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 33 static struct hlist_head * cache_hash; 34 static struct list_head lru_head; 35 static int cache_disabled = 1; 36 37 /* 38 * Calculate the hash index from an XID. 39 */ 40 static inline u32 request_hash(u32 xid) 41 { 42 u32 h = xid; 43 h ^= (xid >> 24); 44 return h & (HASHSIZE-1); 45 } 46 47 static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec); 48 49 /* 50 * locking for the reply cache: 51 * A cache entry is "single use" if c_state == RC_INPROG 52 * Otherwise, it when accessing _prev or _next, the lock must be held. 53 */ 54 static DEFINE_SPINLOCK(cache_lock); 55 56 int nfsd_reply_cache_init(void) 57 { 58 struct svc_cacherep *rp; 59 int i; 60 61 INIT_LIST_HEAD(&lru_head); 62 i = CACHESIZE; 63 while (i) { 64 rp = kmalloc(sizeof(*rp), GFP_KERNEL); 65 if (!rp) 66 goto out_nomem; 67 list_add(&rp->c_lru, &lru_head); 68 rp->c_state = RC_UNUSED; 69 rp->c_type = RC_NOCACHE; 70 INIT_HLIST_NODE(&rp->c_hash); 71 i--; 72 } 73 74 cache_hash = kcalloc (HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL); 75 if (!cache_hash) 76 goto out_nomem; 77 78 cache_disabled = 0; 79 return 0; 80 out_nomem: 81 printk(KERN_ERR "nfsd: failed to allocate reply cache\n"); 82 nfsd_reply_cache_shutdown(); 83 return -ENOMEM; 84 } 85 86 void nfsd_reply_cache_shutdown(void) 87 { 88 struct svc_cacherep *rp; 89 90 while (!list_empty(&lru_head)) { 91 rp = list_entry(lru_head.next, struct svc_cacherep, c_lru); 92 if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF) 93 kfree(rp->c_replvec.iov_base); 94 list_del(&rp->c_lru); 95 kfree(rp); 96 } 97 98 cache_disabled = 1; 99 100 kfree (cache_hash); 101 cache_hash = NULL; 102 } 103 104 /* 105 * Move cache entry to end of LRU list 106 */ 107 static void 108 lru_put_end(struct svc_cacherep *rp) 109 { 110 list_move_tail(&rp->c_lru, &lru_head); 111 } 112 113 /* 114 * Move a cache entry from one hash list to another 115 */ 116 static void 117 hash_refile(struct svc_cacherep *rp) 118 { 119 hlist_del_init(&rp->c_hash); 120 hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid)); 121 } 122 123 /* 124 * Try to find an entry matching the current call in the cache. When none 125 * is found, we grab the oldest unlocked entry off the LRU list. 126 * Note that no operation within the loop may sleep. 127 */ 128 int 129 nfsd_cache_lookup(struct svc_rqst *rqstp, int type) 130 { 131 struct hlist_node *hn; 132 struct hlist_head *rh; 133 struct svc_cacherep *rp; 134 __be32 xid = rqstp->rq_xid; 135 u32 proto = rqstp->rq_prot, 136 vers = rqstp->rq_vers, 137 proc = rqstp->rq_proc; 138 unsigned long age; 139 int rtn; 140 141 rqstp->rq_cacherep = NULL; 142 if (cache_disabled || type == RC_NOCACHE) { 143 nfsdstats.rcnocache++; 144 return RC_DOIT; 145 } 146 147 spin_lock(&cache_lock); 148 rtn = RC_DOIT; 149 150 rh = &cache_hash[request_hash(xid)]; 151 hlist_for_each_entry(rp, hn, rh, c_hash) { 152 if (rp->c_state != RC_UNUSED && 153 xid == rp->c_xid && proc == rp->c_proc && 154 proto == rp->c_prot && vers == rp->c_vers && 155 time_before(jiffies, rp->c_timestamp + 120*HZ) && 156 memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) { 157 nfsdstats.rchits++; 158 goto found_entry; 159 } 160 } 161 nfsdstats.rcmisses++; 162 163 /* This loop shouldn't take more than a few iterations normally */ 164 { 165 int safe = 0; 166 list_for_each_entry(rp, &lru_head, c_lru) { 167 if (rp->c_state != RC_INPROG) 168 break; 169 if (safe++ > CACHESIZE) { 170 printk("nfsd: loop in repcache LRU list\n"); 171 cache_disabled = 1; 172 goto out; 173 } 174 } 175 } 176 177 /* All entries on the LRU are in-progress. This should not happen */ 178 if (&rp->c_lru == &lru_head) { 179 static int complaints; 180 181 printk(KERN_WARNING "nfsd: all repcache entries locked!\n"); 182 if (++complaints > 5) { 183 printk(KERN_WARNING "nfsd: disabling repcache.\n"); 184 cache_disabled = 1; 185 } 186 goto out; 187 } 188 189 rqstp->rq_cacherep = rp; 190 rp->c_state = RC_INPROG; 191 rp->c_xid = xid; 192 rp->c_proc = proc; 193 memcpy(&rp->c_addr, svc_addr_in(rqstp), sizeof(rp->c_addr)); 194 rp->c_prot = proto; 195 rp->c_vers = vers; 196 rp->c_timestamp = jiffies; 197 198 hash_refile(rp); 199 200 /* release any buffer */ 201 if (rp->c_type == RC_REPLBUFF) { 202 kfree(rp->c_replvec.iov_base); 203 rp->c_replvec.iov_base = NULL; 204 } 205 rp->c_type = RC_NOCACHE; 206 out: 207 spin_unlock(&cache_lock); 208 return rtn; 209 210 found_entry: 211 /* We found a matching entry which is either in progress or done. */ 212 age = jiffies - rp->c_timestamp; 213 rp->c_timestamp = jiffies; 214 lru_put_end(rp); 215 216 rtn = RC_DROPIT; 217 /* Request being processed or excessive rexmits */ 218 if (rp->c_state == RC_INPROG || age < RC_DELAY) 219 goto out; 220 221 /* From the hall of fame of impractical attacks: 222 * Is this a user who tries to snoop on the cache? */ 223 rtn = RC_DOIT; 224 if (!rqstp->rq_secure && rp->c_secure) 225 goto out; 226 227 /* Compose RPC reply header */ 228 switch (rp->c_type) { 229 case RC_NOCACHE: 230 break; 231 case RC_REPLSTAT: 232 svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat); 233 rtn = RC_REPLY; 234 break; 235 case RC_REPLBUFF: 236 if (!nfsd_cache_append(rqstp, &rp->c_replvec)) 237 goto out; /* should not happen */ 238 rtn = RC_REPLY; 239 break; 240 default: 241 printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type); 242 rp->c_state = RC_UNUSED; 243 } 244 245 goto out; 246 } 247 248 /* 249 * Update a cache entry. This is called from nfsd_dispatch when 250 * the procedure has been executed and the complete reply is in 251 * rqstp->rq_res. 252 * 253 * We're copying around data here rather than swapping buffers because 254 * the toplevel loop requires max-sized buffers, which would be a waste 255 * of memory for a cache with a max reply size of 100 bytes (diropokres). 256 * 257 * If we should start to use different types of cache entries tailored 258 * specifically for attrstat and fh's, we may save even more space. 259 * 260 * Also note that a cachetype of RC_NOCACHE can legally be passed when 261 * nfsd failed to encode a reply that otherwise would have been cached. 262 * In this case, nfsd_cache_update is called with statp == NULL. 263 */ 264 void 265 nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp) 266 { 267 struct svc_cacherep *rp; 268 struct kvec *resv = &rqstp->rq_res.head[0], *cachv; 269 int len; 270 271 if (!(rp = rqstp->rq_cacherep) || cache_disabled) 272 return; 273 274 len = resv->iov_len - ((char*)statp - (char*)resv->iov_base); 275 len >>= 2; 276 277 /* Don't cache excessive amounts of data and XDR failures */ 278 if (!statp || len > (256 >> 2)) { 279 rp->c_state = RC_UNUSED; 280 return; 281 } 282 283 switch (cachetype) { 284 case RC_REPLSTAT: 285 if (len != 1) 286 printk("nfsd: RC_REPLSTAT/reply len %d!\n",len); 287 rp->c_replstat = *statp; 288 break; 289 case RC_REPLBUFF: 290 cachv = &rp->c_replvec; 291 cachv->iov_base = kmalloc(len << 2, GFP_KERNEL); 292 if (!cachv->iov_base) { 293 spin_lock(&cache_lock); 294 rp->c_state = RC_UNUSED; 295 spin_unlock(&cache_lock); 296 return; 297 } 298 cachv->iov_len = len << 2; 299 memcpy(cachv->iov_base, statp, len << 2); 300 break; 301 } 302 spin_lock(&cache_lock); 303 lru_put_end(rp); 304 rp->c_secure = rqstp->rq_secure; 305 rp->c_type = cachetype; 306 rp->c_state = RC_DONE; 307 rp->c_timestamp = jiffies; 308 spin_unlock(&cache_lock); 309 return; 310 } 311 312 /* 313 * Copy cached reply to current reply buffer. Should always fit. 314 * FIXME as reply is in a page, we should just attach the page, and 315 * keep a refcount.... 316 */ 317 static int 318 nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data) 319 { 320 struct kvec *vec = &rqstp->rq_res.head[0]; 321 322 if (vec->iov_len + data->iov_len > PAGE_SIZE) { 323 printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n", 324 data->iov_len); 325 return 0; 326 } 327 memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len); 328 vec->iov_len += data->iov_len; 329 return 1; 330 } 331