fs/erofs/decompressor.c - linux/kernel/git/gregkh/char-misc - Git at Google

 // 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 int z_erofs_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);
 			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 z_erofs_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)->feature_incompat &
 	    EROFS_FEATURE_INCOMPAT_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) {
 		erofs_err(rq->sb, "failed to decompress, in[%u, %u] out[%u]",
 			  inlen, inputmargin, 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 = z_erofs_lz4_prepare_destpages,
 		.decompress = z_erofs_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 z_erofs_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, i;

 	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;
 	}

 	i = 0;
 	while (1) {
 		dst = vm_map_ram(rq->out, nrpages_out, -1, PAGE_KERNEL);

 		/* retry two more times (totally 3 times) */
 		if (dst || ++i >= 3)
 			break;
 		vm_unmap_aliases();
 	}

 	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)
 		vm_unmap_ram(dst, nrpages_out);
 	return ret;
 }

 static int z_erofs_shifted_transform(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 = kmap_atomic(rq->out[0]);
 		memcpy(dst + rq->pageofs_out, src, righthalf);
 		kunmap_atomic(dst);
 	}

 	if (nrpages_out == 2) {
 		DBG_BUGON(!rq->out[1]);
 		if (rq->out[1] == *rq->in) {
 			memmove(src, src + righthalf, rq->pageofs_out);
 		} else {
 			dst = kmap_atomic(rq->out[1]);
 			memcpy(dst, src + righthalf, rq->pageofs_out);
 			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 z_erofs_shifted_transform(rq, pagepool);
 	return z_erofs_decompress_generic(rq, pagepool);
 }
	// 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 int z_erofs_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);
	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 z_erofs_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)->feature_incompat &
	EROFS_FEATURE_INCOMPAT_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) {
	erofs_err(rq->sb, "failed to decompress, in[%u, %u] out[%u]",
	inlen, inputmargin, 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 = z_erofs_lz4_prepare_destpages,
	.decompress = z_erofs_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 z_erofs_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, i;

	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;
	}

	i = 0;
	while (1) {
	dst = vm_map_ram(rq->out, nrpages_out, -1, PAGE_KERNEL);

	/* retry two more times (totally 3 times) */
	if (dst \|\| ++i >= 3)
	break;
	vm_unmap_aliases();
	}

	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)
	vm_unmap_ram(dst, nrpages_out);
	return ret;
	}

	static int z_erofs_shifted_transform(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 = kmap_atomic(rq->out[0]);
	memcpy(dst + rq->pageofs_out, src, righthalf);
	kunmap_atomic(dst);
	}

	if (nrpages_out == 2) {
	DBG_BUGON(!rq->out[1]);
	if (rq->out[1] == *rq->in) {
	memmove(src, src + righthalf, rq->pageofs_out);
	} else {
	dst = kmap_atomic(rq->out[1]);
	memcpy(dst, src + righthalf, rq->pageofs_out);
	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 z_erofs_shifted_transform(rq, pagepool);
	return z_erofs_decompress_generic(rq, pagepool);
	}