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1/*
2 * fs/kernfs/mount.c - kernfs mount implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7 *
8 * This file is released under the GPLv2.
9 */
10
11#include <linux/fs.h>
12#include <linux/mount.h>
13#include <linux/init.h>
14#include <linux/magic.h>
15#include <linux/slab.h>
16#include <linux/pagemap.h>
17#include <linux/namei.h>
18#include <linux/seq_file.h>
19
20#include "kernfs-internal.h"
21
22struct kmem_cache *kernfs_node_cache;
23
24static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
25{
26 struct kernfs_root *root = kernfs_info(sb)->root;
27 struct kernfs_syscall_ops *scops = root->syscall_ops;
28
29 if (scops && scops->remount_fs)
30 return scops->remount_fs(root, flags, data);
31 return 0;
32}
33
34static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
35{
36 struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
37 struct kernfs_syscall_ops *scops = root->syscall_ops;
38
39 if (scops && scops->show_options)
40 return scops->show_options(sf, root);
41 return 0;
42}
43
44static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
45{
46 struct kernfs_node *node = dentry->d_fsdata;
47 struct kernfs_root *root = kernfs_root(node);
48 struct kernfs_syscall_ops *scops = root->syscall_ops;
49
50 if (scops && scops->show_path)
51 return scops->show_path(sf, node, root);
52
53 seq_dentry(sf, dentry, " \t\n\\");
54 return 0;
55}
56
57const struct super_operations kernfs_sops = {
58 .statfs = simple_statfs,
59 .drop_inode = generic_delete_inode,
60 .evict_inode = kernfs_evict_inode,
61
62 .remount_fs = kernfs_sop_remount_fs,
63 .show_options = kernfs_sop_show_options,
64 .show_path = kernfs_sop_show_path,
65};
66
67/**
68 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
69 * @sb: the super_block in question
70 *
71 * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
72 * %NULL is returned.
73 */
74struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
75{
76 if (sb->s_op == &kernfs_sops)
77 return kernfs_info(sb)->root;
78 return NULL;
79}
80
81/*
82 * find the next ancestor in the path down to @child, where @parent was the
83 * ancestor whose descendant we want to find.
84 *
85 * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
86 * node. If @parent is b, then we return the node for c.
87 * Passing in d as @parent is not ok.
88 */
89static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
90 struct kernfs_node *parent)
91{
92 if (child == parent) {
93 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
94 return NULL;
95 }
96
97 while (child->parent != parent) {
98 if (!child->parent)
99 return NULL;
100 child = child->parent;
101 }
102
103 return child;
104}
105
106/**
107 * kernfs_node_dentry - get a dentry for the given kernfs_node
108 * @kn: kernfs_node for which a dentry is needed
109 * @sb: the kernfs super_block
110 */
111struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
112 struct super_block *sb)
113{
114 struct dentry *dentry;
115 struct kernfs_node *knparent = NULL;
116
117 BUG_ON(sb->s_op != &kernfs_sops);
118
119 dentry = dget(sb->s_root);
120
121 /* Check if this is the root kernfs_node */
122 if (!kn->parent)
123 return dentry;
124
125 knparent = find_next_ancestor(kn, NULL);
126 if (WARN_ON(!knparent))
127 return ERR_PTR(-EINVAL);
128
129 do {
130 struct dentry *dtmp;
131 struct kernfs_node *kntmp;
132
133 if (kn == knparent)
134 return dentry;
135 kntmp = find_next_ancestor(kn, knparent);
136 if (WARN_ON(!kntmp))
137 return ERR_PTR(-EINVAL);
138 mutex_lock(&d_inode(dentry)->i_mutex);
139 dtmp = lookup_one_len(kntmp->name, dentry, strlen(kntmp->name));
140 mutex_unlock(&d_inode(dentry)->i_mutex);
141 dput(dentry);
142 if (IS_ERR(dtmp))
143 return dtmp;
144 knparent = kntmp;
145 dentry = dtmp;
146 } while (true);
147}
148
149static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
150{
151 struct kernfs_super_info *info = kernfs_info(sb);
152 struct inode *inode;
153 struct dentry *root;
154
155 info->sb = sb;
156 sb->s_blocksize = PAGE_SIZE;
157 sb->s_blocksize_bits = PAGE_SHIFT;
158 sb->s_magic = magic;
159 sb->s_op = &kernfs_sops;
160 sb->s_time_gran = 1;
161
162 /* get root inode, initialize and unlock it */
163 mutex_lock(&kernfs_mutex);
164 inode = kernfs_get_inode(sb, info->root->kn);
165 mutex_unlock(&kernfs_mutex);
166 if (!inode) {
167 pr_debug("kernfs: could not get root inode\n");
168 return -ENOMEM;
169 }
170
171 /* instantiate and link root dentry */
172 root = d_make_root(inode);
173 if (!root) {
174 pr_debug("%s: could not get root dentry!\n", __func__);
175 return -ENOMEM;
176 }
177 kernfs_get(info->root->kn);
178 root->d_fsdata = info->root->kn;
179 sb->s_root = root;
180 sb->s_d_op = &kernfs_dops;
181 return 0;
182}
183
184static int kernfs_test_super(struct super_block *sb, void *data)
185{
186 struct kernfs_super_info *sb_info = kernfs_info(sb);
187 struct kernfs_super_info *info = data;
188
189 return sb_info->root == info->root && sb_info->ns == info->ns;
190}
191
192static int kernfs_set_super(struct super_block *sb, void *data)
193{
194 int error;
195 error = set_anon_super(sb, data);
196 if (!error)
197 sb->s_fs_info = data;
198 return error;
199}
200
201/**
202 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
203 * @sb: super_block of interest
204 *
205 * Return the namespace tag associated with kernfs super_block @sb.
206 */
207const void *kernfs_super_ns(struct super_block *sb)
208{
209 struct kernfs_super_info *info = kernfs_info(sb);
210
211 return info->ns;
212}
213
214/**
215 * kernfs_mount_ns - kernfs mount helper
216 * @fs_type: file_system_type of the fs being mounted
217 * @flags: mount flags specified for the mount
218 * @root: kernfs_root of the hierarchy being mounted
219 * @magic: file system specific magic number
220 * @new_sb_created: tell the caller if we allocated a new superblock
221 * @ns: optional namespace tag of the mount
222 *
223 * This is to be called from each kernfs user's file_system_type->mount()
224 * implementation, which should pass through the specified @fs_type and
225 * @flags, and specify the hierarchy and namespace tag to mount via @root
226 * and @ns, respectively.
227 *
228 * The return value can be passed to the vfs layer verbatim.
229 */
230struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
231 struct kernfs_root *root, unsigned long magic,
232 bool *new_sb_created, const void *ns)
233{
234 struct super_block *sb;
235 struct kernfs_super_info *info;
236 int error;
237
238 info = kzalloc(sizeof(*info), GFP_KERNEL);
239 if (!info)
240 return ERR_PTR(-ENOMEM);
241
242 info->root = root;
243 info->ns = ns;
244
245 sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
246 if (IS_ERR(sb) || sb->s_fs_info != info)
247 kfree(info);
248 if (IS_ERR(sb))
249 return ERR_CAST(sb);
250
251 if (new_sb_created)
252 *new_sb_created = !sb->s_root;
253
254 if (!sb->s_root) {
255 struct kernfs_super_info *info = kernfs_info(sb);
256
257 error = kernfs_fill_super(sb, magic);
258 if (error) {
259 deactivate_locked_super(sb);
260 return ERR_PTR(error);
261 }
262 sb->s_flags |= MS_ACTIVE;
263
264 mutex_lock(&kernfs_mutex);
265 list_add(&info->node, &root->supers);
266 mutex_unlock(&kernfs_mutex);
267 }
268
269 return dget(sb->s_root);
270}
271
272/**
273 * kernfs_kill_sb - kill_sb for kernfs
274 * @sb: super_block being killed
275 *
276 * This can be used directly for file_system_type->kill_sb(). If a kernfs
277 * user needs extra cleanup, it can implement its own kill_sb() and call
278 * this function at the end.
279 */
280void kernfs_kill_sb(struct super_block *sb)
281{
282 struct kernfs_super_info *info = kernfs_info(sb);
283 struct kernfs_node *root_kn = sb->s_root->d_fsdata;
284
285 mutex_lock(&kernfs_mutex);
286 list_del(&info->node);
287 mutex_unlock(&kernfs_mutex);
288
289 /*
290 * Remove the superblock from fs_supers/s_instances
291 * so we can't find it, before freeing kernfs_super_info.
292 */
293 kill_anon_super(sb);
294 kfree(info);
295 kernfs_put(root_kn);
296}
297
298/**
299 * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
300 * @kernfs_root: the kernfs_root in question
301 * @ns: the namespace tag
302 *
303 * Pin the superblock so the superblock won't be destroyed in subsequent
304 * operations. This can be used to block ->kill_sb() which may be useful
305 * for kernfs users which dynamically manage superblocks.
306 *
307 * Returns NULL if there's no superblock associated to this kernfs_root, or
308 * -EINVAL if the superblock is being freed.
309 */
310struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
311{
312 struct kernfs_super_info *info;
313 struct super_block *sb = NULL;
314
315 mutex_lock(&kernfs_mutex);
316 list_for_each_entry(info, &root->supers, node) {
317 if (info->ns == ns) {
318 sb = info->sb;
319 if (!atomic_inc_not_zero(&info->sb->s_active))
320 sb = ERR_PTR(-EINVAL);
321 break;
322 }
323 }
324 mutex_unlock(&kernfs_mutex);
325 return sb;
326}
327
328void __init kernfs_init(void)
329{
330 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
331 sizeof(struct kernfs_node),
332 0, SLAB_PANIC, NULL);
333}
1/*
2 * fs/kernfs/mount.c - kernfs mount implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7 *
8 * This file is released under the GPLv2.
9 */
10
11#include <linux/fs.h>
12#include <linux/mount.h>
13#include <linux/init.h>
14#include <linux/magic.h>
15#include <linux/slab.h>
16#include <linux/pagemap.h>
17#include <linux/namei.h>
18#include <linux/seq_file.h>
19
20#include "kernfs-internal.h"
21
22struct kmem_cache *kernfs_node_cache;
23
24static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
25{
26 struct kernfs_root *root = kernfs_info(sb)->root;
27 struct kernfs_syscall_ops *scops = root->syscall_ops;
28
29 if (scops && scops->remount_fs)
30 return scops->remount_fs(root, flags, data);
31 return 0;
32}
33
34static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
35{
36 struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
37 struct kernfs_syscall_ops *scops = root->syscall_ops;
38
39 if (scops && scops->show_options)
40 return scops->show_options(sf, root);
41 return 0;
42}
43
44static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
45{
46 struct kernfs_node *node = dentry->d_fsdata;
47 struct kernfs_root *root = kernfs_root(node);
48 struct kernfs_syscall_ops *scops = root->syscall_ops;
49
50 if (scops && scops->show_path)
51 return scops->show_path(sf, node, root);
52
53 seq_dentry(sf, dentry, " \t\n\\");
54 return 0;
55}
56
57const struct super_operations kernfs_sops = {
58 .statfs = simple_statfs,
59 .drop_inode = generic_delete_inode,
60 .evict_inode = kernfs_evict_inode,
61
62 .remount_fs = kernfs_sop_remount_fs,
63 .show_options = kernfs_sop_show_options,
64 .show_path = kernfs_sop_show_path,
65};
66
67/**
68 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
69 * @sb: the super_block in question
70 *
71 * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
72 * %NULL is returned.
73 */
74struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
75{
76 if (sb->s_op == &kernfs_sops)
77 return kernfs_info(sb)->root;
78 return NULL;
79}
80
81/*
82 * find the next ancestor in the path down to @child, where @parent was the
83 * ancestor whose descendant we want to find.
84 *
85 * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
86 * node. If @parent is b, then we return the node for c.
87 * Passing in d as @parent is not ok.
88 */
89static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
90 struct kernfs_node *parent)
91{
92 if (child == parent) {
93 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
94 return NULL;
95 }
96
97 while (child->parent != parent) {
98 if (!child->parent)
99 return NULL;
100 child = child->parent;
101 }
102
103 return child;
104}
105
106/**
107 * kernfs_node_dentry - get a dentry for the given kernfs_node
108 * @kn: kernfs_node for which a dentry is needed
109 * @sb: the kernfs super_block
110 */
111struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
112 struct super_block *sb)
113{
114 struct dentry *dentry;
115 struct kernfs_node *knparent = NULL;
116
117 BUG_ON(sb->s_op != &kernfs_sops);
118
119 dentry = dget(sb->s_root);
120
121 /* Check if this is the root kernfs_node */
122 if (!kn->parent)
123 return dentry;
124
125 knparent = find_next_ancestor(kn, NULL);
126 if (WARN_ON(!knparent))
127 return ERR_PTR(-EINVAL);
128
129 do {
130 struct dentry *dtmp;
131 struct kernfs_node *kntmp;
132
133 if (kn == knparent)
134 return dentry;
135 kntmp = find_next_ancestor(kn, knparent);
136 if (WARN_ON(!kntmp))
137 return ERR_PTR(-EINVAL);
138 dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
139 strlen(kntmp->name));
140 dput(dentry);
141 if (IS_ERR(dtmp))
142 return dtmp;
143 knparent = kntmp;
144 dentry = dtmp;
145 } while (true);
146}
147
148static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
149{
150 struct kernfs_super_info *info = kernfs_info(sb);
151 struct inode *inode;
152 struct dentry *root;
153
154 info->sb = sb;
155 /* Userspace would break if executables or devices appear on sysfs */
156 sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
157 sb->s_blocksize = PAGE_SIZE;
158 sb->s_blocksize_bits = PAGE_SHIFT;
159 sb->s_magic = magic;
160 sb->s_op = &kernfs_sops;
161 sb->s_xattr = kernfs_xattr_handlers;
162 sb->s_time_gran = 1;
163
164 /* get root inode, initialize and unlock it */
165 mutex_lock(&kernfs_mutex);
166 inode = kernfs_get_inode(sb, info->root->kn);
167 mutex_unlock(&kernfs_mutex);
168 if (!inode) {
169 pr_debug("kernfs: could not get root inode\n");
170 return -ENOMEM;
171 }
172
173 /* instantiate and link root dentry */
174 root = d_make_root(inode);
175 if (!root) {
176 pr_debug("%s: could not get root dentry!\n", __func__);
177 return -ENOMEM;
178 }
179 kernfs_get(info->root->kn);
180 root->d_fsdata = info->root->kn;
181 sb->s_root = root;
182 sb->s_d_op = &kernfs_dops;
183 return 0;
184}
185
186static int kernfs_test_super(struct super_block *sb, void *data)
187{
188 struct kernfs_super_info *sb_info = kernfs_info(sb);
189 struct kernfs_super_info *info = data;
190
191 return sb_info->root == info->root && sb_info->ns == info->ns;
192}
193
194static int kernfs_set_super(struct super_block *sb, void *data)
195{
196 int error;
197 error = set_anon_super(sb, data);
198 if (!error)
199 sb->s_fs_info = data;
200 return error;
201}
202
203/**
204 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
205 * @sb: super_block of interest
206 *
207 * Return the namespace tag associated with kernfs super_block @sb.
208 */
209const void *kernfs_super_ns(struct super_block *sb)
210{
211 struct kernfs_super_info *info = kernfs_info(sb);
212
213 return info->ns;
214}
215
216/**
217 * kernfs_mount_ns - kernfs mount helper
218 * @fs_type: file_system_type of the fs being mounted
219 * @flags: mount flags specified for the mount
220 * @root: kernfs_root of the hierarchy being mounted
221 * @magic: file system specific magic number
222 * @new_sb_created: tell the caller if we allocated a new superblock
223 * @ns: optional namespace tag of the mount
224 *
225 * This is to be called from each kernfs user's file_system_type->mount()
226 * implementation, which should pass through the specified @fs_type and
227 * @flags, and specify the hierarchy and namespace tag to mount via @root
228 * and @ns, respectively.
229 *
230 * The return value can be passed to the vfs layer verbatim.
231 */
232struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
233 struct kernfs_root *root, unsigned long magic,
234 bool *new_sb_created, const void *ns)
235{
236 struct super_block *sb;
237 struct kernfs_super_info *info;
238 int error;
239
240 info = kzalloc(sizeof(*info), GFP_KERNEL);
241 if (!info)
242 return ERR_PTR(-ENOMEM);
243
244 info->root = root;
245 info->ns = ns;
246
247 sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
248 &init_user_ns, info);
249 if (IS_ERR(sb) || sb->s_fs_info != info)
250 kfree(info);
251 if (IS_ERR(sb))
252 return ERR_CAST(sb);
253
254 if (new_sb_created)
255 *new_sb_created = !sb->s_root;
256
257 if (!sb->s_root) {
258 struct kernfs_super_info *info = kernfs_info(sb);
259
260 error = kernfs_fill_super(sb, magic);
261 if (error) {
262 deactivate_locked_super(sb);
263 return ERR_PTR(error);
264 }
265 sb->s_flags |= MS_ACTIVE;
266
267 mutex_lock(&kernfs_mutex);
268 list_add(&info->node, &root->supers);
269 mutex_unlock(&kernfs_mutex);
270 }
271
272 return dget(sb->s_root);
273}
274
275/**
276 * kernfs_kill_sb - kill_sb for kernfs
277 * @sb: super_block being killed
278 *
279 * This can be used directly for file_system_type->kill_sb(). If a kernfs
280 * user needs extra cleanup, it can implement its own kill_sb() and call
281 * this function at the end.
282 */
283void kernfs_kill_sb(struct super_block *sb)
284{
285 struct kernfs_super_info *info = kernfs_info(sb);
286 struct kernfs_node *root_kn = sb->s_root->d_fsdata;
287
288 mutex_lock(&kernfs_mutex);
289 list_del(&info->node);
290 mutex_unlock(&kernfs_mutex);
291
292 /*
293 * Remove the superblock from fs_supers/s_instances
294 * so we can't find it, before freeing kernfs_super_info.
295 */
296 kill_anon_super(sb);
297 kfree(info);
298 kernfs_put(root_kn);
299}
300
301/**
302 * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
303 * @kernfs_root: the kernfs_root in question
304 * @ns: the namespace tag
305 *
306 * Pin the superblock so the superblock won't be destroyed in subsequent
307 * operations. This can be used to block ->kill_sb() which may be useful
308 * for kernfs users which dynamically manage superblocks.
309 *
310 * Returns NULL if there's no superblock associated to this kernfs_root, or
311 * -EINVAL if the superblock is being freed.
312 */
313struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
314{
315 struct kernfs_super_info *info;
316 struct super_block *sb = NULL;
317
318 mutex_lock(&kernfs_mutex);
319 list_for_each_entry(info, &root->supers, node) {
320 if (info->ns == ns) {
321 sb = info->sb;
322 if (!atomic_inc_not_zero(&info->sb->s_active))
323 sb = ERR_PTR(-EINVAL);
324 break;
325 }
326 }
327 mutex_unlock(&kernfs_mutex);
328 return sb;
329}
330
331void __init kernfs_init(void)
332{
333 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
334 sizeof(struct kernfs_node),
335 0, SLAB_PANIC, NULL);
336}