bi_io_vec,
194                    cb->orig_bio->bi_vcnt,
195                    cb->compressed_len);
196csum_failed:
197    if (ret)
198        cb->errors = 1;
199
200    /* release the compressed pages */
201    index = 0;
202    for (index = 0; index < cb->nr_pages; index++) {
203        page = cb->compressed_pages[index];
204        page->mapping = NULL;
205        page_cache_release(page);
206    }
207
208    /* do io completion on the original bio */
209    if (cb->errors) {
210        bio_io_error(cb->orig_bio);
211    } else {
212        int bio_index = 0;
213        struct bio_vec *bvec = cb->orig_bio->bi_io_vec;
214
215        /*
216         * we have verified the checksum already, set page
217         * checked so the end_io handlers know about it
218         */
219        while (bio_index < cb->orig_bio->bi_vcnt) {
220            SetPageChecked(bvec->bv_page);
221            bvec++;
222            bio_index++;
223        }
224        bio_endio(cb->orig_bio, 0);
225    }
226
227    /* finally free the cb struct */
228    kfree(cb->compressed_pages);
229    kfree(cb);
230out:
231    bio_put(bio);
232}
233
234/*
235 * Clear the writeback bits on all of the file
236 * pages for a compressed write
237 */
238static noinline int end_compressed_writeback(struct inode *inode, u64 start,
239                         unsigned long ram_size)
240{
241    unsigned long index = start >> PAGE_CACHE_SHIFT;
242    unsigned long end_index = (start + ram_size - 1) >> PAGE_CACHE_SHIFT;
243    struct page *pages[16];
244    unsigned long nr_pages = end_index - index + 1;
245    int i;
246    int ret;
247
248    while (nr_pages > 0) {
249        ret = find_get_pages_contig(inode->i_mapping, index,
250                     min_t(unsigned long,
251                     nr_pages, ARRAY_SIZE(pages)), pages);
252        if (ret == 0) {
253            nr_pages -= 1;
254            index += 1;
255            continue;
256        }
257        for (i = 0; i < ret; i++) {
258            end_page_writeback(pages[i]);
259            page_cache_release(pages[i]);
260        }
261        nr_pages -= ret;
262        index += ret;
263    }
264    /* the inode may be gone now */
265    return 0;
266}
267
268/*
269 * do the cleanup once all the compressed pages hit the disk.
270 * This will clear writeback on the file pages and free the compressed
271 * pages.
272 *
273 * This also calls the writeback end hooks for the file pages so that
274 * metadata and checksums can be updated in the file.
275 */
276static void end_compressed_bio_write(struct bio *bio, int err)
277{
278    struct extent_io_tree *tree;
279    struct compressed_bio *cb = bio->bi_private;
280    struct inode *inode;
281    struct page *page;
282    unsigned long index;
283
284    if (err)
285        cb->errors = 1;
286
287    /* if there are more bios still pending for this compressed
288     * extent, just exit
289     */
290    if (!atomic_dec_and_test(&cb->pending_bios))
291        goto out;
292
293    /* ok, we're the last bio for this extent, step one is to
294     * call back into the FS and do all the end_io operations
295     */
296    inode = cb->inode;
297    tree = &BTRFS_I(inode)->io_tree;
298    cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
299    tree->ops->writepage_end_io_hook(cb->compressed_pages[0],
300                     cb->start,
301                     cb->start + cb->len - 1,
302                     NULL, 1);
303    cb->compressed_pages[0]->mapping = NULL;
304
305    end_compressed_writeback(inode, cb->start, cb->len);
306    /* note, our inode could be gone now */
307
308    /*
309     * release the compressed pages, these came from alloc_page and
310     * are not attached to the inode at all
311     */
312    index = 0;
313    for (index = 0; index < cb->nr_pages; index++) {
314        page = cb->compressed_pages[index];
315        page->mapping = NULL;
316        page_cache_release(page);
317    }
318
319    /* finally free the cb struct */
320    kfree(cb->compressed_pages);
321    kfree(cb);
322out:
323    bio_put(bio);
324}
325
326/*
327 * worker function to build and submit bios for previously compressed pages.
328 * The corresponding pages in the inode should be marked for writeback
329 * and the compressed pages should have a reference on them for dropping
330 * when the IO is complete.
331 *
332 * This also checksums the file bytes and gets things ready for
333 * the end io hooks.
334 */
335int btrfs_submit_compressed_write(struct inode *inode, u64 start,
336                 unsigned long len, u64 disk_start,
337                 unsigned long compressed_len,
338                 struct page **compressed_pages,
339                 unsigned long nr_pages)
340{
341    struct bio *bio = NULL;
342    struct btrfs_root *root = BTRFS_I(inode)->root;
343    struct compressed_bio *cb;
344    unsigned long bytes_left;
345    struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
346    int page_index = 0;
347    struct page *page;
348    u64 first_byte = disk_start;
349    struct block_device *bdev;
350    int ret;
351
352    WARN_ON(start & ((u64)PAGE_CACHE_SIZE - 1));
353    cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
354    atomic_set(&cb->pending_bios, 0);
355    cb->errors = 0;
356    cb->inode = inode;
357    cb->start = start;
358    cb->len = len;
359    cb->mirror_num = 0;
360    cb->compressed_pages = compressed_pages;
361    cb->compressed_len = compressed_len;
362    cb->orig_bio = NULL;
363    cb->nr_pages = nr_pages;
364
365    bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
366
367    bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
368    bio->bi_private = cb;
369    bio->bi_end_io = end_compressed_bio_write;
370    atomic_inc(&cb->pending_bios);
371
372    /* create and submit bios for the compressed pages */
373    bytes_left = compressed_len;
374    for (page_index = 0; page_index < cb->nr_pages; page_index++) {
375        page = compressed_pages[page_index];
376        page->mapping = inode->i_mapping;
377        if (bio->bi_size)
378            ret = io_tree->ops->merge_bio_hook(page, 0,
379                               PAGE_CACHE_SIZE,
380                               bio, 0);
381        else
382            ret = 0;
383
384        page->mapping = NULL;
385        if (ret || bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) <
386            PAGE_CACHE_SIZE) {
387            bio_get(bio);
388
389            /*
390             * inc the count before we submit the bio so
391             * we know the end IO handler won't happen before
392             * we inc the count. Otherwise, the cb might get
393             * freed before we're done setting it up
394             */
395            atomic_inc(&cb->pending_bios);
396            ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
397            BUG_ON(ret);
398
399            ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
400            BUG_ON(ret);
401
402            ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
403            BUG_ON(ret);
404
405            bio_put(bio);
406
407            bio = compressed_bio_alloc(bdev, first_byte, GFP_NOFS);
408            bio->bi_private = cb;
409            bio->bi_end_io = end_compressed_bio_write;
410            bio_add_page(bio, page, PAGE_CACHE_SIZE, 0);
411        }
412        if (bytes_left < PAGE_CACHE_SIZE) {
413            printk("bytes left %lu compress len %lu nr %lu\n",
414                   bytes_left, cb->compressed_len, cb->nr_pages);
415        }
416        bytes_left -= PAGE_CACHE_SIZE;
417        first_byte += PAGE_CACHE_SIZE;
418        cond_resched();
419    }
420    bio_get(bio);
421
422    ret = btrfs_bio_wq_end_io(root->fs_info, bio, 0);
423    BUG_ON(ret);
424
425    ret = btrfs_csum_one_bio(root, inode, bio, start, 1);
426    BUG_ON(ret);
427
428    ret = btrfs_map_bio(root, WRITE, bio, 0, 1);
429    BUG_ON(ret);
430
431    bio_put(bio);
432    return 0;
433}
434
435static noinline int add_ra_bio_pages(struct inode *inode,
436                     u64 compressed_end,
437                     struct compressed_bio *cb)
438{
439    unsigned long end_index;
440    unsigned long page_index;
441    u64 last_offset;
442    u64 isize = i_size_read(inode);
443    int ret;
444    struct page *page;
445    unsigned long nr_pages = 0;
446    struct extent_map *em;
447    struct address_space *mapping = inode->i_mapping;
448    struct extent_map_tree *em_tree;
449    struct extent_io_tree *tree;
450    u64 end;
451    int misses = 0;
452
453    page = cb->orig_bio->bi_io_vec[cb->orig_bio->bi_vcnt - 1].bv_page;
454    last_offset = (page_offset(page) + PAGE_CACHE_SIZE);
455    em_tree = &BTRFS_I(inode)->extent_tree;
456    tree = &BTRFS_I(inode)->io_tree;
457
458    if (isize == 0)
459        return 0;
460
461    end_index = (i_size_read(inode) - 1) >> PAGE_CACHE_SHIFT;
462
463    while (last_offset < compressed_end) {
464        page_index = last_offset >> PAGE_CACHE_SHIFT;
465
466        if (page_index > end_index)
467            break;
468
469        rcu_read_lock();
470        page = radix_tree_lookup(&mapping->page_tree, page_index);
471        rcu_read_unlock();
472        if (page) {
473            misses++;
474            if (misses > 4)
475                break;
476            goto next;
477        }
478
479        page = __page_cache_alloc(mapping_gfp_mask(mapping) &
480                                ~__GFP_FS);
481        if (!page)
482            break;
483
484        if (add_to_page_cache_lru(page, mapping, page_index,
485                                GFP_NOFS)) {
486            page_cache_release(page);
487            goto next;
488        }
489
490        end = last_offset + PAGE_CACHE_SIZE - 1;
491        /*
492         * at this point, we have a locked page in the page cache
493         * for these bytes in the file. But, we have to make
494         * sure they map to this compressed extent on disk.
495         */
496        set_page_extent_mapped(page);
497        lock_extent(tree, last_offset, end, GFP_NOFS);
498        read_lock(&em_tree->lock);
499        em = lookup_extent_mapping(em_tree, last_offset,
500                       PAGE_CACHE_SIZE);
501        read_unlock(&em_tree->lock);
502
503        if (!em || last_offset < em->start ||
504            (last_offset + PAGE_CACHE_SIZE > extent_map_end(em)) ||
505            (em->block_start >> 9) != cb->orig_bio->bi_sector) {
506            free_extent_map(em);
507            unlock_extent(tree, last_offset, end, GFP_NOFS);
508            unlock_page(page);
509            page_cache_release(page);
510            break;
511        }
512        free_extent_map(em);
513
514        if (page->index == end_index) {
515            char *userpage;
516            size_t zero_offset = isize & (PAGE_CACHE_SIZE - 1);
517
518            if (zero_offset) {
519                int zeros;
520                zeros = PAGE_CACHE_SIZE - zero_offset;
521                userpage = kmap_atomic(page, KM_USER0);
522                memset(userpage + zero_offset, 0, zeros);
523                flush_dcache_page(page);
524                kunmap_atomic(userpage, KM_USER0);
525            }
526        }
527
528        ret = bio_add_page(cb->orig_bio, page,
529                   PAGE_CACHE_SIZE, 0);
530
531        if (ret == PAGE_CACHE_SIZE) {
532            nr_pages++;
533            page_cache_release(page);
534        } else {
535            unlock_extent(tree, last_offset, end, GFP_NOFS);
536            unlock_page(page);
537            page_cache_release(page);
538            break;
539        }
540next:
541        last_offset += PAGE_CACHE_SIZE;
542    }
543    return 0;
544}
545
546/*
547 * for a compressed read, the bio we get passed has all the inode pages
548 * in it. We don't actually do IO on those pages but allocate new ones
549 * to hold the compressed pages on disk.
550 *
551 * bio->bi_sector points to the compressed extent on disk
552 * bio->bi_io_vec points to all of the inode pages
553 * bio->bi_vcnt is a count of pages
554 *
555 * After the compressed pages are read, we copy the bytes into the
556 * bio we were passed and then call the bio end_io calls
557 */
558int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
559                 int mirror_num, unsigned long bio_flags)
560{
561    struct extent_io_tree *tree;
562    struct extent_map_tree *em_tree;
563    struct compressed_bio *cb;
564    struct btrfs_root *root = BTRFS_I(inode)->root;
565    unsigned long uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
566    unsigned long compressed_len;
567    unsigned long nr_pages;
568    unsigned long page_index;
569    struct page *page;
570    struct block_device *bdev;
571    struct bio *comp_bio;
572    u64 cur_disk_byte = (u64)bio->bi_sector << 9;
573    u64 em_len;
574    u64 em_start;
575    struct extent_map *em;
576    int ret;
577    u32 *sums;
578
579    tree = &BTRFS_I(inode)->io_tree;
580    em_tree = &BTRFS_I(inode)->extent_tree;
581
582    /* we need the actual starting offset of this extent in the file */
583    read_lock(&em_tree->lock);
584    em = lookup_extent_mapping(em_tree,
585                   page_offset(bio->bi_io_vec->bv_page),
586                   PAGE_CACHE_SIZE);
587    read_unlock(&em_tree->lock);
588
589    compressed_len = em->block_len;
590    cb = kmalloc(compressed_bio_size(root, compressed_len), GFP_NOFS);
591    atomic_set(&cb->pending_bios, 0);
592    cb->errors = 0;
593    cb->inode = inode;
594    cb->mirror_num = mirror_num;
595    sums = &cb->sums;
596
597    cb->start = em->orig_start;
598    em_len = em->len;
599    em_start = em->start;
600
601    free_extent_map(em);
602    em = NULL;
603
604    cb->len = uncompressed_len;
605    cb->compressed_len = compressed_len;
606    cb->orig_bio = bio;
607
608    nr_pages = (compressed_len + PAGE_CACHE_SIZE - 1) /
609                 PAGE_CACHE_SIZE;
610    cb->compressed_pages = kmalloc(sizeof(struct page *) * nr_pages,
611                       GFP_NOFS);
612    bdev = BTRFS_I(inode)->root->fs_info->fs_devices->latest_bdev;
613
614    for (page_index = 0; page_index < nr_pages; page_index++) {
615        cb->compressed_pages[page_index] = alloc_page(GFP_NOFS |
616                                  __GFP_HIGHMEM);
617    }
618    cb->nr_pages = nr_pages;
619
620    add_ra_bio_pages(inode, em_start + em_len, cb);
621
622    /* include any pages we added in add_ra-bio_pages */
623    uncompressed_len = bio->bi_vcnt * PAGE_CACHE_SIZE;
624    cb->len = uncompressed_len;
625
626    comp_bio = compressed_bio_alloc(bdev, cur_disk_byte, GFP_NOFS);
627    comp_bio->bi_private = cb;
628    comp_bio->bi_end_io = end_compressed_bio_read;
629    atomic_inc(&cb->pending_bios);
630
631    for (page_index = 0; page_index < nr_pages; page_index++) {
632        page = cb->compressed_pages[page_index];
633        page->mapping = inode->i_mapping;
634        page->index = em_start >> PAGE_CACHE_SHIFT;
635
636        if (comp_bio->bi_size)
637            ret = tree->ops->merge_bio_hook(page, 0,
638                            PAGE_CACHE_SIZE,
639                            comp_bio, 0);
640        else
641            ret = 0;
642
643        page->mapping = NULL;
644        if (ret || bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0) <
645            PAGE_CACHE_SIZE) {
646            bio_get(comp_bio);
647
648            ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
649            BUG_ON(ret);
650
651            /*
652             * inc the count before we submit the bio so
653             * we know the end IO handler won't happen before
654             * we inc the count. Otherwise, the cb might get
655             * freed before we're done setting it up
656             */
657            atomic_inc(&cb->pending_bios);
658
659            if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
660                btrfs_lookup_bio_sums(root, inode, comp_bio,
661                              sums);
662            }
663            sums += (comp_bio->bi_size + root->sectorsize - 1) /
664                root->sectorsize;
665
666            ret = btrfs_map_bio(root, READ, comp_bio,
667                        mirror_num, 0);
668            BUG_ON(ret);
669
670            bio_put(comp_bio);
671
672            comp_bio = compressed_bio_alloc(bdev, cur_disk_byte,
673                            GFP_NOFS);
674            comp_bio->bi_private = cb;
675            comp_bio->bi_end_io = end_compressed_bio_read;
676
677            bio_add_page(comp_bio, page, PAGE_CACHE_SIZE, 0);
678        }
679        cur_disk_byte += PAGE_CACHE_SIZE;
680    }
681    bio_get(comp_bio);
682
683    ret = btrfs_bio_wq_end_io(root->fs_info, comp_bio, 0);
684    BUG_ON(ret);
685
686    if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM))
687        btrfs_lookup_bio_sums(root, inode, comp_bio, sums);
688
689    ret = btrfs_map_bio(root, READ, comp_bio, mirror_num, 0);
690    BUG_ON(ret);
691
692    bio_put(comp_bio);
693    return 0;
694}
695

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