patch-2.1.32 linux/fs/nfsd/nfscache.c

• Lines: 322
• Date: Fri Apr 4 11:06:02 1997
• Orig file: v2.1.31/linux/fs/nfsd/nfscache.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.1.31/linux/fs/nfsd/nfscache.c linux/fs/nfsd/nfscache.c
@@ -0,0 +1,321 @@
+/*
+ * 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/malloc.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[HASHSIZE];
+static struct svc_cacherep *	lru_head;
+static struct svc_cacherep *	lru_tail;
+static struct svc_cacherep	nfscache[CACHESIZE];
+static int			cache_initialized = 0;
+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;
+	int			i;
+
+	if (cache_initialized)
+		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;
+
+	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;
+}
+
+/*
+ * 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;
+	struct svc_client	*clp = rqstp->rq_client;
+	u32			xid = rqstp->rq_xid,
+				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 &&
+		    exp_checkaddr(clp, rp->c_client)) {
+			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 = 0;
+
+		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_client = rqstp->rq_addr.sin_addr;
+	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;
+
+	/* Don't cache excessive amounts of data and XDR failures */
+	if (!statp || (len = resp->buf - statp) > (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);
+	resp->buf += ((data->len + 3) >> 2);
+	resp->len += data->len;
+	return 1;
+}