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_make_root(inode);
  53                 if (sb->s_root == NULL)
  54                         return -ENOMEM;
  55                 ihold(inode);
  56                 /*
  57                  * Ensure that this dentry is invisible to d_find_alias().
  58                  * Otherwise, it may be spliced into the tree by
  59                  * d_materialise_unique if a parent directory from the same
  60                  * filesystem gets mounted at a later time.
  61                  * This again causes shrink_dcache_for_umount_subtree() to
  62                  * Oops, since the test for IS_ROOT() will fail.
  63                  */
  64                 spin_lock(&sb->s_root->d_inode->i_lock);
  65                 spin_lock(&sb->s_root->d_lock);
  66                 list_del_init(&sb->s_root->d_alias);
  67                 spin_unlock(&sb->s_root->d_lock);
  68                 spin_unlock(&sb->s_root->d_inode->i_lock);
  69         }
  70         return 0;
  71 }
  72
  73 /*
  74  * get an NFS2/NFS3 root dentry from the root filehandle
  75  */
  76 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
  77                             const char *devname)
  78 {
  79         struct nfs_server *server = NFS_SB(sb);
  80         struct nfs_fsinfo fsinfo;
  81         struct dentry *ret;
  82         struct inode *inode;
  83         void *name = kstrdup(devname, GFP_KERNEL);
  84         int error;
  85
  86         if (!name)
  87                 return ERR_PTR(-ENOMEM);
  88
  89         /* get the actual root for this mount */
  90         fsinfo.fattr = nfs_alloc_fattr();
  91         if (fsinfo.fattr == NULL) {
  92                 kfree(name);
  93                 return ERR_PTR(-ENOMEM);
  94         }
  95
  96         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  97         if (error < 0) {
  98                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  99                 ret = ERR_PTR(error);
 100                 goto out;
 101         }
 102
 103         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
 104         if (IS_ERR(inode)) {
 105                 dprintk("nfs_get_root: get root inode failed\n");
 106                 ret = ERR_CAST(inode);
 107                 goto out;
 108         }
 109
 110         error = nfs_superblock_set_dummy_root(sb, inode);
 111         if (error != 0) {
 112                 ret = ERR_PTR(error);
 113                 goto out;
 114         }
 115
 116         /* root dentries normally start off anonymous and get spliced in later
 117          * if the dentry tree reaches them; however if the dentry already
 118          * exists, we'll pick it up at this point and use it as the root
 119          */
 120         ret = d_obtain_alias(inode);
 121         if (IS_ERR(ret)) {
 122                 dprintk("nfs_get_root: get root dentry failed\n");
 123                 goto out;
 124         }
 125
 126         security_d_instantiate(ret, inode);
 127         spin_lock(&ret->d_lock);
 128         if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 129                 ret->d_fsdata = name;
 130                 name = NULL;
 131         }
 132         spin_unlock(&ret->d_lock);
 133 out:
 134         if (name)
 135                 kfree(name);
 136         nfs_free_fattr(fsinfo.fattr);
 137         return ret;
 138 }
 139
 140 #ifdef CONFIG_NFS_V4
 141
 142 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 143 {
 144         struct nfs_fsinfo fsinfo;
 145         int ret = -ENOMEM;
 146
 147         dprintk("--> nfs4_get_rootfh()\n");
 148
 149         fsinfo.fattr = nfs_alloc_fattr();
 150         if (fsinfo.fattr == NULL)
 151                 goto out;
 152
 153         /* Start by getting the root filehandle from the server */
 154         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 155         if (ret < 0) {
 156                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 157                 goto out;
 158         }
 159
 160         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
 161                         || !S_ISDIR(fsinfo.fattr->mode)) {
 162                 printk(KERN_ERR "nfs4_get_rootfh:"
 163                        " getroot encountered non-directory\n");
 164                 ret = -ENOTDIR;
 165                 goto out;
 166         }
 167
 168         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 169                 printk(KERN_ERR "nfs4_get_rootfh:"
 170                        " getroot obtained referral\n");
 171                 ret = -EREMOTE;
 172                 goto out;
 173         }
 174
 175         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 176 out:
 177         nfs_free_fattr(fsinfo.fattr);
 178         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 179         return ret;
 180 }
 181
 182 /*
 183  * get an NFS4 root dentry from the root filehandle
 184  */
 185 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh,
 186                              const char *devname)
 187 {
 188         struct nfs_server *server = NFS_SB(sb);
 189         struct nfs_fattr *fattr = NULL;
 190         struct dentry *ret;
 191         struct inode *inode;
 192         void *name = kstrdup(devname, GFP_KERNEL);
 193         int error;
 194
 195         dprintk("--> nfs4_get_root()\n");
 196
 197         if (!name)
 198                 return ERR_PTR(-ENOMEM);
 199
 200         /* get the info about the server and filesystem */
 201         error = nfs4_server_capabilities(server, mntfh);
 202         if (error < 0) {
 203                 dprintk("nfs_get_root: getcaps error = %d\n",
 204                         -error);
 205                 kfree(name);
 206                 return ERR_PTR(error);
 207         }
 208
 209         fattr = nfs_alloc_fattr();
 210         if (fattr == NULL) {
 211                 kfree(name);
 212                 return ERR_PTR(-ENOMEM);
 213         }
 214
 215         /* get the actual root for this mount */
 216         error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
 217         if (error < 0) {
 218                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 219                 ret = ERR_PTR(error);
 220                 goto out;
 221         }
 222
 223         if (fattr->valid & NFS_ATTR_FATTR_FSID &&
 224             !nfs_fsid_equal(&server->fsid, &fattr->fsid))
 225                 memcpy(&server->fsid, &fattr->fsid, sizeof(server->fsid));
 226
 227         inode = nfs_fhget(sb, mntfh, fattr);
 228         if (IS_ERR(inode)) {
 229                 dprintk("nfs_get_root: get root inode failed\n");
 230                 ret = ERR_CAST(inode);
 231                 goto out;
 232         }
 233
 234         error = nfs_superblock_set_dummy_root(sb, inode);
 235         if (error != 0) {
 236                 ret = ERR_PTR(error);
 237                 goto out;
 238         }
 239
 240         /* root dentries normally start off anonymous and get spliced in later
 241          * if the dentry tree reaches them; however if the dentry already
 242          * exists, we'll pick it up at this point and use it as the root
 243          */
 244         ret = d_obtain_alias(inode);
 245         if (IS_ERR(ret)) {
 246                 dprintk("nfs_get_root: get root dentry failed\n");
 247                 goto out;
 248         }
 249
 250         security_d_instantiate(ret, inode);
 251         spin_lock(&ret->d_lock);
 252         if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 253                 ret->d_fsdata = name;
 254                 name = NULL;
 255         }
 256         spin_unlock(&ret->d_lock);
 257 out:
 258         if (name)
 259                 kfree(name);
 260         nfs_free_fattr(fattr);
 261         dprintk("<-- nfs4_get_root()\n");
 262         return ret;
 263 }
 264
 265 #endif /* CONFIG_NFS_V4 */