From: Timofey Titovets <nefelim...@gmail.com>
This add supporting of autochange count of zram devices on demand, like
loop devices;
This working by following rules:
- Always save minimum devices count specified by num_device (can be
specified while kernel module loading)
- if last device already using add new device;
- if last and prelast devices is free - delete last zram device;
Signed-off-by: Timofey Titovets <nefelim...@gmail.com>
From v1 -> v2:
Delete useless variable 'ret', added documentation for explain new zram
behaviour
Please pull from:
https://github.com/Nefelim4ag/linux.git
---
Tested on 3.15.5-2-ARCH, can be applied on any kernel version
after this patch 'zram: add LZ4 compression support' -
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=6e76668e415adf799839f0ab205142ad7002d260
---
diff --git a/Documentation/blockdev/zram.txt
b/Documentation/blockdev/zram.txt
index 0595c3f..7f5c921 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -18,9 +18,19 @@ Following shows a typical sequence of steps for using
zram.
1) Load Module:
modprobe zram num_devices=4
- This creates 4 devices: /dev/zram{0,1,2,3}
+ This pre creates 4 devices: /dev/zram{0,1,2,3}
(num_devices parameter is optional. Default: 1)
+ Kernel dynamically changes number of zram devices by demand
+ (between num_devices and 31)
+ If set disk size(4) for last device
+ kernel automatically adds new zram device
+ If last two devices have zero disk size after reset(8),
+ kernel will destroy last device
+
+ Summing up all features, comes one simple rule:
+ "The last zram device is always free for use"
+
2) Set max number of compression streams
Compression backend may use up to max_comp_streams compression streams,
thus allowing up to max_comp_streams concurrent compression operations.
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 089e72c..9b2fc89 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -42,6 +42,10 @@ static const char *default_compressor = "lzo";
/* Module params (documentation at end) */
static unsigned int num_devices = 1;
+static unsigned int last_created_dev = 1;
+
+static void zram_add_dev(void);
+static void zram_del_dev(void);
#define ZRAM_ATTR_RO(name) \
static ssize_t zram_attr_##name##_show(struct device *d, \
@@ -168,6 +172,7 @@ 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);
@@ -239,6 +244,7 @@ static struct zram_meta *zram_meta_alloc(u64 disksize)
{
size_t num_pages;
struct zram_meta *meta = kmalloc(sizeof(*meta), GFP_KERNEL);
+
if (!meta)
goto out;
@@ -374,6 +380,7 @@ static int zram_bvec_read(struct zram *zram, struct
bio_vec *bvec,
struct page *page;
unsigned char *user_mem, *uncmem = NULL;
struct zram_meta *meta = zram->meta;
+
page = bvec->bv_page;
read_lock(&meta->tb_lock);
@@ -607,6 +614,7 @@ static void zram_reset_device(struct zram *zram,
bool reset_capacity)
/* Free all pages that are still in this zram device */
for (index = 0; index < zram->disksize >> PAGE_SHIFT; index++) {
unsigned long handle = meta->table[index].handle;
+
if (!handle)
continue;
@@ -668,6 +676,7 @@ static ssize_t disksize_store(struct device *dev,
set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
revalidate_disk(zram->disk);
up_write(&zram->init_lock);
+ zram_add_dev();
return len;
out_destroy_comp:
@@ -712,6 +721,7 @@ static ssize_t reset_store(struct device *dev,
bdput(bdev);
zram_reset_device(zram, true);
+ zram_del_dev();
return len;
out:
@@ -954,6 +964,41 @@ static void destroy_device(struct zram *zram)
blk_cleanup_queue(zram->queue);
}
+/* remove last free device, if last and prelast dev a free */
+static void zram_del_dev(void)
+{
+ if (last_created_dev < num_devices)
+ return;
+
+ if (zram_devices[last_created_dev].disksize == 0 &&
+ zram_devices[last_created_dev-1].disksize == 0
+ ) {
+ destroy_device(&zram_devices[last_created_dev]);
+ last_created_dev--;
+ pr_info("Deleted zram%u device\n", last_created_dev);
+ }
+}
+
+/* Auto add empty zram device, if last device in use */
+static void zram_add_dev(void)
+{
+ if (last_created_dev+1 > max_num_devices) {
+ pr_warn("Can't add zram%u, max device number reached\n",
+ num_devices);
+ return;
+ }
+
+ if (&zram_devices[last_created_dev].disksize > 0) {
+ last_created_dev++;
+ if (create_device(&zram_devices[last_created_dev],
last_created_dev)) {
+ destroy_device(&zram_devices[last_created_dev]);
+ last_created_dev--;
+ return;
+ }
+ pr_info("Created zram%u device\n", last_created_dev);
+ }
+}
+
static int __init zram_init(void)
{
int ret, dev_id;
@@ -972,18 +1017,20 @@ static int __init zram_init(void)
goto out;
}
- /* Allocate the device array and initialize each one */
- zram_devices = kzalloc(num_devices * sizeof(struct zram), GFP_KERNEL);
+ /* Allocate the device array */
+ zram_devices = kcalloc(max_num_devices, sizeof(struct zram),
GFP_KERNEL);
if (!zram_devices) {
ret = -ENOMEM;
goto unregister;
}
+ /* Initialise zram{0..num_devices} */
for (dev_id = 0; dev_id < num_devices; dev_id++) {
ret = create_device(&zram_devices[dev_id], dev_id);
if (ret)
goto free_devices;
}
+ last_created_dev = num_devices-1;
pr_info("Created %u device(s) ...\n", num_devices);
@@ -1004,7 +1051,7 @@ static void __exit zram_exit(void)
int i;
struct zram *zram;
- for (i = 0; i < num_devices; i++) {
+ for (i = 0; i < last_created_dev+1; i++) {
zram = &zram_devices[i];
destroy_device(zram);
@@ -1025,7 +1072,7 @@ module_init(zram_init);
module_exit(zram_exit);
module_param(num_devices, uint, 0);
-MODULE_PARM_DESC(num_devices, "Number of zram devices");
+MODULE_PARM_DESC(num_devices, "Number of pre created zram devices");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Nitin Gupta <ngu...@vflare.org>");
--
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