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 {
  80         struct nfs_server *server = NFS_SB(sb);
  81         struct nfs_fsinfo fsinfo;
  82         struct dentry *ret;
  83         struct inode *inode;
  84         int error;
  85
  86         /* get the actual root for this mount */
  87         fsinfo.fattr = nfs_alloc_fattr();
  88         if (fsinfo.fattr == NULL)
  89                 return ERR_PTR(-ENOMEM);
  90
  91         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  92         if (error < 0) {
  93                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  94                 ret = ERR_PTR(error);
  95                 goto out;
  96         }
  97
  98         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  99         if (IS_ERR(inode)) {
 100                 dprintk("nfs_get_root: get root inode failed\n");
 101                 ret = ERR_CAST(inode);
 102                 goto out;
 103         }
 104
 105         error = nfs_superblock_set_dummy_root(sb, inode);
 106         if (error != 0) {
 107                 ret = ERR_PTR(error);
 108                 goto out;
 109         }
 110
 111         /* root dentries normally start off anonymous and get spliced in later
 112          * if the dentry tree reaches them; however if the dentry already
 113          * exists, we'll pick it up at this point and use it as the root
 114          */
 115         ret = d_obtain_alias(inode);
 116         if (IS_ERR(ret)) {
 117                 dprintk("nfs_get_root: get root dentry failed\n");
 118                 goto out;
 119         }
 120
 121         security_d_instantiate(ret, inode);
 122 out:
 123         nfs_free_fattr(fsinfo.fattr);
 124         return ret;
 125 }
 126
 127 #ifdef CONFIG_NFS_V4
 128
 129 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 130 {
 131         struct nfs_fsinfo fsinfo;
 132         int ret = -ENOMEM;
 133
 134         dprintk("--> nfs4_get_rootfh()\n");
 135
 136         fsinfo.fattr = nfs_alloc_fattr();
 137         if (fsinfo.fattr == NULL)
 138                 goto out;
 139
 140         /* Start by getting the root filehandle from the server */
 141         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 142         if (ret < 0) {
 143                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 144                 goto out;
 145         }
 146
 147         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
 148                         || !S_ISDIR(fsinfo.fattr->mode)) {
 149                 printk(KERN_ERR "nfs4_get_rootfh:"
 150                        " getroot encountered non-directory\n");
 151                 ret = -ENOTDIR;
 152                 goto out;
 153         }
 154
 155         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 156                 printk(KERN_ERR "nfs4_get_rootfh:"
 157                        " getroot obtained referral\n");
 158                 ret = -EREMOTE;
 159                 goto out;
 160         }
 161
 162         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 163 out:
 164         nfs_free_fattr(fsinfo.fattr);
 165         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 166         return ret;
 167 }
 168
 169 /*
 170  * get an NFS4 root dentry from the root filehandle
 171  */
 172 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 173 {
 174         struct nfs_server *server = NFS_SB(sb);
 175         struct nfs_fattr *fattr = NULL;
 176         struct dentry *ret;
 177         struct inode *inode;
 178         int error;
 179
 180         dprintk("--> nfs4_get_root()\n");
 181
 182         /* get the info about the server and filesystem */
 183         error = nfs4_server_capabilities(server, mntfh);
 184         if (error < 0) {
 185                 dprintk("nfs_get_root: getcaps error = %d\n",
 186                         -error);
 187                 return ERR_PTR(error);
 188         }
 189
 190         fattr = nfs_alloc_fattr();
 191         if (fattr == NULL)
 192                 return ERR_PTR(-ENOMEM);;
 193
 194         /* get the actual root for this mount */
 195         error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
 196         if (error < 0) {
 197                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 198                 ret = ERR_PTR(error);
 199                 goto out;
 200         }
 201
 202         inode = nfs_fhget(sb, mntfh, fattr);
 203         if (IS_ERR(inode)) {
 204                 dprintk("nfs_get_root: get root inode failed\n");
 205                 ret = ERR_CAST(inode);
 206                 goto out;
 207         }
 208
 209         error = nfs_superblock_set_dummy_root(sb, inode);
 210         if (error != 0) {
 211                 ret = ERR_PTR(error);
 212                 goto out;
 213         }
 214
 215         /* root dentries normally start off anonymous and get spliced in later
 216          * if the dentry tree reaches them; however if the dentry already
 217          * exists, we'll pick it up at this point and use it as the root
 218          */
 219         ret = d_obtain_alias(inode);
 220         if (IS_ERR(ret)) {
 221                 dprintk("nfs_get_root: get root dentry failed\n");
 222                 goto out;
 223         }
 224
 225         security_d_instantiate(ret, inode);
 226
 227 out:
 228         nfs_free_fattr(fattr);
 229         dprintk("<-- nfs4_get_root()\n");
 230         return ret;
 231 }
 232
 233 #endif /* CONFIG_NFS_V4 */