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/mount.h>
  12 #include <linux/namei.h>
  13 #include <linux/nfs_fs.h>
  14 #include <linux/string.h>
  15 #include <linux/sunrpc/clnt.h>
  16 #include <linux/vfs.h>
  17 #include "internal.h"
  18
  19 #define NFSDBG_FACILITY         NFSDBG_VFS
  20
  21 static void nfs_expire_automounts(void *list);
  22
  23 LIST_HEAD(nfs_automount_list);
  24 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts,
  25                             &nfs_automount_list);
  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 = buffer+buflen;
  53         int namelen;
  54
  55         *--end = '\0';
  56         buflen--;
  57         spin_lock(&dcache_lock);
  58         while (!IS_ROOT(dentry) && dentry != droot) {
  59                 namelen = dentry->d_name.len;
  60                 buflen -= namelen + 1;
  61                 if (buflen < 0)
  62                         goto Elong_unlock;
  63                 end -= namelen;
  64                 memcpy(end, dentry->d_name.name, namelen);
  65                 *--end = '/';
  66                 dentry = dentry->d_parent;
  67         }
  68         spin_unlock(&dcache_lock);
  69         namelen = strlen(base);
  70         /* Strip off excess slashes in base string */
  71         while (namelen > 0 && base[namelen - 1] == '/')
  72                 namelen--;
  73         buflen -= namelen;
  74         if (buflen < 0)
  75                 goto Elong;
  76         end -= namelen;
  77         memcpy(end, base, namelen);
  78         return end;
  79 Elong_unlock:
  80         spin_unlock(&dcache_lock);
  81 Elong:
  82         return ERR_PTR(-ENAMETOOLONG);
  83 }
  84
  85 /*
  86  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  87  * @dentry - dentry of mountpoint
  88  * @nd - nameidata info
  89  *
  90  * When we encounter a mountpoint on the server, we want to set up
  91  * a mountpoint on the client too, to prevent inode numbers from
  92  * colliding, and to allow "df" to work properly.
  93  * On NFSv4, we also want to allow for the fact that different
  94  * filesystems may be migrated to different servers in a failover
  95  * situation, and that different filesystems may want to use
  96  * different security flavours.
  97  */
  98 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
  99 {
 100         struct vfsmount *mnt;
 101         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
 102         struct dentry *parent;
 103         struct nfs_fh fh;
 104         struct nfs_fattr fattr;
 105         int err;
 106
 107         dprintk("--> nfs_follow_mountpoint()\n");
 108
 109         BUG_ON(IS_ROOT(dentry));
 110         dprintk("%s: enter\n", __FUNCTION__);
 111         dput(nd->dentry);
 112         nd->dentry = dget(dentry);
 113
 114         /* Look it up again */
 115         parent = dget_parent(nd->dentry);
 116         err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
 117                                                   &nd->dentry->d_name,
 118                                                   &fh, &fattr);
 119         dput(parent);
 120         if (err != 0)
 121                 goto out_err;
 122
 123         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
 124                 mnt = nfs_do_refmount(nd->mnt, nd->dentry);
 125         else
 126                 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
 127         err = PTR_ERR(mnt);
 128         if (IS_ERR(mnt))
 129                 goto out_err;
 130
 131         mntget(mnt);
 132         err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
 133         if (err < 0) {
 134                 mntput(mnt);
 135                 if (err == -EBUSY)
 136                         goto out_follow;
 137                 goto out_err;
 138         }
 139         mntput(nd->mnt);
 140         dput(nd->dentry);
 141         nd->mnt = mnt;
 142         nd->dentry = dget(mnt->mnt_root);
 143         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 144 out:
 145         dprintk("%s: done, returned %d\n", __FUNCTION__, err);
 146
 147         dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
 148         return ERR_PTR(err);
 149 out_err:
 150         path_release(nd);
 151         goto out;
 152 out_follow:
 153         while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
 154                 ;
 155         err = 0;
 156         goto out;
 157 }
 158
 159 struct inode_operations nfs_mountpoint_inode_operations = {
 160         .follow_link    = nfs_follow_mountpoint,
 161         .getattr        = nfs_getattr,
 162 };
 163
 164 struct inode_operations nfs_referral_inode_operations = {
 165         .follow_link    = nfs_follow_mountpoint,
 166 };
 167
 168 static void nfs_expire_automounts(void *data)
 169 {
 170         struct list_head *list = (struct list_head *)data;
 171
 172         mark_mounts_for_expiry(list);
 173         if (!list_empty(list))
 174                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 175 }
 176
 177 void nfs_release_automount_timer(void)
 178 {
 179         if (list_empty(&nfs_automount_list)) {
 180                 cancel_delayed_work(&nfs_automount_task);
 181                 flush_scheduled_work();
 182         }
 183 }
 184
 185 /*
 186  * Clone a mountpoint of the appropriate type
 187  */
 188 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 189                                            const char *devname,
 190                                            struct nfs_clone_mount *mountdata)
 191 {
 192 #ifdef CONFIG_NFS_V4
 193         struct vfsmount *mnt = NULL;
 194         switch (server->nfs_client->cl_nfsversion) {
 195                 case 2:
 196                 case 3:
 197                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 198                         break;
 199                 case 4:
 200                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 201         }
 202         return mnt;
 203 #else
 204         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 205 #endif
 206 }
 207
 208 /**
 209  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 210  * @mnt_parent - mountpoint of parent directory
 211  * @dentry - parent directory
 212  * @fh - filehandle for new root dentry
 213  * @fattr - attributes for new root inode
 214  *
 215  */
 216 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 217                                         const struct dentry *dentry,
 218                                         struct nfs_fh *fh,
 219                                         struct nfs_fattr *fattr)
 220 {
 221         struct nfs_clone_mount mountdata = {
 222                 .sb = mnt_parent->mnt_sb,
 223                 .dentry = dentry,
 224                 .fh = fh,
 225                 .fattr = fattr,
 226         };
 227         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 228         char *page = (char *) __get_free_page(GFP_USER);
 229         char *devname;
 230
 231         dprintk("--> nfs_do_submount()\n");
 232
 233         dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
 234                         dentry->d_parent->d_name.name,
 235                         dentry->d_name.name);
 236         if (page == NULL)
 237                 goto out;
 238         devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
 239         mnt = (struct vfsmount *)devname;
 240         if (IS_ERR(devname))
 241                 goto free_page;
 242         mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
 243 free_page:
 244         free_page((unsigned long)page);
 245 out:
 246         dprintk("%s: done\n", __FUNCTION__);
 247
 248         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 249         return mnt;
 250 }