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/uaccess.h>
  36
  37 #include "nfs4_fs.h"
  38 #include "delegation.h"
  39 #include "internal.h"
  40
  41 #define NFSDBG_FACILITY         NFSDBG_CLIENT
  42
  43 /*
  44  * Set the superblock root dentry.
  45  * Note that this function frees the inode in case of error.
  46  */
  47 static int nfs_superblock_set_dummy_root(struct super_block *sb, struct inode *inode)
  48 {
  49         /* The mntroot acts as the dummy root dentry for this superblock */
  50         if (sb->s_root == NULL) {
  51                 sb->s_root = d_make_root(inode);
  52                 if (sb->s_root == NULL)
  53                         return -ENOMEM;
  54                 ihold(inode);
  55                 /*
  56                  * Ensure that this dentry is invisible to d_find_alias().
  57                  * Otherwise, it may be spliced into the tree by
  58                  * d_materialise_unique if a parent directory from the same
  59                  * filesystem gets mounted at a later time.
  60                  * This again causes shrink_dcache_for_umount_subtree() to
  61                  * Oops, since the test for IS_ROOT() will fail.
  62                  */
  63                 spin_lock(&sb->s_root->d_inode->i_lock);
  64                 spin_lock(&sb->s_root->d_lock);
  65                 list_del_init(&sb->s_root->d_alias);
  66                 spin_unlock(&sb->s_root->d_lock);
  67                 spin_unlock(&sb->s_root->d_inode->i_lock);
  68         }
  69         return 0;
  70 }
  71
  72 /*
  73  * get an NFS2/NFS3 root dentry from the root filehandle
  74  */
  75 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh,
  76                             const char *devname)
  77 {
  78         struct nfs_server *server = NFS_SB(sb);
  79         struct nfs_fsinfo fsinfo;
  80         struct dentry *ret;
  81         struct inode *inode;
  82         void *name = kstrdup(devname, GFP_KERNEL);
  83         int error;
  84
  85         if (!name)
  86                 return ERR_PTR(-ENOMEM);
  87
  88         /* get the actual root for this mount */
  89         fsinfo.fattr = nfs_alloc_fattr();
  90         if (fsinfo.fattr == NULL) {
  91                 kfree(name);
  92                 return ERR_PTR(-ENOMEM);
  93         }
  94
  95         error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo);
  96         if (error < 0) {
  97                 dprintk("nfs_get_root: getattr error = %d\n", -error);
  98                 ret = ERR_PTR(error);
  99                 goto out;
 100         }
 101
 102         inode = nfs_fhget(sb, mntfh, fsinfo.fattr);
 103         if (IS_ERR(inode)) {
 104                 dprintk("nfs_get_root: get root inode failed\n");
 105                 ret = ERR_CAST(inode);
 106                 goto out;
 107         }
 108
 109         error = nfs_superblock_set_dummy_root(sb, inode);
 110         if (error != 0) {
 111                 ret = ERR_PTR(error);
 112                 goto out;
 113         }
 114
 115         /* root dentries normally start off anonymous and get spliced in later
 116          * if the dentry tree reaches them; however if the dentry already
 117          * exists, we'll pick it up at this point and use it as the root
 118          */
 119         ret = d_obtain_alias(inode);
 120         if (IS_ERR(ret)) {
 121                 dprintk("nfs_get_root: get root dentry failed\n");
 122                 goto out;
 123         }
 124
 125         security_d_instantiate(ret, inode);
 126         spin_lock(&ret->d_lock);
 127         if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) {
 128                 ret->d_fsdata = name;
 129                 name = NULL;
 130         }
 131         spin_unlock(&ret->d_lock);
 132 out:
 133         if (name)
 134                 kfree(name);
 135         nfs_free_fattr(fsinfo.fattr);
 136         return ret;
 137 }
 138
 139 #ifdef CONFIG_NFS_V4
 140
 141 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh)
 142 {
 143         struct nfs_fsinfo fsinfo;
 144         int ret = -ENOMEM;
 145
 146         dprintk("--> nfs4_get_rootfh()\n");
 147
 148         fsinfo.fattr = nfs_alloc_fattr();
 149         if (fsinfo.fattr == NULL)
 150                 goto out;
 151
 152         /* Start by getting the root filehandle from the server */
 153         ret = nfs4_proc_get_rootfh(server, mntfh, &fsinfo);
 154         if (ret < 0) {
 155                 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret);
 156                 goto out;
 157         }
 158
 159         if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE)
 160                         || !S_ISDIR(fsinfo.fattr->mode)) {
 161                 printk(KERN_ERR "nfs4_get_rootfh:"
 162                        " getroot encountered non-directory\n");
 163                 ret = -ENOTDIR;
 164                 goto out;
 165         }
 166
 167         if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) {
 168                 printk(KERN_ERR "nfs4_get_rootfh:"
 169                        " getroot obtained referral\n");
 170                 ret = -EREMOTE;
 171                 goto out;
 172         }
 173
 174         memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid));
 175 out:
 176         nfs_free_fattr(fsinfo.fattr);
 177         dprintk("<-- nfs4_get_rootfh() = %d\n", ret);
 178         return ret;
 179 }
 180
 181 #endif /* CONFIG_NFS_V4 */