[PATCH v2 5/8] staging: erofs: introduce generic decompression backend
Chao Yu
yuchao0 at huawei.com
Fri Jun 21 09:46:50 UTC 2019
On 2019/6/21 0:07, Gao Xiang wrote:
> 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 at huawei.com>
> ---
> drivers/staging/erofs/Makefile | 2 +-
> drivers/staging/erofs/compress.h | 21 ++
> drivers/staging/erofs/decompressor.c | 307 +++++++++++++++++++++++++++
> 3 files changed, 329 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..c68d17b579e0
> --- /dev/null
> +++ b/drivers/staging/erofs/decompressor.c
> @@ -0,0 +1,307 @@
> +// 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 at 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);
> + DBG_BUGON(page_ref_count(availables[j]) != 1);
> + } else {
> + availables[j] = alloc_pages(GFP_KERNEL, 0);
> + if (!availables[j])
> + return -ENOMEM;
> + }
> + availables[j]->mapping = Z_EROFS_MAPPING_STAGING;
Could we use __stagingpage_alloc() instead opened codes, there is something
different in between them though.
Reviewed-by: Chao Yu <yuchao0 at huawei.com>
Thanks,
> + }
> + 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;
> + 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;
> + 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);
> +}
> +
>
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