Re: [PATCH 6/9] f2fs: zstd: Switch to the zstd-1.4.6 API

Nick Terrell
2020-09-17T19:05:28Z

> On Sep 16, 2020, at 11:31 PM, Chao Yu <yuchao0@huawei.com> wrote:
>
> Hi Nick,
>
> On 2020/9/17 2:39, Nick Terrell wrote:
>>> On Sep 15, 2020, at 11:31 PM, Chao Yu <yuchao0@huawei.com> wrote:
>>>
>>> Hi Nick,
>>>
>>> remove not related mailing list.
>>>
>>> On 2020/9/16 11:43, Nick Terrell wrote:
>>>> From: Nick Terrell <terrelln@fb.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'}`

Probably, but it was just a quick one-off script.

> 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?

The /tmp/silesia directory in the example is populated with all the files from
this website. It is a popular data compression benchmark corpus. You can
click on the “total” link to download a zip archive of all the files.

http://sun.aei.polsl.pl/~sdeor/index.php?page=silesia

-Nick

> Thanks,
>
>> Best,
>> Nick
>>> Thanks,
>>>
>>>> Signed-off-by: Nick Terrell <terrelln@fb.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,