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                 /* Circumvent igrab(): we know the inode is not being freed */
  58                 atomic_inc(&inode->i_count);
  59                 /*
  60                  * Ensure that this dentry is invisible to d_find_alias().
  61                  * Otherwise, it may be spliced into the tree by
  62                  * d_materialise_unique if a parent directory from the same
  63                  * filesystem gets mounted at a later time.
  64                  * This again causes shrink_dcache_for_umount_subtree() to
  65                  * Oops, since the test for IS_ROOT() will fail.
  66                  */
  67                 spin_lock(&dcache_lock);
  68                 list_del_init(&sb->s_root->d_alias);
  69                 spin_unlock(&dcache_lock);
  70         }
  71         return 0;
  72 }
  73
  74 /*
  75  * get an NFS2/NFS3 root dentry from the root filehandle
  76  */
  77 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh)
  78 {
  79         struct nfs_server *server = NFS_SB(sb);
  80         struct nfs_fsinfo fsinfo;
  81         struct dentry *ret;
  82         struct inode *inode;
  83         int error;
  84
  85         /* get the actual root for this mount */
  86         fsinfo.fattr = nfs_alloc_fattr();
  87         if (fsinfo.fattr == NULL)
  88                 return ERR_PTR(-ENOMEM);
  89
  90         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  91         if (error < 0) {
  92                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  93                 ret = ERR_PTR(error);
  94                 goto out;
  95         }
  96
  97         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
  98         if (IS_ERR(inode)) {
  99                 dprintk("nfs_get_root: get root inode failed\n");
 100                 ret = ERR_CAST(inode);
 101                 goto out;
 102         }
 103
 104         error = nfs_superblock_set_dummy_root(sb, inode);
 105         if (error != 0) {
 106                 ret = ERR_PTR(error);
 107                 goto out;
 108         }
 109
 110         /* root dentries normally start off anonymous and get spliced in later
 111          * if the dentry tree reaches them; however if the dentry already
 112          * exists, we'll pick it up at this point and use it as the root
 113          */
 114         ret = d_obtain_alias(inode);
 115         if (IS_ERR(ret)) {
 116                 dprintk("nfs_get_root: get root dentry failed\n");
 117                 goto out;
 118         }
 119
 120         security_d_instantiate(ret, inode);
 121
 122         if (ret->d_op == NULL)
 123                 ret->d_op = server->nfs_client->rpc_ops->dentry_ops;
 124 out:
 125         nfs_free_fattr(fsinfo.fattr);
 126         return ret;
 127 }
 128
 129 #ifdef CONFIG_NFS_V4
 130
 131 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 132 {
 133         struct nfs_fsinfo fsinfo;
 134         int ret = -ENOMEM;
 135
 136         dprintk("--> nfs4_get_rootfh()\n");
 137
 138         fsinfo.fattr = nfs_alloc_fattr();
 139         if (fsinfo.fattr == NULL)
 140                 goto out;
 141
 142         /* Start by getting the root filehandle from the server */
 143         ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
 144         if (ret < 0) {
 145                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 146                 goto out;
 147         }
 148
 149         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_MODE)
 150                         || !S_ISDIR(fsinfo.fattr->mode)) {
 151                 printk(KERN_ERR "nfs4_get_rootfh:"
 152                        " getroot encountered non-directory\n");
 153                 ret = -ENOTDIR;
 154                 goto out;
 155         }
 156
 157         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 158                 printk(KERN_ERR "nfs4_get_rootfh:"
 159                        " getroot obtained referral\n");
 160                 ret = -EREMOTE;
 161                 goto out;
 162         }
 163
 164         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 165 out:
 166         nfs_free_fattr(fsinfo.fattr);
 167         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 168         return ret;
 169 }
 170
 171 /*
 172  * get an NFS4 root dentry from the root filehandle
 173  */
 174 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh)
 175 {
 176         struct nfs_server *server = NFS_SB(sb);
 177         struct nfs_fattr *fattr = NULL;
 178         struct dentry *ret;
 179         struct inode *inode;
 180         int error;
 181
 182         dprintk("--> nfs4_get_root()\n");
 183
 184         /* get the info about the server and filesystem */
 185         error = nfs4_server_capabilities(server, mntfh);
 186         if (error < 0) {
 187                 dprintk("nfs_get_root: getcaps error = %d\n",
 188                         -error);
 189                 return ERR_PTR(error);
 190         }
 191
 192         fattr = nfs_alloc_fattr();
 193         if (fattr == NULL)
 194                 return ERR_PTR(-ENOMEM);;
 195
 196         /* get the actual root for this mount */
 197         error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr);
 198         if (error < 0) {
 199                 dprintk("nfs_get_root: getattr error = %d\n", -error);
 200                 ret = ERR_PTR(error);
 201                 goto out;
 202         }
 203
 204         inode = nfs_fhget(sb, mntfh, fattr);
 205         if (IS_ERR(inode)) {
 206                 dprintk("nfs_get_root: get root inode failed\n");
 207                 ret = ERR_CAST(inode);
 208                 goto out;
 209         }
 210
 211         error = nfs_superblock_set_dummy_root(sb, inode);
 212         if (error != 0) {
 213                 ret = ERR_PTR(error);
 214                 goto out;
 215         }
 216
 217         /* root dentries normally start off anonymous and get spliced in later
 218          * if the dentry tree reaches them; however if the dentry already
 219          * exists, we'll pick it up at this point and use it as the root
 220          */
 221         ret = d_obtain_alias(inode);
 222         if (IS_ERR(ret)) {
 223                 dprintk("nfs_get_root: get root dentry failed\n");
 224                 goto out;
 225         }
 226
 227         security_d_instantiate(ret, inode);
 228
 229         if (ret->d_op == NULL)
 230                 ret->d_op = server->nfs_client->rpc_ops->dentry_ops;
 231
 232 out:
 233         nfs_free_fattr(fattr);
 234         dprintk("<-- nfs4_get_root()\n");
 235         return ret;
 236 }
 237
 238 #endif /* CONFIG_NFS_V4 */