[PATCH v3 06/10] fs/ntfs3: Add compression

Konstantin Komarov
2020-08-28T14:41:27Z

This adds compression

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
---
fs/ntfs3/lznt.c | 451 ++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 451 insertions(+)
create mode 100644 fs/ntfs3/lznt.c

diff --git a/fs/ntfs3/lznt.c b/fs/ntfs3/lznt.c
new file mode 100644
index 000000000000..123ee648dc38
--- /dev/null
+++ b/fs/ntfs3/lznt.c
@@ -0,0 +1,451 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * linux/fs/ntfs3/lznt.c
+ *
+ * Copyright (C) 2019-2020 Paragon Software GmbH, All rights reserved.
+ *
+ */
+#include <linux/blkdev.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/nls.h>
+#include <linux/sched/signal.h>
+
+#include "debug.h"
+#include "ntfs.h"
+#include "ntfs_fs.h"
+
+/* src buffer is zero */
+#define LZNT_ERROR_ALL_ZEROS 1
+#define LZNT_CHUNK_SIZE 0x1000
+
+struct lznt_hash {
+ const u8 *p1;
+ const u8 *p2;
+};
+
+struct lznt {
+ const u8 *unc;
+ const u8 *unc_end;
+ const u8 *best_match;
+ size_t max_len;
+ bool std;
+
+ struct lznt_hash hash[LZNT_CHUNK_SIZE];
+};
+
+static inline size_t get_match_len(const u8 *ptr, const u8 *end, const u8 *prev,
+ size_t max_len)
+{
+ size_t len = 0;
+
+ while (ptr + len < end && ptr[len] == prev[len] && ++len < max_len)
+ ;
+ return len;
+}
+
+static size_t longest_match_std(const u8 *src, struct lznt *ctx)
+{
+ size_t hash_index;
+ size_t len1 = 0, len2 = 0;
+ const u8 **hash;
+
+ hash_index =
+ ((40543U * ((((src[0] << 4) ^ src[1]) << 4) ^ src[2])) >> 4) &
+ (LZNT_CHUNK_SIZE - 1);
+
+ hash = &(ctx->hash[hash_index].p1);
+
+ if (hash[0] >= ctx->unc && hash[0] < src && hash[0][0] == src[0] &&
+ hash[0][1] == src[1] && hash[0][2] == src[2]) {
+ len1 = 3;
+ if (ctx->max_len > 3)
+ len1 += get_match_len(src + 3, ctx->unc_end,
+ hash[0] + 3, ctx->max_len - 3);
+ }
+
+ if (hash[1] >= ctx->unc && hash[1] < src && hash[1][0] == src[0] &&
+ hash[1][1] == src[1] && hash[1][2] == src[2]) {
+ len2 = 3;
+ if (ctx->max_len > 3)
+ len2 += get_match_len(src + 3, ctx->unc_end,
+ hash[1] + 3, ctx->max_len - 3);
+ }
+
+ /* Compare two matches and select the best one */
+ if (len1 < len2) {
+ ctx->best_match = hash[1];
+ len1 = len2;
+ } else
+ ctx->best_match = hash[0];
+
+ hash[1] = hash[0];
+ hash[0] = src;
+ return len1;
+}
+
+static size_t longest_match_best(const u8 *src, struct lznt *ctx)
+{
+ size_t max_len;
+ const u8 *ptr;
+
+ if (ctx->unc >= src || !ctx->max_len)
+ return 0;
+
+ max_len = 0;
+ for (ptr = ctx->unc; ptr < src; ++ptr) {
+ size_t len =
+ get_match_len(src, ctx->unc_end, ptr, ctx->max_len);
+ if (len >= max_len) {
+ max_len = len;
+ ctx->best_match = ptr;
+ }
+ }
+
+ return max_len >= 3 ? max_len : 0;
+}
+
+static const size_t s_max_len[] = {
+ 0x1002, 0x802, 0x402, 0x202, 0x102, 0x82, 0x42, 0x22, 0x12,
+};
+
+static const size_t s_max_off[] = {
+ 0x10, 0x20, 0x40, 0x80, 0x100, 0x200, 0x400, 0x800, 0x1000,
+};
+
+static inline u16 make_pair(size_t offset, size_t len, size_t index)
+{
+ return ((offset - 1) << (12 - index)) |
+ ((len - 3) & (((1 << (12 - index)) - 1)));
+}
+
+static inline size_t parse_pair(u16 pair, size_t *offset, size_t index)
+{
+ *offset = 1 + (pair >> (12 - index));
+ return 3 + (pair & ((1 << (12 - index)) - 1));
+}
+
+/*
+ * compress_chunk
+ *
+ * returns one of the three values:
+ * 0 - ok, 'cmpr' contains 'cmpr_chunk_size' bytes of compressed data
+ * 1 - input buffer is full zero
+ * -2 - the compressed buffer is too small to hold the compressed data
+ */
+static inline int compress_chunk(size_t (*match)(const u8 *, struct lznt *),
+ const u8 *unc, const u8 *unc_end, u8 *cmpr,
+ u8 *cmpr_end, size_t *cmpr_chunk_size,
+ struct lznt *ctx)
+{
+ size_t cnt = 0;
+ size_t idx = 0;
+ const u8 *up = unc;
+ u8 *cp = cmpr + 3;
+ u8 *cp2 = cmpr + 2;
+ u8 not_zero = 0;
+ /* Control byte of 8-bit values: ( 0 - means byte as is, 1 - short pair ) */
+ u8 ohdr = 0;
+ u8 *last;
+ u16 t16;
+
+ if (unc + LZNT_CHUNK_SIZE < unc_end)
+ unc_end = unc + LZNT_CHUNK_SIZE;
+
+ last = min(cmpr + LZNT_CHUNK_SIZE + sizeof(short), cmpr_end);
+
+ ctx->unc = unc;
+ ctx->unc_end = unc_end;
+ ctx->max_len = s_max_len[0];
+
+ while (up < unc_end) {
+ size_t max_len;
+
+ while (unc + s_max_off[idx] < up)
+ ctx->max_len = s_max_len[++idx];
+
+ // Find match
+ max_len = up + 3 <= unc_end ? (*match)(up, ctx) : 0;
+
+ if (!max_len) {
+ if (cp >= last)
+ goto NotCompressed;
+ not_zero |= *cp++ = *up++;
+ } else if (cp + 1 >= last) {
+ goto NotCompressed;
+ } else {
+ t16 = make_pair(up - ctx->best_match, max_len, idx);
+ *cp++ = t16;
+ *cp++ = t16 >> 8;
+
+ ohdr |= 1 << cnt;
+ up += max_len;
+ }
+
+ cnt = (cnt + 1) & 7;
+ if (!cnt) {
+ *cp2 = ohdr;
+ ohdr = 0;
+ cp2 = cp;
+ cp += 1;
+ }
+ }
+
+ if (cp2 < last)
+ *cp2 = ohdr;
+ else
+ cp -= 1;
+
+ *cmpr_chunk_size = cp - cmpr;
+
+ t16 = (*cmpr_chunk_size - 3) | 0xB000;
+ cmpr[0] = t16;
+ cmpr[1] = t16 >> 8;
+
+ return not_zero ? 0 : LZNT_ERROR_ALL_ZEROS;
+
+NotCompressed:
+
+ if ((cmpr + LZNT_CHUNK_SIZE + sizeof(short)) > last)
+ return -2;
+
+ /*
+ * Copy non cmpr data
+ * 0x3FFF == ((LZNT_CHUNK_SIZE + 2 - 3) | 0x3000)
+ */
+ cmpr[0] = 0xff;
+ cmpr[1] = 0x3f;
+
+ memcpy(cmpr + sizeof(short), unc, LZNT_CHUNK_SIZE);
+ *cmpr_chunk_size = LZNT_CHUNK_SIZE + sizeof(short);
+
+ return 0;
+}
+
+static inline ssize_t decompress_chunk(u8 *unc, u8 *unc_end, const u8 *cmpr,
+ const u8 *cmpr_end)
+{
+ u8 *up = unc;
+ u8 ch = *cmpr++;
+ size_t bit = 0;
+ size_t index = 0;
+ u16 pair;
+ size_t offset, length;
+
+ /* Do decompression until pointers are inside range */
+ while (up < unc_end && cmpr < cmpr_end) {
+ /* Correct index */
+ while (unc + s_max_off[index] < up)
+ index += 1;
+
+ /* Check the current flag for zero */
+ if (!(ch & (1 << bit))) {
+ /* Just copy byte */
+ *up++ = *cmpr++;
+ goto next;
+ }
+
+ /* Check for boundary */
+ if (cmpr + 1 >= cmpr_end)
+ return -EINVAL;
+
+ /* Read a short from little endian stream */
+ pair = cmpr[1];
+ pair <<= 8;
+ pair |= cmpr[0];
+
+ cmpr += 2;
+
+ /* Translate packed information into offset and length */
+ length = parse_pair(pair, &offset, index);
+
+ /* Check offset for boundary */
+ if (unc + offset > up)
+ return -EINVAL;
+
+ /* Truncate the length if necessary */
+ if (up + length >= unc_end)
+ length = unc_end - up;
+
+ /* Now we copy bytes. This is the heart of LZ algorithm. */
+ for (; length > 0; length--, up++)
+ *up = *(up - offset);
+
+next:
+ /* Advance flag bit value */
+ bit = (bit + 1) & 7;
+
+ if (!bit) {
+ if (cmpr >= cmpr_end)
+ break;
+
+ ch = *cmpr++;
+ }
+ }
+
+ /* return the size of uncompressed data */
+ return up - unc;
+}
+
+/*
+ * std = true - standard compression
+ * std = false - best compression, requires a lot of cpu
+ */
+struct lznt *get_compression_ctx(bool std)
+{
+ struct lznt *r = ntfs_alloc(
+ std ? sizeof(struct lznt) : offsetof(struct lznt, hash), 1);
+
+ if (r)
+ r->std = std;
+ return r;
+}
+
+/*
+ * compress_lznt
+ *
+ * Compresses "unc" into "cmpr"
+ * +x - ok, 'cmpr' contains 'final_compressed_size' bytes of compressed data
+ * 0 - input buffer is full zero
+ */
+size_t compress_lznt(const void *unc, size_t unc_size, void *cmpr,
+ size_t cmpr_size, struct lznt *ctx)
+{
+ int err;
+ size_t (*match)(const u8 *src, struct lznt *ctx);
+ u8 *p = cmpr;
+ u8 *end = p + cmpr_size;
+ const u8 *unc_chunk = unc;
+ const u8 *unc_end = unc_chunk + unc_size;
+ bool is_zero = true;
+
+ if (ctx->std) {
+ match = &longest_match_std;
+ memset(ctx->hash, 0, sizeof(ctx->hash));
+ } else {
+ match = &longest_match_best;
+ }
+
+ /* compression cycle */
+ for (; unc_chunk < unc_end; unc_chunk += LZNT_CHUNK_SIZE) {
+ cmpr_size = 0;
+ err = compress_chunk(match, unc_chunk, unc_end, p, end,
+ &cmpr_size, ctx);
+ if (err < 0)
+ return unc_size;
+
+ if (is_zero && err != LZNT_ERROR_ALL_ZEROS)
+ is_zero = false;
+
+ p += cmpr_size;
+ }
+
+ if (p <= end - 2)
+ p[0] = p[1] = 0;
+
+ return is_zero ? 0 : PtrOffset(cmpr, p);
+}
+
+/*
+ * decompress_lznt
+ *
+ * decompresses "cmpr" into "unc"
+ */
+ssize_t decompress_lznt(const void *cmpr, size_t cmpr_size, void *unc,
+ size_t unc_size)
+{
+ const u8 *cmpr_chunk = cmpr;
+ const u8 *cmpr_end = cmpr_chunk + cmpr_size;
+ u8 *unc_chunk = unc;
+ u8 *unc_end = unc_chunk + unc_size;
+ u16 chunk_hdr;
+
+ if (cmpr_size < sizeof(short))
+ return -EINVAL;
+
+ /* read chunk header */
+ chunk_hdr = cmpr_chunk[1];
+ chunk_hdr <<= 8;
+ chunk_hdr |= cmpr_chunk[0];
+
+ /* loop through decompressing chunks */
+ for (;;) {
+ size_t chunk_size_saved;
+ size_t unc_use;
+ size_t cmpr_use = 3 + (chunk_hdr & (LZNT_CHUNK_SIZE - 1));
+
+ /* Check that the chunk actually fits the supplied buffer */
+ if (cmpr_chunk + cmpr_use > cmpr_end)
+ return -EINVAL;
+
+ /* First make sure the chunk contains compressed data */
+ if (chunk_hdr & 0x8000) {
+ /* Decompress a chunk and return if we get an error */
+ ssize_t err =
+ decompress_chunk(unc_chunk, unc_end,
+ cmpr_chunk + sizeof(chunk_hdr),
+ cmpr_chunk + cmpr_use);
+ if (err < 0)
+ return err;
+ unc_use = err;
+ } else {
+ /* This chunk does not contain compressed data */
+ unc_use = unc_chunk + LZNT_CHUNK_SIZE > unc_end ?
+ unc_end - unc_chunk :
+ LZNT_CHUNK_SIZE;
+
+ if (cmpr_chunk + sizeof(chunk_hdr) + unc_use >
+ cmpr_end) {
+ return -EINVAL;
+ }
+
+ memcpy(unc_chunk, cmpr_chunk + sizeof(chunk_hdr),
+ unc_use);
+ }
+
+ /* Advance pointers */
+ cmpr_chunk += cmpr_use;
+ unc_chunk += unc_use;
+
+ /* Check for the end of unc buffer */
+ if (unc_chunk >= unc_end)
+ break;
+
+ /* Proceed the next chunk */
+ if (cmpr_chunk > cmpr_end - 2)
+ break;
+
+ chunk_size_saved = LZNT_CHUNK_SIZE;
+
+ /* read chunk header */
+ chunk_hdr = cmpr_chunk[1];
+ chunk_hdr <<= 8;
+ chunk_hdr |= cmpr_chunk[0];
+
+ if (!chunk_hdr)
+ break;
+
+ /* Check the size of unc buffer */
+ if (unc_use < chunk_size_saved) {
+ size_t t1 = chunk_size_saved - unc_use;
+ u8 *t2 = unc_chunk + t1;
+
+ /* 'Zero' memory */
+ if (t2 >= unc_end)
+ break;
+
+ memset(unc_chunk, 0, t1);
+ unc_chunk = t2;
+ }
+ }
+
+ /* Check compression boundary */
+ if (cmpr_chunk > cmpr_end)
+ return -EINVAL;
+
+ /*
+ * The unc size is just a difference between current
+ * pointer and original one
+ */
+ return PtrOffset(unc, unc_chunk);
+}
--
2.25.2