[mirror_ubuntu-bionic-kernel.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/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);
}

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