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