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