fs/nfs/getroot.c

   1 /* getroot.c: get the root dentry for an NFS mount
   2  *
   3  * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14
  15 #include <linux/time.h>
  16 #include <linux/kernel.h>
  17 #include <linux/mm.h>
  18 #include <linux/string.h>
  19 #include <linux/stat.h>
  20 #include <linux/errno.h>
  21 #include <linux/unistd.h>
  22 #include <linux/sunrpc/clnt.h>
  23 #include <linux/sunrpc/stats.h>
  24 #include <linux/nfs_fs.h>
  25 #include <linux/nfs_mount.h>
  26 #include <linux/nfs4_mount.h>
  27 #include <linux/lockd/bind.h>
  28 #include <linux/seq_file.h>
  29 #include <linux/mount.h>
  30 #include <linux/nfs_idmap.h>
  31 #include <linux/vfs.h>
  32 #include <linux/namei.h>
  33 #include <linux/security.h>
  34
  35 #include <asm/system.h>
  36 #include <asm/uaccess.h>
  37
  38 #include "nfs4_fs.h"
  39 #include "delegation.h"
  40 #include "internal.h"
  41
  42 #define NFSDBG_FACILITY         NFSDBG_CLIENT
  43
  44 /*
  45  * Set the superblock root dentry.
  46  * Note that this function frees the inode in case of error.
  47  */
  48 static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
  49 {
  50         /* The mntroot acts as the dummy root dentry for this superblock */
  51         if (sb->s_root == NULL) {
  52                 sb->s_root = d_alloc_root(inode);
  53                 if (sb->s_root == NULL) {
  54                         iput(inode);
  55                         return -ENOMEM;
  56                 }
  57                 ihold(inode);
  58                 /*
  59                  * Ensure that this dentry is invisible to d_find_alias().
  60                  * Otherwise, it may be spliced into the tree by
  61                  * d_materialise_unique if a parent directory from the same
  62                  * filesystem gets mounted at a later time.
  63                  * This again causes shrink_dcache_for_umount_subtree() to
  64                  * Oops, since the test for IS_ROOT() will fail.
  65                  */
  66                 spin_lock(&sb->s_root->d_inode->i_lock);
  67                 spin_lock(&sb->s_root->d_lock);
  68                 list_del_init(&sb->s_root->d_alias);
  69                 spin_unlock(&sb->s_root->d_lock);
  70                 spin_unlock(&sb->s_root->d_inode->i_lock);
  71         }
  72         return 0;
  73 }
  74
  75 /*
  76  * get an NFS2/NFS3 root dentry from the root filehandle
  77  */
  78 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
  79                             const char *devname)
  80 {
  81         struct nfs_server *server = NFS_SB(sb);
  82         struct nfs_fsinfo fsinfo;
  83         struct dentry *ret;
  84         struct inode *inode;
  85         void *name = kstrdup(devname, GFP_KERNEL);
  86         int error;
  87
  88         if (!name)
  89                 return ERR_PTR(-ENOMEM);
  90
  91         /* get the actual root for this mount */
  92         fsinfo.fattr = nfs_alloc_fattr();
  93         if (fsinfo.fattr == NULL) {
  94                 kfree(name);
  95                 return ERR_PTR(-ENOMEM);
  96         }
  97
  98         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  99         if (error < 0) {
 100                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 101                 ret = ERR_PTR(error);
 102                 goto out;
 103         }
 104
 105         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
 106         if (IS_ERR(inode)) {
 107                 dprintk("nfs_get_root: get root inode failed\n");
 108                 ret = ERR_CAST(inode);
 109                 goto out;
 110         }
 111
 112         error = nfs_superblock_set_dummy_root(sb, inode);
 113         if (error != 0) {
 114                 ret = ERR_PTR(error);
 115                 goto out;
 116         }
 117
 118         /* root dentries normally start off anonymous and get spliced in later
 119          * if the dentry tree reaches them; however if the dentry already
 120          * exists, we'll pick it up at this point and use it as the root
 121          */
 122         ret = d_obtain_alias(inode);
 123         if (IS_ERR(ret)) {
 124                 dprintk("nfs_get_root: get root dentry failed\n");
 125                 goto out;
 126         }
 127
 128         security_d_instantiate(ret, inode);
 129         spin_lock(&ret->d_lock);
 130         if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 131                 ret->d_fsdata = name;
 132                 name = NULL;
 133         }
 134         spin_unlock(&ret->d_lock);
 135 out:
 136         if (name)
 137                 kfree(name);
 138         nfs_free_fattr(fsinfo.fattr);
 139         return ret;
 140 }
 141
 142 #ifdef CONFIG_NFS_V4
 143
 144 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 145 {
 146         struct nfs_fsinfo fsinfo;
 147         int ret = -ENOMEM;
 148
 149         dprintk("--> nfs4_get_rootfh()\n");
 150
 151         fsinfo.fattr = nfs_alloc_fattr();
 152         if (fsinfo.fattr == NULL)
 153                 goto out;
 154
 155         /* Start by getting the root filehandle from the server */
 156         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 157         if (ret < 0) {
 158                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 159                 goto out;
 160         }
 161
 162         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
 163                         || !S_ISDIR(fsinfo.fattr->mode)) {
 164                 printk(KERN_ERR "nfs4_get_rootfh:"
 165                        " getroot encountered non-directory\n");
 166                 ret = -ENOTDIR;
 167                 goto out;
 168         }
 169
 170         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 171                 printk(KERN_ERR "nfs4_get_rootfh:"
 172                        " getroot obtained referral\n");
 173                 ret = -EREMOTE;
 174                 goto out;
 175         }
 176
 177         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 178 out:
 179         nfs_free_fattr(fsinfo.fattr);
 180         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 181         return ret;
 182 }
 183
 184 /*
 185  * get an NFS4 root dentry from the root filehandle
 186  */
 187 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 188                              const char *devname)
 189 {
 190         struct nfs_server *server = NFS_SB(sb);
 191         struct nfs_fattr *fattr = NULL;
 192         struct dentry *ret;
 193         struct inode *inode;
 194         void *name = kstrdup(devname, GFP_KERNEL);
 195         int error;
 196
 197         dprintk("--> nfs4_get_root()\n");
 198
 199         if (!name)
 200                 return ERR_PTR(-ENOMEM);
 201
 202         /* get the info about the server and filesystem */
 203         error = nfs4_server_capabilities(server, mntfh);
 204         if (error < 0) {
 205                 dprintk("nfs_get_root: getcaps error = %d\n",
 206                         -error);
 207                 kfree(name);
 208                 return ERR_PTR(error);
 209         }
 210
 211         fattr = nfs_alloc_fattr();
 212         if (fattr == NULL) {
 213                 kfree(name);
 214                 return ERR_PTR(-ENOMEM);
 215         }
 216
 217         /* get the actual root for this mount */
 218         error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
 219         if (error < 0) {
 220                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 221                 ret = ERR_PTR(error);
 222                 goto out;
 223         }
 224
 225         inode = nfs_fhget(sb, mntfh, fattr);
 226         if (IS_ERR(inode)) {
 227                 dprintk("nfs_get_root: get root inode failed\n");
 228                 ret = ERR_CAST(inode);
 229                 goto out;
 230         }
 231
 232         error = nfs_superblock_set_dummy_root(sb, inode);
 233         if (error != 0) {
 234                 ret = ERR_PTR(error);
 235                 goto out;
 236         }
 237
 238         /* root dentries normally start off anonymous and get spliced in later
 239          * if the dentry tree reaches them; however if the dentry already
 240          * exists, we'll pick it up at this point and use it as the root
 241          */
 242         ret = d_obtain_alias(inode);
 243         if (IS_ERR(ret)) {
 244                 dprintk("nfs_get_root: get root dentry failed\n");
 245                 goto out;
 246         }
 247
 248         security_d_instantiate(ret, inode);
 249         spin_lock(&ret->d_lock);
 250         if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 251                 ret->d_fsdata = name;
 252                 name = NULL;
 253         }
 254         spin_unlock(&ret->d_lock);
 255 out:
 256         if (name)
 257                 kfree(name);
 258         nfs_free_fattr(fattr);
 259         dprintk("<-- nfs4_get_root()\n");
 260         return ret;
 261 }
 262
 263 #endif /* CONFIG_NFS_V4 */