// 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 <[email protected]>
*/
#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(nfsd_cacherep, 0);
return drc_slab ? 0: -ENOMEM;
}
void nfsd_drc_slab_free(void)
{
kmem_cache_destroy(drc_slab);
}
int nfsd_reply_cache_init(struct nfsd_net *nn)
{
unsigned int hashsize;
unsigned int i;
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->drc_hashtbl = kvzalloc(array_size(hashsize,
sizeof(*nn->drc_hashtbl)), GFP_KERNEL);
if (!nn->drc_hashtbl)
return -ENOMEM;
nn->nfsd_reply_cache_shrinker = shrinker_alloc(0, "nfsd-reply:%s",
nn->nfsd_name);
if (!nn->nfsd_reply_cache_shrinker)
goto out_shrinker;
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;
nn->nfsd_reply_cache_shrinker->private_data = nn;
shrinker_register(nn->nfsd_reply_cache_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:
kvfree(nn->drc_hashtbl);
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;
shrinker_free(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 = shrink->private_data;
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 = shrink->private_data;
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;
}
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 = net_generic(SVC_NET(rqstp), nfsd_net_id);
struct nfsd_cacherep *rp, *found;
__wsum csum;
struct nfsd_drc_bucket *b;
int type = rqstp->rq_cachetype;
LIST_HEAD(dispose);
int rtn = RC_DOIT;
if (type == RC_NOCACHE) {
nfsd_stats_rc_nocache_inc(nn);
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.
*/
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);
nfsd_cacherep_dispose(&dispose);
nfsd_stats_rc_misses_inc(nn);
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(nn);
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_STATS_DRC_MEM_USAGE]));
seq_printf(m, "cache hits: %lld\n",
percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_HITS]));
seq_printf(m, "cache misses: %lld\n",
percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_MISSES]));
seq_printf(m, "not cached: %lld\n",
percpu_counter_sum_positive(&nn->counter[NFSD_STATS_RC_NOCACHE]));
seq_printf(m, "payload misses: %lld\n",
percpu_counter_sum_positive(&nn->counter[NFSD_STATS_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;
}
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