From: Timofey Titovets <nefelim...@gmail.com>
This add supporting of auto allocate new zram devices on demand, like
loop devices
This working by following rules:
- Pre create zram devices specified by num_device
- if all device already in use -> add new free device
From v1 -> v2:
Delete useless variable 'ret', added documentation for explain new zram
behavior
From v2 -> v3
Delete logic to destroy not used devices, for avoid concurrency issues
Code refactoring for made patch small and clean as possible
Patch can pass the test:
#!/bin/sh
modprobe zram
while true; do
echo 10485760 > /sys/block/zram0/disksize&
echo 1 > /sys/block/zram0/reset&
done
Can be pulled 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..a090ac7 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -21,6 +21,9 @@ Following shows a typical sequence of steps for using
zram.
This creates 4 devices: /dev/zram{0,1,2,3}
(num_devices parameter is optional. Default: 1)
+ If all device in use kernel will create new zram device
+ (between num_devices and 31)
+
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..cc78779 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -43,6 +43,8 @@ static const char *default_compressor = "lzo";
/* Module params (documentation at end) */
static unsigned int num_devices = 1;
+static inline int zram_add_dev(void);
+
#define ZRAM_ATTR_RO(name) \
static ssize_t zram_attr_##name##_show(struct device *d, \
struct device_attribute *attr, char *b) \
@@ -168,6 +170,7 @@ 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 +242,7 @@ 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 +378,7 @@ 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 +612,7 @@ 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;
@@ -667,6 +673,7 @@ static ssize_t disksize_store(struct device *dev,
zram->disksize = disksize;
set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
revalidate_disk(zram->disk);
+ zram_add_dev();
up_write(&zram->init_lock);
return len;
@@ -954,6 +961,34 @@ static void destroy_device(struct zram *zram)
blk_cleanup_queue(zram->queue);
}
+/*
+ * Automatically add empty zram device,
+ * if all created devices already initialized
+ */
+static inline int zram_add_dev(void)
+{
+ int dev_id;
+
+ for (dev_id = 0; dev_id < num_devices; dev_id++) {
+ if (!zram_devices[dev_id].disksize)
+ return 0;
+ }
+
+ if (max_num_devices <= num_devices) {
+ pr_warn("Can't add zram%u, max device number reached\n",
num_devices);
+ return 1;
+ }
+
+ if (create_device(&zram_devices[num_devices], num_devices)) {
+ destroy_device(&zram_devices[num_devices]);
+ return 1;
+ }
+ pr_info("Created zram%u device\n", num_devices);
+ num_devices++;
+
+ return 0;
+}
+
static int __init zram_init(void)
{
int ret, dev_id;
@@ -972,13 +1007,14 @@ 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)
@@ -1025,7 +1061,7 @@ 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>");
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
