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 */ 238