diff options
Diffstat (limited to 'fs/nfsd/nfscache.c')
| -rw-r--r-- | fs/nfsd/nfscache.c | 614 |
1 files changed, 614 insertions, 0 deletions
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c new file mode 100644 index 000000000..dbdeb9d6a --- /dev/null +++ b/fs/nfsd/nfscache.c @@ -0,0 +1,614 @@ +// 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 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(void) +{ + struct svc_cacherep *rp; + + rp = kmem_cache_alloc(drc_slab, GFP_KERNEL); + if (rp) { + rp->c_state = RC_UNUSED; + rp->c_type = RC_NOCACHE; + INIT_LIST_HEAD(&rp->c_lru); + } + return rp; +} + +static void +nfsd_reply_cache_free_locked(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); + } + 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(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(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(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 bool +nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp) +{ + /* Check RPC XID first */ + if (rqstp->rq_xid != rp->c_xid) + return false; + /* compare checksum of NFS data */ + if (csum != rp->c_csum) { + ++payload_misses; + return false; + } + + /* Other discriminators */ + if (rqstp->rq_proc != rp->c_proc || + rqstp->rq_prot != rp->c_prot || + rqstp->rq_vers != rp->c_vers || + rqstp->rq_arg.len != rp->c_len || + !rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) || + rpc_get_port(svc_addr(rqstp)) != rpc_get_port((struct sockaddr *)&rp->c_addr)) + return false; + + return true; +} + +/* + * Search the request hash for an entry that matches the given rqstp. + * Must be called with cache_lock held. Returns the found entry or + * NULL on failure. + */ +static struct svc_cacherep * +nfsd_cache_search(struct nfsd_drc_bucket *b, struct svc_rqst *rqstp, + __wsum csum) +{ + struct svc_cacherep *rp, *ret = NULL; + struct list_head *rh = &b->lru_head; + unsigned int entries = 0; + + list_for_each_entry(rp, rh, c_lru) { + ++entries; + if (nfsd_cache_match(rqstp, csum, rp)) { + ret = rp; + break; + } + } + + /* 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)); + } + + 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; + u32 proto = rqstp->rq_prot, + vers = rqstp->rq_vers, + proc = rqstp->rq_proc; + __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(); + spin_lock(&b->cache_lock); + if (likely(rp)) { + atomic_inc(&num_drc_entries); + drc_mem_usage += sizeof(*rp); + } + + /* go ahead and prune the cache */ + prune_bucket(b); + + found = nfsd_cache_search(b, rqstp, csum); + if (found) { + if (likely(rp)) + nfsd_reply_cache_free_locked(rp); + rp = found; + goto found_entry; + } + + if (!rp) { + dprintk("nfsd: unable to allocate DRC entry!\n"); + goto out; + } + + nfsdstats.rcmisses++; + rqstp->rq_cacherep = rp; + rp->c_state = RC_INPROG; + rp->c_xid = xid; + rp->c_proc = proc; + rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp)); + rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp))); + rp->c_prot = proto; + rp->c_vers = vers; + rp->c_len = rqstp->rq_arg.len; + rp->c_csum = csum; + + lru_put_end(b, rp); + + /* release any buffer */ + if (rp->c_type == RC_REPLBUFF) { + drc_mem_usage -= rp->c_replvec.iov_len; + kfree(rp->c_replvec.iov_base); + rp->c_replvec.iov_base = NULL; + } + rp->c_type = RC_NOCACHE; + out: + spin_unlock(&b->cache_lock); + return rtn; + +found_entry: + nfsdstats.rchits++; + /* We found a matching entry which is either in progress or done. */ + lru_put_end(b, rp); + + 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(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_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); +} |