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