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/fs.h>
16#include <linux/pagemap.h>
17#include <linux/mount.h>
18#include <linux/namei.h>
19#include <linux/gfp.h>
20#include "internal.h"
21
22
23static struct dentry *afs_mntpt_lookup(struct inode *dir,
24				       struct dentry *dentry,
25				       unsigned int flags);
26static int afs_mntpt_open(struct inode *inode, struct file *file);
27static void afs_mntpt_expiry_timed_out(struct work_struct *work);
28
29const struct file_operations afs_mntpt_file_operations = {
30	.open		= afs_mntpt_open,
31	.llseek		= noop_llseek,
32};
33
34const struct inode_operations afs_mntpt_inode_operations = {
35	.lookup		= afs_mntpt_lookup,
36	.readlink	= page_readlink,
37	.getattr	= afs_getattr,
38};
39
40const struct inode_operations afs_autocell_inode_operations = {
41	.getattr	= afs_getattr,
42};
43
44static LIST_HEAD(afs_vfsmounts);
45static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
46
47static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
48
49/*
50 * check a symbolic link to see whether it actually encodes a mountpoint
51 * - sets the AFS_VNODE_MOUNTPOINT flag on the vnode appropriately
52 */
53int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
54{
55	struct page *page;
56	size_t size;
57	char *buf;
58	int ret;
59
60	_enter("{%x:%u,%u}",
61	       vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
62
63	/* read the contents of the symlink into the pagecache */
64	page = read_cache_page(AFS_VNODE_TO_I(vnode)->i_mapping, 0,
65			       afs_page_filler, key);
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		vnode->vfs_inode.i_flags |= S_AUTOMOUNT;
89		spin_unlock(&vnode->lock);
90	}
91
92	ret = 0;
93
94	kunmap(page);
95out_free:
96	page_cache_release(page);
97out:
98	_leave(" = %d", ret);
99	return ret;
100}
101
102/*
103 * no valid lookup procedure on this sort of dir
104 */
105static struct dentry *afs_mntpt_lookup(struct inode *dir,
106				       struct dentry *dentry,
107				       unsigned int flags)
108{
109	_enter("%p,%p{%pd2}", dir, dentry, dentry);
110	return ERR_PTR(-EREMOTE);
111}
112
113/*
114 * no valid open procedure on this sort of dir
115 */
116static int afs_mntpt_open(struct inode *inode, struct file *file)
117{
118	_enter("%p,%p{%pD2}", inode, file, file);
119	return -EREMOTE;
120}
121
122/*
123 * create a vfsmount to be automounted
124 */
125static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
126{
127	struct afs_super_info *super;
128	struct vfsmount *mnt;
129	struct afs_vnode *vnode;
130	struct page *page;
131	char *devname, *options;
132	bool rwpath = false;
133	int ret;
134
135	_enter("{%pd}", mntpt);
136
137	BUG_ON(!d_inode(mntpt));
138
139	ret = -ENOMEM;
140	devname = (char *) get_zeroed_page(GFP_KERNEL);
141	if (!devname)
142		goto error_no_devname;
143
144	options = (char *) get_zeroed_page(GFP_KERNEL);
145	if (!options)
146		goto error_no_options;
147
148	vnode = AFS_FS_I(d_inode(mntpt));
149	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
150		/* if the directory is a pseudo directory, use the d_name */
151		static const char afs_root_cell[] = ":root.cell.";
152		unsigned size = mntpt->d_name.len;
153
154		ret = -ENOENT;
155		if (size < 2 || size > AFS_MAXCELLNAME)
156			goto error_no_page;
157
158		if (mntpt->d_name.name[0] == '.') {
159			devname[0] = '#';
160			memcpy(devname + 1, mntpt->d_name.name, size - 1);
161			memcpy(devname + size, afs_root_cell,
162			       sizeof(afs_root_cell));
163			rwpath = true;
164		} else {
165			devname[0] = '%';
166			memcpy(devname + 1, mntpt->d_name.name, size);
167			memcpy(devname + size + 1, afs_root_cell,
168			       sizeof(afs_root_cell));
169		}
170	} else {
171		/* read the contents of the AFS special symlink */
172		loff_t size = i_size_read(d_inode(mntpt));
173		char *buf;
174
175		ret = -EINVAL;
176		if (size > PAGE_SIZE - 1)
177			goto error_no_page;
178
179		page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
180		if (IS_ERR(page)) {
181			ret = PTR_ERR(page);
182			goto error_no_page;
183		}
184
185		ret = -EIO;
186		if (PageError(page))
187			goto error;
188
189		buf = kmap_atomic(page);
190		memcpy(devname, buf, size);
191		kunmap_atomic(buf);
192		page_cache_release(page);
193		page = NULL;
194	}
195
196	/* work out what options we want */
197	super = AFS_FS_S(mntpt->d_sb);
198	memcpy(options, "cell=", 5);
199	strcpy(options + 5, super->volume->cell->name);
200	if (super->volume->type == AFSVL_RWVOL || rwpath)
201		strcat(options, ",rwpath");
202
203	/* try and do the mount */
204	_debug("--- attempting mount %s -o %s ---", devname, options);
205	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
206	_debug("--- mount result %p ---", mnt);
207
208	free_page((unsigned long) devname);
209	free_page((unsigned long) options);
210	_leave(" = %p", mnt);
211	return mnt;
212
213error:
214	page_cache_release(page);
215error_no_page:
216	free_page((unsigned long) options);
217error_no_options:
218	free_page((unsigned long) devname);
219error_no_devname:
220	_leave(" = %d", ret);
221	return ERR_PTR(ret);
222}
223
224/*
225 * handle an automount point
226 */
227struct vfsmount *afs_d_automount(struct path *path)
228{
229	struct vfsmount *newmnt;
230
231	_enter("{%pd}", path->dentry);
232
233	newmnt = afs_mntpt_do_automount(path->dentry);
234	if (IS_ERR(newmnt))
235		return newmnt;
236
237	mntget(newmnt); /* prevent immediate expiration */
238	mnt_set_expiry(newmnt, &afs_vfsmounts);
239	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
240			   afs_mntpt_expiry_timeout * HZ);
241	_leave(" = %p", newmnt);
242	return newmnt;
243}
244
245/*
246 * handle mountpoint expiry timer going off
247 */
248static void afs_mntpt_expiry_timed_out(struct work_struct *work)
249{
250	_enter("");
251
252	if (!list_empty(&afs_vfsmounts)) {
253		mark_mounts_for_expiry(&afs_vfsmounts);
254		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
255				   afs_mntpt_expiry_timeout * HZ);
256	}
257
258	_leave("");
259}
260
261/*
262 * kill the AFS mountpoint timer if it's still running
263 */
264void afs_mntpt_kill_timer(void)
265{
266	_enter("");
267
268	ASSERT(list_empty(&afs_vfsmounts));
269	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
270}
271