revert-mm-fix-blkdev-size-calculation-in-generic_write_checks
[linux-2.6/linux-trees-mm.git] / fs / nfsd / nfscache.c
blob92cb5ae4d68c3f5619d922f75dce2bc8528e5c49
1 /*
2 * linux/fs/nfsd/nfscache.c
4 * Request reply cache. This is currently a global cache, but this may
5 * change in the future and be a per-client cache.
7 * This code is heavily inspired by the 44BSD implementation, although
8 * it does things a bit differently.
10 * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
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>
20 #include <linux/sunrpc/svc.h>
21 #include <linux/nfsd/nfsd.h>
22 #include <linux/nfsd/cache.h>
24 /* Size of reply cache. Common values are:
25 * 4.3BSD: 128
26 * 4.4BSD: 256
27 * Solaris2: 1024
28 * DEC Unix: 512-4096
30 #define CACHESIZE 1024
31 #define HASHSIZE 64
32 #define REQHASH(xid) (((((__force __u32)xid) >> 24) ^ ((__force __u32)xid)) & (HASHSIZE-1))
34 static struct hlist_head * hash_list;
35 static struct list_head lru_head;
36 static int cache_disabled = 1;
38 static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
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.
45 static DEFINE_SPINLOCK(cache_lock);
47 int
48 nfsd_reply_cache_init(void)
50 struct svc_cacherep *rp;
51 int i;
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--;
66 hash_list = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
67 if (!hash_list)
68 goto out_nomem;
70 cache_disabled = 0;
71 return 0;
72 out_nomem:
73 printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
74 nfsd_reply_cache_shutdown();
75 return -ENOMEM;
78 void
79 nfsd_reply_cache_shutdown(void)
81 struct svc_cacherep *rp;
83 while (!list_empty(&lru_head)) {
84 rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
85 if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
86 kfree(rp->c_replvec.iov_base);
87 list_del(&rp->c_lru);
88 kfree(rp);
91 cache_disabled = 1;
93 kfree (hash_list);
94 hash_list = NULL;
98 * Move cache entry to end of LRU list
100 static void
101 lru_put_end(struct svc_cacherep *rp)
103 list_move_tail(&rp->c_lru, &lru_head);
107 * Move a cache entry from one hash list to another
109 static void
110 hash_refile(struct svc_cacherep *rp)
112 hlist_del_init(&rp->c_hash);
113 hlist_add_head(&rp->c_hash, hash_list + REQHASH(rp->c_xid));
117 * Try to find an entry matching the current call in the cache. When none
118 * is found, we grab the oldest unlocked entry off the LRU list.
119 * Note that no operation within the loop may sleep.
122 nfsd_cache_lookup(struct svc_rqst *rqstp, int type)
124 struct hlist_node *hn;
125 struct hlist_head *rh;
126 struct svc_cacherep *rp;
127 __be32 xid = rqstp->rq_xid;
128 u32 proto = rqstp->rq_prot,
129 vers = rqstp->rq_vers,
130 proc = rqstp->rq_proc;
131 unsigned long age;
132 int rtn;
134 rqstp->rq_cacherep = NULL;
135 if (cache_disabled || type == RC_NOCACHE) {
136 nfsdstats.rcnocache++;
137 return RC_DOIT;
140 spin_lock(&cache_lock);
141 rtn = RC_DOIT;
143 rh = &hash_list[REQHASH(xid)];
144 hlist_for_each_entry(rp, hn, rh, c_hash) {
145 if (rp->c_state != RC_UNUSED &&
146 xid == rp->c_xid && proc == rp->c_proc &&
147 proto == rp->c_prot && vers == rp->c_vers &&
148 time_before(jiffies, rp->c_timestamp + 120*HZ) &&
149 memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) {
150 nfsdstats.rchits++;
151 goto found_entry;
154 nfsdstats.rcmisses++;
156 /* This loop shouldn't take more than a few iterations normally */
158 int safe = 0;
159 list_for_each_entry(rp, &lru_head, c_lru) {
160 if (rp->c_state != RC_INPROG)
161 break;
162 if (safe++ > CACHESIZE) {
163 printk("nfsd: loop in repcache LRU list\n");
164 cache_disabled = 1;
165 goto out;
170 /* This should not happen */
171 if (rp == NULL) {
172 static int complaints;
174 printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
175 if (++complaints > 5) {
176 printk(KERN_WARNING "nfsd: disabling repcache.\n");
177 cache_disabled = 1;
179 goto out;
182 rqstp->rq_cacherep = rp;
183 rp->c_state = RC_INPROG;
184 rp->c_xid = xid;
185 rp->c_proc = proc;
186 memcpy(&rp->c_addr, svc_addr_in(rqstp), sizeof(rp->c_addr));
187 rp->c_prot = proto;
188 rp->c_vers = vers;
189 rp->c_timestamp = jiffies;
191 hash_refile(rp);
193 /* release any buffer */
194 if (rp->c_type == RC_REPLBUFF) {
195 kfree(rp->c_replvec.iov_base);
196 rp->c_replvec.iov_base = NULL;
198 rp->c_type = RC_NOCACHE;
199 out:
200 spin_unlock(&cache_lock);
201 return rtn;
203 found_entry:
204 /* We found a matching entry which is either in progress or done. */
205 age = jiffies - rp->c_timestamp;
206 rp->c_timestamp = jiffies;
207 lru_put_end(rp);
209 rtn = RC_DROPIT;
210 /* Request being processed or excessive rexmits */
211 if (rp->c_state == RC_INPROG || age < RC_DELAY)
212 goto out;
214 /* From the hall of fame of impractical attacks:
215 * Is this a user who tries to snoop on the cache? */
216 rtn = RC_DOIT;
217 if (!rqstp->rq_secure && rp->c_secure)
218 goto out;
220 /* Compose RPC reply header */
221 switch (rp->c_type) {
222 case RC_NOCACHE:
223 break;
224 case RC_REPLSTAT:
225 svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
226 rtn = RC_REPLY;
227 break;
228 case RC_REPLBUFF:
229 if (!nfsd_cache_append(rqstp, &rp->c_replvec))
230 goto out; /* should not happen */
231 rtn = RC_REPLY;
232 break;
233 default:
234 printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
235 rp->c_state = RC_UNUSED;
238 goto out;
242 * Update a cache entry. This is called from nfsd_dispatch when
243 * the procedure has been executed and the complete reply is in
244 * rqstp->rq_res.
246 * We're copying around data here rather than swapping buffers because
247 * the toplevel loop requires max-sized buffers, which would be a waste
248 * of memory for a cache with a max reply size of 100 bytes (diropokres).
250 * If we should start to use different types of cache entries tailored
251 * specifically for attrstat and fh's, we may save even more space.
253 * Also note that a cachetype of RC_NOCACHE can legally be passed when
254 * nfsd failed to encode a reply that otherwise would have been cached.
255 * In this case, nfsd_cache_update is called with statp == NULL.
257 void
258 nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
260 struct svc_cacherep *rp;
261 struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
262 int len;
264 if (!(rp = rqstp->rq_cacherep) || cache_disabled)
265 return;
267 len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
268 len >>= 2;
270 /* Don't cache excessive amounts of data and XDR failures */
271 if (!statp || len > (256 >> 2)) {
272 rp->c_state = RC_UNUSED;
273 return;
276 switch (cachetype) {
277 case RC_REPLSTAT:
278 if (len != 1)
279 printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
280 rp->c_replstat = *statp;
281 break;
282 case RC_REPLBUFF:
283 cachv = &rp->c_replvec;
284 cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
285 if (!cachv->iov_base) {
286 spin_lock(&cache_lock);
287 rp->c_state = RC_UNUSED;
288 spin_unlock(&cache_lock);
289 return;
291 cachv->iov_len = len << 2;
292 memcpy(cachv->iov_base, statp, len << 2);
293 break;
295 spin_lock(&cache_lock);
296 lru_put_end(rp);
297 rp->c_secure = rqstp->rq_secure;
298 rp->c_type = cachetype;
299 rp->c_state = RC_DONE;
300 rp->c_timestamp = jiffies;
301 spin_unlock(&cache_lock);
302 return;
306 * Copy cached reply to current reply buffer. Should always fit.
307 * FIXME as reply is in a page, we should just attach the page, and
308 * keep a refcount....
310 static int
311 nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
313 struct kvec *vec = &rqstp->rq_res.head[0];
315 if (vec->iov_len + data->iov_len > PAGE_SIZE) {
316 printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
317 data->iov_len);
318 return 0;
320 memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
321 vec->iov_len += data->iov_len;
322 return 1;