Re: [PATCH v3 8/9] zram: use crypto API for compression

[Minchan Kim <minchan@kernel.org>]

Hi Joonsoo,

On Fri, Sep 18, 2015 at 02:19:23PM +0900, Joonsoo Kim wrote:
> Until now, zram uses compression algorithm through direct call
> to core algorithm function, but, it has drawback that we need to add
> compression algorithm manually to zram if needed. Without this work,
> we cannot utilize various compression algorithms in the system.
> Moreover, to add new compression algorithm, we need to know how to use it
> and this is somewhat time-consuming.
> 
> When I tested new algorithms such as zlib, these problems make me hard
> to test them. To prevent these problem in the future, I think that
> using crypto API for compression is better approach and this patch
> implements it.
> 
> The reason we need to support vairous compression algorithms is that
> zram's performance is highly depend on workload and compression algorithm
> and architecture. Every compression algorithm has it's own strong point.
> For example, zlib is the best for compression ratio, but, it's
> (de)compression speed is rather slow. Against my expectation, in my kernel
> build test with zram swap, in low-memory condition on x86, zlib shows best
> performance than others. In this case, I guess that compression ratio is
> the most important factor. Unlike this situation, on ARM, maybe fast
> (de)compression speed is the most important because it's computation speed
> is slower than x86.
> 
> We can't expect what algorithm is the best fit for one's system, because
> it needs too complex calculation. We need to test it in case by case and
> easy to use new compression algorithm by this patch will help
> that situation.
> 
> There is one problem that crypto API requires tfm object to (de)compress
> something and zram abstract it on zstrm which is very limited resource.
> If number of zstrm is set to low and is contended, zram's performace could
> be down-graded due to this change. But, following patch support to use
> crypto decompress_noctx API and would restore the performance as is.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> ---
>  drivers/block/zram/Kconfig     |  8 +++----
>  drivers/block/zram/Makefile    |  4 +---
>  drivers/block/zram/zcomp.c     | 54 +++++++++++++++++++++++-------------------
>  drivers/block/zram/zcomp.h     | 30 ++++++-----------------
>  drivers/block/zram/zcomp_lz4.c | 47 ------------------------------------
>  drivers/block/zram/zcomp_lz4.h | 17 -------------
>  drivers/block/zram/zcomp_lzo.c | 47 ------------------------------------
>  drivers/block/zram/zcomp_lzo.h | 17 -------------
>  drivers/block/zram/zram_drv.c  |  6 ++---
>  9 files changed, 44 insertions(+), 186 deletions(-)
>  delete mode 100644 drivers/block/zram/zcomp_lz4.c
>  delete mode 100644 drivers/block/zram/zcomp_lz4.h
>  delete mode 100644 drivers/block/zram/zcomp_lzo.c
>  delete mode 100644 drivers/block/zram/zcomp_lzo.h
> 
> diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig
> index 386ba3d..7619bed 100644
> --- a/drivers/block/zram/Kconfig
> +++ b/drivers/block/zram/Kconfig
> @@ -1,8 +1,7 @@
>  config ZRAM
>  	tristate "Compressed RAM block device support"
>  	depends on BLOCK && SYSFS && ZSMALLOC
> -	select LZO_COMPRESS
> -	select LZO_DECOMPRESS
> +	select CRYPTO_LZO
>  	default n
>  	help
>  	  Creates virtual block devices called /dev/zramX (X = 0, 1, ...).
> @@ -18,9 +17,8 @@ config ZRAM
>  config ZRAM_LZ4_COMPRESS
>  	bool "Enable LZ4 algorithm support"
>  	depends on ZRAM
> -	select LZ4_COMPRESS
> -	select LZ4_DECOMPRESS
> +	select CRYPTO_LZ4

It is out of my expectation.

When I heard crypto support for zRAM first, I imagined zram user can
use any crypto compressor algorithm easily if system has the algorithm.
IOW, I expect zRAM shouldn't bind CONFIG_CRYPTO_ALGONAME statically
except the default one(ie, CONFIG_CRYPTO_LZO) like zswap and It seems
you did in eariler version.

You seem to have a trouble to adapt crypto to current comp_algorithm
because crypto doesn't export any API to enumerate algorithm name
while zram should export supporting algorithm name via comp_algorithm
and I heard crypto maintainer doesn't want to export it. Instead,
user can use /proc/crypto to know what kinds of compressor system
can support.

Hmm,
At the first glance, I was about to say "let's sort it out with
futher patches" but I changed my mind. ;-).

We should sort it out before you are adding zlib support(ie, please
include zlib support patch with number data in this patchset). Otherwise,
we should add new hard-wired stuff for zlib like lzo, lz4 to
comp_algorithm and will depreate soon.

My idea is ABI change of comp_algorithm. Namely, let's deprecate it
and guide to use /proc/crypto to show available compressor.
Someday, we removes backends string array finally.

Welcome to any ideas.

>  	default n
>  	help
>  	  This option enables LZ4 compression algorithm support. Compression
> -	  algorithm can be changed using `comp_algorithm' device attribute.
> \ No newline at end of file
> +	  algorithm can be changed using `comp_algorithm' device attribute.
> diff --git a/drivers/block/zram/Makefile b/drivers/block/zram/Makefile
> index be0763f..9e2b79e 100644
> --- a/drivers/block/zram/Makefile
> +++ b/drivers/block/zram/Makefile
> @@ -1,5 +1,3 @@
> -zram-y	:=	zcomp_lzo.o zcomp.o zram_drv.o
> -
> -zram-$(CONFIG_ZRAM_LZ4_COMPRESS) += zcomp_lz4.o
> +zram-y	:=	zcomp.o zram_drv.o
>  
>  obj-$(CONFIG_ZRAM)	+=	zram.o
> diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> index 3456d5a..c2ed7c8 100644
> --- a/drivers/block/zram/zcomp.c
> +++ b/drivers/block/zram/zcomp.c
> @@ -15,10 +15,6 @@
>  #include <linux/sched.h>
>  
>  #include "zcomp.h"
> -#include "zcomp_lzo.h"
> -#ifdef CONFIG_ZRAM_LZ4_COMPRESS
> -#include "zcomp_lz4.h"
> -#endif
>  
>  /*
>   * single zcomp_strm backend
> @@ -43,19 +39,20 @@ struct zcomp_strm_multi {
>  	wait_queue_head_t strm_wait;
>  };
>  
> -static struct zcomp_backend *backends[] = {
> -	&zcomp_lzo,
> +static const char * const backends[] = {
> +	"lzo",
>  #ifdef CONFIG_ZRAM_LZ4_COMPRESS
> -	&zcomp_lz4,
> +	"lz4",
>  #endif
>  	NULL
>  };
>  
> -static struct zcomp_backend *find_backend(const char *compress)
> +static const char *find_backend(const char *compress)
>  {
>  	int i = 0;
>  	while (backends[i]) {
> -		if (sysfs_streq(compress, backends[i]->name))
> +		if (sysfs_streq(compress, backends[i]) &&
> +			crypto_has_comp(compress, 0, 0))
>  			break;
>  		i++;
>  	}
> @@ -64,8 +61,8 @@ static struct zcomp_backend *find_backend(const char *compress)
>  
>  static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
>  {
> -	if (zstrm->private)
> -		comp->backend->destroy(zstrm->private);
> +	if (zstrm->tfm)
> +		crypto_free_comp(zstrm->tfm);
>  	free_pages((unsigned long)zstrm->buffer, 1);
>  	kfree(zstrm);
>  }
> @@ -80,13 +77,18 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
>  	if (!zstrm)
>  		return NULL;
>  
> -	zstrm->private = comp->backend->create();
> +	zstrm->tfm = crypto_alloc_comp(comp->backend, 0, 0);
> +	if (IS_ERR(zstrm->tfm)) {
> +		kfree(zstrm);
> +		return NULL;
> +	}
> +
>  	/*
>  	 * allocate 2 pages. 1 for compressed data, plus 1 extra for the
>  	 * case when compressed size is larger than the original one
>  	 */
>  	zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
> -	if (!zstrm->private || !zstrm->buffer) {
> +	if (!zstrm->buffer) {
>  		zcomp_strm_free(comp, zstrm);
>  		zstrm = NULL;
>  	}
> @@ -274,12 +276,12 @@ ssize_t zcomp_available_show(const char *comp, char *buf)
>  	int i = 0;
>  
>  	while (backends[i]) {
> -		if (!strcmp(comp, backends[i]->name))
> +		if (!strcmp(comp, backends[i]))
>  			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
> -					"[%s] ", backends[i]->name);
> +					"[%s] ", backends[i]);
>  		else
>  			sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
> -					"%s ", backends[i]->name);
> +					"%s ", backends[i]);
>  		i++;
>  	}
>  	sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
> @@ -317,10 +319,10 @@ void zcomp_compress_end(struct zcomp *comp, struct zcomp_strm *zstrm)
>  	zcomp_strm_release(comp, zstrm);
>  }
>  
> -/* May return NULL, may sleep */
> +/* Never return NULL, may sleep */
>  struct zcomp_strm *zcomp_decompress_begin(struct zcomp *comp)
>  {
> -	return NULL;
> +	return zcomp_strm_find(comp);
>  }
>  
>  void zcomp_decompress_end(struct zcomp *comp, struct zcomp_strm *zstrm)
> @@ -330,17 +332,21 @@ void zcomp_decompress_end(struct zcomp *comp, struct zcomp_strm *zstrm)
>  }
>  
>  int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
> -		const unsigned char *src, size_t *dst_len)
> +		const unsigned char *src, unsigned int *dst_len)
>  {
> -	return comp->backend->compress(src, zstrm->buffer, dst_len,
> -			zstrm->private);
> +	*dst_len = PAGE_SIZE << 1;
> +
> +	return crypto_comp_compress(zstrm->tfm, src, PAGE_SIZE,
> +					zstrm->buffer, dst_len);
>  }
>  
>  int zcomp_decompress(struct zcomp *comp, struct zcomp_strm *zstrm,
>  		const unsigned char *src,
> -		size_t src_len, unsigned char *dst)
> +		unsigned int src_len, unsigned char *dst)
>  {
> -	return comp->backend->decompress(src, src_len, dst);
> +	unsigned int size = PAGE_SIZE;
> +
> +	return crypto_comp_decompress(zstrm->tfm, src, src_len,	dst, &size);
>  }
>  
>  void zcomp_destroy(struct zcomp *comp)
> @@ -359,7 +365,7 @@ void zcomp_destroy(struct zcomp *comp)
>  struct zcomp *zcomp_create(const char *compress, int max_strm)
>  {
>  	struct zcomp *comp;
> -	struct zcomp_backend *backend;
> +	const char *backend;
>  
>  	backend = find_backend(compress);
>  	if (!backend)
> diff --git a/drivers/block/zram/zcomp.h b/drivers/block/zram/zcomp.h
> index 4c09c01..4f9df8e 100644
> --- a/drivers/block/zram/zcomp.h
> +++ b/drivers/block/zram/zcomp.h
> @@ -11,38 +11,22 @@
>  #define _ZCOMP_H_
>  
>  #include <linux/mutex.h>
> +#include <linux/crypto.h>
>  
>  struct zcomp_strm {
> +	struct crypto_comp *tfm;
> +
>  	/* compression/decompression buffer */
>  	void *buffer;
> -	/*
> -	 * The private data of the compression stream, only compression
> -	 * stream backend can touch this (e.g. compression algorithm
> -	 * working memory)
> -	 */
> -	void *private;
> +
>  	/* used in multi stream backend, protected by backend strm_lock */
>  	struct list_head list;
>  };
>  
> -/* static compression backend */
> -struct zcomp_backend {
> -	int (*compress)(const unsigned char *src, unsigned char *dst,
> -			size_t *dst_len, void *private);
> -
> -	int (*decompress)(const unsigned char *src, size_t src_len,
> -			unsigned char *dst);
> -
> -	void *(*create)(void);
> -	void (*destroy)(void *private);
> -
> -	const char *name;
> -};
> -
>  /* dynamic per-device compression frontend */
>  struct zcomp {
>  	void *stream;
> -	struct zcomp_backend *backend;
> +	const char *backend;
>  
>  	struct zcomp_strm *(*strm_find)(struct zcomp *comp);
>  	void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);
> @@ -61,14 +45,14 @@ struct zcomp_strm *zcomp_compress_begin(struct zcomp *comp);
>  void zcomp_compress_end(struct zcomp *comp, struct zcomp_strm *zstrm);
>  
>  int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
> -		const unsigned char *src, size_t *dst_len);
> +		const unsigned char *src, unsigned int *dst_len);
>  
>  struct zcomp_strm *zcomp_decompress_begin(struct zcomp *comp);
>  void zcomp_decompress_end(struct zcomp *comp, struct zcomp_strm *zstrm);
>  
>  int zcomp_decompress(struct zcomp *comp, struct zcomp_strm *zstrm,
>  		const unsigned char *src,
> -		size_t src_len, unsigned char *dst);
> +		unsigned int src_len, unsigned char *dst);
>  
>  bool zcomp_set_max_streams(struct zcomp *comp, int num_strm);
>  #endif /* _ZCOMP_H_ */
> diff --git a/drivers/block/zram/zcomp_lz4.c b/drivers/block/zram/zcomp_lz4.c
> deleted file mode 100644
> index f2afb7e..0000000
> --- a/drivers/block/zram/zcomp_lz4.c
> +++ /dev/null
> @@ -1,47 +0,0 @@
> -/*
> - * Copyright (C) 2014 Sergey Senozhatsky.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License
> - * as published by the Free Software Foundation; either version
> - * 2 of the License, or (at your option) any later version.
> - */
> -
> -#include <linux/kernel.h>
> -#include <linux/slab.h>
> -#include <linux/lz4.h>
> -
> -#include "zcomp_lz4.h"
> -
> -static void *zcomp_lz4_create(void)
> -{
> -	return kzalloc(LZ4_MEM_COMPRESS, GFP_KERNEL);
> -}
> -
> -static void zcomp_lz4_destroy(void *private)
> -{
> -	kfree(private);
> -}
> -
> -static int zcomp_lz4_compress(const unsigned char *src, unsigned char *dst,
> -		size_t *dst_len, void *private)
> -{
> -	/* return  : Success if return 0 */
> -	return lz4_compress(src, PAGE_SIZE, dst, dst_len, private);
> -}
> -
> -static int zcomp_lz4_decompress(const unsigned char *src, size_t src_len,
> -		unsigned char *dst)
> -{
> -	size_t dst_len = PAGE_SIZE;
> -	/* return  : Success if return 0 */
> -	return lz4_decompress_unknownoutputsize(src, src_len, dst, &dst_len);
> -}
> -
> -struct zcomp_backend zcomp_lz4 = {
> -	.compress = zcomp_lz4_compress,
> -	.decompress = zcomp_lz4_decompress,
> -	.create = zcomp_lz4_create,
> -	.destroy = zcomp_lz4_destroy,
> -	.name = "lz4",
> -};
> diff --git a/drivers/block/zram/zcomp_lz4.h b/drivers/block/zram/zcomp_lz4.h
> deleted file mode 100644
> index 60613fb..0000000
> --- a/drivers/block/zram/zcomp_lz4.h
> +++ /dev/null
> @@ -1,17 +0,0 @@
> -/*
> - * Copyright (C) 2014 Sergey Senozhatsky.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License
> - * as published by the Free Software Foundation; either version
> - * 2 of the License, or (at your option) any later version.
> - */
> -
> -#ifndef _ZCOMP_LZ4_H_
> -#define _ZCOMP_LZ4_H_
> -
> -#include "zcomp.h"
> -
> -extern struct zcomp_backend zcomp_lz4;
> -
> -#endif /* _ZCOMP_LZ4_H_ */
> diff --git a/drivers/block/zram/zcomp_lzo.c b/drivers/block/zram/zcomp_lzo.c
> deleted file mode 100644
> index da1bc47..0000000
> --- a/drivers/block/zram/zcomp_lzo.c
> +++ /dev/null
> @@ -1,47 +0,0 @@
> -/*
> - * Copyright (C) 2014 Sergey Senozhatsky.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License
> - * as published by the Free Software Foundation; either version
> - * 2 of the License, or (at your option) any later version.
> - */
> -
> -#include <linux/kernel.h>
> -#include <linux/slab.h>
> -#include <linux/lzo.h>
> -
> -#include "zcomp_lzo.h"
> -
> -static void *lzo_create(void)
> -{
> -	return kzalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
> -}
> -
> -static void lzo_destroy(void *private)
> -{
> -	kfree(private);
> -}
> -
> -static int lzo_compress(const unsigned char *src, unsigned char *dst,
> -		size_t *dst_len, void *private)
> -{
> -	int ret = lzo1x_1_compress(src, PAGE_SIZE, dst, dst_len, private);
> -	return ret == LZO_E_OK ? 0 : ret;
> -}
> -
> -static int lzo_decompress(const unsigned char *src, size_t src_len,
> -		unsigned char *dst)
> -{
> -	size_t dst_len = PAGE_SIZE;
> -	int ret = lzo1x_decompress_safe(src, src_len, dst, &dst_len);
> -	return ret == LZO_E_OK ? 0 : ret;
> -}
> -
> -struct zcomp_backend zcomp_lzo = {
> -	.compress = lzo_compress,
> -	.decompress = lzo_decompress,
> -	.create = lzo_create,
> -	.destroy = lzo_destroy,
> -	.name = "lzo",
> -};
> diff --git a/drivers/block/zram/zcomp_lzo.h b/drivers/block/zram/zcomp_lzo.h
> deleted file mode 100644
> index 128c580..0000000
> --- a/drivers/block/zram/zcomp_lzo.h
> +++ /dev/null
> @@ -1,17 +0,0 @@
> -/*
> - * Copyright (C) 2014 Sergey Senozhatsky.
> - *
> - * This program is free software; you can redistribute it and/or
> - * modify it under the terms of the GNU General Public License
> - * as published by the Free Software Foundation; either version
> - * 2 of the License, or (at your option) any later version.
> - */
> -
> -#ifndef _ZCOMP_LZO_H_
> -#define _ZCOMP_LZO_H_
> -
> -#include "zcomp.h"
> -
> -extern struct zcomp_backend zcomp_lzo;
> -
> -#endif /* _ZCOMP_LZO_H_ */
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 55e09db1..834f452 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -567,7 +567,7 @@ static int zram_decompress_page(struct zram *zram, struct zcomp_strm *zstrm,
>  	unsigned char *cmem;
>  	struct zram_meta *meta = zram->meta;
>  	unsigned long handle;
> -	size_t size;
> +	unsigned int size;
>  
>  	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
>  	handle = meta->table[index].handle;
> @@ -656,7 +656,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  			   int offset)
>  {
>  	int ret = 0;
> -	size_t clen;
> +	unsigned int clen;
>  	unsigned long handle;
>  	struct page *page;
>  	unsigned char *user_mem, *cmem, *src, *uncmem = NULL;
> @@ -731,7 +731,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  
>  	handle = zs_malloc(meta->mem_pool, clen);
>  	if (!handle) {
> -		pr_err("Error allocating memory for compressed page: %u, size=%zu\n",
> +		pr_err("Error allocating memory for compressed page: %u, size=%u\n",
>  			index, clen);
>  		ret = -ENOMEM;
>  		goto out;
> -- 
> 1.9.1
>