1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Copyright (C) 2008 Oracle.  All rights reserved.
   4 */
   5
   6#include <linux/kernel.h>
   7#include <linux/bio.h>
 
   8#include <linux/file.h>
   9#include <linux/fs.h>
  10#include <linux/pagemap.h>
  11#include <linux/highmem.h>
  12#include <linux/time.h>
  13#include <linux/init.h>
  14#include <linux/string.h>
  15#include <linux/backing-dev.h>
 
 
  16#include <linux/writeback.h>
 
  17#include <linux/slab.h>
  18#include <linux/sched/mm.h>
  19#include <linux/log2.h>
  20#include <crypto/hash.h>
  21#include "misc.h"
  22#include "ctree.h"
  23#include "disk-io.h"
  24#include "transaction.h"
  25#include "btrfs_inode.h"
  26#include "volumes.h"
  27#include "ordered-data.h"
  28#include "compression.h"
  29#include "extent_io.h"
  30#include "extent_map.h"
  31
  32int zlib_compress_pages(struct list_head *ws, struct address_space *mapping,
  33		u64 start, struct page **pages, unsigned long *out_pages,
  34		unsigned long *total_in, unsigned long *total_out);
  35int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
  36int zlib_decompress(struct list_head *ws, unsigned char *data_in,
  37		struct page *dest_page, unsigned long start_byte, size_t srclen,
  38		size_t destlen);
  39struct list_head *zlib_alloc_workspace(unsigned int level);
  40void zlib_free_workspace(struct list_head *ws);
  41struct list_head *zlib_get_workspace(unsigned int level);
  42
  43int lzo_compress_pages(struct list_head *ws, struct address_space *mapping,
  44		u64 start, struct page **pages, unsigned long *out_pages,
  45		unsigned long *total_in, unsigned long *total_out);
  46int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
  47int lzo_decompress(struct list_head *ws, unsigned char *data_in,
  48		struct page *dest_page, unsigned long start_byte, size_t srclen,
  49		size_t destlen);
  50struct list_head *lzo_alloc_workspace(unsigned int level);
  51void lzo_free_workspace(struct list_head *ws);
  52
  53int zstd_compress_pages(struct list_head *ws, struct address_space *mapping,
  54		u64 start, struct page **pages, unsigned long *out_pages,
  55		unsigned long *total_in, unsigned long *total_out);
  56int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb);
  57int zstd_decompress(struct list_head *ws, unsigned char *data_in,
  58		struct page *dest_page, unsigned long start_byte, size_t srclen,
  59		size_t destlen);
  60void zstd_init_workspace_manager(void);
  61void zstd_cleanup_workspace_manager(void);
  62struct list_head *zstd_alloc_workspace(unsigned int level);
  63void zstd_free_workspace(struct list_head *ws);
  64struct list_head *zstd_get_workspace(unsigned int level);
  65void zstd_put_workspace(struct list_head *ws);
  66
  67static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
  68
  69const char* btrfs_compress_type2str(enum btrfs_compression_type type)
  70{
  71	switch (type) {
  72	case BTRFS_COMPRESS_ZLIB:
  73	case BTRFS_COMPRESS_LZO:
  74	case BTRFS_COMPRESS_ZSTD:
  75	case BTRFS_COMPRESS_NONE:
  76		return btrfs_compress_types[type];
  77	default:
  78		break;
  79	}
  80
  81	return NULL;
  82}
  83
  84bool btrfs_compress_is_valid_type(const char *str, size_t len)
  85{
  86	int i;
  87
  88	for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
  89		size_t comp_len = strlen(btrfs_compress_types[i]);
  90
  91		if (len < comp_len)
  92			continue;
  93
  94		if (!strncmp(btrfs_compress_types[i], str, comp_len))
  95			return true;
  96	}
  97	return false;
  98}
  99
 100static int compression_compress_pages(int type, struct list_head *ws,
 101               struct address_space *mapping, u64 start, struct page **pages,
 102               unsigned long *out_pages, unsigned long *total_in,
 103               unsigned long *total_out)
 104{
 105	switch (type) {
 106	case BTRFS_COMPRESS_ZLIB:
 107		return zlib_compress_pages(ws, mapping, start, pages,
 108				out_pages, total_in, total_out);
 109	case BTRFS_COMPRESS_LZO:
 110		return lzo_compress_pages(ws, mapping, start, pages,
 111				out_pages, total_in, total_out);
 112	case BTRFS_COMPRESS_ZSTD:
 113		return zstd_compress_pages(ws, mapping, start, pages,
 114				out_pages, total_in, total_out);
 115	case BTRFS_COMPRESS_NONE:
 116	default:
 117		/*
 118		 * This can't happen, the type is validated several times
 119		 * before we get here. As a sane fallback, return what the
 120		 * callers will understand as 'no compression happened'.
 121		 */
 122		return -E2BIG;
 123	}
 124}
 125
 126static int compression_decompress_bio(int type, struct list_head *ws,
 127		struct compressed_bio *cb)
 128{
 129	switch (type) {
 130	case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb);
 131	case BTRFS_COMPRESS_LZO:  return lzo_decompress_bio(ws, cb);
 132	case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb);
 133	case BTRFS_COMPRESS_NONE:
 134	default:
 135		/*
 136		 * This can't happen, the type is validated several times
 137		 * before we get here.
 138		 */
 139		BUG();
 140	}
 141}
 142
 143static int compression_decompress(int type, struct list_head *ws,
 144               unsigned char *data_in, struct page *dest_page,
 145               unsigned long start_byte, size_t srclen, size_t destlen)
 146{
 147	switch (type) {
 148	case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page,
 149						start_byte, srclen, destlen);
 150	case BTRFS_COMPRESS_LZO:  return lzo_decompress(ws, data_in, dest_page,
 151						start_byte, srclen, destlen);
 152	case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page,
 153						start_byte, srclen, destlen);
 154	case BTRFS_COMPRESS_NONE:
 155	default:
 156		/*
 157		 * This can't happen, the type is validated several times
 158		 * before we get here.
 159		 */
 160		BUG();
 161	}
 162}
 163
 164static int btrfs_decompress_bio(struct compressed_bio *cb);
 165
 166static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
 167				      unsigned long disk_size)
 168{
 169	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 170
 171	return sizeof(struct compressed_bio) +
 172		(DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
 173}
 174
 175static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
 
 176				 u64 disk_start)
 177{
 178	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 179	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
 180	const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 181	struct page *page;
 182	unsigned long i;
 183	char *kaddr;
 184	u8 csum[BTRFS_CSUM_SIZE];
 185	struct compressed_bio *cb = bio->bi_private;
 186	u8 *cb_sum = cb->sums;
 187
 188	if (inode->flags & BTRFS_INODE_NODATASUM)
 189		return 0;
 190
 191	shash->tfm = fs_info->csum_shash;
 192
 193	for (i = 0; i < cb->nr_pages; i++) {
 194		page = cb->compressed_pages[i];
 
 195
 196		kaddr = kmap_atomic(page);
 197		crypto_shash_digest(shash, kaddr, PAGE_SIZE, csum);
 
 198		kunmap_atomic(kaddr);
 199
 200		if (memcmp(&csum, cb_sum, csum_size)) {
 201			btrfs_print_data_csum_error(inode, disk_start,
 202					csum, cb_sum, cb->mirror_num);
 203			if (btrfs_io_bio(bio)->device)
 204				btrfs_dev_stat_inc_and_print(
 205					btrfs_io_bio(bio)->device,
 206					BTRFS_DEV_STAT_CORRUPTION_ERRS);
 207			return -EIO;
 208		}
 209		cb_sum += csum_size;
 
 210	}
 211	return 0;
 
 
 212}
 213
 214/* when we finish reading compressed pages from the disk, we
 215 * decompress them and then run the bio end_io routines on the
 216 * decompressed pages (in the inode address space).
 217 *
 218 * This allows the checksumming and other IO error handling routines
 219 * to work normally
 220 *
 221 * The compressed pages are freed here, and it must be run
 222 * in process context
 223 */
 224static void end_compressed_bio_read(struct bio *bio)
 225{
 226	struct compressed_bio *cb = bio->bi_private;
 227	struct inode *inode;
 228	struct page *page;
 229	unsigned long index;
 230	unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
 231	int ret = 0;
 232
 233	if (bio->bi_status)
 234		cb->errors = 1;
 235
 236	/* if there are more bios still pending for this compressed
 237	 * extent, just exit
 238	 */
 239	if (!refcount_dec_and_test(&cb->pending_bios))
 240		goto out;
 241
 242	/*
 243	 * Record the correct mirror_num in cb->orig_bio so that
 244	 * read-repair can work properly.
 245	 */
 
 246	btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
 247	cb->mirror_num = mirror;
 248
 249	/*
 250	 * Some IO in this cb have failed, just skip checksum as there
 251	 * is no way it could be correct.
 252	 */
 253	if (cb->errors == 1)
 254		goto csum_failed;
 255
 256	inode = cb->inode;
 257	ret = check_compressed_csum(BTRFS_I(inode), bio,
 258				    (u64)bio->bi_iter.bi_sector << 9);
 259	if (ret)
 260		goto csum_failed;
 261
 262	/* ok, we're the last bio for this extent, lets start
 263	 * the decompression.
 264	 */
 265	ret = btrfs_decompress_bio(cb);
 266
 267csum_failed:
 268	if (ret)
 269		cb->errors = 1;
 270
 271	/* release the compressed pages */
 272	index = 0;
 273	for (index = 0; index < cb->nr_pages; index++) {
 274		page = cb->compressed_pages[index];
 275		page->mapping = NULL;
 276		put_page(page);
 277	}
 278
 279	/* do io completion on the original bio */
 280	if (cb->errors) {
 281		bio_io_error(cb->orig_bio);
 282	} else {
 
 283		struct bio_vec *bvec;
 284		struct bvec_iter_all iter_all;
 285
 286		/*
 287		 * we have verified the checksum already, set page
 288		 * checked so the end_io handlers know about it
 289		 */
 290		ASSERT(!bio_flagged(bio, BIO_CLONED));
 291		bio_for_each_segment_all(bvec, cb->orig_bio, iter_all)
 292			SetPageChecked(bvec->bv_page);
 293
 294		bio_endio(cb->orig_bio);
 295	}
 296
 297	/* finally free the cb struct */
 298	kfree(cb->compressed_pages);
 299	kfree(cb);
 300out:
 301	bio_put(bio);
 302}
 303
 304/*
 305 * Clear the writeback bits on all of the file
 306 * pages for a compressed write
 307 */
 308static noinline void end_compressed_writeback(struct inode *inode,
 309					      const struct compressed_bio *cb)
 310{
 311	unsigned long index = cb->start >> PAGE_SHIFT;
 312	unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
 313	struct page *pages[16];
 314	unsigned long nr_pages = end_index - index + 1;
 315	int i;
 316	int ret;
 317
 318	if (cb->errors)
 319		mapping_set_error(inode->i_mapping, -EIO);
 320
 321	while (nr_pages > 0) {
 322		ret = find_get_pages_contig(inode->i_mapping, index,
 323				     min_t(unsigned long,
 324				     nr_pages, ARRAY_SIZE(pages)), pages);
 325		if (ret == 0) {
 326			nr_pages -= 1;
 327			index += 1;
 328			continue;
 329		}
 330		for (i = 0; i < ret; i++) {
 331			if (cb->errors)
 332				SetPageError(pages[i]);
 333			end_page_writeback(pages[i]);
 334			put_page(pages[i]);
 335		}
 336		nr_pages -= ret;
 337		index += ret;
 338	}
 339	/* the inode may be gone now */
 340}
 341
 342/*
 343 * do the cleanup once all the compressed pages hit the disk.
 344 * This will clear writeback on the file pages and free the compressed
 345 * pages.
 346 *
 347 * This also calls the writeback end hooks for the file pages so that
 348 * metadata and checksums can be updated in the file.
 349 */
 350static void end_compressed_bio_write(struct bio *bio)
 351{
 
 352	struct compressed_bio *cb = bio->bi_private;
 353	struct inode *inode;
 354	struct page *page;
 355	unsigned long index;
 356
 357	if (bio->bi_status)
 358		cb->errors = 1;
 359
 360	/* if there are more bios still pending for this compressed
 361	 * extent, just exit
 362	 */
 363	if (!refcount_dec_and_test(&cb->pending_bios))
 364		goto out;
 365
 366	/* ok, we're the last bio for this extent, step one is to
 367	 * call back into the FS and do all the end_io operations
 368	 */
 369	inode = cb->inode;
 
 370	cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
 371	btrfs_writepage_endio_finish_ordered(cb->compressed_pages[0],
 372			cb->start, cb->start + cb->len - 1,
 373			bio->bi_status == BLK_STS_OK);
 
 
 
 374	cb->compressed_pages[0]->mapping = NULL;
 375
 376	end_compressed_writeback(inode, cb);
 377	/* note, our inode could be gone now */
 378
 379	/*
 380	 * release the compressed pages, these came from alloc_page and
 381	 * are not attached to the inode at all
 382	 */
 383	index = 0;
 384	for (index = 0; index < cb->nr_pages; index++) {
 385		page = cb->compressed_pages[index];
 386		page->mapping = NULL;
 387		put_page(page);
 388	}
 389
 390	/* finally free the cb struct */
 391	kfree(cb->compressed_pages);
 392	kfree(cb);
 393out:
 394	bio_put(bio);
 395}
 396
 397/*
 398 * worker function to build and submit bios for previously compressed pages.
 399 * The corresponding pages in the inode should be marked for writeback
 400 * and the compressed pages should have a reference on them for dropping
 401 * when the IO is complete.
 402 *
 403 * This also checksums the file bytes and gets things ready for
 404 * the end io hooks.
 405 */
 406blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 407				 unsigned long len, u64 disk_start,
 408				 unsigned long compressed_len,
 409				 struct page **compressed_pages,
 410				 unsigned long nr_pages,
 411				 unsigned int write_flags,
 412				 struct cgroup_subsys_state *blkcg_css)
 413{
 414	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 415	struct bio *bio = NULL;
 416	struct compressed_bio *cb;
 417	unsigned long bytes_left;
 
 418	int pg_index = 0;
 419	struct page *page;
 420	u64 first_byte = disk_start;
 
 421	blk_status_t ret;
 422	int skip_sum = inode->flags & BTRFS_INODE_NODATASUM;
 423
 424	WARN_ON(!PAGE_ALIGNED(start));
 425	cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
 426	if (!cb)
 427		return BLK_STS_RESOURCE;
 428	refcount_set(&cb->pending_bios, 0);
 429	cb->errors = 0;
 430	cb->inode = &inode->vfs_inode;
 431	cb->start = start;
 432	cb->len = len;
 433	cb->mirror_num = 0;
 434	cb->compressed_pages = compressed_pages;
 435	cb->compressed_len = compressed_len;
 436	cb->orig_bio = NULL;
 437	cb->nr_pages = nr_pages;
 438
 439	bio = btrfs_bio_alloc(first_byte);
 
 
 440	bio->bi_opf = REQ_OP_WRITE | write_flags;
 441	bio->bi_private = cb;
 442	bio->bi_end_io = end_compressed_bio_write;
 443
 444	if (blkcg_css) {
 445		bio->bi_opf |= REQ_CGROUP_PUNT;
 446		kthread_associate_blkcg(blkcg_css);
 447	}
 448	refcount_set(&cb->pending_bios, 1);
 449
 450	/* create and submit bios for the compressed pages */
 451	bytes_left = compressed_len;
 452	for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
 453		int submit = 0;
 454
 455		page = compressed_pages[pg_index];
 456		page->mapping = inode->vfs_inode.i_mapping;
 457		if (bio->bi_iter.bi_size)
 458			submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,
 459							  0);
 
 460
 461		page->mapping = NULL;
 462		if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
 463		    PAGE_SIZE) {
 464			/*
 465			 * inc the count before we submit the bio so
 466			 * we know the end IO handler won't happen before
 467			 * we inc the count.  Otherwise, the cb might get
 468			 * freed before we're done setting it up
 469			 */
 470			refcount_inc(&cb->pending_bios);
 471			ret = btrfs_bio_wq_end_io(fs_info, bio,
 472						  BTRFS_WQ_ENDIO_DATA);
 473			BUG_ON(ret); /* -ENOMEM */
 474
 475			if (!skip_sum) {
 476				ret = btrfs_csum_one_bio(inode, bio, start, 1);
 477				BUG_ON(ret); /* -ENOMEM */
 478			}
 479
 480			ret = btrfs_map_bio(fs_info, bio, 0);
 481			if (ret) {
 482				bio->bi_status = ret;
 483				bio_endio(bio);
 484			}
 485
 486			bio = btrfs_bio_alloc(first_byte);
 487			bio->bi_opf = REQ_OP_WRITE | write_flags;
 488			bio->bi_private = cb;
 489			bio->bi_end_io = end_compressed_bio_write;
 490			if (blkcg_css)
 491				bio->bi_opf |= REQ_CGROUP_PUNT;
 492			bio_add_page(bio, page, PAGE_SIZE, 0);
 493		}
 494		if (bytes_left < PAGE_SIZE) {
 495			btrfs_info(fs_info,
 496					"bytes left %lu compress len %lu nr %lu",
 497			       bytes_left, cb->compressed_len, cb->nr_pages);
 498		}
 499		bytes_left -= PAGE_SIZE;
 500		first_byte += PAGE_SIZE;
 501		cond_resched();
 502	}
 503
 504	ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
 505	BUG_ON(ret); /* -ENOMEM */
 506
 507	if (!skip_sum) {
 508		ret = btrfs_csum_one_bio(inode, bio, start, 1);
 509		BUG_ON(ret); /* -ENOMEM */
 510	}
 511
 512	ret = btrfs_map_bio(fs_info, bio, 0);
 513	if (ret) {
 514		bio->bi_status = ret;
 515		bio_endio(bio);
 516	}
 517
 518	if (blkcg_css)
 519		kthread_associate_blkcg(NULL);
 520
 521	return 0;
 522}
 523
 524static u64 bio_end_offset(struct bio *bio)
 525{
 526	struct bio_vec *last = bio_last_bvec_all(bio);
 527
 528	return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
 529}
 530
 531static noinline int add_ra_bio_pages(struct inode *inode,
 532				     u64 compressed_end,
 533				     struct compressed_bio *cb)
 534{
 535	unsigned long end_index;
 536	unsigned long pg_index;
 537	u64 last_offset;
 538	u64 isize = i_size_read(inode);
 539	int ret;
 540	struct page *page;
 541	unsigned long nr_pages = 0;
 542	struct extent_map *em;
 543	struct address_space *mapping = inode->i_mapping;
 544	struct extent_map_tree *em_tree;
 545	struct extent_io_tree *tree;
 546	u64 end;
 547	int misses = 0;
 548
 549	last_offset = bio_end_offset(cb->orig_bio);
 550	em_tree = &BTRFS_I(inode)->extent_tree;
 551	tree = &BTRFS_I(inode)->io_tree;
 552
 553	if (isize == 0)
 554		return 0;
 555
 556	end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
 557
 558	while (last_offset < compressed_end) {
 559		pg_index = last_offset >> PAGE_SHIFT;
 560
 561		if (pg_index > end_index)
 562			break;
 563
 564		page = xa_load(&mapping->i_pages, pg_index);
 565		if (page && !xa_is_value(page)) {
 
 
 566			misses++;
 567			if (misses > 4)
 568				break;
 569			goto next;
 570		}
 571
 572		page = __page_cache_alloc(mapping_gfp_constraint(mapping,
 573								 ~__GFP_FS));
 574		if (!page)
 575			break;
 576
 577		if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
 578			put_page(page);
 579			goto next;
 580		}
 581
 582		end = last_offset + PAGE_SIZE - 1;
 583		/*
 584		 * at this point, we have a locked page in the page cache
 585		 * for these bytes in the file.  But, we have to make
 586		 * sure they map to this compressed extent on disk.
 587		 */
 588		set_page_extent_mapped(page);
 589		lock_extent(tree, last_offset, end);
 590		read_lock(&em_tree->lock);
 591		em = lookup_extent_mapping(em_tree, last_offset,
 592					   PAGE_SIZE);
 593		read_unlock(&em_tree->lock);
 594
 595		if (!em || last_offset < em->start ||
 596		    (last_offset + PAGE_SIZE > extent_map_end(em)) ||
 597		    (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
 598			free_extent_map(em);
 599			unlock_extent(tree, last_offset, end);
 600			unlock_page(page);
 601			put_page(page);
 602			break;
 603		}
 604		free_extent_map(em);
 605
 606		if (page->index == end_index) {
 607			char *userpage;
 608			size_t zero_offset = offset_in_page(isize);
 609
 610			if (zero_offset) {
 611				int zeros;
 612				zeros = PAGE_SIZE - zero_offset;
 613				userpage = kmap_atomic(page);
 614				memset(userpage + zero_offset, 0, zeros);
 615				flush_dcache_page(page);
 616				kunmap_atomic(userpage);
 617			}
 618		}
 619
 620		ret = bio_add_page(cb->orig_bio, page,
 621				   PAGE_SIZE, 0);
 622
 623		if (ret == PAGE_SIZE) {
 624			nr_pages++;
 625			put_page(page);
 626		} else {
 627			unlock_extent(tree, last_offset, end);
 628			unlock_page(page);
 629			put_page(page);
 630			break;
 631		}
 632next:
 633		last_offset += PAGE_SIZE;
 634	}
 635	return 0;
 636}
 637
 638/*
 639 * for a compressed read, the bio we get passed has all the inode pages
 640 * in it.  We don't actually do IO on those pages but allocate new ones
 641 * to hold the compressed pages on disk.
 642 *
 643 * bio->bi_iter.bi_sector points to the compressed extent on disk
 644 * bio->bi_io_vec points to all of the inode pages
 645 *
 646 * After the compressed pages are read, we copy the bytes into the
 647 * bio we were passed and then call the bio end_io calls
 648 */
 649blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 650				 int mirror_num, unsigned long bio_flags)
 651{
 652	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 
 653	struct extent_map_tree *em_tree;
 654	struct compressed_bio *cb;
 655	unsigned long compressed_len;
 656	unsigned long nr_pages;
 657	unsigned long pg_index;
 658	struct page *page;
 
 659	struct bio *comp_bio;
 660	u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9;
 661	u64 em_len;
 662	u64 em_start;
 663	struct extent_map *em;
 664	blk_status_t ret = BLK_STS_RESOURCE;
 665	int faili = 0;
 666	const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 667	u8 *sums;
 668
 
 669	em_tree = &BTRFS_I(inode)->extent_tree;
 670
 671	/* we need the actual starting offset of this extent in the file */
 672	read_lock(&em_tree->lock);
 673	em = lookup_extent_mapping(em_tree,
 674				   page_offset(bio_first_page_all(bio)),
 675				   PAGE_SIZE);
 676	read_unlock(&em_tree->lock);
 677	if (!em)
 678		return BLK_STS_IOERR;
 679
 680	compressed_len = em->block_len;
 681	cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
 682	if (!cb)
 683		goto out;
 684
 685	refcount_set(&cb->pending_bios, 0);
 686	cb->errors = 0;
 687	cb->inode = inode;
 688	cb->mirror_num = mirror_num;
 689	sums = cb->sums;
 690
 691	cb->start = em->orig_start;
 692	em_len = em->len;
 693	em_start = em->start;
 694
 695	free_extent_map(em);
 696	em = NULL;
 697
 698	cb->len = bio->bi_iter.bi_size;
 699	cb->compressed_len = compressed_len;
 700	cb->compress_type = extent_compress_type(bio_flags);
 701	cb->orig_bio = bio;
 702
 703	nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
 704	cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *),
 705				       GFP_NOFS);
 706	if (!cb->compressed_pages)
 707		goto fail1;
 708
 
 
 709	for (pg_index = 0; pg_index < nr_pages; pg_index++) {
 710		cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS |
 711							      __GFP_HIGHMEM);
 712		if (!cb->compressed_pages[pg_index]) {
 713			faili = pg_index - 1;
 714			ret = BLK_STS_RESOURCE;
 715			goto fail2;
 716		}
 717	}
 718	faili = nr_pages - 1;
 719	cb->nr_pages = nr_pages;
 720
 721	add_ra_bio_pages(inode, em_start + em_len, cb);
 722
 723	/* include any pages we added in add_ra-bio_pages */
 724	cb->len = bio->bi_iter.bi_size;
 725
 726	comp_bio = btrfs_bio_alloc(cur_disk_byte);
 727	comp_bio->bi_opf = REQ_OP_READ;
 728	comp_bio->bi_private = cb;
 729	comp_bio->bi_end_io = end_compressed_bio_read;
 730	refcount_set(&cb->pending_bios, 1);
 731
 732	for (pg_index = 0; pg_index < nr_pages; pg_index++) {
 733		int submit = 0;
 734
 735		page = cb->compressed_pages[pg_index];
 736		page->mapping = inode->i_mapping;
 737		page->index = em_start >> PAGE_SHIFT;
 738
 739		if (comp_bio->bi_iter.bi_size)
 740			submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE,
 741							  comp_bio, 0);
 
 742
 743		page->mapping = NULL;
 744		if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) <
 745		    PAGE_SIZE) {
 746			unsigned int nr_sectors;
 747
 748			ret = btrfs_bio_wq_end_io(fs_info, comp_bio,
 749						  BTRFS_WQ_ENDIO_DATA);
 750			BUG_ON(ret); /* -ENOMEM */
 751
 752			/*
 753			 * inc the count before we submit the bio so
 754			 * we know the end IO handler won't happen before
 755			 * we inc the count.  Otherwise, the cb might get
 756			 * freed before we're done setting it up
 757			 */
 758			refcount_inc(&cb->pending_bios);
 759
 760			if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 761				ret = btrfs_lookup_bio_sums(inode, comp_bio,
 762							    (u64)-1, sums);
 763				BUG_ON(ret); /* -ENOMEM */
 764			}
 
 
 765
 766			nr_sectors = DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
 767						  fs_info->sectorsize);
 768			sums += csum_size * nr_sectors;
 769
 770			ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
 771			if (ret) {
 772				comp_bio->bi_status = ret;
 773				bio_endio(comp_bio);
 774			}
 775
 776			comp_bio = btrfs_bio_alloc(cur_disk_byte);
 777			comp_bio->bi_opf = REQ_OP_READ;
 778			comp_bio->bi_private = cb;
 779			comp_bio->bi_end_io = end_compressed_bio_read;
 780
 781			bio_add_page(comp_bio, page, PAGE_SIZE, 0);
 782		}
 783		cur_disk_byte += PAGE_SIZE;
 784	}
 785
 786	ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
 787	BUG_ON(ret); /* -ENOMEM */
 788
 789	if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
 790		ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1, sums);
 791		BUG_ON(ret); /* -ENOMEM */
 792	}
 793
 794	ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
 795	if (ret) {
 796		comp_bio->bi_status = ret;
 797		bio_endio(comp_bio);
 798	}
 799
 800	return 0;
 801
 802fail2:
 803	while (faili >= 0) {
 804		__free_page(cb->compressed_pages[faili]);
 805		faili--;
 806	}
 807
 808	kfree(cb->compressed_pages);
 809fail1:
 810	kfree(cb);
 811out:
 812	free_extent_map(em);
 813	return ret;
 814}
 815
 816/*
 817 * Heuristic uses systematic sampling to collect data from the input data
 818 * range, the logic can be tuned by the following constants:
 819 *
 820 * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample
 821 * @SAMPLING_INTERVAL  - range from which the sampled data can be collected
 822 */
 823#define SAMPLING_READ_SIZE	(16)
 824#define SAMPLING_INTERVAL	(256)
 825
 826/*
 827 * For statistical analysis of the input data we consider bytes that form a
 828 * Galois Field of 256 objects. Each object has an attribute count, ie. how
 829 * many times the object appeared in the sample.
 830 */
 831#define BUCKET_SIZE		(256)
 832
 833/*
 834 * The size of the sample is based on a statistical sampling rule of thumb.
 835 * The common way is to perform sampling tests as long as the number of
 836 * elements in each cell is at least 5.
 837 *
 838 * Instead of 5, we choose 32 to obtain more accurate results.
 839 * If the data contain the maximum number of symbols, which is 256, we obtain a
 840 * sample size bound by 8192.
 841 *
 842 * For a sample of at most 8KB of data per data range: 16 consecutive bytes
 843 * from up to 512 locations.
 844 */
 845#define MAX_SAMPLE_SIZE		(BTRFS_MAX_UNCOMPRESSED *		\
 846				 SAMPLING_READ_SIZE / SAMPLING_INTERVAL)
 847
 848struct bucket_item {
 849	u32 count;
 850};
 851
 852struct heuristic_ws {
 853	/* Partial copy of input data */
 854	u8 *sample;
 855	u32 sample_size;
 856	/* Buckets store counters for each byte value */
 857	struct bucket_item *bucket;
 858	/* Sorting buffer */
 859	struct bucket_item *bucket_b;
 860	struct list_head list;
 861};
 862
 863static struct workspace_manager heuristic_wsm;
 864
 865static void free_heuristic_ws(struct list_head *ws)
 866{
 867	struct heuristic_ws *workspace;
 868
 869	workspace = list_entry(ws, struct heuristic_ws, list);
 870
 871	kvfree(workspace->sample);
 872	kfree(workspace->bucket);
 873	kfree(workspace->bucket_b);
 874	kfree(workspace);
 875}
 876
 877static struct list_head *alloc_heuristic_ws(unsigned int level)
 878{
 879	struct heuristic_ws *ws;
 880
 881	ws = kzalloc(sizeof(*ws), GFP_KERNEL);
 882	if (!ws)
 883		return ERR_PTR(-ENOMEM);
 884
 885	ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL);
 886	if (!ws->sample)
 887		goto fail;
 888
 889	ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL);
 890	if (!ws->bucket)
 891		goto fail;
 892
 893	ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL);
 894	if (!ws->bucket_b)
 895		goto fail;
 896
 897	INIT_LIST_HEAD(&ws->list);
 898	return &ws->list;
 899fail:
 900	free_heuristic_ws(&ws->list);
 901	return ERR_PTR(-ENOMEM);
 902}
 903
 904const struct btrfs_compress_op btrfs_heuristic_compress = {
 905	.workspace_manager = &heuristic_wsm,
 
 
 
 
 
 
 
 906};
 907
 
 
 
 
 908static const struct btrfs_compress_op * const btrfs_compress_op[] = {
 909	/* The heuristic is represented as compression type 0 */
 910	&btrfs_heuristic_compress,
 911	&btrfs_zlib_compress,
 912	&btrfs_lzo_compress,
 913	&btrfs_zstd_compress,
 914};
 915
 916static struct list_head *alloc_workspace(int type, unsigned int level)
 917{
 918	switch (type) {
 919	case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level);
 920	case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level);
 921	case BTRFS_COMPRESS_LZO:  return lzo_alloc_workspace(level);
 922	case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level);
 923	default:
 924		/*
 925		 * This can't happen, the type is validated several times
 926		 * before we get here.
 927		 */
 928		BUG();
 929	}
 930}
 931
 932static void free_workspace(int type, struct list_head *ws)
 933{
 934	switch (type) {
 935	case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws);
 936	case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws);
 937	case BTRFS_COMPRESS_LZO:  return lzo_free_workspace(ws);
 938	case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws);
 939	default:
 940		/*
 941		 * This can't happen, the type is validated several times
 942		 * before we get here.
 943		 */
 944		BUG();
 945	}
 946}
 947
 948static void btrfs_init_workspace_manager(int type)
 949{
 950	struct workspace_manager *wsm;
 951	struct list_head *workspace;
 
 952
 953	wsm = btrfs_compress_op[type]->workspace_manager;
 954	INIT_LIST_HEAD(&wsm->idle_ws);
 955	spin_lock_init(&wsm->ws_lock);
 956	atomic_set(&wsm->total_ws, 0);
 957	init_waitqueue_head(&wsm->ws_wait);
 958
 959	/*
 960	 * Preallocate one workspace for each compression type so we can
 961	 * guarantee forward progress in the worst case
 962	 */
 963	workspace = alloc_workspace(type, 0);
 964	if (IS_ERR(workspace)) {
 965		pr_warn(
 966	"BTRFS: cannot preallocate compression workspace, will try later\n");
 967	} else {
 968		atomic_set(&wsm->total_ws, 1);
 969		wsm->free_ws = 1;
 970		list_add(workspace, &wsm->idle_ws);
 971	}
 972}
 973
 974static void btrfs_cleanup_workspace_manager(int type)
 975{
 976	struct workspace_manager *wsman;
 977	struct list_head *ws;
 
 978
 979	wsman = btrfs_compress_op[type]->workspace_manager;
 980	while (!list_empty(&wsman->idle_ws)) {
 981		ws = wsman->idle_ws.next;
 982		list_del(ws);
 983		free_workspace(type, ws);
 984		atomic_dec(&wsman->total_ws);
 
 
 
 
 
 
 985	}
 986}
 987
 988/*
 989 * This finds an available workspace or allocates a new one.
 990 * If it's not possible to allocate a new one, waits until there's one.
 991 * Preallocation makes a forward progress guarantees and we do not return
 992 * errors.
 993 */
 994struct list_head *btrfs_get_workspace(int type, unsigned int level)
 995{
 996	struct workspace_manager *wsm;
 997	struct list_head *workspace;
 998	int cpus = num_online_cpus();
 
 999	unsigned nofs_flag;
1000	struct list_head *idle_ws;
1001	spinlock_t *ws_lock;
1002	atomic_t *total_ws;
1003	wait_queue_head_t *ws_wait;
1004	int *free_ws;
1005
1006	wsm = btrfs_compress_op[type]->workspace_manager;
1007	idle_ws	 = &wsm->idle_ws;
1008	ws_lock	 = &wsm->ws_lock;
1009	total_ws = &wsm->total_ws;
1010	ws_wait	 = &wsm->ws_wait;
1011	free_ws	 = &wsm->free_ws;
 
 
 
 
 
 
 
1012
1013again:
1014	spin_lock(ws_lock);
1015	if (!list_empty(idle_ws)) {
1016		workspace = idle_ws->next;
1017		list_del(workspace);
1018		(*free_ws)--;
1019		spin_unlock(ws_lock);
1020		return workspace;
1021
1022	}
1023	if (atomic_read(total_ws) > cpus) {
1024		DEFINE_WAIT(wait);
1025
1026		spin_unlock(ws_lock);
1027		prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
1028		if (atomic_read(total_ws) > cpus && !*free_ws)
1029			schedule();
1030		finish_wait(ws_wait, &wait);
1031		goto again;
1032	}
1033	atomic_inc(total_ws);
1034	spin_unlock(ws_lock);
1035
1036	/*
1037	 * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have
1038	 * to turn it off here because we might get called from the restricted
1039	 * context of btrfs_compress_bio/btrfs_compress_pages
1040	 */
1041	nofs_flag = memalloc_nofs_save();
1042	workspace = alloc_workspace(type, level);
 
 
 
1043	memalloc_nofs_restore(nofs_flag);
1044
1045	if (IS_ERR(workspace)) {
1046		atomic_dec(total_ws);
1047		wake_up(ws_wait);
1048
1049		/*
1050		 * Do not return the error but go back to waiting. There's a
1051		 * workspace preallocated for each type and the compression
1052		 * time is bounded so we get to a workspace eventually. This
1053		 * makes our caller's life easier.
1054		 *
1055		 * To prevent silent and low-probability deadlocks (when the
1056		 * initial preallocation fails), check if there are any
1057		 * workspaces at all.
1058		 */
1059		if (atomic_read(total_ws) == 0) {
1060			static DEFINE_RATELIMIT_STATE(_rs,
1061					/* once per minute */ 60 * HZ,
1062					/* no burst */ 1);
1063
1064			if (__ratelimit(&_rs)) {
1065				pr_warn("BTRFS: no compression workspaces, low memory, retrying\n");
1066			}
1067		}
1068		goto again;
1069	}
1070	return workspace;
1071}
1072
1073static struct list_head *get_workspace(int type, int level)
1074{
1075	switch (type) {
1076	case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level);
1077	case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level);
1078	case BTRFS_COMPRESS_LZO:  return btrfs_get_workspace(type, level);
1079	case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level);
1080	default:
1081		/*
1082		 * This can't happen, the type is validated several times
1083		 * before we get here.
1084		 */
1085		BUG();
1086	}
1087}
1088
1089/*
1090 * put a workspace struct back on the list or free it if we have enough
1091 * idle ones sitting around
1092 */
1093void btrfs_put_workspace(int type, struct list_head *ws)
 
1094{
1095	struct workspace_manager *wsm;
1096	struct list_head *idle_ws;
1097	spinlock_t *ws_lock;
1098	atomic_t *total_ws;
1099	wait_queue_head_t *ws_wait;
1100	int *free_ws;
1101
1102	wsm = btrfs_compress_op[type]->workspace_manager;
1103	idle_ws	 = &wsm->idle_ws;
1104	ws_lock	 = &wsm->ws_lock;
1105	total_ws = &wsm->total_ws;
1106	ws_wait	 = &wsm->ws_wait;
1107	free_ws	 = &wsm->free_ws;
 
 
 
 
 
 
 
1108
1109	spin_lock(ws_lock);
1110	if (*free_ws <= num_online_cpus()) {
1111		list_add(ws, idle_ws);
1112		(*free_ws)++;
1113		spin_unlock(ws_lock);
1114		goto wake;
1115	}
1116	spin_unlock(ws_lock);
1117
1118	free_workspace(type, ws);
 
 
 
1119	atomic_dec(total_ws);
1120wake:
1121	cond_wake_up(ws_wait);
 
 
 
 
 
1122}
1123
1124static void put_workspace(int type, struct list_head *ws)
1125{
1126	switch (type) {
1127	case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws);
1128	case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws);
1129	case BTRFS_COMPRESS_LZO:  return btrfs_put_workspace(type, ws);
1130	case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws);
1131	default:
1132		/*
1133		 * This can't happen, the type is validated several times
1134		 * before we get here.
1135		 */
1136		BUG();
1137	}
1138}
1139
1140/*
1141 * Adjust @level according to the limits of the compression algorithm or
1142 * fallback to default
1143 */
1144static unsigned int btrfs_compress_set_level(int type, unsigned level)
1145{
1146	const struct btrfs_compress_op *ops = btrfs_compress_op[type];
 
1147
1148	if (level == 0)
1149		level = ops->default_level;
1150	else
1151		level = min(level, ops->max_level);
 
 
1152
1153	return level;
 
 
 
 
 
 
 
1154}
1155
1156/*
1157 * Given an address space and start and length, compress the bytes into @pages
1158 * that are allocated on demand.
1159 *
1160 * @type_level is encoded algorithm and level, where level 0 means whatever
1161 * default the algorithm chooses and is opaque here;
1162 * - compression algo are 0-3
1163 * - the level are bits 4-7
1164 *
1165 * @out_pages is an in/out parameter, holds maximum number of pages to allocate
1166 * and returns number of actually allocated pages
1167 *
1168 * @total_in is used to return the number of bytes actually read.  It
1169 * may be smaller than the input length if we had to exit early because we
1170 * ran out of room in the pages array or because we cross the
1171 * max_out threshold.
1172 *
1173 * @total_out is an in/out parameter, must be set to the input length and will
1174 * be also used to return the total number of compressed bytes
1175 *
1176 * @max_out tells us the max number of bytes that we're allowed to
1177 * stuff into pages
1178 */
1179int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping,
1180			 u64 start, struct page **pages,
1181			 unsigned long *out_pages,
1182			 unsigned long *total_in,
1183			 unsigned long *total_out)
1184{
1185	int type = btrfs_compress_type(type_level);
1186	int level = btrfs_compress_level(type_level);
1187	struct list_head *workspace;
1188	int ret;
 
 
 
1189
1190	level = btrfs_compress_set_level(type, level);
1191	workspace = get_workspace(type, level);
1192	ret = compression_compress_pages(type, workspace, mapping, start, pages,
1193					 out_pages, total_in, total_out);
1194	put_workspace(type, workspace);
 
1195	return ret;
1196}
1197
1198/*
1199 * pages_in is an array of pages with compressed data.
1200 *
1201 * disk_start is the starting logical offset of this array in the file
1202 *
1203 * orig_bio contains the pages from the file that we want to decompress into
1204 *
1205 * srclen is the number of bytes in pages_in
1206 *
1207 * The basic idea is that we have a bio that was created by readpages.
1208 * The pages in the bio are for the uncompressed data, and they may not
1209 * be contiguous.  They all correspond to the range of bytes covered by
1210 * the compressed extent.
1211 */
1212static int btrfs_decompress_bio(struct compressed_bio *cb)
1213{
1214	struct list_head *workspace;
1215	int ret;
1216	int type = cb->compress_type;
1217
1218	workspace = get_workspace(type, 0);
1219	ret = compression_decompress_bio(type, workspace, cb);
1220	put_workspace(type, workspace);
1221
1222	return ret;
1223}
1224
1225/*
1226 * a less complex decompression routine.  Our compressed data fits in a
1227 * single page, and we want to read a single page out of it.
1228 * start_byte tells us the offset into the compressed data we're interested in
1229 */
1230int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page,
1231		     unsigned long start_byte, size_t srclen, size_t destlen)
1232{
1233	struct list_head *workspace;
1234	int ret;
1235
1236	workspace = get_workspace(type, 0);
1237	ret = compression_decompress(type, workspace, data_in, dest_page,
1238				     start_byte, srclen, destlen);
1239	put_workspace(type, workspace);
1240
1241	return ret;
1242}
 
1243
1244void __init btrfs_init_compress(void)
1245{
1246	btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE);
1247	btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB);
1248	btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO);
1249	zstd_init_workspace_manager();
1250}
1251
1252void __cold btrfs_exit_compress(void)
1253{
1254	btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE);
1255	btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB);
1256	btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO);
1257	zstd_cleanup_workspace_manager();
1258}
1259
1260/*
1261 * Copy uncompressed data from working buffer to pages.
1262 *
1263 * buf_start is the byte offset we're of the start of our workspace buffer.
1264 *
1265 * total_out is the last byte of the buffer
1266 */
1267int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start,
1268			      unsigned long total_out, u64 disk_start,
1269			      struct bio *bio)
1270{
1271	unsigned long buf_offset;
1272	unsigned long current_buf_start;
1273	unsigned long start_byte;
1274	unsigned long prev_start_byte;
1275	unsigned long working_bytes = total_out - buf_start;
1276	unsigned long bytes;
1277	char *kaddr;
1278	struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter);
1279
1280	/*
1281	 * start byte is the first byte of the page we're currently
1282	 * copying into relative to the start of the compressed data.
1283	 */
1284	start_byte = page_offset(bvec.bv_page) - disk_start;
1285
1286	/* we haven't yet hit data corresponding to this page */
1287	if (total_out <= start_byte)
1288		return 1;
1289
1290	/*
1291	 * the start of the data we care about is offset into
1292	 * the middle of our working buffer
1293	 */
1294	if (total_out > start_byte && buf_start < start_byte) {
1295		buf_offset = start_byte - buf_start;
1296		working_bytes -= buf_offset;
1297	} else {
1298		buf_offset = 0;
1299	}
1300	current_buf_start = buf_start;
1301
1302	/* copy bytes from the working buffer into the pages */
1303	while (working_bytes > 0) {
1304		bytes = min_t(unsigned long, bvec.bv_len,
1305				PAGE_SIZE - (buf_offset % PAGE_SIZE));
1306		bytes = min(bytes, working_bytes);
1307
1308		kaddr = kmap_atomic(bvec.bv_page);
1309		memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes);
1310		kunmap_atomic(kaddr);
1311		flush_dcache_page(bvec.bv_page);
1312
1313		buf_offset += bytes;
1314		working_bytes -= bytes;
1315		current_buf_start += bytes;
1316
1317		/* check if we need to pick another page */
1318		bio_advance(bio, bytes);
1319		if (!bio->bi_iter.bi_size)
1320			return 0;
1321		bvec = bio_iter_iovec(bio, bio->bi_iter);
1322		prev_start_byte = start_byte;
1323		start_byte = page_offset(bvec.bv_page) - disk_start;
1324
1325		/*
1326		 * We need to make sure we're only adjusting
1327		 * our offset into compression working buffer when
1328		 * we're switching pages.  Otherwise we can incorrectly
1329		 * keep copying when we were actually done.
1330		 */
1331		if (start_byte != prev_start_byte) {
1332			/*
1333			 * make sure our new page is covered by this
1334			 * working buffer
1335			 */
1336			if (total_out <= start_byte)
1337				return 1;
1338
1339			/*
1340			 * the next page in the biovec might not be adjacent
1341			 * to the last page, but it might still be found
1342			 * inside this working buffer. bump our offset pointer
1343			 */
1344			if (total_out > start_byte &&
1345			    current_buf_start < start_byte) {
1346				buf_offset = start_byte - buf_start;
1347				working_bytes = total_out - start_byte;
1348				current_buf_start = buf_start + buf_offset;
1349			}
1350		}
1351	}
1352
1353	return 1;
1354}
1355
1356/*
1357 * Shannon Entropy calculation
1358 *
1359 * Pure byte distribution analysis fails to determine compressibility of data.
1360 * Try calculating entropy to estimate the average minimum number of bits
1361 * needed to encode the sampled data.
1362 *
1363 * For convenience, return the percentage of needed bits, instead of amount of
1364 * bits directly.
1365 *
1366 * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy
1367 *			    and can be compressible with high probability
1368 *
1369 * @ENTROPY_LVL_HIGH - data are not compressible with high probability
1370 *
1371 * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate.
1372 */
1373#define ENTROPY_LVL_ACEPTABLE		(65)
1374#define ENTROPY_LVL_HIGH		(80)
1375
1376/*
1377 * For increasead precision in shannon_entropy calculation,
1378 * let's do pow(n, M) to save more digits after comma:
1379 *
1380 * - maximum int bit length is 64
1381 * - ilog2(MAX_SAMPLE_SIZE)	-> 13
1382 * - 13 * 4 = 52 < 64		-> M = 4
1383 *
1384 * So use pow(n, 4).
1385 */
1386static inline u32 ilog2_w(u64 n)
1387{
1388	return ilog2(n * n * n * n);
1389}
1390
1391static u32 shannon_entropy(struct heuristic_ws *ws)
1392{
1393	const u32 entropy_max = 8 * ilog2_w(2);
1394	u32 entropy_sum = 0;
1395	u32 p, p_base, sz_base;
1396	u32 i;
1397
1398	sz_base = ilog2_w(ws->sample_size);
1399	for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) {
1400		p = ws->bucket[i].count;
1401		p_base = ilog2_w(p);
1402		entropy_sum += p * (sz_base - p_base);
1403	}
1404
1405	entropy_sum /= ws->sample_size;
1406	return entropy_sum * 100 / entropy_max;
1407}
1408
1409#define RADIX_BASE		4U
1410#define COUNTERS_SIZE		(1U << RADIX_BASE)
1411
1412static u8 get4bits(u64 num, int shift) {
1413	u8 low4bits;
1414
1415	num >>= shift;
1416	/* Reverse order */
1417	low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE);
1418	return low4bits;
1419}
1420
1421/*
1422 * Use 4 bits as radix base
1423 * Use 16 u32 counters for calculating new position in buf array
1424 *
1425 * @array     - array that will be sorted
1426 * @array_buf - buffer array to store sorting results
1427 *              must be equal in size to @array
1428 * @num       - array size
1429 */
1430static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf,
1431		       int num)
1432{
1433	u64 max_num;
1434	u64 buf_num;
1435	u32 counters[COUNTERS_SIZE];
1436	u32 new_addr;
1437	u32 addr;
1438	int bitlen;
1439	int shift;
1440	int i;
1441
1442	/*
1443	 * Try avoid useless loop iterations for small numbers stored in big
1444	 * counters.  Example: 48 33 4 ... in 64bit array
1445	 */
1446	max_num = array[0].count;
1447	for (i = 1; i < num; i++) {
1448		buf_num = array[i].count;
1449		if (buf_num > max_num)
1450			max_num = buf_num;
1451	}
1452
1453	buf_num = ilog2(max_num);
1454	bitlen = ALIGN(buf_num, RADIX_BASE * 2);
1455
1456	shift = 0;
1457	while (shift < bitlen) {
1458		memset(counters, 0, sizeof(counters));
1459
1460		for (i = 0; i < num; i++) {
1461			buf_num = array[i].count;
1462			addr = get4bits(buf_num, shift);
1463			counters[addr]++;
1464		}
1465
1466		for (i = 1; i < COUNTERS_SIZE; i++)
1467			counters[i] += counters[i - 1];
1468
1469		for (i = num - 1; i >= 0; i--) {
1470			buf_num = array[i].count;
1471			addr = get4bits(buf_num, shift);
1472			counters[addr]--;
1473			new_addr = counters[addr];
1474			array_buf[new_addr] = array[i];
1475		}
1476
1477		shift += RADIX_BASE;
1478
1479		/*
1480		 * Normal radix expects to move data from a temporary array, to
1481		 * the main one.  But that requires some CPU time. Avoid that
1482		 * by doing another sort iteration to original array instead of
1483		 * memcpy()
1484		 */
1485		memset(counters, 0, sizeof(counters));
1486
1487		for (i = 0; i < num; i ++) {
1488			buf_num = array_buf[i].count;
1489			addr = get4bits(buf_num, shift);
1490			counters[addr]++;
1491		}
1492
1493		for (i = 1; i < COUNTERS_SIZE; i++)
1494			counters[i] += counters[i - 1];
1495
1496		for (i = num - 1; i >= 0; i--) {
1497			buf_num = array_buf[i].count;
1498			addr = get4bits(buf_num, shift);
1499			counters[addr]--;
1500			new_addr = counters[addr];
1501			array[new_addr] = array_buf[i];
1502		}
1503
1504		shift += RADIX_BASE;
1505	}
1506}
1507
1508/*
1509 * Size of the core byte set - how many bytes cover 90% of the sample
1510 *
1511 * There are several types of structured binary data that use nearly all byte
1512 * values. The distribution can be uniform and counts in all buckets will be
1513 * nearly the same (eg. encrypted data). Unlikely to be compressible.
1514 *
1515 * Other possibility is normal (Gaussian) distribution, where the data could
1516 * be potentially compressible, but we have to take a few more steps to decide
1517 * how much.
1518 *
1519 * @BYTE_CORE_SET_LOW  - main part of byte values repeated frequently,
1520 *                       compression algo can easy fix that
1521 * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high
1522 *                       probability is not compressible
1523 */
1524#define BYTE_CORE_SET_LOW		(64)
1525#define BYTE_CORE_SET_HIGH		(200)
1526
1527static int byte_core_set_size(struct heuristic_ws *ws)
1528{
1529	u32 i;
1530	u32 coreset_sum = 0;
1531	const u32 core_set_threshold = ws->sample_size * 90 / 100;
1532	struct bucket_item *bucket = ws->bucket;
1533
1534	/* Sort in reverse order */
1535	radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE);
1536
1537	for (i = 0; i < BYTE_CORE_SET_LOW; i++)
1538		coreset_sum += bucket[i].count;
1539
1540	if (coreset_sum > core_set_threshold)
1541		return i;
1542
1543	for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) {
1544		coreset_sum += bucket[i].count;
1545		if (coreset_sum > core_set_threshold)
1546			break;
1547	}
1548
1549	return i;
1550}
1551
1552/*
1553 * Count byte values in buckets.
1554 * This heuristic can detect textual data (configs, xml, json, html, etc).
1555 * Because in most text-like data byte set is restricted to limited number of
1556 * possible characters, and that restriction in most cases makes data easy to
1557 * compress.
1558 *
1559 * @BYTE_SET_THRESHOLD - consider all data within this byte set size:
1560 *	less - compressible
1561 *	more - need additional analysis
1562 */
1563#define BYTE_SET_THRESHOLD		(64)
1564
1565static u32 byte_set_size(const struct heuristic_ws *ws)
1566{
1567	u32 i;
1568	u32 byte_set_size = 0;
1569
1570	for (i = 0; i < BYTE_SET_THRESHOLD; i++) {
1571		if (ws->bucket[i].count > 0)
1572			byte_set_size++;
1573	}
1574
1575	/*
1576	 * Continue collecting count of byte values in buckets.  If the byte
1577	 * set size is bigger then the threshold, it's pointless to continue,
1578	 * the detection technique would fail for this type of data.
1579	 */
1580	for (; i < BUCKET_SIZE; i++) {
1581		if (ws->bucket[i].count > 0) {
1582			byte_set_size++;
1583			if (byte_set_size > BYTE_SET_THRESHOLD)
1584				return byte_set_size;
1585		}
1586	}
1587
1588	return byte_set_size;
1589}
1590
1591static bool sample_repeated_patterns(struct heuristic_ws *ws)
1592{
1593	const u32 half_of_sample = ws->sample_size / 2;
1594	const u8 *data = ws->sample;
1595
1596	return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0;
1597}
1598
1599static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end,
1600				     struct heuristic_ws *ws)
1601{
1602	struct page *page;
1603	u64 index, index_end;
1604	u32 i, curr_sample_pos;
1605	u8 *in_data;
1606
1607	/*
1608	 * Compression handles the input data by chunks of 128KiB
1609	 * (defined by BTRFS_MAX_UNCOMPRESSED)
1610	 *
1611	 * We do the same for the heuristic and loop over the whole range.
1612	 *
1613	 * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will
1614	 * process no more than BTRFS_MAX_UNCOMPRESSED at a time.
1615	 */
1616	if (end - start > BTRFS_MAX_UNCOMPRESSED)
1617		end = start + BTRFS_MAX_UNCOMPRESSED;
1618
1619	index = start >> PAGE_SHIFT;
1620	index_end = end >> PAGE_SHIFT;
1621
1622	/* Don't miss unaligned end */
1623	if (!IS_ALIGNED(end, PAGE_SIZE))
1624		index_end++;
1625
1626	curr_sample_pos = 0;
1627	while (index < index_end) {
1628		page = find_get_page(inode->i_mapping, index);
1629		in_data = kmap(page);
1630		/* Handle case where the start is not aligned to PAGE_SIZE */
1631		i = start % PAGE_SIZE;
1632		while (i < PAGE_SIZE - SAMPLING_READ_SIZE) {
1633			/* Don't sample any garbage from the last page */
1634			if (start > end - SAMPLING_READ_SIZE)
1635				break;
1636			memcpy(&ws->sample[curr_sample_pos], &in_data[i],
1637					SAMPLING_READ_SIZE);
1638			i += SAMPLING_INTERVAL;
1639			start += SAMPLING_INTERVAL;
1640			curr_sample_pos += SAMPLING_READ_SIZE;
1641		}
1642		kunmap(page);
1643		put_page(page);
1644
1645		index++;
1646	}
1647
1648	ws->sample_size = curr_sample_pos;
1649}
1650
1651/*
1652 * Compression heuristic.
1653 *
1654 * For now is's a naive and optimistic 'return true', we'll extend the logic to
1655 * quickly (compared to direct compression) detect data characteristics
1656 * (compressible/uncompressible) to avoid wasting CPU time on uncompressible
1657 * data.
1658 *
1659 * The following types of analysis can be performed:
1660 * - detect mostly zero data
1661 * - detect data with low "byte set" size (text, etc)
1662 * - detect data with low/high "core byte" set
1663 *
1664 * Return non-zero if the compression should be done, 0 otherwise.
1665 */
1666int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
1667{
1668	struct list_head *ws_list = get_workspace(0, 0);
1669	struct heuristic_ws *ws;
1670	u32 i;
1671	u8 byte;
1672	int ret = 0;
1673
1674	ws = list_entry(ws_list, struct heuristic_ws, list);
1675
1676	heuristic_collect_sample(inode, start, end, ws);
1677
1678	if (sample_repeated_patterns(ws)) {
1679		ret = 1;
1680		goto out;
1681	}
1682
1683	memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE);
1684
1685	for (i = 0; i < ws->sample_size; i++) {
1686		byte = ws->sample[i];
1687		ws->bucket[byte].count++;
1688	}
1689
1690	i = byte_set_size(ws);
1691	if (i < BYTE_SET_THRESHOLD) {
1692		ret = 2;
1693		goto out;
1694	}
1695
1696	i = byte_core_set_size(ws);
1697	if (i <= BYTE_CORE_SET_LOW) {
1698		ret = 3;
1699		goto out;
1700	}
1701
1702	if (i >= BYTE_CORE_SET_HIGH) {
1703		ret = 0;
1704		goto out;
1705	}
1706
1707	i = shannon_entropy(ws);
1708	if (i <= ENTROPY_LVL_ACEPTABLE) {
1709		ret = 4;
1710		goto out;
1711	}
1712
1713	/*
1714	 * For the levels below ENTROPY_LVL_HIGH, additional analysis would be
1715	 * needed to give green light to compression.
1716	 *
1717	 * For now just assume that compression at that level is not worth the
1718	 * resources because:
1719	 *
1720	 * 1. it is possible to defrag the data later
1721	 *
1722	 * 2. the data would turn out to be hardly compressible, eg. 150 byte
1723	 * values, every bucket has counter at level ~54. The heuristic would
1724	 * be confused. This can happen when data have some internal repeated
1725	 * patterns like "abbacbbc...". This can be detected by analyzing
1726	 * pairs of bytes, which is too costly.
1727	 */
1728	if (i < ENTROPY_LVL_HIGH) {
1729		ret = 5;
1730		goto out;
1731	} else {
1732		ret = 0;
1733		goto out;
1734	}
1735
1736out:
1737	put_workspace(0, ws_list);
1738	return ret;
1739}
1740
1741/*
1742 * Convert the compression suffix (eg. after "zlib" starting with ":") to
1743 * level, unrecognized string will set the default level
1744 */
1745unsigned int btrfs_compress_str2level(unsigned int type, const char *str)
1746{
1747	unsigned int level = 0;
1748	int ret;
1749
1750	if (!type)
1751		return 0;
1752
1753	if (str[0] == ':') {
1754		ret = kstrtouint(str + 1, 10, &level);
1755		if (ret)
1756			level = 0;
1757	}
1758
1759	level = btrfs_compress_set_level(type, level);
1760
1761	return level;
1762}