Cleancache backend implementation

gistfile1.c

#include <linux/cleancache.h>
#include <linux/init.h>
#include <linux/module.h>

/* Allocation flags */
#define ZCOMPRAM_GFP_MASK  (GFP_ATOMIC | __GFP_NORETRY | __GFP_NOWARN)

/* Initial page pool: 32 MB (2^13 * 4KB) in pages */
#define ZCOMPRAM_ORDER 13

/* The pool holding the compressed pages */
struct page* page_pool;

/*  Clean cache operations implementation */
static void zcompram_cleancache_put_page(int pool_id,
					struct cleancache_filekey key,
					pgoff_t index, struct page *page)
{
	printk(KERN_INFO "ZCOMPRAM: PUT PAGE %d %ld %p\n", pool_id, index, page);
}

static int zcompram_cleancache_get_page(int pool_id,
					struct cleancache_filekey key,
					pgoff_t index, struct page *page)
{
	printk(KERN_INFO "ZCOMPRAM: GET PAGE %d %ld %p\n", pool_id, index, page);
	return -1;
}

static void zcompram_cleancache_flush_page(int pool_id,
					struct cleancache_filekey key,
					pgoff_t index)
{
	printk(KERN_INFO "ZCOMPRAM: FLUSH PAGE\n");
}

static void zcompram_cleancache_flush_inode(int pool_id,
					struct cleancache_filekey key)
{
	printk(KERN_INFO "ZCOMPRAM: FLUSH INODE\n");
}

static void zcompram_cleancache_flush_fs(int pool_id)
{
	printk(KERN_INFO "ZCOMPRAM: FLUSH FS\n");
}

static int zcompram_cleancache_init_fs(size_t pagesize)
{
	printk(KERN_INFO "ZCOMPRAM: INIT FS\n");
	return -1;
}

static int zcompram_cleancache_init_shared_fs(char *uuid, size_t pagesize)
{
	printk(KERN_INFO "ZCOMPRAM: FLUSH INIT SHARED\n");
	return -1;
}

static struct cleancache_ops zcompram_cleancache_ops = {
	.put_page = zcompram_cleancache_put_page,
	.get_page = zcompram_cleancache_get_page,
	.invalidate_page = zcompram_cleancache_flush_page,
	.invalidate_inode = zcompram_cleancache_flush_inode,
	.invalidate_fs = zcompram_cleancache_flush_fs,
	.init_shared_fs = zcompram_cleancache_init_shared_fs,
	.init_fs = zcompram_cleancache_init_fs
};

struct cleancache_ops zcompram_cleancache_register_ops(void)
{
	struct cleancache_ops old_ops =
		cleancache_register_ops(&zcompram_cleancache_ops);

	return old_ops;
}

static int __init zcompram_init(void)
{
	printk(KERN_INFO ">> ZCOMPRAM INIT\n");
	page_pool = alloc_pages(ZCOMPRAM_GFP_MASK, ZCOMPRAM_ORDER);

	zcompram_cleancache_register_ops();

	if (cleancache_enabled) {
		printk(KERN_INFO ">> ZCOMPRAM: cleancache_enabled\n");
	}
	else {
		printk(KERN_INFO ">> ZCOMPRAM: cleancache_disabled\n");
	}
	
	return 0;
}

static void zcompram_exit(void)
{
	__free_pages(page_pool, ZCOMPRAM_ORDER);
}

module_init(zcompram_init);
module_exit(zcompram_exit);

MODULE_LICENSE("GPL");