staging: zcache: enable zcache to be built/loaded as a module

Allow zcache to be built/loaded as a module.  Note runtime dependency
disallows loading if cleancache/frontswap lazy initialization patches
are not present.  Zsmalloc support has not yet been merged into zcache
but, once merged, could now easily be selected via a module_param.

If built-in (not built as a module), the original mechanism of enabling
via a kernel boot parameter is retained, but this should be considered
deprecated.

Note that module unload is explicitly not yet supported.
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
[v1: Rebased with different order of patches]
[v2: Removed [CLEANCACHE|FRONTSWAP]_HAS_LAZY_INIT ifdef]
[v3: Rebased on top of ramster->zcache move]
[v4: Redid the Makefile]
[v5: s/ZCACHE2/ZCACHE/]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
Cc: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andor Daam <andor.daam@googlemail.com>
Cc: Florian Schmaus <fschmaus@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Stefan Hengelein <ilendir@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/staging/zcache/Kconfig

 config ZCACHE
-	bool "Dynamic compression of swap pages and clean pagecache pages"
+	tristate "Dynamic compression of swap pages and clean pagecache pages"
 	depends on CRYPTO=y && SWAP=y && CLEANCACHE && FRONTSWAP
 	select CRYPTO_LZO
 	default n
@@ -19,8 +19,8 @@ config ZCACHE_DEBUG
 	  how zcache is doing. You probably want to set this to 'N'.
 
 config RAMSTER
-	bool "Cross-machine RAM capacity sharing, aka peer-to-peer tmem"
-	depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE=y
+	tristate "Cross-machine RAM capacity sharing, aka peer-to-peer tmem"
+	depends on CONFIGFS_FS=y && SYSFS=y && !HIGHMEM && ZCACHE
 	depends on NET
 	# must ensure struct page is 8-byte aligned
 	select HAVE_ALIGNED_STRUCT_PAGE if !64BIT

drivers/staging/zcache/tmem.c

@@ -35,7 +35,8 @@
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/atomic.h>
-#ifdef CONFIG_RAMSTER
+#include <linux/export.h>
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 #include <linux/delay.h>
 #endif
 
@@ -641,6 +642,7 @@ void *tmem_localify_get_pampd(struct tmem_pool *pool, struct tmem_oid *oidp,
 	/* note, hashbucket remains locked */
 	return pampd;
 }
+EXPORT_SYMBOL_GPL(tmem_localify_get_pampd);
 
 void tmem_localify_finish(struct tmem_obj *obj, uint32_t index,
 			  void *pampd, void *saved_hb, bool delete)
@@ -658,6 +660,7 @@ void tmem_localify_finish(struct tmem_obj *obj, uint32_t index,
 	}
 	spin_unlock(&hb->lock);
 }
+EXPORT_SYMBOL_GPL(tmem_localify_finish);
 
 /*
  * For ramster only.  Helper function to support asynchronous tmem_get.
@@ -719,6 +722,7 @@ int tmem_replace(struct tmem_pool *pool, struct tmem_oid *oidp,
 	spin_unlock(&hb->lock);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(tmem_replace);
 #endif
 
 /*

drivers/staging/zcache/tmem.h

@@ -126,7 +126,7 @@ static inline unsigned tmem_oid_hash(struct tmem_oid *oidp)
 				TMEM_HASH_BUCKET_BITS);
 }
 
-#ifdef CONFIG_RAMSTER
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 struct tmem_xhandle {
 	uint8_t client_id;
 	uint8_t xh_data_cksum;
@@ -171,7 +171,7 @@ struct tmem_obj {
 	unsigned int objnode_tree_height;
 	unsigned long objnode_count;
 	long pampd_count;
-#ifdef CONFIG_RAMSTER
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 	/*
 	 * for current design of ramster, all pages belonging to
 	 * an object reside on the same remotenode and extra is
@@ -215,7 +215,7 @@ struct tmem_pamops {
 				uint32_t);
 	void (*free)(void *, struct tmem_pool *,
 				struct tmem_oid *, uint32_t, bool);
-#ifdef CONFIG_RAMSTER
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 	void (*new_obj)(struct tmem_obj *);
 	void (*free_obj)(struct tmem_pool *, struct tmem_obj *, bool);
 	void *(*repatriate_preload)(void *, struct tmem_pool *,
@@ -247,7 +247,7 @@ extern int tmem_flush_page(struct tmem_pool *, struct tmem_oid *,
 extern int tmem_flush_object(struct tmem_pool *, struct tmem_oid *);
 extern int tmem_destroy_pool(struct tmem_pool *);
 extern void tmem_new_pool(struct tmem_pool *, uint32_t);
-#ifdef CONFIG_RAMSTER
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 extern int tmem_replace(struct tmem_pool *, struct tmem_oid *, uint32_t index,
 			void *);
 extern void *tmem_localify_get_pampd(struct tmem_pool *, struct tmem_oid *,

drivers/staging/zcache/zcache-main.c

@@ -37,8 +37,10 @@
 #include "debug.h"
 #ifdef CONFIG_RAMSTER
 static bool ramster_enabled __read_mostly;
+static int disable_frontswap_selfshrink;
 #else
 #define ramster_enabled false
+#define disable_frontswap_selfshrink 0
 #endif
 
 #ifndef __PG_WAS_ACTIVE
@@ -81,8 +83,12 @@ static char *namestr __read_mostly = "zcache";
 	(__GFP_FS | __GFP_NORETRY | __GFP_NOWARN | __GFP_NOMEMALLOC)
 
 /* crypto API for zcache  */
+#ifdef CONFIG_ZCACHE_MODULE
+static char *zcache_comp_name = "lzo";
+#else
 #define ZCACHE_COMP_NAME_SZ CRYPTO_MAX_ALG_NAME
 static char zcache_comp_name[ZCACHE_COMP_NAME_SZ] __read_mostly;
+#endif
 static struct crypto_comp * __percpu *zcache_comp_pcpu_tfms __read_mostly;
 
 enum comp_op {
@@ -1721,6 +1727,7 @@ struct frontswap_ops *zcache_frontswap_register_ops(void)
  * OR NOTHING HAPPENS!
  */
 
+#ifndef CONFIG_ZCACHE_MODULE
 static int __init enable_zcache(char *s)
 {
 	zcache_enabled = true;
@@ -1787,18 +1794,27 @@ static int __init enable_zcache_compressor(char *s)
 	return 1;
 }
 __setup("zcache=", enable_zcache_compressor);
+#endif
 
 
-static int __init zcache_comp_init(void)
+static int zcache_comp_init(void)
 {
 	int ret = 0;
 
 	/* check crypto algorithm */
+#ifdef CONFIG_ZCACHE_MODULE
+	ret = crypto_has_comp(zcache_comp_name, 0, 0);
+	if (!ret) {
+		ret = -1;
+		goto out;
+	}
+#else
 	if (*zcache_comp_name != '\0') {
 		ret = crypto_has_comp(zcache_comp_name, 0, 0);
 		if (!ret)
 			pr_info("zcache: %s not supported\n",
 					zcache_comp_name);
+		goto out;
 	}
 	if (!ret)
 		strcpy(zcache_comp_name, "lzo");
@@ -1807,6 +1823,7 @@ static int __init zcache_comp_init(void)
 		ret = 1;
 		goto out;
 	}
+#endif
 	pr_info("zcache: using %s compressor\n", zcache_comp_name);
 
 	/* alloc percpu transforms */
@@ -1818,10 +1835,13 @@ static int __init zcache_comp_init(void)
 	return ret;
 }
 
-static int __init zcache_init(void)
+static int zcache_init(void)
 {
 	int ret = 0;
 
+#ifdef CONFIG_ZCACHE_MODULE
+	zcache_enabled = 1;
+#endif
 	if (ramster_enabled) {
 		namestr = "ramster";
 		ramster_register_pamops(&zcache_pamops);
@@ -1894,9 +1914,28 @@ static int __init zcache_init(void)
 	}
 	if (ramster_enabled)
 		ramster_init(!disable_cleancache, !disable_frontswap,
-				frontswap_has_exclusive_gets, false);
+				frontswap_has_exclusive_gets,
+				!disable_frontswap_selfshrink);
 out:
 	return ret;
 }
 
+#ifdef CONFIG_ZCACHE_MODULE
+#ifdef CONFIG_RAMSTER
+module_param(ramster_enabled, int, S_IRUGO);
+module_param(disable_frontswap_selfshrink, int, S_IRUGO);
+#endif
+module_param(disable_cleancache, int, S_IRUGO);
+module_param(disable_frontswap, int, S_IRUGO);
+#ifdef FRONTSWAP_HAS_EXCLUSIVE_GETS
+module_param(frontswap_has_exclusive_gets, bool, S_IRUGO);
+#endif
+module_param(disable_frontswap_ignore_nonactive, int, S_IRUGO);
+module_param(zcache_comp_name, charp, S_IRUGO);
+module_init(zcache_init);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Dan Magenheimer <dan.magenheimer@oracle.com>");
+MODULE_DESCRIPTION("In-kernel compression of cleancache/frontswap pages");
+#else
 late_initcall(zcache_init);
+#endif

drivers/staging/zcache/zcache.h

@@ -39,7 +39,7 @@ extern int zcache_flush_page(int, int, struct tmem_oid *, uint32_t);
 extern int zcache_flush_object(int, int, struct tmem_oid *);
 extern void zcache_decompress_to_page(char *, unsigned int, struct page *);
 
-#ifdef CONFIG_RAMSTER
+#if defined(CONFIG_RAMSTER) || defined(CONFIG_RAMSTER_MODULE)
 extern void *zcache_pampd_create(char *, unsigned int, bool, int,
 				struct tmem_handle *);
 int zcache_autocreate_pool(unsigned int cli_id, unsigned int pool_id, bool eph);