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/module.h>
11#include <linux/dcache.h>
12#include <linux/gfp.h>
13#include <linux/mount.h>
14#include <linux/namei.h>
15#include <linux/nfs_fs.h>
16#include <linux/string.h>
17#include <linux/sunrpc/clnt.h>
18#include <linux/vfs.h>
19#include <linux/sunrpc/gss_api.h>
20#include "internal.h"
21
22#define NFSDBG_FACILITY		NFSDBG_VFS
23
24static void nfs_expire_automounts(struct work_struct *work);
25
26static LIST_HEAD(nfs_automount_list);
27static DECLARE_DELAYED_WORK(nfs_automount_task, nfs_expire_automounts);
28int nfs_mountpoint_expiry_timeout = 500 * HZ;
29
30/*
31 * nfs_path - reconstruct the path given an arbitrary dentry
32 * @base - used to return pointer to the end of devname part of path
33 * @dentry - pointer to dentry
34 * @buffer - result buffer
35 * @buflen - length of buffer
36 * @flags - options (see below)
37 *
38 * Helper function for constructing the server pathname
39 * by arbitrary hashed dentry.
40 *
41 * This is mainly for use in figuring out the path on the
42 * server side when automounting on top of an existing partition
43 * and in generating /proc/mounts and friends.
44 *
45 * Supported flags:
46 * NFS_PATH_CANONICAL: ensure there is exactly one slash after
47 *		       the original device (export) name
48 *		       (if unset, the original name is returned verbatim)
49 */
50char *nfs_path(char **p, struct dentry *dentry, char *buffer, ssize_t buflen,
51	       unsigned flags)
52{
53	char *end;
54	int namelen;
55	unsigned seq;
56	const char *base;
57
58rename_retry:
59	end = buffer+buflen;
60	*--end = '\0';
61	buflen--;
62
63	seq = read_seqbegin(&rename_lock);
64	rcu_read_lock();
65	while (1) {
66		spin_lock(&dentry->d_lock);
67		if (IS_ROOT(dentry))
68			break;
69		namelen = dentry->d_name.len;
70		buflen -= namelen + 1;
71		if (buflen < 0)
72			goto Elong_unlock;
73		end -= namelen;
74		memcpy(end, dentry->d_name.name, namelen);
75		*--end = '/';
76		spin_unlock(&dentry->d_lock);
77		dentry = dentry->d_parent;
78	}
79	if (read_seqretry(&rename_lock, seq)) {
80		spin_unlock(&dentry->d_lock);
81		rcu_read_unlock();
82		goto rename_retry;
83	}
84	if ((flags & NFS_PATH_CANONICAL) && *end != '/') {
85		if (--buflen < 0) {
86			spin_unlock(&dentry->d_lock);
87			rcu_read_unlock();
88			goto Elong;
89		}
90		*--end = '/';
91	}
92	*p = end;
93	base = dentry->d_fsdata;
94	if (!base) {
95		spin_unlock(&dentry->d_lock);
96		rcu_read_unlock();
97		WARN_ON(1);
98		return end;
99	}
100	namelen = strlen(base);
101	if (flags & NFS_PATH_CANONICAL) {
102		/* Strip off excess slashes in base string */
103		while (namelen > 0 && base[namelen - 1] == '/')
104			namelen--;
105	}
106	buflen -= namelen;
107	if (buflen < 0) {
108		spin_unlock(&dentry->d_lock);
109		rcu_read_unlock();
110		goto Elong;
111	}
112	end -= namelen;
113	memcpy(end, base, namelen);
114	spin_unlock(&dentry->d_lock);
115	rcu_read_unlock();
116	return end;
117Elong_unlock:
118	spin_unlock(&dentry->d_lock);
119	rcu_read_unlock();
120	if (read_seqretry(&rename_lock, seq))
121		goto rename_retry;
122Elong:
123	return ERR_PTR(-ENAMETOOLONG);
124}
125EXPORT_SYMBOL_GPL(nfs_path);
126
127/*
128 * nfs_d_automount - Handle crossing a mountpoint on the server
129 * @path - The mountpoint
130 *
131 * When we encounter a mountpoint on the server, we want to set up
132 * a mountpoint on the client too, to prevent inode numbers from
133 * colliding, and to allow "df" to work properly.
134 * On NFSv4, we also want to allow for the fact that different
135 * filesystems may be migrated to different servers in a failover
136 * situation, and that different filesystems may want to use
137 * different security flavours.
138 */
139struct vfsmount *nfs_d_automount(struct path *path)
140{
141	struct vfsmount *mnt;
142	struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
143	struct nfs_fh *fh = NULL;
144	struct nfs_fattr *fattr = NULL;
145
146	dprintk("--> nfs_d_automount()\n");
147
148	mnt = ERR_PTR(-ESTALE);
149	if (IS_ROOT(path->dentry))
150		goto out_nofree;
151
152	mnt = ERR_PTR(-ENOMEM);
153	fh = nfs_alloc_fhandle();
154	fattr = nfs_alloc_fattr();
155	if (fh == NULL || fattr == NULL)
156		goto out;
157
158	dprintk("%s: enter\n", __func__);
159
160	mnt = server->nfs_client->rpc_ops->submount(server, path->dentry, fh, fattr);
161	if (IS_ERR(mnt))
162		goto out;
163
164	dprintk("%s: done, success\n", __func__);
165	mntget(mnt); /* prevent immediate expiration */
166	mnt_set_expiry(mnt, &nfs_automount_list);
167	schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
168
169out:
170	nfs_free_fattr(fattr);
171	nfs_free_fhandle(fh);
172out_nofree:
173	if (IS_ERR(mnt))
174		dprintk("<-- %s(): error %ld\n", __func__, PTR_ERR(mnt));
175	else
176		dprintk("<-- %s() = %p\n", __func__, mnt);
177	return mnt;
178}
179
180static int
181nfs_namespace_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
182{
183	if (NFS_FH(d_inode(dentry))->size != 0)
184		return nfs_getattr(mnt, dentry, stat);
185	generic_fillattr(d_inode(dentry), stat);
186	return 0;
187}
188
189static int
190nfs_namespace_setattr(struct dentry *dentry, struct iattr *attr)
191{
192	if (NFS_FH(d_inode(dentry))->size != 0)
193		return nfs_setattr(dentry, attr);
194	return -EACCES;
195}
196
197const struct inode_operations nfs_mountpoint_inode_operations = {
198	.getattr	= nfs_getattr,
199	.setattr	= nfs_setattr,
200};
201
202const struct inode_operations nfs_referral_inode_operations = {
203	.getattr	= nfs_namespace_getattr,
204	.setattr	= nfs_namespace_setattr,
205};
206
207static void nfs_expire_automounts(struct work_struct *work)
208{
209	struct list_head *list = &nfs_automount_list;
210
211	mark_mounts_for_expiry(list);
212	if (!list_empty(list))
213		schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
214}
215
216void nfs_release_automount_timer(void)
217{
218	if (list_empty(&nfs_automount_list))
219		cancel_delayed_work(&nfs_automount_task);
220}
221
222/*
223 * Clone a mountpoint of the appropriate type
224 */
225static struct vfsmount *nfs_do_clone_mount(struct nfs_server *server,
226					   const char *devname,
227					   struct nfs_clone_mount *mountdata)
228{
229	return vfs_kern_mount(&nfs_xdev_fs_type, 0, devname, mountdata);
230}
231
232/**
233 * nfs_do_submount - set up mountpoint when crossing a filesystem boundary
234 * @dentry - parent directory
235 * @fh - filehandle for new root dentry
236 * @fattr - attributes for new root inode
237 * @authflavor - security flavor to use when performing the mount
238 *
239 */
240struct vfsmount *nfs_do_submount(struct dentry *dentry, struct nfs_fh *fh,
241				 struct nfs_fattr *fattr, rpc_authflavor_t authflavor)
242{
243	struct nfs_clone_mount mountdata = {
244		.sb = dentry->d_sb,
245		.dentry = dentry,
246		.fh = fh,
247		.fattr = fattr,
248		.authflavor = authflavor,
249	};
250	struct vfsmount *mnt = ERR_PTR(-ENOMEM);
251	char *page = (char *) __get_free_page(GFP_USER);
252	char *devname;
253
254	dprintk("--> nfs_do_submount()\n");
255
256	dprintk("%s: submounting on %pd2\n", __func__,
257			dentry);
258	if (page == NULL)
259		goto out;
260	devname = nfs_devname(dentry, page, PAGE_SIZE);
261	mnt = (struct vfsmount *)devname;
262	if (IS_ERR(devname))
263		goto free_page;
264	mnt = nfs_do_clone_mount(NFS_SB(dentry->d_sb), devname, &mountdata);
265free_page:
266	free_page((unsigned long)page);
267out:
268	dprintk("%s: done\n", __func__);
269
270	dprintk("<-- nfs_do_submount() = %p\n", mnt);
271	return mnt;
272}
273EXPORT_SYMBOL_GPL(nfs_do_submount);
274
275struct vfsmount *nfs_submount(struct nfs_server *server, struct dentry *dentry,
276			      struct nfs_fh *fh, struct nfs_fattr *fattr)
277{
278	int err;
279	struct dentry *parent = dget_parent(dentry);
280
281	/* Look it up again to get its attributes */
282	err = server->nfs_client->rpc_ops->lookup(d_inode(parent), &dentry->d_name, fh, fattr, NULL);
283	dput(parent);
284	if (err != 0)
285		return ERR_PTR(err);
286
287	return nfs_do_submount(dentry, fh, fattr, server->client->cl_auth->au_flavor);
288}
289EXPORT_SYMBOL_GPL(nfs_submount);
290