--- /dev/null
+
+The NFS client
+==============
+
+The NFS version 2 protocol was first documented in RFC1094 (March 1989).
+Since then two more major releases of NFS have been published, with NFSv3
+being documented in RFC1813 (June 1995), and NFSv4 in RFC3530 (April
+2003).
+
+The Linux NFS client currently supports all the above published versions,
+and work is in progress on adding support for minor version 1 of the NFSv4
+protocol.
+
+The purpose of this document is to provide information on some of the
+upcall interfaces that are used in order to provide the NFS client with
+some of the information that it requires in order to fully comply with
+the NFS spec.
+
+The DNS resolver
+================
+
+NFSv4 allows for one server to refer the NFS client to data that has been
+migrated onto another server by means of the special "fs_locations"
+attribute. See
+ http://tools.ietf.org/html/rfc3530#section-6
+and
+ http://tools.ietf.org/html/draft-ietf-nfsv4-referrals-00
+
+The fs_locations information can take the form of either an ip address and
+a path, or a DNS hostname and a path. The latter requires the NFS client to
+do a DNS lookup in order to mount the new volume, and hence the need for an
+upcall to allow userland to provide this service.
+
+Assuming that the user has the 'rpc_pipefs' filesystem mounted in the usual
+/var/lib/nfs/rpc_pipefs, the upcall consists of the following steps:
+
+ (1) The process checks the dns_resolve cache to see if it contains a
+ valid entry. If so, it returns that entry and exits.
+
+ (2) If no valid entry exists, the helper script '/sbin/nfs_cache_getent'
+ (may be changed using the 'nfs.cache_getent' kernel boot parameter)
+ is run, with two arguments:
+ - the cache name, "dns_resolve"
+ - the hostname to resolve
+
+ (3) After looking up the corresponding ip address, the helper script
+ writes the result into the rpc_pipefs pseudo-file
+ '/var/lib/nfs/rpc_pipefs/cache/dns_resolve/channel'
+ in the following (text) format:
+
+ "<ip address> <hostname> <ttl>\n"
+
+ Where <ip address> is in the usual IPv4 (123.456.78.90) or IPv6
+ (ffee:ddcc:bbaa:9988:7766:5544:3322:1100, ffee::1100, ...) format.
+ <hostname> is identical to the second argument of the helper
+ script, and <ttl> is the 'time to live' of this cache entry (in
+ units of seconds).
+
+ Note: If <ip address> is invalid, say the string "0", then a negative
+ entry is created, which will cause the kernel to treat the hostname
+ as having no valid DNS translation.
+
+
+
+
+A basic sample /sbin/nfs_cache_getent
+=====================================
+
+#!/bin/bash
+#
+ttl=600
+#
+cut=/usr/bin/cut
+getent=/usr/bin/getent
+rpc_pipefs=/var/lib/nfs/rpc_pipefs
+#
+die()
+{
+ echo "Usage: $0 cache_name entry_name"
+ exit 1
+}
+
+[ $# -lt 2 ] && die
+cachename="$1"
+cache_path=${rpc_pipefs}/cache/${cachename}/channel
+
+case "${cachename}" in
+ dns_resolve)
+ name="$2"
+ result="$(${getent} hosts ${name} | ${cut} -f1 -d\ )"
+ [ -z "${result}" ] && result="0"
+ ;;
+ *)
+ die
+ ;;
+esac
+echo "${result} ${name} ${ttl}" >${cache_path}
+
[NFS] set the TCP port on which the NFSv4 callback
channel should listen.
+ nfs.cache_getent=
+ [NFS] sets the pathname to the program which is used
+ to update the NFS client cache entries.
+
+ nfs.cache_getent_timeout=
+ [NFS] sets the timeout after which an attempt to
+ update a cache entry is deemed to have failed.
+
nfs.idmap_cache_timeout=
[NFS] set the maximum lifetime for idmapper cache
entries.
nfs-y := client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \
direct.o pagelist.o proc.o read.o symlink.o unlink.o \
- write.o namespace.o mount_clnt.o
+ write.o namespace.o mount_clnt.o \
+ dns_resolve.o cache_lib.o
nfs-$(CONFIG_ROOT_NFS) += nfsroot.o
nfs-$(CONFIG_NFS_V3) += nfs3proc.o nfs3xdr.o
nfs-$(CONFIG_NFS_V3_ACL) += nfs3acl.o
--- /dev/null
+/*
+ * linux/fs/nfs/cache_lib.c
+ *
+ * Helper routines for the NFS client caches
+ *
+ * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
+ */
+#include <linux/kmod.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/sunrpc/cache.h>
+#include <linux/sunrpc/rpc_pipe_fs.h>
+
+#include "cache_lib.h"
+
+#define NFS_CACHE_UPCALL_PATHLEN 256
+#define NFS_CACHE_UPCALL_TIMEOUT 15
+
+static char nfs_cache_getent_prog[NFS_CACHE_UPCALL_PATHLEN] =
+ "/sbin/nfs_cache_getent";
+static unsigned long nfs_cache_getent_timeout = NFS_CACHE_UPCALL_TIMEOUT;
+
+module_param_string(cache_getent, nfs_cache_getent_prog,
+ sizeof(nfs_cache_getent_prog), 0600);
+MODULE_PARM_DESC(cache_getent, "Path to the client cache upcall program");
+module_param_named(cache_getent_timeout, nfs_cache_getent_timeout, ulong, 0600);
+MODULE_PARM_DESC(cache_getent_timeout, "Timeout (in seconds) after which "
+ "the cache upcall is assumed to have failed");
+
+int nfs_cache_upcall(struct cache_detail *cd, char *entry_name)
+{
+ static char *envp[] = { "HOME=/",
+ "TERM=linux",
+ "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
+ NULL
+ };
+ char *argv[] = {
+ nfs_cache_getent_prog,
+ cd->name,
+ entry_name,
+ NULL
+ };
+ int ret = -EACCES;
+
+ if (nfs_cache_getent_prog[0] == '\0')
+ goto out;
+ ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+ /*
+ * Disable the upcall mechanism if we're getting an ENOENT or
+ * EACCES error. The admin can re-enable it on the fly by using
+ * sysfs to set the 'cache_getent' parameter once the problem
+ * has been fixed.
+ */
+ if (ret == -ENOENT || ret == -EACCES)
+ nfs_cache_getent_prog[0] = '\0';
+out:
+ return ret > 0 ? 0 : ret;
+}
+
+/*
+ * Deferred request handling
+ */
+void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq)
+{
+ if (atomic_dec_and_test(&dreq->count))
+ kfree(dreq);
+}
+
+static void nfs_dns_cache_revisit(struct cache_deferred_req *d, int toomany)
+{
+ struct nfs_cache_defer_req *dreq;
+
+ dreq = container_of(d, struct nfs_cache_defer_req, deferred_req);
+
+ complete_all(&dreq->completion);
+ nfs_cache_defer_req_put(dreq);
+}
+
+static struct cache_deferred_req *nfs_dns_cache_defer(struct cache_req *req)
+{
+ struct nfs_cache_defer_req *dreq;
+
+ dreq = container_of(req, struct nfs_cache_defer_req, req);
+ dreq->deferred_req.revisit = nfs_dns_cache_revisit;
+ atomic_inc(&dreq->count);
+
+ return &dreq->deferred_req;
+}
+
+struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void)
+{
+ struct nfs_cache_defer_req *dreq;
+
+ dreq = kzalloc(sizeof(*dreq), GFP_KERNEL);
+ if (dreq) {
+ init_completion(&dreq->completion);
+ atomic_set(&dreq->count, 1);
+ dreq->req.defer = nfs_dns_cache_defer;
+ }
+ return dreq;
+}
+
+int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq)
+{
+ if (wait_for_completion_timeout(&dreq->completion,
+ nfs_cache_getent_timeout * HZ) == 0)
+ return -ETIMEDOUT;
+ return 0;
+}
+
+int nfs_cache_register(struct cache_detail *cd)
+{
+ struct nameidata nd;
+ struct vfsmount *mnt;
+ int ret;
+
+ mnt = rpc_get_mount();
+ if (IS_ERR(mnt))
+ return PTR_ERR(mnt);
+ ret = vfs_path_lookup(mnt->mnt_root, mnt, "/cache", 0, &nd);
+ if (ret)
+ goto err;
+ ret = sunrpc_cache_register_pipefs(nd.path.dentry,
+ cd->name, 0600, cd);
+ path_put(&nd.path);
+ if (!ret)
+ return ret;
+err:
+ rpc_put_mount();
+ return ret;
+}
+
+void nfs_cache_unregister(struct cache_detail *cd)
+{
+ sunrpc_cache_unregister_pipefs(cd);
+ rpc_put_mount();
+}
+
--- /dev/null
+/*
+ * Helper routines for the NFS client caches
+ *
+ * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
+ */
+
+#include <linux/completion.h>
+#include <linux/sunrpc/cache.h>
+#include <asm/atomic.h>
+
+/*
+ * Deferred request handling
+ */
+struct nfs_cache_defer_req {
+ struct cache_req req;
+ struct cache_deferred_req deferred_req;
+ struct completion completion;
+ atomic_t count;
+};
+
+extern int nfs_cache_upcall(struct cache_detail *cd, char *entry_name);
+extern struct nfs_cache_defer_req *nfs_cache_defer_req_alloc(void);
+extern void nfs_cache_defer_req_put(struct nfs_cache_defer_req *dreq);
+extern int nfs_cache_wait_for_upcall(struct nfs_cache_defer_req *dreq);
+
+extern int nfs_cache_register(struct cache_detail *cd);
+extern void nfs_cache_unregister(struct cache_detail *cd);
--- /dev/null
+/*
+ * linux/fs/nfs/dns_resolve.c
+ *
+ * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@netapp.com>
+ *
+ * Resolves DNS hostnames into valid ip addresses
+ */
+
+#include <linux/hash.h>
+#include <linux/string.h>
+#include <linux/kmod.h>
+#include <linux/module.h>
+#include <linux/socket.h>
+#include <linux/seq_file.h>
+#include <linux/inet.h>
+#include <linux/sunrpc/clnt.h>
+#include <linux/sunrpc/cache.h>
+#include <linux/sunrpc/svcauth.h>
+
+#include "dns_resolve.h"
+#include "cache_lib.h"
+
+#define NFS_DNS_HASHBITS 4
+#define NFS_DNS_HASHTBL_SIZE (1 << NFS_DNS_HASHBITS)
+
+static struct cache_head *nfs_dns_table[NFS_DNS_HASHTBL_SIZE];
+
+struct nfs_dns_ent {
+ struct cache_head h;
+
+ char *hostname;
+ size_t namelen;
+
+ struct sockaddr_storage addr;
+ size_t addrlen;
+};
+
+
+static void nfs_dns_ent_init(struct cache_head *cnew,
+ struct cache_head *ckey)
+{
+ struct nfs_dns_ent *new;
+ struct nfs_dns_ent *key;
+
+ new = container_of(cnew, struct nfs_dns_ent, h);
+ key = container_of(ckey, struct nfs_dns_ent, h);
+
+ kfree(new->hostname);
+ new->hostname = kstrndup(key->hostname, key->namelen, GFP_KERNEL);
+ if (new->hostname) {
+ new->namelen = key->namelen;
+ memcpy(&new->addr, &key->addr, key->addrlen);
+ new->addrlen = key->addrlen;
+ } else {
+ new->namelen = 0;
+ new->addrlen = 0;
+ }
+}
+
+static void nfs_dns_ent_put(struct kref *ref)
+{
+ struct nfs_dns_ent *item;
+
+ item = container_of(ref, struct nfs_dns_ent, h.ref);
+ kfree(item->hostname);
+ kfree(item);
+}
+
+static struct cache_head *nfs_dns_ent_alloc(void)
+{
+ struct nfs_dns_ent *item = kmalloc(sizeof(*item), GFP_KERNEL);
+
+ if (item != NULL) {
+ item->hostname = NULL;
+ item->namelen = 0;
+ item->addrlen = 0;
+ return &item->h;
+ }
+ return NULL;
+};
+
+static unsigned int nfs_dns_hash(const struct nfs_dns_ent *key)
+{
+ return hash_str(key->hostname, NFS_DNS_HASHBITS);
+}
+
+static void nfs_dns_request(struct cache_detail *cd,
+ struct cache_head *ch,
+ char **bpp, int *blen)
+{
+ struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
+
+ qword_add(bpp, blen, key->hostname);
+ (*bpp)[-1] = '\n';
+}
+
+static int nfs_dns_upcall(struct cache_detail *cd,
+ struct cache_head *ch)
+{
+ struct nfs_dns_ent *key = container_of(ch, struct nfs_dns_ent, h);
+ int ret;
+
+ ret = nfs_cache_upcall(cd, key->hostname);
+ if (ret)
+ ret = sunrpc_cache_pipe_upcall(cd, ch, nfs_dns_request);
+ return ret;
+}
+
+static int nfs_dns_match(struct cache_head *ca,
+ struct cache_head *cb)
+{
+ struct nfs_dns_ent *a;
+ struct nfs_dns_ent *b;
+
+ a = container_of(ca, struct nfs_dns_ent, h);
+ b = container_of(cb, struct nfs_dns_ent, h);
+
+ if (a->namelen == 0 || a->namelen != b->namelen)
+ return 0;
+ return memcmp(a->hostname, b->hostname, a->namelen) == 0;
+}
+
+static int nfs_dns_show(struct seq_file *m, struct cache_detail *cd,
+ struct cache_head *h)
+{
+ struct nfs_dns_ent *item;
+ long ttl;
+
+ if (h == NULL) {
+ seq_puts(m, "# ip address hostname ttl\n");
+ return 0;
+ }
+ item = container_of(h, struct nfs_dns_ent, h);
+ ttl = (long)item->h.expiry_time - (long)get_seconds();
+ if (ttl < 0)
+ ttl = 0;
+
+ if (!test_bit(CACHE_NEGATIVE, &h->flags)) {
+ char buf[INET6_ADDRSTRLEN+IPV6_SCOPE_ID_LEN+1];
+
+ rpc_ntop((struct sockaddr *)&item->addr, buf, sizeof(buf));
+ seq_printf(m, "%15s ", buf);
+ } else
+ seq_puts(m, "<none> ");
+ seq_printf(m, "%15s %ld\n", item->hostname, ttl);
+ return 0;
+}
+
+struct nfs_dns_ent *nfs_dns_lookup(struct cache_detail *cd,
+ struct nfs_dns_ent *key)
+{
+ struct cache_head *ch;
+
+ ch = sunrpc_cache_lookup(cd,
+ &key->h,
+ nfs_dns_hash(key));
+ if (!ch)
+ return NULL;
+ return container_of(ch, struct nfs_dns_ent, h);
+}
+
+struct nfs_dns_ent *nfs_dns_update(struct cache_detail *cd,
+ struct nfs_dns_ent *new,
+ struct nfs_dns_ent *key)
+{
+ struct cache_head *ch;
+
+ ch = sunrpc_cache_update(cd,
+ &new->h, &key->h,
+ nfs_dns_hash(key));
+ if (!ch)
+ return NULL;
+ return container_of(ch, struct nfs_dns_ent, h);
+}
+
+static int nfs_dns_parse(struct cache_detail *cd, char *buf, int buflen)
+{
+ char buf1[NFS_DNS_HOSTNAME_MAXLEN+1];
+ struct nfs_dns_ent key, *item;
+ unsigned long ttl;
+ ssize_t len;
+ int ret = -EINVAL;
+
+ if (buf[buflen-1] != '\n')
+ goto out;
+ buf[buflen-1] = '\0';
+
+ len = qword_get(&buf, buf1, sizeof(buf1));
+ if (len <= 0)
+ goto out;
+ key.addrlen = rpc_pton(buf1, len,
+ (struct sockaddr *)&key.addr,
+ sizeof(key.addr));
+
+ len = qword_get(&buf, buf1, sizeof(buf1));
+ if (len <= 0)
+ goto out;
+
+ key.hostname = buf1;
+ key.namelen = len;
+ memset(&key.h, 0, sizeof(key.h));
+
+ ttl = get_expiry(&buf);
+ if (ttl == 0)
+ goto out;
+ key.h.expiry_time = ttl + get_seconds();
+
+ ret = -ENOMEM;
+ item = nfs_dns_lookup(cd, &key);
+ if (item == NULL)
+ goto out;
+
+ if (key.addrlen == 0)
+ set_bit(CACHE_NEGATIVE, &key.h.flags);
+
+ item = nfs_dns_update(cd, &key, item);
+ if (item == NULL)
+ goto out;
+
+ ret = 0;
+ cache_put(&item->h, cd);
+out:
+ return ret;
+}
+
+static struct cache_detail nfs_dns_resolve = {
+ .owner = THIS_MODULE,
+ .hash_size = NFS_DNS_HASHTBL_SIZE,
+ .hash_table = nfs_dns_table,
+ .name = "dns_resolve",
+ .cache_put = nfs_dns_ent_put,
+ .cache_upcall = nfs_dns_upcall,
+ .cache_parse = nfs_dns_parse,
+ .cache_show = nfs_dns_show,
+ .match = nfs_dns_match,
+ .init = nfs_dns_ent_init,
+ .update = nfs_dns_ent_init,
+ .alloc = nfs_dns_ent_alloc,
+};
+
+static int do_cache_lookup(struct cache_detail *cd,
+ struct nfs_dns_ent *key,
+ struct nfs_dns_ent **item,
+ struct nfs_cache_defer_req *dreq)
+{
+ int ret = -ENOMEM;
+
+ *item = nfs_dns_lookup(cd, key);
+ if (*item) {
+ ret = cache_check(cd, &(*item)->h, &dreq->req);
+ if (ret)
+ *item = NULL;
+ }
+ return ret;
+}
+
+static int do_cache_lookup_nowait(struct cache_detail *cd,
+ struct nfs_dns_ent *key,
+ struct nfs_dns_ent **item)
+{
+ int ret = -ENOMEM;
+
+ *item = nfs_dns_lookup(cd, key);
+ if (!*item)
+ goto out_err;
+ ret = -ETIMEDOUT;
+ if (!test_bit(CACHE_VALID, &(*item)->h.flags)
+ || (*item)->h.expiry_time < get_seconds()
+ || cd->flush_time > (*item)->h.last_refresh)
+ goto out_put;
+ ret = -ENOENT;
+ if (test_bit(CACHE_NEGATIVE, &(*item)->h.flags))
+ goto out_put;
+ return 0;
+out_put:
+ cache_put(&(*item)->h, cd);
+out_err:
+ *item = NULL;
+ return ret;
+}
+
+static int do_cache_lookup_wait(struct cache_detail *cd,
+ struct nfs_dns_ent *key,
+ struct nfs_dns_ent **item)
+{
+ struct nfs_cache_defer_req *dreq;
+ int ret = -ENOMEM;
+
+ dreq = nfs_cache_defer_req_alloc();
+ if (!dreq)
+ goto out;
+ ret = do_cache_lookup(cd, key, item, dreq);
+ if (ret == -EAGAIN) {
+ ret = nfs_cache_wait_for_upcall(dreq);
+ if (!ret)
+ ret = do_cache_lookup_nowait(cd, key, item);
+ }
+ nfs_cache_defer_req_put(dreq);
+out:
+ return ret;
+}
+
+ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
+ struct sockaddr *sa, size_t salen)
+{
+ struct nfs_dns_ent key = {
+ .hostname = name,
+ .namelen = namelen,
+ };
+ struct nfs_dns_ent *item = NULL;
+ ssize_t ret;
+
+ ret = do_cache_lookup_wait(&nfs_dns_resolve, &key, &item);
+ if (ret == 0) {
+ if (salen >= item->addrlen) {
+ memcpy(sa, &item->addr, item->addrlen);
+ ret = item->addrlen;
+ } else
+ ret = -EOVERFLOW;
+ cache_put(&item->h, &nfs_dns_resolve);
+ } else if (ret == -ENOENT)
+ ret = -ESRCH;
+ return ret;
+}
+
+int nfs_dns_resolver_init(void)
+{
+ return nfs_cache_register(&nfs_dns_resolve);
+}
+
+void nfs_dns_resolver_destroy(void)
+{
+ nfs_cache_unregister(&nfs_dns_resolve);
+}
+
--- /dev/null
+/*
+ * Resolve DNS hostnames into valid ip addresses
+ */
+#ifndef __LINUX_FS_NFS_DNS_RESOLVE_H
+#define __LINUX_FS_NFS_DNS_RESOLVE_H
+
+#define NFS_DNS_HOSTNAME_MAXLEN (128)
+
+extern int nfs_dns_resolver_init(void);
+extern void nfs_dns_resolver_destroy(void);
+extern ssize_t nfs_dns_resolve_name(char *name, size_t namelen,
+ struct sockaddr *sa, size_t salen);
+
+#endif
#include "iostat.h"
#include "internal.h"
#include "fscache.h"
+#include "dns_resolve.h"
#define NFSDBG_FACILITY NFSDBG_VFS
{
int err;
+ err = nfs_dns_resolver_init();
+ if (err < 0)
+ goto out8;
+
err = nfs_fscache_register();
if (err < 0)
goto out7;
out6:
nfs_fscache_unregister();
out7:
+ nfs_dns_resolver_destroy();
+out8:
return err;
}
nfs_destroy_inodecache();
nfs_destroy_nfspagecache();
nfs_fscache_unregister();
+ nfs_dns_resolver_destroy();
#ifdef CONFIG_PROC_FS
rpc_proc_unregister("nfs");
#endif
return ERR_PTR(err);
return rpc_mount;
}
+EXPORT_SYMBOL_GPL(rpc_get_mount);
void rpc_put_mount(void)
{
simple_release_fs(&rpc_mount, &rpc_mount_count);
}
+EXPORT_SYMBOL_GPL(rpc_put_mount);
static int rpc_delete_dentry(struct dentry *dentry)
{
RPCAUTH_portmap,
RPCAUTH_statd,
RPCAUTH_nfsd4_cb,
+ RPCAUTH_cache,
RPCAUTH_RootEOF
};
.name = "nfsd4_cb",
.mode = S_IFDIR | S_IRUGO | S_IXUGO,
},
+ [RPCAUTH_cache] = {
+ .name = "cache",
+ .mode = S_IFDIR | S_IRUGO | S_IXUGO,
+ },
};
static int
git://ftp.safe.ca / safe / jmp / linux-2.6 / commitdiff