The NFSv4 and NFSv4.1 protocols both allow for the redirection of a client from one server to another in order to support filesystem migration and replication. For full protocol support, we need to add the ability to convert a DNS host name into an IP address that we can feed to the RPC client. We'll reuse the sunrpc cache, now that it has been converted to work with rpc_pipefs. Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> --- Documentation/filesystems/nfs.txt | 98 ++++++++++ Documentation/kernel-parameters.txt | 8 + fs/nfs/Makefile | 3 +- fs/nfs/cache_lib.c | 140 +++++++++++++++ fs/nfs/cache_lib.h | 27 +++ fs/nfs/dns_resolve.c | 335 +++++++++++++++++++++++++++++++++++ fs/nfs/dns_resolve.h | 14 ++ fs/nfs/inode.c | 8 + net/sunrpc/rpc_pipe.c | 7 + 9 files changed, 639 insertions(+), 1 deletions(-) create mode 100644 Documentation/filesystems/nfs.txt create mode 100644 fs/nfs/cache_lib.c create mode 100644 fs/nfs/cache_lib.h create mode 100644 fs/nfs/dns_resolve.c create mode 100644 fs/nfs/dns_resolve.h diff --git a/Documentation/filesystems/nfs.txt b/Documentation/filesystems/nfs.txt new file mode 100644 index 0000000..f50f26c --- /dev/null +++ b/Documentation/filesystems/nfs.txt @@ -0,0 +1,98 @@ + +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} + diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 2f18206..4d0ed96 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -1499,6 +1499,14 @@ and is between 256 and 4096 characters. It is defined in the file [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. diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile index 8451598..da7fda6 100644 --- a/fs/nfs/Makefile +++ b/fs/nfs/Makefile @@ -6,7 +6,8 @@ obj-$(CONFIG_NFS_FS) += nfs.o nfs-y := client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \ direct.o pagelist.o proc.o read.o symlink.o unlink.o \ - write.o namespace.o mount_clnt.o + write.o namespace.o mount_clnt.o \ + dns_resolve.o cache_lib.o nfs-$(CONFIG_ROOT_NFS) += nfsroot.o nfs-$(CONFIG_NFS_V3) += nfs3proc.o nfs3xdr.o nfs-$(CONFIG_NFS_V3_ACL) += nfs3acl.o diff --git a/fs/nfs/cache_lib.c b/fs/nfs/cache_lib.c new file mode 100644 index 0000000..b4ffd01 --- /dev/null +++ b/fs/nfs/cache_lib.c @@ -0,0 +1,140 @@ +/* + * linux/fs/nfs/cache_lib.c + * + * Helper routines for the NFS client caches + * + * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> + */ +#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(); +} + diff --git a/fs/nfs/cache_lib.h b/fs/nfs/cache_lib.h new file mode 100644 index 0000000..76f856e --- /dev/null +++ b/fs/nfs/cache_lib.h @@ -0,0 +1,27 @@ +/* + * Helper routines for the NFS client caches + * + * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> + */ + +#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); diff --git a/fs/nfs/dns_resolve.c b/fs/nfs/dns_resolve.c new file mode 100644 index 0000000..f4d54ba --- /dev/null +++ b/fs/nfs/dns_resolve.c @@ -0,0 +1,335 @@ +/* + * linux/fs/nfs/dns_resolve.c + * + * Copyright (c) 2009 Trond Myklebust <Trond.Myklebust@xxxxxxxxxx> + * + * 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); +} + diff --git a/fs/nfs/dns_resolve.h b/fs/nfs/dns_resolve.h new file mode 100644 index 0000000..a3f0938 --- /dev/null +++ b/fs/nfs/dns_resolve.h @@ -0,0 +1,14 @@ +/* + * 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 diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index fe5a8b4..060022b 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -46,6 +46,7 @@ #include "iostat.h" #include "internal.h" #include "fscache.h" +#include "dns_resolve.h" #define NFSDBG_FACILITY NFSDBG_VFS @@ -1506,6 +1507,10 @@ static int __init init_nfs_fs(void) { int err; + err = nfs_dns_resolver_init(); + if (err < 0) + goto out8; + err = nfs_fscache_register(); if (err < 0) goto out7; @@ -1564,6 +1569,8 @@ out5: out6: nfs_fscache_unregister(); out7: + nfs_dns_resolver_destroy(); +out8: return err; } @@ -1575,6 +1582,7 @@ static void __exit exit_nfs_fs(void) nfs_destroy_inodecache(); nfs_destroy_nfspagecache(); nfs_fscache_unregister(); + nfs_dns_resolver_destroy(); #ifdef CONFIG_PROC_FS rpc_proc_unregister("nfs"); #endif diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c index 3fdacaf..7f676bd 100644 --- a/net/sunrpc/rpc_pipe.c +++ b/net/sunrpc/rpc_pipe.c @@ -416,11 +416,13 @@ struct vfsmount *rpc_get_mount(void) 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) { @@ -946,6 +948,7 @@ enum { RPCAUTH_portmap, RPCAUTH_statd, RPCAUTH_nfsd4_cb, + RPCAUTH_cache, RPCAUTH_RootEOF }; @@ -974,6 +977,10 @@ static const struct rpc_filelist files[] = { .name = "nfsd4_cb", .mode = S_IFDIR | S_IRUGO | S_IXUGO, }, + [RPCAUTH_cache] = { + .name = "cache", + .mode = S_IFDIR | S_IRUGO | S_IXUGO, + }, }; static int -- 1.6.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
