[PATCH] kNFSd: Initialial caching infrastructure for RPC authentication caches

This patch provides a "virtual class" for defining caches
that make user-space information available in the kernel
It is intended for RPC services or clients that need user-space
support for authentication.

As yet, support for userspace interaction isn't included as I want
that to be able to have separate review.

2 files changed, 244 insertions, 0 deletions

diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h
new file mode 100644
index 000000000000..efbf31293a6c
--- /dev/null
+++ b/include/linux/sunrpc/cache.h
@@ -0,0 +1,243 @@
+/*
+ * include/linux/sunrpc/cache.h
+ *
+ * Generic code for various authentication-related caches
+ * used by sunrpc clients and servers.
+ *
+ * Copyright (C) 2002 Neil Brown <neilb@cse.unsw.edu.au>
+ *
+ * Released under terms in GPL version 2.  See COPYING.
+ *
+ */
+
+#ifndef _LINUX_SUNRPC_CACHE_H_
+#define _LINUX_SUNRPC_CACHE_H_
+
+#include <linux/slab.h>
+#include <asm/atomic.h>
+
+/*
+ * Each cache requires:
+ *  - A 'struct cache_detail' which contains information specific to the cache
+ *    for common code to use.
+ *  - An item structure that must contain a "struct cache_head"
+ *  - A lookup function defined using DefineCacheLookup
+ *  - A 'put' function that can release a cache item. It will only
+ *    be called after cache_put has succeed, so there are guarantee
+ *    to be no references.
+ *  - A function to calculate a hash of an item's key.
+ *
+ * as well as assorted code fragments (e.g. compare keys) and numbers
+ * (e.g. hash size, goal_age, etc).
+ *
+ * Each cache must be registered so that it can be cleaned regularly.
+ * When the cache is unregistered, it is flushed completely.
+ *
+ * Entries have a ref count and a 'hashed' flag which counts the existance
+ * in the hash table.
+ * We only expire entries when refcount is zero.
+ * Existance in the cache is not measured in refcount but rather in
+ * CACHE_HASHED flag.
+ */
+
+/* Every cache item has a common header that is used
+ * for expiring and refreshing entries.
+ * 
+ */
+struct cache_head {
+	struct cache_head * next;
+	time_t		expiry_time;	/* After time time, don't use the data */
+	time_t		last_refresh;   /* If CACHE_PENDING, this is when upcall 
+					 * was sent, else this is when update was received
+					 */
+	atomic_t 	refcnt;
+	unsigned long	flags;
+};
+#define	CACHE_VALID	0	/* Entry contains valid data */
+#define	CACHE_NEGATIVE	1	/* Negative entry - there is no match for the key */
+#define	CACHE_PENDING	2	/* An upcall has been sent but no reply received yet*/
+#define	CACHE_HASHED	3	/* Entry is in a hash table */
+
+#define	CACHE_NEW_EXPIRY 120	/* keep new things pending confirmation for 120 seconds */
+
+struct cache_detail {
+	int			hash_size;
+	struct cache_head **	hash_table;
+	rwlock_t		hash_lock;
+
+	atomic_t		inuse; /* active user-space update or lookup */
+
+	char			*name;
+	void			(*cache_put)(struct cache_head *,
+					     struct cache_detail*);
+
+	/* request and update functions for interaction with userspace
+	 * will go here
+	 */
+
+	/* fields below this comment are for internal use
+	 * and should not be touched by cache owners
+	 */
+	time_t			flush_time;		/* flush all cache items with last_refresh
+							 * earlier than this */
+	struct list_head	others;
+	time_t			nextcheck;
+	int			entries;
+};
+
+
+/*
+ * just like a template in C++, this macro does cache lookup
+ * for us.
+ * The function is passed some sort of HANDLE from which a cache_detail
+ * structure can be determined (via SETUP, DETAIL), a template
+ * cache entry (type RTN*), and a "set" flag.  Using the HASHFN and the 
+ * TEST, the function will try to find a matching cache entry in the cache.
+ * If "set" == 0 :
+ *    If an entry is found, it is returned
+ *    If no entry is found, a new non-VALID entry is created.
+ * If "set" == 1 :
+ *    If no entry is found a new one is inserted with data from "template"
+ *    If a non-CACHE_VALID entry is found, it is updated from template using UPDATE
+ *    If a CACHE_VALID entry is found, a new entry is swapped in with data
+ *       from "template"
+ * If set == 2, we UPDATE, but don't swap. i.e. update in place
+ *
+ * If the passed handle has the CACHE_NEGATIVE flag set, then UPDATE is not
+ * run but insteead CACHE_NEGATIVE is set in any new item.
+
+ *  In any case, the new entry is returned with a reference count.
+ *
+ *    
+ * RTN is a struct type for a cache entry
+ * MEMBER is the member of the cache which is cache_head, which must be first
+ * FNAME is the name for the function	
+ * ARGS are arguments to function and must contain RTN *item, int set.  May
+ *   also contain something to be usedby SETUP or DETAIL to find cache_detail.
+ * SETUP  locates the cache detail and makes it available as...
+ * DETAIL identifies the cache detail, possibly set up by SETUP
+ * HASHFN returns a hash value of the cache entry "item"
+ * TEST  tests if "tmp" matches "item"
+ * INIT copies key information from "item" to "new"
+ * UPDATE copies content information from "item" to "tmp"
+ */
+#define DefineCacheLookup(RTN,MEMBER,FNAME,ARGS,SETUP,DETAIL,HASHFN,TEST,INIT,UPDATE)	\
+RTN *FNAME ARGS										\
+{											\
+	RTN *tmp, *new=NULL;								\
+	struct cache_head **hp, **head;							\
+	SETUP;										\
+ retry:											\
+	head = &(DETAIL)->hash_table[HASHFN];						\
+	if (set||new) write_lock(&(DETAIL)->hash_lock);					\
+	else read_lock(&(DETAIL)->hash_lock);						\
+	for(hp=head; *hp != NULL; hp = &tmp->MEMBER.next) {				\
+		tmp = container_of(*hp, RTN, MEMBER);					\
+		if (TEST) { /* found a match */						\
+											\
+			atomic_inc(&tmp->MEMBER.refcnt);				\
+			if (set) {							\
+				if (set!= 2 && test_bit(CACHE_VALID, &tmp->MEMBER.flags))\
+				{ /* need to swap in new */				\
+					RTN *t2;					\
+					if (!new) break;				\
+											\
+					new->MEMBER.next = tmp->MEMBER.next;		\
+					*head = &new->MEMBER;				\
+					tmp->MEMBER.next = NULL;			\
+					set_bit(CACHE_HASHED, &new->MEMBER.flags);	\
+					clear_bit(CACHE_HASHED, &tmp->MEMBER.flags);	\
+					t2 = tmp; tmp = new; new = t2;			\
+				}							\
+				if (test_bit(CACHE_NEGATIVE,  &item->MEMBER.flags))	\
+					 set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);	\
+				else {UPDATE;}						\
+			}								\
+			if (set||new) write_unlock(&(DETAIL)->hash_lock);		\
+			else read_unlock(&(DETAIL)->hash_lock);				\
+			if (set)							\
+				cache_fresh(DETAIL, &tmp->MEMBER, item->MEMBER.expiry_time); \
+			if (new) (DETAIL)->cache_put(&new->MEMBER, DETAIL);		\
+			return tmp;							\
+		}									\
+	}										\
+	/* Didn't find anything */							\
+	if (new) {									\
+		new->MEMBER.next = *head;						\
+		*head = &new->MEMBER;							\
+		(DETAIL)->entries ++;							\
+		set_bit(CACHE_HASHED, &new->MEMBER.flags);				\
+		if (set) {								\
+			tmp = new;							\
+			if (test_bit(CACHE_NEGATIVE, &item->MEMBER.flags))		\
+				set_bit(CACHE_NEGATIVE, &tmp->MEMBER.flags);		\
+			else {UPDATE;}							\
+		}									\
+	}										\
+	if (set||new) write_unlock(&(DETAIL)->hash_lock);				\
+	else read_unlock(&(DETAIL)->hash_lock);						\
+	if (new && set)									\
+		cache_fresh(DETAIL, &new->MEMBER, item->MEMBER.expiry_time);		\
+	if (new)				       					\
+		return new;								\
+	new = kmalloc(sizeof(*new), GFP_KERNEL);					\
+	if (new) {									\
+		cache_init(&new->MEMBER);						\
+		atomic_inc(&new->MEMBER.refcnt);					\
+		INIT;									\
+		tmp = new;								\
+		goto retry;								\
+	}										\
+	return NULL;									\
+}
+
+#define DefineSimpleCacheLookup(STRUCT)	\
+	DefineCacheLookup(struct STRUCT, h, STRUCT##_lookup, (struct STRUCT *item, int set), /*no setup */,	\
+			  & STRUCT##_cache, STRUCT##_hash(item), STRUCT##_match(item, tmp),\
+			  STRUCT##_init(new, item), STRUCT##_update(tmp, item))
+
+#define cache_for_each(pos, detail, index, member) 						\
+	for (({read_lock(&(detail)->hash_lock); index = (detail)->hash_size;}) ;		\
+	     ({if (index==0)read_unlock(&(detail)->hash_lock); index--;});			\
+		)										\
+		for (pos = container_of((detail)->hash_table[index], typeof(*pos), member);	\
+		     &pos->member;								\
+		     pos = container_of(pos->member.next, typeof(*pos), member))
+
+	     
+
+static inline struct cache_head  *cache_get(struct cache_head *h)
+{
+	atomic_inc(&h->refcnt);
+	return h;
+}
+
+
+static int inline cache_put(struct cache_head *h, struct cache_detail *cd)
+{
+	atomic_dec(&h->refcnt);
+	if (!atomic_read(&h->refcnt) &&
+	    h->expiry_time < cd->nextcheck)
+		cd->nextcheck = h->expiry_time;
+	if (!test_bit(CACHE_HASHED, &h->flags) &&
+	    !atomic_read(&h->refcnt))
+		return 1;
+
+	return 0;
+}
+
+extern void cache_init(struct cache_head *h);
+extern void cache_fresh(struct cache_detail *detail,
+			struct cache_head *head, time_t expiry);
+extern int cache_check(struct cache_detail *detail,
+		       struct cache_head *h);
+extern int cache_clean(void);
+extern void cache_flush(void);
+extern void cache_purge(struct cache_detail *detail);
+#define NEVER (0x7FFFFFFF)
+extern void cache_register(struct cache_detail *cd);
+extern int cache_unregister(struct cache_detail *cd);
+extern struct cache_detail *cache_find(char *name);
+extern void cache_drop(struct cache_detail *detail);
+
+#endif /*  _LINUX_SUNRPC_CACHE_H_ */
diff --git a/include/linux/sunrpc/debug.h b/include/linux/sunrpc/debug.h
index b338aa49201e..b41549525233 100644
--- a/include/linux/sunrpc/debug.h
+++ b/include/linux/sunrpc/debug.h
@@ -35,6 +35,7 @@
 #define RPCDBG_SVCSOCK		0x0100
 #define RPCDBG_SVCDSP		0x0200
 #define RPCDBG_MISC		0x0400
+#define RPCDBG_CACHE		0x0800
 #define RPCDBG_ALL		0x7fff
 
 #ifdef __KERNEL__