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;
  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:
  72         return ERR_PTR(-ENAMETOOLONG);
  73 }
  74
  75 /*
  76  * nfs_follow_mountpoint - handle crossing a mountpoint on the server
  77  * @dentry - dentry of mountpoint
  78  * @nd - nameidata info
  79  *
  80  * When we encounter a mountpoint on the server, we want to set up
  81  * a mountpoint on the client too, to prevent inode numbers from
  82  * colliding, and to allow "df" to work properly.
  83  * On NFSv4, we also want to allow for the fact that different
  84  * filesystems may be migrated to different servers in a failover
  85  * situation, and that different filesystems may want to use
  86  * different security flavours.
  87  */
  88 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
  89 {
  90         struct vfsmount *mnt;
  91         struct nfs_server *server = NFS_SERVER(dentry->d_inode);
  92         struct dentry *parent;
  93         struct nfs_fh fh;
  94         struct nfs_fattr fattr;
  95         int err;
  96
  97         BUG_ON(IS_ROOT(dentry));
  98         dprintk("%s: enter\n", __FUNCTION__);
  99         dput(nd->dentry);
 100         nd->dentry = dget(dentry);
 101         if (d_mountpoint(nd->dentry))
 102                 goto out_follow;
 103         /* Look it up again */
 104         parent = dget_parent(nd->dentry);
 105         err = server->rpc_ops->lookup(parent->d_inode, &nd->dentry->d_name, &fh, &fattr);
 106         dput(parent);
 107         if (err != 0)
 108                 goto out_err;
 109
 110         if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL)
 111                 mnt = nfs_do_refmount(nd->mnt, nd->dentry);
 112         else
 113                 mnt = nfs_do_submount(nd->mnt, nd->dentry, &fh, &fattr);
 114         err = PTR_ERR(mnt);
 115         if (IS_ERR(mnt))
 116                 goto out_err;
 117
 118         mntget(mnt);
 119         err = do_add_mount(mnt, nd, nd->mnt->mnt_flags|MNT_SHRINKABLE, &nfs_automount_list);
 120         if (err < 0) {
 121                 mntput(mnt);
 122                 if (err == -EBUSY)
 123                         goto out_follow;
 124                 goto out_err;
 125         }
 126         mntput(nd->mnt);
 127         dput(nd->dentry);
 128         nd->mnt = mnt;
 129         nd->dentry = dget(mnt->mnt_root);
 130         schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 131 out:
 132         dprintk("%s: done, returned %d\n", __FUNCTION__, err);
 133         return ERR_PTR(err);
 134 out_err:
 135         path_release(nd);
 136         goto out;
 137 out_follow:
 138         while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
 139                 ;
 140         err = 0;
 141         goto out;
 142 }
 143
 144 struct inode_operations nfs_mountpoint_inode_operations = {
 145         .follow_link    = nfs_follow_mountpoint,
 146         .getattr        = nfs_getattr,
 147 };
 148
 149 struct inode_operations nfs_referral_inode_operations = {
 150         .follow_link    = nfs_follow_mountpoint,
 151 };
 152
 153 static void nfs_expire_automounts(void *data)
 154 {
 155         struct list_head *list = (struct list_head *)data;
 156
 157         mark_mounts_for_expiry(list);
 158         if (!list_empty(list))
 159                 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
 160 }
 161
 162 void nfs_release_automount_timer(void)
 163 {
 164         if (list_empty(&nfs_automount_list)) {
 165                 cancel_delayed_work(&nfs_automount_task);
 166                 flush_scheduled_work();
 167         }
 168 }
 169
 170 /*
 171  * Clone a mountpoint of the appropriate type
 172  */
 173 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, char *devname,
 174                                            struct nfs_clone_mount *mountdata)
 175 {
 176 #ifdef CONFIG_NFS_V4
 177         struct vfsmount *mnt = NULL;
 178         switch (server->rpc_ops->version) {
 179                 case 2:
 180                 case 3:
 181                         mnt = vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
 182                         break;
 183                 case 4:
 184                         mnt = vfs_kern_mount(&clone_nfs4_fs_type, 0, devname, mountdata);
 185         }
 186         return mnt;
 187 #else
 188         return vfs_kern_mount(&clone_nfs_fs_type, 0, devname, mountdata);
 189 #endif
 190 }
 191
 192 /**
 193  * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
 194  * @mnt_parent - mountpoint of parent directory
 195  * @dentry - parent directory
 196  * @fh - filehandle for new root dentry
 197  * @fattr - attributes for new root inode
 198  *
 199  */
 200 struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent,
 201                 const struct dentry *dentry, struct nfs_fh *fh,
 202                 struct nfs_fattr *fattr)
 203 {
 204         struct nfs_clone_mount mountdata = {
 205                 .sb = mnt_parent->mnt_sb,
 206                 .dentry = dentry,
 207                 .fh = fh,
 208                 .fattr = fattr,
 209         };
 210         struct vfsmount *mnt = ERR_PTR(-ENOMEM);
 211         char *page = (char *) __get_free_page(GFP_USER);
 212         char *devname;
 213
 214         dprintk("%s: submounting on %s/%s\n", __FUNCTION__,
 215                         dentry->d_parent->d_name.name,
 216                         dentry->d_name.name);
 217         if (page == NULL)
 218                 goto out;
 219         devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE);
 220         mnt = (struct vfsmount *)devname;
 221         if (IS_ERR(devname))
 222                 goto free_page;
 223         mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata);
 224 free_page:
 225         free_page((unsigned long)page);
 226 out:
 227         dprintk("%s: done\n", __FUNCTION__);
 228         return mnt;
 229 }