xref: /openbmc/linux/fs/afs/mntpt.c (revision ed2d2ead)
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 };
36 
37 const struct inode_operations afs_autocell_inode_operations = {
38 	.getattr	= afs_getattr,
39 };
40 
41 static LIST_HEAD(afs_vfsmounts);
42 static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
43 
44 static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
45 
46 static const char afs_root_volume[] = "root.cell";
47 
48 /*
49  * no valid lookup procedure on this sort of dir
50  */
afs_mntpt_lookup(struct inode * dir,struct dentry * dentry,unsigned int flags)51 static 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  */
afs_mntpt_open(struct inode * inode,struct file * file)62 static 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  */
afs_mntpt_set_params(struct fs_context * fc,struct dentry * mntpt)71 static 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 		buf = kmap(page);
136 		ret = -EINVAL;
137 		if (buf[size - 1] == '.')
138 			ret = vfs_parse_fs_string(fc, "source", buf, size - 1);
139 		kunmap(page);
140 		put_page(page);
141 		if (ret < 0)
142 			return ret;
143 
144 		/* Don't cross a backup volume mountpoint from a backup volume */
145 		if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL &&
146 		    ctx->type == AFSVL_BACKVOL)
147 			return -ENODEV;
148 	}
149 
150 	return 0;
151 }
152 
153 /*
154  * create a vfsmount to be automounted
155  */
afs_mntpt_do_automount(struct dentry * mntpt)156 static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
157 {
158 	struct fs_context *fc;
159 	struct vfsmount *mnt;
160 	int ret;
161 
162 	BUG_ON(!d_inode(mntpt));
163 
164 	fc = fs_context_for_submount(&afs_fs_type, mntpt);
165 	if (IS_ERR(fc))
166 		return ERR_CAST(fc);
167 
168 	ret = afs_mntpt_set_params(fc, mntpt);
169 	if (!ret)
170 		mnt = fc_mount(fc);
171 	else
172 		mnt = ERR_PTR(ret);
173 
174 	put_fs_context(fc);
175 	return mnt;
176 }
177 
178 /*
179  * handle an automount point
180  */
afs_d_automount(struct path * path)181 struct vfsmount *afs_d_automount(struct path *path)
182 {
183 	struct vfsmount *newmnt;
184 
185 	_enter("{%pd}", path->dentry);
186 
187 	newmnt = afs_mntpt_do_automount(path->dentry);
188 	if (IS_ERR(newmnt))
189 		return newmnt;
190 
191 	mntget(newmnt); /* prevent immediate expiration */
192 	mnt_set_expiry(newmnt, &afs_vfsmounts);
193 	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
194 			   afs_mntpt_expiry_timeout * HZ);
195 	_leave(" = %p", newmnt);
196 	return newmnt;
197 }
198 
199 /*
200  * handle mountpoint expiry timer going off
201  */
afs_mntpt_expiry_timed_out(struct work_struct * work)202 static void afs_mntpt_expiry_timed_out(struct work_struct *work)
203 {
204 	_enter("");
205 
206 	if (!list_empty(&afs_vfsmounts)) {
207 		mark_mounts_for_expiry(&afs_vfsmounts);
208 		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
209 				   afs_mntpt_expiry_timeout * HZ);
210 	}
211 
212 	_leave("");
213 }
214 
215 /*
216  * kill the AFS mountpoint timer if it's still running
217  */
afs_mntpt_kill_timer(void)218 void afs_mntpt_kill_timer(void)
219 {
220 	_enter("");
221 
222 	ASSERT(list_empty(&afs_vfsmounts));
223 	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
224 }
225