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