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Commit 9cc97529 authored by Sergey Senozhatsky's avatar Sergey Senozhatsky Committed by Linus Torvalds
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zram: factor out single stream compression 

This is preparation patch to add multi stream support to zcomp.

Introduce struct zcomp_strm_single and a set of functions to manage
zcomp_strm stream access.  zcomp_strm_single implements single compession
stream, same way as current zcomp implementation.  This moves zcomp_strm
stream control and locking from zcomp, so compressing backend zcomp is not
aware of required locking.

Single and multi streams require different locking schemes.  Minchan Kim
reported that spinlock-based locking scheme (which is used in multi stream
implementation) has demonstrated a severe perfomance regression for single
compression stream case, comparing to mutex-based.  see
https://lkml.org/lkml/2014/2/18/16



The following set of functions added:
- zcomp_strm_single_find()/zcomp_strm_single_release()
  find and release a compression stream, implement required locking
- zcomp_strm_single_create()/zcomp_strm_single_destroy()
  create and destroy zcomp_strm_single

New ->strm_find() and ->strm_release() callbacks added to zcomp, which are
set to zcomp_strm_single_find() and zcomp_strm_single_release() during
initialisation.  Instead of direct locking and zcomp_strm access from
zcomp_strm_find() and zcomp_strm_release(), zcomp now calls ->strm_find()
and ->strm_release() correspondingly.

Signed-off-by: default avatarSergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b7ca232e

drivers/block/zram/zcomp.c

+54 −8
Original line number Diff line number Diff line
@@ -16,6 +16,14 @@ 
#include "zcomp.h"

#include "zcomp_lzo.h"



/*

 * single zcomp_strm backend

 */

struct zcomp_strm_single {

	struct mutex strm_lock;

	struct zcomp_strm *zstrm;

};



static struct zcomp_backend *find_backend(const char *compress)

{

	if (strncmp(compress, "lzo", 3) == 0)
@@ -54,15 +62,56 @@ static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp) 
	return zstrm;

}



static struct zcomp_strm *zcomp_strm_single_find(struct zcomp *comp)

{

	struct zcomp_strm_single *zs = comp->stream;

	mutex_lock(&zs->strm_lock);

	return zs->zstrm;

}



static void zcomp_strm_single_release(struct zcomp *comp,

		struct zcomp_strm *zstrm)

{

	struct zcomp_strm_single *zs = comp->stream;

	mutex_unlock(&zs->strm_lock);

}



static void zcomp_strm_single_destroy(struct zcomp *comp)

{

	struct zcomp_strm_single *zs = comp->stream;

	zcomp_strm_free(comp, zs->zstrm);

	kfree(zs);

}



static int zcomp_strm_single_create(struct zcomp *comp)

{

	struct zcomp_strm_single *zs;



	comp->destroy = zcomp_strm_single_destroy;

	comp->strm_find = zcomp_strm_single_find;

	comp->strm_release = zcomp_strm_single_release;

	zs = kmalloc(sizeof(struct zcomp_strm_single), GFP_KERNEL);

	if (!zs)

		return -ENOMEM;



	comp->stream = zs;

	mutex_init(&zs->strm_lock);

	zs->zstrm = zcomp_strm_alloc(comp);

	if (!zs->zstrm) {

		kfree(zs);

		return -ENOMEM;

	}

	return 0;

}



struct zcomp_strm *zcomp_strm_find(struct zcomp *comp)

{

	mutex_lock(&comp->strm_lock);

	return comp->zstrm;

	return comp->strm_find(comp);

}



void zcomp_strm_release(struct zcomp *comp, struct zcomp_strm *zstrm)

{

	mutex_unlock(&comp->strm_lock);

	comp->strm_release(comp, zstrm);

}



int zcomp_compress(struct zcomp *comp, struct zcomp_strm *zstrm,
@@ -80,7 +129,7 @@ int zcomp_decompress(struct zcomp *comp, const unsigned char *src, 


void zcomp_destroy(struct zcomp *comp)

{

	zcomp_strm_free(comp, comp->zstrm);

	comp->destroy(comp);

	kfree(comp);

}
@@ -104,10 +153,7 @@ struct zcomp *zcomp_create(const char *compress) 
		return NULL;



	comp->backend = backend;

	mutex_init(&comp->strm_lock);



	comp->zstrm = zcomp_strm_alloc(comp);

	if (!comp->zstrm) {

	if (zcomp_strm_single_create(comp) != 0) {

		kfree(comp);

		return NULL;

	}

drivers/block/zram/zcomp.h

+5 −2
Original line number Diff line number Diff line
@@ -39,9 +39,12 @@ struct zcomp_backend { 


/* dynamic per-device compression frontend */

struct zcomp {

	struct mutex strm_lock;

	struct zcomp_strm *zstrm;

	void *stream;

	struct zcomp_backend *backend;



	struct zcomp_strm *(*strm_find)(struct zcomp *comp);

	void (*strm_release)(struct zcomp *comp, struct zcomp_strm *zstrm);

	void (*destroy)(struct zcomp *comp);

};



struct zcomp *zcomp_create(const char *comp);