Date:   Thu, 17 Sep 2020 14:31:57 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Nick Terrell <terrelln@...com>
CC:     Nick Terrell <nickrterrell@...il.com>,
        "linux-f2fs-devel@...ts.sourceforge.net" 
        <linux-f2fs-devel@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>, Chris Mason <clm@...com>,
        Petr Malat <oss@...at.biz>, Johannes Weiner <jweiner@...com>,
        Niket Agarwal <niketa@...com>, Yann Collet <cyan@...com>
Subject: Re: [PATCH 6/9] f2fs: zstd: Switch to the zstd-1.4.6 API

Hi Nick,

On 2020/9/17 2:39, Nick Terrell wrote:
> 
> 
>> On Sep 15, 2020, at 11:31 PM, Chao Yu <yuchao0@...wei.com> wrote:
>>
>> Hi Nick,
>>
>> remove not related mailing list.
>>
>> On 2020/9/16 11:43, Nick Terrell wrote:
>>> From: Nick Terrell <terrelln@...com>
>>> Move away from the compatibility wrapper to the zstd-1.4.6 API. This
>>> code is more efficient because it uses the single-pass API instead of
>>> the streaming API. The streaming API is not necessary because the whole
>>> input and output buffers are available. This saves memory because we
>>> don't need to allocate a buffer for the window. It is also more
>>> efficient because it saves unnecessary memcpy calls.
>>> I've had problems testing this code because I see data truncation before
>>> and after this patchset. Help testing this patch would be much
>>> appreciated.
>>
>> Can you please explain more about data truncation? I'm a little confused...
>>
>> Do you mean that f2fs doesn't allocate enough memory for zstd compression,
>> so that compression is not finished actually, the compressed data is truncated
>> at dst buffer?
> 
> Hi Chao,
> 
> I’ve tested F2FS using a benchmark I adapted from testing BtrFS [0]. It is possible
> that the script I’m using is buggy or is exposing an edge case in F2FS. The files
> that I copy to F2FS and compress end up truncated with a hole at the end.

Thanks for your explanation. :)

> 
> It is based off of upstream commit ab29a807a7.
> 
> E.g. the end of the copied file looks like this, but the original file has non-zero data
> In the end. Until the hole at the end the file is correct.
> 
> od dickens | tail -n 5
>> 46667760 067502 066167 020056 040440 020163 023511 006555 060412
>> 46670000 000000 000000 000000 000000 000000 000000 000000 000000
>> *
>> 46703060 000000 000000 000000 000000 000000 000000 000000
>> 46703076
> 
> [0] https://gist.github.com/terrelln/7dd2919937dfbdb8e839e4ad11c81db4

Shouldn't we just get sha1 value by flitering sha1sum output?

                 asha=`sha1sum $BENCHMARK_DIR/$file |awk {'print $1'}`
                 bsha=`sha1sum $MP/$i/$file |awk {'print $1'}`

I can't reproduce this issue by using simple data sample, could you share
that 'dickens' file or other smaller-sized sample if you have?

Thanks,

> 
> Best,
> Nick
> 
>> Thanks,
>>
>>> Signed-off-by: Nick Terrell <terrelln@...com>
>>> ---
>>>   fs/f2fs/compress.c | 102 +++++++++++++++++----------------------------
>>>   1 file changed, 38 insertions(+), 64 deletions(-)
>>> diff --git a/fs/f2fs/compress.c b/fs/f2fs/compress.c
>>> index e056f3a2b404..b79efce81651 100644
>>> --- a/fs/f2fs/compress.c
>>> +++ b/fs/f2fs/compress.c
>>> @@ -11,7 +11,8 @@
>>>   #include <linux/backing-dev.h>
>>>   #include <linux/lzo.h>
>>>   #include <linux/lz4.h>
>>> -#include <linux/zstd_compat.h>
>>> +#include <linux/zstd.h>
>>> +#include <linux/zstd_errors.h>
>>>     #include "f2fs.h"
>>>   #include "node.h"
>>> @@ -298,21 +299,21 @@ static const struct f2fs_compress_ops f2fs_lz4_ops = {
>>>   static int zstd_init_compress_ctx(struct compress_ctx *cc)
>>>   {
>>>   	ZSTD_parameters params;
>>> -	ZSTD_CStream *stream;
>>> +	ZSTD_CCtx *ctx;
>>>   	void *workspace;
>>>   	unsigned int workspace_size;
>>>     	params = ZSTD_getParams(F2FS_ZSTD_DEFAULT_CLEVEL, cc->rlen, 0);
>>> -	workspace_size = ZSTD_CStreamWorkspaceBound(params.cParams);
>>> +	workspace_size = ZSTD_estimateCCtxSize_usingCParams(params.cParams);
>>>     	workspace = f2fs_kvmalloc(F2FS_I_SB(cc->inode),
>>>   					workspace_size, GFP_NOFS);
>>>   	if (!workspace)
>>>   		return -ENOMEM;
>>>   -	stream = ZSTD_initCStream(params, 0, workspace, workspace_size);
>>> -	if (!stream) {
>>> -		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_initCStream failed\n",
>>> +	ctx = ZSTD_initStaticCCtx(workspace, workspace_size);
>>> +	if (!ctx) {
>>> +		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_inittaticCStream failed\n",
>>>   				KERN_ERR, F2FS_I_SB(cc->inode)->sb->s_id,
>>>   				__func__);
>>>   		kvfree(workspace);
>>> @@ -320,7 +321,7 @@ static int zstd_init_compress_ctx(struct compress_ctx *cc)
>>>   	}
>>>     	cc->private = workspace;
>>> -	cc->private2 = stream;
>>> +	cc->private2 = ctx;
>>>     	cc->clen = cc->rlen - PAGE_SIZE - COMPRESS_HEADER_SIZE;
>>>   	return 0;
>>> @@ -335,65 +336,48 @@ static void zstd_destroy_compress_ctx(struct compress_ctx *cc)
>>>     static int zstd_compress_pages(struct compress_ctx *cc)
>>>   {
>>> -	ZSTD_CStream *stream = cc->private2;
>>> -	ZSTD_inBuffer inbuf;
>>> -	ZSTD_outBuffer outbuf;
>>> -	int src_size = cc->rlen;
>>> -	int dst_size = src_size - PAGE_SIZE - COMPRESS_HEADER_SIZE;
>>> -	int ret;
>>> -
>>> -	inbuf.pos = 0;
>>> -	inbuf.src = cc->rbuf;
>>> -	inbuf.size = src_size;
>>> -
>>> -	outbuf.pos = 0;
>>> -	outbuf.dst = cc->cbuf->cdata;
>>> -	outbuf.size = dst_size;
>>> -
>>> -	ret = ZSTD_compressStream(stream, &outbuf, &inbuf);
>>> -	if (ZSTD_isError(ret)) {
>>> -		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_compressStream failed, ret: %d\n",
>>> -				KERN_ERR, F2FS_I_SB(cc->inode)->sb->s_id,
>>> -				__func__, ZSTD_getErrorCode(ret));
>>> -		return -EIO;
>>> -	}
>>> -
>>> -	ret = ZSTD_endStream(stream, &outbuf);
>>> +	ZSTD_CCtx *ctx = cc->private2;
>>> +	const size_t src_size = cc->rlen;
>>> +	const size_t dst_size = src_size - PAGE_SIZE - COMPRESS_HEADER_SIZE;
>>> +	ZSTD_parameters params = ZSTD_getParams(F2FS_ZSTD_DEFAULT_CLEVEL, src_size, 0);
>>> +	size_t ret;
>>> +
>>> +	ret = ZSTD_compress_advanced(
>>> +			ctx, cc->cbuf->cdata, dst_size, cc->rbuf, src_size, NULL, 0, params);
>>>   	if (ZSTD_isError(ret)) {
>>> -		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_endStream returned %d\n",
>>> +		/*
>>> +		 * there is compressed data remained in intermediate buffer due to
>>> +		 * no more space in cbuf.cdata
>>> +		 */
>>> +		if (ZSTD_getErrorCode(ret) == ZSTD_error_dstSize_tooSmall)
>>> +			return -EAGAIN;
>>> +		/* other compression errors return -EIO */
>>> +		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_compress_advanced failed, err: %s\n",
>>>   				KERN_ERR, F2FS_I_SB(cc->inode)->sb->s_id,
>>> -				__func__, ZSTD_getErrorCode(ret));
>>> +				__func__, ZSTD_getErrorName(ret));
>>>   		return -EIO;
>>>   	}
>>>   -	/*
>>> -	 * there is compressed data remained in intermediate buffer due to
>>> -	 * no more space in cbuf.cdata
>>> -	 */
>>> -	if (ret)
>>> -		return -EAGAIN;
>>> -
>>> -	cc->clen = outbuf.pos;
>>> +	cc->clen = ret;
>>>   	return 0;
>>>   }
>>>     static int zstd_init_decompress_ctx(struct decompress_io_ctx *dic)
>>>   {
>>> -	ZSTD_DStream *stream;
>>> +	ZSTD_DCtx *ctx;
>>>   	void *workspace;
>>>   	unsigned int workspace_size;
>>>   -	workspace_size = ZSTD_DStreamWorkspaceBound(MAX_COMPRESS_WINDOW_SIZE);
>>> +	workspace_size = ZSTD_estimateDCtxSize();
>>>     	workspace = f2fs_kvmalloc(F2FS_I_SB(dic->inode),
>>>   					workspace_size, GFP_NOFS);
>>>   	if (!workspace)
>>>   		return -ENOMEM;
>>>   -	stream = ZSTD_initDStream(MAX_COMPRESS_WINDOW_SIZE,
>>> -					workspace, workspace_size);
>>> -	if (!stream) {
>>> -		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_initDStream failed\n",
>>> +	ctx = ZSTD_initStaticDCtx(workspace, workspace_size);
>>> +	if (!ctx) {
>>> +		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_initStaticDCtx failed\n",
>>>   				KERN_ERR, F2FS_I_SB(dic->inode)->sb->s_id,
>>>   				__func__);
>>>   		kvfree(workspace);
>>> @@ -401,7 +385,7 @@ static int zstd_init_decompress_ctx(struct decompress_io_ctx *dic)
>>>   	}
>>>     	dic->private = workspace;
>>> -	dic->private2 = stream;
>>> +	dic->private2 = ctx;
>>>     	return 0;
>>>   }
>>> @@ -415,28 +399,18 @@ static void zstd_destroy_decompress_ctx(struct decompress_io_ctx *dic)
>>>     static int zstd_decompress_pages(struct decompress_io_ctx *dic)
>>>   {
>>> -	ZSTD_DStream *stream = dic->private2;
>>> -	ZSTD_inBuffer inbuf;
>>> -	ZSTD_outBuffer outbuf;
>>> -	int ret;
>>> -
>>> -	inbuf.pos = 0;
>>> -	inbuf.src = dic->cbuf->cdata;
>>> -	inbuf.size = dic->clen;
>>> -
>>> -	outbuf.pos = 0;
>>> -	outbuf.dst = dic->rbuf;
>>> -	outbuf.size = dic->rlen;
>>> +	ZSTD_DCtx *ctx = dic->private2;
>>> +	size_t ret;
>>>   -	ret = ZSTD_decompressStream(stream, &outbuf, &inbuf);
>>> +	ret = ZSTD_decompressDCtx(ctx, dic->rbuf, dic->rlen, dic->cbuf->cdata, dic->clen);
>>>   	if (ZSTD_isError(ret)) {
>>> -		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_compressStream failed, ret: %d\n",
>>> +		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD_decompressDCtx failed, err: %s\n",
>>>   				KERN_ERR, F2FS_I_SB(dic->inode)->sb->s_id,
>>> -				__func__, ZSTD_getErrorCode(ret));
>>> +				__func__, ZSTD_getErrorName(ret));
>>>   		return -EIO;
>>>   	}
>>>   -	if (dic->rlen != outbuf.pos) {
>>> +	if (dic->rlen != ret) {
>>>   		printk_ratelimited("%sF2FS-fs (%s): %s ZSTD invalid rlen:%zu, "
>>>   				"expected:%lu\n", KERN_ERR,
>>>   				F2FS_I_SB(dic->inode)->sb->s_id,
> 

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