1 /*
2 * linux/fs/nfsd/nfscache.c
3 *
4 * Request reply cache. This is currently a global cache, but this may
5 * change in the future and be a per-client cache.
6 *
7 * This code is heavily inspired by the 44BSD implementation, although
8 * it does things a bit differently.
9 *
10 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
11 */
12
13 #include <linux/kernel.h>
14 #include <linux/time.h>
15 #include <linux/slab.h>
16 #include <linux/string.h>
17 #include <linux/spinlock.h>
18 #include <linux/list.h>
19
20 #include <linux/sunrpc/svc.h>
21 #include <linux/nfsd/nfsd.h>
22 #include <linux/nfsd/cache.h>
23
24 /* Size of reply cache. Common values are:
25 * 4.3BSD: 128
26 * 4.4BSD: 256
27 * Solaris2: 1024
28 * DEC Unix: 512-4096
29 */
30 #define CACHESIZE 1024
31 #define HASHSIZE 64
32 #define REQHASH(xid) (((((__force __u32)xid) >> 24) ^ ((__force __u32)xid)) & (HASHSIZE-1))
33
34 static struct hlist_head * hash_list;
35 static struct list_head lru_head;
36 static int cache_disabled = 1;
37
38 static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
39
40 /*
41 * locking for the reply cache:
42 * A cache entry is "single use" if c_state == RC_INPROG
43 * Otherwise, it when accessing _prev or _next, the lock must be held.
44 */
45 static DEFINE_SPINLOCK(cache_lock);
46
47 int nfsd_reply_cache_init(void)
48 {
49 struct svc_cacherep *rp;
50 int i;
51
52 INIT_LIST_HEAD(&lru_head);
53 i = CACHESIZE;
54 while (i) {
55 rp = kmalloc(sizeof(*rp), GFP_KERNEL);
56 if (!rp)
57 goto out_nomem;
58 list_add(&rp->c_lru, &lru_head);
59 rp->c_state = RC_UNUSED;
60 rp->c_type = RC_NOCACHE;
61 INIT_HLIST_NODE(&rp->c_hash);
62 i--;
63 }
64
65 hash_list = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
66 if (!hash_list)
67 goto out_nomem;
68
69 cache_disabled = 0;
70 return 0;
71 out_nomem:
72 printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
73 nfsd_reply_cache_shutdown();
74 return -ENOMEM;
75 }
76
77 void nfsd_reply_cache_shutdown(void)
78 {
79 struct svc_cacherep *rp;
80
81 while (!list_empty(&lru_head)) {
82 rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
83 if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
84 kfree(rp->c_replvec.iov_base);
85 list_del(&rp->c_lru);
86 kfree(rp);
87 }
88
89 cache_disabled = 1;
90
91 kfree (hash_list);
92 hash_list = NULL;
93 }
94
95 /*
96 * Move cache entry to end of LRU list
97 */
98 static void
99 lru_put_end(struct svc_cacherep *rp)
100 {
101 list_move_tail(&rp->c_lru, &lru_head);
102 }
103
104 /*
105 * Move a cache entry from one hash list to another
106 */
107 static void
108 hash_refile(struct svc_cacherep *rp)
109 {
110 hlist_del_init(&rp->c_hash);
111 hlist_add_head(&rp->c_hash, hash_list + REQHASH(rp->c_xid));
112 }
113
114 /*
115 * Try to find an entry matching the current call in the cache. When none
116 * is found, we grab the oldest unlocked entry off the LRU list.
117 * Note that no operation within the loop may sleep.
118 */
119 int
120 nfsd_cache_lookup(struct svc_rqst *rqstp, int type)
121 {
122 struct hlist_node *hn;
123 struct hlist_head *rh;
124 struct svc_cacherep *rp;
125 __be32 xid = rqstp->rq_xid;
126 u32 proto = rqstp->rq_prot,
127 vers = rqstp->rq_vers,
128 proc = rqstp->rq_proc;
129 unsigned long age;
130 int rtn;
131
132 rqstp->rq_cacherep = NULL;
133 if (cache_disabled || type == RC_NOCACHE) {
134 nfsdstats.rcnocache++;
135 return RC_DOIT;
136 }
137
138 spin_lock(&cache_lock);
139 rtn = RC_DOIT;
140
141 rh = &hash_list[REQHASH(xid)];
142 hlist_for_each_entry(rp, hn, rh, c_hash) {
143 if (rp->c_state != RC_UNUSED &&
144 xid == rp->c_xid && proc == rp->c_proc &&
145 proto == rp->c_prot && vers == rp->c_vers &&
146 time_before(jiffies, rp->c_timestamp + 120*HZ) &&
147 memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) {
148 nfsdstats.rchits++;
149 goto found_entry;
150 }
151 }
152 nfsdstats.rcmisses++;
153
154 /* This loop shouldn't take more than a few iterations normally */
155 {
156 int safe = 0;
157 list_for_each_entry(rp, &lru_head, c_lru) {
158 if (rp->c_state != RC_INPROG)
159 break;
160 if (safe++ > CACHESIZE) {
161 printk("nfsd: loop in repcache LRU list\n");
162 cache_disabled = 1;
163 goto out;
164 }
165 }
166 }
167
168 /* This should not happen */
169 if (rp == NULL) {
170 static int complaints;
171
172 printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
173 if (++complaints > 5) {
174 printk(KERN_WARNING "nfsd: disabling repcache.\n");
175 cache_disabled = 1;
176 }
177 goto out;
178 }
179
180 rqstp->rq_cacherep = rp;
181 rp->c_state = RC_INPROG;
182 rp->c_xid = xid;
183 rp->c_proc = proc;
184 memcpy(&rp->c_addr, svc_addr_in(rqstp), sizeof(rp->c_addr));
185 rp->c_prot = proto;
186 rp->c_vers = vers;
187 rp->c_timestamp = jiffies;
188
189 hash_refile(rp);
190
191 /* release any buffer */
192 if (rp->c_type == RC_REPLBUFF) {
193 kfree(rp->c_replvec.iov_base);
194 rp->c_replvec.iov_base = NULL;
195 }
196 rp->c_type = RC_NOCACHE;
197 out:
198 spin_unlock(&cache_lock);
199 return rtn;
200
201 found_entry:
202 /* We found a matching entry which is either in progress or done. */
203 age = jiffies - rp->c_timestamp;
204 rp->c_timestamp = jiffies;
205 lru_put_end(rp);
206
207 rtn = RC_DROPIT;
208 /* Request being processed or excessive rexmits */
209 if (rp->c_state == RC_INPROG || age < RC_DELAY)
210 goto out;
211
212 /* From the hall of fame of impractical attacks:
213 * Is this a user who tries to snoop on the cache? */
214 rtn = RC_DOIT;
215 if (!rqstp->rq_secure && rp->c_secure)
216 goto out;
217
218 /* Compose RPC reply header */
219 switch (rp->c_type) {
220 case RC_NOCACHE:
221 break;
222 case RC_REPLSTAT:
223 svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
224 rtn = RC_REPLY;
225 break;
226 case RC_REPLBUFF:
227 if (!nfsd_cache_append(rqstp, &rp->c_replvec))
228 goto out; /* should not happen */
229 rtn = RC_REPLY;
230 break;
231 default:
232 printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
233 rp->c_state = RC_UNUSED;
234 }
235
236 goto out;
237 }
238
239 /*
240 * Update a cache entry. This is called from nfsd_dispatch when
241 * the procedure has been executed and the complete reply is in
242 * rqstp->rq_res.
243 *
244 * We're copying around data here rather than swapping buffers because
245 * the toplevel loop requires max-sized buffers, which would be a waste
246 * of memory for a cache with a max reply size of 100 bytes (diropokres).
247 *
248 * If we should start to use different types of cache entries tailored
249 * specifically for attrstat and fh's, we may save even more space.
250 *
251 * Also note that a cachetype of RC_NOCACHE can legally be passed when
252 * nfsd failed to encode a reply that otherwise would have been cached.
253 * In this case, nfsd_cache_update is called with statp == NULL.
254 */
255 void
256 nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
257 {
258 struct svc_cacherep *rp;
259 struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
260 int len;
261
262 if (!(rp = rqstp->rq_cacherep) || cache_disabled)
263 return;
264
265 len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
266 len >>= 2;
267
268 /* Don't cache excessive amounts of data and XDR failures */
269 if (!statp || len > (256 >> 2)) {
270 rp->c_state = RC_UNUSED;
271 return;
272 }
273
274 switch (cachetype) {
275 case RC_REPLSTAT:
276 if (len != 1)
277 printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
278 rp->c_replstat = *statp;
279 break;
280 case RC_REPLBUFF:
281 cachv = &rp->c_replvec;
282 cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
283 if (!cachv->iov_base) {
284 spin_lock(&cache_lock);
285 rp->c_state = RC_UNUSED;
286 spin_unlock(&cache_lock);
287 return;
288 }
289 cachv->iov_len = len << 2;
290 memcpy(cachv->iov_base, statp, len << 2);
291 break;
292 }
293 spin_lock(&cache_lock);
294 lru_put_end(rp);
295 rp->c_secure = rqstp->rq_secure;
296 rp->c_type = cachetype;
297 rp->c_state = RC_DONE;
298 rp->c_timestamp = jiffies;
299 spin_unlock(&cache_lock);
300 return;
301 }
302
303 /*
304 * Copy cached reply to current reply buffer. Should always fit.
305 * FIXME as reply is in a page, we should just attach the page, and
306 * keep a refcount....
307 */
308 static int
309 nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
310 {
311 struct kvec *vec = &rqstp->rq_res.head[0];
312
313 if (vec->iov_len + data->iov_len > PAGE_SIZE) {
314 printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
315 data->iov_len);
316 return 0;
317 }
318 memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
319 vec->iov_len += data->iov_len;
320 return 1;
321 }
322
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