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/*
* linux/fs/nfsd/nfscache.c
*
* 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/kernel.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sunrpc/svc.h>
#include <linux/nfsd/nfsd.h>
#include <linux/nfsd/cache.h>
/* Size of reply cache. Common values are:
* 4.3BSD: 128
* 4.4BSD: 256
* Solaris2: 1024
* DEC Unix: 512-4096
*/
#define CACHESIZE 1024
#define HASHSIZE 64
#define REQHASH(xid) ((((xid) >> 24) ^ (xid)) & (HASHSIZE-1))
struct nfscache_head {
struct svc_cacherep * next;
struct svc_cacherep * prev;
};
static struct nfscache_head * hash_list;
static struct svc_cacherep * lru_head;
static struct svc_cacherep * lru_tail;
static struct svc_cacherep * nfscache;
static int cache_initialized;
static int cache_disabled = 1;
static int nfsd_cache_append(struct svc_rqst *rqstp, struct svc_buf *data);
void
nfsd_cache_init(void)
{
struct svc_cacherep *rp;
struct nfscache_head *rh;
size_t i;
unsigned long order;
if (cache_initialized)
return;
i = CACHESIZE * sizeof (struct svc_cacherep);
for (order = 0; (PAGE_SIZE << order) < i; order++)
;
nfscache = (struct svc_cacherep *)
__get_free_pages(GFP_KERNEL, order);
if (!nfscache) {
printk (KERN_ERR "nfsd: cannot allocate %Zd bytes for reply cache\n", i);
return;
}
memset(nfscache, 0, i);
i = HASHSIZE * sizeof (struct nfscache_head);
hash_list = kmalloc (i, GFP_KERNEL);
if (!hash_list) {
free_pages ((unsigned long)nfscache, order);
nfscache = NULL;
printk (KERN_ERR "nfsd: cannot allocate %Zd bytes for hash list\n", i);
return;
}
for (i = 0, rh = hash_list; i < HASHSIZE; i++, rh++)
rh->next = rh->prev = (struct svc_cacherep *) rh;
for (i = 0, rp = nfscache; i < CACHESIZE; i++, rp++) {
rp->c_state = RC_UNUSED;
rp->c_type = RC_NOCACHE;
rp->c_hash_next =
rp->c_hash_prev = rp;
rp->c_lru_next = rp + 1;
rp->c_lru_prev = rp - 1;
}
lru_head = nfscache;
lru_tail = nfscache + CACHESIZE - 1;
lru_head->c_lru_prev = NULL;
lru_tail->c_lru_next = NULL;
cache_initialized = 1;
cache_disabled = 0;
}
void
nfsd_cache_shutdown(void)
{
struct svc_cacherep *rp;
size_t i;
unsigned long order;
if (!cache_initialized)
return;
for (rp = lru_head; rp; rp = rp->c_lru_next) {
if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
kfree(rp->c_replbuf.buf);
}
cache_initialized = 0;
cache_disabled = 1;
i = CACHESIZE * sizeof (struct svc_cacherep);
for (order = 0; (PAGE_SIZE << order) < i; order++)
;
free_pages ((unsigned long)nfscache, order);
nfscache = NULL;
kfree (hash_list);
hash_list = NULL;
}
/*
* Move cache entry to front of LRU list
*/
static void
lru_put_front(struct svc_cacherep *rp)
{
struct svc_cacherep *prev = rp->c_lru_prev,
*next = rp->c_lru_next;
if (prev)
prev->c_lru_next = next;
else
lru_head = next;
if (next)
next->c_lru_prev = prev;
else
lru_tail = prev;
rp->c_lru_next = lru_head;
rp->c_lru_prev = NULL;
if (lru_head)
lru_head->c_lru_prev = rp;
lru_head = rp;
}
/*
* Move a cache entry from one hash list to another
*/
static void
hash_refile(struct svc_cacherep *rp)
{
struct svc_cacherep *prev = rp->c_hash_prev,
*next = rp->c_hash_next;
struct nfscache_head *head = hash_list + REQHASH(rp->c_xid);
prev->c_hash_next = next;
next->c_hash_prev = prev;
rp->c_hash_next = head->next;
rp->c_hash_prev = (struct svc_cacherep *) head;
head->next->c_hash_prev = rp;
head->next = rp;
}
/*
* 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, int type)
{
struct svc_cacherep *rh, *rp;
u32 xid = rqstp->rq_xid,
proto = rqstp->rq_prot,
vers = rqstp->rq_vers,
proc = rqstp->rq_proc;
unsigned long age;
rqstp->rq_cacherep = NULL;
if (cache_disabled || type == RC_NOCACHE) {
nfsdstats.rcnocache++;
return RC_DOIT;
}
rp = rh = (struct svc_cacherep *) &hash_list[REQHASH(xid)];
while ((rp = rp->c_hash_next) != rh) {
if (rp->c_state != RC_UNUSED &&
xid == rp->c_xid && proc == rp->c_proc &&
proto == rp->c_prot && vers == rp->c_vers &&
time_before(jiffies, rp->c_timestamp + 120*HZ) &&
memcmp((char*)&rqstp->rq_addr, (char*)&rp->c_addr, sizeof(rp->c_addr))==0) {
nfsdstats.rchits++;
goto found_entry;
}
}
nfsdstats.rcmisses++;
/* This loop shouldn't take more than a few iterations normally */
{
int safe = 0;
for (rp = lru_tail; rp; rp = rp->c_lru_prev) {
if (rp->c_state != RC_INPROG)
break;
if (safe++ > CACHESIZE) {
printk("nfsd: loop in repcache LRU list\n");
cache_disabled = 1;
return RC_DOIT;
}
}
}
/* This should not happen */
if (rp == NULL) {
static int complaints;
printk(KERN_WARNING "nfsd: all repcache entries locked!\n");
if (++complaints > 5) {
printk(KERN_WARNING "nfsd: disabling repcache.\n");
cache_disabled = 1;
}
return RC_DOIT;
}
rqstp->rq_cacherep = rp;
rp->c_state = RC_INPROG;
rp->c_xid = xid;
rp->c_proc = proc;
rp->c_addr = rqstp->rq_addr;
rp->c_prot = proto;
rp->c_vers = vers;
rp->c_timestamp = jiffies;
hash_refile(rp);
/* release any buffer */
if (rp->c_type == RC_REPLBUFF) {
kfree(rp->c_replbuf.buf);
rp->c_replbuf.buf = NULL;
}
rp->c_type = RC_NOCACHE;
return RC_DOIT;
found_entry:
/* We found a matching entry which is either in progress or done. */
age = jiffies - rp->c_timestamp;
rp->c_timestamp = jiffies;
lru_put_front(rp);
/* Request being processed or excessive rexmits */
if (rp->c_state == RC_INPROG || age < RC_DELAY)
return RC_DROPIT;
/* From the hall of fame of impractical attacks:
* Is this a user who tries to snoop on the cache? */
if (!rqstp->rq_secure && rp->c_secure)
return RC_DOIT;
/* Compose RPC reply header */
switch (rp->c_type) {
case RC_NOCACHE:
return RC_DOIT;
case RC_REPLSTAT:
svc_putlong(&rqstp->rq_resbuf, rp->c_replstat);
break;
case RC_REPLBUFF:
if (!nfsd_cache_append(rqstp, &rp->c_replbuf))
return RC_DOIT; /* should not happen */
break;
default:
printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
rp->c_state = RC_UNUSED;
return RC_DOIT;
}
return RC_REPLY;
}
/*
* 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, u32 *statp)
{
struct svc_cacherep *rp;
struct svc_buf *resp = &rqstp->rq_resbuf, *cachp;
int len;
if (!(rp = rqstp->rq_cacherep) || cache_disabled)
return;
len = resp->len - (statp - resp->base);
/* 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:
cachp = &rp->c_replbuf;
cachp->buf = (u32 *) kmalloc(len << 2, GFP_KERNEL);
if (!cachp->buf) {
rp->c_state = RC_UNUSED;
return;
}
cachp->len = len;
memcpy(cachp->buf, statp, len << 2);
break;
}
lru_put_front(rp);
rp->c_secure = rqstp->rq_secure;
rp->c_type = cachetype;
rp->c_state = RC_DONE;
rp->c_timestamp = jiffies;
return;
}
/*
* Copy cached reply to current reply buffer. Should always fit.
*/
static int
nfsd_cache_append(struct svc_rqst *rqstp, struct svc_buf *data)
{
struct svc_buf *resp = &rqstp->rq_resbuf;
if (resp->len + data->len > resp->buflen) {
printk(KERN_WARNING "nfsd: cached reply too large (%d).\n",
data->len);
return 0;
}
memcpy(resp->buf, data->buf, data->len << 2);
resp->buf += data->len;
resp->len += data->len;
return 1;
}
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