zram: make compression algorithm selection possible

Add and document `comp_algorithm' device attribute. This attribute allows to show supported compression and currently selected compression algorithms: cat /sys/block/zram0/comp_algorithm [lzo] lz4 and change selected compression algorithm: echo lzo > /sys/block/zram0/comp_algorithm Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

zram: make compression algorithm selection possible
Add and document `comp_algorithm' device attribute. This attribute allows to show supported compression and currently selected compression algorithms: cat /sys/block/zram0/comp_algorithm [lzo] lz4 and change selected compression algorithm: echo lzo > /sys/block/zram0/comp_algorithm Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Sergey Senozhatsky · Linus Torvalds
1 parent fe8eb122c8
Showing 6 changed files with 93 additions and 11 deletions Side-by-side Diff
Documentation/ABI/testing/sysfs-block-zram
Documentation/blockdev/zram.txt
drivers/block/zram/zcomp.c
drivers/block/zram/zcomp.h
drivers/block/zram/zram_drv.c
drivers/block/zram/zram_drv.h
@@ -65,6 +65,14 @@
 		number of backend's zcomp_strm compression streams (number of
 		concurrent compress operations).
  
+What:		/sys/block/zram<id>/comp_algorithm
+Date:		February 2014
+Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+		The comp_algorithm file is read-write and lets to show
+		available and selected compression algorithms, change
+		compression algorithm selection.
+
 What:		/sys/block/zram<id>/notify_free
 Date:		August 2010
 Contact:	Nitin Gupta <ngupta@vflare.org>
@@ -42,7 +42,21 @@
 as a special case and does not support dynamic max_comp_streams. Only multi
 stream backend supports dynamic max_comp_streams adjustment.
  
-3) Set Disksize
+3) Select compression algorithm
+	Using comp_algorithm device attribute one can see available and
+	currently selected (shown in square brackets) compression algortithms,
+	change selected compression algorithm (once the device is initialised
+	there is no way to change compression algorithm).
+
+	Examples:
+	#show supported compression algorithms
+	cat /sys/block/zram0/comp_algorithm
+	lzo [lz4]
+
+	#select lzo compression algorithm
+	echo lzo > /sys/block/zram0/comp_algorithm
+
+4) Set Disksize
         Set disk size by writing the value to sysfs node 'disksize'.
         The value can be either in bytes or you can use mem suffixes.
         Examples:
  
@@ -59,14 +73,14 @@
 since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
 size of the disk when not in use so a huge zram is wasteful.
  
-4) Activate:
+5) Activate:
 	mkswap /dev/zram0
 	swapon /dev/zram0
  
 	mkfs.ext4 /dev/zram1
 	mount /dev/zram1 /tmp
  
-5) Stats:
+6) Stats:
 	Per-device statistics are exported as various nodes under
 	/sys/block/zram<id>/
 		disksize
  
@@ -81,11 +95,11 @@
 		compr_data_size
 		mem_used_total
  
-6) Deactivate:
+7) Deactivate:
 	swapoff /dev/zram0
 	umount /dev/zram1
  
-7) Reset:
+8) Reset:
 	Write any positive value to 'reset' sysfs node
 	echo 1 > /sys/block/zram0/reset
 	echo 1 > /sys/block/zram1/reset
@@ -39,11 +39,20 @@
 	wait_queue_head_t strm_wait;
 };
  
+static struct zcomp_backend *backends[] = {
+	&zcomp_lzo,
+	NULL
+};
+
 static struct zcomp_backend *find_backend(const char *compress)
 {
-	if (strncmp(compress, "lzo", 3) == 0)
-		return &zcomp_lzo;
-	return NULL;
+	int i = 0;
+	while (backends[i]) {
+		if (sysfs_streq(compress, backends[i]->name))
+			break;
+		i++;
+	}
+	return backends[i];
 }
  
 static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
@@ -249,6 +258,23 @@
 		return -ENOMEM;
 	}
 	return 0;
+}
+
+/* show available compressors */
+ssize_t zcomp_available_show(const char *comp, char *buf)
+{
+	ssize_t sz = 0;
+	int i = 0;
+
+	while (backends[i]) {
+		if (sysfs_streq(comp, backends[i]->name))
+			sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
+		else
+			sz += sprintf(buf + sz, "%s ", backends[i]->name);
+		i++;
+	}
+	sz += sprintf(buf + sz, "\n");
+	return sz;
 }
  
 int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
@@ -50,6 +50,8 @@
 	void (*destroy)(struct zcomp *comp);
 };
  
+ssize_t zcomp_available_show(const char *comp, char *buf);
+
 struct zcomp *zcomp_create(const char *comp, int max_strm);
 void zcomp_destroy(struct zcomp *comp);
  
@@ -141,6 +141,34 @@
 	return len;
 }
  
+static ssize_t comp_algorithm_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	size_t sz;
+	struct zram *zram = dev_to_zram(dev);
+
+	down_read(&zram->init_lock);
+	sz = zcomp_available_show(zram->compressor, buf);
+	up_read(&zram->init_lock);
+
+	return sz;
+}
+
+static ssize_t comp_algorithm_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct zram *zram = dev_to_zram(dev);
+	down_write(&zram->init_lock);
+	if (init_done(zram)) {
+		up_write(&zram->init_lock);
+		pr_info("Can't change algorithm for initialized device\n");
+		return -EBUSY;
+	}
+	strlcpy(zram->compressor, buf, sizeof(zram->compressor));
+	up_write(&zram->init_lock);
+	return len;
+}
+
 /* flag operations needs meta->tb_lock */
 static int zram_test_flag(struct zram_meta *meta, u32 index,
 			enum zram_pageflags flag)
  
@@ -572,10 +600,10 @@
 		goto out_free_meta;
 	}
  
-	zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
+	zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
 	if (!zram->comp) {
 		pr_info("Cannot initialise %s compressing backend\n",
-				default_compressor);
+				zram->compressor);
 		err = -EINVAL;
 		goto out_free_meta;
 	}
@@ -735,6 +763,8 @@
 static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
 static DEVICE_ATTR(max_comp_streams, S_IRUGO | S_IWUSR,
 		max_comp_streams_show, max_comp_streams_store);
+static DEVICE_ATTR(comp_algorithm, S_IRUGO | S_IWUSR,
+		comp_algorithm_show, comp_algorithm_store);
  
 ZRAM_ATTR_RO(num_reads);
 ZRAM_ATTR_RO(num_writes);
@@ -760,6 +790,7 @@
 	&dev_attr_compr_data_size.attr,
 	&dev_attr_mem_used_total.attr,
 	&dev_attr_max_comp_streams.attr,
+	&dev_attr_comp_algorithm.attr,
 	NULL,
 };
  
@@ -820,7 +851,7 @@
 		pr_warn("Error creating sysfs group");
 		goto out_free_disk;
 	}
-
+	strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
 	zram->meta = NULL;
 	zram->max_comp_streams = 1;
 	return 0;
@@ -101,6 +101,7 @@
 	u64 disksize;	/* bytes */
 	int max_comp_streams;
 	struct zram_stats stats;
+	char compressor[10];
 };
 #endif
...	...	@@ -65,6 +65,14 @@
65	65	number of backend's zcomp_strm compression streams (number of
66	66	concurrent compress operations).
67	67
	68	+What: /sys/block/zram<id>/comp_algorithm
	69	+Date: February 2014
	70	+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
	71	+Description:
	72	+ The comp_algorithm file is read-write and lets to show
	73	+ available and selected compression algorithms, change
	74	+ compression algorithm selection.
	75	+
68	76	What: /sys/block/zram<id>/notify_free
69	77	Date: August 2010
70	78	Contact: Nitin Gupta <ngupta@vflare.org>
...	...	@@ -42,7 +42,21 @@
42	42	as a special case and does not support dynamic max_comp_streams. Only multi
43	43	stream backend supports dynamic max_comp_streams adjustment.
44	44
45		-3) Set Disksize
	45	+3) Select compression algorithm
	46	+ Using comp_algorithm device attribute one can see available and
	47	+ currently selected (shown in square brackets) compression algortithms,
	48	+ change selected compression algorithm (once the device is initialised
	49	+ there is no way to change compression algorithm).
	50	+
	51	+ Examples:
	52	+ #show supported compression algorithms
	53	+ cat /sys/block/zram0/comp_algorithm
	54	+ lzo [lz4]
	55	+
	56	+ #select lzo compression algorithm
	57	+ echo lzo > /sys/block/zram0/comp_algorithm
	58	+
	59	+4) Set Disksize
46	60	Set disk size by writing the value to sysfs node 'disksize'.
47	61	The value can be either in bytes or you can use mem suffixes.
48	62	Examples:
49	63
...	...	@@ -59,14 +73,14 @@
59	73	since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
60	74	size of the disk when not in use so a huge zram is wasteful.
61	75
62		-4) Activate:
	76	+5) Activate:
63	77	mkswap /dev/zram0
64	78	swapon /dev/zram0
65	79
66	80	mkfs.ext4 /dev/zram1
67	81	mount /dev/zram1 /tmp
68	82
69		-5) Stats:
	83	+6) Stats:
70	84	Per-device statistics are exported as various nodes under
71	85	/sys/block/zram<id>/
72	86	disksize
73	87
...	...	@@ -81,11 +95,11 @@
81	95	compr_data_size
82	96	mem_used_total
83	97
84		-6) Deactivate:
	98	+7) Deactivate:
85	99	swapoff /dev/zram0
86	100	umount /dev/zram1
87	101
88		-7) Reset:
	102	+8) Reset:
89	103	Write any positive value to 'reset' sysfs node
90	104	echo 1 > /sys/block/zram0/reset
91	105	echo 1 > /sys/block/zram1/reset
...	...	@@ -39,11 +39,20 @@
39	39	wait_queue_head_t strm_wait;
40	40	};
41	41
	42	+static struct zcomp_backend *backends[] = {
	43	+ &zcomp_lzo,
	44	+ NULL
	45	+};
	46	+
42	47	static struct zcomp_backend find_backend(const char compress)
43	48	{
44		- if (strncmp(compress, "lzo", 3) == 0)
45		- return &zcomp_lzo;
46		- return NULL;
	49	+ int i = 0;
	50	+ while (backends[i]) {
	51	+ if (sysfs_streq(compress, backends[i]->name))
	52	+ break;
	53	+ i++;
	54	+ }
	55	+ return backends[i];
47	56	}
48	57
49	58	static void zcomp_strm_free(struct zcomp comp, struct zcomp_strm zstrm)
...	...	@@ -249,6 +258,23 @@
249	258	return -ENOMEM;
250	259	}
251	260	return 0;
	261	+}
	262	+
	263	+/* show available compressors */
	264	+ssize_t zcomp_available_show(const char comp, char buf)
	265	+{
	266	+ ssize_t sz = 0;
	267	+ int i = 0;
	268	+
	269	+ while (backends[i]) {
	270	+ if (sysfs_streq(comp, backends[i]->name))
	271	+ sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
	272	+ else
	273	+ sz += sprintf(buf + sz, "%s ", backends[i]->name);
	274	+ i++;
	275	+ }
	276	+ sz += sprintf(buf + sz, "\n");
	277	+ return sz;
252	278	}
253	279
254	280	int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
...	...	@@ -50,6 +50,8 @@
50	50	void (destroy)(struct zcomp comp);
51	51	};
52	52
	53	+ssize_t zcomp_available_show(const char comp, char buf);
	54	+
53	55	struct zcomp zcomp_create(const char comp, int max_strm);
54	56	void zcomp_destroy(struct zcomp *comp);
55	57
...	...	@@ -141,6 +141,34 @@
141	141	return len;
142	142	}
143	143
	144	+static ssize_t comp_algorithm_show(struct device *dev,
	145	+ struct device_attribute attr, char buf)
	146	+{
	147	+ size_t sz;
	148	+ struct zram *zram = dev_to_zram(dev);
	149	+
	150	+ down_read(&zram->init_lock);
	151	+ sz = zcomp_available_show(zram->compressor, buf);
	152	+ up_read(&zram->init_lock);
	153	+
	154	+ return sz;
	155	+}
	156	+
	157	+static ssize_t comp_algorithm_store(struct device *dev,
	158	+ struct device_attribute attr, const char buf, size_t len)
	159	+{
	160	+ struct zram *zram = dev_to_zram(dev);
	161	+ down_write(&zram->init_lock);
	162	+ if (init_done(zram)) {
	163	+ up_write(&zram->init_lock);
	164	+ pr_info("Can't change algorithm for initialized device\n");
	165	+ return -EBUSY;
	166	+ }
	167	+ strlcpy(zram->compressor, buf, sizeof(zram->compressor));
	168	+ up_write(&zram->init_lock);
	169	+ return len;
	170	+}
	171	+
144	172	/* flag operations needs meta->tb_lock */
145	173	static int zram_test_flag(struct zram_meta *meta, u32 index,
146	174	enum zram_pageflags flag)
147	175
...	...	@@ -572,10 +600,10 @@
572	600	goto out_free_meta;
573	601	}
574	602
575		- zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
	603	+ zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
576	604	if (!zram->comp) {
577	605	pr_info("Cannot initialise %s compressing backend\n",
578		- default_compressor);
	606	+ zram->compressor);
579	607	err = -EINVAL;
580	608	goto out_free_meta;
581	609	}
...	...	@@ -735,6 +763,8 @@
735	763	static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
736	764	static DEVICE_ATTR(max_comp_streams, S_IRUGO \| S_IWUSR,
737	765	max_comp_streams_show, max_comp_streams_store);
	766	+static DEVICE_ATTR(comp_algorithm, S_IRUGO \| S_IWUSR,
	767	+ comp_algorithm_show, comp_algorithm_store);
738	768
739	769	ZRAM_ATTR_RO(num_reads);
740	770	ZRAM_ATTR_RO(num_writes);
...	...	@@ -760,6 +790,7 @@
760	790	&dev_attr_compr_data_size.attr,
761	791	&dev_attr_mem_used_total.attr,
762	792	&dev_attr_max_comp_streams.attr,
	793	+ &dev_attr_comp_algorithm.attr,
763	794	NULL,
764	795	};
765	796
...	...	@@ -820,7 +851,7 @@
820	851	pr_warn("Error creating sysfs group");
821	852	goto out_free_disk;
822	853	}
823		-
	854	+ strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
824	855	zram->meta = NULL;
825	856	zram->max_comp_streams = 1;
826	857	return 0;
...	...	@@ -101,6 +101,7 @@
101	101	u64 disksize; /* bytes */
102	102	int max_comp_streams;
103	103	struct zram_stats stats;
	104	+ char compressor[10];
104	105	};
105	106	#endif