| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Request reply cache. This is currently a global cache, but this may |
| * change in the future and be a per-client cache. |
| * |
| * This code is heavily inspired by the 44BSD implementation, although |
| * it does things a bit differently. |
| * |
| * Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de> |
| */ |
| |
| #include <linux/slab.h> |
| #include <linux/vmalloc.h> |
| #include <linux/sunrpc/addr.h> |
| #include <linux/highmem.h> |
| #include <linux/log2.h> |
| #include <linux/hash.h> |
| #include <net/checksum.h> |
| |
| #include "nfsd.h" |
| #include "cache.h" |
| |
| #define NFSDDBG_FACILITY NFSDDBG_REPCACHE |
| |
| /* |
| * We use this value to determine the number of hash buckets from the max |
| * cache size, the idea being that when the cache is at its maximum number |
| * of entries, then this should be the average number of entries per bucket. |
| */ |
| #define TARGET_BUCKET_SIZE 64 |
| |
| struct nfsd_drc_bucket { |
| struct rb_root rb_head; |
| struct list_head lru_head; |
| spinlock_t cache_lock; |
| }; |
| |
| static struct nfsd_drc_bucket *drc_hashtbl; |
| static struct kmem_cache *drc_slab; |
| |
| /* max number of entries allowed in the cache */ |
| static unsigned int max_drc_entries; |
| |
| /* number of significant bits in the hash value */ |
| static unsigned int maskbits; |
| static unsigned int drc_hashsize; |
| |
| /* |
| * Stats and other tracking of on the duplicate reply cache. All of these and |
| * the "rc" fields in nfsdstats are protected by the cache_lock |
| */ |
| |
| /* total number of entries */ |
| static atomic_t num_drc_entries; |
| |
| /* cache misses due only to checksum comparison failures */ |
| static unsigned int payload_misses; |
| |
| /* amount of memory (in bytes) currently consumed by the DRC */ |
| static unsigned int drc_mem_usage; |
| |
| /* longest hash chain seen */ |
| static unsigned int longest_chain; |
| |
| /* size of cache when we saw the longest hash chain */ |
| static unsigned int longest_chain_cachesize; |
| |
| static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec); |
| static unsigned long nfsd_reply_cache_count(struct shrinker *shrink, |
| struct shrink_control *sc); |
| static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink, |
| struct shrink_control *sc); |
| |
| static struct shrinker nfsd_reply_cache_shrinker = { |
| .scan_objects = nfsd_reply_cache_scan, |
| .count_objects = nfsd_reply_cache_count, |
| .seeks = 1, |
| }; |
| |
| /* |
| * Put a cap on the size of the DRC based on the amount of available |
| * low memory in the machine. |
| * |
| * 64MB: 8192 |
| * 128MB: 11585 |
| * 256MB: 16384 |
| * 512MB: 23170 |
| * 1GB: 32768 |
| * 2GB: 46340 |
| * 4GB: 65536 |
| * 8GB: 92681 |
| * 16GB: 131072 |
| * |
| * ...with a hard cap of 256k entries. In the worst case, each entry will be |
| * ~1k, so the above numbers should give a rough max of the amount of memory |
| * used in k. |
| */ |
| static unsigned int |
| nfsd_cache_size_limit(void) |
| { |
| unsigned int limit; |
| unsigned long low_pages = totalram_pages - totalhigh_pages; |
| |
| limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10); |
| return min_t(unsigned int, limit, 256*1024); |
| } |
| |
| /* |
| * Compute the number of hash buckets we need. Divide the max cachesize by |
| * the "target" max bucket size, and round up to next power of two. |
| */ |
| static unsigned int |
| nfsd_hashsize(unsigned int limit) |
| { |
| return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE); |
| } |
| |
| static u32 |
| nfsd_cache_hash(__be32 xid) |
| { |
| return hash_32(be32_to_cpu(xid), maskbits); |
| } |
| |
| static struct svc_cacherep * |
| nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum) |
| { |
| struct svc_cacherep *rp; |
| |
| rp = kmem_cache_alloc(drc_slab, GFP_KERNEL); |
| if (rp) { |
| rp->c_state = RC_UNUSED; |
| rp->c_type = RC_NOCACHE; |
| RB_CLEAR_NODE(&rp->c_node); |
| INIT_LIST_HEAD(&rp->c_lru); |
| |
| memset(&rp->c_key, 0, sizeof(rp->c_key)); |
| rp->c_key.k_xid = rqstp->rq_xid; |
| rp->c_key.k_proc = rqstp->rq_proc; |
| rpc_copy_addr((struct sockaddr *)&rp->c_key.k_addr, svc_addr(rqstp)); |
| rpc_set_port((struct sockaddr *)&rp->c_key.k_addr, rpc_get_port(svc_addr(rqstp))); |
| rp->c_key.k_prot = rqstp->rq_prot; |
| rp->c_key.k_vers = rqstp->rq_vers; |
| rp->c_key.k_len = rqstp->rq_arg.len; |
| rp->c_key.k_csum = csum; |
| } |
| return rp; |
| } |
| |
| static void |
| nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) |
| { |
| if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) { |
| drc_mem_usage -= rp->c_replvec.iov_len; |
| kfree(rp->c_replvec.iov_base); |
| } |
| if (rp->c_state != RC_UNUSED) { |
| rb_erase(&rp->c_node, &b->rb_head); |
| list_del(&rp->c_lru); |
| atomic_dec(&num_drc_entries); |
| drc_mem_usage -= sizeof(*rp); |
| } |
| kmem_cache_free(drc_slab, rp); |
| } |
| |
| static void |
| nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) |
| { |
| spin_lock(&b->cache_lock); |
| nfsd_reply_cache_free_locked(b, rp); |
| spin_unlock(&b->cache_lock); |
| } |
| |
| int nfsd_reply_cache_init(void) |
| { |
| unsigned int hashsize; |
| unsigned int i; |
| int status = 0; |
| |
| max_drc_entries = nfsd_cache_size_limit(); |
| atomic_set(&num_drc_entries, 0); |
| hashsize = nfsd_hashsize(max_drc_entries); |
| maskbits = ilog2(hashsize); |
| |
| status = register_shrinker(&nfsd_reply_cache_shrinker); |
| if (status) |
| return status; |
| |
| drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep), |
| 0, 0, NULL); |
| if (!drc_slab) |
| goto out_nomem; |
| |
| drc_hashtbl = kcalloc(hashsize, sizeof(*drc_hashtbl), GFP_KERNEL); |
| if (!drc_hashtbl) { |
| drc_hashtbl = vzalloc(array_size(hashsize, |
| sizeof(*drc_hashtbl))); |
| if (!drc_hashtbl) |
| goto out_nomem; |
| } |
| |
| for (i = 0; i < hashsize; i++) { |
| INIT_LIST_HEAD(&drc_hashtbl[i].lru_head); |
| spin_lock_init(&drc_hashtbl[i].cache_lock); |
| } |
| drc_hashsize = hashsize; |
| |
| return 0; |
| out_nomem: |
| printk(KERN_ERR "nfsd: failed to allocate reply cache\n"); |
| nfsd_reply_cache_shutdown(); |
| return -ENOMEM; |
| } |
| |
| void nfsd_reply_cache_shutdown(void) |
| { |
| struct svc_cacherep *rp; |
| unsigned int i; |
| |
| unregister_shrinker(&nfsd_reply_cache_shrinker); |
| |
| for (i = 0; i < drc_hashsize; i++) { |
| struct list_head *head = &drc_hashtbl[i].lru_head; |
| while (!list_empty(head)) { |
| rp = list_first_entry(head, struct svc_cacherep, c_lru); |
| nfsd_reply_cache_free_locked(&drc_hashtbl[i], rp); |
| } |
| } |
| |
| kvfree(drc_hashtbl); |
| drc_hashtbl = NULL; |
| drc_hashsize = 0; |
| |
| kmem_cache_destroy(drc_slab); |
| drc_slab = NULL; |
| } |
| |
| /* |
| * Move cache entry to end of LRU list, and queue the cleaner to run if it's |
| * not already scheduled. |
| */ |
| static void |
| lru_put_end(struct nfsd_drc_bucket *b, struct svc_cacherep *rp) |
| { |
| rp->c_timestamp = jiffies; |
| list_move_tail(&rp->c_lru, &b->lru_head); |
| } |
| |
| static long |
| prune_bucket(struct nfsd_drc_bucket *b) |
| { |
| struct svc_cacherep *rp, *tmp; |
| long freed = 0; |
| |
| list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) { |
| /* |
| * Don't free entries attached to calls that are still |
| * in-progress, but do keep scanning the list. |
| */ |
| if (rp->c_state == RC_INPROG) |
| continue; |
| if (atomic_read(&num_drc_entries) <= max_drc_entries && |
| time_before(jiffies, rp->c_timestamp + RC_EXPIRE)) |
| break; |
| nfsd_reply_cache_free_locked(b, rp); |
| freed++; |
| } |
| return freed; |
| } |
| |
| /* |
| * Walk the LRU list and prune off entries that are older than RC_EXPIRE. |
| * Also prune the oldest ones when the total exceeds the max number of entries. |
| */ |
| static long |
| prune_cache_entries(void) |
| { |
| unsigned int i; |
| long freed = 0; |
| |
| for (i = 0; i < drc_hashsize; i++) { |
| struct nfsd_drc_bucket *b = &drc_hashtbl[i]; |
| |
| if (list_empty(&b->lru_head)) |
| continue; |
| spin_lock(&b->cache_lock); |
| freed += prune_bucket(b); |
| spin_unlock(&b->cache_lock); |
| } |
| return freed; |
| } |
| |
| static unsigned long |
| nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc) |
| { |
| return atomic_read(&num_drc_entries); |
| } |
| |
| static unsigned long |
| nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc) |
| { |
| return prune_cache_entries(); |
| } |
| /* |
| * Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes |
| */ |
| static __wsum |
| nfsd_cache_csum(struct svc_rqst *rqstp) |
| { |
| int idx; |
| unsigned int base; |
| __wsum csum; |
| struct xdr_buf *buf = &rqstp->rq_arg; |
| const unsigned char *p = buf->head[0].iov_base; |
| size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len, |
| RC_CSUMLEN); |
| size_t len = min(buf->head[0].iov_len, csum_len); |
| |
| /* rq_arg.head first */ |
| csum = csum_partial(p, len, 0); |
| csum_len -= len; |
| |
| /* Continue into page array */ |
| idx = buf->page_base / PAGE_SIZE; |
| base = buf->page_base & ~PAGE_MASK; |
| while (csum_len) { |
| p = page_address(buf->pages[idx]) + base; |
| len = min_t(size_t, PAGE_SIZE - base, csum_len); |
| csum = csum_partial(p, len, csum); |
| csum_len -= len; |
| base = 0; |
| ++idx; |
| } |
| return csum; |
| } |
| |
| static int |
| nfsd_cache_key_cmp(const struct svc_cacherep *key, const struct svc_cacherep *rp) |
| { |
| if (key->c_key.k_xid == rp->c_key.k_xid && |
| key->c_key.k_csum != rp->c_key.k_csum) |
| ++payload_misses; |
| |
| return memcmp(&key->c_key, &rp->c_key, sizeof(key->c_key)); |
| } |
| |
| /* |
| * Search the request hash for an entry that matches the given rqstp. |
| * Must be called with cache_lock held. Returns the found entry or |
| * inserts an empty key on failure. |
| */ |
| static struct svc_cacherep * |
| nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key) |
| { |
| struct svc_cacherep *rp, *ret = key; |
| struct rb_node **p = &b->rb_head.rb_node, |
| *parent = NULL; |
| unsigned int entries = 0; |
| int cmp; |
| |
| while (*p != NULL) { |
| ++entries; |
| parent = *p; |
| rp = rb_entry(parent, struct svc_cacherep, c_node); |
| |
| cmp = nfsd_cache_key_cmp(key, rp); |
| if (cmp < 0) |
| p = &parent->rb_left; |
| else if (cmp > 0) |
| p = &parent->rb_right; |
| else { |
| ret = rp; |
| goto out; |
| } |
| } |
| rb_link_node(&key->c_node, parent, p); |
| rb_insert_color(&key->c_node, &b->rb_head); |
| out: |
| /* tally hash chain length stats */ |
| if (entries > longest_chain) { |
| longest_chain = entries; |
| longest_chain_cachesize = atomic_read(&num_drc_entries); |
| } else if (entries == longest_chain) { |
| /* prefer to keep the smallest cachesize possible here */ |
| longest_chain_cachesize = min_t(unsigned int, |
| longest_chain_cachesize, |
| atomic_read(&num_drc_entries)); |
| } |
| |
| lru_put_end(b, ret); |
| return ret; |
| } |
| |
| /* |
| * Try to find an entry matching the current call in the cache. When none |
| * is found, we try to grab the oldest expired entry off the LRU list. If |
| * a suitable one isn't there, then drop the cache_lock and allocate a |
| * new one, then search again in case one got inserted while this thread |
| * didn't hold the lock. |
| */ |
| int |
| nfsd_cache_lookup(struct svc_rqst *rqstp) |
| { |
| struct svc_cacherep *rp, *found; |
| __be32 xid = rqstp->rq_xid; |
| __wsum csum; |
| u32 hash = nfsd_cache_hash(xid); |
| struct nfsd_drc_bucket *b = &drc_hashtbl[hash]; |
| int type = rqstp->rq_cachetype; |
| int rtn = RC_DOIT; |
| |
| rqstp->rq_cacherep = NULL; |
| if (type == RC_NOCACHE) { |
| nfsdstats.rcnocache++; |
| return rtn; |
| } |
| |
| csum = nfsd_cache_csum(rqstp); |
| |
| /* |
| * Since the common case is a cache miss followed by an insert, |
| * preallocate an entry. |
| */ |
| rp = nfsd_reply_cache_alloc(rqstp, csum); |
| if (!rp) { |
| dprintk("nfsd: unable to allocate DRC entry!\n"); |
| return rtn; |
| } |
| |
| spin_lock(&b->cache_lock); |
| found = nfsd_cache_insert(b, rp); |
| if (found != rp) { |
| nfsd_reply_cache_free_locked(NULL, rp); |
| rp = found; |
| goto found_entry; |
| } |
| |
| nfsdstats.rcmisses++; |
| rqstp->rq_cacherep = rp; |
| rp->c_state = RC_INPROG; |
| |
| atomic_inc(&num_drc_entries); |
| drc_mem_usage += sizeof(*rp); |
| |
| /* go ahead and prune the cache */ |
| prune_bucket(b); |
| out: |
| spin_unlock(&b->cache_lock); |
| return rtn; |
| |
| found_entry: |
| /* We found a matching entry which is either in progress or done. */ |
| nfsdstats.rchits++; |
| rtn = RC_DROPIT; |
| |
| /* Request being processed */ |
| if (rp->c_state == RC_INPROG) |
| goto out; |
| |
| /* From the hall of fame of impractical attacks: |
| * Is this a user who tries to snoop on the cache? */ |
| rtn = RC_DOIT; |
| if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && rp->c_secure) |
| goto out; |
| |
| /* Compose RPC reply header */ |
| switch (rp->c_type) { |
| case RC_NOCACHE: |
| break; |
| case RC_REPLSTAT: |
| svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat); |
| rtn = RC_REPLY; |
| break; |
| case RC_REPLBUFF: |
| if (!nfsd_cache_append(rqstp, &rp->c_replvec)) |
| goto out; /* should not happen */ |
| rtn = RC_REPLY; |
| break; |
| default: |
| printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type); |
| nfsd_reply_cache_free_locked(b, rp); |
| } |
| |
| goto out; |
| } |
| |
| /* |
| * Update a cache entry. This is called from nfsd_dispatch when |
| * the procedure has been executed and the complete reply is in |
| * rqstp->rq_res. |
| * |
| * We're copying around data here rather than swapping buffers because |
| * the toplevel loop requires max-sized buffers, which would be a waste |
| * of memory for a cache with a max reply size of 100 bytes (diropokres). |
| * |
| * If we should start to use different types of cache entries tailored |
| * specifically for attrstat and fh's, we may save even more space. |
| * |
| * Also note that a cachetype of RC_NOCACHE can legally be passed when |
| * nfsd failed to encode a reply that otherwise would have been cached. |
| * In this case, nfsd_cache_update is called with statp == NULL. |
| */ |
| void |
| nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp) |
| { |
| struct svc_cacherep *rp = rqstp->rq_cacherep; |
| struct kvec *resv = &rqstp->rq_res.head[0], *cachv; |
| u32 hash; |
| struct nfsd_drc_bucket *b; |
| int len; |
| size_t bufsize = 0; |
| |
| if (!rp) |
| return; |
| |
| hash = nfsd_cache_hash(rp->c_key.k_xid); |
| b = &drc_hashtbl[hash]; |
| |
| len = resv->iov_len - ((char*)statp - (char*)resv->iov_base); |
| len >>= 2; |
| |
| /* Don't cache excessive amounts of data and XDR failures */ |
| if (!statp || len > (256 >> 2)) { |
| nfsd_reply_cache_free(b, rp); |
| return; |
| } |
| |
| switch (cachetype) { |
| case RC_REPLSTAT: |
| if (len != 1) |
| printk("nfsd: RC_REPLSTAT/reply len %d!\n",len); |
| rp->c_replstat = *statp; |
| break; |
| case RC_REPLBUFF: |
| cachv = &rp->c_replvec; |
| bufsize = len << 2; |
| cachv->iov_base = kmalloc(bufsize, GFP_KERNEL); |
| if (!cachv->iov_base) { |
| nfsd_reply_cache_free(b, rp); |
| return; |
| } |
| cachv->iov_len = bufsize; |
| memcpy(cachv->iov_base, statp, bufsize); |
| break; |
| case RC_NOCACHE: |
| nfsd_reply_cache_free(b, rp); |
| return; |
| } |
| spin_lock(&b->cache_lock); |
| drc_mem_usage += bufsize; |
| lru_put_end(b, rp); |
| rp->c_secure = test_bit(RQ_SECURE, &rqstp->rq_flags); |
| rp->c_type = cachetype; |
| rp->c_state = RC_DONE; |
| spin_unlock(&b->cache_lock); |
| return; |
| } |
| |
| /* |
| * Copy cached reply to current reply buffer. Should always fit. |
| * FIXME as reply is in a page, we should just attach the page, and |
| * keep a refcount.... |
| */ |
| static int |
| nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data) |
| { |
| struct kvec *vec = &rqstp->rq_res.head[0]; |
| |
| if (vec->iov_len + data->iov_len > PAGE_SIZE) { |
| printk(KERN_WARNING "nfsd: cached reply too large (%zd).\n", |
| data->iov_len); |
| return 0; |
| } |
| memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len); |
| vec->iov_len += data->iov_len; |
| return 1; |
| } |
| |
| /* |
| * Note that fields may be added, removed or reordered in the future. Programs |
| * scraping this file for info should test the labels to ensure they're |
| * getting the correct field. |
| */ |
| static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v) |
| { |
| seq_printf(m, "max entries: %u\n", max_drc_entries); |
| seq_printf(m, "num entries: %u\n", |
| atomic_read(&num_drc_entries)); |
| seq_printf(m, "hash buckets: %u\n", 1 << maskbits); |
| seq_printf(m, "mem usage: %u\n", drc_mem_usage); |
| seq_printf(m, "cache hits: %u\n", nfsdstats.rchits); |
| seq_printf(m, "cache misses: %u\n", nfsdstats.rcmisses); |
| seq_printf(m, "not cached: %u\n", nfsdstats.rcnocache); |
| seq_printf(m, "payload misses: %u\n", payload_misses); |
| seq_printf(m, "longest chain len: %u\n", longest_chain); |
| seq_printf(m, "cachesize at longest: %u\n", longest_chain_cachesize); |
| return 0; |
| } |
| |
| int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file) |
| { |
| return single_open(file, nfsd_reply_cache_stats_show, NULL); |
| } |