--- /dev/null
+/*
+ * 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/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 void cache_cleaner_func(struct work_struct *unused);
+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,
+};
+
+/*
+ * locking for the reply cache:
+ * A cache entry is "single use" if c_state == RC_INPROG
+ * Otherwise, it when accessing _prev or _next, the lock must be held.
+ */
+static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);
+
+/*
+ * 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)
+ 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);
+ cancel_delayed_work_sync(&cache_cleaner);
+
+ 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);
+ }
+ }
+
+ kfree (drc_hashtbl);
+ drc_hashtbl = NULL;
+ drc_hashsize = 0;
+
+ if (drc_slab) {
+ 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);
+ schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
+}
+
+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;
+ bool cancel = true;
+
+ 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);
+ if (!list_empty(&b->lru_head))
+ cancel = false;
+ spin_unlock(&b->cache_lock);
+ }
+
+ /*
+ * Conditionally rearm the job to run in RC_EXPIRE since we just
+ * ran the pruner.
+ */
+ if (!cancel)
+ mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
+ return freed;
+}
+
+static void
+cache_cleaner_func(struct work_struct *unused)
+{
+ prune_cache_entries();
+}
+
+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];
+ unsigned long age;
+ 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. */
+ age = jiffies - rp->c_timestamp;
+ lru_put_end(b, rp);
+
+ rtn = RC_DROPIT;
+ /* Request being processed or excessive rexmits */
+ if (rp->c_state == RC_INPROG || age < RC_DELAY)
+ 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);
+}
Code Review / kvmfornfv.git / blobdiff