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0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Request reply cache. This is currently a global cache, but this may
0004  * change in the future and be a per-client cache.
0005  *
0006  * This code is heavily inspired by the 44BSD implementation, although
0007  * it does things a bit differently.
0008  *
0009  * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
0010  */
0011 
0012 #include <linux/sunrpc/svc_xprt.h>
0013 #include <linux/slab.h>
0014 #include <linux/vmalloc.h>
0015 #include <linux/sunrpc/addr.h>
0016 #include <linux/highmem.h>
0017 #include <linux/log2.h>
0018 #include <linux/hash.h>
0019 #include <net/checksum.h>
0020 
0021 #include "nfsd.h"
0022 #include "cache.h"
0023 #include "trace.h"
0024 
0025 /*
0026  * We use this value to determine the number of hash buckets from the max
0027  * cache size, the idea being that when the cache is at its maximum number
0028  * of entries, then this should be the average number of entries per bucket.
0029  */
0030 #define TARGET_BUCKET_SIZE  64
0031 
0032 struct nfsd_drc_bucket {
0033     struct rb_root rb_head;
0034     struct list_head lru_head;
0035     spinlock_t cache_lock;
0036 };
0037 
0038 static struct kmem_cache    *drc_slab;
0039 
0040 static int  nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
0041 static unsigned long nfsd_reply_cache_count(struct shrinker *shrink,
0042                         struct shrink_control *sc);
0043 static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink,
0044                        struct shrink_control *sc);
0045 
0046 /*
0047  * Put a cap on the size of the DRC based on the amount of available
0048  * low memory in the machine.
0049  *
0050  *  64MB:    8192
0051  * 128MB:   11585
0052  * 256MB:   16384
0053  * 512MB:   23170
0054  *   1GB:   32768
0055  *   2GB:   46340
0056  *   4GB:   65536
0057  *   8GB:   92681
0058  *  16GB:  131072
0059  *
0060  * ...with a hard cap of 256k entries. In the worst case, each entry will be
0061  * ~1k, so the above numbers should give a rough max of the amount of memory
0062  * used in k.
0063  *
0064  * XXX: these limits are per-container, so memory used will increase
0065  * linearly with number of containers.  Maybe that's OK.
0066  */
0067 static unsigned int
0068 nfsd_cache_size_limit(void)
0069 {
0070     unsigned int limit;
0071     unsigned long low_pages = totalram_pages() - totalhigh_pages();
0072 
0073     limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10);
0074     return min_t(unsigned int, limit, 256*1024);
0075 }
0076 
0077 /*
0078  * Compute the number of hash buckets we need. Divide the max cachesize by
0079  * the "target" max bucket size, and round up to next power of two.
0080  */
0081 static unsigned int
0082 nfsd_hashsize(unsigned int limit)
0083 {
0084     return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE);
0085 }
0086 
0087 static struct svc_cacherep *
0088 nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum,
0089             struct nfsd_net *nn)
0090 {
0091     struct svc_cacherep *rp;
0092 
0093     rp = kmem_cache_alloc(drc_slab, GFP_KERNEL);
0094     if (rp) {
0095         rp->c_state = RC_UNUSED;
0096         rp->c_type = RC_NOCACHE;
0097         RB_CLEAR_NODE(&rp->c_node);
0098         INIT_LIST_HEAD(&rp->c_lru);
0099 
0100         memset(&rp->c_key, 0, sizeof(rp->c_key));
0101         rp->c_key.k_xid = rqstp->rq_xid;
0102         rp->c_key.k_proc = rqstp->rq_proc;
0103         rpc_copy_addr((struct sockaddr *)&rp->c_key.k_addr, svc_addr(rqstp));
0104         rpc_set_port((struct sockaddr *)&rp->c_key.k_addr, rpc_get_port(svc_addr(rqstp)));
0105         rp->c_key.k_prot = rqstp->rq_prot;
0106         rp->c_key.k_vers = rqstp->rq_vers;
0107         rp->c_key.k_len = rqstp->rq_arg.len;
0108         rp->c_key.k_csum = csum;
0109     }
0110     return rp;
0111 }
0112 
0113 static void
0114 nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
0115                 struct nfsd_net *nn)
0116 {
0117     if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
0118         nfsd_stats_drc_mem_usage_sub(nn, rp->c_replvec.iov_len);
0119         kfree(rp->c_replvec.iov_base);
0120     }
0121     if (rp->c_state != RC_UNUSED) {
0122         rb_erase(&rp->c_node, &b->rb_head);
0123         list_del(&rp->c_lru);
0124         atomic_dec(&nn->num_drc_entries);
0125         nfsd_stats_drc_mem_usage_sub(nn, sizeof(*rp));
0126     }
0127     kmem_cache_free(drc_slab, rp);
0128 }
0129 
0130 static void
0131 nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
0132             struct nfsd_net *nn)
0133 {
0134     spin_lock(&b->cache_lock);
0135     nfsd_reply_cache_free_locked(b, rp, nn);
0136     spin_unlock(&b->cache_lock);
0137 }
0138 
0139 int nfsd_drc_slab_create(void)
0140 {
0141     drc_slab = kmem_cache_create("nfsd_drc",
0142                 sizeof(struct svc_cacherep), 0, 0, NULL);
0143     return drc_slab ? 0: -ENOMEM;
0144 }
0145 
0146 void nfsd_drc_slab_free(void)
0147 {
0148     kmem_cache_destroy(drc_slab);
0149 }
0150 
0151 static int nfsd_reply_cache_stats_init(struct nfsd_net *nn)
0152 {
0153     return nfsd_percpu_counters_init(nn->counter, NFSD_NET_COUNTERS_NUM);
0154 }
0155 
0156 static void nfsd_reply_cache_stats_destroy(struct nfsd_net *nn)
0157 {
0158     nfsd_percpu_counters_destroy(nn->counter, NFSD_NET_COUNTERS_NUM);
0159 }
0160 
0161 int nfsd_reply_cache_init(struct nfsd_net *nn)
0162 {
0163     unsigned int hashsize;
0164     unsigned int i;
0165     int status = 0;
0166 
0167     nn->max_drc_entries = nfsd_cache_size_limit();
0168     atomic_set(&nn->num_drc_entries, 0);
0169     hashsize = nfsd_hashsize(nn->max_drc_entries);
0170     nn->maskbits = ilog2(hashsize);
0171 
0172     status = nfsd_reply_cache_stats_init(nn);
0173     if (status)
0174         goto out_nomem;
0175 
0176     nn->nfsd_reply_cache_shrinker.scan_objects = nfsd_reply_cache_scan;
0177     nn->nfsd_reply_cache_shrinker.count_objects = nfsd_reply_cache_count;
0178     nn->nfsd_reply_cache_shrinker.seeks = 1;
0179     status = register_shrinker(&nn->nfsd_reply_cache_shrinker,
0180                    "nfsd-reply:%s", nn->nfsd_name);
0181     if (status)
0182         goto out_stats_destroy;
0183 
0184     nn->drc_hashtbl = kvzalloc(array_size(hashsize,
0185                 sizeof(*nn->drc_hashtbl)), GFP_KERNEL);
0186     if (!nn->drc_hashtbl)
0187         goto out_shrinker;
0188 
0189     for (i = 0; i < hashsize; i++) {
0190         INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head);
0191         spin_lock_init(&nn->drc_hashtbl[i].cache_lock);
0192     }
0193     nn->drc_hashsize = hashsize;
0194 
0195     return 0;
0196 out_shrinker:
0197     unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
0198 out_stats_destroy:
0199     nfsd_reply_cache_stats_destroy(nn);
0200 out_nomem:
0201     printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
0202     return -ENOMEM;
0203 }
0204 
0205 void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
0206 {
0207     struct svc_cacherep *rp;
0208     unsigned int i;
0209 
0210     unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
0211 
0212     for (i = 0; i < nn->drc_hashsize; i++) {
0213         struct list_head *head = &nn->drc_hashtbl[i].lru_head;
0214         while (!list_empty(head)) {
0215             rp = list_first_entry(head, struct svc_cacherep, c_lru);
0216             nfsd_reply_cache_free_locked(&nn->drc_hashtbl[i],
0217                                     rp, nn);
0218         }
0219     }
0220     nfsd_reply_cache_stats_destroy(nn);
0221 
0222     kvfree(nn->drc_hashtbl);
0223     nn->drc_hashtbl = NULL;
0224     nn->drc_hashsize = 0;
0225 
0226 }
0227 
0228 /*
0229  * Move cache entry to end of LRU list, and queue the cleaner to run if it's
0230  * not already scheduled.
0231  */
0232 static void
0233 lru_put_end(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
0234 {
0235     rp->c_timestamp = jiffies;
0236     list_move_tail(&rp->c_lru, &b->lru_head);
0237 }
0238 
0239 static noinline struct nfsd_drc_bucket *
0240 nfsd_cache_bucket_find(__be32 xid, struct nfsd_net *nn)
0241 {
0242     unsigned int hash = hash_32((__force u32)xid, nn->maskbits);
0243 
0244     return &nn->drc_hashtbl[hash];
0245 }
0246 
0247 static long prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn,
0248              unsigned int max)
0249 {
0250     struct svc_cacherep *rp, *tmp;
0251     long freed = 0;
0252 
0253     list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) {
0254         /*
0255          * Don't free entries attached to calls that are still
0256          * in-progress, but do keep scanning the list.
0257          */
0258         if (rp->c_state == RC_INPROG)
0259             continue;
0260         if (atomic_read(&nn->num_drc_entries) <= nn->max_drc_entries &&
0261             time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
0262             break;
0263         nfsd_reply_cache_free_locked(b, rp, nn);
0264         if (max && freed++ > max)
0265             break;
0266     }
0267     return freed;
0268 }
0269 
0270 static long nfsd_prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn)
0271 {
0272     return prune_bucket(b, nn, 3);
0273 }
0274 
0275 /*
0276  * Walk the LRU list and prune off entries that are older than RC_EXPIRE.
0277  * Also prune the oldest ones when the total exceeds the max number of entries.
0278  */
0279 static long
0280 prune_cache_entries(struct nfsd_net *nn)
0281 {
0282     unsigned int i;
0283     long freed = 0;
0284 
0285     for (i = 0; i < nn->drc_hashsize; i++) {
0286         struct nfsd_drc_bucket *b = &nn->drc_hashtbl[i];
0287 
0288         if (list_empty(&b->lru_head))
0289             continue;
0290         spin_lock(&b->cache_lock);
0291         freed += prune_bucket(b, nn, 0);
0292         spin_unlock(&b->cache_lock);
0293     }
0294     return freed;
0295 }
0296 
0297 static unsigned long
0298 nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
0299 {
0300     struct nfsd_net *nn = container_of(shrink,
0301                 struct nfsd_net, nfsd_reply_cache_shrinker);
0302 
0303     return atomic_read(&nn->num_drc_entries);
0304 }
0305 
0306 static unsigned long
0307 nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
0308 {
0309     struct nfsd_net *nn = container_of(shrink,
0310                 struct nfsd_net, nfsd_reply_cache_shrinker);
0311 
0312     return prune_cache_entries(nn);
0313 }
0314 /*
0315  * Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes
0316  */
0317 static __wsum
0318 nfsd_cache_csum(struct svc_rqst *rqstp)
0319 {
0320     int idx;
0321     unsigned int base;
0322     __wsum csum;
0323     struct xdr_buf *buf = &rqstp->rq_arg;
0324     const unsigned char *p = buf->head[0].iov_base;
0325     size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len,
0326                 RC_CSUMLEN);
0327     size_t len = min(buf->head[0].iov_len, csum_len);
0328 
0329     /* rq_arg.head first */
0330     csum = csum_partial(p, len, 0);
0331     csum_len -= len;
0332 
0333     /* Continue into page array */
0334     idx = buf->page_base / PAGE_SIZE;
0335     base = buf->page_base & ~PAGE_MASK;
0336     while (csum_len) {
0337         p = page_address(buf->pages[idx]) + base;
0338         len = min_t(size_t, PAGE_SIZE - base, csum_len);
0339         csum = csum_partial(p, len, csum);
0340         csum_len -= len;
0341         base = 0;
0342         ++idx;
0343     }
0344     return csum;
0345 }
0346 
0347 static int
0348 nfsd_cache_key_cmp(const struct svc_cacherep *key,
0349             const struct svc_cacherep *rp, struct nfsd_net *nn)
0350 {
0351     if (key->c_key.k_xid == rp->c_key.k_xid &&
0352         key->c_key.k_csum != rp->c_key.k_csum) {
0353         nfsd_stats_payload_misses_inc(nn);
0354         trace_nfsd_drc_mismatch(nn, key, rp);
0355     }
0356 
0357     return memcmp(&key->c_key, &rp->c_key, sizeof(key->c_key));
0358 }
0359 
0360 /*
0361  * Search the request hash for an entry that matches the given rqstp.
0362  * Must be called with cache_lock held. Returns the found entry or
0363  * inserts an empty key on failure.
0364  */
0365 static struct svc_cacherep *
0366 nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key,
0367             struct nfsd_net *nn)
0368 {
0369     struct svc_cacherep *rp, *ret = key;
0370     struct rb_node      **p = &b->rb_head.rb_node,
0371                 *parent = NULL;
0372     unsigned int        entries = 0;
0373     int cmp;
0374 
0375     while (*p != NULL) {
0376         ++entries;
0377         parent = *p;
0378         rp = rb_entry(parent, struct svc_cacherep, c_node);
0379 
0380         cmp = nfsd_cache_key_cmp(key, rp, nn);
0381         if (cmp < 0)
0382             p = &parent->rb_left;
0383         else if (cmp > 0)
0384             p = &parent->rb_right;
0385         else {
0386             ret = rp;
0387             goto out;
0388         }
0389     }
0390     rb_link_node(&key->c_node, parent, p);
0391     rb_insert_color(&key->c_node, &b->rb_head);
0392 out:
0393     /* tally hash chain length stats */
0394     if (entries > nn->longest_chain) {
0395         nn->longest_chain = entries;
0396         nn->longest_chain_cachesize = atomic_read(&nn->num_drc_entries);
0397     } else if (entries == nn->longest_chain) {
0398         /* prefer to keep the smallest cachesize possible here */
0399         nn->longest_chain_cachesize = min_t(unsigned int,
0400                 nn->longest_chain_cachesize,
0401                 atomic_read(&nn->num_drc_entries));
0402     }
0403 
0404     lru_put_end(b, ret);
0405     return ret;
0406 }
0407 
0408 /**
0409  * nfsd_cache_lookup - Find an entry in the duplicate reply cache
0410  * @rqstp: Incoming Call to find
0411  *
0412  * Try to find an entry matching the current call in the cache. When none
0413  * is found, we try to grab the oldest expired entry off the LRU list. If
0414  * a suitable one isn't there, then drop the cache_lock and allocate a
0415  * new one, then search again in case one got inserted while this thread
0416  * didn't hold the lock.
0417  *
0418  * Return values:
0419  *   %RC_DOIT: Process the request normally
0420  *   %RC_REPLY: Reply from cache
0421  *   %RC_DROPIT: Do not process the request further
0422  */
0423 int nfsd_cache_lookup(struct svc_rqst *rqstp)
0424 {
0425     struct nfsd_net     *nn;
0426     struct svc_cacherep *rp, *found;
0427     __wsum          csum;
0428     struct nfsd_drc_bucket  *b;
0429     int type = rqstp->rq_cachetype;
0430     int rtn = RC_DOIT;
0431 
0432     rqstp->rq_cacherep = NULL;
0433     if (type == RC_NOCACHE) {
0434         nfsd_stats_rc_nocache_inc();
0435         goto out;
0436     }
0437 
0438     csum = nfsd_cache_csum(rqstp);
0439 
0440     /*
0441      * Since the common case is a cache miss followed by an insert,
0442      * preallocate an entry.
0443      */
0444     nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
0445     rp = nfsd_reply_cache_alloc(rqstp, csum, nn);
0446     if (!rp)
0447         goto out;
0448 
0449     b = nfsd_cache_bucket_find(rqstp->rq_xid, nn);
0450     spin_lock(&b->cache_lock);
0451     found = nfsd_cache_insert(b, rp, nn);
0452     if (found != rp)
0453         goto found_entry;
0454 
0455     nfsd_stats_rc_misses_inc();
0456     rqstp->rq_cacherep = rp;
0457     rp->c_state = RC_INPROG;
0458 
0459     atomic_inc(&nn->num_drc_entries);
0460     nfsd_stats_drc_mem_usage_add(nn, sizeof(*rp));
0461 
0462     nfsd_prune_bucket(b, nn);
0463 
0464 out_unlock:
0465     spin_unlock(&b->cache_lock);
0466 out:
0467     return rtn;
0468 
0469 found_entry:
0470     /* We found a matching entry which is either in progress or done. */
0471     nfsd_reply_cache_free_locked(NULL, rp, nn);
0472     nfsd_stats_rc_hits_inc();
0473     rtn = RC_DROPIT;
0474     rp = found;
0475 
0476     /* Request being processed */
0477     if (rp->c_state == RC_INPROG)
0478         goto out_trace;
0479 
0480     /* From the hall of fame of impractical attacks:
0481      * Is this a user who tries to snoop on the cache? */
0482     rtn = RC_DOIT;
0483     if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && rp->c_secure)
0484         goto out_trace;
0485 
0486     /* Compose RPC reply header */
0487     switch (rp->c_type) {
0488     case RC_NOCACHE:
0489         break;
0490     case RC_REPLSTAT:
0491         svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
0492         rtn = RC_REPLY;
0493         break;
0494     case RC_REPLBUFF:
0495         if (!nfsd_cache_append(rqstp, &rp->c_replvec))
0496             goto out_unlock; /* should not happen */
0497         rtn = RC_REPLY;
0498         break;
0499     default:
0500         WARN_ONCE(1, "nfsd: bad repcache type %d\n", rp->c_type);
0501     }
0502 
0503 out_trace:
0504     trace_nfsd_drc_found(nn, rqstp, rtn);
0505     goto out_unlock;
0506 }
0507 
0508 /**
0509  * nfsd_cache_update - Update an entry in the duplicate reply cache.
0510  * @rqstp: svc_rqst with a finished Reply
0511  * @cachetype: which cache to update
0512  * @statp: Reply's status code
0513  *
0514  * This is called from nfsd_dispatch when the procedure has been
0515  * executed and the complete reply is in rqstp->rq_res.
0516  *
0517  * We're copying around data here rather than swapping buffers because
0518  * the toplevel loop requires max-sized buffers, which would be a waste
0519  * of memory for a cache with a max reply size of 100 bytes (diropokres).
0520  *
0521  * If we should start to use different types of cache entries tailored
0522  * specifically for attrstat and fh's, we may save even more space.
0523  *
0524  * Also note that a cachetype of RC_NOCACHE can legally be passed when
0525  * nfsd failed to encode a reply that otherwise would have been cached.
0526  * In this case, nfsd_cache_update is called with statp == NULL.
0527  */
0528 void nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
0529 {
0530     struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
0531     struct svc_cacherep *rp = rqstp->rq_cacherep;
0532     struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
0533     struct nfsd_drc_bucket *b;
0534     int     len;
0535     size_t      bufsize = 0;
0536 
0537     if (!rp)
0538         return;
0539 
0540     b = nfsd_cache_bucket_find(rp->c_key.k_xid, nn);
0541 
0542     len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
0543     len >>= 2;
0544 
0545     /* Don't cache excessive amounts of data and XDR failures */
0546     if (!statp || len > (256 >> 2)) {
0547         nfsd_reply_cache_free(b, rp, nn);
0548         return;
0549     }
0550 
0551     switch (cachetype) {
0552     case RC_REPLSTAT:
0553         if (len != 1)
0554             printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
0555         rp->c_replstat = *statp;
0556         break;
0557     case RC_REPLBUFF:
0558         cachv = &rp->c_replvec;
0559         bufsize = len << 2;
0560         cachv->iov_base = kmalloc(bufsize, GFP_KERNEL);
0561         if (!cachv->iov_base) {
0562             nfsd_reply_cache_free(b, rp, nn);
0563             return;
0564         }
0565         cachv->iov_len = bufsize;
0566         memcpy(cachv->iov_base, statp, bufsize);
0567         break;
0568     case RC_NOCACHE:
0569         nfsd_reply_cache_free(b, rp, nn);
0570         return;
0571     }
0572     spin_lock(&b->cache_lock);
0573     nfsd_stats_drc_mem_usage_add(nn, bufsize);
0574     lru_put_end(b, rp);
0575     rp->c_secure = test_bit(RQ_SECURE, &rqstp->rq_flags);
0576     rp->c_type = cachetype;
0577     rp->c_state = RC_DONE;
0578     spin_unlock(&b->cache_lock);
0579     return;
0580 }
0581 
0582 /*
0583  * Copy cached reply to current reply buffer. Should always fit.
0584  * FIXME as reply is in a page, we should just attach the page, and
0585  * keep a refcount....
0586  */
0587 static int
0588 nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
0589 {
0590     struct kvec *vec = &rqstp->rq_res.head[0];
0591 
0592     if (vec->iov_len + data->iov_len > PAGE_SIZE) {
0593         printk(KERN_WARNING "nfsd: cached reply too large (%zd).\n",
0594                 data->iov_len);
0595         return 0;
0596     }
0597     memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
0598     vec->iov_len += data->iov_len;
0599     return 1;
0600 }
0601 
0602 /*
0603  * Note that fields may be added, removed or reordered in the future. Programs
0604  * scraping this file for info should test the labels to ensure they're
0605  * getting the correct field.
0606  */
0607 static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
0608 {
0609     struct nfsd_net *nn = m->private;
0610 
0611     seq_printf(m, "max entries:           %u\n", nn->max_drc_entries);
0612     seq_printf(m, "num entries:           %u\n",
0613            atomic_read(&nn->num_drc_entries));
0614     seq_printf(m, "hash buckets:          %u\n", 1 << nn->maskbits);
0615     seq_printf(m, "mem usage:             %lld\n",
0616            percpu_counter_sum_positive(&nn->counter[NFSD_NET_DRC_MEM_USAGE]));
0617     seq_printf(m, "cache hits:            %lld\n",
0618            percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_HITS]));
0619     seq_printf(m, "cache misses:          %lld\n",
0620            percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_MISSES]));
0621     seq_printf(m, "not cached:            %lld\n",
0622            percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_NOCACHE]));
0623     seq_printf(m, "payload misses:        %lld\n",
0624            percpu_counter_sum_positive(&nn->counter[NFSD_NET_PAYLOAD_MISSES]));
0625     seq_printf(m, "longest chain len:     %u\n", nn->longest_chain);
0626     seq_printf(m, "cachesize at longest:  %u\n", nn->longest_chain_cachesize);
0627     return 0;
0628 }
0629 
0630 int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file)
0631 {
0632     struct nfsd_net *nn = net_generic(file_inode(file)->i_sb->s_fs_info,
0633                                 nfsd_net_id);
0634 
0635     return single_open(file, nfsd_reply_cache_stats_show, nn);
0636 }
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