linux/fs/erofs/decompressor.c

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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2019 HUAWEI, Inc.
* http://www.huawei.com/
* Created by Gao Xiang <gaoxiang25@huawei.com>
*/
#include "compress.h"
#include <linux/module.h>
#include <linux/lz4.h>
#ifndef LZ4_DISTANCE_MAX /* history window size */
#define LZ4_DISTANCE_MAX 65535 /* set to maximum value by default */
#endif
#define LZ4_MAX_DISTANCE_PAGES (DIV_ROUND_UP(LZ4_DISTANCE_MAX, PAGE_SIZE) + 1)
#ifndef LZ4_DECOMPRESS_INPLACE_MARGIN
#define LZ4_DECOMPRESS_INPLACE_MARGIN(srcsize) (((srcsize) >> 8) + 32)
#endif
struct z_erofs_decompressor {
/*
* if destpages have sparsed pages, fill them with bounce pages.
* it also check whether destpages indicate continuous physical memory.
*/
int (*prepare_destpages)(struct z_erofs_decompress_req *rq,
struct list_head *pagepool);
int (*decompress)(struct z_erofs_decompress_req *rq, u8 *out);
char *name;
};
static bool use_vmap;
module_param(use_vmap, bool, 0444);
MODULE_PARM_DESC(use_vmap, "Use vmap() instead of vm_map_ram() (default 0)");
static int lz4_prepare_destpages(struct z_erofs_decompress_req *rq,
struct list_head *pagepool)
{
const unsigned int nr =
PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
struct page *availables[LZ4_MAX_DISTANCE_PAGES] = { NULL };
unsigned long bounced[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
BITS_PER_LONG)] = { 0 };
void *kaddr = NULL;
unsigned int i, j, top;
top = 0;
for (i = j = 0; i < nr; ++i, ++j) {
struct page *const page = rq->out[i];
struct page *victim;
if (j >= LZ4_MAX_DISTANCE_PAGES)
j = 0;
/* 'valid' bounced can only be tested after a complete round */
if (test_bit(j, bounced)) {
DBG_BUGON(i < LZ4_MAX_DISTANCE_PAGES);
DBG_BUGON(top >= LZ4_MAX_DISTANCE_PAGES);
availables[top++] = rq->out[i - LZ4_MAX_DISTANCE_PAGES];
}
if (page) {
__clear_bit(j, bounced);
if (kaddr) {
if (kaddr + PAGE_SIZE == page_address(page))
kaddr += PAGE_SIZE;
else
kaddr = NULL;
} else if (!i) {
kaddr = page_address(page);
}
continue;
}
kaddr = NULL;
__set_bit(j, bounced);
if (top) {
victim = availables[--top];
get_page(victim);
} else {
victim = erofs_allocpage(pagepool, GFP_KERNEL, false);
if (!victim)
return -ENOMEM;
victim->mapping = Z_EROFS_MAPPING_STAGING;
}
rq->out[i] = victim;
}
return kaddr ? 1 : 0;
}
static void *generic_copy_inplace_data(struct z_erofs_decompress_req *rq,
u8 *src, unsigned int pageofs_in)
{
/*
* if in-place decompression is ongoing, those decompressed
* pages should be copied in order to avoid being overlapped.
*/
struct page **in = rq->in;
u8 *const tmp = erofs_get_pcpubuf(0);
u8 *tmpp = tmp;
unsigned int inlen = rq->inputsize - pageofs_in;
unsigned int count = min_t(uint, inlen, PAGE_SIZE - pageofs_in);
while (tmpp < tmp + inlen) {
if (!src)
src = kmap_atomic(*in);
memcpy(tmpp, src + pageofs_in, count);
kunmap_atomic(src);
src = NULL;
tmpp += count;
pageofs_in = 0;
count = PAGE_SIZE;
++in;
}
return tmp;
}
static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
{
unsigned int inputmargin, inlen;
u8 *src;
bool copied, support_0padding;
int ret;
if (rq->inputsize > PAGE_SIZE)
return -EOPNOTSUPP;
src = kmap_atomic(*rq->in);
inputmargin = 0;
support_0padding = false;
/* decompression inplace is only safe when 0padding is enabled */
if (EROFS_SB(rq->sb)->requirements & EROFS_REQUIREMENT_LZ4_0PADDING) {
support_0padding = true;
while (!src[inputmargin & ~PAGE_MASK])
if (!(++inputmargin & ~PAGE_MASK))
break;
if (inputmargin >= rq->inputsize) {
kunmap_atomic(src);
return -EIO;
}
}
copied = false;
inlen = rq->inputsize - inputmargin;
if (rq->inplace_io) {
const uint oend = (rq->pageofs_out +
rq->outputsize) & ~PAGE_MASK;
const uint nr = PAGE_ALIGN(rq->pageofs_out +
rq->outputsize) >> PAGE_SHIFT;
if (rq->partial_decoding || !support_0padding ||
rq->out[nr - 1] != rq->in[0] ||
rq->inputsize - oend <
LZ4_DECOMPRESS_INPLACE_MARGIN(inlen)) {
src = generic_copy_inplace_data(rq, src, inputmargin);
inputmargin = 0;
copied = true;
}
}
ret = LZ4_decompress_safe_partial(src + inputmargin, out,
inlen, rq->outputsize,
rq->outputsize);
if (ret < 0) {
errln("%s, failed to decompress, in[%p, %u, %u] out[%p, %u]",
__func__, src + inputmargin, inlen, inputmargin,
out, rq->outputsize);
WARN_ON(1);
print_hex_dump(KERN_DEBUG, "[ in]: ", DUMP_PREFIX_OFFSET,
16, 1, src + inputmargin, inlen, true);
print_hex_dump(KERN_DEBUG, "[out]: ", DUMP_PREFIX_OFFSET,
16, 1, out, rq->outputsize, true);
ret = -EIO;
}
if (copied)
erofs_put_pcpubuf(src);
else
kunmap_atomic(src);
return ret;
}
static struct z_erofs_decompressor decompressors[] = {
[Z_EROFS_COMPRESSION_SHIFTED] = {
.name = "shifted"
},
[Z_EROFS_COMPRESSION_LZ4] = {
.prepare_destpages = lz4_prepare_destpages,
.decompress = lz4_decompress,
.name = "lz4"
},
};
static void copy_from_pcpubuf(struct page **out, const char *dst,
unsigned short pageofs_out,
unsigned int outputsize)
{
const char *end = dst + outputsize;
const unsigned int righthalf = PAGE_SIZE - pageofs_out;
const char *cur = dst - pageofs_out;
while (cur < end) {
struct page *const page = *out++;
if (page) {
char *buf = kmap_atomic(page);
if (cur >= dst) {
memcpy(buf, cur, min_t(uint, PAGE_SIZE,
end - cur));
} else {
memcpy(buf + pageofs_out, cur + pageofs_out,
min_t(uint, righthalf, end - cur));
}
kunmap_atomic(buf);
}
cur += PAGE_SIZE;
}
}
static void *erofs_vmap(struct page **pages, unsigned int count)
{
int i = 0;
if (use_vmap)
return vmap(pages, count, VM_MAP, PAGE_KERNEL);
while (1) {
void *addr = vm_map_ram(pages, count, -1, PAGE_KERNEL);
/* retry two more times (totally 3 times) */
if (addr || ++i >= 3)
return addr;
vm_unmap_aliases();
}
return NULL;
}
static void erofs_vunmap(const void *mem, unsigned int count)
{
if (!use_vmap)
vm_unmap_ram(mem, count);
else
vunmap(mem);
}
static int decompress_generic(struct z_erofs_decompress_req *rq,
struct list_head *pagepool)
{
const unsigned int nrpages_out =
PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
const struct z_erofs_decompressor *alg = decompressors + rq->alg;
unsigned int dst_maptype;
void *dst;
int ret;
if (nrpages_out == 1 && !rq->inplace_io) {
DBG_BUGON(!*rq->out);
dst = kmap_atomic(*rq->out);
dst_maptype = 0;
goto dstmap_out;
}
/*
* For the case of small output size (especially much less
* than PAGE_SIZE), memcpy the decompressed data rather than
* compressed data is preferred.
*/
if (rq->outputsize <= PAGE_SIZE * 7 / 8) {
dst = erofs_get_pcpubuf(0);
if (IS_ERR(dst))
return PTR_ERR(dst);
rq->inplace_io = false;
ret = alg->decompress(rq, dst);
if (!ret)
copy_from_pcpubuf(rq->out, dst, rq->pageofs_out,
rq->outputsize);
erofs_put_pcpubuf(dst);
return ret;
}
ret = alg->prepare_destpages(rq, pagepool);
if (ret < 0) {
return ret;
} else if (ret) {
dst = page_address(*rq->out);
dst_maptype = 1;
goto dstmap_out;
}
dst = erofs_vmap(rq->out, nrpages_out);
if (!dst)
return -ENOMEM;
dst_maptype = 2;
dstmap_out:
ret = alg->decompress(rq, dst + rq->pageofs_out);
if (!dst_maptype)
kunmap_atomic(dst);
else if (dst_maptype == 2)
erofs_vunmap(dst, nrpages_out);
return ret;
}
static int shifted_decompress(const struct z_erofs_decompress_req *rq,
struct list_head *pagepool)
{
const unsigned int nrpages_out =
PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
const unsigned int righthalf = PAGE_SIZE - rq->pageofs_out;
unsigned char *src, *dst;
if (nrpages_out > 2) {
DBG_BUGON(1);
return -EIO;
}
if (rq->out[0] == *rq->in) {
DBG_BUGON(nrpages_out != 1);
return 0;
}
src = kmap_atomic(*rq->in);
if (!rq->out[0]) {
dst = NULL;
} else {
dst = kmap_atomic(rq->out[0]);
memcpy(dst + rq->pageofs_out, src, righthalf);
}
if (rq->out[1] == *rq->in) {
memmove(src, src + righthalf, rq->pageofs_out);
} else if (nrpages_out == 2) {
if (dst)
kunmap_atomic(dst);
DBG_BUGON(!rq->out[1]);
dst = kmap_atomic(rq->out[1]);
memcpy(dst, src + righthalf, rq->pageofs_out);
}
if (dst)
kunmap_atomic(dst);
kunmap_atomic(src);
return 0;
}
int z_erofs_decompress(struct z_erofs_decompress_req *rq,
struct list_head *pagepool)
{
if (rq->alg == Z_EROFS_COMPRESSION_SHIFTED)
return shifted_decompress(rq, pagepool);
return decompress_generic(rq, pagepool);
}