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    Subject[RFC PATCH 5/8] staging: erofs: introduce generic decompression backend
    Date
    This patch adds a new generic decompression framework
    in order to replace the old LZ4-specific decompression code.

    Even though LZ4 is still the only supported algorithm, yet
    it is more cleaner and easy to integrate new algorithm than
    the old almost hard-coded decompression backend.

    Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
    ---
    drivers/staging/erofs/Makefile | 2 +-
    drivers/staging/erofs/compress.h | 21 ++
    drivers/staging/erofs/decompressor.c | 306 +++++++++++++++++++++++++++
    3 files changed, 328 insertions(+), 1 deletion(-)
    create mode 100644 drivers/staging/erofs/decompressor.c

    diff --git a/drivers/staging/erofs/Makefile b/drivers/staging/erofs/Makefile
    index 84b412c7a991..adeb5d6e2668 100644
    --- a/drivers/staging/erofs/Makefile
    +++ b/drivers/staging/erofs/Makefile
    @@ -9,5 +9,5 @@ obj-$(CONFIG_EROFS_FS) += erofs.o
    ccflags-y += -I $(srctree)/$(src)/include
    erofs-objs := super.o inode.o data.o namei.o dir.o utils.o
    erofs-$(CONFIG_EROFS_FS_XATTR) += xattr.o
    -erofs-$(CONFIG_EROFS_FS_ZIP) += unzip_vle.o unzip_vle_lz4.o zmap.o
    +erofs-$(CONFIG_EROFS_FS_ZIP) += unzip_vle.o unzip_vle_lz4.o zmap.o decompressor.o

    diff --git a/drivers/staging/erofs/compress.h b/drivers/staging/erofs/compress.h
    index 1dcfc3b35118..ebeccb1f4eae 100644
    --- a/drivers/staging/erofs/compress.h
    +++ b/drivers/staging/erofs/compress.h
    @@ -9,6 +9,24 @@
    #ifndef __EROFS_FS_COMPRESS_H
    #define __EROFS_FS_COMPRESS_H

    +#include "internal.h"
    +
    +enum {
    + Z_EROFS_COMPRESSION_SHIFTED = Z_EROFS_COMPRESSION_MAX,
    + Z_EROFS_COMPRESSION_RUNTIME_MAX
    +};
    +
    +struct z_erofs_decompress_req {
    + struct page **in, **out;
    +
    + unsigned short pageofs_out;
    + unsigned int inputsize, outputsize;
    +
    + /* indicate the algorithm will be used for decompression */
    + unsigned int alg;
    + bool inplace_io, partial_decoding;
    +};
    +
    /*
    * - 0x5A110C8D ('sallocated', Z_EROFS_MAPPING_STAGING) -
    * used to mark temporary allocated pages from other
    @@ -36,5 +54,8 @@ static inline bool z_erofs_put_stagingpage(struct list_head *pagepool,
    return true;
    }

    +int z_erofs_decompress(struct z_erofs_decompress_req *rq,
    + struct list_head *pagepool);
    +
    #endif

    diff --git a/drivers/staging/erofs/decompressor.c b/drivers/staging/erofs/decompressor.c
    new file mode 100644
    index 000000000000..4f644bdea0bc
    --- /dev/null
    +++ b/drivers/staging/erofs/decompressor.c
    @@ -0,0 +1,306 @@
    +// SPDX-License-Identifier: GPL-2.0
    +/*
    + * linux/drivers/staging/erofs/decompressor.c
    + *
    + * Copyright (C) 2019 HUAWEI, Inc.
    + * http://www.huawei.com/
    + * Created by Gao Xiang <gaoxiang25@huawei.com>
    + */
    +#include "compress.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)
    +
    +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 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 unused[DIV_ROUND_UP(LZ4_MAX_DISTANCE_PAGES,
    + BITS_PER_LONG)] = { 0 };
    + void *kaddr = NULL;
    + unsigned int i, j, k;
    +
    + for (i = 0; i < nr; ++i) {
    + struct page *const page = rq->out[i];
    +
    + j = i & (LZ4_MAX_DISTANCE_PAGES - 1);
    + if (availables[j])
    + __set_bit(j, unused);
    +
    + if (page) {
    + 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;
    +
    + k = find_first_bit(unused, LZ4_MAX_DISTANCE_PAGES);
    + if (k < LZ4_MAX_DISTANCE_PAGES) {
    + j = k;
    + get_page(availables[j]);
    + } else {
    + DBG_BUGON(availables[j]);
    +
    + if (!list_empty(pagepool)) {
    + availables[j] = lru_to_page(pagepool);
    + list_del(&availables[j]->lru);
    + } else {
    + availables[j] = alloc_pages(GFP_KERNEL, 0);
    + if (!availables[j])
    + return -ENOMEM;
    + }
    + availables[j]->mapping = Z_EROFS_MAPPING_STAGING;
    + }
    + rq->out[i] = availables[j];
    + __clear_bit(j, unused);
    + }
    + 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;
    + void *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 (inlen) {
    + if (!src)
    + src = kmap_atomic(*in++);
    + memcpy(tmpp, src + pageofs_in, count);
    + kunmap_atomic(src);
    + src = NULL;
    + inlen -= count;
    + tmpp += count;
    + pageofs_in = 0;
    + count = PAGE_SIZE;
    + }
    + return tmp;
    +}
    +
    +static int lz4_decompress(struct z_erofs_decompress_req *rq, u8 *out)
    +{
    + unsigned int inputmargin, inlen;
    + u8 *src;
    + bool copied;
    + int ret;
    +
    + if (rq->inputsize > PAGE_SIZE)
    + return -ENOTSUPP;
    +
    + src = kmap_atomic(*rq->in);
    + inputmargin = 0;
    + 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) {
    + 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 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);
    +
    + 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);
    +}
    +
    --
    2.17.1
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      Last update: 2019-06-14 20:18    [W:4.045 / U:0.580 seconds]
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