1 /* 2 * linux/fs/nfs/namespace.c 3 * 4 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> 5 * - Modified by David Howells <dhowells@redhat.com> 6 * 7 * NFS namespace 8 */ 9 10 #include <linux/module.h> 11 #include <linux/dcache.h> 12 #include <linux/gfp.h> 13 #include <linux/mount.h> 14 #include <linux/namei.h> 15 #include <linux/nfs_fs.h> 16 #include <linux/string.h> 17 #include <linux/sunrpc/clnt.h> 18 #include <linux/vfs.h> 19 #include <linux/sunrpc/gss_api.h> 20 #include "internal.h" 21 22 #define NFSDBG_FACILITY NFSDBG_VFS 23 24 static void nfs_expire_automounts(struct work_struct *work); 25 26 static LIST_HEAD(nfs_automount_list); 27 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 28 int nfs_mountpoint_expiry_timeout = 500 * HZ; 29 30 /* 31 * nfs_path - reconstruct the path given an arbitrary dentry 32 * @base - used to return pointer to the end of devname part of path 33 * @dentry - pointer to dentry 34 * @buffer - result buffer 35 * @buflen - length of buffer 36 * @flags - options (see below) 37 * 38 * Helper function for constructing the server pathname 39 * by arbitrary hashed dentry. 40 * 41 * This is mainly for use in figuring out the path on the 42 * server side when automounting on top of an existing partition 43 * and in generating /proc/mounts and friends. 44 * 45 * Supported flags: 46 * NFS_PATH_CANONICAL: ensure there is exactly one slash after 47 * the original device (export) name 48 * (if unset, the original name is returned verbatim) 49 */ 50 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen, 51 unsigned flags) 52 { 53 char *end; 54 int namelen; 55 unsigned seq; 56 const char *base; 57 58 rename_retry: 59 end = buffer+buflen; 60 *--end = '\0'; 61 buflen--; 62 63 seq = read_seqbegin(&rename_lock); 64 rcu_read_lock(); 65 while (1) { 66 spin_lock(&dentry->d_lock); 67 if (IS_ROOT(dentry)) 68 break; 69 namelen = dentry->d_name.len; 70 buflen -= namelen + 1; 71 if (buflen < 0) 72 goto Elong_unlock; 73 end -= namelen; 74 memcpy(end, dentry->d_name.name, namelen); 75 *--end = '/'; 76 spin_unlock(&dentry->d_lock); 77 dentry = dentry->d_parent; 78 } 79 if (read_seqretry(&rename_lock, seq)) { 80 spin_unlock(&dentry->d_lock); 81 rcu_read_unlock(); 82 goto rename_retry; 83 } 84 if ((flags & NFS_PATH_CANONICAL) && *end != '/') { 85 if (--buflen < 0) { 86 spin_unlock(&dentry->d_lock); 87 rcu_read_unlock(); 88 goto Elong; 89 } 90 *--end = '/'; 91 } 92 *p = end; 93 base = dentry->d_fsdata; 94 if (!base) { 95 spin_unlock(&dentry->d_lock); 96 rcu_read_unlock(); 97 WARN_ON(1); 98 return end; 99 } 100 namelen = strlen(base); 101 if (flags & NFS_PATH_CANONICAL) { 102 /* Strip off excess slashes in base string */ 103 while (namelen > 0 && base[namelen - 1] == '/') 104 namelen--; 105 } 106 buflen -= namelen; 107 if (buflen < 0) { 108 spin_unlock(&dentry->d_lock); 109 rcu_read_unlock(); 110 goto Elong; 111 } 112 end -= namelen; 113 memcpy(end, base, namelen); 114 spin_unlock(&dentry->d_lock); 115 rcu_read_unlock(); 116 return end; 117 Elong_unlock: 118 spin_unlock(&dentry->d_lock); 119 rcu_read_unlock(); 120 if (read_seqretry(&rename_lock, seq)) 121 goto rename_retry; 122 Elong: 123 return ERR_PTR(-ENAMETOOLONG); 124 } 125 EXPORT_SYMBOL_GPL(nfs_path); 126 127 /* 128 * nfs_d_automount - Handle crossing a mountpoint on the server 129 * @path - The mountpoint 130 * 131 * When we encounter a mountpoint on the server, we want to set up 132 * a mountpoint on the client too, to prevent inode numbers from 133 * colliding, and to allow "df" to work properly. 134 * On NFSv4, we also want to allow for the fact that different 135 * filesystems may be migrated to different servers in a failover 136 * situation, and that different filesystems may want to use 137 * different security flavours. 138 */ 139 struct vfsmount *nfs_d_automount(struct path *path) 140 { 141 struct vfsmount *mnt; 142 struct nfs_server *server = NFS_SERVER(path->dentry->d_inode); 143 struct nfs_fh *fh = NULL; 144 struct nfs_fattr *fattr = NULL; 145 146 dprintk("--> nfs_d_automount()\n"); 147 148 mnt = ERR_PTR(-ESTALE); 149 if (IS_ROOT(path->dentry)) 150 goto out_nofree; 151 152 mnt = ERR_PTR(-ENOMEM); 153 fh = nfs_alloc_fhandle(); 154 fattr = nfs_alloc_fattr(); 155 if (fh == NULL || fattr == NULL) 156 goto out; 157 158 dprintk("%s: enter\n", __func__); 159 160 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr); 161 if (IS_ERR(mnt)) 162 goto out; 163 164 dprintk("%s: done, success\n", __func__); 165 mntget(mnt); /* prevent immediate expiration */ 166 mnt_set_expiry(mnt, &nfs_automount_list); 167 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 168 169 out: 170 nfs_free_fattr(fattr); 171 nfs_free_fhandle(fh); 172 out_nofree: 173 if (IS_ERR(mnt)) 174 dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt)); 175 else 176 dprintk("<-- %s() = %p\n", __func__, mnt); 177 return mnt; 178 } 179 180 static int 181 nfs_namespace_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat) 182 { 183 if (NFS_FH(dentry->d_inode)->size != 0) 184 return nfs_getattr(mnt, dentry, stat); 185 generic_fillattr(dentry->d_inode, stat); 186 return 0; 187 } 188 189 static int 190 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) 191 { 192 if (NFS_FH(dentry->d_inode)->size != 0) 193 return nfs_setattr(dentry, attr); 194 return -EACCES; 195 } 196 197 const struct inode_operations nfs_mountpoint_inode_operations = { 198 .getattr = nfs_getattr, 199 .setattr = nfs_setattr, 200 }; 201 202 const struct inode_operations nfs_referral_inode_operations = { 203 .getattr = nfs_namespace_getattr, 204 .setattr = nfs_namespace_setattr, 205 }; 206 207 static void nfs_expire_automounts(struct work_struct *work) 208 { 209 struct list_head *list = &nfs_automount_list; 210 211 mark_mounts_for_expiry(list); 212 if (!list_empty(list)) 213 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 214 } 215 216 void nfs_release_automount_timer(void) 217 { 218 if (list_empty(&nfs_automount_list)) 219 cancel_delayed_work(&nfs_automount_task); 220 } 221 222 /* 223 * Clone a mountpoint of the appropriate type 224 */ 225 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 226 const char *devname, 227 struct nfs_clone_mount *mountdata) 228 { 229 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 230 } 231 232 /** 233 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 234 * @dentry - parent directory 235 * @fh - filehandle for new root dentry 236 * @fattr - attributes for new root inode 237 * @authflavor - security flavor to use when performing the mount 238 * 239 */ 240 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, 241 struct nfs_fattr *fattr, rpc_authflavor_t authflavor) 242 { 243 struct nfs_clone_mount mountdata = { 244 .sb = dentry->d_sb, 245 .dentry = dentry, 246 .fh = fh, 247 .fattr = fattr, 248 .authflavor = authflavor, 249 }; 250 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 251 char *page = (char *) __get_free_page(GFP_USER); 252 char *devname; 253 254 dprintk("--> nfs_do_submount()\n"); 255 256 dprintk("%s: submounting on %pd2\n", __func__, 257 dentry); 258 if (page == NULL) 259 goto out; 260 devname = nfs_devname(dentry, page, PAGE_SIZE); 261 mnt = (struct vfsmount *)devname; 262 if (IS_ERR(devname)) 263 goto free_page; 264 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); 265 free_page: 266 free_page((unsigned long)page); 267 out: 268 dprintk("%s: done\n", __func__); 269 270 dprintk("<-- nfs_do_submount() = %p\n", mnt); 271 return mnt; 272 } 273 EXPORT_SYMBOL_GPL(nfs_do_submount); 274 275 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry, 276 struct nfs_fh *fh, struct nfs_fattr *fattr) 277 { 278 int err; 279 struct dentry *parent = dget_parent(dentry); 280 281 /* Look it up again to get its attributes */ 282 err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr, NULL); 283 dput(parent); 284 if (err != 0) 285 return ERR_PTR(err); 286 287 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor); 288 } 289 EXPORT_SYMBOL_GPL(nfs_submount); 290