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/dcache.h>
  11 #include <linux/gfp.h>
  12 #include <linux/mount.h>
  13 #include <linux/namei.h>
  14 #include <linux/nfs_fs.h>
  15 #include <linux/string.h>
  16 #include <linux/sunrpc/clnt.h>
  17 #include <linux/vfs.h>
  18 #include <linux/sunrpc/gss_api.h>
  19 #include "internal.h"
  20
  21 #define NFSDBG_FACILITY         NFSDBG_VFS
  22
  23 static void nfs_expire_automounts(struct work_struct *work);
  24
  25 static LIST_HEAD(nfs_automount_list);
  26 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
  27 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  28
  29 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
  30                                         struct nfs_fh *fh,
  31                                         struct nfs_fattr *fattr,
  32                                         rpc_authflavor_t authflavor);
  33
  34 /*
  35  * nfs_path - reconstruct the path given an arbitrary dentry
  36  * @base - used to return pointer to the end of devname part of path
  37  * @dentry - pointer to dentry
  38  * @buffer - result buffer
  39  * @buflen - length of buffer
  40  *
  41  * Helper function for constructing the server pathname
  42  * by arbitrary hashed dentry.
  43  *
  44  * This is mainly for use in figuring out the path on the
  45  * server side when automounting on top of an existing partition
  46  * and in generating /proc/mounts and friends.
  47  */
  48 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen)
  49 {
  50         char *end;
  51         int namelen;
  52         unsigned seq;
  53         const char *base;
  54
  55 rename_retry:
  56         end = buffer+buflen;
  57         *--end = '\0';
  58         buflen--;
  59
  60         seq = read_seqbegin(&rename_lock);
  61         rcu_read_lock();
  62         while (1) {
  63                 spin_lock(&dentry->d_lock);
  64                 if (IS_ROOT(dentry))
  65                         break;
  66                 namelen = dentry->d_name.len;
  67                 buflen -= namelen + 1;
  68                 if (buflen < 0)
  69                         goto Elong_unlock;
  70                 end -= namelen;
  71                 memcpy(end, dentry->d_name.name, namelen);
  72                 *--end = '/';
  73                 spin_unlock(&dentry->d_lock);
  74                 dentry = dentry->d_parent;
  75         }
  76         if (read_seqretry(&rename_lock, seq)) {
  77                 spin_unlock(&dentry->d_lock);
  78                 rcu_read_unlock();
  79                 goto rename_retry;
  80         }
  81         if (*end != '/') {
  82                 if (--buflen < 0) {
  83                         spin_unlock(&dentry->d_lock);
  84                         rcu_read_unlock();
  85                         goto Elong;
  86                 }
  87                 *--end = '/';
  88         }
  89         *p = end;
  90         base = dentry->d_fsdata;
  91         if (!base) {
  92                 spin_unlock(&dentry->d_lock);
  93                 rcu_read_unlock();
  94                 WARN_ON(1);
  95                 return end;
  96         }
  97         namelen = strlen(base);
  98         /* Strip off excess slashes in base string */
  99         while (namelen > 0 && base[namelen - 1] == '/')
 100                 namelen--;
 101         buflen -= namelen;
 102         if (buflen < 0) {
 103                 spin_unlock(&dentry->d_lock);
 104                 rcu_read_unlock();
 105                 goto Elong;
 106         }
 107         end -= namelen;
 108         memcpy(end, base, namelen);
 109         spin_unlock(&dentry->d_lock);
 110         rcu_read_unlock();
 111         return end;
 112 Elong_unlock:
 113         spin_unlock(&dentry->d_lock);
 114         rcu_read_unlock();
 115         if (read_seqretry(&rename_lock, seq))
 116                 goto rename_retry;
 117 Elong:
 118         return ERR_PTR(-ENAMETOOLONG);
 119 }
 120
 121 #ifdef CONFIG_NFS_V4
 122 rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
 123 {
 124         struct gss_api_mech *mech;
 125         struct xdr_netobj oid;
 126         int i;
 127         rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;
 128
 129         for (i = 0; i < flavors->num_flavors; i++) {
 130                 struct nfs4_secinfo_flavor *flavor;
 131                 flavor = &flavors->flavors[i];
 132
 133                 if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
 134                         pseudoflavor = flavor->flavor;
 135                         break;
 136                 } else if (flavor->flavor == RPC_AUTH_GSS) {
 137                         oid.len  = flavor->gss.sec_oid4.len;
 138                         oid.data = flavor->gss.sec_oid4.data;
 139                         mech = gss_mech_get_by_OID(&oid);
 140                         if (!mech)
 141                                 continue;
 142                         pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
 143                         gss_mech_put(mech);
 144                         break;
 145                 }
 146         }
 147
 148         return pseudoflavor;
 149 }
 150
 151 static struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
 152                                               struct qstr *name,
 153                                               struct nfs_fh *fh,
 154                                               struct nfs_fattr *fattr)
 155 {
 156         int err;
 157
 158         if (NFS_PROTO(dir)->version == 4)
 159                 return nfs4_proc_lookup_mountpoint(dir, name, fh, fattr);
 160
 161         err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
 162         if (err)
 163                 return ERR_PTR(err);
 164         return rpc_clone_client(NFS_SERVER(dir)->client);
 165 }
 166 #else /* CONFIG_NFS_V4 */
 167 static inline struct rpc_clnt *nfs_lookup_mountpoint(struct inode *dir,
 168                                                      struct qstr *name,
 169                                                      struct nfs_fh *fh,
 170                                                      struct nfs_fattr *fattr)
 171 {
 172         int err = NFS_PROTO(dir)->lookup(NFS_SERVER(dir)->client, dir, name, fh, fattr);
 173         if (err)
 174                 return ERR_PTR(err);
 175         return rpc_clone_client(NFS_SERVER(dir)->client);
 176 }
 177 #endif /* CONFIG_NFS_V4 */
 178
 179 /*
 180  * nfs_d_automount - Handle crossing a mountpoint on the server
 181  * @path - The mountpoint
 182  *
 183  * When we encounter a mountpoint on the server, we want to set up
 184  * a mountpoint on the client too, to prevent inode numbers from
 185  * colliding, and to allow "df" to work properly.
 186  * On NFSv4, we also want to allow for the fact that different
 187  * filesystems may be migrated to different servers in a failover
 188  * situation, and that different filesystems may want to use
 189  * different security flavours.
 190  */
 191 struct vfsmount *nfs_d_automount(struct path *path)
 192 {
 193         struct vfsmount *mnt;
 194         struct dentry *parent;
 195         struct nfs_fh *fh = NULL;
 196         struct nfs_fattr *fattr = NULL;
 197         struct rpc_clnt *client;
 198
 199         dprintk("--> nfs_d_automount()\n");
 200
 201         mnt = ERR_PTR(-ESTALE);
 202         if (IS_ROOT(path->dentry))
 203                 goto out_nofree;
 204
 205         mnt = ERR_PTR(-ENOMEM);
 206         fh = nfs_alloc_fhandle();
 207         fattr = nfs_alloc_fattr();
 208         if (fh == NULL || fattr == NULL)
 209                 goto out;
 210
 211         dprintk("%s: enter\n", __func__);
 212
 213         /* Look it up again to get its attributes */
 214         parent = dget_parent(path->dentry);
 215         client = nfs_lookup_mountpoint(parent->d_inode, &path->dentry->d_name, fh, fattr);
 216         dput(parent);
 217         if (IS_ERR(client)) {
 218                 mnt = ERR_CAST(client);
 219                 goto out;
 220         }
 221
 222         if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
 223                 mnt = nfs_do_refmount(client, path->dentry);
 224         else
 225                 mnt = nfs_do_submount(path->dentry, fh, fattr, client->cl_auth->au_flavor);
 226         rpc_shutdown_client(client);
 227
 228         if (IS_ERR(mnt))
 229                 goto out;
 230
 231         dprintk("%s: done, success\n", __func__);
 232         mntget(mnt); /* prevent immediate expiration */
 233         mnt_set_expiry(mnt, &nfs_automount_list);
 234         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 235
 236 out:
 237         nfs_free_fattr(fattr);
 238         nfs_free_fhandle(fh);
 239 out_nofree:
 240         if (IS_ERR(mnt))
 241                 dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
 242         else
 243                 dprintk("<-- %s() = %p\n", __func__, mnt);
 244         return mnt;
 245 }
 246
 247 const struct inode_operations nfs_mountpoint_inode_operations = {
 248         .getattr        = nfs_getattr,
 249 };
 250
 251 const struct inode_operations nfs_referral_inode_operations = {
 252 };
 253
 254 static void nfs_expire_automounts(struct work_struct *work)
 255 {
 256         struct list_head *list = &nfs_automount_list;
 257
 258         mark_mounts_for_expiry(list);
 259         if (!list_empty(list))
 260                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 261 }
 262
 263 void nfs_release_automount_timer(void)
 264 {
 265         if (list_empty(&nfs_automount_list))
 266                 cancel_delayed_work(&nfs_automount_task);
 267 }
 268
 269 /*
 270  * Clone a mountpoint of the appropriate type
 271  */
 272 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 273                                            const char *devname,
 274                                            struct nfs_clone_mount *mountdata)
 275 {
 276 #ifdef CONFIG_NFS_V4
 277         struct vfsmount *mnt = ERR_PTR(-EINVAL);
 278         switch (server->nfs_client->rpc_ops->version) {
 279                 case 2:
 280                 case 3:
 281                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 282                         break;
 283                 case 4:
 284                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 285         }
 286         return mnt;
 287 #else
 288         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 289 #endif
 290 }
 291
 292 /**
 293  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 294  * @dentry - parent directory
 295  * @fh - filehandle for new root dentry
 296  * @fattr - attributes for new root inode
 297  * @authflavor - security flavor to use when performing the mount
 298  *
 299  */
 300 static struct vfsmount *nfs_do_submount(struct dentry *dentry,
 301                                         struct nfs_fh *fh,
 302                                         struct nfs_fattr *fattr,
 303                                         rpc_authflavor_t authflavor)
 304 {
 305         struct nfs_clone_mount mountdata = {
 306                 .sb = dentry->d_sb,
 307                 .dentry = dentry,
 308                 .fh = fh,
 309                 .fattr = fattr,
 310                 .authflavor = authflavor,
 311         };
 312         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 313         char *page = (char *) __get_free_page(GFP_USER);
 314         char *devname;
 315
 316         dprintk("--> nfs_do_submount()\n");
 317
 318         dprintk("%s: submounting on %s/%s\n", __func__,
 319                         dentry->d_parent->d_name.name,
 320                         dentry->d_name.name);
 321         if (page == NULL)
 322                 goto out;
 323         devname = nfs_devname(dentry, page, PAGE_SIZE);
 324         mnt = (struct vfsmount *)devname;
 325         if (IS_ERR(devname))
 326                 goto free_page;
 327         mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 328 free_page:
 329         free_page((unsigned long)page);
 330 out:
 331         dprintk("%s: done\n", __func__);
 332
 333         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 334         return mnt;
 335 }