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/mount.h> 12 #include <linux/namei.h> 13 #include <linux/nfs_fs.h> 14 #include <linux/string.h> 15 #include <linux/sunrpc/clnt.h> 16 #include <linux/vfs.h> 17 #include "internal.h" 18 19 #define NFSDBG_FACILITY NFSDBG_VFS 20 21 static void nfs_expire_automounts(struct work_struct *work); 22 23 static LIST_HEAD(nfs_automount_list); 24 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 25 int nfs_mountpoint_expiry_timeout = 500 * HZ; 26 27 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, 28 const 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 - arbitrary string to prepend to the path 35 * @droot - pointer to root dentry for mountpoint 36 * @dentry - pointer to dentry 37 * @buffer - result buffer 38 * @buflen - length of buffer 39 * 40 * Helper function for constructing the path from the 41 * root dentry to an arbitrary hashed dentry. 42 * 43 * This is mainly for use in figuring out the path on the 44 * server side when automounting on top of an existing partition. 45 */ 46 char *nfs_path(const char *base, 47 const struct dentry *droot, 48 const struct dentry *dentry, 49 char *buffer, ssize_t buflen) 50 { 51 char *end = buffer+buflen; 52 int namelen; 53 54 *--end = '\0'; 55 buflen--; 56 spin_lock(&dcache_lock); 57 while (!IS_ROOT(dentry) && dentry != droot) { 58 namelen = dentry->d_name.len; 59 buflen -= namelen + 1; 60 if (buflen < 0) 61 goto Elong_unlock; 62 end -= namelen; 63 memcpy(end, dentry->d_name.name, namelen); 64 *--end = '/'; 65 dentry = dentry->d_parent; 66 } 67 spin_unlock(&dcache_lock); 68 if (*end != '/') { 69 if (--buflen < 0) 70 goto Elong; 71 *--end = '/'; 72 } 73 namelen = strlen(base); 74 /* Strip off excess slashes in base string */ 75 while (namelen > 0 && base[namelen - 1] == '/') 76 namelen--; 77 buflen -= namelen; 78 if (buflen < 0) 79 goto Elong; 80 end -= namelen; 81 memcpy(end, base, namelen); 82 return end; 83 Elong_unlock: 84 spin_unlock(&dcache_lock); 85 Elong: 86 return ERR_PTR(-ENAMETOOLONG); 87 } 88 89 /* 90 * nfs_follow_mountpoint - handle crossing a mountpoint on the server 91 * @dentry - dentry of mountpoint 92 * @nd - nameidata info 93 * 94 * When we encounter a mountpoint on the server, we want to set up 95 * a mountpoint on the client too, to prevent inode numbers from 96 * colliding, and to allow "df" to work properly. 97 * On NFSv4, we also want to allow for the fact that different 98 * filesystems may be migrated to different servers in a failover 99 * situation, and that different filesystems may want to use 100 * different security flavours. 101 */ 102 static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd) 103 { 104 struct vfsmount *mnt; 105 struct nfs_server *server = NFS_SERVER(dentry->d_inode); 106 struct dentry *parent; 107 struct nfs_fh fh; 108 struct nfs_fattr fattr; 109 int err; 110 111 dprintk("--> nfs_follow_mountpoint()\n"); 112 113 err = -ESTALE; 114 if (IS_ROOT(dentry)) 115 goto out_err; 116 117 dprintk("%s: enter\n", __func__); 118 dput(nd->path.dentry); 119 nd->path.dentry = dget(dentry); 120 121 /* Look it up again */ 122 parent = dget_parent(nd->path.dentry); 123 err = server->nfs_client->rpc_ops->lookup(parent->d_inode, 124 &nd->path.dentry->d_name, 125 &fh, &fattr); 126 dput(parent); 127 if (err != 0) 128 goto out_err; 129 130 if (fattr.valid & NFS_ATTR_FATTR_V4_REFERRAL) 131 mnt = nfs_do_refmount(nd->path.mnt, nd->path.dentry); 132 else 133 mnt = nfs_do_submount(nd->path.mnt, nd->path.dentry, &fh, 134 &fattr); 135 err = PTR_ERR(mnt); 136 if (IS_ERR(mnt)) 137 goto out_err; 138 139 mntget(mnt); 140 err = do_add_mount(mnt, &nd->path, nd->path.mnt->mnt_flags|MNT_SHRINKABLE, 141 &nfs_automount_list); 142 if (err < 0) { 143 mntput(mnt); 144 if (err == -EBUSY) 145 goto out_follow; 146 goto out_err; 147 } 148 path_put(&nd->path); 149 nd->path.mnt = mnt; 150 nd->path.dentry = dget(mnt->mnt_root); 151 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 152 out: 153 dprintk("%s: done, returned %d\n", __func__, err); 154 155 dprintk("<-- nfs_follow_mountpoint() = %d\n", err); 156 return ERR_PTR(err); 157 out_err: 158 path_put(&nd->path); 159 goto out; 160 out_follow: 161 while (d_mountpoint(nd->path.dentry) && 162 follow_down(&nd->path)) 163 ; 164 err = 0; 165 goto out; 166 } 167 168 const struct inode_operations nfs_mountpoint_inode_operations = { 169 .follow_link = nfs_follow_mountpoint, 170 .getattr = nfs_getattr, 171 }; 172 173 const struct inode_operations nfs_referral_inode_operations = { 174 .follow_link = nfs_follow_mountpoint, 175 }; 176 177 static void nfs_expire_automounts(struct work_struct *work) 178 { 179 struct list_head *list = &nfs_automount_list; 180 181 mark_mounts_for_expiry(list); 182 if (!list_empty(list)) 183 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 184 } 185 186 void nfs_release_automount_timer(void) 187 { 188 if (list_empty(&nfs_automount_list)) 189 cancel_delayed_work(&nfs_automount_task); 190 } 191 192 /* 193 * Clone a mountpoint of the appropriate type 194 */ 195 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 196 const char *devname, 197 struct nfs_clone_mount *mountdata) 198 { 199 #ifdef CONFIG_NFS_V4 200 struct vfsmount *mnt = ERR_PTR(-EINVAL); 201 switch (server->nfs_client->rpc_ops->version) { 202 case 2: 203 case 3: 204 mnt = vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 205 break; 206 case 4: 207 mnt = vfs_kern_mount(&nfs4_xdev_fs_type, 0, devname, mountdata); 208 } 209 return mnt; 210 #else 211 return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata); 212 #endif 213 } 214 215 /** 216 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 217 * @mnt_parent - mountpoint of parent directory 218 * @dentry - parent directory 219 * @fh - filehandle for new root dentry 220 * @fattr - attributes for new root inode 221 * 222 */ 223 static struct vfsmount *nfs_do_submount(const struct vfsmount *mnt_parent, 224 const struct dentry *dentry, 225 struct nfs_fh *fh, 226 struct nfs_fattr *fattr) 227 { 228 struct nfs_clone_mount mountdata = { 229 .sb = mnt_parent->mnt_sb, 230 .dentry = dentry, 231 .fh = fh, 232 .fattr = fattr, 233 }; 234 struct vfsmount *mnt = ERR_PTR(-ENOMEM); 235 char *page = (char *) __get_free_page(GFP_USER); 236 char *devname; 237 238 dprintk("--> nfs_do_submount()\n"); 239 240 dprintk("%s: submounting on %s/%s\n", __func__, 241 dentry->d_parent->d_name.name, 242 dentry->d_name.name); 243 if (page == NULL) 244 goto out; 245 devname = nfs_devname(mnt_parent, dentry, page, PAGE_SIZE); 246 mnt = (struct vfsmount *)devname; 247 if (IS_ERR(devname)) 248 goto free_page; 249 mnt = nfs_do_clone_mount(NFS_SB(mnt_parent->mnt_sb), devname, &mountdata); 250 free_page: 251 free_page((unsigned long)page); 252 out: 253 dprintk("%s: done\n", __func__); 254 255 dprintk("<-- nfs_do_submount() = %p\n", mnt); 256 return mnt; 257 } 258