![Johannes Thumshirn](/assets/img/avatar_default.png)
BTRFS has the implicit assumption that a checksum in compressed_bio is 4 bytes. While this is true for CRC32C, it is not for any other checksum. Change the data type to be a byte array and adjust loop index calculation accordingly. Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de> Reviewed-by: David Sterba <dsterba@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
1594 lines
40 KiB
C
1594 lines
40 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright (C) 2008 Oracle. All rights reserved.
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*/
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#include <linux/kernel.h>
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#include <linux/bio.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/pagemap.h>
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#include <linux/highmem.h>
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#include <linux/time.h>
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#include <linux/init.h>
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#include <linux/string.h>
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#include <linux/backing-dev.h>
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#include <linux/writeback.h>
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#include <linux/slab.h>
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#include <linux/sched/mm.h>
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#include <linux/log2.h>
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#include "ctree.h"
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#include "disk-io.h"
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#include "transaction.h"
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#include "btrfs_inode.h"
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#include "volumes.h"
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#include "ordered-data.h"
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#include "compression.h"
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#include "extent_io.h"
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#include "extent_map.h"
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static const char* const btrfs_compress_types[] = { "", "zlib", "lzo", "zstd" };
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const char* btrfs_compress_type2str(enum btrfs_compression_type type)
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{
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switch (type) {
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case BTRFS_COMPRESS_ZLIB:
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case BTRFS_COMPRESS_LZO:
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case BTRFS_COMPRESS_ZSTD:
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case BTRFS_COMPRESS_NONE:
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return btrfs_compress_types[type];
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}
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return NULL;
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}
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static int btrfs_decompress_bio(struct compressed_bio *cb);
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static inline int compressed_bio_size(struct btrfs_fs_info *fs_info,
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unsigned long disk_size)
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{
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u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
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return sizeof(struct compressed_bio) +
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(DIV_ROUND_UP(disk_size, fs_info->sectorsize)) * csum_size;
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}
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static int check_compressed_csum(struct btrfs_inode *inode,
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struct compressed_bio *cb,
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u64 disk_start)
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{
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struct btrfs_fs_info *fs_info = inode->root->fs_info;
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const u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
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int ret;
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struct page *page;
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unsigned long i;
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char *kaddr;
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u32 csum;
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u8 *cb_sum = cb->sums;
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if (inode->flags & BTRFS_INODE_NODATASUM)
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return 0;
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for (i = 0; i < cb->nr_pages; i++) {
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page = cb->compressed_pages[i];
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csum = ~(u32)0;
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kaddr = kmap_atomic(page);
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csum = btrfs_csum_data(kaddr, csum, PAGE_SIZE);
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btrfs_csum_final(csum, (u8 *)&csum);
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kunmap_atomic(kaddr);
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if (memcmp(&csum, cb_sum, csum_size)) {
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btrfs_print_data_csum_error(inode, disk_start, csum,
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*(u32 *)cb_sum, cb->mirror_num);
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ret = -EIO;
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goto fail;
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}
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cb_sum += csum_size;
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}
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ret = 0;
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fail:
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return ret;
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}
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/* when we finish reading compressed pages from the disk, we
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* decompress them and then run the bio end_io routines on the
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* decompressed pages (in the inode address space).
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*
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* This allows the checksumming and other IO error handling routines
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* to work normally
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*
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* The compressed pages are freed here, and it must be run
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* in process context
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*/
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static void end_compressed_bio_read(struct bio *bio)
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{
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struct compressed_bio *cb = bio->bi_private;
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struct inode *inode;
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struct page *page;
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unsigned long index;
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unsigned int mirror = btrfs_io_bio(bio)->mirror_num;
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int ret = 0;
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if (bio->bi_status)
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cb->errors = 1;
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/* if there are more bios still pending for this compressed
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* extent, just exit
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*/
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if (!refcount_dec_and_test(&cb->pending_bios))
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goto out;
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/*
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* Record the correct mirror_num in cb->orig_bio so that
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* read-repair can work properly.
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*/
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ASSERT(btrfs_io_bio(cb->orig_bio));
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btrfs_io_bio(cb->orig_bio)->mirror_num = mirror;
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cb->mirror_num = mirror;
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/*
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* Some IO in this cb have failed, just skip checksum as there
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* is no way it could be correct.
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*/
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if (cb->errors == 1)
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goto csum_failed;
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inode = cb->inode;
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ret = check_compressed_csum(BTRFS_I(inode), cb,
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(u64)bio->bi_iter.bi_sector << 9);
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if (ret)
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goto csum_failed;
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/* ok, we're the last bio for this extent, lets start
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* the decompression.
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*/
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ret = btrfs_decompress_bio(cb);
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csum_failed:
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if (ret)
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cb->errors = 1;
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/* release the compressed pages */
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index = 0;
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for (index = 0; index < cb->nr_pages; index++) {
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page = cb->compressed_pages[index];
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page->mapping = NULL;
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put_page(page);
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}
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/* do io completion on the original bio */
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if (cb->errors) {
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bio_io_error(cb->orig_bio);
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} else {
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struct bio_vec *bvec;
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struct bvec_iter_all iter_all;
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/*
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* we have verified the checksum already, set page
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* checked so the end_io handlers know about it
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*/
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ASSERT(!bio_flagged(bio, BIO_CLONED));
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bio_for_each_segment_all(bvec, cb->orig_bio, iter_all)
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SetPageChecked(bvec->bv_page);
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bio_endio(cb->orig_bio);
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}
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/* finally free the cb struct */
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kfree(cb->compressed_pages);
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kfree(cb);
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out:
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bio_put(bio);
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}
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/*
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* Clear the writeback bits on all of the file
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* pages for a compressed write
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*/
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static noinline void end_compressed_writeback(struct inode *inode,
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const struct compressed_bio *cb)
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{
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unsigned long index = cb->start >> PAGE_SHIFT;
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unsigned long end_index = (cb->start + cb->len - 1) >> PAGE_SHIFT;
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struct page *pages[16];
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unsigned long nr_pages = end_index - index + 1;
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int i;
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int ret;
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if (cb->errors)
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mapping_set_error(inode->i_mapping, -EIO);
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while (nr_pages > 0) {
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ret = find_get_pages_contig(inode->i_mapping, index,
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min_t(unsigned long,
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nr_pages, ARRAY_SIZE(pages)), pages);
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if (ret == 0) {
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nr_pages -= 1;
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index += 1;
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continue;
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}
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for (i = 0; i < ret; i++) {
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if (cb->errors)
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SetPageError(pages[i]);
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end_page_writeback(pages[i]);
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put_page(pages[i]);
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}
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nr_pages -= ret;
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index += ret;
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}
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/* the inode may be gone now */
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}
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/*
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* do the cleanup once all the compressed pages hit the disk.
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* This will clear writeback on the file pages and free the compressed
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* pages.
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*
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* This also calls the writeback end hooks for the file pages so that
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* metadata and checksums can be updated in the file.
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*/
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static void end_compressed_bio_write(struct bio *bio)
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{
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struct compressed_bio *cb = bio->bi_private;
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struct inode *inode;
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struct page *page;
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unsigned long index;
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if (bio->bi_status)
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cb->errors = 1;
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/* if there are more bios still pending for this compressed
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* extent, just exit
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*/
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if (!refcount_dec_and_test(&cb->pending_bios))
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goto out;
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/* ok, we're the last bio for this extent, step one is to
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* call back into the FS and do all the end_io operations
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*/
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inode = cb->inode;
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cb->compressed_pages[0]->mapping = cb->inode->i_mapping;
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btrfs_writepage_endio_finish_ordered(cb->compressed_pages[0],
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cb->start, cb->start + cb->len - 1,
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bio->bi_status == BLK_STS_OK);
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cb->compressed_pages[0]->mapping = NULL;
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end_compressed_writeback(inode, cb);
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/* note, our inode could be gone now */
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/*
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* release the compressed pages, these came from alloc_page and
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* are not attached to the inode at all
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*/
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index = 0;
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for (index = 0; index < cb->nr_pages; index++) {
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page = cb->compressed_pages[index];
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page->mapping = NULL;
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put_page(page);
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}
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/* finally free the cb struct */
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kfree(cb->compressed_pages);
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kfree(cb);
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out:
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bio_put(bio);
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}
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/*
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* worker function to build and submit bios for previously compressed pages.
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* The corresponding pages in the inode should be marked for writeback
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* and the compressed pages should have a reference on them for dropping
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* when the IO is complete.
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*
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* This also checksums the file bytes and gets things ready for
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* the end io hooks.
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*/
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blk_status_t btrfs_submit_compressed_write(struct inode *inode, u64 start,
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unsigned long len, u64 disk_start,
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unsigned long compressed_len,
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struct page **compressed_pages,
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unsigned long nr_pages,
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unsigned int write_flags)
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{
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struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
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struct bio *bio = NULL;
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struct compressed_bio *cb;
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unsigned long bytes_left;
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int pg_index = 0;
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struct page *page;
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u64 first_byte = disk_start;
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struct block_device *bdev;
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blk_status_t ret;
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int skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
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WARN_ON(!PAGE_ALIGNED(start));
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cb = kmalloc(compressed_bio_size(fs_info, compressed_len), GFP_NOFS);
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if (!cb)
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return BLK_STS_RESOURCE;
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refcount_set(&cb->pending_bios, 0);
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cb->errors = 0;
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cb->inode = inode;
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cb->start = start;
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cb->len = len;
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cb->mirror_num = 0;
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cb->compressed_pages = compressed_pages;
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cb->compressed_len = compressed_len;
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cb->orig_bio = NULL;
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cb->nr_pages = nr_pages;
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bdev = fs_info->fs_devices->latest_bdev;
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bio = btrfs_bio_alloc(bdev, first_byte);
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bio->bi_opf = REQ_OP_WRITE | write_flags;
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bio->bi_private = cb;
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bio->bi_end_io = end_compressed_bio_write;
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refcount_set(&cb->pending_bios, 1);
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/* create and submit bios for the compressed pages */
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bytes_left = compressed_len;
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for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
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int submit = 0;
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page = compressed_pages[pg_index];
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page->mapping = inode->i_mapping;
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if (bio->bi_iter.bi_size)
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submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,
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0);
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page->mapping = NULL;
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if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
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PAGE_SIZE) {
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/*
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* inc the count before we submit the bio so
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* we know the end IO handler won't happen before
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* we inc the count. Otherwise, the cb might get
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* freed before we're done setting it up
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*/
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refcount_inc(&cb->pending_bios);
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ret = btrfs_bio_wq_end_io(fs_info, bio,
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BTRFS_WQ_ENDIO_DATA);
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BUG_ON(ret); /* -ENOMEM */
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if (!skip_sum) {
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ret = btrfs_csum_one_bio(inode, bio, start, 1);
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BUG_ON(ret); /* -ENOMEM */
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}
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ret = btrfs_map_bio(fs_info, bio, 0, 1);
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if (ret) {
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bio->bi_status = ret;
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bio_endio(bio);
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}
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bio = btrfs_bio_alloc(bdev, first_byte);
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bio->bi_opf = REQ_OP_WRITE | write_flags;
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bio->bi_private = cb;
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bio->bi_end_io = end_compressed_bio_write;
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bio_add_page(bio, page, PAGE_SIZE, 0);
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}
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if (bytes_left < PAGE_SIZE) {
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btrfs_info(fs_info,
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"bytes left %lu compress len %lu nr %lu",
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bytes_left, cb->compressed_len, cb->nr_pages);
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}
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bytes_left -= PAGE_SIZE;
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first_byte += PAGE_SIZE;
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cond_resched();
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}
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ret = btrfs_bio_wq_end_io(fs_info, bio, BTRFS_WQ_ENDIO_DATA);
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BUG_ON(ret); /* -ENOMEM */
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if (!skip_sum) {
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ret = btrfs_csum_one_bio(inode, bio, start, 1);
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BUG_ON(ret); /* -ENOMEM */
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}
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ret = btrfs_map_bio(fs_info, bio, 0, 1);
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if (ret) {
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bio->bi_status = ret;
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bio_endio(bio);
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}
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return 0;
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}
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static u64 bio_end_offset(struct bio *bio)
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{
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struct bio_vec *last = bio_last_bvec_all(bio);
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return page_offset(last->bv_page) + last->bv_len + last->bv_offset;
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}
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static noinline int add_ra_bio_pages(struct inode *inode,
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u64 compressed_end,
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struct compressed_bio *cb)
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{
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unsigned long end_index;
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unsigned long pg_index;
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u64 last_offset;
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u64 isize = i_size_read(inode);
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int ret;
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struct page *page;
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unsigned long nr_pages = 0;
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struct extent_map *em;
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struct address_space *mapping = inode->i_mapping;
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struct extent_map_tree *em_tree;
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struct extent_io_tree *tree;
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u64 end;
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int misses = 0;
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last_offset = bio_end_offset(cb->orig_bio);
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em_tree = &BTRFS_I(inode)->extent_tree;
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tree = &BTRFS_I(inode)->io_tree;
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if (isize == 0)
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return 0;
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end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
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while (last_offset < compressed_end) {
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pg_index = last_offset >> PAGE_SHIFT;
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if (pg_index > end_index)
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break;
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page = xa_load(&mapping->i_pages, pg_index);
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if (page && !xa_is_value(page)) {
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misses++;
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if (misses > 4)
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break;
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goto next;
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}
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|
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page = __page_cache_alloc(mapping_gfp_constraint(mapping,
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~__GFP_FS));
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if (!page)
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break;
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if (add_to_page_cache_lru(page, mapping, pg_index, GFP_NOFS)) {
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put_page(page);
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goto next;
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}
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|
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end = last_offset + PAGE_SIZE - 1;
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/*
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* at this point, we have a locked page in the page cache
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* for these bytes in the file. But, we have to make
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* sure they map to this compressed extent on disk.
|
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*/
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set_page_extent_mapped(page);
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lock_extent(tree, last_offset, end);
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read_lock(&em_tree->lock);
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em = lookup_extent_mapping(em_tree, last_offset,
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PAGE_SIZE);
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read_unlock(&em_tree->lock);
|
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|
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if (!em || last_offset < em->start ||
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(last_offset + PAGE_SIZE > extent_map_end(em)) ||
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(em->block_start >> 9) != cb->orig_bio->bi_iter.bi_sector) {
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free_extent_map(em);
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unlock_extent(tree, last_offset, end);
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unlock_page(page);
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put_page(page);
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break;
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}
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free_extent_map(em);
|
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|
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if (page->index == end_index) {
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char *userpage;
|
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size_t zero_offset = offset_in_page(isize);
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|
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if (zero_offset) {
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int zeros;
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zeros = PAGE_SIZE - zero_offset;
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userpage = kmap_atomic(page);
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memset(userpage + zero_offset, 0, zeros);
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flush_dcache_page(page);
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kunmap_atomic(userpage);
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}
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}
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|
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ret = bio_add_page(cb->orig_bio, page,
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PAGE_SIZE, 0);
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|
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if (ret == PAGE_SIZE) {
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nr_pages++;
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put_page(page);
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} else {
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unlock_extent(tree, last_offset, end);
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unlock_page(page);
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put_page(page);
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break;
|
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}
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next:
|
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last_offset += PAGE_SIZE;
|
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}
|
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return 0;
|
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}
|
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|
|
/*
|
|
* for a compressed read, the bio we get passed has all the inode pages
|
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* in it. We don't actually do IO on those pages but allocate new ones
|
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* to hold the compressed pages on disk.
|
|
*
|
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* 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 block_device *bdev;
|
|
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;
|
|
|
|
bdev = fs_info->fs_devices->latest_bdev;
|
|
|
|
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(bdev, 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, 0);
|
|
if (ret) {
|
|
comp_bio->bi_status = ret;
|
|
bio_endio(comp_bio);
|
|
}
|
|
|
|
comp_bio = btrfs_bio_alloc(bdev, 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, 0);
|
|
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 heuristic_init_workspace_manager(void)
|
|
{
|
|
btrfs_init_workspace_manager(&heuristic_wsm, &btrfs_heuristic_compress);
|
|
}
|
|
|
|
static void heuristic_cleanup_workspace_manager(void)
|
|
{
|
|
btrfs_cleanup_workspace_manager(&heuristic_wsm);
|
|
}
|
|
|
|
static struct list_head *heuristic_get_workspace(unsigned int level)
|
|
{
|
|
return btrfs_get_workspace(&heuristic_wsm, level);
|
|
}
|
|
|
|
static void heuristic_put_workspace(struct list_head *ws)
|
|
{
|
|
btrfs_put_workspace(&heuristic_wsm, ws);
|
|
}
|
|
|
|
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 = {
|
|
.init_workspace_manager = heuristic_init_workspace_manager,
|
|
.cleanup_workspace_manager = heuristic_cleanup_workspace_manager,
|
|
.get_workspace = heuristic_get_workspace,
|
|
.put_workspace = heuristic_put_workspace,
|
|
.alloc_workspace = alloc_heuristic_ws,
|
|
.free_workspace = free_heuristic_ws,
|
|
};
|
|
|
|
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,
|
|
};
|
|
|
|
void btrfs_init_workspace_manager(struct workspace_manager *wsm,
|
|
const struct btrfs_compress_op *ops)
|
|
{
|
|
struct list_head *workspace;
|
|
|
|
wsm->ops = ops;
|
|
|
|
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 = wsm->ops->alloc_workspace(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);
|
|
}
|
|
}
|
|
|
|
void btrfs_cleanup_workspace_manager(struct workspace_manager *wsman)
|
|
{
|
|
struct list_head *ws;
|
|
|
|
while (!list_empty(&wsman->idle_ws)) {
|
|
ws = wsman->idle_ws.next;
|
|
list_del(ws);
|
|
wsman->ops->free_workspace(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(struct workspace_manager *wsm,
|
|
unsigned int level)
|
|
{
|
|
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;
|
|
|
|
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 = wsm->ops->alloc_workspace(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)
|
|
{
|
|
return btrfs_compress_op[type]->get_workspace(level);
|
|
}
|
|
|
|
/*
|
|
* put a workspace struct back on the list or free it if we have enough
|
|
* idle ones sitting around
|
|
*/
|
|
void btrfs_put_workspace(struct workspace_manager *wsm, struct list_head *ws)
|
|
{
|
|
struct list_head *idle_ws;
|
|
spinlock_t *ws_lock;
|
|
atomic_t *total_ws;
|
|
wait_queue_head_t *ws_wait;
|
|
int *free_ws;
|
|
|
|
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);
|
|
|
|
wsm->ops->free_workspace(ws);
|
|
atomic_dec(total_ws);
|
|
wake:
|
|
cond_wake_up(ws_wait);
|
|
}
|
|
|
|
static void put_workspace(int type, struct list_head *ws)
|
|
{
|
|
return btrfs_compress_op[type]->put_workspace(ws);
|
|
}
|
|
|
|
/*
|
|
* 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_op[type]->set_level(level);
|
|
workspace = get_workspace(type, level);
|
|
ret = btrfs_compress_op[type]->compress_pages(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 = btrfs_compress_op[type]->decompress_bio(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 = btrfs_compress_op[type]->decompress(workspace, data_in,
|
|
dest_page, start_byte,
|
|
srclen, destlen);
|
|
put_workspace(type, workspace);
|
|
|
|
return ret;
|
|
}
|
|
|
|
void __init btrfs_init_compress(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < BTRFS_NR_WORKSPACE_MANAGERS; i++)
|
|
btrfs_compress_op[i]->init_workspace_manager();
|
|
}
|
|
|
|
void __cold btrfs_exit_compress(void)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; i < BTRFS_NR_WORKSPACE_MANAGERS; i++)
|
|
btrfs_compress_op[i]->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_op[type]->set_level(level);
|
|
|
|
return level;
|
|
}
|