fs/nfs/namespace.c

   1 /*
   2  * linux/fs/nfs/namespace.c
   3  *
   4  * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
   5  *
   6  * NFS namespace
   7  */
   8
   9 #include <linux/config.h>
  10
  11 #include <linux/dcache.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(void *list);
  23
  24 LIST_HEAD(nfs_automount_list);
  25 static DECLARE_WORK(nfs_automount_task, nfs_expire_automounts, &nfs_automount_list);
  26 int nfs_mountpoint_expiry_timeout = 500 * HZ;
  27
  28 /*
  29  * nfs_path - reconstruct the path given an arbitrary dentry
  30  * @base - arbitrary string to prepend to the path
  31  * @dentry - pointer to dentry
  32  * @buffer - result buffer
  33  * @buflen - length of buffer
  34  *
  35  * Helper function for constructing the path from the
  36  * root dentry to an arbitrary hashed dentry.
  37  *
  38  * This is mainly for use in figuring out the path on the
  39  * server side when automounting on top of an existing partition.
  40  */
  41 char *nfs_path(const char *base, const struct dentry *dentry,
  42                char *buffer, ssize_t buflen)
  43 {
  44         char *end = buffer+buflen;
  45         int namelen;
  46
  47         *--end = '\0';
  48         buflen--;
  49         spin_lock(&dcache_lock);
  50         while (!IS_ROOT(dentry)) {
  51                 namelen = dentry->d_name.len;
  52                 buflen -= namelen + 1;
  53                 if (buflen < 0)
  54                         goto Elong_unlock;
  55                 end -= namelen;
  56                 memcpy(end, dentry->d_name.name, namelen);
  57                 *--end = '/';
  58                 dentry = dentry->d_parent;
  59         }
  60         spin_unlock(&dcache_lock);
  61         namelen = strlen(base);
  62         /* Strip off excess slashes in base string */
  63         while (namelen > 0 && base[namelen - 1] == '/')
  64                 namelen--;
  65         buflen -= namelen;
  66         if (buflen < 0)
  67                 goto Elong;
  68         end -= namelen;
  69         memcpy(end, base, namelen);
  70         return end;
  71 Elong_unlock:
  72         spin_unlock(&dcache_lock);
  73 Elong:
  74         return ERR_PTR(-ENAMETOOLONG);
  75 }
  76
  77 /*
  78  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  79  * @dentry - dentry of mountpoint
  80  * @nd - nameidata info
  81  *
  82  * When we encounter a mountpoint on the server, we want to set up
  83  * a mountpoint on the client too, to prevent inode numbers from
  84  * colliding, and to allow "df" to work properly.
  85  * On NFSv4, we also want to allow for the fact that different
  86  * filesystems may be migrated to different servers in a failover
  87  * situation, and that different filesystems may want to use
  88  * different security flavours.
  89  */
  90 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
  91 {
  92         struct vfsmount *mnt;
  93         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
  94         struct dentry *parent;
  95         struct nfs_fh fh;
  96         struct nfs_fattr fattr;
  97         int err;
  98
  99         BUG_ON(IS_ROOT(dentry));
 100         dprintk("%s: enter\n", __FUNCTION__);
 101         dput(nd->dentry);
 102         nd->dentry = dget(dentry);
 103         if (d_mountpoint(nd->dentry))
 104                 goto out_follow;
 105         /* Look it up again */
 106         parent = dget_parent(nd->dentry);
 107         err = server->rpc_ops->lookup(parent->d_inode, &nd->dentry->d_name, &fh, &fattr);
 108         dput(parent);
 109         if (err != 0)
 110                 goto out_err;
 111
 112         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
 113                 mnt = nfs_do_refmount(nd->mnt, nd->dentry);
 114         else
 115                 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
 116         err = PTR_ERR(mnt);
 117         if (IS_ERR(mnt))
 118                 goto out_err;
 119
 120         mntget(mnt);
 121         err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
 122         if (err < 0) {
 123                 mntput(mnt);
 124                 if (err == -EBUSY)
 125                         goto out_follow;
 126                 goto out_err;
 127         }
 128         mntput(nd->mnt);
 129         dput(nd->dentry);
 130         nd->mnt = mnt;
 131         nd->dentry = dget(mnt->mnt_root);
 132         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 133 out:
 134         dprintk("%s: done, returned %d\n", __FUNCTION__, err);
 135         return ERR_PTR(err);
 136 out_err:
 137         path_release(nd);
 138         goto out;
 139 out_follow:
 140         while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
 141                 ;
 142         err = 0;
 143         goto out;
 144 }
 145
 146 struct inode_operations nfs_mountpoint_inode_operations = {
 147         .follow_link    = nfs_follow_mountpoint,
 148         .getattr        = nfs_getattr,
 149 };
 150
 151 struct inode_operations nfs_referral_inode_operations = {
 152         .follow_link    = nfs_follow_mountpoint,
 153 };
 154
 155 static void nfs_expire_automounts(void *data)
 156 {
 157         struct list_head *list = (struct list_head *)data;
 158
 159         mark_mounts_for_expiry(list);
 160         if (!list_empty(list))
 161                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 162 }
 163
 164 void nfs_release_automount_timer(void)
 165 {
 166         if (list_empty(&nfs_automount_list)) {
 167                 cancel_delayed_work(&nfs_automount_task);
 168                 flush_scheduled_work();
 169         }
 170 }
 171
 172 /*
 173  * Clone a mountpoint of the appropriate type
 174  */
 175 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, char *devname,
 176                                            struct nfs_clone_mount *mountdata)
 177 {
 178 #ifdef CONFIG_NFS_V4
 179         struct vfsmount *mnt = NULL;
 180         switch (server->rpc_ops->version) {
 181                 case 2:
 182                 case 3:
 183                         mnt = vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
 184                         break;
 185                 case 4:
 186                         mnt = vfs_kern_mount(&clone_nfs4_fs_type, 0, devname, mountdata);
 187         }
 188         return mnt;
 189 #else
 190         return vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
 191 #endif
 192 }
 193
 194 /**
 195  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 196  * @mnt_parent - mountpoint of parent directory
 197  * @dentry - parent directory
 198  * @fh - filehandle for new root dentry
 199  * @fattr - attributes for new root inode
 200  *
 201  */
 202 struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 203                 const struct dentry *dentry, struct nfs_fh *fh,
 204                 struct nfs_fattr *fattr)
 205 {
 206         struct nfs_clone_mount mountdata = {
 207                 .sb = mnt_parent->mnt_sb,
 208                 .dentry = dentry,
 209                 .fh = fh,
 210                 .fattr = fattr,
 211         };
 212         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 213         char *page = (char *) __get_free_page(GFP_USER);
 214         char *devname;
 215
 216         dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
 217                         dentry->d_parent->d_name.name,
 218                         dentry->d_name.name);
 219         if (page == NULL)
 220                 goto out;
 221         devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
 222         mnt = (struct vfsmount *)devname;
 223         if (IS_ERR(devname))
 224                 goto free_page;
 225         mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
 226 free_page:
 227         free_page((unsigned long)page);
 228 out:
 229         dprintk("%s: done\n", __FUNCTION__);
 230         return mnt;
 231 }