[deliverable/linux.git] / 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/slab.h>
#include <linux/sunrpc/addr.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);
static void	cache_cleaner_func(struct work_struct *unused);
static int 	nfsd_reply_cache_shrink(struct shrinker *shrink,
					struct shrink_control *sc);

struct shrinker nfsd_reply_cache_shrinker = {
	.shrink	= nfsd_reply_cache_shrink,
	.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 DEFINE_SPINLOCK(cache_lock);
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);
}

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);
}

static void
nfsd_reply_cache_free(struct svc_cacherep *rp)
{
	spin_lock(&cache_lock);
	nfsd_reply_cache_free_locked(rp);
	spin_unlock(&cache_lock);
}

int nfsd_reply_cache_init(void)
{
	register_shrinker(&nfsd_reply_cache_shrinker);
	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;

	unregister_shrinker(&nfsd_reply_cache_shrinker);
	cancel_delayed_work_sync(&cache_cleaner);

	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, and queue the cleaner to run if it's
 * not already scheduled.
 */
static void
lru_put_end(struct svc_cacherep *rp)
{
	rp->c_timestamp = jiffies;
	list_move_tail(&rp->c_lru, &lru_head);
	schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
}

/*
 * 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);
}

/*
 * 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 void
prune_cache_entries(void)
{
	struct svc_cacherep *rp, *tmp;

	list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {
		if (!nfsd_cache_entry_expired(rp) &&
		    num_drc_entries <= max_drc_entries)
			break;
		nfsd_reply_cache_free_locked(rp);
	}

	/*
	 * Conditionally rearm the job. If we cleaned out the list, then
	 * cancel any pending run (since there won't be any work to do).
	 * Otherwise, we rearm the job or modify the existing one to run in
	 * RC_EXPIRE since we just ran the pruner.
	 */
	if (list_empty(&lru_head))
		cancel_delayed_work(&cache_cleaner);
	else
		mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
}

static void
cache_cleaner_func(struct work_struct *unused)
{
	spin_lock(&cache_lock);
	prune_cache_entries();
	spin_unlock(&cache_lock);
}

static int
nfsd_reply_cache_shrink(struct shrinker *shrink, struct shrink_control *sc)
{
	unsigned int num;

	spin_lock(&cache_lock);
	if (sc->nr_to_scan)
		prune_cache_entries();
	num = num_drc_entries;
	spin_unlock(&cache_lock);

	return num;
}

/*
 * 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 (xid == rp->c_xid && proc == rp->c_proc &&
		    proto == rp->c_prot && vers == rp->c_vers &&
		    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) {
			lru_put_end(rp);
			prune_cache_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)) {
		nfsd_reply_cache_free(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;
		cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
		if (!cachv->iov_base) {
			nfsd_reply_cache_free(rp);
			return;
		}
		cachv->iov_len = len << 2;
		memcpy(cachv->iov_base, statp, len << 2);
		break;
	case RC_NOCACHE:
		nfsd_reply_cache_free(rp);
		return;
	}
	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;
}
Commit	Line	Data
1da177e4	1	/*
1da177e4 LT	2	* Request reply cache. This is currently a global cache, but this may
	3	* change in the future and be a per-client cache.
	4	*
	5	* This code is heavily inspired by the 44BSD implementation, although
	6	* it does things a bit differently.
	7	*
	8	* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
	9	*/
	10
5a0e3ad6	11	#include <linux/slab.h>
5976687a	12	#include <linux/sunrpc/addr.h>
0338dd15	13	#include <linux/highmem.h>
5a0e3ad6	14
9a74af21 BH	15	#include "nfsd.h"
9a74af21 BH	16	#include "cache.h"
1da177e4	17
0338dd15 JL	18	#define NFSDDBG_FACILITY NFSDDBG_REPCACHE
0338dd15 JL	19
1da177e4	20	#define HASHSIZE 64
1da177e4	21
fca4217c	22	static struct hlist_head * cache_hash;
1da177e4	23	static struct list_head lru_head;
8a8bc40d	24	static struct kmem_cache *drc_slab;
0ee0bf7e	25	static unsigned int num_drc_entries;
0338dd15	26	static unsigned int max_drc_entries;
1da177e4	27
fca4217c GB	28	/*
	29	* Calculate the hash index from an XID.
	30	*/
	31	static inline u32 request_hash(u32 xid)
	32	{
	33	u32 h = xid;
	34	h ^= (xid >> 24);
	35	return h & (HASHSIZE-1);
	36	}
	37
1da177e4	38	static int nfsd_cache_append(struct svc_rqst rqstp, struct kvec vec);
aca8a23d	39	static void cache_cleaner_func(struct work_struct *unused);
b4e7f2c9 JL	40	static int nfsd_reply_cache_shrink(struct shrinker *shrink,
	41	struct shrink_control *sc);
	42
	43	struct shrinker nfsd_reply_cache_shrinker = {
	44	.shrink = nfsd_reply_cache_shrink,
	45	.seeks = 1,
	46	};
1da177e4	47
fca4217c	48	/*
1da177e4 LT	49	* locking for the reply cache:
	50	* A cache entry is "single use" if c_state == RC_INPROG
	51	* Otherwise, it when accessing _prev or _next, the lock must be held.
	52	*/
	53	static DEFINE_SPINLOCK(cache_lock);
aca8a23d	54	static DECLARE_DELAYED_WORK(cache_cleaner, cache_cleaner_func);
1da177e4	55
0338dd15 JL	56	/*
	57	* Put a cap on the size of the DRC based on the amount of available
	58	* low memory in the machine.
	59	*
	60	* 64MB: 8192
	61	* 128MB: 11585
	62	* 256MB: 16384
	63	* 512MB: 23170
	64	* 1GB: 32768
	65	* 2GB: 46340
	66	* 4GB: 65536
	67	* 8GB: 92681
	68	* 16GB: 131072
	69	*
	70	* ...with a hard cap of 256k entries. In the worst case, each entry will be
	71	* ~1k, so the above numbers should give a rough max of the amount of memory
	72	* used in k.
	73	*/
	74	static unsigned int
	75	nfsd_cache_size_limit(void)
	76	{
	77	unsigned int limit;
	78	unsigned long low_pages = totalram_pages - totalhigh_pages;
	79
	80	limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10);
	81	return min_t(unsigned int, limit, 256*1024);
	82	}
	83
f09841fd JL	84	static struct svc_cacherep *
f09841fd JL	85	nfsd_reply_cache_alloc(void)
1da177e4 LT	86	{
1da177e4 LT	87	struct svc_cacherep *rp;
f09841fd JL	88
	89	rp = kmem_cache_alloc(drc_slab, GFP_KERNEL);
	90	if (rp) {
	91	rp->c_state = RC_UNUSED;
	92	rp->c_type = RC_NOCACHE;
	93	INIT_LIST_HEAD(&rp->c_lru);
	94	INIT_HLIST_NODE(&rp->c_hash);
	95	}
	96	return rp;
	97	}
	98
	99	static void
	100	nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
	101	{
25e6b8b0	102	if (rp->c_type == RC_REPLBUFF)
f09841fd	103	kfree(rp->c_replvec.iov_base);
0338dd15	104	hlist_del(&rp->c_hash);
f09841fd	105	list_del(&rp->c_lru);
0ee0bf7e	106	--num_drc_entries;
f09841fd JL	107	kmem_cache_free(drc_slab, rp);
	108	}
	109
2c6b691c JL	110	static void
	111	nfsd_reply_cache_free(struct svc_cacherep *rp)
	112	{
	113	spin_lock(&cache_lock);
	114	nfsd_reply_cache_free_locked(rp);
	115	spin_unlock(&cache_lock);
	116	}
	117
f09841fd JL	118	int nfsd_reply_cache_init(void)
f09841fd JL	119	{
b4e7f2c9	120	register_shrinker(&nfsd_reply_cache_shrinker);
8a8bc40d JL	121	drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
	122	0, 0, NULL);
	123	if (!drc_slab)
	124	goto out_nomem;
	125
0338dd15	126	cache_hash = kcalloc(HASHSIZE, sizeof(struct hlist_head), GFP_KERNEL);
fca4217c	127	if (!cache_hash)
d5c3428b	128	goto out_nomem;
1da177e4	129
0338dd15 JL	130	INIT_LIST_HEAD(&lru_head);
	131	max_drc_entries = nfsd_cache_size_limit();
	132	num_drc_entries = 0;
d5c3428b BF	133	return 0;
	134	out_nomem:
	135	printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
	136	nfsd_reply_cache_shutdown();
	137	return -ENOMEM;
1da177e4 LT	138	}
1da177e4 LT	139
d5c3428b	140	void nfsd_reply_cache_shutdown(void)
1da177e4 LT	141	{
	142	struct svc_cacherep *rp;
	143
b4e7f2c9	144	unregister_shrinker(&nfsd_reply_cache_shrinker);
aca8a23d JL	145	cancel_delayed_work_sync(&cache_cleaner);
aca8a23d JL	146
1da177e4 LT	147	while (!list_empty(&lru_head)) {
1da177e4 LT	148	rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
f09841fd	149	nfsd_reply_cache_free_locked(rp);
1da177e4 LT	150	}
1da177e4 LT	151
fca4217c GB	152	kfree (cache_hash);
fca4217c GB	153	cache_hash = NULL;
8a8bc40d JL	154
	155	if (drc_slab) {
	156	kmem_cache_destroy(drc_slab);
	157	drc_slab = NULL;
	158	}
1da177e4 LT	159	}
	160
	161	/*
aca8a23d JL	162	* Move cache entry to end of LRU list, and queue the cleaner to run if it's
aca8a23d JL	163	* not already scheduled.
1da177e4 LT	164	*/
	165	static void
	166	lru_put_end(struct svc_cacherep *rp)
	167	{
56c2548b	168	rp->c_timestamp = jiffies;
f116629d	169	list_move_tail(&rp->c_lru, &lru_head);
aca8a23d	170	schedule_delayed_work(&cache_cleaner, RC_EXPIRE);
1da177e4 LT	171	}
	172
	173	/*
	174	* Move a cache entry from one hash list to another
	175	*/
	176	static void
	177	hash_refile(struct svc_cacherep *rp)
	178	{
	179	hlist_del_init(&rp->c_hash);
fca4217c	180	hlist_add_head(&rp->c_hash, cache_hash + request_hash(rp->c_xid));
1da177e4 LT	181	}
1da177e4 LT	182
d1a0774d JL	183	static inline bool
	184	nfsd_cache_entry_expired(struct svc_cacherep *rp)
	185	{
	186	return rp->c_state != RC_INPROG &&
	187	time_after(jiffies, rp->c_timestamp + RC_EXPIRE);
	188	}
	189
aca8a23d JL	190	/*
	191	* Walk the LRU list and prune off entries that are older than RC_EXPIRE.
	192	* Also prune the oldest ones when the total exceeds the max number of entries.
	193	*/
	194	static void
	195	prune_cache_entries(void)
	196	{
	197	struct svc_cacherep rp, tmp;
	198
	199	list_for_each_entry_safe(rp, tmp, &lru_head, c_lru) {
	200	if (!nfsd_cache_entry_expired(rp) &&
	201	num_drc_entries <= max_drc_entries)
	202	break;
	203	nfsd_reply_cache_free_locked(rp);
	204	}
	205
	206	/*
	207	* Conditionally rearm the job. If we cleaned out the list, then
	208	* cancel any pending run (since there won't be any work to do).
	209	* Otherwise, we rearm the job or modify the existing one to run in
	210	* RC_EXPIRE since we just ran the pruner.
	211	*/
	212	if (list_empty(&lru_head))
	213	cancel_delayed_work(&cache_cleaner);
	214	else
	215	mod_delayed_work(system_wq, &cache_cleaner, RC_EXPIRE);
	216	}
	217
	218	static void
	219	cache_cleaner_func(struct work_struct *unused)
	220	{
	221	spin_lock(&cache_lock);
	222	prune_cache_entries();
	223	spin_unlock(&cache_lock);
	224	}
	225
b4e7f2c9 JL	226	static int
	227	nfsd_reply_cache_shrink(struct shrinker shrink, struct shrink_control sc)
	228	{
	229	unsigned int num;
	230
	231	spin_lock(&cache_lock);
	232	if (sc->nr_to_scan)
	233	prune_cache_entries();
	234	num = num_drc_entries;
	235	spin_unlock(&cache_lock);
	236
	237	return num;
	238	}
	239
a4a3ec32 JL	240	/*
	241	* Search the request hash for an entry that matches the given rqstp.
	242	* Must be called with cache_lock held. Returns the found entry or
	243	* NULL on failure.
	244	*/
	245	static struct svc_cacherep *
	246	nfsd_cache_search(struct svc_rqst *rqstp)
	247	{
	248	struct svc_cacherep *rp;
	249	struct hlist_node *hn;
	250	struct hlist_head *rh;
	251	__be32 xid = rqstp->rq_xid;
	252	u32 proto = rqstp->rq_prot,
	253	vers = rqstp->rq_vers,
	254	proc = rqstp->rq_proc;
	255
	256	rh = &cache_hash[request_hash(xid)];
	257	hlist_for_each_entry(rp, hn, rh, c_hash) {
2c6b691c	258	if (xid == rp->c_xid && proc == rp->c_proc &&
a4a3ec32	259	proto == rp->c_prot && vers == rp->c_vers &&
a4a3ec32 JL	260	rpc_cmp_addr(svc_addr(rqstp), (struct sockaddr *)&rp->c_addr) &&
	261	rpc_get_port(svc_addr(rqstp)) == rpc_get_port((struct sockaddr *)&rp->c_addr))
	262	return rp;
	263	}
	264	return NULL;
	265	}
	266
1da177e4 LT	267	/*
	268	* Try to find an entry matching the current call in the cache. When none
	269	* is found, we grab the oldest unlocked entry off the LRU list.
	270	* Note that no operation within the loop may sleep.
	271	*/
	272	int
1091006c	273	nfsd_cache_lookup(struct svc_rqst *rqstp)
1da177e4	274	{
0338dd15	275	struct svc_cacherep rp, found;
c7afef1f AV	276	__be32 xid = rqstp->rq_xid;
c7afef1f AV	277	u32 proto = rqstp->rq_prot,
1da177e4 LT	278	vers = rqstp->rq_vers,
	279	proc = rqstp->rq_proc;
	280	unsigned long age;
1091006c	281	int type = rqstp->rq_cachetype;
1da177e4 LT	282	int rtn;
	283
	284	rqstp->rq_cacherep = NULL;
13cc8a78	285	if (type == RC_NOCACHE) {
1da177e4 LT	286	nfsdstats.rcnocache++;
	287	return RC_DOIT;
	288	}
	289
	290	spin_lock(&cache_lock);
	291	rtn = RC_DOIT;
	292
a4a3ec32	293	rp = nfsd_cache_search(rqstp);
0338dd15	294	if (rp)
a4a3ec32	295	goto found_entry;
0338dd15 JL	296
	297	/* Try to use the first entry on the LRU */
	298	if (!list_empty(&lru_head)) {
	299	rp = list_first_entry(&lru_head, struct svc_cacherep, c_lru);
	300	if (nfsd_cache_entry_expired(rp) \|\|
aca8a23d JL	301	num_drc_entries >= max_drc_entries) {
	302	lru_put_end(rp);
	303	prune_cache_entries();
0338dd15	304	goto setup_entry;
aca8a23d	305	}
1da177e4	306	}
1da177e4	307
0338dd15 JL	308	spin_unlock(&cache_lock);
	309	rp = nfsd_reply_cache_alloc();
	310	if (!rp) {
	311	dprintk("nfsd: unable to allocate DRC entry!\n");
	312	return RC_DOIT;
1da177e4	313	}
0338dd15 JL	314	spin_lock(&cache_lock);
	315	++num_drc_entries;
	316
	317	/*
	318	* Must search again just in case someone inserted one
	319	* after we dropped the lock above.
	320	*/
	321	found = nfsd_cache_search(rqstp);
	322	if (found) {
	323	nfsd_reply_cache_free_locked(rp);
	324	rp = found;
	325	goto found_entry;
1da177e4 LT	326	}
1da177e4 LT	327
0338dd15 JL	328	/*
	329	* We're keeping the one we just allocated. Are we now over the
	330	* limit? Prune one off the tip of the LRU in trade for the one we
	331	* just allocated if so.
	332	*/
	333	if (num_drc_entries >= max_drc_entries)
	334	nfsd_reply_cache_free_locked(list_first_entry(&lru_head,
	335	struct svc_cacherep, c_lru));
1da177e4	336
0338dd15 JL	337	setup_entry:
0338dd15 JL	338	nfsdstats.rcmisses++;
1da177e4 LT	339	rqstp->rq_cacherep = rp;
	340	rp->c_state = RC_INPROG;
	341	rp->c_xid = xid;
	342	rp->c_proc = proc;
7b9e8522 JL	343	rpc_copy_addr((struct sockaddr *)&rp->c_addr, svc_addr(rqstp));
7b9e8522 JL	344	rpc_set_port((struct sockaddr *)&rp->c_addr, rpc_get_port(svc_addr(rqstp)));
1da177e4 LT	345	rp->c_prot = proto;
1da177e4 LT	346	rp->c_vers = vers;
1da177e4 LT	347
1da177e4 LT	348	hash_refile(rp);
56c2548b	349	lru_put_end(rp);
1da177e4 LT	350
	351	/* release any buffer */
	352	if (rp->c_type == RC_REPLBUFF) {
	353	kfree(rp->c_replvec.iov_base);
	354	rp->c_replvec.iov_base = NULL;
	355	}
	356	rp->c_type = RC_NOCACHE;
	357	out:
	358	spin_unlock(&cache_lock);
	359	return rtn;
	360
	361	found_entry:
0338dd15	362	nfsdstats.rchits++;
1da177e4 LT	363	/* We found a matching entry which is either in progress or done. */
1da177e4 LT	364	age = jiffies - rp->c_timestamp;
1da177e4 LT	365	lru_put_end(rp);
	366
	367	rtn = RC_DROPIT;
	368	/* Request being processed or excessive rexmits */
	369	if (rp->c_state == RC_INPROG \|\| age < RC_DELAY)
	370	goto out;
	371
	372	/* From the hall of fame of impractical attacks:
	373	* Is this a user who tries to snoop on the cache? */
	374	rtn = RC_DOIT;
	375	if (!rqstp->rq_secure && rp->c_secure)
	376	goto out;
	377
	378	/* Compose RPC reply header */
	379	switch (rp->c_type) {
	380	case RC_NOCACHE:
	381	break;
	382	case RC_REPLSTAT:
	383	svc_putu32(&rqstp->rq_res.head[0], rp->c_replstat);
	384	rtn = RC_REPLY;
	385	break;
	386	case RC_REPLBUFF:
	387	if (!nfsd_cache_append(rqstp, &rp->c_replvec))
	388	goto out; /* should not happen */
	389	rtn = RC_REPLY;
	390	break;
	391	default:
	392	printk(KERN_WARNING "nfsd: bad repcache type %d\n", rp->c_type);
0338dd15	393	nfsd_reply_cache_free_locked(rp);
1da177e4 LT	394	}
	395
	396	goto out;
	397	}
	398
	399	/*
	400	* Update a cache entry. This is called from nfsd_dispatch when
	401	* the procedure has been executed and the complete reply is in
	402	* rqstp->rq_res.
	403	*
	404	* We're copying around data here rather than swapping buffers because
	405	* the toplevel loop requires max-sized buffers, which would be a waste
	406	* of memory for a cache with a max reply size of 100 bytes (diropokres).
	407	*
	408	* If we should start to use different types of cache entries tailored
	409	* specifically for attrstat and fh's, we may save even more space.
	410	*
	411	* Also note that a cachetype of RC_NOCACHE can legally be passed when
	412	* nfsd failed to encode a reply that otherwise would have been cached.
	413	* In this case, nfsd_cache_update is called with statp == NULL.
	414	*/
	415	void
c7afef1f	416	nfsd_cache_update(struct svc_rqst rqstp, int cachetype, __be32 statp)
1da177e4	417	{
13cc8a78	418	struct svc_cacherep *rp = rqstp->rq_cacherep;
1da177e4 LT	419	struct kvec resv = &rqstp->rq_res.head[0], cachv;
	420	int len;
	421
13cc8a78	422	if (!rp)
1da177e4 LT	423	return;
	424
	425	len = resv->iov_len - ((char)statp - (char)resv->iov_base);
	426	len >>= 2;
fca4217c	427
1da177e4 LT	428	/* Don't cache excessive amounts of data and XDR failures */
1da177e4 LT	429	if (!statp \|\| len > (256 >> 2)) {
2c6b691c	430	nfsd_reply_cache_free(rp);
1da177e4 LT	431	return;
	432	}
	433
	434	switch (cachetype) {
	435	case RC_REPLSTAT:
	436	if (len != 1)
	437	printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
	438	rp->c_replstat = *statp;
	439	break;
	440	case RC_REPLBUFF:
	441	cachv = &rp->c_replvec;
	442	cachv->iov_base = kmalloc(len << 2, GFP_KERNEL);
	443	if (!cachv->iov_base) {
2c6b691c	444	nfsd_reply_cache_free(rp);
1da177e4 LT	445	return;
	446	}
	447	cachv->iov_len = len << 2;
	448	memcpy(cachv->iov_base, statp, len << 2);
	449	break;
2c6b691c JL	450	case RC_NOCACHE:
	451	nfsd_reply_cache_free(rp);
	452	return;
1da177e4 LT	453	}
	454	spin_lock(&cache_lock);
	455	lru_put_end(rp);
	456	rp->c_secure = rqstp->rq_secure;
	457	rp->c_type = cachetype;
	458	rp->c_state = RC_DONE;
1da177e4 LT	459	spin_unlock(&cache_lock);
	460	return;
	461	}
	462
	463	/*
	464	* Copy cached reply to current reply buffer. Should always fit.
	465	* FIXME as reply is in a page, we should just attach the page, and
	466	* keep a refcount....
	467	*/
	468	static int
	469	nfsd_cache_append(struct svc_rqst rqstp, struct kvec data)
	470	{
	471	struct kvec *vec = &rqstp->rq_res.head[0];
	472
	473	if (vec->iov_len + data->iov_len > PAGE_SIZE) {
	474	printk(KERN_WARNING "nfsd: cached reply too large (%Zd).\n",
	475	data->iov_len);
	476	return 0;
	477	}
	478	memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
	479	vec->iov_len += data->iov_len;
	480	return 1;
	481	}