1/*
2 * Request reply cache. This is currently a global cache, but this may
3 * change in the future and be a per-client cache.
4 *
5 * This code is heavily inspired by the 44BSD implementation, although
6 * it does things a bit differently.
7 *
8 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
9 */
10
11#include <linux/slab.h>
12
13#include "nfsd.h"
14#include "cache.h"
15
16/* Size of reply cache. Common values are:
17 * 4.3BSD:	128
18 * 4.4BSD:	256
19 * Solaris2:	1024
20 * DEC Unix:	512-4096
21 */
22#define CACHESIZE		1024
23#define HASHSIZE		64
24
25static struct hlist_head *	cache_hash;
26static struct list_head 	lru_head;
27static int			cache_disabled = 1;
28
29/*
30 * Calculate the hash index from an XID.
31 */
32static inline u32 request_hash(u32 xid)
33{
34	u32 h = xid;
35	h ^= (xid >> 24);
36	return h & (HASHSIZE-1);
37}
38
39static int	nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
40
41/*
42 * locking for the reply cache:
43 * A cache entry is "single use" if c_state == RC_INPROG
44 * Otherwise, it when accessing _prev or _next, the lock must be held.
45 */
46static DEFINE_SPINLOCK(cache_lock);
47
48int nfsd_reply_cache_init(void)
49{
50	struct svc_cacherep	*rp;
51	int			i;
52
53	INIT_LIST_HEAD(&lru_head);
54	i = CACHESIZE;
55	while (i) {
56		rp = kmalloc(sizeof(*rp), GFP_KERNEL);
57		if (!rp)
58			goto out_nomem;
59		list_add(&rp->c_lru, &lru_head);
60		rp->c_state = RC_UNUSED;
61		rp->c_type = RC_NOCACHE;
62		INIT_HLIST_NODE(&rp->c_hash);
63		i--;
64	}
65
66	cache_hash = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
67	if (!cache_hash)
68		goto out_nomem;
69
70	cache_disabled = 0;
71	return 0;
72out_nomem:
73	printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
74	nfsd_reply_cache_shutdown();
75	return -ENOMEM;
76}
77
78void nfsd_reply_cache_shutdown(void)
79{
80	struct svc_cacherep	*rp;
81
82	while (!list_empty(&lru_head)) {
83		rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
84		if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
85			kfree(rp->c_replvec.iov_base);
86		list_del(&rp->c_lru);
87		kfree(rp);
88	}
89
90	cache_disabled = 1;
91
92	kfree (cache_hash);
93	cache_hash = NULL;
94}
95
96/*
97 * Move cache entry to end of LRU list
98 */
99static void
100lru_put_end(struct svc_cacherep *rp)
101{
102	list_move_tail(&rp->c_lru, &lru_head);
103}
104
105/*
106 * Move a cache entry from one hash list to another
107 */
108static void
109hash_refile(struct svc_cacherep *rp)
110{
111	hlist_del_init(&rp->c_hash);
112	hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid));
113}
114
115/*
116 * Try to find an entry matching the current call in the cache. When none
117 * is found, we grab the oldest unlocked entry off the LRU list.
118 * Note that no operation within the loop may sleep.
119 */
120int
121nfsd_cache_lookup(struct svc_rqst *rqstp, int type)
122{
123	struct hlist_node	*hn;
124	struct hlist_head 	*rh;
125	struct svc_cacherep	*rp;
126	__be32			xid = rqstp->rq_xid;
127	u32			proto =  rqstp->rq_prot,
128				vers = rqstp->rq_vers,
129				proc = rqstp->rq_proc;
130	unsigned long		age;
131	int rtn;
132
133	rqstp->rq_cacherep = NULL;
134	if (cache_disabled || type == RC_NOCACHE) {
135		nfsdstats.rcnocache++;
136		return RC_DOIT;
137	}
138
139	spin_lock(&cache_lock);
140	rtn = RC_DOIT;
141
142	rh = &cache_hash[request_hash(xid)];
143	hlist_for_each_entry(rp, hn, rh, c_hash) {
144		if (rp->c_state != RC_UNUSED &&
145		    xid == rp->c_xid && proc == rp->c_proc &&
146		    proto == rp->c_prot && vers == rp->c_vers &&
147		    time_before(jiffies, rp->c_timestamp + 120*HZ) &&
148		    memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) {
149			nfsdstats.rchits++;
150			goto found_entry;
151		}
152	}
153	nfsdstats.rcmisses++;
154
155	/* This loop shouldn't take more than a few iterations normally */
156	{
157	int	safe = 0;
158	list_for_each_entry(rp, &lru_head, c_lru) {
159		if (rp->c_state != RC_INPROG)
160			break;
161		if (safe++ > CACHESIZE) {
162			printk("nfsd: loop in repcache LRU list\n");
163			cache_disabled = 1;
164			goto out;
165		}
166	}
167	}
168
169	/* All entries on the LRU are in-progress. This should not happen */
170	if (&rp->c_lru == &lru_head) {
171		static int	complaints;
172
173		printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
174		if (++complaints > 5) {
175			printk(KERN_WARNING "nfsd: disabling repcache.\n");
176			cache_disabled = 1;
177		}
178		goto out;
179	}
180
181	rqstp->rq_cacherep = rp;
182	rp->c_state = RC_INPROG;
183	rp->c_xid = xid;
184	rp->c_proc = proc;
185	memcpy(&rp->c_addr, svc_addr_in(rqstp), sizeof(rp->c_addr));
186	rp->c_prot = proto;
187	rp->c_vers = vers;
188	rp->c_timestamp = jiffies;
189
190	hash_refile(rp);
191
192	/* release any buffer */
193	if (rp->c_type == RC_REPLBUFF) {
194		kfree(rp->c_replvec.iov_base);
195		rp->c_replvec.iov_base = NULL;
196	}
197	rp->c_type = RC_NOCACHE;
198 out:
199	spin_unlock(&cache_lock);
200	return rtn;
201
202found_entry:
203	/* We found a matching entry which is either in progress or done. */
204	age = jiffies - rp->c_timestamp;
205	rp->c_timestamp = jiffies;
206	lru_put_end(rp);
207
208	rtn = RC_DROPIT;
209	/* Request being processed or excessive rexmits */
210	if (rp->c_state == RC_INPROG || age < RC_DELAY)
211		goto out;
212
213	/* From the hall of fame of impractical attacks:
214	 * Is this a user who tries to snoop on the cache? */
215	rtn = RC_DOIT;
216	if (!rqstp->rq_secure && rp->c_secure)
217		goto out;
218
219	/* Compose RPC reply header */
220	switch (rp->c_type) {
221	case RC_NOCACHE:
222		break;
223	case RC_REPLSTAT:
224		svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
225		rtn = RC_REPLY;
226		break;
227	case RC_REPLBUFF:
228		if (!nfsd_cache_append(rqstp, &rp->c_replvec))
229			goto out;	/* should not happen */
230		rtn = RC_REPLY;
231		break;
232	default:
233		printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
234		rp->c_state = RC_UNUSED;
235	}
236
237	goto out;
238}
239
240/*
241 * Update a cache entry. This is called from nfsd_dispatch when
242 * the procedure has been executed and the complete reply is in
243 * rqstp->rq_res.
244 *
245 * We're copying around data here rather than swapping buffers because
246 * the toplevel loop requires max-sized buffers, which would be a waste
247 * of memory for a cache with a max reply size of 100 bytes (diropokres).
248 *
249 * If we should start to use different types of cache entries tailored
250 * specifically for attrstat and fh's, we may save even more space.
251 *
252 * Also note that a cachetype of RC_NOCACHE can legally be passed when
253 * nfsd failed to encode a reply that otherwise would have been cached.
254 * In this case, nfsd_cache_update is called with statp == NULL.
255 */
256void
257nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
258{
259	struct svc_cacherep *rp;
260	struct kvec	*resv = &rqstp->rq_res.head[0], *cachv;
261	int		len;
262
263	if (!(rp = rqstp->rq_cacherep) || cache_disabled)
264		return;
265
266	len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
267	len >>= 2;
268
269	/* Don't cache excessive amounts of data and XDR failures */
270	if (!statp || len > (256 >> 2)) {
271		rp->c_state = RC_UNUSED;
272		return;
273	}
274
275	switch (cachetype) {
276	case RC_REPLSTAT:
277		if (len != 1)
278			printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
279		rp->c_replstat = *statp;
280		break;
281	case RC_REPLBUFF:
282		cachv = &rp->c_replvec;
283		cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
284		if (!cachv->iov_base) {
285			spin_lock(&cache_lock);
286			rp->c_state = RC_UNUSED;
287			spin_unlock(&cache_lock);
288			return;
289		}
290		cachv->iov_len = len << 2;
291		memcpy(cachv->iov_base, statp, len << 2);
292		break;
293	}
294	spin_lock(&cache_lock);
295	lru_put_end(rp);
296	rp->c_secure = rqstp->rq_secure;
297	rp->c_type = cachetype;
298	rp->c_state = RC_DONE;
299	rp->c_timestamp = jiffies;
300	spin_unlock(&cache_lock);
301	return;
302}
303
304static int
305nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
306{
307	struct kvec	*vec = &rqstp->rq_res.head[0];
308
309	if (vec->iov_len + data->iov_len > PAGE_SIZE) {
310		printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
311				data->iov_len);
312		return 0;
313	}
314	memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
315	vec->iov_len += data->iov_len;
316	return 1;
317}
318