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 */ 182