// SPDX-License-Identifier: GPL-2.0 /* * Copyright (C) 2008 Oracle. All rights reserved. */ #include <linux/kernel.h> #include <linux/bio.h> #include <linux/file.h> #include <linux/fs.h> #include <linux/pagemap.h> #include <linux/highmem.h> #include <linux/time.h> #include <linux/init.h> #include <linux/string.h> #include <linux/backing-dev.h> #include <linux/writeback.h> #include <linux/slab.h> #include <linux/sched/mm.h> #include <linux/log2.h> #include <crypto/hash.h> #include "misc.h" #include "ctree.h" #include "disk-io.h" #include "transaction.h" #include "btrfs_inode.h" #include "volumes.h" #include "ordered-data.h" #include "compression.h" #include "extent_io.h" #include "extent_map.h" int zlib_compress_pages(struct list_head *ws, struct address_space *mapping, u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out); int zlib_decompress_bio(struct list_head *ws, struct compressed_bio *cb); int zlib_decompress(struct list_head *ws, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen); struct list_head *zlib_alloc_workspace(unsigned int level); void zlib_free_workspace(struct list_head *ws); struct list_head *zlib_get_workspace(unsigned int level); int lzo_compress_pages(struct list_head *ws, struct address_space *mapping, u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out); int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb); int lzo_decompress(struct list_head *ws, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen); struct list_head *lzo_alloc_workspace(unsigned int level); void lzo_free_workspace(struct list_head *ws); int zstd_compress_pages(struct list_head *ws, struct address_space *mapping, u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out); int zstd_decompress_bio(struct list_head *ws, struct compressed_bio *cb); int zstd_decompress(struct list_head *ws, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen); void zstd_init_workspace_manager(void); void zstd_cleanup_workspace_manager(void); struct list_head *zstd_alloc_workspace(unsigned int level); void zstd_free_workspace(struct list_head *ws); struct list_head *zstd_get_workspace(unsigned int level); void zstd_put_workspace(struct list_head *ws); static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" }; const char* btrfs_compress_type2str(enum btrfs_compression_type type) { switch (type) { case BTRFS_COMPRESS_ZLIB: case BTRFS_COMPRESS_LZO: case BTRFS_COMPRESS_ZSTD: case BTRFS_COMPRESS_NONE: return btrfs_compress_types[type]; default: break; } return NULL; } bool btrfs_compress_is_valid_type(const char *str, size_t len) { int i; for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) { size_t comp_len = strlen(btrfs_compress_types[i]); if (len < comp_len) continue; if (!strncmp(btrfs_compress_types[i], str, comp_len)) return true; } return false; } static int compression_compress_pages(int type, struct list_head *ws, struct address_space *mapping, u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out) { switch (type) { case BTRFS_COMPRESS_ZLIB: return zlib_compress_pages(ws, mapping, start, pages, out_pages, total_in, total_out); case BTRFS_COMPRESS_LZO: return lzo_compress_pages(ws, mapping, start, pages, out_pages, total_in, total_out); case BTRFS_COMPRESS_ZSTD: return zstd_compress_pages(ws, mapping, start, pages, out_pages, total_in, total_out); case BTRFS_COMPRESS_NONE: default: /* * This can't happen, the type is validated several times * before we get here. As a sane fallback, return what the * callers will understand as 'no compression happened'. */ return -E2BIG; } } static int compression_decompress_bio(int type, struct list_head *ws, struct compressed_bio *cb) { switch (type) { case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb); case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb); case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb); case BTRFS_COMPRESS_NONE: default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } static int compression_decompress(int type, struct list_head *ws, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen) { switch (type) { case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page, start_byte, srclen, destlen); case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page, start_byte, srclen, destlen); case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page, start_byte, srclen, destlen); case BTRFS_COMPRESS_NONE: default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } static int btrfs_decompress_bio(struct compressed_bio *cb); static inline int compressed_bio_size(struct btrfs_fs_info *fs_info, unsigned long disk_size) { u16 csum_size = btrfs_super_csum_size(fs_info->super_copy); return sizeof(struct compressed_bio) + (DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size; } static int check_compressed_csum(struct btrfs_inode *inode, struct compressed_bio *cb, u64 disk_start) { struct btrfs_fs_info *fs_info = inode->root->fs_info; SHASH_DESC_ON_STACK(shash, fs_info->csum_shash); const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy); int ret; struct page *page; unsigned long i; char *kaddr; u8 csum[BTRFS_CSUM_SIZE]; u8 *cb_sum = cb->sums; if (inode->flags & BTRFS_INODE_NODATASUM) return 0; shash->tfm = fs_info->csum_shash; for (i = 0; i < cb->nr_pages; i++) { page = cb->compressed_pages[i]; crypto_shash_init(shash); kaddr = kmap_atomic(page); crypto_shash_update(shash, kaddr, PAGE_SIZE); kunmap_atomic(kaddr); crypto_shash_final(shash, (u8 *)&csum); if (memcmp(&csum, cb_sum, csum_size)) { btrfs_print_data_csum_error(inode, disk_start, csum, cb_sum, cb->mirror_num); ret = -EIO; goto fail; } cb_sum += csum_size; } ret = 0; fail: return ret; } /* when we finish reading compressed pages from the disk, we * decompress them and then run the bio end_io routines on the * decompressed pages (in the inode address space). * * This allows the checksumming and other IO error handling routines * to work normally * * The compressed pages are freed here, and it must be run * in process context */ static void end_compressed_bio_read(struct bio *bio) { struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; unsigned int mirror = btrfs_io_bio(bio)->mirror_num; int ret = 0; if (bio->bi_status) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!refcount_dec_and_test(&cb->pending_bios)) goto out; /* * Record the correct mirror_num in cb->orig_bio so that * read-repair can work properly. */ ASSERT(btrfs_io_bio(cb->orig_bio)); btrfs_io_bio(cb->orig_bio)->mirror_num = mirror; cb->mirror_num = mirror; /* * Some IO in this cb have failed, just skip checksum as there * is no way it could be correct. */ if (cb->errors == 1) goto csum_failed; inode = cb->inode; ret = check_compressed_csum(BTRFS_I(inode), cb, (u64)bio->bi_iter.bi_sector << 9); if (ret) goto csum_failed; /* ok, we're the last bio for this extent, lets start * the decompression. */ ret = btrfs_decompress_bio(cb); csum_failed: if (ret) cb->errors = 1; /* release the compressed pages */ index = 0; for (index = 0; index < cb->nr_pages; index++) { page = cb->compressed_pages[index]; page->mapping = NULL; put_page(page); } /* do io completion on the original bio */ if (cb->errors) { bio_io_error(cb->orig_bio); } else { struct bio_vec *bvec; struct bvec_iter_all iter_all; /* * we have verified the checksum already, set page * checked so the end_io handlers know about it */ ASSERT(!bio_flagged(bio, BIO_CLONED)); bio_for_each_segment_all(bvec, cb->orig_bio, iter_all) SetPageChecked(bvec->bv_page); bio_endio(cb->orig_bio); } /* finally free the cb struct */ kfree(cb->compressed_pages); kfree(cb); out: bio_put(bio); } /* * Clear the writeback bits on all of the file * pages for a compressed write */ static noinline void end_compressed_writeback(struct inode *inode, const struct compressed_bio *cb) { unsigned long index = cb->start >> PAGE_SHIFT; unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT; struct page *pages[16]; unsigned long nr_pages = end_index - index + 1; int i; int ret; if (cb->errors) mapping_set_error(inode->i_mapping, -EIO); while (nr_pages > 0) { ret = find_get_pages_contig(inode->i_mapping, index, min_t(unsigned long, nr_pages, ARRAY_SIZE(pages)), pages); if (ret == 0) { nr_pages -= 1; index += 1; continue; } for (i = 0; i < ret; i++) { if (cb->errors) SetPageError(pages[i]); end_page_writeback(pages[i]); put_page(pages[i]); } nr_pages -= ret; index += ret; } /* the inode may be gone now */ } /* * do the cleanup once all the compressed pages hit the disk. * This will clear writeback on the file pages and free the compressed * pages. * * This also calls the writeback end hooks for the file pages so that * metadata and checksums can be updated in the file. */ static void end_compressed_bio_write(struct bio *bio) { struct compressed_bio *cb = bio->bi_private; struct inode *inode; struct page *page; unsigned long index; if (bio->bi_status) cb->errors = 1; /* if there are more bios still pending for this compressed * extent, just exit */ if (!refcount_dec_and_test(&cb->pending_bios)) goto out; /* ok, we're the last bio for this extent, step one is to * call back into the FS and do all the end_io operations */ inode = cb->inode; cb->compressed_pages[0]->mapping = cb->inode->i_mapping; btrfs_writepage_endio_finish_ordered(cb->compressed_pages[0], cb->start, cb->start + cb->len - 1, bio->bi_status == BLK_STS_OK); cb->compressed_pages[0]->mapping = NULL; end_compressed_writeback(inode, cb); /* note, our inode could be gone now */ /* * release the compressed pages, these came from alloc_page and * are not attached to the inode at all */ index = 0; for (index = 0; index < cb->nr_pages; index++) { page = cb->compressed_pages[index]; page->mapping = NULL; put_page(page); } /* finally free the cb struct */ kfree(cb->compressed_pages); kfree(cb); out: bio_put(bio); } /* * worker function to build and submit bios for previously compressed pages. * The corresponding pages in the inode should be marked for writeback * and the compressed pages should have a reference on them for dropping * when the IO is complete. * * This also checksums the file bytes and gets things ready for * the end io hooks. */ blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start, unsigned long len, u64 disk_start, unsigned long compressed_len, struct page **compressed_pages, unsigned long nr_pages, unsigned int write_flags, struct cgroup_subsys_state *blkcg_css) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct bio *bio = NULL; struct compressed_bio *cb; unsigned long bytes_left; int pg_index = 0; struct page *page; u64 first_byte = disk_start; blk_status_t ret; int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM; WARN_ON(!PAGE_ALIGNED(start)); cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS); if (!cb) return BLK_STS_RESOURCE; refcount_set(&cb->pending_bios, 0); cb->errors = 0; cb->inode = inode; cb->start = start; cb->len = len; cb->mirror_num = 0; cb->compressed_pages = compressed_pages; cb->compressed_len = compressed_len; cb->orig_bio = NULL; cb->nr_pages = nr_pages; bio = btrfs_bio_alloc(first_byte); bio->bi_opf = REQ_OP_WRITE | write_flags; bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; if (blkcg_css) { bio->bi_opf |= REQ_CGROUP_PUNT; bio_associate_blkg_from_css(bio, blkcg_css); } refcount_set(&cb->pending_bios, 1); /* create and submit bios for the compressed pages */ bytes_left = compressed_len; for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) { int submit = 0; page = compressed_pages[pg_index]; page->mapping = inode->i_mapping; if (bio->bi_iter.bi_size) submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio, 0); page->mapping = NULL; if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) { /* * inc the count before we submit the bio so * we know the end IO handler won't happen before * we inc the count. Otherwise, the cb might get * freed before we're done setting it up */ refcount_inc(&cb->pending_bios); ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!skip_sum) { ret = btrfs_csum_one_bio(inode, bio, start, 1); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, bio, 0); if (ret) { bio->bi_status = ret; bio_endio(bio); } bio = btrfs_bio_alloc(first_byte); bio->bi_opf = REQ_OP_WRITE | write_flags; bio->bi_private = cb; bio->bi_end_io = end_compressed_bio_write; bio_add_page(bio, page, PAGE_SIZE, 0); } if (bytes_left < PAGE_SIZE) { btrfs_info(fs_info, "bytes left %lu compress len %lu nr %lu", bytes_left, cb->compressed_len, cb->nr_pages); } bytes_left -= PAGE_SIZE; first_byte += PAGE_SIZE; cond_resched(); } ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!skip_sum) { ret = btrfs_csum_one_bio(inode, bio, start, 1); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, bio, 0); if (ret) { bio->bi_status = ret; bio_endio(bio); } return 0; } static u64 bio_end_offset(struct bio *bio) { struct bio_vec *last = bio_last_bvec_all(bio); return page_offset(last->bv_page) + last->bv_len + last->bv_offset; } static noinline int add_ra_bio_pages(struct inode *inode, u64 compressed_end, struct compressed_bio *cb) { unsigned long end_index; unsigned long pg_index; u64 last_offset; u64 isize = i_size_read(inode); int ret; struct page *page; unsigned long nr_pages = 0; struct extent_map *em; struct address_space *mapping = inode->i_mapping; struct extent_map_tree *em_tree; struct extent_io_tree *tree; u64 end; int misses = 0; last_offset = bio_end_offset(cb->orig_bio); em_tree = &BTRFS_I(inode)->extent_tree; tree = &BTRFS_I(inode)->io_tree; if (isize == 0) return 0; end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT; while (last_offset < compressed_end) { pg_index = last_offset >> PAGE_SHIFT; if (pg_index > end_index) break; page = xa_load(&mapping->i_pages, pg_index); if (page && !xa_is_value(page)) { misses++; if (misses > 4) break; goto next; } page = __page_cache_alloc(mapping_gfp_constraint(mapping, ~__GFP_FS)); if (!page) break; if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) { put_page(page); goto next; } end = last_offset + PAGE_SIZE - 1; /* * at this point, we have a locked page in the page cache * for these bytes in the file. But, we have to make * sure they map to this compressed extent on disk. */ set_page_extent_mapped(page); lock_extent(tree, last_offset, end); read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, last_offset, PAGE_SIZE); read_unlock(&em_tree->lock); if (!em || last_offset < em->start || (last_offset + PAGE_SIZE > extent_map_end(em)) || (em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) { free_extent_map(em); unlock_extent(tree, last_offset, end); unlock_page(page); put_page(page); break; } free_extent_map(em); if (page->index == end_index) { char *userpage; size_t zero_offset = offset_in_page(isize); if (zero_offset) { int zeros; zeros = PAGE_SIZE - zero_offset; userpage = kmap_atomic(page); memset(userpage + zero_offset, 0, zeros); flush_dcache_page(page); kunmap_atomic(userpage); } } ret = bio_add_page(cb->orig_bio, page, PAGE_SIZE, 0); if (ret == PAGE_SIZE) { nr_pages++; put_page(page); } else { unlock_extent(tree, last_offset, end); unlock_page(page); put_page(page); break; } next: last_offset += PAGE_SIZE; } return 0; } /* * for a compressed read, the bio we get passed has all the inode pages * in it. We don't actually do IO on those pages but allocate new ones * to hold the compressed pages on disk. * * bio->bi_iter.bi_sector points to the compressed extent on disk * bio->bi_io_vec points to all of the inode pages * * After the compressed pages are read, we copy the bytes into the * bio we were passed and then call the bio end_io calls */ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio, int mirror_num, unsigned long bio_flags) { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); struct extent_map_tree *em_tree; struct compressed_bio *cb; unsigned long compressed_len; unsigned long nr_pages; unsigned long pg_index; struct page *page; struct bio *comp_bio; u64 cur_disk_byte = (u64)bio->bi_iter.bi_sector << 9; u64 em_len; u64 em_start; struct extent_map *em; blk_status_t ret = BLK_STS_RESOURCE; int faili = 0; const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy); u8 *sums; em_tree = &BTRFS_I(inode)->extent_tree; /* we need the actual starting offset of this extent in the file */ read_lock(&em_tree->lock); em = lookup_extent_mapping(em_tree, page_offset(bio_first_page_all(bio)), PAGE_SIZE); read_unlock(&em_tree->lock); if (!em) return BLK_STS_IOERR; compressed_len = em->block_len; cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS); if (!cb) goto out; refcount_set(&cb->pending_bios, 0); cb->errors = 0; cb->inode = inode; cb->mirror_num = mirror_num; sums = cb->sums; cb->start = em->orig_start; em_len = em->len; em_start = em->start; free_extent_map(em); em = NULL; cb->len = bio->bi_iter.bi_size; cb->compressed_len = compressed_len; cb->compress_type = extent_compress_type(bio_flags); cb->orig_bio = bio; nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE); cb->compressed_pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); if (!cb->compressed_pages) goto fail1; for (pg_index = 0; pg_index < nr_pages; pg_index++) { cb->compressed_pages[pg_index] = alloc_page(GFP_NOFS | __GFP_HIGHMEM); if (!cb->compressed_pages[pg_index]) { faili = pg_index - 1; ret = BLK_STS_RESOURCE; goto fail2; } } faili = nr_pages - 1; cb->nr_pages = nr_pages; add_ra_bio_pages(inode, em_start + em_len, cb); /* include any pages we added in add_ra-bio_pages */ cb->len = bio->bi_iter.bi_size; comp_bio = btrfs_bio_alloc(cur_disk_byte); comp_bio->bi_opf = REQ_OP_READ; comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; refcount_set(&cb->pending_bios, 1); for (pg_index = 0; pg_index < nr_pages; pg_index++) { int submit = 0; page = cb->compressed_pages[pg_index]; page->mapping = inode->i_mapping; page->index = em_start >> PAGE_SHIFT; if (comp_bio->bi_iter.bi_size) submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, comp_bio, 0); page->mapping = NULL; if (submit || bio_add_page(comp_bio, page, PAGE_SIZE, 0) < PAGE_SIZE) { unsigned int nr_sectors; ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ /* * inc the count before we submit the bio so * we know the end IO handler won't happen before * we inc the count. Otherwise, the cb might get * freed before we're done setting it up */ refcount_inc(&cb->pending_bios); if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(inode, comp_bio, sums); BUG_ON(ret); /* -ENOMEM */ } nr_sectors = DIV_ROUND_UP(comp_bio->bi_iter.bi_size, fs_info->sectorsize); sums += csum_size * nr_sectors; ret = btrfs_map_bio(fs_info, comp_bio, mirror_num); if (ret) { comp_bio->bi_status = ret; bio_endio(comp_bio); } comp_bio = btrfs_bio_alloc(cur_disk_byte); comp_bio->bi_opf = REQ_OP_READ; comp_bio->bi_private = cb; comp_bio->bi_end_io = end_compressed_bio_read; bio_add_page(comp_bio, page, PAGE_SIZE, 0); } cur_disk_byte += PAGE_SIZE; } ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA); BUG_ON(ret); /* -ENOMEM */ if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) { ret = btrfs_lookup_bio_sums(inode, comp_bio, sums); BUG_ON(ret); /* -ENOMEM */ } ret = btrfs_map_bio(fs_info, comp_bio, mirror_num); if (ret) { comp_bio->bi_status = ret; bio_endio(comp_bio); } return 0; fail2: while (faili >= 0) { __free_page(cb->compressed_pages[faili]); faili--; } kfree(cb->compressed_pages); fail1: kfree(cb); out: free_extent_map(em); return ret; } /* * Heuristic uses systematic sampling to collect data from the input data * range, the logic can be tuned by the following constants: * * @SAMPLING_READ_SIZE - how many bytes will be copied from for each sample * @SAMPLING_INTERVAL - range from which the sampled data can be collected */ #define SAMPLING_READ_SIZE (16) #define SAMPLING_INTERVAL (256) /* * For statistical analysis of the input data we consider bytes that form a * Galois Field of 256 objects. Each object has an attribute count, ie. how * many times the object appeared in the sample. */ #define BUCKET_SIZE (256) /* * The size of the sample is based on a statistical sampling rule of thumb. * The common way is to perform sampling tests as long as the number of * elements in each cell is at least 5. * * Instead of 5, we choose 32 to obtain more accurate results. * If the data contain the maximum number of symbols, which is 256, we obtain a * sample size bound by 8192. * * For a sample of at most 8KB of data per data range: 16 consecutive bytes * from up to 512 locations. */ #define MAX_SAMPLE_SIZE (BTRFS_MAX_UNCOMPRESSED * \ SAMPLING_READ_SIZE / SAMPLING_INTERVAL) struct bucket_item { u32 count; }; struct heuristic_ws { /* Partial copy of input data */ u8 *sample; u32 sample_size; /* Buckets store counters for each byte value */ struct bucket_item *bucket; /* Sorting buffer */ struct bucket_item *bucket_b; struct list_head list; }; static struct workspace_manager heuristic_wsm; static void free_heuristic_ws(struct list_head *ws) { struct heuristic_ws *workspace; workspace = list_entry(ws, struct heuristic_ws, list); kvfree(workspace->sample); kfree(workspace->bucket); kfree(workspace->bucket_b); kfree(workspace); } static struct list_head *alloc_heuristic_ws(unsigned int level) { struct heuristic_ws *ws; ws = kzalloc(sizeof(*ws), GFP_KERNEL); if (!ws) return ERR_PTR(-ENOMEM); ws->sample = kvmalloc(MAX_SAMPLE_SIZE, GFP_KERNEL); if (!ws->sample) goto fail; ws->bucket = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket), GFP_KERNEL); if (!ws->bucket) goto fail; ws->bucket_b = kcalloc(BUCKET_SIZE, sizeof(*ws->bucket_b), GFP_KERNEL); if (!ws->bucket_b) goto fail; INIT_LIST_HEAD(&ws->list); return &ws->list; fail: free_heuristic_ws(&ws->list); return ERR_PTR(-ENOMEM); } const struct btrfs_compress_op btrfs_heuristic_compress = { .workspace_manager = &heuristic_wsm, }; static const struct btrfs_compress_op * const btrfs_compress_op[] = { /* The heuristic is represented as compression type 0 */ &btrfs_heuristic_compress, &btrfs_zlib_compress, &btrfs_lzo_compress, &btrfs_zstd_compress, }; static struct list_head *alloc_workspace(int type, unsigned int level) { switch (type) { case BTRFS_COMPRESS_NONE: return alloc_heuristic_ws(level); case BTRFS_COMPRESS_ZLIB: return zlib_alloc_workspace(level); case BTRFS_COMPRESS_LZO: return lzo_alloc_workspace(level); case BTRFS_COMPRESS_ZSTD: return zstd_alloc_workspace(level); default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } static void free_workspace(int type, struct list_head *ws) { switch (type) { case BTRFS_COMPRESS_NONE: return free_heuristic_ws(ws); case BTRFS_COMPRESS_ZLIB: return zlib_free_workspace(ws); case BTRFS_COMPRESS_LZO: return lzo_free_workspace(ws); case BTRFS_COMPRESS_ZSTD: return zstd_free_workspace(ws); default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } static void btrfs_init_workspace_manager(int type) { struct workspace_manager *wsm; struct list_head *workspace; wsm = btrfs_compress_op[type]->workspace_manager; INIT_LIST_HEAD(&wsm->idle_ws); spin_lock_init(&wsm->ws_lock); atomic_set(&wsm->total_ws, 0); init_waitqueue_head(&wsm->ws_wait); /* * Preallocate one workspace for each compression type so we can * guarantee forward progress in the worst case */ workspace = alloc_workspace(type, 0); if (IS_ERR(workspace)) { pr_warn( "BTRFS: cannot preallocate compression workspace, will try later\n"); } else { atomic_set(&wsm->total_ws, 1); wsm->free_ws = 1; list_add(workspace, &wsm->idle_ws); } } static void btrfs_cleanup_workspace_manager(int type) { struct workspace_manager *wsman; struct list_head *ws; wsman = btrfs_compress_op[type]->workspace_manager; while (!list_empty(&wsman->idle_ws)) { ws = wsman->idle_ws.next; list_del(ws); free_workspace(type, ws); atomic_dec(&wsman->total_ws); } } /* * This finds an available workspace or allocates a new one. * If it's not possible to allocate a new one, waits until there's one. * Preallocation makes a forward progress guarantees and we do not return * errors. */ struct list_head *btrfs_get_workspace(int type, unsigned int level) { struct workspace_manager *wsm; struct list_head *workspace; int cpus = num_online_cpus(); unsigned nofs_flag; struct list_head *idle_ws; spinlock_t *ws_lock; atomic_t *total_ws; wait_queue_head_t *ws_wait; int *free_ws; wsm = btrfs_compress_op[type]->workspace_manager; idle_ws = &wsm->idle_ws; ws_lock = &wsm->ws_lock; total_ws = &wsm->total_ws; ws_wait = &wsm->ws_wait; free_ws = &wsm->free_ws; again: spin_lock(ws_lock); if (!list_empty(idle_ws)) { workspace = idle_ws->next; list_del(workspace); (*free_ws)--; spin_unlock(ws_lock); return workspace; } if (atomic_read(total_ws) > cpus) { DEFINE_WAIT(wait); spin_unlock(ws_lock); prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE); if (atomic_read(total_ws) > cpus && !*free_ws) schedule(); finish_wait(ws_wait, &wait); goto again; } atomic_inc(total_ws); spin_unlock(ws_lock); /* * Allocation helpers call vmalloc that can't use GFP_NOFS, so we have * to turn it off here because we might get called from the restricted * context of btrfs_compress_bio/btrfs_compress_pages */ nofs_flag = memalloc_nofs_save(); workspace = alloc_workspace(type, level); memalloc_nofs_restore(nofs_flag); if (IS_ERR(workspace)) { atomic_dec(total_ws); wake_up(ws_wait); /* * Do not return the error but go back to waiting. There's a * workspace preallocated for each type and the compression * time is bounded so we get to a workspace eventually. This * makes our caller's life easier. * * To prevent silent and low-probability deadlocks (when the * initial preallocation fails), check if there are any * workspaces at all. */ if (atomic_read(total_ws) == 0) { static DEFINE_RATELIMIT_STATE(_rs, /* once per minute */ 60 * HZ, /* no burst */ 1); if (__ratelimit(&_rs)) { pr_warn("BTRFS: no compression workspaces, low memory, retrying\n"); } } goto again; } return workspace; } static struct list_head *get_workspace(int type, int level) { switch (type) { case BTRFS_COMPRESS_NONE: return btrfs_get_workspace(type, level); case BTRFS_COMPRESS_ZLIB: return zlib_get_workspace(level); case BTRFS_COMPRESS_LZO: return btrfs_get_workspace(type, level); case BTRFS_COMPRESS_ZSTD: return zstd_get_workspace(level); default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } /* * put a workspace struct back on the list or free it if we have enough * idle ones sitting around */ void btrfs_put_workspace(int type, struct list_head *ws) { struct workspace_manager *wsm; struct list_head *idle_ws; spinlock_t *ws_lock; atomic_t *total_ws; wait_queue_head_t *ws_wait; int *free_ws; wsm = btrfs_compress_op[type]->workspace_manager; idle_ws = &wsm->idle_ws; ws_lock = &wsm->ws_lock; total_ws = &wsm->total_ws; ws_wait = &wsm->ws_wait; free_ws = &wsm->free_ws; spin_lock(ws_lock); if (*free_ws <= num_online_cpus()) { list_add(ws, idle_ws); (*free_ws)++; spin_unlock(ws_lock); goto wake; } spin_unlock(ws_lock); free_workspace(type, ws); atomic_dec(total_ws); wake: cond_wake_up(ws_wait); } static void put_workspace(int type, struct list_head *ws) { switch (type) { case BTRFS_COMPRESS_NONE: return btrfs_put_workspace(type, ws); case BTRFS_COMPRESS_ZLIB: return btrfs_put_workspace(type, ws); case BTRFS_COMPRESS_LZO: return btrfs_put_workspace(type, ws); case BTRFS_COMPRESS_ZSTD: return zstd_put_workspace(ws); default: /* * This can't happen, the type is validated several times * before we get here. */ BUG(); } } /* * Given an address space and start and length, compress the bytes into @pages * that are allocated on demand. * * @type_level is encoded algorithm and level, where level 0 means whatever * default the algorithm chooses and is opaque here; * - compression algo are 0-3 * - the level are bits 4-7 * * @out_pages is an in/out parameter, holds maximum number of pages to allocate * and returns number of actually allocated pages * * @total_in is used to return the number of bytes actually read. It * may be smaller than the input length if we had to exit early because we * ran out of room in the pages array or because we cross the * max_out threshold. * * @total_out is an in/out parameter, must be set to the input length and will * be also used to return the total number of compressed bytes * * @max_out tells us the max number of bytes that we're allowed to * stuff into pages */ int btrfs_compress_pages(unsigned int type_level, struct address_space *mapping, u64 start, struct page **pages, unsigned long *out_pages, unsigned long *total_in, unsigned long *total_out) { int type = btrfs_compress_type(type_level); int level = btrfs_compress_level(type_level); struct list_head *workspace; int ret; level = btrfs_compress_set_level(type, level); workspace = get_workspace(type, level); ret = compression_compress_pages(type, workspace, mapping, start, pages, out_pages, total_in, total_out); put_workspace(type, workspace); return ret; } /* * pages_in is an array of pages with compressed data. * * disk_start is the starting logical offset of this array in the file * * orig_bio contains the pages from the file that we want to decompress into * * srclen is the number of bytes in pages_in * * The basic idea is that we have a bio that was created by readpages. * The pages in the bio are for the uncompressed data, and they may not * be contiguous. They all correspond to the range of bytes covered by * the compressed extent. */ static int btrfs_decompress_bio(struct compressed_bio *cb) { struct list_head *workspace; int ret; int type = cb->compress_type; workspace = get_workspace(type, 0); ret = compression_decompress_bio(type, workspace, cb); put_workspace(type, workspace); return ret; } /* * a less complex decompression routine. Our compressed data fits in a * single page, and we want to read a single page out of it. * start_byte tells us the offset into the compressed data we're interested in */ int btrfs_decompress(int type, unsigned char *data_in, struct page *dest_page, unsigned long start_byte, size_t srclen, size_t destlen) { struct list_head *workspace; int ret; workspace = get_workspace(type, 0); ret = compression_decompress(type, workspace, data_in, dest_page, start_byte, srclen, destlen); put_workspace(type, workspace); return ret; } void __init btrfs_init_compress(void) { btrfs_init_workspace_manager(BTRFS_COMPRESS_NONE); btrfs_init_workspace_manager(BTRFS_COMPRESS_ZLIB); btrfs_init_workspace_manager(BTRFS_COMPRESS_LZO); zstd_init_workspace_manager(); } void __cold btrfs_exit_compress(void) { btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_NONE); btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_ZLIB); btrfs_cleanup_workspace_manager(BTRFS_COMPRESS_LZO); zstd_cleanup_workspace_manager(); } /* * Copy uncompressed data from working buffer to pages. * * buf_start is the byte offset we're of the start of our workspace buffer. * * total_out is the last byte of the buffer */ int btrfs_decompress_buf2page(const char *buf, unsigned long buf_start, unsigned long total_out, u64 disk_start, struct bio *bio) { unsigned long buf_offset; unsigned long current_buf_start; unsigned long start_byte; unsigned long prev_start_byte; unsigned long working_bytes = total_out - buf_start; unsigned long bytes; char *kaddr; struct bio_vec bvec = bio_iter_iovec(bio, bio->bi_iter); /* * start byte is the first byte of the page we're currently * copying into relative to the start of the compressed data. */ start_byte = page_offset(bvec.bv_page) - disk_start; /* we haven't yet hit data corresponding to this page */ if (total_out <= start_byte) return 1; /* * the start of the data we care about is offset into * the middle of our working buffer */ if (total_out > start_byte && buf_start < start_byte) { buf_offset = start_byte - buf_start; working_bytes -= buf_offset; } else { buf_offset = 0; } current_buf_start = buf_start; /* copy bytes from the working buffer into the pages */ while (working_bytes > 0) { bytes = min_t(unsigned long, bvec.bv_len, PAGE_SIZE - buf_offset); bytes = min(bytes, working_bytes); kaddr = kmap_atomic(bvec.bv_page); memcpy(kaddr + bvec.bv_offset, buf + buf_offset, bytes); kunmap_atomic(kaddr); flush_dcache_page(bvec.bv_page); buf_offset += bytes; working_bytes -= bytes; current_buf_start += bytes; /* check if we need to pick another page */ bio_advance(bio, bytes); if (!bio->bi_iter.bi_size) return 0; bvec = bio_iter_iovec(bio, bio->bi_iter); prev_start_byte = start_byte; start_byte = page_offset(bvec.bv_page) - disk_start; /* * We need to make sure we're only adjusting * our offset into compression working buffer when * we're switching pages. Otherwise we can incorrectly * keep copying when we were actually done. */ if (start_byte != prev_start_byte) { /* * make sure our new page is covered by this * working buffer */ if (total_out <= start_byte) return 1; /* * the next page in the biovec might not be adjacent * to the last page, but it might still be found * inside this working buffer. bump our offset pointer */ if (total_out > start_byte && current_buf_start < start_byte) { buf_offset = start_byte - buf_start; working_bytes = total_out - start_byte; current_buf_start = buf_start + buf_offset; } } } return 1; } /* * Shannon Entropy calculation * * Pure byte distribution analysis fails to determine compressibility of data. * Try calculating entropy to estimate the average minimum number of bits * needed to encode the sampled data. * * For convenience, return the percentage of needed bits, instead of amount of * bits directly. * * @ENTROPY_LVL_ACEPTABLE - below that threshold, sample has low byte entropy * and can be compressible with high probability * * @ENTROPY_LVL_HIGH - data are not compressible with high probability * * Use of ilog2() decreases precision, we lower the LVL to 5 to compensate. */ #define ENTROPY_LVL_ACEPTABLE (65) #define ENTROPY_LVL_HIGH (80) /* * For increasead precision in shannon_entropy calculation, * let's do pow(n, M) to save more digits after comma: * * - maximum int bit length is 64 * - ilog2(MAX_SAMPLE_SIZE) -> 13 * - 13 * 4 = 52 < 64 -> M = 4 * * So use pow(n, 4). */ static inline u32 ilog2_w(u64 n) { return ilog2(n * n * n * n); } static u32 shannon_entropy(struct heuristic_ws *ws) { const u32 entropy_max = 8 * ilog2_w(2); u32 entropy_sum = 0; u32 p, p_base, sz_base; u32 i; sz_base = ilog2_w(ws->sample_size); for (i = 0; i < BUCKET_SIZE && ws->bucket[i].count > 0; i++) { p = ws->bucket[i].count; p_base = ilog2_w(p); entropy_sum += p * (sz_base - p_base); } entropy_sum /= ws->sample_size; return entropy_sum * 100 / entropy_max; } #define RADIX_BASE 4U #define COUNTERS_SIZE (1U << RADIX_BASE) static u8 get4bits(u64 num, int shift) { u8 low4bits; num >>= shift; /* Reverse order */ low4bits = (COUNTERS_SIZE - 1) - (num % COUNTERS_SIZE); return low4bits; } /* * Use 4 bits as radix base * Use 16 u32 counters for calculating new position in buf array * * @array - array that will be sorted * @array_buf - buffer array to store sorting results * must be equal in size to @array * @num - array size */ static void radix_sort(struct bucket_item *array, struct bucket_item *array_buf, int num) { u64 max_num; u64 buf_num; u32 counters[COUNTERS_SIZE]; u32 new_addr; u32 addr; int bitlen; int shift; int i; /* * Try avoid useless loop iterations for small numbers stored in big * counters. Example: 48 33 4 ... in 64bit array */ max_num = array[0].count; for (i = 1; i < num; i++) { buf_num = array[i].count; if (buf_num > max_num) max_num = buf_num; } buf_num = ilog2(max_num); bitlen = ALIGN(buf_num, RADIX_BASE * 2); shift = 0; while (shift < bitlen) { memset(counters, 0, sizeof(counters)); for (i = 0; i < num; i++) { buf_num = array[i].count; addr = get4bits(buf_num, shift); counters[addr]++; } for (i = 1; i < COUNTERS_SIZE; i++) counters[i] += counters[i - 1]; for (i = num - 1; i >= 0; i--) { buf_num = array[i].count; addr = get4bits(buf_num, shift); counters[addr]--; new_addr = counters[addr]; array_buf[new_addr] = array[i]; } shift += RADIX_BASE; /* * Normal radix expects to move data from a temporary array, to * the main one. But that requires some CPU time. Avoid that * by doing another sort iteration to original array instead of * memcpy() */ memset(counters, 0, sizeof(counters)); for (i = 0; i < num; i ++) { buf_num = array_buf[i].count; addr = get4bits(buf_num, shift); counters[addr]++; } for (i = 1; i < COUNTERS_SIZE; i++) counters[i] += counters[i - 1]; for (i = num - 1; i >= 0; i--) { buf_num = array_buf[i].count; addr = get4bits(buf_num, shift); counters[addr]--; new_addr = counters[addr]; array[new_addr] = array_buf[i]; } shift += RADIX_BASE; } } /* * Size of the core byte set - how many bytes cover 90% of the sample * * There are several types of structured binary data that use nearly all byte * values. The distribution can be uniform and counts in all buckets will be * nearly the same (eg. encrypted data). Unlikely to be compressible. * * Other possibility is normal (Gaussian) distribution, where the data could * be potentially compressible, but we have to take a few more steps to decide * how much. * * @BYTE_CORE_SET_LOW - main part of byte values repeated frequently, * compression algo can easy fix that * @BYTE_CORE_SET_HIGH - data have uniform distribution and with high * probability is not compressible */ #define BYTE_CORE_SET_LOW (64) #define BYTE_CORE_SET_HIGH (200) static int byte_core_set_size(struct heuristic_ws *ws) { u32 i; u32 coreset_sum = 0; const u32 core_set_threshold = ws->sample_size * 90 / 100; struct bucket_item *bucket = ws->bucket; /* Sort in reverse order */ radix_sort(ws->bucket, ws->bucket_b, BUCKET_SIZE); for (i = 0; i < BYTE_CORE_SET_LOW; i++) coreset_sum += bucket[i].count; if (coreset_sum > core_set_threshold) return i; for (; i < BYTE_CORE_SET_HIGH && bucket[i].count > 0; i++) { coreset_sum += bucket[i].count; if (coreset_sum > core_set_threshold) break; } return i; } /* * Count byte values in buckets. * This heuristic can detect textual data (configs, xml, json, html, etc). * Because in most text-like data byte set is restricted to limited number of * possible characters, and that restriction in most cases makes data easy to * compress. * * @BYTE_SET_THRESHOLD - consider all data within this byte set size: * less - compressible * more - need additional analysis */ #define BYTE_SET_THRESHOLD (64) static u32 byte_set_size(const struct heuristic_ws *ws) { u32 i; u32 byte_set_size = 0; for (i = 0; i < BYTE_SET_THRESHOLD; i++) { if (ws->bucket[i].count > 0) byte_set_size++; } /* * Continue collecting count of byte values in buckets. If the byte * set size is bigger then the threshold, it's pointless to continue, * the detection technique would fail for this type of data. */ for (; i < BUCKET_SIZE; i++) { if (ws->bucket[i].count > 0) { byte_set_size++; if (byte_set_size > BYTE_SET_THRESHOLD) return byte_set_size; } } return byte_set_size; } static bool sample_repeated_patterns(struct heuristic_ws *ws) { const u32 half_of_sample = ws->sample_size / 2; const u8 *data = ws->sample; return memcmp(&data[0], &data[half_of_sample], half_of_sample) == 0; } static void heuristic_collect_sample(struct inode *inode, u64 start, u64 end, struct heuristic_ws *ws) { struct page *page; u64 index, index_end; u32 i, curr_sample_pos; u8 *in_data; /* * Compression handles the input data by chunks of 128KiB * (defined by BTRFS_MAX_UNCOMPRESSED) * * We do the same for the heuristic and loop over the whole range. * * MAX_SAMPLE_SIZE - calculated under assumption that heuristic will * process no more than BTRFS_MAX_UNCOMPRESSED at a time. */ if (end - start > BTRFS_MAX_UNCOMPRESSED) end = start + BTRFS_MAX_UNCOMPRESSED; index = start >> PAGE_SHIFT; index_end = end >> PAGE_SHIFT; /* Don't miss unaligned end */ if (!IS_ALIGNED(end, PAGE_SIZE)) index_end++; curr_sample_pos = 0; while (index < index_end) { page = find_get_page(inode->i_mapping, index); in_data = kmap(page); /* Handle case where the start is not aligned to PAGE_SIZE */ i = start % PAGE_SIZE; while (i < PAGE_SIZE - SAMPLING_READ_SIZE) { /* Don't sample any garbage from the last page */ if (start > end - SAMPLING_READ_SIZE) break; memcpy(&ws->sample[curr_sample_pos], &in_data[i], SAMPLING_READ_SIZE); i += SAMPLING_INTERVAL; start += SAMPLING_INTERVAL; curr_sample_pos += SAMPLING_READ_SIZE; } kunmap(page); put_page(page); index++; } ws->sample_size = curr_sample_pos; } /* * Compression heuristic. * * For now is's a naive and optimistic 'return true', we'll extend the logic to * quickly (compared to direct compression) detect data characteristics * (compressible/uncompressible) to avoid wasting CPU time on uncompressible * data. * * The following types of analysis can be performed: * - detect mostly zero data * - detect data with low "byte set" size (text, etc) * - detect data with low/high "core byte" set * * Return non-zero if the compression should be done, 0 otherwise. */ int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end) { struct list_head *ws_list = get_workspace(0, 0); struct heuristic_ws *ws; u32 i; u8 byte; int ret = 0; ws = list_entry(ws_list, struct heuristic_ws, list); heuristic_collect_sample(inode, start, end, ws); if (sample_repeated_patterns(ws)) { ret = 1; goto out; } memset(ws->bucket, 0, sizeof(*ws->bucket)*BUCKET_SIZE); for (i = 0; i < ws->sample_size; i++) { byte = ws->sample[i]; ws->bucket[byte].count++; } i = byte_set_size(ws); if (i < BYTE_SET_THRESHOLD) { ret = 2; goto out; } i = byte_core_set_size(ws); if (i <= BYTE_CORE_SET_LOW) { ret = 3; goto out; } if (i >= BYTE_CORE_SET_HIGH) { ret = 0; goto out; } i = shannon_entropy(ws); if (i <= ENTROPY_LVL_ACEPTABLE) { ret = 4; goto out; } /* * For the levels below ENTROPY_LVL_HIGH, additional analysis would be * needed to give green light to compression. * * For now just assume that compression at that level is not worth the * resources because: * * 1. it is possible to defrag the data later * * 2. the data would turn out to be hardly compressible, eg. 150 byte * values, every bucket has counter at level ~54. The heuristic would * be confused. This can happen when data have some internal repeated * patterns like "abbacbbc...". This can be detected by analyzing * pairs of bytes, which is too costly. */ if (i < ENTROPY_LVL_HIGH) { ret = 5; goto out; } else { ret = 0; goto out; } out: put_workspace(0, ws_list); return ret; } /* * Convert the compression suffix (eg. after "zlib" starting with ":") to * level, unrecognized string will set the default level */ unsigned int btrfs_compress_str2level(unsigned int type, const char *str) { unsigned int level = 0; int ret; if (!type) return 0; if (str[0] == ':') { ret = kstrtouint(str + 1, 10, &level); if (ret) level = 0; } level = btrfs_compress_set_level(type, level); return level; } /* * Adjust @level according to the limits of the compression algorithm or * fallback to default */ unsigned int btrfs_compress_set_level(int type, unsigned level) { const struct btrfs_compress_op *ops = btrfs_compress_op[type]; if (level == 0) level = ops->default_level; else level = min(level, ops->max_level); return level; }