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/config.h>
  11
  12 #include <linux/dcache.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 "internal.h"
  20
  21 #define NFSDBG_FACILITY         NFSDBG_VFS
  22
  23 static void nfs_expire_automounts(void *list);
  24
  25 LIST_HEAD(nfs_automount_list);
  26 static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list);
  27 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  28
  29 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
  30                                         const struct dentry *dentry,
  31                                         struct nfs_fh *fh,
  32                                         struct nfs_fattr *fattr);
  33
  34 /*
  35  * nfs_path - reconstruct the path given an arbitrary dentry
  36  * @base - arbitrary string to prepend to the path
  37  * @droot - pointer to root dentry for mountpoint
  38  * @dentry - pointer to dentry
  39  * @buffer - result buffer
  40  * @buflen - length of buffer
  41  *
  42  * Helper function for constructing the path from the
  43  * root dentry to an arbitrary hashed dentry.
  44  *
  45  * This is mainly for use in figuring out the path on the
  46  * server side when automounting on top of an existing partition.
  47  */
  48 char *nfs_path(const char *base,
  49                const struct dentry *droot,
  50                const struct dentry *dentry,
  51                char *buffer, ssize_t buflen)
  52 {
  53         char *end = buffer+buflen;
  54         int namelen;
  55
  56         *--end = '\0';
  57         buflen--;
  58         spin_lock(&dcache_lock);
  59         while (!IS_ROOT(dentry) && dentry != droot) {
  60                 namelen = dentry->d_name.len;
  61                 buflen -= namelen + 1;
  62                 if (buflen < 0)
  63                         goto Elong_unlock;
  64                 end -= namelen;
  65                 memcpy(end, dentry->d_name.name, namelen);
  66                 *--end = '/';
  67                 dentry = dentry->d_parent;
  68         }
  69         spin_unlock(&dcache_lock);
  70         namelen = strlen(base);
  71         /* Strip off excess slashes in base string */
  72         while (namelen > 0 && base[namelen - 1] == '/')
  73                 namelen--;
  74         buflen -= namelen;
  75         if (buflen < 0)
  76                 goto Elong;
  77         end -= namelen;
  78         memcpy(end, base, namelen);
  79         return end;
  80 Elong_unlock:
  81         spin_unlock(&dcache_lock);
  82 Elong:
  83         return ERR_PTR(-ENAMETOOLONG);
  84 }
  85
  86 /*
  87  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  88  * @dentry - dentry of mountpoint
  89  * @nd - nameidata info
  90  *
  91  * When we encounter a mountpoint on the server, we want to set up
  92  * a mountpoint on the client too, to prevent inode numbers from
  93  * colliding, and to allow "df" to work properly.
  94  * On NFSv4, we also want to allow for the fact that different
  95  * filesystems may be migrated to different servers in a failover
  96  * situation, and that different filesystems may want to use
  97  * different security flavours.
  98  */
  99 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
 100 {
 101         struct vfsmount *mnt;
 102         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
 103         struct dentry *parent;
 104         struct nfs_fh fh;
 105         struct nfs_fattr fattr;
 106         int err;
 107
 108         dprintk("--> nfs_follow_mountpoint()\n");
 109
 110         BUG_ON(IS_ROOT(dentry));
 111         dprintk("%s: enter\n", __FUNCTION__);
 112         dput(nd->dentry);
 113         nd->dentry = dget(dentry);
 114
 115         /* Look it up again */
 116         parent = dget_parent(nd->dentry);
 117         err = server->nfs_client->rpc_ops->lookup(parent->d_inode,
 118                                                   &nd->dentry->d_name,
 119                                                   &fh, &fattr);
 120         dput(parent);
 121         if (err != 0)
 122                 goto out_err;
 123
 124         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
 125                 mnt = nfs_do_refmount(nd->mnt, nd->dentry);
 126         else
 127                 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
 128         err = PTR_ERR(mnt);
 129         if (IS_ERR(mnt))
 130                 goto out_err;
 131
 132         mntget(mnt);
 133         err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
 134         if (err < 0) {
 135                 mntput(mnt);
 136                 if (err == -EBUSY)
 137                         goto out_follow;
 138                 goto out_err;
 139         }
 140         mntput(nd->mnt);
 141         dput(nd->dentry);
 142         nd->mnt = mnt;
 143         nd->dentry = dget(mnt->mnt_root);
 144         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 145 out:
 146         dprintk("%s: done, returned %d\n", __FUNCTION__, err);
 147
 148         dprintk("<-- nfs_follow_mountpoint() = %d\n", err);
 149         return ERR_PTR(err);
 150 out_err:
 151         path_release(nd);
 152         goto out;
 153 out_follow:
 154         while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
 155                 ;
 156         err = 0;
 157         goto out;
 158 }
 159
 160 struct inode_operations nfs_mountpoint_inode_operations = {
 161         .follow_link    = nfs_follow_mountpoint,
 162         .getattr        = nfs_getattr,
 163 };
 164
 165 struct inode_operations nfs_referral_inode_operations = {
 166         .follow_link    = nfs_follow_mountpoint,
 167 };
 168
 169 static void nfs_expire_automounts(void *data)
 170 {
 171         struct list_head *list = (struct list_head *)data;
 172
 173         mark_mounts_for_expiry(list);
 174         if (!list_empty(list))
 175                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 176 }
 177
 178 void nfs_release_automount_timer(void)
 179 {
 180         if (list_empty(&nfs_automount_list)) {
 181                 cancel_delayed_work(&nfs_automount_task);
 182                 flush_scheduled_work();
 183         }
 184 }
 185
 186 /*
 187  * Clone a mountpoint of the appropriate type
 188  */
 189 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
 190                                            const char *devname,
 191                                            struct nfs_clone_mount *mountdata)
 192 {
 193 #ifdef CONFIG_NFS_V4
 194         struct vfsmount *mnt = NULL;
 195         switch (server->nfs_client->cl_nfsversion) {
 196                 case 2:
 197                 case 3:
 198                         mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 199                         break;
 200                 case 4:
 201                         mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata);
 202         }
 203         return mnt;
 204 #else
 205         return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
 206 #endif
 207 }
 208
 209 /**
 210  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 211  * @mnt_parent - mountpoint of parent directory
 212  * @dentry - parent directory
 213  * @fh - filehandle for new root dentry
 214  * @fattr - attributes for new root inode
 215  *
 216  */
 217 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 218                                         const struct dentry *dentry,
 219                                         struct nfs_fh *fh,
 220                                         struct nfs_fattr *fattr)
 221 {
 222         struct nfs_clone_mount mountdata = {
 223                 .sb = mnt_parent->mnt_sb,
 224                 .dentry = dentry,
 225                 .fh = fh,
 226                 .fattr = fattr,
 227         };
 228         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 229         char *page = (char *) __get_free_page(GFP_USER);
 230         char *devname;
 231
 232         dprintk("--> nfs_do_submount()\n");
 233
 234         dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
 235                         dentry->d_parent->d_name.name,
 236                         dentry->d_name.name);
 237         if (page == NULL)
 238                 goto out;
 239         devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
 240         mnt = (struct vfsmount *)devname;
 241         if (IS_ERR(devname))
 242                 goto free_page;
 243         mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
 244 free_page:
 245         free_page((unsigned long)page);
 246 out:
 247         dprintk("%s: done\n", __FUNCTION__);
 248
 249         dprintk("<-- nfs_do_submount() = %p\n", mnt);
 250         return mnt;
 251 }