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_in - pointer to dentry
  34  * @buffer - result buffer
  35  * @buflen_in - 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_in, char *buffer,
  51                ssize_t buflen_in, unsigned flags)
  52 {
  53         char *end;
  54         int namelen;
  55         unsigned seq;
  56         const char *base;
  57         struct dentry *dentry;
  58         ssize_t buflen;
  59
  60 rename_retry:
  61         buflen = buflen_in;
  62         dentry = dentry_in;
  63         end = buffer+buflen;
  64         *--end = '\0';
  65         buflen--;
  66
  67         seq = read_seqbegin(&rename_lock);
  68         rcu_read_lock();
  69         while (1) {
  70                 spin_lock(&dentry->d_lock);
  71                 if (IS_ROOT(dentry))
  72                         break;
  73                 namelen = dentry->d_name.len;
  74                 buflen -= namelen + 1;
  75                 if (buflen < 0)
  76                         goto Elong_unlock;
  77                 end -= namelen;
  78                 memcpy(end, dentry->d_name.name, namelen);
  79                 *--end = '/';
  80                 spin_unlock(&dentry->d_lock);
  81                 dentry = dentry->d_parent;
  82         }
  83         if (read_seqretry(&rename_lock, seq)) {
  84                 spin_unlock(&dentry->d_lock);
  85                 rcu_read_unlock();
  86                 goto rename_retry;
  87         }
  88         if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
  89                 if (--buflen < 0) {
  90                         spin_unlock(&dentry->d_lock);
  91                         rcu_read_unlock();
  92                         goto Elong;
  93                 }
  94                 *--end = '/';
  95         }
  96         *p = end;
  97         base = dentry->d_fsdata;
  98         if (!base) {
  99                 spin_unlock(&dentry->d_lock);
 100                 rcu_read_unlock();
 101                 WARN_ON(1);
 102                 return end;
 103         }
 104         namelen = strlen(base);
 105         if (*end == '/') {
 106                 /* Strip off excess slashes in base string */
 107                 while (namelen > 0 && base[namelen - 1] == '/')
 108                         namelen--;
 109         }
 110         buflen -= namelen;
 111         if (buflen < 0) {
 112                 spin_unlock(&dentry->d_lock);
 113                 rcu_read_unlock();
 114                 goto Elong;
 115         }
 116         end -= namelen;
 117         memcpy(end, base, namelen);
 118         spin_unlock(&dentry->d_lock);
 119         rcu_read_unlock();
 120         return end;
 121 Elong_unlock:
 122         spin_unlock(&dentry->d_lock);
 123         rcu_read_unlock();
 124         if (read_seqretry(&rename_lock, seq))
 125                 goto rename_retry;
 126 Elong:
 127         return ERR_PTR(-ENAMETOOLONG);
 128 }
 129 EXPORT_SYMBOL_GPL(nfs_path);
 130
 131 /*
 132  * nfs_d_automount - Handle crossing a mountpoint on the server
 133  * @path - The mountpoint
 134  *
 135  * When we encounter a mountpoint on the server, we want to set up
 136  * a mountpoint on the client too, to prevent inode numbers from
 137  * colliding, and to allow "df" to work properly.
 138  * On NFSv4, we also want to allow for the fact that different
 139  * filesystems may be migrated to different servers in a failover
 140  * situation, and that different filesystems may want to use
 141  * different security flavours.
 142  */
 143 struct vfsmount *nfs_d_automount(struct path *path)
 144 {
 145         struct vfsmount *mnt;
 146         struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
 147         struct nfs_fh *fh = NULL;
 148         struct nfs_fattr *fattr = NULL;
 149
 150         if (IS_ROOT(path->dentry))
 151                 return ERR_PTR(-ESTALE);
 152
 153         mnt = ERR_PTR(-ENOMEM);
 154         fh = nfs_alloc_fhandle();
 155         fattr = nfs_alloc_fattr();
 156         if (fh == NULL || fattr == NULL)
 157                 goto out;
 158
 159         mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
 160         if (IS_ERR(mnt))
 161                 goto out;
 162
 163         mntget(mnt); /* prevent immediate expiration */
 164         mnt_set_expiry(mnt, &nfs_automount_list);
 165         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 166
 167 out:
 168         nfs_free_fattr(fattr);
 169         nfs_free_fhandle(fh);
 170         return mnt;
 171 }
 172
 173 static int
 174 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
 175                         u32 request_mask, unsigned int query_flags)
 176 {
 177         if (NFS_FH(d_inode(path->dentry))->size != 0)
 178                 return nfs_getattr(path, stat, request_mask, query_flags);
 179         generic_fillattr(d_inode(path->dentry), stat);
 180         return 0;
 181 }
 182
 183 static int
 184 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
 185 {
 186         if (NFS_FH(d_inode(dentry))->size != 0)
 187                 return nfs_setattr(dentry, attr);
 188         return -EACCES;
 189 }
 190
 191 const struct inode_operations nfs_mountpoint_inode_operations = {
 192         .getattr        = nfs_getattr,
 193         .setattr        = nfs_setattr,
 194 };
 195
 196 const struct inode_operations nfs_referral_inode_operations = {
 197         .getattr        = nfs_namespace_getattr,
 198         .setattr        = nfs_namespace_setattr,
 199 };
 200
 201 static void nfs_expire_automounts(struct work_struct *work)
 202 {
 203         struct list_head *list = &nfs_automount_list;
 204
 205         mark_mounts_for_expiry(list);
 206         if (!list_empty(list))
 207                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 208 }
 209
 210 void nfs_release_automount_timer(void)
 211 {
 212         if (list_empty(&nfs_automount_list))
 213                 cancel_delayed_work(&nfs_automount_task);
 214 }
 215
 216 /*
 217  * Clone a mountpoint of the appropriate type
 218  */
 219 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 220                                            const char *devname,
 221                                            struct nfs_clone_mount *mountdata)
 222 {
 223         return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata);
 224 }
 225
 226 /**
 227  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 228  * @dentry - parent directory
 229  * @fh - filehandle for new root dentry
 230  * @fattr - attributes for new root inode
 231  * @authflavor - security flavor to use when performing the mount
 232  *
 233  */
 234 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
 235                                  struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
 236 {
 237         struct nfs_clone_mount mountdata = {
 238                 .sb = dentry->d_sb,
 239                 .dentry = dentry,
 240                 .fh = fh,
 241                 .fattr = fattr,
 242                 .authflavor = authflavor,
 243         };
 244         struct vfsmount *mnt;
 245         char *page = (char *) __get_free_page(GFP_USER);
 246         char *devname;
 247
 248         if (page == NULL)
 249                 return ERR_PTR(-ENOMEM);
 250
 251         devname = nfs_devname(dentry, page, PAGE_SIZE);
 252         if (IS_ERR(devname))
 253                 mnt = ERR_CAST(devname);
 254         else
 255                 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
 256
 257         free_page((unsigned long)page);
 258         return mnt;
 259 }
 260 EXPORT_SYMBOL_GPL(nfs_do_submount);
 261
 262 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
 263                               struct nfs_fh *fh, struct nfs_fattr *fattr)
 264 {
 265         int err;
 266         struct dentry *parent = dget_parent(dentry);
 267
 268         /* Look it up again to get its attributes */
 269         err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
 270         dput(parent);
 271         if (err != 0)
 272                 return ERR_PTR(err);
 273
 274         return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
 275 }
 276 EXPORT_SYMBOL_GPL(nfs_submount);