linux/fs/nfs/namespace.c
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   1/*
   2 * linux/fs/nfs/namespace.c
   3 *
   4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   5 * - Modified by David Howells <dhowells@redhat.com>
   6 *
   7 * NFS namespace
   8 */
   9
  10#include <linux/module.h>
  11#include <linux/dcache.h>
  12#include <linux/gfp.h>
  13#include <linux/mount.h>
  14#include <linux/namei.h>
  15#include <linux/nfs_fs.h>
  16#include <linux/string.h>
  17#include <linux/sunrpc/clnt.h>
  18#include <linux/vfs.h>
  19#include <linux/sunrpc/gss_api.h>
  20#include "internal.h"
  21
  22#define NFSDBG_FACILITY         NFSDBG_VFS
  23
  24static void nfs_expire_automounts(struct work_struct *work);
  25
  26static LIST_HEAD(nfs_automount_list);
  27static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  28int nfs_mountpoint_expiry_timeout = 500 * HZ;
  29
  30/*
  31 * nfs_path - reconstruct the path given an arbitrary dentry
  32 * @base - used to return pointer to the end of devname part of path
  33 * @dentry - pointer to dentry
  34 * @buffer - result buffer
  35 * @buflen - length of buffer
  36 * @flags - options (see below)
  37 *
  38 * Helper function for constructing the server pathname
  39 * by arbitrary hashed dentry.
  40 *
  41 * This is mainly for use in figuring out the path on the
  42 * server side when automounting on top of an existing partition
  43 * and in generating /proc/mounts and friends.
  44 *
  45 * Supported flags:
  46 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
  47 *                     the original device (export) name
  48 *                     (if unset, the original name is returned verbatim)
  49 */
  50char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
  51               unsigned flags)
  52{
  53        char *end;
  54        int namelen;
  55        unsigned seq;
  56        const char *base;
  57
  58rename_retry:
  59        end = buffer+buflen;
  60        *--end = '\0';
  61        buflen--;
  62
  63        seq = read_seqbegin(&rename_lock);
  64        rcu_read_lock();
  65        while (1) {
  66                spin_lock(&dentry->d_lock);
  67                if (IS_ROOT(dentry))
  68                        break;
  69                namelen = dentry->d_name.len;
  70                buflen -= namelen + 1;
  71                if (buflen < 0)
  72                        goto Elong_unlock;
  73                end -= namelen;
  74                memcpy(end, dentry->d_name.name, namelen);
  75                *--end = '/';
  76                spin_unlock(&dentry->d_lock);
  77                dentry = dentry->d_parent;
  78        }
  79        if (read_seqretry(&rename_lock, seq)) {
  80                spin_unlock(&dentry->d_lock);
  81                rcu_read_unlock();
  82                goto rename_retry;
  83        }
  84        if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
  85                if (--buflen < 0) {
  86                        spin_unlock(&dentry->d_lock);
  87                        rcu_read_unlock();
  88                        goto Elong;
  89                }
  90                *--end = '/';
  91        }
  92        *p = end;
  93        base = dentry->d_fsdata;
  94        if (!base) {
  95                spin_unlock(&dentry->d_lock);
  96                rcu_read_unlock();
  97                WARN_ON(1);
  98                return end;
  99        }
 100        namelen = strlen(base);
 101        if (flags & NFS_PATH_CANONICAL) {
 102                /* Strip off excess slashes in base string */
 103                while (namelen > 0 && base[namelen - 1] == '/')
 104                        namelen--;
 105        }
 106        buflen -= namelen;
 107        if (buflen < 0) {
 108                spin_unlock(&dentry->d_lock);
 109                rcu_read_unlock();
 110                goto Elong;
 111        }
 112        end -= namelen;
 113        memcpy(end, base, namelen);
 114        spin_unlock(&dentry->d_lock);
 115        rcu_read_unlock();
 116        return end;
 117Elong_unlock:
 118        spin_unlock(&dentry->d_lock);
 119        rcu_read_unlock();
 120        if (read_seqretry(&rename_lock, seq))
 121                goto rename_retry;
 122Elong:
 123        return ERR_PTR(-ENAMETOOLONG);
 124}
 125EXPORT_SYMBOL_GPL(nfs_path);
 126
 127/*
 128 * nfs_d_automount - Handle crossing a mountpoint on the server
 129 * @path - The mountpoint
 130 *
 131 * When we encounter a mountpoint on the server, we want to set up
 132 * a mountpoint on the client too, to prevent inode numbers from
 133 * colliding, and to allow "df" to work properly.
 134 * On NFSv4, we also want to allow for the fact that different
 135 * filesystems may be migrated to different servers in a failover
 136 * situation, and that different filesystems may want to use
 137 * different security flavours.
 138 */
 139struct vfsmount *nfs_d_automount(struct path *path)
 140{
 141        struct vfsmount *mnt;
 142        struct nfs_server *server = NFS_SERVER(path->dentry->d_inode);
 143        struct nfs_fh *fh = NULL;
 144        struct nfs_fattr *fattr = NULL;
 145
 146        dprintk("--> nfs_d_automount()\n");
 147
 148        mnt = ERR_PTR(-ESTALE);
 149        if (IS_ROOT(path->dentry))
 150                goto out_nofree;
 151
 152        mnt = ERR_PTR(-ENOMEM);
 153        fh = nfs_alloc_fhandle();
 154        fattr = nfs_alloc_fattr();
 155        if (fh == NULL || fattr == NULL)
 156                goto out;
 157
 158        dprintk("%s: enter\n", __func__);
 159
 160        mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
 161        if (IS_ERR(mnt))
 162                goto out;
 163
 164        dprintk("%s: done, success\n", __func__);
 165        mntget(mnt); /* prevent immediate expiration */
 166        mnt_set_expiry(mnt, &nfs_automount_list);
 167        schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 168
 169out:
 170        nfs_free_fattr(fattr);
 171        nfs_free_fhandle(fh);
 172out_nofree:
 173        if (IS_ERR(mnt))
 174                dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
 175        else
 176                dprintk("<-- %s() = %p\n", __func__, mnt);
 177        return mnt;
 178}
 179
 180const struct inode_operations nfs_mountpoint_inode_operations = {
 181        .getattr        = nfs_getattr,
 182};
 183
 184const struct inode_operations nfs_referral_inode_operations = {
 185};
 186
 187static void nfs_expire_automounts(struct work_struct *work)
 188{
 189        struct list_head *list = &nfs_automount_list;
 190
 191        mark_mounts_for_expiry(list);
 192        if (!list_empty(list))
 193                schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 194}
 195
 196void nfs_release_automount_timer(void)
 197{
 198        if (list_empty(&nfs_automount_list))
 199                cancel_delayed_work(&nfs_automount_task);
 200}
 201
 202/*
 203 * Clone a mountpoint of the appropriate type
 204 */
 205static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 206                                           const char *devname,
 207                                           struct nfs_clone_mount *mountdata)
 208{
 209        return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 210}
 211
 212/**
 213 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 214 * @dentry - parent directory
 215 * @fh - filehandle for new root dentry
 216 * @fattr - attributes for new root inode
 217 * @authflavor - security flavor to use when performing the mount
 218 *
 219 */
 220struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
 221                                 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
 222{
 223        struct nfs_clone_mount mountdata = {
 224                .sb = dentry->d_sb,
 225                .dentry = dentry,
 226                .fh = fh,
 227                .fattr = fattr,
 228                .authflavor = authflavor,
 229        };
 230        struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 231        char *page = (char *) __get_free_page(GFP_USER);
 232        char *devname;
 233
 234        dprintk("--> nfs_do_submount()\n");
 235
 236        dprintk("%s: submounting on %s/%s\n", __func__,
 237                        dentry->d_parent->d_name.name,
 238                        dentry->d_name.name);
 239        if (page == NULL)
 240                goto out;
 241        devname = nfs_devname(dentry, page, PAGE_SIZE);
 242        mnt = (struct vfsmount *)devname;
 243        if (IS_ERR(devname))
 244                goto free_page;
 245        mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 246free_page:
 247        free_page((unsigned long)page);
 248out:
 249        dprintk("%s: done\n", __func__);
 250
 251        dprintk("<-- nfs_do_submount() = %p\n", mnt);
 252        return mnt;
 253}
 254EXPORT_SYMBOL_GPL(nfs_do_submount);
 255
 256struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
 257                              struct nfs_fh *fh, struct nfs_fattr *fattr)
 258{
 259        int err;
 260        struct dentry *parent = dget_parent(dentry);
 261
 262        /* Look it up again to get its attributes */
 263        err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr);
 264        dput(parent);
 265        if (err != 0)
 266                return ERR_PTR(err);
 267
 268        return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
 269}
 270EXPORT_SYMBOL_GPL(nfs_submount);
 271
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