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(&dcache_lock);
  67                 list_del_init(&sb->s_root->d_alias);
  68                 spin_unlock(&dcache_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 {
  78         struct nfs_server *server = NFS_SB(sb);
  79         struct nfs_fsinfo fsinfo;
  80         struct dentry *ret;
  81         struct inode *inode;
  82         int error;
  83
  84         /* get the actual root for this mount */
  85         fsinfo.fattr = nfs_alloc_fattr();
  86         if (fsinfo.fattr == NULL)
  87                 return ERR_PTR(-ENOMEM);
  88
  89         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  90         if (error < 0) {
  91                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  92                 ret = ERR_PTR(error);
  93                 goto out;
  94         }
  95
  96         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  97         if (IS_ERR(inode)) {
  98                 dprintk("nfs_get_root: get root inode failed\n");
  99                 ret = ERR_CAST(inode);
 100                 goto out;
 101         }
 102
 103         error = nfs_superblock_set_dummy_root(sb, inode);
 104         if (error != 0) {
 105                 ret = ERR_PTR(error);
 106                 goto out;
 107         }
 108
 109         /* root dentries normally start off anonymous and get spliced in later
 110          * if the dentry tree reaches them; however if the dentry already
 111          * exists, we'll pick it up at this point and use it as the root
 112          */
 113         ret = d_obtain_alias(inode);
 114         if (IS_ERR(ret)) {
 115                 dprintk("nfs_get_root: get root dentry failed\n");
 116                 goto out;
 117         }
 118
 119         security_d_instantiate(ret, inode);
 120
 121         if (ret->d_op == NULL)
 122                 ret->d_op = server->nfs_client->rpc_ops->dentry_ops;
 123 out:
 124         nfs_free_fattr(fsinfo.fattr);
 125         return ret;
 126 }
 127
 128 #ifdef CONFIG_NFS_V4
 129
 130 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 131 {
 132         struct nfs_fsinfo fsinfo;
 133         int ret = -ENOMEM;
 134
 135         dprintk("--> nfs4_get_rootfh()\n");
 136
 137         fsinfo.fattr = nfs_alloc_fattr();
 138         if (fsinfo.fattr == NULL)
 139                 goto out;
 140
 141         /* Start by getting the root filehandle from the server */
 142         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 143         if (ret < 0) {
 144                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 145                 goto out;
 146         }
 147
 148         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
 149                         || !S_ISDIR(fsinfo.fattr->mode)) {
 150                 printk(KERN_ERR "nfs4_get_rootfh:"
 151                        " getroot encountered non-directory\n");
 152                 ret = -ENOTDIR;
 153                 goto out;
 154         }
 155
 156         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 157                 printk(KERN_ERR "nfs4_get_rootfh:"
 158                        " getroot obtained referral\n");
 159                 ret = -EREMOTE;
 160                 goto out;
 161         }
 162
 163         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 164 out:
 165         nfs_free_fattr(fsinfo.fattr);
 166         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 167         return ret;
 168 }
 169
 170 /*
 171  * get an NFS4 root dentry from the root filehandle
 172  */
 173 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 174 {
 175         struct nfs_server *server = NFS_SB(sb);
 176         struct nfs_fattr *fattr = NULL;
 177         struct dentry *ret;
 178         struct inode *inode;
 179         int error;
 180
 181         dprintk("--> nfs4_get_root()\n");
 182
 183         /* get the info about the server and filesystem */
 184         error = nfs4_server_capabilities(server, mntfh);
 185         if (error < 0) {
 186                 dprintk("nfs_get_root: getcaps error = %d\n",
 187                         -error);
 188                 return ERR_PTR(error);
 189         }
 190
 191         fattr = nfs_alloc_fattr();
 192         if (fattr == NULL)
 193                 return ERR_PTR(-ENOMEM);;
 194
 195         /* get the actual root for this mount */
 196         error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
 197         if (error < 0) {
 198                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 199                 ret = ERR_PTR(error);
 200                 goto out;
 201         }
 202
 203         inode = nfs_fhget(sb, mntfh, fattr);
 204         if (IS_ERR(inode)) {
 205                 dprintk("nfs_get_root: get root inode failed\n");
 206                 ret = ERR_CAST(inode);
 207                 goto out;
 208         }
 209
 210         error = nfs_superblock_set_dummy_root(sb, inode);
 211         if (error != 0) {
 212                 ret = ERR_PTR(error);
 213                 goto out;
 214         }
 215
 216         /* root dentries normally start off anonymous and get spliced in later
 217          * if the dentry tree reaches them; however if the dentry already
 218          * exists, we'll pick it up at this point and use it as the root
 219          */
 220         ret = d_obtain_alias(inode);
 221         if (IS_ERR(ret)) {
 222                 dprintk("nfs_get_root: get root dentry failed\n");
 223                 goto out;
 224         }
 225
 226         security_d_instantiate(ret, inode);
 227
 228         if (ret->d_op == NULL)
 229                 ret->d_op = server->nfs_client->rpc_ops->dentry_ops;
 230
 231 out:
 232         nfs_free_fattr(fattr);
 233         dprintk("<-- nfs4_get_root()\n");
 234         return ret;
 235 }
 236
 237 #endif /* CONFIG_NFS_V4 */