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
20 static struct dentry *afs_mntpt_lookup(struct inode *dir,
21 struct dentry *dentry,
22 unsigned int flags);
23 static int afs_mntpt_open(struct inode *inode, struct file *file);
24 static void afs_mntpt_expiry_timed_out(struct work_struct *work);
25
26 const struct file_operations afs_mntpt_file_operations = {
27 .open = afs_mntpt_open,
28 .llseek = noop_llseek,
29 };
30
31 const struct inode_operations afs_mntpt_inode_operations = {
32 .lookup = afs_mntpt_lookup,
33 .readlink = page_readlink,
34 .getattr = afs_getattr,
35 .listxattr = afs_listxattr,
36 };
37
38 const struct inode_operations afs_autocell_inode_operations = {
39 .getattr = afs_getattr,
40 };
41
42 static LIST_HEAD(afs_vfsmounts);
43 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
44
45 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
46
47 static const char afs_root_volume[] = "root.cell";
48
49 /*
50 * no valid lookup procedure on this sort of dir
51 */
afs_mntpt_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)52 static struct dentry *afs_mntpt_lookup(struct inode *dir,
53 struct dentry *dentry,
54 unsigned int flags)
55 {
56 _enter("%p,%p{%pd2}", dir, dentry, dentry);
57 return ERR_PTR(-EREMOTE);
58 }
59
60 /*
61 * no valid open procedure on this sort of dir
62 */
afs_mntpt_open(struct inode * inode,struct file * file)63 static int afs_mntpt_open(struct inode *inode, struct file *file)
64 {
65 _enter("%p,%p{%pD2}", inode, file, file);
66 return -EREMOTE;
67 }
68
69 /*
70 * Set the parameters for the proposed superblock.
71 */
afs_mntpt_set_params(struct fs_context * fc,struct dentry * mntpt)72 static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
73 {
74 struct afs_fs_context *ctx = fc->fs_private;
75 struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
76 struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
77 struct afs_cell *cell;
78 const char *p;
79 int ret;
80
81 if (fc->net_ns != src_as->net_ns) {
82 put_net(fc->net_ns);
83 fc->net_ns = get_net(src_as->net_ns);
84 }
85
86 if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
87 ctx->type = AFSVL_RWVOL;
88 ctx->force = true;
89 }
90 if (ctx->cell) {
91 afs_unuse_cell(ctx->net, ctx->cell, afs_cell_trace_unuse_mntpt);
92 ctx->cell = NULL;
93 }
94 if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
95 /* if the directory is a pseudo directory, use the d_name */
96 unsigned size = mntpt->d_name.len;
97
98 if (size < 2)
99 return -ENOENT;
100
101 p = mntpt->d_name.name;
102 if (mntpt->d_name.name[0] == '.') {
103 size--;
104 p++;
105 ctx->type = AFSVL_RWVOL;
106 ctx->force = true;
107 }
108 if (size > AFS_MAXCELLNAME)
109 return -ENAMETOOLONG;
110
111 cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
112 if (IS_ERR(cell)) {
113 pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
114 return PTR_ERR(cell);
115 }
116 ctx->cell = cell;
117
118 ctx->volname = afs_root_volume;
119 ctx->volnamesz = sizeof(afs_root_volume) - 1;
120 } else {
121 /* read the contents of the AFS special symlink */
122 struct page *page;
123 loff_t size = i_size_read(d_inode(mntpt));
124 char *buf;
125
126 if (src_as->cell)
127 ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);
128
129 if (size < 2 || size > PAGE_SIZE - 1)
130 return -EINVAL;
131
132 page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
133 if (IS_ERR(page))
134 return PTR_ERR(page);
135
136 if (PageError(page)) {
137 ret = afs_bad(AFS_FS_I(d_inode(mntpt)), afs_file_error_mntpt);
138 put_page(page);
139 return ret;
140 }
141
142 buf = kmap(page);
143 ret = -EINVAL;
144 if (buf[size - 1] == '.')
145 ret = vfs_parse_fs_string(fc, "source", buf, size - 1);
146 kunmap(page);
147 put_page(page);
148 if (ret < 0)
149 return ret;
150 }
151
152 return 0;
153 }
154
155 /*
156 * create a vfsmount to be automounted
157 */
afs_mntpt_do_automount(struct dentry * mntpt)158 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
159 {
160 struct fs_context *fc;
161 struct vfsmount *mnt;
162 int ret;
163
164 BUG_ON(!d_inode(mntpt));
165
166 fc = fs_context_for_submount(&afs_fs_type, mntpt);
167 if (IS_ERR(fc))
168 return ERR_CAST(fc);
169
170 ret = afs_mntpt_set_params(fc, mntpt);
171 if (!ret)
172 mnt = fc_mount(fc);
173 else
174 mnt = ERR_PTR(ret);
175
176 put_fs_context(fc);
177 return mnt;
178 }
179
180 /*
181 * handle an automount point
182 */
afs_d_automount(struct path * path)183 struct vfsmount *afs_d_automount(struct path *path)
184 {
185 struct vfsmount *newmnt;
186
187 _enter("{%pd}", path->dentry);
188
189 newmnt = afs_mntpt_do_automount(path->dentry);
190 if (IS_ERR(newmnt))
191 return newmnt;
192
193 mntget(newmnt); /* prevent immediate expiration */
194 mnt_set_expiry(newmnt, &afs_vfsmounts);
195 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
196 afs_mntpt_expiry_timeout * HZ);
197 _leave(" = %p", newmnt);
198 return newmnt;
199 }
200
201 /*
202 * handle mountpoint expiry timer going off
203 */
afs_mntpt_expiry_timed_out(struct work_struct * work)204 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
205 {
206 _enter("");
207
208 if (!list_empty(&afs_vfsmounts)) {
209 mark_mounts_for_expiry(&afs_vfsmounts);
210 queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
211 afs_mntpt_expiry_timeout * HZ);
212 }
213
214 _leave("");
215 }
216
217 /*
218 * kill the AFS mountpoint timer if it's still running
219 */
afs_mntpt_kill_timer(void)220 void afs_mntpt_kill_timer(void)
221 {
222 _enter("");
223
224 ASSERT(list_empty(&afs_vfsmounts));
225 cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
226 }
227
