1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/fs/nfs/namespace.c 4 * 5 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com> 6 * - Modified by David Howells <dhowells@redhat.com> 7 * 8 * NFS namespace 9 */ 10 11 #include <linux/module.h> 12 #include <linux/dcache.h> 13 #include <linux/gfp.h> 14 #include <linux/mount.h> 15 #include <linux/namei.h> 16 #include <linux/nfs_fs.h> 17 #include <linux/string.h> 18 #include <linux/sunrpc/clnt.h> 19 #include <linux/vfs.h> 20 #include <linux/sunrpc/gss_api.h> 21 #include "internal.h" 22 #include "nfs.h" 23 24 #define NFSDBG_FACILITY NFSDBG_VFS 25 26 static void nfs_expire_automounts(struct work_struct *work); 27 28 static LIST_HEAD(nfs_automount_list); 29 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 30 int nfs_mountpoint_expiry_timeout = 500 * HZ; 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 * @flags - options (see below) 39 * 40 * Helper function for constructing the server pathname 41 * by 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 * and in generating /proc/mounts and friends. 46 * 47 * Supported flags: 48 * NFS_PATH_CANONICAL: ensure there is exactly one slash after 49 * the original device (export) name 50 * (if unset, the original name is returned verbatim) 51 */ 52 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen, 53 unsigned flags) 54 { 55 char *end; 56 int namelen; 57 unsigned seq; 58 const char *base; 59 60 rename_retry: 61 end = buffer+buflen; 62 *--end = '\0'; 63 buflen--; 64 65 seq = read_seqbegin(&rename_lock); 66 rcu_read_lock(); 67 while (1) { 68 spin_lock(&dentry->d_lock); 69 if (IS_ROOT(dentry)) 70 break; 71 namelen = dentry->d_name.len; 72 buflen -= namelen + 1; 73 if (buflen < 0) 74 goto Elong_unlock; 75 end -= namelen; 76 memcpy(end, dentry->d_name.name, namelen); 77 *--end = '/'; 78 spin_unlock(&dentry->d_lock); 79 dentry = dentry->d_parent; 80 } 81 if (read_seqretry(&rename_lock, seq)) { 82 spin_unlock(&dentry->d_lock); 83 rcu_read_unlock(); 84 goto rename_retry; 85 } 86 if ((flags & NFS_PATH_CANONICAL) && *end != '/') { 87 if (--buflen < 0) { 88 spin_unlock(&dentry->d_lock); 89 rcu_read_unlock(); 90 goto Elong; 91 } 92 *--end = '/'; 93 } 94 *p = end; 95 base = dentry->d_fsdata; 96 if (!base) { 97 spin_unlock(&dentry->d_lock); 98 rcu_read_unlock(); 99 WARN_ON(1); 100 return end; 101 } 102 namelen = strlen(base); 103 if (*end == '/') { 104 /* Strip off excess slashes in base string */ 105 while (namelen > 0 && base[namelen - 1] == '/') 106 namelen--; 107 } 108 buflen -= namelen; 109 if (buflen < 0) { 110 spin_unlock(&dentry->d_lock); 111 rcu_read_unlock(); 112 goto Elong; 113 } 114 end -= namelen; 115 memcpy(end, base, namelen); 116 spin_unlock(&dentry->d_lock); 117 rcu_read_unlock(); 118 return end; 119 Elong_unlock: 120 spin_unlock(&dentry->d_lock); 121 rcu_read_unlock(); 122 if (read_seqretry(&rename_lock, seq)) 123 goto rename_retry; 124 Elong: 125 return ERR_PTR(-ENAMETOOLONG); 126 } 127 EXPORT_SYMBOL_GPL(nfs_path); 128 129 /* 130 * nfs_d_automount - Handle crossing a mountpoint on the server 131 * @path - The mountpoint 132 * 133 * When we encounter a mountpoint on the server, we want to set up 134 * a mountpoint on the client too, to prevent inode numbers from 135 * colliding, and to allow "df" to work properly. 136 * On NFSv4, we also want to allow for the fact that different 137 * filesystems may be migrated to different servers in a failover 138 * situation, and that different filesystems may want to use 139 * different security flavours. 140 */ 141 struct vfsmount *nfs_d_automount(struct path *path) 142 { 143 struct vfsmount *mnt; 144 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry)); 145 struct nfs_fh *fh = NULL; 146 struct nfs_fattr *fattr = NULL; 147 148 if (IS_ROOT(path->dentry)) 149 return ERR_PTR(-ESTALE); 150 151 mnt = ERR_PTR(-ENOMEM); 152 fh = nfs_alloc_fhandle(); 153 fattr = nfs_alloc_fattr(); 154 if (fh == NULL || fattr == NULL) 155 goto out; 156 157 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr); 158 if (IS_ERR(mnt)) 159 goto out; 160 161 if (nfs_mountpoint_expiry_timeout < 0) 162 goto out; 163 164 mntget(mnt); /* prevent immediate expiration */ 165 mnt_set_expiry(mnt, &nfs_automount_list); 166 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 167 168 out: 169 nfs_free_fattr(fattr); 170 nfs_free_fhandle(fh); 171 return mnt; 172 } 173 174 static int 175 nfs_namespace_getattr(const struct path *path, struct kstat *stat, 176 u32 request_mask, unsigned int query_flags) 177 { 178 if (NFS_FH(d_inode(path->dentry))->size != 0) 179 return nfs_getattr(path, stat, request_mask, query_flags); 180 generic_fillattr(d_inode(path->dentry), stat); 181 return 0; 182 } 183 184 static int 185 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) 186 { 187 if (NFS_FH(d_inode(dentry))->size != 0) 188 return nfs_setattr(dentry, attr); 189 return -EACCES; 190 } 191 192 const struct inode_operations nfs_mountpoint_inode_operations = { 193 .getattr = nfs_getattr, 194 .setattr = nfs_setattr, 195 }; 196 197 const struct inode_operations nfs_referral_inode_operations = { 198 .getattr = nfs_namespace_getattr, 199 .setattr = nfs_namespace_setattr, 200 }; 201 202 static void nfs_expire_automounts(struct work_struct *work) 203 { 204 struct list_head *list = &nfs_automount_list; 205 206 mark_mounts_for_expiry(list); 207 if (!list_empty(list)) 208 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 209 } 210 211 void nfs_release_automount_timer(void) 212 { 213 if (list_empty(&nfs_automount_list)) 214 cancel_delayed_work(&nfs_automount_task); 215 } 216 217 /** 218 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 219 * @dentry: parent directory 220 * @fh: filehandle for new root dentry 221 * @fattr: attributes for new root inode 222 * @authflavor: security flavor to use when performing the mount 223 * 224 */ 225 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, 226 struct nfs_fattr *fattr, rpc_authflavor_t authflavor) 227 { 228 struct super_block *sb = dentry->d_sb; 229 struct nfs_clone_mount mountdata = { 230 .sb = sb, 231 .dentry = dentry, 232 .authflavor = authflavor, 233 }; 234 struct nfs_mount_info mount_info = { 235 .inherited_bsize = sb->s_blocksize_bits, 236 .cloned = &mountdata, 237 .mntfh = fh, 238 .nfs_mod = NFS_SB(sb)->nfs_client->cl_nfs_mod, 239 }; 240 struct nfs_server *server; 241 struct vfsmount *mnt; 242 char *page = (char *) __get_free_page(GFP_USER); 243 char *devname; 244 245 if (page == NULL) 246 return ERR_PTR(-ENOMEM); 247 248 server = mount_info.nfs_mod->rpc_ops->clone_server(NFS_SB(sb), fh, 249 fattr, authflavor); 250 if (IS_ERR(server)) 251 return ERR_CAST(server); 252 253 mount_info.server = server; 254 255 devname = nfs_devname(dentry, page, PAGE_SIZE); 256 if (IS_ERR(devname)) 257 mnt = ERR_CAST(devname); 258 else 259 mnt = vfs_submount(dentry, &nfs_prepared_fs_type, devname, &mount_info); 260 261 if (mount_info.server) 262 nfs_free_server(mount_info.server); 263 free_page((unsigned long)page); 264 return mnt; 265 } 266 EXPORT_SYMBOL_GPL(nfs_do_submount); 267 268 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry, 269 struct nfs_fh *fh, struct nfs_fattr *fattr) 270 { 271 int err; 272 struct dentry *parent = dget_parent(dentry); 273 274 /* Look it up again to get its attributes */ 275 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL); 276 dput(parent); 277 if (err != 0) 278 return ERR_PTR(err); 279 280 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor); 281 } 282 EXPORT_SYMBOL_GPL(nfs_submount); 283