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 "internal.h" 19 20 #define NFSDBG_FACILITY NFSDBG_VFS 21 22 static void nfs_expire_automounts(struct work_struct *work); 23 24 static LIST_HEAD(nfs_automount_list); 25 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 26 int nfs_mountpoint_expiry_timeout = 500 * HZ; 27 28 static struct vfsmount *nfs_do_submount(struct dentry *dentry, 29 struct nfs_fh *fh, 30 struct nfs_fattr *fattr); 31 32 /* 33 * nfs_path - reconstruct the path given an arbitrary dentry 34 * @base - used to return pointer to the end of devname part of path 35 * @dentry - pointer to dentry 36 * @buffer - result buffer 37 * @buflen - length of buffer 38 * 39 * Helper function for constructing the server pathname 40 * by arbitrary hashed dentry. 41 * 42 * This is mainly for use in figuring out the path on the 43 * server side when automounting on top of an existing partition 44 * and in generating /proc/mounts and friends. 45 */ 46 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen) 47 { 48 char *end; 49 int namelen; 50 unsigned seq; 51 const char *base; 52 53 rename_retry: 54 end = buffer+buflen; 55 *--end = '\0'; 56 buflen--; 57 58 seq = read_seqbegin(&rename_lock); 59 rcu_read_lock(); 60 while (1) { 61 spin_lock(&dentry->d_lock); 62 if (IS_ROOT(dentry)) 63 break; 64 namelen = dentry->d_name.len; 65 buflen -= namelen + 1; 66 if (buflen < 0) 67 goto Elong_unlock; 68 end -= namelen; 69 memcpy(end, dentry->d_name.name, namelen); 70 *--end = '/'; 71 spin_unlock(&dentry->d_lock); 72 dentry = dentry->d_parent; 73 } 74 if (read_seqretry(&rename_lock, seq)) { 75 spin_unlock(&dentry->d_lock); 76 rcu_read_unlock(); 77 goto rename_retry; 78 } 79 if (*end != '/') { 80 if (--buflen < 0) { 81 spin_unlock(&dentry->d_lock); 82 rcu_read_unlock(); 83 goto Elong; 84 } 85 *--end = '/'; 86 } 87 *p = end; 88 base = dentry->d_fsdata; 89 if (!base) { 90 spin_unlock(&dentry->d_lock); 91 rcu_read_unlock(); 92 WARN_ON(1); 93 return end; 94 } 95 namelen = strlen(base); 96 /* Strip off excess slashes in base string */ 97 while (namelen > 0 && base[namelen - 1] == '/') 98 namelen--; 99 buflen -= namelen; 100 if (buflen < 0) { 101 spin_unlock(&dentry->d_lock); 102 rcu_read_unlock(); 103 goto Elong; 104 } 105 end -= namelen; 106 memcpy(end, base, namelen); 107 spin_unlock(&dentry->d_lock); 108 rcu_read_unlock(); 109 return end; 110 Elong_unlock: 111 spin_unlock(&dentry->d_lock); 112 rcu_read_unlock(); 113 if (read_seqretry(&rename_lock, seq)) 114 goto rename_retry; 115 Elong: 116 return ERR_PTR(-ENAMETOOLONG); 117 } 118 119 /* 120 * nfs_d_automount - Handle crossing a mountpoint on the server 121 * @path - The mountpoint 122 * 123 * When we encounter a mountpoint on the server, we want to set up 124 * a mountpoint on the client too, to prevent inode numbers from 125 * colliding, and to allow "df" to work properly. 126 * On NFSv4, we also want to allow for the fact that different 127 * filesystems may be migrated to different servers in a failover 128 * situation, and that different filesystems may want to use 129 * different security flavours. 130 */ 131 struct vfsmount *nfs_d_automount(struct path *path) 132 { 133 struct vfsmount *mnt; 134 struct nfs_server *server = NFS_SERVER(path->dentry->d_inode); 135 struct dentry *parent; 136 struct nfs_fh *fh = NULL; 137 struct nfs_fattr *fattr = NULL; 138 int err; 139 140 dprintk("--> nfs_d_automount()\n"); 141 142 mnt = ERR_PTR(-ESTALE); 143 if (IS_ROOT(path->dentry)) 144 goto out_nofree; 145 146 mnt = ERR_PTR(-ENOMEM); 147 fh = nfs_alloc_fhandle(); 148 fattr = nfs_alloc_fattr(); 149 if (fh == NULL || fattr == NULL) 150 goto out; 151 152 dprintk("%s: enter\n", __func__); 153 154 /* Look it up again to get its attributes */ 155 parent = dget_parent(path->dentry); 156 err = server->nfs_client->rpc_ops->lookup(parent->d_inode, 157 &path->dentry->d_name, 158 fh, fattr); 159 dput(parent); 160 if (err != 0) { 161 mnt = ERR_PTR(err); 162 goto out; 163 } 164 165 if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL) 166 mnt = nfs_do_refmount(path->dentry); 167 else 168 mnt = nfs_do_submount(path->dentry, fh, fattr); 169 if (IS_ERR(mnt)) 170 goto out; 171 172 dprintk("%s: done, success\n", __func__); 173 mntget(mnt); /* prevent immediate expiration */ 174 mnt_set_expiry(mnt, &nfs_automount_list); 175 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 176 177 out: 178 nfs_free_fattr(fattr); 179 nfs_free_fhandle(fh); 180 out_nofree: 181 dprintk("<-- nfs_follow_mountpoint() = %p\n", mnt); 182 return mnt; 183 } 184 185 const struct inode_operations nfs_mountpoint_inode_operations = { 186 .getattr = nfs_getattr, 187 }; 188 189 const struct inode_operations nfs_referral_inode_operations = { 190 }; 191 192 static void nfs_expire_automounts(struct work_struct *work) 193 { 194 struct list_head *list = &nfs_automount_list; 195 196 mark_mounts_for_expiry(list); 197 if (!list_empty(list)) 198 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 199 } 200 201 void nfs_release_automount_timer(void) 202 { 203 if (list_empty(&nfs_automount_list)) 204 cancel_delayed_work(&nfs_automount_task); 205 } 206 207 /* 208 * Clone a mountpoint of the appropriate type 209 */ 210 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 211 const char *devname, 212 struct nfs_clone_mount *mountdata) 213 { 214 #ifdef CONFIG_NFS_V4 215 struct vfsmount *mnt = ERR_PTR(-EINVAL); 216 switch (server->nfs_client->rpc_ops->version) { 217 case 2: 218 case 3: 219 mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 220 break; 221 case 4: 222 mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); 223 } 224 return mnt; 225 #else 226 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 227 #endif 228 } 229 230 /** 231 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 232 * @dentry - parent directory 233 * @fh - filehandle for new root dentry 234 * @fattr - attributes for new root inode 235 * 236 */ 237 static struct vfsmount *nfs_do_submount(struct dentry *dentry, 238 struct nfs_fh *fh, 239 struct nfs_fattr *fattr) 240 { 241 struct nfs_clone_mount mountdata = { 242 .sb = dentry->d_sb, 243 .dentry = dentry, 244 .fh = fh, 245 .fattr = fattr, 246 }; 247 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 248 char *page = (char *) __get_free_page(GFP_USER); 249 char *devname; 250 251 dprintk("--> nfs_do_submount()\n"); 252 253 dprintk("%s: submounting on %s/%s\n", __func__, 254 dentry->d_parent->d_name.name, 255 dentry->d_name.name); 256 if (page == NULL) 257 goto out; 258 devname = nfs_devname(dentry, page, PAGE_SIZE); 259 mnt = (struct vfsmount *)devname; 260 if (IS_ERR(devname)) 261 goto free_page; 262 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); 263 free_page: 264 free_page((unsigned long)page); 265 out: 266 dprintk("%s: done\n", __func__); 267 268 dprintk("<-- nfs_do_submount() = %p\n", mnt); 269 return mnt; 270 } 271