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Commit 7fc45dbc authored by Gao Xiang's avatar Gao Xiang Committed by Greg Kroah-Hartman
Browse files

staging: erofs: introduce generic decompression backend 



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.

Reviewed-by: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarGao Xiang <gaoxiang25@huawei.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 27481233

drivers/staging/erofs/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

drivers/staging/erofs/compress.h

+21 −0
Original line number Diff line number Diff line
@@ -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

drivers/staging/erofs/decompressor.c

0 → 100644
+301 −0
Original line number Diff line number Diff line 
// 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);

				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;

		}

		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;



	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);

		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);

}