xref: /openbmc/linux/fs/afs/mntpt.c (revision 62e7ca52)
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 
23 static struct dentry *afs_mntpt_lookup(struct inode *dir,
24 				       struct dentry *dentry,
25 				       unsigned int flags);
26 static int afs_mntpt_open(struct inode *inode, struct file *file);
27 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
28 
29 const struct file_operations afs_mntpt_file_operations = {
30 	.open		= afs_mntpt_open,
31 	.llseek		= noop_llseek,
32 };
33 
34 const struct inode_operations afs_mntpt_inode_operations = {
35 	.lookup		= afs_mntpt_lookup,
36 	.readlink	= page_readlink,
37 	.getattr	= afs_getattr,
38 };
39 
40 const struct inode_operations afs_autocell_inode_operations = {
41 	.getattr	= afs_getattr,
42 };
43 
44 static LIST_HEAD(afs_vfsmounts);
45 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
46 
47 static 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  */
53 int 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);
95 out_free:
96 	page_cache_release(page);
97 out:
98 	_leave(" = %d", ret);
99 	return ret;
100 }
101 
102 /*
103  * no valid lookup procedure on this sort of dir
104  */
105 static struct dentry *afs_mntpt_lookup(struct inode *dir,
106 				       struct dentry *dentry,
107 				       unsigned int flags)
108 {
109 	_enter("%p,%p{%p{%s},%s}",
110 	       dir,
111 	       dentry,
112 	       dentry->d_parent,
113 	       dentry->d_parent ?
114 	       dentry->d_parent->d_name.name : (const unsigned char *) "",
115 	       dentry->d_name.name);
116 
117 	return ERR_PTR(-EREMOTE);
118 }
119 
120 /*
121  * no valid open procedure on this sort of dir
122  */
123 static int afs_mntpt_open(struct inode *inode, struct file *file)
124 {
125 	_enter("%p,%p{%p{%s},%s}",
126 	       inode, file,
127 	       file->f_path.dentry->d_parent,
128 	       file->f_path.dentry->d_parent ?
129 	       file->f_path.dentry->d_parent->d_name.name :
130 	       (const unsigned char *) "",
131 	       file->f_path.dentry->d_name.name);
132 
133 	return -EREMOTE;
134 }
135 
136 /*
137  * create a vfsmount to be automounted
138  */
139 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
140 {
141 	struct afs_super_info *super;
142 	struct vfsmount *mnt;
143 	struct afs_vnode *vnode;
144 	struct page *page;
145 	char *devname, *options;
146 	bool rwpath = false;
147 	int ret;
148 
149 	_enter("{%s}", mntpt->d_name.name);
150 
151 	BUG_ON(!mntpt->d_inode);
152 
153 	ret = -ENOMEM;
154 	devname = (char *) get_zeroed_page(GFP_KERNEL);
155 	if (!devname)
156 		goto error_no_devname;
157 
158 	options = (char *) get_zeroed_page(GFP_KERNEL);
159 	if (!options)
160 		goto error_no_options;
161 
162 	vnode = AFS_FS_I(mntpt->d_inode);
163 	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
164 		/* if the directory is a pseudo directory, use the d_name */
165 		static const char afs_root_cell[] = ":root.cell.";
166 		unsigned size = mntpt->d_name.len;
167 
168 		ret = -ENOENT;
169 		if (size < 2 || size > AFS_MAXCELLNAME)
170 			goto error_no_page;
171 
172 		if (mntpt->d_name.name[0] == '.') {
173 			devname[0] = '#';
174 			memcpy(devname + 1, mntpt->d_name.name, size - 1);
175 			memcpy(devname + size, afs_root_cell,
176 			       sizeof(afs_root_cell));
177 			rwpath = true;
178 		} else {
179 			devname[0] = '%';
180 			memcpy(devname + 1, mntpt->d_name.name, size);
181 			memcpy(devname + size + 1, afs_root_cell,
182 			       sizeof(afs_root_cell));
183 		}
184 	} else {
185 		/* read the contents of the AFS special symlink */
186 		loff_t size = i_size_read(mntpt->d_inode);
187 		char *buf;
188 
189 		ret = -EINVAL;
190 		if (size > PAGE_SIZE - 1)
191 			goto error_no_page;
192 
193 		page = read_mapping_page(mntpt->d_inode->i_mapping, 0, NULL);
194 		if (IS_ERR(page)) {
195 			ret = PTR_ERR(page);
196 			goto error_no_page;
197 		}
198 
199 		ret = -EIO;
200 		if (PageError(page))
201 			goto error;
202 
203 		buf = kmap_atomic(page);
204 		memcpy(devname, buf, size);
205 		kunmap_atomic(buf);
206 		page_cache_release(page);
207 		page = NULL;
208 	}
209 
210 	/* work out what options we want */
211 	super = AFS_FS_S(mntpt->d_sb);
212 	memcpy(options, "cell=", 5);
213 	strcpy(options + 5, super->volume->cell->name);
214 	if (super->volume->type == AFSVL_RWVOL || rwpath)
215 		strcat(options, ",rwpath");
216 
217 	/* try and do the mount */
218 	_debug("--- attempting mount %s -o %s ---", devname, options);
219 	mnt = vfs_kern_mount(&afs_fs_type, 0, devname, options);
220 	_debug("--- mount result %p ---", mnt);
221 
222 	free_page((unsigned long) devname);
223 	free_page((unsigned long) options);
224 	_leave(" = %p", mnt);
225 	return mnt;
226 
227 error:
228 	page_cache_release(page);
229 error_no_page:
230 	free_page((unsigned long) options);
231 error_no_options:
232 	free_page((unsigned long) devname);
233 error_no_devname:
234 	_leave(" = %d", ret);
235 	return ERR_PTR(ret);
236 }
237 
238 /*
239  * handle an automount point
240  */
241 struct vfsmount *afs_d_automount(struct path *path)
242 {
243 	struct vfsmount *newmnt;
244 
245 	_enter("{%s}", path->dentry->d_name.name);
246 
247 	newmnt = afs_mntpt_do_automount(path->dentry);
248 	if (IS_ERR(newmnt))
249 		return newmnt;
250 
251 	mntget(newmnt); /* prevent immediate expiration */
252 	mnt_set_expiry(newmnt, &afs_vfsmounts);
253 	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
254 			   afs_mntpt_expiry_timeout * HZ);
255 	_leave(" = %p", newmnt);
256 	return newmnt;
257 }
258 
259 /*
260  * handle mountpoint expiry timer going off
261  */
262 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
263 {
264 	_enter("");
265 
266 	if (!list_empty(&afs_vfsmounts)) {
267 		mark_mounts_for_expiry(&afs_vfsmounts);
268 		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
269 				   afs_mntpt_expiry_timeout * HZ);
270 	}
271 
272 	_leave("");
273 }
274 
275 /*
276  * kill the AFS mountpoint timer if it's still running
277  */
278 void afs_mntpt_kill_timer(void)
279 {
280 	_enter("");
281 
282 	ASSERT(list_empty(&afs_vfsmounts));
283 	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
284 }
285