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