1/* mountpoint management
2 *
3 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12#include <linux/kernel.h>
13#include <linux/module.h>
14#include <linux/init.h>
15#include <linux/slab.h>
16#include <linux/fs.h>
17#include <linux/pagemap.h>
18#include <linux/mount.h>
19#include <linux/namei.h>
20#include <linux/mnt_namespace.h>
21#include "internal.h"
22
23
24static struct dentry *afs_mntpt_lookup(struct inode *dir,
25				       struct dentry *dentry,
26				       struct nameidata *nd);
27static int afs_mntpt_open(struct inode *inode, struct file *file);
28static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd);
29static void afs_mntpt_expiry_timed_out(struct work_struct *work);
30
31const struct file_operations afs_mntpt_file_operations = {
32	.open		= afs_mntpt_open,
33};
34
35const struct inode_operations afs_mntpt_inode_operations = {
36	.lookup		= afs_mntpt_lookup,
37	.follow_link	= afs_mntpt_follow_link,
38	.readlink	= page_readlink,
39	.getattr	= afs_getattr,
40};
41
42static LIST_HEAD(afs_vfsmounts);
43static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
44
45unsigned long afs_mntpt_expiry_timeout = 10 * 60;
46
47/*
48 * check a symbolic link to see whether it actually encodes a mountpoint
49 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
50 */
51int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
52{
53	struct file file = {
54		.private_data = key,
55	};
56	struct page *page;
57	size_t size;
58	char *buf;
59	int ret;
60
61	_enter("{%x:%u,%u}",
62	       vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
63
64	/* read the contents of the symlink into the pagecache */
65	page = read_mapping_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0, &file);
66	if (IS_ERR(page)) {
67		ret = PTR_ERR(page);
68		goto out;
69	}
70
71	ret = -EIO;
72	if (PageError(page))
73		goto out_free;
74
75	buf = kmap(page);
76
77	/* examine the symlink's contents */
78	size = vnode->status.size;
79	_debug("symlink to %*.*s", (int) size, (int) size, buf);
80
81	if (size > 2 &&
82	    (buf[0] == '%' || buf[0] == '#') &&
83	    buf[size - 1] == '.'
84	    ) {
85		_debug("symlink is a mountpoint");
86		spin_lock(&vnode->lock);
87		set_bit(AFS_VNODE_MOUNTPOINT, &vnode->flags);
88		spin_unlock(&vnode->lock);
89	}
90
91	ret = 0;
92
93	kunmap(page);
94out_free:
95	page_cache_release(page);
96out:
97	_leave(" = %d", ret);
98	return ret;
99}
100
101/*
102 * no valid lookup procedure on this sort of dir
103 */
104static struct dentry *afs_mntpt_lookup(struct inode *dir,
105				       struct dentry *dentry,
106				       struct nameidata *nd)
107{
108	_enter("%p,%p{%p{%s},%s}",
109	       dir,
110	       dentry,
111	       dentry->d_parent,
112	       dentry->d_parent ?
113	       dentry->d_parent->d_name.name : (const unsigned char *) "",
114	       dentry->d_name.name);
115
116	return ERR_PTR(-EREMOTE);
117}
118
119/*
120 * no valid open procedure on this sort of dir
121 */
122static int afs_mntpt_open(struct inode *inode, struct file *file)
123{
124	_enter("%p,%p{%p{%s},%s}",
125	       inode, file,
126	       file->f_path.dentry->d_parent,
127	       file->f_path.dentry->d_parent ?
128	       file->f_path.dentry->d_parent->d_name.name :
129	       (const unsigned char *) "",
130	       file->f_path.dentry->d_name.name);
131
132	return -EREMOTE;
133}
134
135/*
136 * create a vfsmount to be automounted
137 */
138static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
139{
140	struct afs_super_info *super;
141	struct vfsmount *mnt;
142	struct page *page = NULL;
143	size_t size;
144	char *buf, *devname = NULL, *options = NULL;
145	int ret;
146
147	_enter("{%s}", mntpt->d_name.name);
148
149	BUG_ON(!mntpt->d_inode);
150
151	ret = -EINVAL;
152	size = mntpt->d_inode->i_size;
153	if (size > PAGE_SIZE - 1)
154		goto error;
155
156	ret = -ENOMEM;
157	devname = (char *) get_zeroed_page(GFP_KERNEL);
158	if (!devname)
159		goto error;
160
161	options = (char *) get_zeroed_page(GFP_KERNEL);
162	if (!options)
163		goto error;
164
165	/* read the contents of the AFS special symlink */
166	page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
167	if (IS_ERR(page)) {
168		ret = PTR_ERR(page);
169		goto error;
170	}
171
172	ret = -EIO;
173	if (PageError(page))
174		goto error;
175
176	buf = kmap(page);
177	memcpy(devname, buf, size);
178	kunmap(page);
179	page_cache_release(page);
180	page = NULL;
181
182	/* work out what options we want */
183	super = AFS_FS_S(mntpt->d_sb);
184	memcpy(options, "cell=", 5);
185	strcpy(options + 5, super->volume->cell->name);
186	if (super->volume->type == AFSVL_RWVOL)
187		strcat(options, ",rwpath");
188
189	/* try and do the mount */
190	_debug("--- attempting mount %s -o %s ---", devname, options);
191	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
192	_debug("--- mount result %p ---", mnt);
193
194	free_page((unsigned long) devname);
195	free_page((unsigned long) options);
196	_leave(" = %p", mnt);
197	return mnt;
198
199error:
200	if (page)
201		page_cache_release(page);
202	if (devname)
203		free_page((unsigned long) devname);
204	if (options)
205		free_page((unsigned long) options);
206	_leave(" = %d", ret);
207	return ERR_PTR(ret);
208}
209
210/*
211 * follow a link from a mountpoint directory, thus causing it to be mounted
212 */
213static void *afs_mntpt_follow_link(struct dentry *dentry, struct nameidata *nd)
214{
215	struct vfsmount *newmnt;
216	int err;
217
218	_enter("%p{%s},{%s:%p{%s},}",
219	       dentry,
220	       dentry->d_name.name,
221	       nd->mnt->mnt_devname,
222	       dentry,
223	       nd->dentry->d_name.name);
224
225	dput(nd->dentry);
226	nd->dentry = dget(dentry);
227
228	newmnt = afs_mntpt_do_automount(nd->dentry);
229	if (IS_ERR(newmnt)) {
230		path_release(nd);
231		return (void *)newmnt;
232	}
233
234	mntget(newmnt);
235	err = do_add_mount(newmnt, nd, MNT_SHRINKABLE, &afs_vfsmounts);
236	switch (err) {
237	case 0:
238		mntput(nd->mnt);
239		dput(nd->dentry);
240		nd->mnt = newmnt;
241		nd->dentry = dget(newmnt->mnt_root);
242		schedule_delayed_work(&afs_mntpt_expiry_timer,
243				      afs_mntpt_expiry_timeout * HZ);
244		break;
245	case -EBUSY:
246		/* someone else made a mount here whilst we were busy */
247		while (d_mountpoint(nd->dentry) &&
248		       follow_down(&nd->mnt, &nd->dentry))
249			;
250		err = 0;
251	default:
252		mntput(newmnt);
253		break;
254	}
255
256	_leave(" = %d", err);
257	return ERR_PTR(err);
258}
259
260/*
261 * handle mountpoint expiry timer going off
262 */
263static void afs_mntpt_expiry_timed_out(struct work_struct *work)
264{
265	_enter("");
266
267	if (!list_empty(&afs_vfsmounts)) {
268		mark_mounts_for_expiry(&afs_vfsmounts);
269		schedule_delayed_work(&afs_mntpt_expiry_timer,
270				      afs_mntpt_expiry_timeout * HZ);
271	}
272
273	_leave("");
274}
275
276/*
277 * kill the AFS mountpoint timer if it's still running
278 */
279void afs_mntpt_kill_timer(void)
280{
281	_enter("");
282
283	ASSERT(list_empty(&afs_vfsmounts));
284	cancel_delayed_work(&afs_mntpt_expiry_timer);
285	flush_scheduled_work();
286}
287
288/*
289 * begin unmount by attempting to remove all automounted mountpoints we added
290 */
291void afs_umount_begin(struct vfsmount *vfsmnt, int flags)
292{
293	shrink_submounts(vfsmnt, &afs_vfsmounts);
294}
295