staging: zcache: support multiple clients, prep for KVM and RAMster

This is version 3 of an update to zcache, incorporating feedback from the list.
This patch adds support to the in-kernel transcendent memory ("tmem") code
and the zcache driver for multiple clients, which will be needed for both
RAMster and KVM support.  It also adds additional tmem callbacks to support
RAMster and corresponding no-op stubs in the zcache driver.  In v2, I've
also taken the liberty of adding some additional sysfs variables to
both surface information and allow policy control.  Those experimenting
with zcache should find them useful.  V3 clarifies some code walking
and declaring arrays.

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>

[v3: error27@gmail.com: fix array bounds/walking]
[v2: konrad.wilk@oracle.com: fix bools, add check for NULL, fix a comment]
[v2: sjenning@linux.vnet.ibm.com: add info/tunables for poor compression]
[v2: marcusklemm@googlemail.com: add tunable for max persistent pages]
Acked-by: Dan Carpenter <error27@gmail.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: linux-mm@kvack.org
Cc: kvm@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 17 insertions, 6 deletions

diff --git a/drivers/staging/zcache/tmem.h b/drivers/staging/zcache/tmem.h
index 2e07e217d51f..ed147c4b110d 100644
--- a/drivers/staging/zcache/tmem.h
+++ b/drivers/staging/zcache/tmem.h
@@ -147,6 +147,7 @@ struct tmem_obj {
 	unsigned int objnode_tree_height;
 	unsigned long objnode_count;
 	long pampd_count;
+	void *extra; /* for private use by pampd implementation */
 	DECL_SENTINEL
 };
 
@@ -166,10 +167,18 @@ struct tmem_objnode {
 
 /* pampd abstract datatype methods provided by the PAM implementation */
 struct tmem_pamops {
-	void *(*create)(struct tmem_pool *, struct tmem_oid *, uint32_t,
-			struct page *);
-	int (*get_data)(struct page *, void *, struct tmem_pool *);
-	void (*free)(void *, struct tmem_pool *);
+	void *(*create)(char *, size_t, bool, int,
+			struct tmem_pool *, struct tmem_oid *, uint32_t);
+	int (*get_data)(char *, size_t *, bool, void *, struct tmem_pool *,
+				struct tmem_oid *, uint32_t);
+	int (*get_data_and_free)(char *, size_t *, bool, void *,
+				struct tmem_pool *, struct tmem_oid *,
+				uint32_t);
+	void (*free)(void *, struct tmem_pool *, struct tmem_oid *, uint32_t);
+	void (*free_obj)(struct tmem_pool *, struct tmem_obj *);
+	bool (*is_remote)(void *);
+	void (*new_obj)(struct tmem_obj *);
+	int (*replace_in_obj)(void *, struct tmem_obj *);
 };
 extern void tmem_register_pamops(struct tmem_pamops *m);
 
@@ -184,9 +193,11 @@ extern void tmem_register_hostops(struct tmem_hostops *m);
 
 /* core tmem accessor functions */
 extern int tmem_put(struct tmem_pool *, struct tmem_oid *, uint32_t index,
-			struct page *page);
+			char *, size_t, bool, bool);
 extern int tmem_get(struct tmem_pool *, struct tmem_oid *, uint32_t index,
-			struct page *page);
+			char *, size_t *, bool, int);
+extern int tmem_replace(struct tmem_pool *, struct tmem_oid *, uint32_t index,
+			void *);
 extern int tmem_flush_page(struct tmem_pool *, struct tmem_oid *,
 			uint32_t index);
 extern int tmem_flush_object(struct tmem_pool *, struct tmem_oid *);