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