Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 652 insertions, 0 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
new file mode 100644
index 000000000..f53335ae0
--- /dev/null
+++ b/fs/nfsd/nfscache.c
@@ -0,0 +1,652 @@
+// 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 svc_cacherep *
+nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum,
+			struct nfsd_net *nn)
+{
+	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,
+				struct nfsd_net *nn)
+{
+	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
+		nfsd_stats_drc_mem_usage_sub(nn, 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(&nn->num_drc_entries);
+		nfsd_stats_drc_mem_usage_sub(nn, sizeof(*rp));
+	}
+	kmem_cache_free(drc_slab, rp);
+}
+
+static void
+nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
+			struct nfsd_net *nn)
+{
+	spin_lock(&b->cache_lock);
+	nfsd_reply_cache_free_locked(b, rp, nn);
+	spin_unlock(&b->cache_lock);
+}
+
+int nfsd_drc_slab_create(void)
+{
+	drc_slab = kmem_cache_create("nfsd_drc",
+				sizeof(struct svc_cacherep), 0, 0, NULL);
+	return drc_slab ? 0: -ENOMEM;
+}
+
+void nfsd_drc_slab_free(void)
+{
+	kmem_cache_destroy(drc_slab);
+}
+
+static int nfsd_reply_cache_stats_init(struct nfsd_net *nn)
+{
+	return nfsd_percpu_counters_init(nn->counter, NFSD_NET_COUNTERS_NUM);
+}
+
+static void nfsd_reply_cache_stats_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);
+
+	status = nfsd_reply_cache_stats_init(nn);
+	if (status)
+		goto out_nomem;
+
+	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)
+		goto out_stats_destroy;
+
+	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);
+out_stats_destroy:
+	nfsd_reply_cache_stats_destroy(nn);
+out_nomem:
+	printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
+	return -ENOMEM;
+}
+
+void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
+{
+	struct svc_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 svc_cacherep, c_lru);
+			nfsd_reply_cache_free_locked(&nn->drc_hashtbl[i],
+									rp, nn);
+		}
+	}
+	nfsd_reply_cache_stats_destroy(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 svc_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];
+}
+
+static long prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn,
+			 unsigned int max)
+{
+	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(&nn->num_drc_entries) <= nn->max_drc_entries &&
+		    time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
+			break;
+		nfsd_reply_cache_free_locked(b, rp, nn);
+		if (max && freed++ > max)
+			break;
+	}
+	return freed;
+}
+
+static long nfsd_prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn)
+{
+	return prune_bucket(b, nn, 3);
+}
+
+/*
+ * 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(struct nfsd_net *nn)
+{
+	unsigned int i;
+	long freed = 0;
+
+	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);
+		freed += prune_bucket(b, nn, 0);
+		spin_unlock(&b->cache_lock);
+	}
+	return freed;
+}
+
+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);
+}
+
+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);
+
+	return prune_cache_entries(nn);
+}
+
+/**
+ * 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 svc_cacherep *key,
+			const struct svc_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 svc_cacherep *
+nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key,
+			struct nfsd_net *nn)
+{
+	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, 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
+ *
+ * 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_net		*nn;
+	struct svc_cacherep	*rp, *found;
+	__wsum			csum;
+	struct nfsd_drc_bucket	*b;
+	int type = rqstp->rq_cachetype;
+	int rtn = RC_DOIT;
+
+	rqstp->rq_cacherep = NULL;
+	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_reply_cache_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;
+
+	nfsd_stats_rc_misses_inc();
+	rqstp->rq_cacherep = rp;
+	rp->c_state = RC_INPROG;
+
+	atomic_inc(&nn->num_drc_entries);
+	nfsd_stats_drc_mem_usage_add(nn, sizeof(*rp));
+
+	nfsd_prune_bucket(b, nn);
+
+out_unlock:
+	spin_unlock(&b->cache_lock);
+out:
+	return rtn;
+
+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:
+		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_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);
+	goto out_unlock;
+}
+
+/**
+ * nfsd_cache_update - Update an entry in the duplicate reply cache.
+ * @rqstp: svc_rqst with a finished Reply
+ * @cachetype: which cache to update
+ * @statp: Reply's status code
+ *
+ * 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 nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
+	struct svc_cacherep *rp = rqstp->rq_cacherep;
+	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;
+}
+
+/*
+ * 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.
+ */
+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;
+}