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_make_root(inode); 53 if (sb->s_root == NULL) 54 return -ENOMEM; 55 ihold(inode); 56 /* 57 * Ensure that this dentry is invisible to d_find_alias(). 58 * Otherwise, it may be spliced into the tree by 59 * d_materialise_unique if a parent directory from the same 60 * filesystem gets mounted at a later time. 61 * This again causes shrink_dcache_for_umount_subtree() to 62 * Oops, since the test for IS_ROOT() will fail. 63 */ 64 spin_lock(&sb->s_root->d_inode->i_lock); 65 spin_lock(&sb->s_root->d_lock); 66 list_del_init(&sb->s_root->d_alias); 67 spin_unlock(&sb->s_root->d_lock); 68 spin_unlock(&sb->s_root->d_inode->i_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 const char *devname) 78 { 79 struct nfs_server *server = NFS_SB(sb); 80 struct nfs_fsinfo fsinfo; 81 struct dentry *ret; 82 struct inode *inode; 83 void *name = kstrdup(devname, GFP_KERNEL); 84 int error; 85 86 if (!name) 87 return ERR_PTR(-ENOMEM); 88 89 /* get the actual root for this mount */ 90 fsinfo.fattr = nfs_alloc_fattr(); 91 if (fsinfo.fattr == NULL) { 92 kfree(name); 93 return ERR_PTR(-ENOMEM); 94 } 95 96 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 97 if (error < 0) { 98 dprintk("nfs_get_root: getattr error = %d\n", -error); 99 ret = ERR_PTR(error); 100 goto out; 101 } 102 103 inode = nfs_fhget(sb, mntfh, fsinfo.fattr); 104 if (IS_ERR(inode)) { 105 dprintk("nfs_get_root: get root inode failed\n"); 106 ret = ERR_CAST(inode); 107 goto out; 108 } 109 110 error = nfs_superblock_set_dummy_root(sb, inode); 111 if (error != 0) { 112 ret = ERR_PTR(error); 113 goto out; 114 } 115 116 /* root dentries normally start off anonymous and get spliced in later 117 * if the dentry tree reaches them; however if the dentry already 118 * exists, we'll pick it up at this point and use it as the root 119 */ 120 ret = d_obtain_alias(inode); 121 if (IS_ERR(ret)) { 122 dprintk("nfs_get_root: get root dentry failed\n"); 123 goto out; 124 } 125 126 security_d_instantiate(ret, inode); 127 spin_lock(&ret->d_lock); 128 if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) { 129 ret->d_fsdata = name; 130 name = NULL; 131 } 132 spin_unlock(&ret->d_lock); 133 out: 134 if (name) 135 kfree(name); 136 nfs_free_fattr(fsinfo.fattr); 137 return ret; 138 } 139 140 #ifdef CONFIG_NFS_V4 141 142 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh) 143 { 144 struct nfs_fsinfo fsinfo; 145 int ret = -ENOMEM; 146 147 dprintk("--> nfs4_get_rootfh()\n"); 148 149 fsinfo.fattr = nfs_alloc_fattr(); 150 if (fsinfo.fattr == NULL) 151 goto out; 152 153 /* Start by getting the root filehandle from the server */ 154 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 155 if (ret < 0) { 156 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret); 157 goto out; 158 } 159 160 if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_TYPE) 161 || !S_ISDIR(fsinfo.fattr->mode)) { 162 printk(KERN_ERR "nfs4_get_rootfh:" 163 " getroot encountered non-directory\n"); 164 ret = -ENOTDIR; 165 goto out; 166 } 167 168 if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) { 169 printk(KERN_ERR "nfs4_get_rootfh:" 170 " getroot obtained referral\n"); 171 ret = -EREMOTE; 172 goto out; 173 } 174 175 memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid)); 176 out: 177 nfs_free_fattr(fsinfo.fattr); 178 dprintk("<-- nfs4_get_rootfh() = %d\n", ret); 179 return ret; 180 } 181 182 /* 183 * get an NFS4 root dentry from the root filehandle 184 */ 185 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh, 186 const char *devname) 187 { 188 struct nfs_server *server = NFS_SB(sb); 189 struct nfs_fattr *fattr = NULL; 190 struct dentry *ret; 191 struct inode *inode; 192 void *name = kstrdup(devname, GFP_KERNEL); 193 int error; 194 195 dprintk("--> nfs4_get_root()\n"); 196 197 if (!name) 198 return ERR_PTR(-ENOMEM); 199 200 /* get the info about the server and filesystem */ 201 error = nfs4_server_capabilities(server, mntfh); 202 if (error < 0) { 203 dprintk("nfs_get_root: getcaps error = %d\n", 204 -error); 205 kfree(name); 206 return ERR_PTR(error); 207 } 208 209 fattr = nfs_alloc_fattr(); 210 if (fattr == NULL) { 211 kfree(name); 212 return ERR_PTR(-ENOMEM); 213 } 214 215 /* get the actual root for this mount */ 216 error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr); 217 if (error < 0) { 218 dprintk("nfs_get_root: getattr error = %d\n", -error); 219 ret = ERR_PTR(error); 220 goto out; 221 } 222 223 if (fattr->valid & NFS_ATTR_FATTR_FSID && 224 !nfs_fsid_equal(&server->fsid, &fattr->fsid)) 225 memcpy(&server->fsid, &fattr->fsid, sizeof(server->fsid)); 226 227 inode = nfs_fhget(sb, mntfh, fattr); 228 if (IS_ERR(inode)) { 229 dprintk("nfs_get_root: get root inode failed\n"); 230 ret = ERR_CAST(inode); 231 goto out; 232 } 233 234 error = nfs_superblock_set_dummy_root(sb, inode); 235 if (error != 0) { 236 ret = ERR_PTR(error); 237 goto out; 238 } 239 240 /* root dentries normally start off anonymous and get spliced in later 241 * if the dentry tree reaches them; however if the dentry already 242 * exists, we'll pick it up at this point and use it as the root 243 */ 244 ret = d_obtain_alias(inode); 245 if (IS_ERR(ret)) { 246 dprintk("nfs_get_root: get root dentry failed\n"); 247 goto out; 248 } 249 250 security_d_instantiate(ret, inode); 251 spin_lock(&ret->d_lock); 252 if (IS_ROOT(ret) && !(ret->d_flags & DCACHE_NFSFS_RENAMED)) { 253 ret->d_fsdata = name; 254 name = NULL; 255 } 256 spin_unlock(&ret->d_lock); 257 out: 258 if (name) 259 kfree(name); 260 nfs_free_fattr(fattr); 261 dprintk("<-- nfs4_get_root()\n"); 262 return ret; 263 } 264 265 #endif /* CONFIG_NFS_V4 */ 266