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 (*end == '/') {
 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(d_inode(path->dentry));
 143         struct nfs_fh *fh = NULL;
 144         struct nfs_fattr *fattr = NULL;
 145
 146         if (IS_ROOT(path->dentry))
 147                 return ERR_PTR(-ESTALE);
 148
 149         mnt = ERR_PTR(-ENOMEM);
 150         fh = nfs_alloc_fhandle();
 151         fattr = nfs_alloc_fattr();
 152         if (fh == NULL || fattr == NULL)
 153                 goto out;
 154
 155         mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
 156         if (IS_ERR(mnt))
 157                 goto out;
 158
 159         mntget(mnt); /* prevent immediate expiration */
 160         mnt_set_expiry(mnt, &nfs_automount_list);
 161         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 162
 163 out:
 164         nfs_free_fattr(fattr);
 165         nfs_free_fhandle(fh);
 166         return mnt;
 167 }
 168
 169 static int
 170 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
 171                         u32 request_mask, unsigned int query_flags)
 172 {
 173         if (NFS_FH(d_inode(path->dentry))->size != 0)
 174                 return nfs_getattr(path, stat, request_mask, query_flags);
 175         generic_fillattr(d_inode(path->dentry), stat);
 176         return 0;
 177 }
 178
 179 static int
 180 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
 181 {
 182         if (NFS_FH(d_inode(dentry))->size != 0)
 183                 return nfs_setattr(dentry, attr);
 184         return -EACCES;
 185 }
 186
 187 const struct inode_operations nfs_mountpoint_inode_operations = {
 188         .getattr        = nfs_getattr,
 189         .setattr        = nfs_setattr,
 190 };
 191
 192 const struct inode_operations nfs_referral_inode_operations = {
 193         .getattr        = nfs_namespace_getattr,
 194         .setattr        = nfs_namespace_setattr,
 195 };
 196
 197 static void nfs_expire_automounts(struct work_struct *work)
 198 {
 199         struct list_head *list = &nfs_automount_list;
 200
 201         mark_mounts_for_expiry(list);
 202         if (!list_empty(list))
 203                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 204 }
 205
 206 void nfs_release_automount_timer(void)
 207 {
 208         if (list_empty(&nfs_automount_list))
 209                 cancel_delayed_work(&nfs_automount_task);
 210 }
 211
 212 /*
 213  * Clone a mountpoint of the appropriate type
 214  */
 215 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 216                                            const char *devname,
 217                                            struct nfs_clone_mount *mountdata)
 218 {
 219         return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
 220 }
 221
 222 /**
 223  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 224  * @dentry - parent directory
 225  * @fh - filehandle for new root dentry
 226  * @fattr - attributes for new root inode
 227  * @authflavor - security flavor to use when performing the mount
 228  *
 229  */
 230 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
 231                                  struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
 232 {
 233         struct nfs_clone_mount mountdata = {
 234                 .sb = dentry->d_sb,
 235                 .dentry = dentry,
 236                 .fh = fh,
 237                 .fattr = fattr,
 238                 .authflavor = authflavor,
 239         };
 240         struct vfsmount *mnt;
 241         char *page = (char *) __get_free_page(GFP_USER);
 242         char *devname;
 243
 244         if (page == NULL)
 245                 return ERR_PTR(-ENOMEM);
 246
 247         devname = nfs_devname(dentry, page, PAGE_SIZE);
 248         if (IS_ERR(devname))
 249                 mnt = ERR_CAST(devname);
 250         else
 251                 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 252
 253         free_page((unsigned long)page);
 254         return mnt;
 255 }
 256 EXPORT_SYMBOL_GPL(nfs_do_submount);
 257
 258 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
 259                               struct nfs_fh *fh, struct nfs_fattr *fattr)
 260 {
 261         int err;
 262         struct dentry *parent = dget_parent(dentry);
 263
 264         /* Look it up again to get its attributes */
 265         err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
 266         dput(parent);
 267         if (err != 0)
 268                 return ERR_PTR(err);
 269
 270         return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
 271 }
 272 EXPORT_SYMBOL_GPL(nfs_submount);