fs/nfs/namespace.c

   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
  24 static void nfs_expire_automounts(struct work_struct *work);
  25
  26 static LIST_HEAD(nfs_automount_list);
  27 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  28 int 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  */
  50 char *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
  58 rename_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;
 117 Elong_unlock:
 118         spin_unlock(&dentry->d_lock);
 119         rcu_read_unlock();
 120         if (read_seqretry(&rename_lock, seq))
 121                 goto rename_retry;
 122 Elong:
 123         return ERR_PTR(-ENAMETOOLONG);
 124 }
 125 EXPORT_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  */
 139 struct 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
 169 out:
 170         nfs_free_fattr(fattr);
 171         nfs_free_fhandle(fh);
 172 out_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
 180 static int
 181 nfs_namespace_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
 182 {
 183         if (NFS_FH(dentry->d_inode)->size != 0)
 184                 return nfs_getattr(mnt, dentry, stat);
 185         generic_fillattr(dentry->d_inode, stat);
 186         return 0;
 187 }
 188
 189 static int
 190 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
 191 {
 192         if (NFS_FH(dentry->d_inode)->size != 0)
 193                 return nfs_setattr(dentry, attr);
 194         return -EACCES;
 195 }
 196
 197 const struct inode_operations nfs_mountpoint_inode_operations = {
 198         .getattr        = nfs_getattr,
 199         .setattr        = nfs_setattr,
 200 };
 201
 202 const struct inode_operations nfs_referral_inode_operations = {
 203         .getattr        = nfs_namespace_getattr,
 204         .setattr        = nfs_namespace_setattr,
 205 };
 206
 207 static void nfs_expire_automounts(struct work_struct *work)
 208 {
 209         struct list_head *list = &nfs_automount_list;
 210
 211         mark_mounts_for_expiry(list);
 212         if (!list_empty(list))
 213                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 214 }
 215
 216 void nfs_release_automount_timer(void)
 217 {
 218         if (list_empty(&nfs_automount_list))
 219                 cancel_delayed_work(&nfs_automount_task);
 220 }
 221
 222 /*
 223  * Clone a mountpoint of the appropriate type
 224  */
 225 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 226                                            const char *devname,
 227                                            struct nfs_clone_mount *mountdata)
 228 {
 229         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 230 }
 231
 232 /**
 233  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 234  * @dentry - parent directory
 235  * @fh - filehandle for new root dentry
 236  * @fattr - attributes for new root inode
 237  * @authflavor - security flavor to use when performing the mount
 238  *
 239  */
 240 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
 241                                  struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
 242 {
 243         struct nfs_clone_mount mountdata = {
 244                 .sb = dentry->d_sb,
 245                 .dentry = dentry,
 246                 .fh = fh,
 247                 .fattr = fattr,
 248                 .authflavor = authflavor,
 249         };
 250         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 251         char *page = (char *) __get_free_page(GFP_USER);
 252         char *devname;
 253
 254         dprintk("--> nfs_do_submount()\n");
 255
 256         dprintk("%s: submounting on %s/%s\n", __func__,
 257                         dentry->d_parent->d_name.name,
 258                         dentry->d_name.name);
 259         if (page == NULL)
 260                 goto out;
 261         devname = nfs_devname(dentry, page, PAGE_SIZE);
 262         mnt = (struct vfsmount *)devname;
 263         if (IS_ERR(devname))
 264                 goto free_page;
 265         mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 266 free_page:
 267         free_page((unsigned long)page);
 268 out:
 269         dprintk("%s: done\n", __func__);
 270
 271         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 272         return mnt;
 273 }
 274 EXPORT_SYMBOL_GPL(nfs_do_submount);
 275
 276 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
 277                               struct nfs_fh *fh, struct nfs_fattr *fattr)
 278 {
 279         int err;
 280         struct dentry *parent = dget_parent(dentry);
 281
 282         /* Look it up again to get its attributes */
 283         err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr);
 284         dput(parent);
 285         if (err != 0)
 286                 return ERR_PTR(err);
 287
 288         return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
 289 }
 290 EXPORT_SYMBOL_GPL(nfs_submount);