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SubjectRe: [PATCH v2 5/8] staging: erofs: introduce generic decompression backend
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On 2019/6/21 18:42, Gao Xiang wrote:
> Hi Chao,
>
> On 2019/6/21 17:46, Chao Yu wrote:
>> 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@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@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.
>
> It was written "on propose" since the problem is that currently __stagingpage_alloc()
> will allocate all pages in GFP_NOFAIL case, but memory allocation failure is accepted
> here, therefore I open code to aim at introducing new decompression backend.
>
> I will submit another patch after this series to clean up all staging page allocation
> cases later, which was already on my scheduling list. :)

Hi Xiang,

Yes, I noticed that there is something different in between __stagingpage_alloc
and opened codes, I think we can change __stagingpage_alloc to accept extra
parameters for different requirement.

But, anyway, I agreed with you that we can clean up with additional patch later. :)

Thanks,

>
> Thanks,
> Gao Xiang
>
>>
>> Reviewed-by: Chao Yu <yuchao0@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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