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 */ 234