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 23 #define NFSDBG_FACILITY NFSDBG_VFS 24 25 static void nfs_expire_automounts(struct work_struct *work); 26 27 static LIST_HEAD(nfs_automount_list); 28 static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts); 29 int nfs_mountpoint_expiry_timeout = 500 * HZ; 30 31 /* 32 * nfs_path - reconstruct the path given an arbitrary dentry 33 * @base - used to return pointer to the end of devname part of path 34 * @dentry - pointer to dentry 35 * @buffer - result buffer 36 * @buflen - length of buffer 37 * @flags - options (see below) 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 * Supported flags: 47 * NFS_PATH_CANONICAL: ensure there is exactly one slash after 48 * the original device (export) name 49 * (if unset, the original name is returned verbatim) 50 */ 51 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen, 52 unsigned flags) 53 { 54 char *end; 55 int namelen; 56 unsigned seq; 57 const char *base; 58 59 rename_retry: 60 end = buffer+buflen; 61 *--end = '\0'; 62 buflen--; 63 64 seq = read_seqbegin(&rename_lock); 65 rcu_read_lock(); 66 while (1) { 67 spin_lock(&dentry->d_lock); 68 if (IS_ROOT(dentry)) 69 break; 70 namelen = dentry->d_name.len; 71 buflen -= namelen + 1; 72 if (buflen < 0) 73 goto Elong_unlock; 74 end -= namelen; 75 memcpy(end, dentry->d_name.name, namelen); 76 *--end = '/'; 77 spin_unlock(&dentry->d_lock); 78 dentry = dentry->d_parent; 79 } 80 if (read_seqretry(&rename_lock, seq)) { 81 spin_unlock(&dentry->d_lock); 82 rcu_read_unlock(); 83 goto rename_retry; 84 } 85 if ((flags & NFS_PATH_CANONICAL) && *end != '/') { 86 if (--buflen < 0) { 87 spin_unlock(&dentry->d_lock); 88 rcu_read_unlock(); 89 goto Elong; 90 } 91 *--end = '/'; 92 } 93 *p = end; 94 base = dentry->d_fsdata; 95 if (!base) { 96 spin_unlock(&dentry->d_lock); 97 rcu_read_unlock(); 98 WARN_ON(1); 99 return end; 100 } 101 namelen = strlen(base); 102 if (*end == '/') { 103 /* Strip off excess slashes in base string */ 104 while (namelen > 0 && base[namelen - 1] == '/') 105 namelen--; 106 } 107 buflen -= namelen; 108 if (buflen < 0) { 109 spin_unlock(&dentry->d_lock); 110 rcu_read_unlock(); 111 goto Elong; 112 } 113 end -= namelen; 114 memcpy(end, base, namelen); 115 spin_unlock(&dentry->d_lock); 116 rcu_read_unlock(); 117 return end; 118 Elong_unlock: 119 spin_unlock(&dentry->d_lock); 120 rcu_read_unlock(); 121 if (read_seqretry(&rename_lock, seq)) 122 goto rename_retry; 123 Elong: 124 return ERR_PTR(-ENAMETOOLONG); 125 } 126 EXPORT_SYMBOL_GPL(nfs_path); 127 128 /* 129 * nfs_d_automount - Handle crossing a mountpoint on the server 130 * @path - The mountpoint 131 * 132 * When we encounter a mountpoint on the server, we want to set up 133 * a mountpoint on the client too, to prevent inode numbers from 134 * colliding, and to allow "df" to work properly. 135 * On NFSv4, we also want to allow for the fact that different 136 * filesystems may be migrated to different servers in a failover 137 * situation, and that different filesystems may want to use 138 * different security flavours. 139 */ 140 struct vfsmount *nfs_d_automount(struct path *path) 141 { 142 struct vfsmount *mnt; 143 struct nfs_server *server = NFS_SERVER(d_inode(path->dentry)); 144 struct nfs_fh *fh = NULL; 145 struct nfs_fattr *fattr = NULL; 146 147 if (IS_ROOT(path->dentry)) 148 return ERR_PTR(-ESTALE); 149 150 mnt = ERR_PTR(-ENOMEM); 151 fh = nfs_alloc_fhandle(); 152 fattr = nfs_alloc_fattr(); 153 if (fh == NULL || fattr == NULL) 154 goto out; 155 156 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr); 157 if (IS_ERR(mnt)) 158 goto out; 159 160 if (nfs_mountpoint_expiry_timeout < 0) 161 goto out; 162 163 mntget(mnt); /* prevent immediate expiration */ 164 mnt_set_expiry(mnt, &nfs_automount_list); 165 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 166 167 out: 168 nfs_free_fattr(fattr); 169 nfs_free_fhandle(fh); 170 return mnt; 171 } 172 173 static int 174 nfs_namespace_getattr(const struct path *path, struct kstat *stat, 175 u32 request_mask, unsigned int query_flags) 176 { 177 if (NFS_FH(d_inode(path->dentry))->size != 0) 178 return nfs_getattr(path, stat, request_mask, query_flags); 179 generic_fillattr(d_inode(path->dentry), stat); 180 return 0; 181 } 182 183 static int 184 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr) 185 { 186 if (NFS_FH(d_inode(dentry))->size != 0) 187 return nfs_setattr(dentry, attr); 188 return -EACCES; 189 } 190 191 const struct inode_operations nfs_mountpoint_inode_operations = { 192 .getattr = nfs_getattr, 193 .setattr = nfs_setattr, 194 }; 195 196 const struct inode_operations nfs_referral_inode_operations = { 197 .getattr = nfs_namespace_getattr, 198 .setattr = nfs_namespace_setattr, 199 }; 200 201 static void nfs_expire_automounts(struct work_struct *work) 202 { 203 struct list_head *list = &nfs_automount_list; 204 205 mark_mounts_for_expiry(list); 206 if (!list_empty(list)) 207 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout); 208 } 209 210 void nfs_release_automount_timer(void) 211 { 212 if (list_empty(&nfs_automount_list)) 213 cancel_delayed_work(&nfs_automount_task); 214 } 215 216 /* 217 * Clone a mountpoint of the appropriate type 218 */ 219 static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server, 220 const char *devname, 221 struct nfs_clone_mount *mountdata) 222 { 223 return vfs_submount(mountdata->dentry, &nfs_xdev_fs_type, devname, mountdata); 224 } 225 226 /** 227 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary 228 * @dentry: parent directory 229 * @fh: filehandle for new root dentry 230 * @fattr: attributes for new root inode 231 * @authflavor: security flavor to use when performing the mount 232 * 233 */ 234 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh, 235 struct nfs_fattr *fattr, rpc_authflavor_t authflavor) 236 { 237 struct nfs_clone_mount mountdata = { 238 .sb = dentry->d_sb, 239 .dentry = dentry, 240 .fh = fh, 241 .fattr = fattr, 242 .authflavor = authflavor, 243 }; 244 struct vfsmount *mnt; 245 char *page = (char *) __get_free_page(GFP_USER); 246 char *devname; 247 248 if (page == NULL) 249 return ERR_PTR(-ENOMEM); 250 251 devname = nfs_devname(dentry, page, PAGE_SIZE); 252 if (IS_ERR(devname)) 253 mnt = ERR_CAST(devname); 254 else 255 mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata); 256 257 free_page((unsigned long)page); 258 return mnt; 259 } 260 EXPORT_SYMBOL_GPL(nfs_do_submount); 261 262 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry, 263 struct nfs_fh *fh, struct nfs_fattr *fattr) 264 { 265 int err; 266 struct dentry *parent = dget_parent(dentry); 267 268 /* Look it up again to get its attributes */ 269 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL); 270 dput(parent); 271 if (err != 0) 272 return ERR_PTR(err); 273 274 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor); 275 } 276 EXPORT_SYMBOL_GPL(nfs_submount); 277