1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/fs/nfs/namespace.c
5 * Copyright (C) 2005 Trond Myklebust <Trond.Myklebust@netapp.com>
6 * - Modified by David Howells <dhowells@redhat.com>
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>
24 #define NFSDBG_FACILITY NFSDBG_VFS
26 static void nfs_expire_automounts(struct work_struct *work);
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;
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)
40 * Helper function for constructing the server pathname
41 * by arbitrary hashed dentry.
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.
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)
52 char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
65 seq = read_seqbegin(&rename_lock);
68 spin_lock(&dentry->d_lock);
71 namelen = dentry->d_name.len;
72 buflen -= namelen + 1;
76 memcpy(end, dentry->d_name.name, namelen);
78 spin_unlock(&dentry->d_lock);
79 dentry = dentry->d_parent;
81 if (read_seqretry(&rename_lock, seq)) {
82 spin_unlock(&dentry->d_lock);
86 if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
88 spin_unlock(&dentry->d_lock);
95 base = dentry->d_fsdata;
97 spin_unlock(&dentry->d_lock);
102 namelen = strlen(base);
104 /* Strip off excess slashes in base string */
105 while (namelen > 0 && base[namelen - 1] == '/')
110 spin_unlock(&dentry->d_lock);
115 memcpy(end, base, namelen);
116 spin_unlock(&dentry->d_lock);
120 spin_unlock(&dentry->d_lock);
122 if (read_seqretry(&rename_lock, seq))
125 return ERR_PTR(-ENAMETOOLONG);
127 EXPORT_SYMBOL_GPL(nfs_path);
130 * nfs_d_automount - Handle crossing a mountpoint on the server
131 * @path - The mountpoint
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.
141 struct vfsmount *nfs_d_automount(struct path *path)
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;
148 if (IS_ROOT(path->dentry))
149 return ERR_PTR(-ESTALE);
151 mnt = ERR_PTR(-ENOMEM);
152 fh = nfs_alloc_fhandle();
153 fattr = nfs_alloc_fattr();
154 if (fh == NULL || fattr == NULL)
157 mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
161 if (nfs_mountpoint_expiry_timeout < 0)
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);
169 nfs_free_fattr(fattr);
170 nfs_free_fhandle(fh);
175 nfs_namespace_getattr(const struct path *path, struct kstat *stat,
176 u32 request_mask, unsigned int query_flags)
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);
185 nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
187 if (NFS_FH(d_inode(dentry))->size != 0)
188 return nfs_setattr(dentry, attr);
192 const struct inode_operations nfs_mountpoint_inode_operations = {
193 .getattr = nfs_getattr,
194 .setattr = nfs_setattr,
197 const struct inode_operations nfs_referral_inode_operations = {
198 .getattr = nfs_namespace_getattr,
199 .setattr = nfs_namespace_setattr,
202 static void nfs_expire_automounts(struct work_struct *work)
204 struct list_head *list = &nfs_automount_list;
206 mark_mounts_for_expiry(list);
207 if (!list_empty(list))
208 schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
211 void nfs_release_automount_timer(void)
213 if (list_empty(&nfs_automount_list))
214 cancel_delayed_work(&nfs_automount_task);
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
225 struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
226 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
228 struct super_block *sb = dentry->d_sb;
229 struct nfs_clone_mount mountdata = {
232 .authflavor = authflavor,
234 struct nfs_mount_info mount_info = {
235 .fill_super = nfs_clone_super,
236 .set_security = nfs_clone_sb_security,
237 .cloned = &mountdata,
239 .nfs_mod = NFS_SB(sb)->nfs_client->cl_nfs_mod,
241 struct nfs_server *server;
242 struct vfsmount *mnt;
243 char *page = (char *) __get_free_page(GFP_USER);
247 return ERR_PTR(-ENOMEM);
249 server = mount_info.nfs_mod->rpc_ops->clone_server(NFS_SB(sb), fh,
252 return ERR_CAST(server);
254 mount_info.server = server;
256 devname = nfs_devname(dentry, page, PAGE_SIZE);
258 mnt = ERR_CAST(devname);
260 mnt = vfs_submount(dentry, &nfs_prepared_fs_type, devname, &mount_info);
262 if (mount_info.server)
263 nfs_free_server(mount_info.server);
264 free_page((unsigned long)page);
267 EXPORT_SYMBOL_GPL(nfs_do_submount);
269 struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
270 struct nfs_fh *fh, struct nfs_fattr *fattr)
273 struct dentry *parent = dget_parent(dentry);
275 /* Look it up again to get its attributes */
276 err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
281 return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
283 EXPORT_SYMBOL_GPL(nfs_submount);