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smb: client: compress: LZ77 code improvements cleanup
- Check data compressibility with some heuristics (copied from
btrfs):
- should_compress() final decision is is_compressible(data)
- Cleanup compress/lz77.h leaving only lz77_compress() exposed:
- Move parts to compress/lz77.c, while removing the rest of it
because they were either unused, used only once, were
implemented wrong (thanks to David Howells for the help)
- Updated the compression parameters (still compatible with
Windows implementation) trading off ~20% compression ratio
for ~40% performance:
- min match len: 3 -> 4
- max distance: 8KiB -> 1KiB
- hash table type: u32 * -> u64 *
Known bugs:
This implementation currently works fine in general, but breaks with
some payloads used during testing. Investigation ongoing, to be
fixed in a next commit.
Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Co-developed-by: David Howells <dhowells@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Enzo Matsumiya
Steve French
parent
f046d71e84
commit
94ae8c3fee
@ -15,6 +15,7 @@
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#include <linux/slab.h>
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#include <linux/kernel.h>
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#include <linux/uio.h>
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#include <linux/sort.h>
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#include "cifsglob.h"
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#include "../common/smb2pdu.h"
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@ -24,27 +25,361 @@
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#include "compress/lz77.h"
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#include "compress.h"
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int smb_compress(void *buf, const void *data, size_t *len)
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/*
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* The heuristic_*() functions below try to determine data compressibility.
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*
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* Derived from fs/btrfs/compression.c, changing coding style, some parameters, and removing
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* unused parts.
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*
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* Read that file for better and more detailed explanation of the calculations.
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*
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* The algorithms are ran in a collected sample of the input (uncompressed) data.
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* The sample is formed of 2K reads in PAGE_SIZE intervals, with a maximum size of 4M.
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*
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* Parsing the sample goes from "low-hanging fruits" (fastest algorithms, likely compressible)
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* to "need more analysis" (likely uncompressible).
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*/
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struct bucket {
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unsigned int count;
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};
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/**
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* calc_shannon_entropy() - Compute Shannon entropy of the sampled data.
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* @bkt: Bytes counts of the sample.
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* @slen: Size of the sample.
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*
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* Return: true if the level (percentage of number of bits that would be required to
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* compress the data) is below the minimum threshold.
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*
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* Note:
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* There _is_ an entropy level here that's > 65 (minimum threshold) that would indicate a
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* possibility of compression, but compressing, or even further analysing, it would waste so much
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* resources that it's simply not worth it.
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*
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* Also Shannon entropy is the last computed heuristic; if we got this far and ended up
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* with uncertainty, just stay on the safe side and call it uncompressible.
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*/
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static bool calc_shannon_entropy(struct bucket *bkt, size_t slen)
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{
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struct smb2_compression_hdr *hdr;
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size_t buf_len, data_len;
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const size_t threshold = 65, max_entropy = 8 * ilog2(16);
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size_t i, p, p2, len, sum = 0;
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#define pow4(n) (n * n * n * n)
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len = ilog2(pow4(slen));
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for (i = 0; i < 256 && bkt[i].count > 0; i++) {
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p = bkt[i].count;
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p2 = ilog2(pow4(p));
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sum += p * (len - p2);
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}
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sum /= slen;
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return ((sum * 100 / max_entropy) <= threshold);
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}
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/**
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* calc_byte_distribution() - Compute byte distribution on the sampled data.
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* @bkt: Byte counts of the sample.
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* @slen: Size of the sample.
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*
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* Return:
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* 1: High probability (normal (Gaussian) distribution) of the data being compressible.
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* 0: A "hard no" for compression -- either a computed uniform distribution of the bytes (e.g.
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* random or encrypted data), or calc_shannon_entropy() returned false (see above).
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* 2: When computed byte distribution resulted in "low > n < high" grounds.
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* calc_shannon_entropy() should be used for a final decision.
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*/
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static int calc_byte_distribution(struct bucket *bkt, size_t slen)
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{
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const size_t low = 64, high = 200, threshold = slen * 90 / 100;
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size_t sum = 0;
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int i;
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for (i = 0; i < low; i++)
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sum += bkt[i].count;
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if (sum > threshold)
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return i;
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for (; i < high && bkt[i].count > 0; i++) {
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sum += bkt[i].count;
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if (sum > threshold)
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break;
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}
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if (i <= low)
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return 1;
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if (i >= high)
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return 0;
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return 2;
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}
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static bool check_ascii_bytes(const struct bucket *bkt)
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{
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const size_t threshold = 64;
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size_t count = 0;
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int i;
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for (i = 0; i < threshold; i++)
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if (bkt[i].count > 0)
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count++;
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for (; i < 256; i++) {
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if (bkt[i].count > 0) {
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count++;
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if (count > threshold)
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break;
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}
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}
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return (count < threshold);
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}
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static bool check_repeated_data(const u8 *sample, size_t len)
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{
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size_t s = len / 2;
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return (!memcmp(&sample[0], &sample[s], s));
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}
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static int cmp_bkt(const void *_a, const void *_b)
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{
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const struct bucket *a = _a, *b = _b;
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/* Reverse sort. */
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if (a->count > b->count)
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return -1;
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return 1;
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}
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/*
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* TODO:
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* Support other iter types, if required.
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* Only ITER_XARRAY is supported for now.
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*/
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static int collect_sample(const struct iov_iter *iter, ssize_t max, u8 *sample)
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{
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struct folio *folios[16], *folio;
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unsigned int nr, i, j, npages;
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loff_t start = iter->xarray_start + iter->iov_offset;
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pgoff_t last, index = start / PAGE_SIZE;
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size_t len, off, foff;
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ssize_t ret = 0;
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void *p;
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int s = 0;
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last = (start + max - 1) / PAGE_SIZE;
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do {
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nr = xa_extract(iter->xarray, (void **)folios, index, last, ARRAY_SIZE(folios),
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XA_PRESENT);
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if (nr == 0)
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return -EIO;
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for (i = 0; i < nr; i++) {
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folio = folios[i];
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npages = folio_nr_pages(folio);
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foff = start - folio_pos(folio);
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off = foff % PAGE_SIZE;
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for (j = foff / PAGE_SIZE; j < npages; j++) {
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size_t len2;
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len = min_t(size_t, max, PAGE_SIZE - off);
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len2 = min_t(size_t, len, SZ_2K);
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p = kmap_local_page(folio_page(folio, j));
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memcpy(&sample[s], p, len2);
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kunmap_local(p);
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if (ret < 0)
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return ret;
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s += len2;
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if (len2 < SZ_2K || s >= max - SZ_2K)
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return s;
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max -= len;
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if (max <= 0)
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return s;
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start += len;
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off = 0;
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index++;
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}
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}
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} while (nr == ARRAY_SIZE(folios));
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return s;
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}
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/**
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* is_compressible() - Determines if a chunk of data is compressible.
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* @data: Iterator containing uncompressed data.
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*
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* Return:
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* 0: @data is not compressible
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* 1: @data is compressible
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* -ENOMEM: failed to allocate memory for sample buffer
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*
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* Tests shows that this function is quite reliable in predicting data compressibility,
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* matching close to 1:1 with the behaviour of LZ77 compression success and failures.
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*/
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static int is_compressible(const struct iov_iter *data)
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{
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const size_t read_size = SZ_2K, bkt_size = 256, max = SZ_4M;
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struct bucket *bkt;
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int i = 0, ret = 0;
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size_t len;
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u8 *sample;
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len = iov_iter_count(data);
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if (len < read_size)
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return 0;
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if (len - read_size > max)
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len = max;
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sample = kvzalloc(len, GFP_KERNEL);
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if (!sample)
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return -ENOMEM;
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/* Sample 2K bytes per page of the uncompressed data. */
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ret = collect_sample(data, len, sample);
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if (ret < 0)
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goto out;
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len = ret;
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ret = 1;
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if (check_repeated_data(sample, len))
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goto out;
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bkt = kcalloc(bkt_size, sizeof(*bkt), GFP_KERNEL);
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if (!bkt) {
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kvfree(sample);
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return -ENOMEM;
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}
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for (i = 0; i < len; i++)
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bkt[sample[i]].count++;
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if (check_ascii_bytes(bkt))
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goto out;
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/* Sort in descending order */
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sort(bkt, bkt_size, sizeof(*bkt), cmp_bkt, NULL);
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ret = calc_byte_distribution(bkt, len);
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if (ret != 2)
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goto out;
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ret = calc_shannon_entropy(bkt, len);
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out:
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kvfree(sample);
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kfree(bkt);
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WARN(ret < 0, "%s: ret=%d\n", __func__, ret);
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return !!ret;
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}
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bool should_compress(const struct cifs_tcon *tcon, const struct smb_rqst *rq)
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{
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const struct smb2_hdr *shdr = rq->rq_iov->iov_base;
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if (unlikely(!tcon || !tcon->ses || !tcon->ses->server))
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return false;
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if (!tcon->ses->server->compression.enabled)
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return false;
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if (!(tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA))
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return false;
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if (shdr->Command == SMB2_WRITE) {
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const struct smb2_write_req *wreq = rq->rq_iov->iov_base;
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if (wreq->Length < SMB_COMPRESS_MIN_LEN)
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return false;
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return is_compressible(&rq->rq_iter);
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}
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return (shdr->Command == SMB2_READ);
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}
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int smb_compress(struct TCP_Server_Info *server, struct smb_rqst *rq, compress_send_fn send_fn)
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{
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struct iov_iter iter;
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u32 slen, dlen;
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void *src, *dst;
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int ret;
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buf_len = sizeof(struct smb2_write_req);
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data_len = *len;
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*len = 0;
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if (!server || !rq || !rq->rq_iov || !rq->rq_iov->iov_base)
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return -EINVAL;
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hdr = buf;
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hdr->ProtocolId = SMB2_COMPRESSION_TRANSFORM_ID;
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hdr->OriginalCompressedSegmentSize = cpu_to_le32(data_len);
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hdr->Offset = cpu_to_le32(buf_len);
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hdr->Flags = SMB2_COMPRESSION_FLAG_NONE;
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hdr->CompressionAlgorithm = SMB3_COMPRESS_LZ77;
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if (rq->rq_iov->iov_len != sizeof(struct smb2_write_req))
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return -EINVAL;
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/* XXX: add other algs here as they're implemented */
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ret = lz77_compress(data, data_len, buf + SMB_COMPRESS_HDR_LEN + buf_len, &data_len);
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if (!ret)
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*len = SMB_COMPRESS_HDR_LEN + buf_len + data_len;
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slen = iov_iter_count(&rq->rq_iter);
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src = kvzalloc(slen, GFP_KERNEL);
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if (!src) {
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ret = -ENOMEM;
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goto err_free;
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}
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/* Keep the original iter intact. */
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iter = rq->rq_iter;
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if (!copy_from_iter_full(src, slen, &iter)) {
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ret = -EIO;
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goto err_free;
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}
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/*
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* This is just overprovisioning, as the algorithm will error out if @dst reaches 7/8
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* of @slen.
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*/
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dlen = slen;
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dst = kvzalloc(dlen, GFP_KERNEL);
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if (!dst) {
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ret = -ENOMEM;
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goto err_free;
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}
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ret = lz77_compress(src, slen, dst, &dlen);
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if (!ret) {
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struct smb2_compression_hdr hdr = { 0 };
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struct smb_rqst comp_rq = { .rq_nvec = 3, };
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struct kvec iov[3];
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hdr.ProtocolId = SMB2_COMPRESSION_TRANSFORM_ID;
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hdr.OriginalCompressedSegmentSize = cpu_to_le32(slen);
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hdr.CompressionAlgorithm = SMB3_COMPRESS_LZ77;
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hdr.Flags = SMB2_COMPRESSION_FLAG_NONE;
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hdr.Offset = cpu_to_le32(rq->rq_iov[0].iov_len);
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iov[0].iov_base = &hdr;
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iov[0].iov_len = sizeof(hdr);
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iov[1] = rq->rq_iov[0];
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iov[2].iov_base = dst;
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iov[2].iov_len = dlen;
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comp_rq.rq_iov = iov;
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ret = send_fn(server, 1, &comp_rq);
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} else if (ret == -EMSGSIZE || dlen >= slen) {
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ret = send_fn(server, 1, rq);
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}
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err_free:
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kvfree(dst);
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kvfree(src);
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return ret;
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}
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@ -26,18 +26,27 @@
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#define SMB_COMPRESS_PAYLOAD_HDR_LEN 8
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#define SMB_COMPRESS_MIN_LEN PAGE_SIZE
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struct smb_compress_ctx {
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struct TCP_Server_Info *server;
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struct work_struct work;
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struct mid_q_entry *mid;
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void *buf; /* compressed data */
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void *data; /* uncompressed data */
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size_t len;
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};
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#ifdef CONFIG_CIFS_COMPRESSION
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int smb_compress(void *buf, const void *data, size_t *len);
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typedef int (*compress_send_fn)(struct TCP_Server_Info *, int, struct smb_rqst *);
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int smb_compress(struct TCP_Server_Info *server, struct smb_rqst *rq, compress_send_fn send_fn);
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/**
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* should_compress() - Determines if a request (write) or the response to a
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* request (read) should be compressed.
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* @tcon: tcon of the request is being sent to
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* @rqst: request to evaluate
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*
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* Return: true iff:
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* - compression was successfully negotiated with server
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* - server has enabled compression for the share
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* - it's a read or write request
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* - (write only) request length is >= SMB_COMPRESS_MIN_LEN
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* - (write only) is_compressible() returns 1
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*
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* Return false otherwise.
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*/
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bool should_compress(const struct cifs_tcon *tcon, const struct smb_rqst *rq);
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/**
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* smb_compress_alg_valid() - Validate a compression algorithm.
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@ -62,48 +71,20 @@ static __always_inline int smb_compress_alg_valid(__le16 alg, bool valid_none)
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return false;
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}
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|
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/**
|
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* should_compress() - Determines if a request (write) or the response to a
|
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* request (read) should be compressed.
|
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* @tcon: tcon of the request is being sent to
|
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* @buf: buffer with an SMB2 READ/WRITE request
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*
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* Return: true iff:
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* - compression was successfully negotiated with server
|
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* - server has enabled compression for the share
|
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* - it's a read or write request
|
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* - if write, request length is >= SMB_COMPRESS_MIN_LEN
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*
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* Return false otherwise.
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*/
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static __always_inline bool should_compress(const struct cifs_tcon *tcon, const void *buf)
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#else /* !CONFIG_CIFS_COMPRESSION */
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static inline int smb_compress(void *unused1, void *unused2, void *unused3)
|
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{
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const struct smb2_hdr *shdr = buf;
|
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|
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if (!tcon || !tcon->ses || !tcon->ses->server)
|
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return false;
|
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|
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if (!tcon->ses->server->compression.enabled)
|
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return false;
|
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|
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if (!(tcon->share_flags & SMB2_SHAREFLAG_COMPRESS_DATA))
|
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return false;
|
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|
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if (shdr->Command == SMB2_WRITE) {
|
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const struct smb2_write_req *req = buf;
|
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|
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return (req->Length >= SMB_COMPRESS_MIN_LEN);
|
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}
|
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|
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return (shdr->Command == SMB2_READ);
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return -EOPNOTSUPP;
|
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}
|
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|
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static inline bool should_compress(void *unused1, void *unused2)
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{
|
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return false;
|
||||
}
|
||||
|
||||
static inline int smb_compress_alg_valid(__le16 unused1, bool unused2)
|
||||
{
|
||||
return -EOPNOTSUPP;
|
||||
}
|
||||
/*
|
||||
* #else !CONFIG_CIFS_COMPRESSION ...
|
||||
* These routines should not be called when CONFIG_CIFS_COMPRESSION disabled
|
||||
* #define smb_compress(arg1, arg2, arg3) (-EOPNOTSUPP)
|
||||
* #define smb_compress_alg_valid(arg1, arg2) (-EOPNOTSUPP)
|
||||
* #define should_compress(arg1, arg2) (false)
|
||||
*/
|
||||
#endif /* !CONFIG_CIFS_COMPRESSION */
|
||||
#endif /* _SMB_COMPRESS_H */
|
||||
|
||||
@ -7,14 +7,75 @@
|
||||
* Implementation of the LZ77 "plain" compression algorithm, as per MS-XCA spec.
|
||||
*/
|
||||
#include <linux/slab.h>
|
||||
#include <linux/sizes.h>
|
||||
#include <linux/count_zeros.h>
|
||||
#include <asm/unaligned.h>
|
||||
|
||||
#include "lz77.h"
|
||||
|
||||
static __always_inline u32 hash3(const u8 *ptr)
|
||||
/*
|
||||
* Compression parameters.
|
||||
*/
|
||||
#define LZ77_MATCH_MIN_LEN 4
|
||||
#define LZ77_MATCH_MIN_DIST 1
|
||||
#define LZ77_MATCH_MAX_DIST SZ_1K
|
||||
#define LZ77_HASH_LOG 15
|
||||
#define LZ77_HASH_SIZE (1 << LZ77_HASH_LOG)
|
||||
#define LZ77_STEP_SIZE sizeof(u64)
|
||||
|
||||
static __always_inline u8 lz77_read8(const u8 *ptr)
|
||||
{
|
||||
return lz77_hash32(lz77_read32(ptr) & 0xffffff, LZ77_HASH_LOG);
|
||||
return get_unaligned(ptr);
|
||||
}
|
||||
|
||||
static u8 *write_match(u8 *dst, u8 **nib, u32 dist, u32 len)
|
||||
static __always_inline u64 lz77_read64(const u64 *ptr)
|
||||
{
|
||||
return get_unaligned(ptr);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write8(u8 *ptr, u8 v)
|
||||
{
|
||||
put_unaligned(v, ptr);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write16(u16 *ptr, u16 v)
|
||||
{
|
||||
put_unaligned_le16(v, ptr);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write32(u32 *ptr, u32 v)
|
||||
{
|
||||
put_unaligned_le32(v, ptr);
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_match_len(const void *wnd, const void *cur, const void *end)
|
||||
{
|
||||
const void *start = cur;
|
||||
u64 diff;
|
||||
|
||||
/* Safe for a do/while because otherwise we wouldn't reach here from the main loop. */
|
||||
do {
|
||||
diff = lz77_read64(cur) ^ lz77_read64(wnd);
|
||||
if (!diff) {
|
||||
cur += LZ77_STEP_SIZE;
|
||||
wnd += LZ77_STEP_SIZE;
|
||||
|
||||
continue;
|
||||
}
|
||||
|
||||
/* This computes the number of common bytes in @diff. */
|
||||
cur += count_trailing_zeros(diff) >> 3;
|
||||
|
||||
return (cur - start);
|
||||
} while (likely(cur + LZ77_STEP_SIZE < end));
|
||||
|
||||
while (cur < end && lz77_read8(cur++) == lz77_read8(wnd++))
|
||||
;
|
||||
|
||||
return (cur - start);
|
||||
}
|
||||
|
||||
static __always_inline void *lz77_write_match(void *dst, void **nib, u32 dist, u32 len)
|
||||
{
|
||||
len -= 3;
|
||||
dist--;
|
||||
@ -22,6 +83,7 @@ static u8 *write_match(u8 *dst, u8 **nib, u32 dist, u32 len)
|
||||
|
||||
if (len < 7) {
|
||||
lz77_write16(dst, dist + len);
|
||||
|
||||
return dst + 2;
|
||||
}
|
||||
|
||||
@ -31,11 +93,13 @@ static u8 *write_match(u8 *dst, u8 **nib, u32 dist, u32 len)
|
||||
len -= 7;
|
||||
|
||||
if (!*nib) {
|
||||
lz77_write8(dst, umin(len, 15));
|
||||
*nib = dst;
|
||||
lz77_write8(dst, min_t(unsigned int, len, 15));
|
||||
dst++;
|
||||
} else {
|
||||
**nib |= min_t(unsigned int, len, 15) << 4;
|
||||
u8 *b = *nib;
|
||||
|
||||
lz77_write8(b, *b | umin(len, 15) << 4);
|
||||
*nib = NULL;
|
||||
}
|
||||
|
||||
@ -45,15 +109,16 @@ static u8 *write_match(u8 *dst, u8 **nib, u32 dist, u32 len)
|
||||
len -= 15;
|
||||
if (len < 255) {
|
||||
lz77_write8(dst, len);
|
||||
|
||||
return dst + 1;
|
||||
}
|
||||
|
||||
lz77_write8(dst, 0xff);
|
||||
dst++;
|
||||
|
||||
len += 7 + 15;
|
||||
if (len <= 0xffff) {
|
||||
lz77_write16(dst, len);
|
||||
|
||||
return dst + 2;
|
||||
}
|
||||
|
||||
@ -64,148 +129,107 @@ static u8 *write_match(u8 *dst, u8 **nib, u32 dist, u32 len)
|
||||
return dst + 4;
|
||||
}
|
||||
|
||||
static u8 *write_literals(u8 *dst, const u8 *dst_end, const u8 *src, size_t count,
|
||||
struct lz77_flags *flags)
|
||||
noinline int lz77_compress(const void *src, u32 slen, void *dst, u32 *dlen)
|
||||
{
|
||||
const u8 *end = src + count;
|
||||
|
||||
while (src < end) {
|
||||
size_t c = lz77_min(count, 32 - flags->count);
|
||||
|
||||
if (dst + c >= dst_end)
|
||||
return ERR_PTR(-EFAULT);
|
||||
|
||||
if (lz77_copy(dst, src, c))
|
||||
return ERR_PTR(-EFAULT);
|
||||
|
||||
dst += c;
|
||||
src += c;
|
||||
count -= c;
|
||||
|
||||
flags->val <<= c;
|
||||
flags->count += c;
|
||||
if (flags->count == 32) {
|
||||
lz77_write32(flags->pos, flags->val);
|
||||
flags->count = 0;
|
||||
flags->pos = dst;
|
||||
dst += 4;
|
||||
}
|
||||
}
|
||||
|
||||
return dst;
|
||||
}
|
||||
|
||||
static __always_inline bool is_valid_match(const u32 dist, const u32 len)
|
||||
{
|
||||
return (dist >= LZ77_MATCH_MIN_DIST && dist < LZ77_MATCH_MAX_DIST) &&
|
||||
(len >= LZ77_MATCH_MIN_LEN && len < LZ77_MATCH_MAX_LEN);
|
||||
}
|
||||
|
||||
static __always_inline const u8 *find_match(u32 *htable, const u8 *base, const u8 *cur,
|
||||
const u8 *end, u32 *best_len)
|
||||
{
|
||||
const u8 *match;
|
||||
u32 hash;
|
||||
size_t offset;
|
||||
|
||||
hash = hash3(cur);
|
||||
offset = cur - base;
|
||||
|
||||
if (htable[hash] >= offset)
|
||||
return cur;
|
||||
|
||||
match = base + htable[hash];
|
||||
*best_len = lz77_match(match, cur, end);
|
||||
if (is_valid_match(cur - match, *best_len))
|
||||
return match;
|
||||
|
||||
return cur;
|
||||
}
|
||||
|
||||
int lz77_compress(const u8 *src, size_t src_len, u8 *dst, size_t *dst_len)
|
||||
{
|
||||
const u8 *srcp, *src_end, *anchor;
|
||||
struct lz77_flags flags = { 0 };
|
||||
u8 *dstp, *dst_end, *nib;
|
||||
u32 *htable;
|
||||
int ret;
|
||||
const void *srcp, *end;
|
||||
void *dstp, *nib, *flag_pos;
|
||||
u32 flag_count = 0;
|
||||
long flag = 0;
|
||||
u64 *htable;
|
||||
|
||||
srcp = src;
|
||||
anchor = srcp;
|
||||
src_end = src + src_len;
|
||||
|
||||
end = src + slen;
|
||||
dstp = dst;
|
||||
dst_end = dst + *dst_len;
|
||||
flags.pos = dstp;
|
||||
nib = NULL;
|
||||
|
||||
memset(dstp, 0, *dst_len);
|
||||
flag_pos = dstp;
|
||||
dstp += 4;
|
||||
|
||||
htable = kvcalloc(LZ77_HASH_SIZE, sizeof(u32), GFP_KERNEL);
|
||||
htable = kvcalloc(LZ77_HASH_SIZE, sizeof(*htable), GFP_KERNEL);
|
||||
if (!htable)
|
||||
return -ENOMEM;
|
||||
|
||||
/* fill hashtable with invalid offsets */
|
||||
memset(htable, 0xff, LZ77_HASH_SIZE * sizeof(u32));
|
||||
/* Main loop. */
|
||||
do {
|
||||
u32 dist, len = 0;
|
||||
const void *wnd;
|
||||
u64 hash;
|
||||
|
||||
/* from here on, any error is because @dst_len reached >= @src_len */
|
||||
ret = -EMSGSIZE;
|
||||
hash = ((lz77_read64(srcp) << 24) * 889523592379ULL) >> (64 - LZ77_HASH_LOG);
|
||||
wnd = src + htable[hash];
|
||||
htable[hash] = srcp - src;
|
||||
dist = srcp - wnd;
|
||||
|
||||
/* main loop */
|
||||
while (srcp < src_end) {
|
||||
u32 hash, dist, len;
|
||||
const u8 *match;
|
||||
if (dist && dist < LZ77_MATCH_MAX_DIST)
|
||||
len = lz77_match_len(wnd, srcp, end);
|
||||
|
||||
while (srcp + 3 < src_end) {
|
||||
len = LZ77_MATCH_MIN_LEN - 1;
|
||||
match = find_match(htable, src, srcp, src_end, &len);
|
||||
hash = hash3(srcp);
|
||||
htable[hash] = srcp - src;
|
||||
if (len < LZ77_MATCH_MIN_LEN) {
|
||||
lz77_write8(dstp, lz77_read8(srcp));
|
||||
|
||||
if (likely(match < srcp)) {
|
||||
dist = srcp - match;
|
||||
break;
|
||||
dstp++;
|
||||
srcp++;
|
||||
|
||||
flag <<= 1;
|
||||
flag_count++;
|
||||
if (flag_count == 32) {
|
||||
lz77_write32(flag_pos, flag);
|
||||
flag_count = 0;
|
||||
flag_pos = dstp;
|
||||
dstp += 4;
|
||||
}
|
||||
|
||||
srcp++;
|
||||
continue;
|
||||
}
|
||||
|
||||
dstp = write_literals(dstp, dst_end, anchor, srcp - anchor, &flags);
|
||||
if (IS_ERR(dstp))
|
||||
goto err_free;
|
||||
/*
|
||||
* Bail out if @dstp reached >= 7/8 of @slen -- already compressed badly, not worth
|
||||
* going further.
|
||||
*/
|
||||
if (unlikely(dstp - dst >= slen - (slen >> 3))) {
|
||||
*dlen = slen;
|
||||
goto out;
|
||||
}
|
||||
|
||||
if (srcp + 3 >= src_end)
|
||||
goto leftovers;
|
||||
|
||||
dstp = write_match(dstp, &nib, dist, len);
|
||||
dstp = lz77_write_match(dstp, &nib, dist, len);
|
||||
srcp += len;
|
||||
anchor = srcp;
|
||||
|
||||
flags.val = (flags.val << 1) | 1;
|
||||
flags.count++;
|
||||
if (flags.count == 32) {
|
||||
lz77_write32(flags.pos, flags.val);
|
||||
flags.count = 0;
|
||||
flags.pos = dstp;
|
||||
flag = (flag << 1) | 1;
|
||||
flag_count++;
|
||||
if (flag_count == 32) {
|
||||
lz77_write32(flag_pos, flag);
|
||||
flag_count = 0;
|
||||
flag_pos = dstp;
|
||||
dstp += 4;
|
||||
}
|
||||
} while (likely(srcp + LZ77_STEP_SIZE < end));
|
||||
|
||||
while (srcp < end) {
|
||||
u32 c = umin(end - srcp, 32 - flag_count);
|
||||
|
||||
memcpy(dstp, srcp, c);
|
||||
|
||||
dstp += c;
|
||||
srcp += c;
|
||||
|
||||
flag <<= c;
|
||||
flag_count += c;
|
||||
if (flag_count == 32) {
|
||||
lz77_write32(flag_pos, flag);
|
||||
flag_count = 0;
|
||||
flag_pos = dstp;
|
||||
dstp += 4;
|
||||
}
|
||||
}
|
||||
leftovers:
|
||||
if (srcp < src_end) {
|
||||
dstp = write_literals(dstp, dst_end, srcp, src_end - srcp, &flags);
|
||||
if (IS_ERR(dstp))
|
||||
goto err_free;
|
||||
}
|
||||
|
||||
flags.val <<= (32 - flags.count);
|
||||
flags.val |= (1 << (32 - flags.count)) - 1;
|
||||
lz77_write32(flags.pos, flags.val);
|
||||
flag <<= (32 - flag_count);
|
||||
flag |= (1 << (32 - flag_count)) - 1;
|
||||
lz77_write32(flag_pos, flag);
|
||||
|
||||
*dst_len = dstp - dst;
|
||||
ret = 0;
|
||||
err_free:
|
||||
*dlen = dstp - dst;
|
||||
out:
|
||||
kvfree(htable);
|
||||
|
||||
return ret;
|
||||
if (*dlen < slen)
|
||||
return 0;
|
||||
|
||||
return -EMSGSIZE;
|
||||
}
|
||||
|
||||
@ -4,283 +4,12 @@
|
||||
*
|
||||
* Authors: Enzo Matsumiya <ematsumiya@suse.de>
|
||||
*
|
||||
* Definitions and optmized helpers for LZ77 compression.
|
||||
* Implementation of the LZ77 "plain" compression algorithm, as per MS-XCA spec.
|
||||
*/
|
||||
#ifndef _SMB_COMPRESS_LZ77_H
|
||||
#define _SMB_COMPRESS_LZ77_H
|
||||
|
||||
#include <linux/uaccess.h>
|
||||
#ifdef CONFIG_CIFS_COMPRESSION
|
||||
#include <asm/ptrace.h>
|
||||
#include <linux/kernel.h>
|
||||
#include <linux/string.h>
|
||||
#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
|
||||
#include <asm-generic/unaligned.h>
|
||||
#endif
|
||||
|
||||
#define LZ77_HASH_LOG 13
|
||||
#define LZ77_HASH_SIZE (1 << LZ77_HASH_LOG)
|
||||
#define LZ77_HASH_MASK lz77_hash_mask(LZ77_HASH_LOG)
|
||||
|
||||
/* We can increase this for better compression (but worse performance). */
|
||||
#define LZ77_MATCH_MIN_LEN 3
|
||||
/* From MS-XCA, but it's arbitrarily chosen. */
|
||||
#define LZ77_MATCH_MAX_LEN S32_MAX
|
||||
/*
|
||||
* Check this to ensure we don't match the current position, which would
|
||||
* end up doing a verbatim copy of the input, and actually overflowing
|
||||
* the output buffer because of the encoded metadata.
|
||||
*/
|
||||
#define LZ77_MATCH_MIN_DIST 1
|
||||
/* How far back in the buffer can we try to find a match (i.e. window size) */
|
||||
#define LZ77_MATCH_MAX_DIST 8192
|
||||
|
||||
#define LZ77_STEPSIZE_16 sizeof(u16)
|
||||
#define LZ77_STEPSIZE_32 sizeof(u32)
|
||||
#define LZ77_STEPSIZE_64 sizeof(u64)
|
||||
|
||||
struct lz77_flags {
|
||||
u8 *pos;
|
||||
size_t count;
|
||||
long val;
|
||||
};
|
||||
|
||||
static __always_inline u32 lz77_hash_mask(const unsigned int log2)
|
||||
{
|
||||
return ((1 << log2) - 1);
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_hash64(const u64 v, const unsigned int log2)
|
||||
{
|
||||
const u64 prime5bytes = 889523592379ULL;
|
||||
|
||||
return (u32)(((v << 24) * prime5bytes) >> (64 - log2));
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_hash32(const u32 v, const unsigned int log2)
|
||||
{
|
||||
return ((v * 2654435769LL) >> (32 - log2)) & lz77_hash_mask(log2);
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_log2(unsigned int x)
|
||||
{
|
||||
return x ? ((u32)(31 - __builtin_clz(x))) : 0;
|
||||
}
|
||||
|
||||
#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
|
||||
static __always_inline u8 lz77_read8(const void *ptr)
|
||||
{
|
||||
return *(u8 *)ptr;
|
||||
}
|
||||
|
||||
static __always_inline u16 lz77_read16(const void *ptr)
|
||||
{
|
||||
return *(u16 *)ptr;
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_read32(const void *ptr)
|
||||
{
|
||||
return *(u32 *)ptr;
|
||||
}
|
||||
|
||||
static __always_inline u64 lz77_read64(const void *ptr)
|
||||
{
|
||||
return *(u64 *)ptr;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write8(void *ptr, const u8 v)
|
||||
{
|
||||
*(u8 *)ptr = v;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write16(void *ptr, const u16 v)
|
||||
{
|
||||
*(u16 *)ptr = v;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write32(void *ptr, const u32 v)
|
||||
{
|
||||
*(u32 *)ptr = v;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write64(void *ptr, const u64 v)
|
||||
{
|
||||
*(u64 *)ptr = v;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr16(void *ptr, const void *vp)
|
||||
{
|
||||
*(u16 *)ptr = *(const u16 *)vp;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr32(void *ptr, const void *vp)
|
||||
{
|
||||
*(u32 *)ptr = *(const u32 *)vp;
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr64(void *ptr, const void *vp)
|
||||
{
|
||||
*(u64 *)ptr = *(const u64 *)vp;
|
||||
}
|
||||
|
||||
static __always_inline long lz77_copy(u8 *dst, const u8 *src, size_t count)
|
||||
{
|
||||
return copy_from_kernel_nofault(dst, src, count);
|
||||
}
|
||||
#else /* CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
|
||||
static __always_inline u8 lz77_read8(const void *ptr)
|
||||
{
|
||||
return get_unaligned((u8 *)ptr);
|
||||
}
|
||||
|
||||
static __always_inline u16 lz77_read16(const void *ptr)
|
||||
{
|
||||
return lz77_read8(ptr) | (lz77_read8(ptr + 1) << 8);
|
||||
}
|
||||
|
||||
static __always_inline u32 lz77_read32(const void *ptr)
|
||||
{
|
||||
return lz77_read16(ptr) | (lz77_read16(ptr + 2) << 16);
|
||||
}
|
||||
|
||||
static __always_inline u64 lz77_read64(const void *ptr)
|
||||
{
|
||||
return lz77_read32(ptr) | ((u64)lz77_read32(ptr + 4) << 32);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write8(void *ptr, const u8 v)
|
||||
{
|
||||
put_unaligned(v, (u8 *)ptr);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write16(void *ptr, const u16 v)
|
||||
{
|
||||
lz77_write8(ptr, v & 0xff);
|
||||
lz77_write8(ptr + 1, (v >> 8) & 0xff);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write32(void *ptr, const u32 v)
|
||||
{
|
||||
lz77_write16(ptr, v & 0xffff);
|
||||
lz77_write16(ptr + 2, (v >> 16) & 0xffff);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write64(void *ptr, const u64 v)
|
||||
{
|
||||
lz77_write32(ptr, v & 0xffffffff);
|
||||
lz77_write32(ptr + 4, (v >> 32) & 0xffffffff);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr16(void *ptr, const void *vp)
|
||||
{
|
||||
const u16 v = lz77_read16(vp);
|
||||
|
||||
lz77_write16(ptr, v);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr32(void *ptr, const void *vp)
|
||||
{
|
||||
const u32 v = lz77_read32(vp);
|
||||
|
||||
lz77_write32(ptr, v);
|
||||
}
|
||||
|
||||
static __always_inline void lz77_write_ptr64(void *ptr, const void *vp)
|
||||
{
|
||||
const u64 v = lz77_read64(vp);
|
||||
|
||||
lz77_write64(ptr, v);
|
||||
}
|
||||
static __always_inline long lz77_copy(u8 *dst, const u8 *src, size_t count)
|
||||
{
|
||||
memcpy(dst, src, count);
|
||||
return 0;
|
||||
}
|
||||
#endif /* !CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS */
|
||||
|
||||
static __always_inline unsigned int __count_common_bytes(const unsigned long diff)
|
||||
{
|
||||
#ifdef __has_builtin
|
||||
# if __has_builtin(__builtin_ctzll)
|
||||
return (unsigned int)__builtin_ctzll(diff) >> 3;
|
||||
# endif
|
||||
#else
|
||||
/* count trailing zeroes */
|
||||
unsigned long bits = 0, i, z = 0;
|
||||
|
||||
bits |= diff;
|
||||
for (i = 0; i < 64; i++) {
|
||||
if (bits[i])
|
||||
break;
|
||||
z++;
|
||||
}
|
||||
|
||||
return (unsigned int)z >> 3;
|
||||
#endif
|
||||
}
|
||||
|
||||
static __always_inline size_t lz77_match(const u8 *match, const u8 *cur, const u8 *end)
|
||||
{
|
||||
const u8 *start = cur;
|
||||
|
||||
if (cur == match)
|
||||
return 0;
|
||||
|
||||
if (likely(cur < end - (LZ77_STEPSIZE_64 - 1))) {
|
||||
u64 const diff = lz77_read64(cur) ^ lz77_read64(match);
|
||||
|
||||
if (!diff) {
|
||||
cur += LZ77_STEPSIZE_64;
|
||||
match += LZ77_STEPSIZE_64;
|
||||
} else {
|
||||
return __count_common_bytes(diff);
|
||||
}
|
||||
}
|
||||
|
||||
while (likely(cur < end - (LZ77_STEPSIZE_64 - 1))) {
|
||||
u64 const diff = lz77_read64(cur) ^ lz77_read64(match);
|
||||
|
||||
if (!diff) {
|
||||
cur += LZ77_STEPSIZE_64;
|
||||
match += LZ77_STEPSIZE_64;
|
||||
continue;
|
||||
}
|
||||
|
||||
cur += __count_common_bytes(diff);
|
||||
return (size_t)(cur - start);
|
||||
}
|
||||
|
||||
if (cur < end - 3 && !(lz77_read32(cur) ^ lz77_read32(match))) {
|
||||
cur += LZ77_STEPSIZE_32;
|
||||
match += LZ77_STEPSIZE_32;
|
||||
}
|
||||
|
||||
if (cur < end - 1 && lz77_read16(cur) == lz77_read16(match)) {
|
||||
cur += LZ77_STEPSIZE_16;
|
||||
match += LZ77_STEPSIZE_16;
|
||||
}
|
||||
|
||||
if (cur < end && *cur == *match)
|
||||
cur++;
|
||||
|
||||
return (size_t)(cur - start);
|
||||
}
|
||||
|
||||
static __always_inline unsigned long lz77_max(unsigned long a, unsigned long b)
|
||||
{
|
||||
int m = (a < b) - 1;
|
||||
|
||||
return (a & m) | (b & ~m);
|
||||
}
|
||||
|
||||
static __always_inline unsigned long lz77_min(unsigned long a, unsigned long b)
|
||||
{
|
||||
int m = (a > b) - 1;
|
||||
|
||||
return (a & m) | (b & ~m);
|
||||
}
|
||||
|
||||
int lz77_compress(const u8 *src, size_t src_len, u8 *dst, size_t *dst_len);
|
||||
/* when CONFIG_CIFS_COMPRESSION not set lz77_compress() is not called */
|
||||
#endif /* !CONFIG_CIFS_COMPRESSION */
|
||||
int lz77_compress(const void *src, u32 slen, void *dst, u32 *dlen);
|
||||
#endif /* _SMB_COMPRESS_LZ77_H */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user