1 files changed, 328 insertions, 0 deletions
diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
new file mode 100644
index 00000000000..119e4d4495b
--- /dev/null
+++ b/fs/nfsd/nfscache.c
@@ -0,0 +1,328 @@
+/*
+ * 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/time.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/spinlock.h>
+#include <linux/list.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))
+
+static struct hlist_head *	hash_list;
+static struct list_head 	lru_head;
+static int			cache_disabled = 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);
+
+void
+nfsd_cache_init(void)
+{
+	struct svc_cacherep	*rp;
+	int			i;
+
+	INIT_LIST_HEAD(&lru_head);
+	i = CACHESIZE;
+	while(i) {
+		rp = kmalloc(sizeof(*rp), GFP_KERNEL);
+		if (!rp) break;
+		list_add(&rp->c_lru, &lru_head);
+		rp->c_state = RC_UNUSED;
+		rp->c_type = RC_NOCACHE;
+		INIT_HLIST_NODE(&rp->c_hash);
+		i--;
+	}
+
+	if (i)
+		printk (KERN_ERR "nfsd: cannot allocate all %d cache entries, only got %d\n",
+			CACHESIZE, CACHESIZE-i);
+
+	hash_list = kmalloc (HASHSIZE * sizeof(struct hlist_head), GFP_KERNEL);
+	if (!hash_list) {
+		nfsd_cache_shutdown();
+		printk (KERN_ERR "nfsd: cannot allocate %Zd bytes for hash list\n",
+			HASHSIZE * sizeof(struct hlist_head));
+		return;
+	}
+	memset(hash_list, 0, HASHSIZE * sizeof(struct hlist_head));
+
+	cache_disabled = 0;
+}
+
+void
+nfsd_cache_shutdown(void)
+{
+	struct svc_cacherep	*rp;
+
+	while (!list_empty(&lru_head)) {
+		rp = list_entry(lru_head.next, struct svc_cacherep, c_lru);
+		if (rp->c_state == RC_DONE && rp->c_type == RC_REPLBUFF)
+			kfree(rp->c_replvec.iov_base);
+		list_del(&rp->c_lru);
+		kfree(rp);
+	}
+
+	cache_disabled = 1;
+
+	if (hash_list)
+		kfree (hash_list);
+	hash_list = NULL;
+}
+
+/*
+ * Move cache entry to end of LRU list
+ */
+static void
+lru_put_end(struct svc_cacherep *rp)
+{
+	list_del(&rp->c_lru);
+	list_add_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, hash_list + REQHASH(rp->c_xid));
+}
+
+/*
+ * 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 hlist_node	*hn;
+	struct hlist_head 	*rh;
+	struct svc_cacherep	*rp;
+	u32			xid = rqstp->rq_xid,
+				proto =  rqstp->rq_prot,
+				vers = rqstp->rq_vers,
+				proc = rqstp->rq_proc;
+	unsigned long		age;
+	int rtn;
+
+	rqstp->rq_cacherep = NULL;
+	if (cache_disabled || type == RC_NOCACHE) {
+		nfsdstats.rcnocache++;
+		return RC_DOIT;
+	}
+
+	spin_lock(&cache_lock);
+	rtn = RC_DOIT;
+
+	rh = &hash_list[REQHASH(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 &&
+		    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;
+	list_for_each_entry(rp, &lru_head, c_lru) {
+		if (rp->c_state != RC_INPROG)
+			break;
+		if (safe++ > CACHESIZE) {
+			printk("nfsd: loop in repcache LRU list\n");
+			cache_disabled = 1;
+			goto out;
+		}
+	}
+	}
+
+	/* 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;
+		}
+		goto out;
+	}
+
+	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_replvec.iov_base);
+		rp->c_replvec.iov_base = NULL;
+	}
+	rp->c_type = RC_NOCACHE;
+ out:
+	spin_unlock(&cache_lock);
+	return rtn;
+
+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_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);
+		rp->c_state = RC_UNUSED;
+	}
+
+	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, u32 *statp)
+{
+	struct svc_cacherep *rp;
+	struct kvec	*resv = &rqstp->rq_res.head[0], *cachv;
+	int		len;
+
+	if (!(rp = rqstp->rq_cacherep) || cache_disabled)
+		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) {
+			spin_lock(&cache_lock);
+			rp->c_state = RC_UNUSED;
+			spin_unlock(&cache_lock);
+			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;
+	rp->c_timestamp = jiffies;
+	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;
+}