Adding upstream version 4.19.249.upstream/4.19.249

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 614 insertions, 0 deletions

diff --git a/fs/nfsd/nfscache.c b/fs/nfsd/nfscache.c
new file mode 100644
index 000000000..dbdeb9d6a
--- /dev/null
+++ b/fs/nfsd/nfscache.c
@@ -0,0 +1,614 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * 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/vmalloc.h>
+#include <linux/sunrpc/addr.h>
+#include <linux/highmem.h>
+#include <linux/log2.h>
+#include <linux/hash.h>
+#include <net/checksum.h>
+
+#include "nfsd.h"
+#include "cache.h"
+
+#define NFSDDBG_FACILITY	NFSDDBG_REPCACHE
+
+/*
+ * We use this value to determine the number of hash buckets from the max
+ * cache size, the idea being that when the cache is at its maximum number
+ * of entries, then this should be the average number of entries per bucket.
+ */
+#define TARGET_BUCKET_SIZE	64
+
+struct nfsd_drc_bucket {
+	struct list_head lru_head;
+	spinlock_t cache_lock;
+};
+
+static struct nfsd_drc_bucket	*drc_hashtbl;
+static struct kmem_cache	*drc_slab;
+
+/* max number of entries allowed in the cache */
+static unsigned int		max_drc_entries;
+
+/* number of significant bits in the hash value */
+static unsigned int		maskbits;
+static unsigned int		drc_hashsize;
+
+/*
+ * Stats and other tracking of on the duplicate reply cache. All of these and
+ * the "rc" fields in nfsdstats are protected by the cache_lock
+ */
+
+/* total number of entries */
+static atomic_t			num_drc_entries;
+
+/* cache misses due only to checksum comparison failures */
+static unsigned int		payload_misses;
+
+/* amount of memory (in bytes) currently consumed by the DRC */
+static unsigned int		drc_mem_usage;
+
+/* longest hash chain seen */
+static unsigned int		longest_chain;
+
+/* size of cache when we saw the longest hash chain */
+static unsigned int		longest_chain_cachesize;
+
+static int	nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
+static unsigned long nfsd_reply_cache_count(struct shrinker *shrink,
+					    struct shrink_control *sc);
+static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink,
+					   struct shrink_control *sc);
+
+static struct shrinker nfsd_reply_cache_shrinker = {
+	.scan_objects = nfsd_reply_cache_scan,
+	.count_objects = nfsd_reply_cache_count,
+	.seeks	= 1,
+};
+
+/*
+ * 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);
+}
+
+/*
+ * Compute the number of hash buckets we need. Divide the max cachesize by
+ * the "target" max bucket size, and round up to next power of two.
+ */
+static unsigned int
+nfsd_hashsize(unsigned int limit)
+{
+	return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE);
+}
+
+static u32
+nfsd_cache_hash(__be32 xid)
+{
+	return hash_32(be32_to_cpu(xid), maskbits);
+}
+
+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);
+	}
+	return rp;
+}
+
+static void
+nfsd_reply_cache_free_locked(struct svc_cacherep *rp)
+{
+	if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
+		drc_mem_usage -= rp->c_replvec.iov_len;
+		kfree(rp->c_replvec.iov_base);
+	}
+	list_del(&rp->c_lru);
+	atomic_dec(&num_drc_entries);
+	drc_mem_usage -= sizeof(*rp);
+	kmem_cache_free(drc_slab, rp);
+}
+
+static void
+nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
+{
+	spin_lock(&b->cache_lock);
+	nfsd_reply_cache_free_locked(rp);
+	spin_unlock(&b->cache_lock);
+}
+
+int nfsd_reply_cache_init(void)
+{
+	unsigned int hashsize;
+	unsigned int i;
+	int status = 0;
+
+	max_drc_entries = nfsd_cache_size_limit();
+	atomic_set(&num_drc_entries, 0);
+	hashsize = nfsd_hashsize(max_drc_entries);
+	maskbits = ilog2(hashsize);
+
+	status = register_shrinker(&nfsd_reply_cache_shrinker);
+	if (status)
+		return status;
+
+	drc_slab = kmem_cache_create("nfsd_drc", sizeof(struct svc_cacherep),
+					0, 0, NULL);
+	if (!drc_slab)
+		goto out_nomem;
+
+	drc_hashtbl = kcalloc(hashsize, sizeof(*drc_hashtbl), GFP_KERNEL);
+	if (!drc_hashtbl) {
+		drc_hashtbl = vzalloc(array_size(hashsize,
+						 sizeof(*drc_hashtbl)));
+		if (!drc_hashtbl)
+			goto out_nomem;
+	}
+
+	for (i = 0; i < hashsize; i++) {
+		INIT_LIST_HEAD(&drc_hashtbl[i].lru_head);
+		spin_lock_init(&drc_hashtbl[i].cache_lock);
+	}
+	drc_hashsize = hashsize;
+
+	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;
+	unsigned int i;
+
+	unregister_shrinker(&nfsd_reply_cache_shrinker);
+
+	for (i = 0; i < drc_hashsize; i++) {
+		struct list_head *head = &drc_hashtbl[i].lru_head;
+		while (!list_empty(head)) {
+			rp = list_first_entry(head, struct svc_cacherep, c_lru);
+			nfsd_reply_cache_free_locked(rp);
+		}
+	}
+
+	kvfree(drc_hashtbl);
+	drc_hashtbl = NULL;
+	drc_hashsize = 0;
+
+	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 nfsd_drc_bucket *b, struct svc_cacherep *rp)
+{
+	rp->c_timestamp = jiffies;
+	list_move_tail(&rp->c_lru, &b->lru_head);
+}
+
+static long
+prune_bucket(struct nfsd_drc_bucket *b)
+{
+	struct svc_cacherep *rp, *tmp;
+	long freed = 0;
+
+	list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) {
+		/*
+		 * Don't free entries attached to calls that are still
+		 * in-progress, but do keep scanning the list.
+		 */
+		if (rp->c_state == RC_INPROG)
+			continue;
+		if (atomic_read(&num_drc_entries) <= max_drc_entries &&
+		    time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
+			break;
+		nfsd_reply_cache_free_locked(rp);
+		freed++;
+	}
+	return freed;
+}
+
+/*
+ * 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 long
+prune_cache_entries(void)
+{
+	unsigned int i;
+	long freed = 0;
+
+	for (i = 0; i < drc_hashsize; i++) {
+		struct nfsd_drc_bucket *b = &drc_hashtbl[i];
+
+		if (list_empty(&b->lru_head))
+			continue;
+		spin_lock(&b->cache_lock);
+		freed += prune_bucket(b);
+		spin_unlock(&b->cache_lock);
+	}
+	return freed;
+}
+
+static unsigned long
+nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+	return atomic_read(&num_drc_entries);
+}
+
+static unsigned long
+nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+	return prune_cache_entries();
+}
+/*
+ * Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes
+ */
+static __wsum
+nfsd_cache_csum(struct svc_rqst *rqstp)
+{
+	int idx;
+	unsigned int base;
+	__wsum csum;
+	struct xdr_buf *buf = &rqstp->rq_arg;
+	const unsigned char *p = buf->head[0].iov_base;
+	size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len,
+				RC_CSUMLEN);
+	size_t len = min(buf->head[0].iov_len, csum_len);
+
+	/* rq_arg.head first */
+	csum = csum_partial(p, len, 0);
+	csum_len -= len;
+
+	/* Continue into page array */
+	idx = buf->page_base / PAGE_SIZE;
+	base = buf->page_base & ~PAGE_MASK;
+	while (csum_len) {
+		p = page_address(buf->pages[idx]) + base;
+		len = min_t(size_t, PAGE_SIZE - base, csum_len);
+		csum = csum_partial(p, len, csum);
+		csum_len -= len;
+		base = 0;
+		++idx;
+	}
+	return csum;
+}
+
+static bool
+nfsd_cache_match(struct svc_rqst *rqstp, __wsum csum, struct svc_cacherep *rp)
+{
+	/* Check RPC XID first */
+	if (rqstp->rq_xid != rp->c_xid)
+		return false;
+	/* compare checksum of NFS data */
+	if (csum != rp->c_csum) {
+		++payload_misses;
+		return false;
+	}
+
+	/* Other discriminators */
+	if (rqstp->rq_proc != rp->c_proc ||
+	    rqstp->rq_prot != rp->c_prot ||
+	    rqstp->rq_vers != rp->c_vers ||
+	    rqstp->rq_arg.len != rp->c_len ||
+	    !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 false;
+
+	return true;
+}
+
+/*
+ * 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 nfsd_drc_bucket *b, struct svc_rqst *rqstp,
+		__wsum csum)
+{
+	struct svc_cacherep	*rp, *ret = NULL;
+	struct list_head 	*rh = &b->lru_head;
+	unsigned int		entries = 0;
+
+	list_for_each_entry(rp, rh, c_lru) {
+		++entries;
+		if (nfsd_cache_match(rqstp, csum, rp)) {
+			ret = rp;
+			break;
+		}
+	}
+
+	/* tally hash chain length stats */
+	if (entries > longest_chain) {
+		longest_chain = entries;
+		longest_chain_cachesize = atomic_read(&num_drc_entries);
+	} else if (entries == longest_chain) {
+		/* prefer to keep the smallest cachesize possible here */
+		longest_chain_cachesize = min_t(unsigned int,
+				longest_chain_cachesize,
+				atomic_read(&num_drc_entries));
+	}
+
+	return ret;
+}
+
+/*
+ * Try to find an entry matching the current call in the cache. When none
+ * is found, we try to grab the oldest expired entry off the LRU list. If
+ * a suitable one isn't there, then drop the cache_lock and allocate a
+ * new one, then search again in case one got inserted while this thread
+ * didn't hold the lock.
+ */
+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;
+	__wsum			csum;
+	u32 hash = nfsd_cache_hash(xid);
+	struct nfsd_drc_bucket *b = &drc_hashtbl[hash];
+	int type = rqstp->rq_cachetype;
+	int rtn = RC_DOIT;
+
+	rqstp->rq_cacherep = NULL;
+	if (type == RC_NOCACHE) {
+		nfsdstats.rcnocache++;
+		return rtn;
+	}
+
+	csum = nfsd_cache_csum(rqstp);
+
+	/*
+	 * Since the common case is a cache miss followed by an insert,
+	 * preallocate an entry.
+	 */
+	rp = nfsd_reply_cache_alloc();
+	spin_lock(&b->cache_lock);
+	if (likely(rp)) {
+		atomic_inc(&num_drc_entries);
+		drc_mem_usage += sizeof(*rp);
+	}
+
+	/* go ahead and prune the cache */
+	prune_bucket(b);
+
+	found = nfsd_cache_search(b, rqstp, csum);
+	if (found) {
+		if (likely(rp))
+			nfsd_reply_cache_free_locked(rp);
+		rp = found;
+		goto found_entry;
+	}
+
+	if (!rp) {
+		dprintk("nfsd: unable to allocate DRC entry!\n");
+		goto out;
+	}
+
+	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;
+	rp->c_len = rqstp->rq_arg.len;
+	rp->c_csum = csum;
+
+	lru_put_end(b, rp);
+
+	/* release any buffer */
+	if (rp->c_type == RC_REPLBUFF) {
+		drc_mem_usage -= rp->c_replvec.iov_len;
+		kfree(rp->c_replvec.iov_base);
+		rp->c_replvec.iov_base = NULL;
+	}
+	rp->c_type = RC_NOCACHE;
+ out:
+	spin_unlock(&b->cache_lock);
+	return rtn;
+
+found_entry:
+	nfsdstats.rchits++;
+	/* We found a matching entry which is either in progress or done. */
+	lru_put_end(b, rp);
+
+	rtn = RC_DROPIT;
+	/* Request being processed */
+	if (rp->c_state == RC_INPROG)
+		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 (!test_bit(RQ_SECURE, &rqstp->rq_flags) && 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;
+	u32		hash;
+	struct nfsd_drc_bucket *b;
+	int		len;
+	size_t		bufsize = 0;
+
+	if (!rp)
+		return;
+
+	hash = nfsd_cache_hash(rp->c_xid);
+	b = &drc_hashtbl[hash];
+
+	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(b, 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;
+		bufsize = len << 2;
+		cachv->iov_base = kmalloc(bufsize, GFP_KERNEL);
+		if (!cachv->iov_base) {
+			nfsd_reply_cache_free(b, rp);
+			return;
+		}
+		cachv->iov_len = bufsize;
+		memcpy(cachv->iov_base, statp, bufsize);
+		break;
+	case RC_NOCACHE:
+		nfsd_reply_cache_free(b, rp);
+		return;
+	}
+	spin_lock(&b->cache_lock);
+	drc_mem_usage += bufsize;
+	lru_put_end(b, rp);
+	rp->c_secure = test_bit(RQ_SECURE, &rqstp->rq_flags);
+	rp->c_type = cachetype;
+	rp->c_state = RC_DONE;
+	spin_unlock(&b->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;
+}
+
+/*
+ * Note that fields may be added, removed or reordered in the future. Programs
+ * scraping this file for info should test the labels to ensure they're
+ * getting the correct field.
+ */
+static int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
+{
+	seq_printf(m, "max entries:           %u\n", max_drc_entries);
+	seq_printf(m, "num entries:           %u\n",
+			atomic_read(&num_drc_entries));
+	seq_printf(m, "hash buckets:          %u\n", 1 << maskbits);
+	seq_printf(m, "mem usage:             %u\n", drc_mem_usage);
+	seq_printf(m, "cache hits:            %u\n", nfsdstats.rchits);
+	seq_printf(m, "cache misses:          %u\n", nfsdstats.rcmisses);
+	seq_printf(m, "not cached:            %u\n", nfsdstats.rcnocache);
+	seq_printf(m, "payload misses:        %u\n", payload_misses);
+	seq_printf(m, "longest chain len:     %u\n", longest_chain);
+	seq_printf(m, "cachesize at longest:  %u\n", longest_chain_cachesize);
+	return 0;
+}
+
+int nfsd_reply_cache_stats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, nfsd_reply_cache_stats_show, NULL);
+}