diff options
Diffstat (limited to '')
-rw-r--r-- | fs/nfsd/nfscache.c | 705 |
1 files changed, 705 insertions, 0 deletions
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c new file mode 100644 index 0000000000..6cd36af2f9 --- /dev/null +++ b/fs/nfsd/nfscache.c @@ -0,0 +1,705 @@ +// 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/sunrpc/svc_xprt.h> +#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" +#include "trace.h" + +/* + * 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 kmem_cache *drc_slab; + +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); + +/* + * 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. + * + * XXX: these limits are per-container, so memory used will increase + * linearly with number of containers. Maybe that's OK. + */ +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 struct nfsd_cacherep * +nfsd_cacherep_alloc(struct svc_rqst *rqstp, __wsum csum, + struct nfsd_net *nn) +{ + struct nfsd_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_cacherep_free(struct nfsd_cacherep *rp) +{ + if (rp->c_type == RC_REPLBUFF) + kfree(rp->c_replvec.iov_base); + kmem_cache_free(drc_slab, rp); +} + +static unsigned long +nfsd_cacherep_dispose(struct list_head *dispose) +{ + struct nfsd_cacherep *rp; + unsigned long freed = 0; + + while (!list_empty(dispose)) { + rp = list_first_entry(dispose, struct nfsd_cacherep, c_lru); + list_del(&rp->c_lru); + nfsd_cacherep_free(rp); + freed++; + } + return freed; +} + +static void +nfsd_cacherep_unlink_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b, + struct nfsd_cacherep *rp) +{ + if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) + nfsd_stats_drc_mem_usage_sub(nn, rp->c_replvec.iov_len); + if (rp->c_state != RC_UNUSED) { + rb_erase(&rp->c_node, &b->rb_head); + list_del(&rp->c_lru); + atomic_dec(&nn->num_drc_entries); + nfsd_stats_drc_mem_usage_sub(nn, sizeof(*rp)); + } +} + +static void +nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct nfsd_cacherep *rp, + struct nfsd_net *nn) +{ + nfsd_cacherep_unlink_locked(nn, b, rp); + nfsd_cacherep_free(rp); +} + +static void +nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct nfsd_cacherep *rp, + struct nfsd_net *nn) +{ + spin_lock(&b->cache_lock); + nfsd_cacherep_unlink_locked(nn, b, rp); + spin_unlock(&b->cache_lock); + nfsd_cacherep_free(rp); +} + +int nfsd_drc_slab_create(void) +{ + drc_slab = kmem_cache_create("nfsd_drc", + sizeof(struct nfsd_cacherep), 0, 0, NULL); + return drc_slab ? 0: -ENOMEM; +} + +void nfsd_drc_slab_free(void) +{ + kmem_cache_destroy(drc_slab); +} + +/** + * nfsd_net_reply_cache_init - per net namespace reply cache set-up + * @nn: nfsd_net being initialized + * + * Returns zero on succes; otherwise a negative errno is returned. + */ +int nfsd_net_reply_cache_init(struct nfsd_net *nn) +{ + return nfsd_percpu_counters_init(nn->counter, NFSD_NET_COUNTERS_NUM); +} + +/** + * nfsd_net_reply_cache_destroy - per net namespace reply cache tear-down + * @nn: nfsd_net being freed + * + */ +void nfsd_net_reply_cache_destroy(struct nfsd_net *nn) +{ + nfsd_percpu_counters_destroy(nn->counter, NFSD_NET_COUNTERS_NUM); +} + +int nfsd_reply_cache_init(struct nfsd_net *nn) +{ + unsigned int hashsize; + unsigned int i; + int status = 0; + + nn->max_drc_entries = nfsd_cache_size_limit(); + atomic_set(&nn->num_drc_entries, 0); + hashsize = nfsd_hashsize(nn->max_drc_entries); + nn->maskbits = ilog2(hashsize); + + nn->nfsd_reply_cache_shrinker.scan_objects = nfsd_reply_cache_scan; + nn->nfsd_reply_cache_shrinker.count_objects = nfsd_reply_cache_count; + nn->nfsd_reply_cache_shrinker.seeks = 1; + status = register_shrinker(&nn->nfsd_reply_cache_shrinker, + "nfsd-reply:%s", nn->nfsd_name); + if (status) + return status; + + nn->drc_hashtbl = kvzalloc(array_size(hashsize, + sizeof(*nn->drc_hashtbl)), GFP_KERNEL); + if (!nn->drc_hashtbl) + goto out_shrinker; + + for (i = 0; i < hashsize; i++) { + INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head); + spin_lock_init(&nn->drc_hashtbl[i].cache_lock); + } + nn->drc_hashsize = hashsize; + + return 0; +out_shrinker: + unregister_shrinker(&nn->nfsd_reply_cache_shrinker); + printk(KERN_ERR "nfsd: failed to allocate reply cache\n"); + return -ENOMEM; +} + +void nfsd_reply_cache_shutdown(struct nfsd_net *nn) +{ + struct nfsd_cacherep *rp; + unsigned int i; + + unregister_shrinker(&nn->nfsd_reply_cache_shrinker); + + for (i = 0; i < nn->drc_hashsize; i++) { + struct list_head *head = &nn->drc_hashtbl[i].lru_head; + while (!list_empty(head)) { + rp = list_first_entry(head, struct nfsd_cacherep, c_lru); + nfsd_reply_cache_free_locked(&nn->drc_hashtbl[i], + rp, nn); + } + } + + kvfree(nn->drc_hashtbl); + nn->drc_hashtbl = NULL; + nn->drc_hashsize = 0; + +} + +/* + * 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 nfsd_cacherep *rp) +{ + rp->c_timestamp = jiffies; + list_move_tail(&rp->c_lru, &b->lru_head); +} + +static noinline struct nfsd_drc_bucket * +nfsd_cache_bucket_find(__be32 xid, struct nfsd_net *nn) +{ + unsigned int hash = hash_32((__force u32)xid, nn->maskbits); + + return &nn->drc_hashtbl[hash]; +} + +/* + * Remove and return no more than @max expired entries in bucket @b. + * If @max is zero, do not limit the number of removed entries. + */ +static void +nfsd_prune_bucket_locked(struct nfsd_net *nn, struct nfsd_drc_bucket *b, + unsigned int max, struct list_head *dispose) +{ + unsigned long expiry = jiffies - RC_EXPIRE; + struct nfsd_cacherep *rp, *tmp; + unsigned int freed = 0; + + lockdep_assert_held(&b->cache_lock); + + /* The bucket LRU is ordered oldest-first. */ + 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(&nn->num_drc_entries) <= nn->max_drc_entries && + time_before(expiry, rp->c_timestamp)) + break; + + nfsd_cacherep_unlink_locked(nn, b, rp); + list_add(&rp->c_lru, dispose); + + if (max && ++freed > max) + break; + } +} + +/** + * nfsd_reply_cache_count - count_objects method for the DRC shrinker + * @shrink: our registered shrinker context + * @sc: garbage collection parameters + * + * Returns the total number of entries in the duplicate reply cache. To + * keep things simple and quick, this is not the number of expired entries + * in the cache (ie, the number that would be removed by a call to + * nfsd_reply_cache_scan). + */ +static unsigned long +nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc) +{ + struct nfsd_net *nn = container_of(shrink, + struct nfsd_net, nfsd_reply_cache_shrinker); + + return atomic_read(&nn->num_drc_entries); +} + +/** + * nfsd_reply_cache_scan - scan_objects method for the DRC shrinker + * @shrink: our registered shrinker context + * @sc: garbage collection parameters + * + * Free expired entries on each bucket's LRU list until we've released + * nr_to_scan freed objects. Nothing will be released if the cache + * has not exceeded it's max_drc_entries limit. + * + * Returns the number of entries released by this call. + */ +static unsigned long +nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc) +{ + struct nfsd_net *nn = container_of(shrink, + struct nfsd_net, nfsd_reply_cache_shrinker); + unsigned long freed = 0; + LIST_HEAD(dispose); + unsigned int i; + + for (i = 0; i < nn->drc_hashsize; i++) { + struct nfsd_drc_bucket *b = &nn->drc_hashtbl[i]; + + if (list_empty(&b->lru_head)) + continue; + + spin_lock(&b->cache_lock); + nfsd_prune_bucket_locked(nn, b, 0, &dispose); + spin_unlock(&b->cache_lock); + + freed += nfsd_cacherep_dispose(&dispose); + if (freed > sc->nr_to_scan) + break; + } + + trace_nfsd_drc_gc(nn, freed); + return freed; +} + +/** + * nfsd_cache_csum - Checksum incoming NFS Call arguments + * @buf: buffer containing a whole RPC Call message + * @start: starting byte of the NFS Call header + * @remaining: size of the NFS Call header, in bytes + * + * Compute a weak checksum of the leading bytes of an NFS procedure + * call header to help verify that a retransmitted Call matches an + * entry in the duplicate reply cache. + * + * To avoid assumptions about how the RPC message is laid out in + * @buf and what else it might contain (eg, a GSS MIC suffix), the + * caller passes us the exact location and length of the NFS Call + * header. + * + * Returns a 32-bit checksum value, as defined in RFC 793. + */ +static __wsum nfsd_cache_csum(struct xdr_buf *buf, unsigned int start, + unsigned int remaining) +{ + unsigned int base, len; + struct xdr_buf subbuf; + __wsum csum = 0; + void *p; + int idx; + + if (remaining > RC_CSUMLEN) + remaining = RC_CSUMLEN; + if (xdr_buf_subsegment(buf, &subbuf, start, remaining)) + return csum; + + /* rq_arg.head first */ + if (subbuf.head[0].iov_len) { + len = min_t(unsigned int, subbuf.head[0].iov_len, remaining); + csum = csum_partial(subbuf.head[0].iov_base, len, csum); + remaining -= len; + } + + /* Continue into page array */ + idx = subbuf.page_base / PAGE_SIZE; + base = subbuf.page_base & ~PAGE_MASK; + while (remaining) { + p = page_address(subbuf.pages[idx]) + base; + len = min_t(unsigned int, PAGE_SIZE - base, remaining); + csum = csum_partial(p, len, csum); + remaining -= len; + base = 0; + ++idx; + } + return csum; +} + +static int +nfsd_cache_key_cmp(const struct nfsd_cacherep *key, + const struct nfsd_cacherep *rp, struct nfsd_net *nn) +{ + if (key->c_key.k_xid == rp->c_key.k_xid && + key->c_key.k_csum != rp->c_key.k_csum) { + nfsd_stats_payload_misses_inc(nn); + trace_nfsd_drc_mismatch(nn, key, rp); + } + + 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 nfsd_cacherep * +nfsd_cache_insert(struct nfsd_drc_bucket *b, struct nfsd_cacherep *key, + struct nfsd_net *nn) +{ + struct nfsd_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 nfsd_cacherep, c_node); + + cmp = nfsd_cache_key_cmp(key, rp, nn); + 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 > nn->longest_chain) { + nn->longest_chain = entries; + nn->longest_chain_cachesize = atomic_read(&nn->num_drc_entries); + } else if (entries == nn->longest_chain) { + /* prefer to keep the smallest cachesize possible here */ + nn->longest_chain_cachesize = min_t(unsigned int, + nn->longest_chain_cachesize, + atomic_read(&nn->num_drc_entries)); + } + + lru_put_end(b, ret); + return ret; +} + +/** + * nfsd_cache_lookup - Find an entry in the duplicate reply cache + * @rqstp: Incoming Call to find + * @start: starting byte in @rqstp->rq_arg of the NFS Call header + * @len: size of the NFS Call header, in bytes + * @cacherep: OUT: DRC entry for this request + * + * 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. + * + * Return values: + * %RC_DOIT: Process the request normally + * %RC_REPLY: Reply from cache + * %RC_DROPIT: Do not process the request further + */ +int nfsd_cache_lookup(struct svc_rqst *rqstp, unsigned int start, + unsigned int len, struct nfsd_cacherep **cacherep) +{ + struct nfsd_net *nn; + struct nfsd_cacherep *rp, *found; + __wsum csum; + struct nfsd_drc_bucket *b; + int type = rqstp->rq_cachetype; + unsigned long freed; + LIST_HEAD(dispose); + int rtn = RC_DOIT; + + if (type == RC_NOCACHE) { + nfsd_stats_rc_nocache_inc(); + goto out; + } + + csum = nfsd_cache_csum(&rqstp->rq_arg, start, len); + + /* + * Since the common case is a cache miss followed by an insert, + * preallocate an entry. + */ + nn = net_generic(SVC_NET(rqstp), nfsd_net_id); + rp = nfsd_cacherep_alloc(rqstp, csum, nn); + if (!rp) + goto out; + + b = nfsd_cache_bucket_find(rqstp->rq_xid, nn); + spin_lock(&b->cache_lock); + found = nfsd_cache_insert(b, rp, nn); + if (found != rp) + goto found_entry; + *cacherep = rp; + rp->c_state = RC_INPROG; + nfsd_prune_bucket_locked(nn, b, 3, &dispose); + spin_unlock(&b->cache_lock); + + freed = nfsd_cacherep_dispose(&dispose); + trace_nfsd_drc_gc(nn, freed); + + nfsd_stats_rc_misses_inc(); + atomic_inc(&nn->num_drc_entries); + nfsd_stats_drc_mem_usage_add(nn, sizeof(*rp)); + goto out; + +found_entry: + /* We found a matching entry which is either in progress or done. */ + nfsd_reply_cache_free_locked(NULL, rp, nn); + nfsd_stats_rc_hits_inc(); + rtn = RC_DROPIT; + rp = found; + + /* Request being processed */ + if (rp->c_state == RC_INPROG) + goto out_trace; + + /* 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_trace; + + /* Compose RPC reply header */ + switch (rp->c_type) { + case RC_NOCACHE: + break; + case RC_REPLSTAT: + xdr_stream_encode_be32(&rqstp->rq_res_stream, rp->c_replstat); + rtn = RC_REPLY; + break; + case RC_REPLBUFF: + if (!nfsd_cache_append(rqstp, &rp->c_replvec)) + goto out_unlock; /* should not happen */ + rtn = RC_REPLY; + break; + default: + WARN_ONCE(1, "nfsd: bad repcache type %d\n", rp->c_type); + } + +out_trace: + trace_nfsd_drc_found(nn, rqstp, rtn); +out_unlock: + spin_unlock(&b->cache_lock); +out: + return rtn; +} + +/** + * nfsd_cache_update - Update an entry in the duplicate reply cache. + * @rqstp: svc_rqst with a finished Reply + * @rp: IN: DRC entry for this request + * @cachetype: which cache to update + * @statp: pointer to Reply's NFS status code, or NULL + * + * 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, struct nfsd_cacherep *rp, + int cachetype, __be32 *statp) +{ + struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id); + struct kvec *resv = &rqstp->rq_res.head[0], *cachv; + struct nfsd_drc_bucket *b; + int len; + size_t bufsize = 0; + + if (!rp) + return; + + b = nfsd_cache_bucket_find(rp->c_key.k_xid, nn); + + 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, nn); + 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, nn); + return; + } + cachv->iov_len = bufsize; + memcpy(cachv->iov_base, statp, bufsize); + break; + case RC_NOCACHE: + nfsd_reply_cache_free(b, rp, nn); + return; + } + spin_lock(&b->cache_lock); + nfsd_stats_drc_mem_usage_add(nn, 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; +} + +static int +nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data) +{ + __be32 *p; + + p = xdr_reserve_space(&rqstp->rq_res_stream, data->iov_len); + if (unlikely(!p)) + return false; + memcpy(p, data->iov_base, data->iov_len); + xdr_commit_encode(&rqstp->rq_res_stream); + return true; +} + +/* + * 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. + */ +int nfsd_reply_cache_stats_show(struct seq_file *m, void *v) +{ + struct nfsd_net *nn = net_generic(file_inode(m->file)->i_sb->s_fs_info, + nfsd_net_id); + + seq_printf(m, "max entries: %u\n", nn->max_drc_entries); + seq_printf(m, "num entries: %u\n", + atomic_read(&nn->num_drc_entries)); + seq_printf(m, "hash buckets: %u\n", 1 << nn->maskbits); + seq_printf(m, "mem usage: %lld\n", + percpu_counter_sum_positive(&nn->counter[NFSD_NET_DRC_MEM_USAGE])); + seq_printf(m, "cache hits: %lld\n", + percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_HITS])); + seq_printf(m, "cache misses: %lld\n", + percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_MISSES])); + seq_printf(m, "not cached: %lld\n", + percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_NOCACHE])); + seq_printf(m, "payload misses: %lld\n", + percpu_counter_sum_positive(&nn->counter[NFSD_NET_PAYLOAD_MISSES])); + seq_printf(m, "longest chain len: %u\n", nn->longest_chain); + seq_printf(m, "cachesize at longest: %u\n", nn->longest_chain_cachesize); + return 0; +} |