xref: /kernel/linux/linux-5.10/fs/afs/mntpt.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* mountpoint management
3 *
4 * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 */
7
8#include <linux/kernel.h>
9#include <linux/module.h>
10#include <linux/init.h>
11#include <linux/fs.h>
12#include <linux/pagemap.h>
13#include <linux/mount.h>
14#include <linux/namei.h>
15#include <linux/gfp.h>
16#include <linux/fs_context.h>
17#include "internal.h"
18
19
20static struct dentry *afs_mntpt_lookup(struct inode *dir,
21				       struct dentry *dentry,
22				       unsigned int flags);
23static int afs_mntpt_open(struct inode *inode, struct file *file);
24static void afs_mntpt_expiry_timed_out(struct work_struct *work);
25
26const struct file_operations afs_mntpt_file_operations = {
27	.open		= afs_mntpt_open,
28	.llseek		= noop_llseek,
29};
30
31const struct inode_operations afs_mntpt_inode_operations = {
32	.lookup		= afs_mntpt_lookup,
33	.readlink	= page_readlink,
34	.getattr	= afs_getattr,
35};
36
37const struct inode_operations afs_autocell_inode_operations = {
38	.getattr	= afs_getattr,
39};
40
41static LIST_HEAD(afs_vfsmounts);
42static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
43
44static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
45
46static const char afs_root_volume[] = "root.cell";
47
48/*
49 * no valid lookup procedure on this sort of dir
50 */
51static struct dentry *afs_mntpt_lookup(struct inode *dir,
52				       struct dentry *dentry,
53				       unsigned int flags)
54{
55	_enter("%p,%p{%pd2}", dir, dentry, dentry);
56	return ERR_PTR(-EREMOTE);
57}
58
59/*
60 * no valid open procedure on this sort of dir
61 */
62static int afs_mntpt_open(struct inode *inode, struct file *file)
63{
64	_enter("%p,%p{%pD2}", inode, file, file);
65	return -EREMOTE;
66}
67
68/*
69 * Set the parameters for the proposed superblock.
70 */
71static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
72{
73	struct afs_fs_context *ctx = fc->fs_private;
74	struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
75	struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
76	struct afs_cell *cell;
77	const char *p;
78	int ret;
79
80	if (fc->net_ns != src_as->net_ns) {
81		put_net(fc->net_ns);
82		fc->net_ns = get_net(src_as->net_ns);
83	}
84
85	if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
86		ctx->type = AFSVL_RWVOL;
87		ctx->force = true;
88	}
89	if (ctx->cell) {
90		afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_mntpt);
91		ctx->cell = NULL;
92	}
93	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
94		/* if the directory is a pseudo directory, use the d_name */
95		unsigned size = mntpt->d_name.len;
96
97		if (size < 2)
98			return -ENOENT;
99
100		p = mntpt->d_name.name;
101		if (mntpt->d_name.name[0] == '.') {
102			size--;
103			p++;
104			ctx->type = AFSVL_RWVOL;
105			ctx->force = true;
106		}
107		if (size > AFS_MAXCELLNAME)
108			return -ENAMETOOLONG;
109
110		cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
111		if (IS_ERR(cell)) {
112			pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
113			return PTR_ERR(cell);
114		}
115		ctx->cell = cell;
116
117		ctx->volname = afs_root_volume;
118		ctx->volnamesz = sizeof(afs_root_volume) - 1;
119	} else {
120		/* read the contents of the AFS special symlink */
121		struct page *page;
122		loff_t size = i_size_read(d_inode(mntpt));
123		char *buf;
124
125		if (src_as->cell)
126			ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);
127
128		if (size < 2 || size > PAGE_SIZE - 1)
129			return -EINVAL;
130
131		page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
132		if (IS_ERR(page))
133			return PTR_ERR(page);
134
135		if (PageError(page)) {
136			ret = afs_bad(AFS_FS_I(d_inode(mntpt)), afs_file_error_mntpt);
137			put_page(page);
138			return ret;
139		}
140
141		buf = kmap(page);
142		ret = -EINVAL;
143		if (buf[size - 1] == '.')
144			ret = vfs_parse_fs_string(fc, "source", buf, size - 1);
145		kunmap(page);
146		put_page(page);
147		if (ret < 0)
148			return ret;
149	}
150
151	return 0;
152}
153
154/*
155 * create a vfsmount to be automounted
156 */
157static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
158{
159	struct fs_context *fc;
160	struct vfsmount *mnt;
161	int ret;
162
163	BUG_ON(!d_inode(mntpt));
164
165	fc = fs_context_for_submount(&afs_fs_type, mntpt);
166	if (IS_ERR(fc))
167		return ERR_CAST(fc);
168
169	ret = afs_mntpt_set_params(fc, mntpt);
170	if (!ret)
171		mnt = fc_mount(fc);
172	else
173		mnt = ERR_PTR(ret);
174
175	put_fs_context(fc);
176	return mnt;
177}
178
179/*
180 * handle an automount point
181 */
182struct vfsmount *afs_d_automount(struct path *path)
183{
184	struct vfsmount *newmnt;
185
186	_enter("{%pd}", path->dentry);
187
188	newmnt = afs_mntpt_do_automount(path->dentry);
189	if (IS_ERR(newmnt))
190		return newmnt;
191
192	mntget(newmnt); /* prevent immediate expiration */
193	mnt_set_expiry(newmnt, &afs_vfsmounts);
194	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
195			   afs_mntpt_expiry_timeout * HZ);
196	_leave(" = %p", newmnt);
197	return newmnt;
198}
199
200/*
201 * handle mountpoint expiry timer going off
202 */
203static void afs_mntpt_expiry_timed_out(struct work_struct *work)
204{
205	_enter("");
206
207	if (!list_empty(&afs_vfsmounts)) {
208		mark_mounts_for_expiry(&afs_vfsmounts);
209		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
210				   afs_mntpt_expiry_timeout * HZ);
211	}
212
213	_leave("");
214}
215
216/*
217 * kill the AFS mountpoint timer if it's still running
218 */
219void afs_mntpt_kill_timer(void)
220{
221	_enter("");
222
223	ASSERT(list_empty(&afs_vfsmounts));
224	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
225}
226