original development tree for Linux kernel GTP module; now long in mainline.
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/*
* 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/clnt.h>
#include <linux/highmem.h>
#include "nfsd.h"
#include "cache.h"
#define NFSDDBG_FACILITY NFSDDBG_REPCACHE
#define HASHSIZE 64
static struct hlist_head * cache_hash;
static struct list_head lru_head;
static struct kmem_cache *drc_slab;
static unsigned int num_drc_entries;
static unsigned int max_drc_entries;
/*
* Calculate the hash index from an XID.
*/
static inline u32 request_hash(u32 xid)
{
u32 h = xid;
h ^= (xid >> 24);
return h & (HASHSIZE-1);
}
static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
/*
* 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 DEFINE_SPINLOCK(cache_lock);
/*
* 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);
}
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);
INIT_HLIST_NODE(&rp->c_hash);
}
return rp;
}
static void
nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
{
if (rp->c_type == RC_REPLBUFF)
kfree(rp->c_replvec.iov_base);
hlist_del(&rp->c_hash);
list_del(&rp->c_lru);
--num_drc_entries;
kmem_cache_free(drc_slab, rp);
}
int nfsd_reply_cache_init(void)
{
drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
0, 0, NULL);
if (!drc_slab)
goto out_nomem;
cache_hash = kcalloc(HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
if (!cache_hash)
goto out_nomem;
INIT_LIST_HEAD(&lru_head);
max_drc_entries = nfsd_cache_size_limit();
num_drc_entries = 0;
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;
while (!list_empty(&lru_head)) {
rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
nfsd_reply_cache_free_locked(rp);
}
kfree (cache_hash);
cache_hash = NULL;
if (drc_slab) {
kmem_cache_destroy(drc_slab);
drc_slab = NULL;
}
}
/*
* Move cache entry to end of LRU list
*/
static void
lru_put_end(struct svc_cacherep *rp)
{
rp->c_timestamp = jiffies;
list_move_tail(&rp->c_lru, &lru_head);
}
/*
* Move a cache entry from one hash list to another
*/
static void
hash_refile(struct svc_cacherep *rp)
{
hlist_del_init(&rp->c_hash);
hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid));
}
static inline bool
nfsd_cache_entry_expired(struct svc_cacherep *rp)
{
return rp->c_state != RC_INPROG &&
time_after(jiffies, rp->c_timestamp + RC_EXPIRE);
}
/*
* 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 svc_rqst *rqstp)
{
struct svc_cacherep *rp;
struct hlist_node *hn;
struct hlist_head *rh;
__be32 xid = rqstp->rq_xid;
u32 proto = rqstp->rq_prot,
vers = rqstp->rq_vers,
proc = rqstp->rq_proc;
rh = &cache_hash[request_hash(xid)];
hlist_for_each_entry(rp, hn, rh, c_hash) {
if (rp->c_state != RC_UNUSED &&
xid == rp->c_xid && proc == rp->c_proc &&
proto == rp->c_prot && vers == rp->c_vers &&
!nfsd_cache_entry_expired(rp) &&
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 rp;
}
return NULL;
}
/*
* Try to find an entry matching the current call in the cache. When none
* is found, we grab the oldest unlocked entry off the LRU list.
* Note that no operation within the loop may sleep.
*/
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;
unsigned long age;
int type = rqstp->rq_cachetype;
int rtn;
rqstp->rq_cacherep = NULL;
if (type == RC_NOCACHE) {
nfsdstats.rcnocache++;
return RC_DOIT;
}
spin_lock(&cache_lock);
rtn = RC_DOIT;
rp = nfsd_cache_search(rqstp);
if (rp)
goto found_entry;
/* Try to use the first entry on the LRU */
if (!list_empty(&lru_head)) {
rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
if (nfsd_cache_entry_expired(rp) ||
num_drc_entries >= max_drc_entries)
goto setup_entry;
}
spin_unlock(&cache_lock);
rp = nfsd_reply_cache_alloc();
if (!rp) {
dprintk("nfsd: unable to allocate DRC entry!\n");
return RC_DOIT;
}
spin_lock(&cache_lock);
++num_drc_entries;
/*
* Must search again just in case someone inserted one
* after we dropped the lock above.
*/
found = nfsd_cache_search(rqstp);
if (found) {
nfsd_reply_cache_free_locked(rp);
rp = found;
goto found_entry;
}
/*
* We're keeping the one we just allocated. Are we now over the
* limit? Prune one off the tip of the LRU in trade for the one we
* just allocated if so.
*/
if (num_drc_entries >= max_drc_entries)
nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
struct svc_cacherep, c_lru));
setup_entry:
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;
hash_refile(rp);
lru_put_end(rp);
/* release any buffer */
if (rp->c_type == RC_REPLBUFF) {
kfree(rp->c_replvec.iov_base);
rp->c_replvec.iov_base = NULL;
}
rp->c_type = RC_NOCACHE;
out:
spin_unlock(&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(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 (!rqstp->rq_secure && 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;
int len;
if (!rp)
return;
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)) {
rp->c_state = RC_UNUSED;
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;
cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
if (!cachv->iov_base) {
rp->c_state = RC_UNUSED;
return;
}
cachv->iov_len = len << 2;
memcpy(cachv->iov_base, statp, len << 2);
break;
}
spin_lock(&cache_lock);
lru_put_end(rp);
rp->c_secure = rqstp->rq_secure;
rp->c_type = cachetype;
rp->c_state = RC_DONE;
spin_unlock(&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;
}