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/dcache.h> 11 #include <linux/gfp.h> 12 #include <linux/mount.h> 13 #include <linux/namei.h> 14 #include <linux/nfs_fs.h> 15 #include <linux/string.h> 16 #include <linux/sunrpc/clnt.h> 17 #include <linux/vfs.h> 18 #include <linux/sunrpc/gss_api.h> 19 #include "internal.h" 20 21 #define NFSDBG_FACILITY NFSDBG_VFS 22 23 static void nfs_expire_automounts(struct work_struct *work); 24 25 static LIST_HEAD(nfs_automount_list); 26 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 27 int nfs_mountpoint_expiry_timeout = 500 * HZ; 28 29 /* 30 * nfs_path - reconstruct the path given an arbitrary dentry 31 * @base - used to return pointer to the end of devname part of path 32 * @dentry - pointer to dentry 33 * @buffer - result buffer 34 * @buflen - length of buffer 35 * 36 * Helper function for constructing the server pathname 37 * by arbitrary hashed dentry. 38 * 39 * This is mainly for use in figuring out the path on the 40 * server side when automounting on top of an existing partition 41 * and in generating /proc/mounts and friends. 42 */ 43 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen) 44 { 45 char *end; 46 int namelen; 47 unsigned seq; 48 const char *base; 49 50 rename_retry: 51 end = buffer+buflen; 52 *--end = '\0'; 53 buflen--; 54 55 seq = read_seqbegin(&rename_lock); 56 rcu_read_lock(); 57 while (1) { 58 spin_lock(&dentry->d_lock); 59 if (IS_ROOT(dentry)) 60 break; 61 namelen = dentry->d_name.len; 62 buflen -= namelen + 1; 63 if (buflen < 0) 64 goto Elong_unlock; 65 end -= namelen; 66 memcpy(end, dentry->d_name.name, namelen); 67 *--end = '/'; 68 spin_unlock(&dentry->d_lock); 69 dentry = dentry->d_parent; 70 } 71 if (read_seqretry(&rename_lock, seq)) { 72 spin_unlock(&dentry->d_lock); 73 rcu_read_unlock(); 74 goto rename_retry; 75 } 76 if (*end != '/') { 77 if (--buflen < 0) { 78 spin_unlock(&dentry->d_lock); 79 rcu_read_unlock(); 80 goto Elong; 81 } 82 *--end = '/'; 83 } 84 *p = end; 85 base = dentry->d_fsdata; 86 if (!base) { 87 spin_unlock(&dentry->d_lock); 88 rcu_read_unlock(); 89 WARN_ON(1); 90 return end; 91 } 92 namelen = strlen(base); 93 /* Strip off excess slashes in base string */ 94 while (namelen > 0 && base[namelen - 1] == '/') 95 namelen--; 96 buflen -= namelen; 97 if (buflen < 0) { 98 spin_unlock(&dentry->d_lock); 99 rcu_read_unlock(); 100 goto Elong; 101 } 102 end -= namelen; 103 memcpy(end, base, namelen); 104 spin_unlock(&dentry->d_lock); 105 rcu_read_unlock(); 106 return end; 107 Elong_unlock: 108 spin_unlock(&dentry->d_lock); 109 rcu_read_unlock(); 110 if (read_seqretry(&rename_lock, seq)) 111 goto rename_retry; 112 Elong: 113 return ERR_PTR(-ENAMETOOLONG); 114 } 115 116 /* 117 * nfs_d_automount - Handle crossing a mountpoint on the server 118 * @path - The mountpoint 119 * 120 * When we encounter a mountpoint on the server, we want to set up 121 * a mountpoint on the client too, to prevent inode numbers from 122 * colliding, and to allow "df" to work properly. 123 * On NFSv4, we also want to allow for the fact that different 124 * filesystems may be migrated to different servers in a failover 125 * situation, and that different filesystems may want to use 126 * different security flavours. 127 */ 128 struct vfsmount *nfs_d_automount(struct path *path) 129 { 130 struct vfsmount *mnt; 131 struct nfs_server *server = NFS_SERVER(path->dentry->d_inode); 132 struct nfs_fh *fh = NULL; 133 struct nfs_fattr *fattr = NULL; 134 135 dprintk("--> nfs_d_automount()\n"); 136 137 mnt = ERR_PTR(-ESTALE); 138 if (IS_ROOT(path->dentry)) 139 goto out_nofree; 140 141 mnt = ERR_PTR(-ENOMEM); 142 fh = nfs_alloc_fhandle(); 143 fattr = nfs_alloc_fattr(); 144 if (fh == NULL || fattr == NULL) 145 goto out; 146 147 dprintk("%s: enter\n", __func__); 148 149 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr); 150 if (IS_ERR(mnt)) 151 goto out; 152 153 dprintk("%s: done, success\n", __func__); 154 mntget(mnt); /* prevent immediate expiration */ 155 mnt_set_expiry(mnt, &nfs_automount_list); 156 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 157 158 out: 159 nfs_free_fattr(fattr); 160 nfs_free_fhandle(fh); 161 out_nofree: 162 if (IS_ERR(mnt)) 163 dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt)); 164 else 165 dprintk("<-- %s() = %p\n", __func__, mnt); 166 return mnt; 167 } 168 169 const struct inode_operations nfs_mountpoint_inode_operations = { 170 .getattr = nfs_getattr, 171 }; 172 173 const struct inode_operations nfs_referral_inode_operations = { 174 }; 175 176 static void nfs_expire_automounts(struct work_struct *work) 177 { 178 struct list_head *list = &nfs_automount_list; 179 180 mark_mounts_for_expiry(list); 181 if (!list_empty(list)) 182 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 183 } 184 185 void nfs_release_automount_timer(void) 186 { 187 if (list_empty(&nfs_automount_list)) 188 cancel_delayed_work(&nfs_automount_task); 189 } 190 191 /* 192 * Clone a mountpoint of the appropriate type 193 */ 194 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 195 const char *devname, 196 struct nfs_clone_mount *mountdata) 197 { 198 #ifdef CONFIG_NFS_V4 199 struct vfsmount *mnt = ERR_PTR(-EINVAL); 200 switch (server->nfs_client->rpc_ops->version) { 201 case 2: 202 case 3: 203 mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 204 break; 205 case 4: 206 mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); 207 } 208 return mnt; 209 #else 210 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 211 #endif 212 } 213 214 /** 215 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 216 * @dentry - parent directory 217 * @fh - filehandle for new root dentry 218 * @fattr - attributes for new root inode 219 * @authflavor - security flavor to use when performing the mount 220 * 221 */ 222 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, 223 struct nfs_fattr *fattr, rpc_authflavor_t authflavor) 224 { 225 struct nfs_clone_mount mountdata = { 226 .sb = dentry->d_sb, 227 .dentry = dentry, 228 .fh = fh, 229 .fattr = fattr, 230 .authflavor = authflavor, 231 }; 232 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 233 char *page = (char *) __get_free_page(GFP_USER); 234 char *devname; 235 236 dprintk("--> nfs_do_submount()\n"); 237 238 dprintk("%s: submounting on %s/%s\n", __func__, 239 dentry->d_parent->d_name.name, 240 dentry->d_name.name); 241 if (page == NULL) 242 goto out; 243 devname = nfs_devname(dentry, page, PAGE_SIZE); 244 mnt = (struct vfsmount *)devname; 245 if (IS_ERR(devname)) 246 goto free_page; 247 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); 248 free_page: 249 free_page((unsigned long)page); 250 out: 251 dprintk("%s: done\n", __func__); 252 253 dprintk("<-- nfs_do_submount() = %p\n", mnt); 254 return mnt; 255 } 256 257 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry, 258 struct nfs_fh *fh, struct nfs_fattr *fattr) 259 { 260 int err; 261 struct dentry *parent = dget_parent(dentry); 262 263 /* Look it up again to get its attributes */ 264 err = server->nfs_client->rpc_ops->lookup(parent->d_inode, &dentry->d_name, fh, fattr); 265 dput(parent); 266 if (err != 0) 267 return ERR_PTR(err); 268 269 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor); 270 } 271