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d5e4377d50
The current btrfs zoned device support is a little cumbersome in the data I/O path as it requires the callers to not issue I/O larger than the supported ZONE_APPEND size of the underlying device. This leads to a lot of extra accounting. Instead change btrfs_submit_bio so that it can take write bios of arbitrary size and form from the upper layers, and just split them internally to the ZONE_APPEND queue limits. Then remove all the upper layer warts catering to limited write sized on zoned devices, including the extra refcount in the compressed_bio. Reviewed-by: Josef Bacik <josef@toxicpanda.com> Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: David Sterba <dsterba@suse.com>
1566 lines
41 KiB
C
1566 lines
41 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/pagevec.h>
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#include <linux/highmem.h>
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#include <linux/kthread.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/psi.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 <crypto/hash.h>
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#include "misc.h"
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#include "ctree.h"
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#include "fs.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 "bio.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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#include "subpage.h"
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#include "zoned.h"
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#include "file-item.h"
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#include "super.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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default:
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break;
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}
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return NULL;
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}
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bool btrfs_compress_is_valid_type(const char *str, size_t len)
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{
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int i;
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for (i = 1; i < ARRAY_SIZE(btrfs_compress_types); i++) {
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size_t comp_len = strlen(btrfs_compress_types[i]);
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if (len < comp_len)
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continue;
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if (!strncmp(btrfs_compress_types[i], str, comp_len))
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return true;
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}
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return false;
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}
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static int compression_compress_pages(int type, struct list_head *ws,
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struct address_space *mapping, u64 start, struct page **pages,
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unsigned long *out_pages, unsigned long *total_in,
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unsigned long *total_out)
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{
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switch (type) {
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case BTRFS_COMPRESS_ZLIB:
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return zlib_compress_pages(ws, mapping, start, pages,
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out_pages, total_in, total_out);
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case BTRFS_COMPRESS_LZO:
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return lzo_compress_pages(ws, mapping, start, pages,
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out_pages, total_in, total_out);
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case BTRFS_COMPRESS_ZSTD:
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return zstd_compress_pages(ws, mapping, start, pages,
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out_pages, total_in, total_out);
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case BTRFS_COMPRESS_NONE:
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default:
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/*
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* This can happen when compression races with remount setting
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* it to 'no compress', while caller doesn't call
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* inode_need_compress() to check if we really need to
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* compress.
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*
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* Not a big deal, just need to inform caller that we
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* haven't allocated any pages yet.
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*/
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*out_pages = 0;
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return -E2BIG;
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}
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}
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static int compression_decompress_bio(struct list_head *ws,
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struct compressed_bio *cb)
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{
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switch (cb->compress_type) {
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case BTRFS_COMPRESS_ZLIB: return zlib_decompress_bio(ws, cb);
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case BTRFS_COMPRESS_LZO: return lzo_decompress_bio(ws, cb);
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case BTRFS_COMPRESS_ZSTD: return zstd_decompress_bio(ws, cb);
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case BTRFS_COMPRESS_NONE:
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default:
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/*
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* This can't happen, the type is validated several times
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* before we get here.
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*/
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BUG();
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}
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}
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static int compression_decompress(int type, struct list_head *ws,
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const u8 *data_in, struct page *dest_page,
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unsigned long start_byte, size_t srclen, size_t destlen)
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{
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switch (type) {
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case BTRFS_COMPRESS_ZLIB: return zlib_decompress(ws, data_in, dest_page,
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start_byte, srclen, destlen);
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case BTRFS_COMPRESS_LZO: return lzo_decompress(ws, data_in, dest_page,
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start_byte, srclen, destlen);
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case BTRFS_COMPRESS_ZSTD: return zstd_decompress(ws, data_in, dest_page,
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start_byte, srclen, destlen);
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case BTRFS_COMPRESS_NONE:
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default:
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/*
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* This can't happen, the type is validated several times
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* before we get here.
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*/
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BUG();
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}
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}
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static int btrfs_decompress_bio(struct compressed_bio *cb);
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static void end_compressed_bio_read(struct btrfs_bio *bbio)
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{
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struct compressed_bio *cb = bbio->private;
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unsigned int index;
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struct page *page;
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if (bbio->bio.bi_status)
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cb->status = bbio->bio.bi_status;
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else
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cb->status = errno_to_blk_status(btrfs_decompress_bio(cb));
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/* Release the compressed pages */
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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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btrfs_bio_end_io(btrfs_bio(cb->orig_bio), cb->status);
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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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bio_put(&bbio->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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struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
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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 folio_batch fbatch;
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const int errno = blk_status_to_errno(cb->status);
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int i;
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int ret;
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if (errno)
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mapping_set_error(inode->i_mapping, errno);
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folio_batch_init(&fbatch);
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while (index <= end_index) {
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ret = filemap_get_folios(inode->i_mapping, &index, end_index,
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&fbatch);
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if (ret == 0)
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return;
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for (i = 0; i < ret; i++) {
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struct folio *folio = fbatch.folios[i];
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if (errno)
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folio_set_error(folio);
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btrfs_page_clamp_clear_writeback(fs_info, &folio->page,
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cb->start, cb->len);
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}
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folio_batch_release(&fbatch);
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}
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/* the inode may be gone now */
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}
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static void finish_compressed_bio_write(struct compressed_bio *cb)
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{
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struct inode *inode = cb->inode;
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unsigned int index;
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/*
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* Ok, we're the last bio for this extent, step one is to call back
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* into the FS and do all the end_io operations.
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*/
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btrfs_writepage_endio_finish_ordered(BTRFS_I(inode), NULL,
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cb->start, cb->start + cb->len - 1,
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cb->status == BLK_STS_OK);
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if (cb->writeback)
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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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for (index = 0; index < cb->nr_pages; index++) {
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struct page *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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}
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static void btrfs_finish_compressed_write_work(struct work_struct *work)
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{
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struct compressed_bio *cb =
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container_of(work, struct compressed_bio, write_end_work);
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finish_compressed_bio_write(cb);
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}
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/*
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* Do the cleanup once all the compressed pages hit the disk. This will clear
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* writeback on the file pages and free the compressed pages.
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*
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* This also calls the writeback end hooks for the file pages so that metadata
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* and checksums can be updated in the file.
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*/
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static void end_compressed_bio_write(struct btrfs_bio *bbio)
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{
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struct compressed_bio *cb = bbio->private;
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struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
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cb->status = bbio->bio.bi_status;
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queue_work(fs_info->compressed_write_workers, &cb->write_end_work);
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bio_put(&bbio->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 btrfs_inode *inode, u64 start,
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unsigned int len, u64 disk_start,
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unsigned int compressed_len,
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struct page **compressed_pages,
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unsigned int nr_pages,
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blk_opf_t write_flags,
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struct cgroup_subsys_state *blkcg_css,
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bool writeback)
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{
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struct btrfs_fs_info *fs_info = inode->root->fs_info;
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struct bio *bio = NULL;
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struct compressed_bio *cb;
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u64 cur_disk_bytenr = disk_start;
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blk_status_t ret = BLK_STS_OK;
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ASSERT(IS_ALIGNED(start, fs_info->sectorsize) &&
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IS_ALIGNED(len, fs_info->sectorsize));
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cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS);
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if (!cb)
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return BLK_STS_RESOURCE;
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cb->status = BLK_STS_OK;
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cb->inode = &inode->vfs_inode;
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cb->start = start;
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cb->len = len;
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cb->compressed_pages = compressed_pages;
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cb->compressed_len = compressed_len;
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cb->writeback = writeback;
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INIT_WORK(&cb->write_end_work, btrfs_finish_compressed_write_work);
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cb->nr_pages = nr_pages;
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if (blkcg_css) {
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kthread_associate_blkcg(blkcg_css);
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write_flags |= REQ_CGROUP_PUNT;
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}
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write_flags |= REQ_BTRFS_ONE_ORDERED;
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bio = btrfs_bio_alloc(BIO_MAX_VECS, REQ_OP_WRITE | write_flags,
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BTRFS_I(cb->inode), end_compressed_bio_write, cb);
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bio->bi_iter.bi_sector = cur_disk_bytenr >> SECTOR_SHIFT;
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btrfs_bio(bio)->file_offset = start;
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while (cur_disk_bytenr < disk_start + compressed_len) {
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u64 offset = cur_disk_bytenr - disk_start;
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unsigned int index = offset >> PAGE_SHIFT;
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unsigned int real_size;
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unsigned int added;
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struct page *page = compressed_pages[index];
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/*
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* We have various limits on the real read size:
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* - page boundary
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* - compressed length boundary
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*/
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real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));
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real_size = min_t(u64, real_size, compressed_len - offset);
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ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
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added = bio_add_page(bio, page, real_size, offset_in_page(offset));
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/*
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* Maximum compressed extent is smaller than bio size limit,
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* thus bio_add_page() should always success.
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*/
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ASSERT(added == real_size);
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cur_disk_bytenr += added;
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}
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/* Finished the range. */
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ASSERT(bio->bi_iter.bi_size);
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btrfs_submit_bio(bio, 0);
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if (blkcg_css)
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kthread_associate_blkcg(NULL);
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return ret;
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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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/*
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* Add extra pages in the same compressed file extent so that we don't need to
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* re-read the same extent again and again.
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*
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* NOTE: this won't work well for subpage, as for subpage read, we lock the
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* full page then submit bio for each compressed/regular extents.
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*
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* This means, if we have several sectors in the same page points to the same
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* on-disk compressed data, we will re-read the same extent many times and
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* this function can only help for the next page.
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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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int *memstall, unsigned long *pflags)
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{
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struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
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unsigned long end_index;
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u64 cur = bio_end_offset(cb->orig_bio);
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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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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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int sectors_missed = 0;
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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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/*
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* For current subpage support, we only support 64K page size,
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* which means maximum compressed extent size (128K) is just 2x page
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* size.
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* This makes readahead less effective, so here disable readahead for
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* subpage for now, until full compressed write is supported.
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*/
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if (btrfs_sb(inode->i_sb)->sectorsize < PAGE_SIZE)
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return 0;
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end_index = (i_size_read(inode) - 1) >> PAGE_SHIFT;
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while (cur < compressed_end) {
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u64 page_end;
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u64 pg_index = cur >> PAGE_SHIFT;
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u32 add_size;
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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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sectors_missed += (PAGE_SIZE - offset_in_page(cur)) >>
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fs_info->sectorsize_bits;
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/* Beyond threshold, no need to continue */
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if (sectors_missed > 4)
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break;
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/*
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* Jump to next page start as we already have page for
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* current offset.
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*/
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cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
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continue;
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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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/* There is already a page, skip to page end */
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cur = (pg_index << PAGE_SHIFT) + PAGE_SIZE;
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continue;
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}
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if (!*memstall && PageWorkingset(page)) {
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psi_memstall_enter(pflags);
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*memstall = 1;
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}
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ret = set_page_extent_mapped(page);
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if (ret < 0) {
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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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page_end = (pg_index << PAGE_SHIFT) + PAGE_SIZE - 1;
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lock_extent(tree, cur, page_end, NULL);
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read_lock(&em_tree->lock);
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em = lookup_extent_mapping(em_tree, cur, page_end + 1 - cur);
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read_unlock(&em_tree->lock);
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/*
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* At this point, we have a locked page in the page cache for
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* these bytes in the file. But, we have to make sure they map
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* to this compressed extent on disk.
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*/
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if (!em || cur < em->start ||
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(cur + fs_info->sectorsize > 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, cur, page_end, NULL);
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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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if (page->index == end_index) {
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size_t zero_offset = offset_in_page(isize);
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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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memzero_page(page, zero_offset, zeros);
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}
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}
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add_size = min(em->start + em->len, page_end + 1) - cur;
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ret = bio_add_page(cb->orig_bio, page, add_size, offset_in_page(cur));
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if (ret != add_size) {
|
|
unlock_extent(tree, cur, page_end, NULL);
|
|
unlock_page(page);
|
|
put_page(page);
|
|
break;
|
|
}
|
|
/*
|
|
* If it's subpage, we also need to increase its
|
|
* subpage::readers number, as at endio we will decrease
|
|
* subpage::readers and to unlock the page.
|
|
*/
|
|
if (fs_info->sectorsize < PAGE_SIZE)
|
|
btrfs_subpage_start_reader(fs_info, page, cur, add_size);
|
|
put_page(page);
|
|
cur += add_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
|
|
*/
|
|
void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
|
|
int mirror_num)
|
|
{
|
|
struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
|
|
struct extent_map_tree *em_tree;
|
|
struct compressed_bio *cb;
|
|
unsigned int compressed_len;
|
|
struct bio *comp_bio;
|
|
const u64 disk_bytenr = bio->bi_iter.bi_sector << SECTOR_SHIFT;
|
|
u64 cur_disk_byte = disk_bytenr;
|
|
u64 file_offset;
|
|
u64 em_len;
|
|
u64 em_start;
|
|
struct extent_map *em;
|
|
unsigned long pflags;
|
|
int memstall = 0;
|
|
blk_status_t ret;
|
|
int ret2;
|
|
int i;
|
|
|
|
em_tree = &BTRFS_I(inode)->extent_tree;
|
|
|
|
file_offset = bio_first_bvec_all(bio)->bv_offset +
|
|
page_offset(bio_first_page_all(bio));
|
|
|
|
/* we need the actual starting offset of this extent in the file */
|
|
read_lock(&em_tree->lock);
|
|
em = lookup_extent_mapping(em_tree, file_offset, fs_info->sectorsize);
|
|
read_unlock(&em_tree->lock);
|
|
if (!em) {
|
|
ret = BLK_STS_IOERR;
|
|
goto out;
|
|
}
|
|
|
|
ASSERT(em->compress_type != BTRFS_COMPRESS_NONE);
|
|
compressed_len = em->block_len;
|
|
cb = kmalloc(sizeof(struct compressed_bio), GFP_NOFS);
|
|
if (!cb) {
|
|
ret = BLK_STS_RESOURCE;
|
|
goto out;
|
|
}
|
|
|
|
cb->status = BLK_STS_OK;
|
|
cb->inode = inode;
|
|
|
|
cb->start = em->orig_start;
|
|
em_len = em->len;
|
|
em_start = em->start;
|
|
|
|
cb->len = bio->bi_iter.bi_size;
|
|
cb->compressed_len = compressed_len;
|
|
cb->compress_type = em->compress_type;
|
|
cb->orig_bio = bio;
|
|
|
|
free_extent_map(em);
|
|
em = NULL;
|
|
|
|
cb->nr_pages = DIV_ROUND_UP(compressed_len, PAGE_SIZE);
|
|
cb->compressed_pages = kcalloc(cb->nr_pages, sizeof(struct page *), GFP_NOFS);
|
|
if (!cb->compressed_pages) {
|
|
ret = BLK_STS_RESOURCE;
|
|
goto fail;
|
|
}
|
|
|
|
ret2 = btrfs_alloc_page_array(cb->nr_pages, cb->compressed_pages);
|
|
if (ret2) {
|
|
ret = BLK_STS_RESOURCE;
|
|
goto fail;
|
|
}
|
|
|
|
add_ra_bio_pages(inode, em_start + em_len, cb, &memstall, &pflags);
|
|
|
|
/* include any pages we added in add_ra-bio_pages */
|
|
cb->len = bio->bi_iter.bi_size;
|
|
|
|
comp_bio = btrfs_bio_alloc(BIO_MAX_VECS, REQ_OP_READ, BTRFS_I(cb->inode),
|
|
end_compressed_bio_read, cb);
|
|
comp_bio->bi_iter.bi_sector = (cur_disk_byte >> SECTOR_SHIFT);
|
|
|
|
while (cur_disk_byte < disk_bytenr + compressed_len) {
|
|
u64 offset = cur_disk_byte - disk_bytenr;
|
|
unsigned int index = offset >> PAGE_SHIFT;
|
|
unsigned int real_size;
|
|
unsigned int added;
|
|
struct page *page = cb->compressed_pages[index];
|
|
|
|
/*
|
|
* We have various limit on the real read size:
|
|
* - page boundary
|
|
* - compressed length boundary
|
|
*/
|
|
real_size = min_t(u64, U32_MAX, PAGE_SIZE - offset_in_page(offset));
|
|
real_size = min_t(u64, real_size, compressed_len - offset);
|
|
ASSERT(IS_ALIGNED(real_size, fs_info->sectorsize));
|
|
|
|
added = bio_add_page(comp_bio, page, real_size, offset_in_page(offset));
|
|
/*
|
|
* Maximum compressed extent is smaller than bio size limit,
|
|
* thus bio_add_page() should always success.
|
|
*/
|
|
ASSERT(added == real_size);
|
|
cur_disk_byte += added;
|
|
}
|
|
|
|
if (memstall)
|
|
psi_memstall_leave(&pflags);
|
|
|
|
/*
|
|
* Stash the initial offset of this chunk, as there is no direct
|
|
* correlation between compressed pages and the original file offset.
|
|
* The field is only used for printing error messages anyway.
|
|
*/
|
|
btrfs_bio(comp_bio)->file_offset = file_offset;
|
|
|
|
ASSERT(comp_bio->bi_iter.bi_size);
|
|
btrfs_submit_bio(comp_bio, mirror_num);
|
|
return;
|
|
|
|
fail:
|
|
if (cb->compressed_pages) {
|
|
for (i = 0; i < cb->nr_pages; i++) {
|
|
if (cb->compressed_pages[i])
|
|
__free_page(cb->compressed_pages[i]);
|
|
}
|
|
}
|
|
|
|
kfree(cb->compressed_pages);
|
|
kfree(cb);
|
|
out:
|
|
free_extent_map(em);
|
|
btrfs_bio_end_io(btrfs_bio(bio), ret);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* 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();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Adjust @level according to the limits of the compression algorithm or
|
|
* fallback to default
|
|
*/
|
|
static 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;
|
|
}
|
|
|
|
/*
|
|
* 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
|
|
*/
|
|
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;
|
|
}
|
|
|
|
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(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, const u8 *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;
|
|
}
|
|
|
|
int __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();
|
|
return 0;
|
|
}
|
|
|
|
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 decompressed data from working buffer to pages.
|
|
*
|
|
* @buf: The decompressed data buffer
|
|
* @buf_len: The decompressed data length
|
|
* @decompressed: Number of bytes that are already decompressed inside the
|
|
* compressed extent
|
|
* @cb: The compressed extent descriptor
|
|
* @orig_bio: The original bio that the caller wants to read for
|
|
*
|
|
* An easier to understand graph is like below:
|
|
*
|
|
* |<- orig_bio ->| |<- orig_bio->|
|
|
* |<------- full decompressed extent ----->|
|
|
* |<----------- @cb range ---->|
|
|
* | |<-- @buf_len -->|
|
|
* |<--- @decompressed --->|
|
|
*
|
|
* Note that, @cb can be a subpage of the full decompressed extent, but
|
|
* @cb->start always has the same as the orig_file_offset value of the full
|
|
* decompressed extent.
|
|
*
|
|
* When reading compressed extent, we have to read the full compressed extent,
|
|
* while @orig_bio may only want part of the range.
|
|
* Thus this function will ensure only data covered by @orig_bio will be copied
|
|
* to.
|
|
*
|
|
* Return 0 if we have copied all needed contents for @orig_bio.
|
|
* Return >0 if we need continue decompress.
|
|
*/
|
|
int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
|
|
struct compressed_bio *cb, u32 decompressed)
|
|
{
|
|
struct bio *orig_bio = cb->orig_bio;
|
|
/* Offset inside the full decompressed extent */
|
|
u32 cur_offset;
|
|
|
|
cur_offset = decompressed;
|
|
/* The main loop to do the copy */
|
|
while (cur_offset < decompressed + buf_len) {
|
|
struct bio_vec bvec;
|
|
size_t copy_len;
|
|
u32 copy_start;
|
|
/* Offset inside the full decompressed extent */
|
|
u32 bvec_offset;
|
|
|
|
bvec = bio_iter_iovec(orig_bio, orig_bio->bi_iter);
|
|
/*
|
|
* cb->start may underflow, but subtracting that value can still
|
|
* give us correct offset inside the full decompressed extent.
|
|
*/
|
|
bvec_offset = page_offset(bvec.bv_page) + bvec.bv_offset - cb->start;
|
|
|
|
/* Haven't reached the bvec range, exit */
|
|
if (decompressed + buf_len <= bvec_offset)
|
|
return 1;
|
|
|
|
copy_start = max(cur_offset, bvec_offset);
|
|
copy_len = min(bvec_offset + bvec.bv_len,
|
|
decompressed + buf_len) - copy_start;
|
|
ASSERT(copy_len);
|
|
|
|
/*
|
|
* Extra range check to ensure we didn't go beyond
|
|
* @buf + @buf_len.
|
|
*/
|
|
ASSERT(copy_start - decompressed < buf_len);
|
|
memcpy_to_page(bvec.bv_page, bvec.bv_offset,
|
|
buf + copy_start - decompressed, copy_len);
|
|
cur_offset += copy_len;
|
|
|
|
bio_advance(orig_bio, copy_len);
|
|
/* Finished the bio */
|
|
if (!orig_bio->bi_iter.bi_size)
|
|
return 0;
|
|
}
|
|
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 (!PAGE_ALIGNED(end))
|
|
index_end++;
|
|
|
|
curr_sample_pos = 0;
|
|
while (index < index_end) {
|
|
page = find_get_page(inode->i_mapping, index);
|
|
in_data = kmap_local_page(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_local(in_data);
|
|
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/incompressible) to avoid wasting CPU time on incompressible
|
|
* 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;
|
|
}
|