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 /* Circumvent igrab(): we know the inode is not being freed */ 58 atomic_inc(&inode->i_count); 59 /* 60 * Ensure that this dentry is invisible to d_find_alias(). 61 * Otherwise, it may be spliced into the tree by 62 * d_materialise_unique if a parent directory from the same 63 * filesystem gets mounted at a later time. 64 * This again causes shrink_dcache_for_umount_subtree() to 65 * Oops, since the test for IS_ROOT() will fail. 66 */ 67 spin_lock(&dcache_lock); 68 list_del_init(&sb->s_root->d_alias); 69 spin_unlock(&dcache_lock); 70 } 71 return 0; 72 } 73 74 /* 75 * get an NFS2/NFS3 root dentry from the root filehandle 76 */ 77 struct dentry *nfs_get_root(struct super_block *sb, struct nfs_fh *mntfh) 78 { 79 struct nfs_server *server = NFS_SB(sb); 80 struct nfs_fsinfo fsinfo; 81 struct dentry *ret; 82 struct inode *inode; 83 int error; 84 85 /* get the actual root for this mount */ 86 fsinfo.fattr = nfs_alloc_fattr(); 87 if (fsinfo.fattr == NULL) 88 return ERR_PTR(-ENOMEM); 89 90 error = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 91 if (error < 0) { 92 dprintk("nfs_get_root: getattr error = %d\n", -error); 93 ret = ERR_PTR(error); 94 goto out; 95 } 96 97 inode = nfs_fhget(sb, mntfh, fsinfo.fattr); 98 if (IS_ERR(inode)) { 99 dprintk("nfs_get_root: get root inode failed\n"); 100 ret = ERR_CAST(inode); 101 goto out; 102 } 103 104 error = nfs_superblock_set_dummy_root(sb, inode); 105 if (error != 0) { 106 ret = ERR_PTR(error); 107 goto out; 108 } 109 110 /* root dentries normally start off anonymous and get spliced in later 111 * if the dentry tree reaches them; however if the dentry already 112 * exists, we'll pick it up at this point and use it as the root 113 */ 114 ret = d_obtain_alias(inode); 115 if (IS_ERR(ret)) { 116 dprintk("nfs_get_root: get root dentry failed\n"); 117 goto out; 118 } 119 120 security_d_instantiate(ret, inode); 121 122 if (ret->d_op == NULL) 123 ret->d_op = server->nfs_client->rpc_ops->dentry_ops; 124 out: 125 nfs_free_fattr(fsinfo.fattr); 126 return ret; 127 } 128 129 #ifdef CONFIG_NFS_V4 130 131 int nfs4_get_rootfh(struct nfs_server *server, struct nfs_fh *mntfh) 132 { 133 struct nfs_fsinfo fsinfo; 134 int ret = -ENOMEM; 135 136 dprintk("--> nfs4_get_rootfh()\n"); 137 138 fsinfo.fattr = nfs_alloc_fattr(); 139 if (fsinfo.fattr == NULL) 140 goto out; 141 142 /* Start by getting the root filehandle from the server */ 143 ret = server->nfs_client->rpc_ops->getroot(server, mntfh, &fsinfo); 144 if (ret < 0) { 145 dprintk("nfs4_get_rootfh: getroot error = %d\n", -ret); 146 goto out; 147 } 148 149 if (!(fsinfo.fattr->valid & NFS_ATTR_FATTR_MODE) 150 || !S_ISDIR(fsinfo.fattr->mode)) { 151 printk(KERN_ERR "nfs4_get_rootfh:" 152 " getroot encountered non-directory\n"); 153 ret = -ENOTDIR; 154 goto out; 155 } 156 157 if (fsinfo.fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) { 158 printk(KERN_ERR "nfs4_get_rootfh:" 159 " getroot obtained referral\n"); 160 ret = -EREMOTE; 161 goto out; 162 } 163 164 memcpy(&server->fsid, &fsinfo.fattr->fsid, sizeof(server->fsid)); 165 out: 166 nfs_free_fattr(fsinfo.fattr); 167 dprintk("<-- nfs4_get_rootfh() = %d\n", ret); 168 return ret; 169 } 170 171 /* 172 * get an NFS4 root dentry from the root filehandle 173 */ 174 struct dentry *nfs4_get_root(struct super_block *sb, struct nfs_fh *mntfh) 175 { 176 struct nfs_server *server = NFS_SB(sb); 177 struct nfs_fattr *fattr = NULL; 178 struct dentry *ret; 179 struct inode *inode; 180 int error; 181 182 dprintk("--> nfs4_get_root()\n"); 183 184 /* get the info about the server and filesystem */ 185 error = nfs4_server_capabilities(server, mntfh); 186 if (error < 0) { 187 dprintk("nfs_get_root: getcaps error = %d\n", 188 -error); 189 return ERR_PTR(error); 190 } 191 192 fattr = nfs_alloc_fattr(); 193 if (fattr == NULL) 194 return ERR_PTR(-ENOMEM);; 195 196 /* get the actual root for this mount */ 197 error = server->nfs_client->rpc_ops->getattr(server, mntfh, fattr); 198 if (error < 0) { 199 dprintk("nfs_get_root: getattr error = %d\n", -error); 200 ret = ERR_PTR(error); 201 goto out; 202 } 203 204 inode = nfs_fhget(sb, mntfh, fattr); 205 if (IS_ERR(inode)) { 206 dprintk("nfs_get_root: get root inode failed\n"); 207 ret = ERR_CAST(inode); 208 goto out; 209 } 210 211 error = nfs_superblock_set_dummy_root(sb, inode); 212 if (error != 0) { 213 ret = ERR_PTR(error); 214 goto out; 215 } 216 217 /* root dentries normally start off anonymous and get spliced in later 218 * if the dentry tree reaches them; however if the dentry already 219 * exists, we'll pick it up at this point and use it as the root 220 */ 221 ret = d_obtain_alias(inode); 222 if (IS_ERR(ret)) { 223 dprintk("nfs_get_root: get root dentry failed\n"); 224 goto out; 225 } 226 227 security_d_instantiate(ret, inode); 228 229 if (ret->d_op == NULL) 230 ret->d_op = server->nfs_client->rpc_ops->dentry_ops; 231 232 out: 233 nfs_free_fattr(fattr); 234 dprintk("<-- nfs4_get_root()\n"); 235 return ret; 236 } 237 238 #endif /* CONFIG_NFS_V4 */ 239