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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
18#include "kernfs-internal.h"
19
20struct kmem_cache *kernfs_node_cache;
21
22static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
23{
24 struct kernfs_root *root = kernfs_info(sb)->root;
25 struct kernfs_syscall_ops *scops = root->syscall_ops;
26
27 if (scops && scops->remount_fs)
28 return scops->remount_fs(root, flags, data);
29 return 0;
30}
31
32static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
33{
34 struct kernfs_root *root = kernfs_root(dentry->d_fsdata);
35 struct kernfs_syscall_ops *scops = root->syscall_ops;
36
37 if (scops && scops->show_options)
38 return scops->show_options(sf, root);
39 return 0;
40}
41
42const struct super_operations kernfs_sops = {
43 .statfs = simple_statfs,
44 .drop_inode = generic_delete_inode,
45 .evict_inode = kernfs_evict_inode,
46
47 .remount_fs = kernfs_sop_remount_fs,
48 .show_options = kernfs_sop_show_options,
49};
50
51/**
52 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
53 * @sb: the super_block in question
54 *
55 * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
56 * %NULL is returned.
57 */
58struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
59{
60 if (sb->s_op == &kernfs_sops)
61 return kernfs_info(sb)->root;
62 return NULL;
63}
64
65static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
66{
67 struct kernfs_super_info *info = kernfs_info(sb);
68 struct inode *inode;
69 struct dentry *root;
70
71 sb->s_blocksize = PAGE_CACHE_SIZE;
72 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
73 sb->s_magic = magic;
74 sb->s_op = &kernfs_sops;
75 sb->s_time_gran = 1;
76
77 /* get root inode, initialize and unlock it */
78 mutex_lock(&kernfs_mutex);
79 inode = kernfs_get_inode(sb, info->root->kn);
80 mutex_unlock(&kernfs_mutex);
81 if (!inode) {
82 pr_debug("kernfs: could not get root inode\n");
83 return -ENOMEM;
84 }
85
86 /* instantiate and link root dentry */
87 root = d_make_root(inode);
88 if (!root) {
89 pr_debug("%s: could not get root dentry!\n", __func__);
90 return -ENOMEM;
91 }
92 kernfs_get(info->root->kn);
93 root->d_fsdata = info->root->kn;
94 sb->s_root = root;
95 sb->s_d_op = &kernfs_dops;
96 return 0;
97}
98
99static int kernfs_test_super(struct super_block *sb, void *data)
100{
101 struct kernfs_super_info *sb_info = kernfs_info(sb);
102 struct kernfs_super_info *info = data;
103
104 return sb_info->root == info->root && sb_info->ns == info->ns;
105}
106
107static int kernfs_set_super(struct super_block *sb, void *data)
108{
109 int error;
110 error = set_anon_super(sb, data);
111 if (!error)
112 sb->s_fs_info = data;
113 return error;
114}
115
116/**
117 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
118 * @sb: super_block of interest
119 *
120 * Return the namespace tag associated with kernfs super_block @sb.
121 */
122const void *kernfs_super_ns(struct super_block *sb)
123{
124 struct kernfs_super_info *info = kernfs_info(sb);
125
126 return info->ns;
127}
128
129/**
130 * kernfs_mount_ns - kernfs mount helper
131 * @fs_type: file_system_type of the fs being mounted
132 * @flags: mount flags specified for the mount
133 * @root: kernfs_root of the hierarchy being mounted
134 * @magic: file system specific magic number
135 * @new_sb_created: tell the caller if we allocated a new superblock
136 * @ns: optional namespace tag of the mount
137 *
138 * This is to be called from each kernfs user's file_system_type->mount()
139 * implementation, which should pass through the specified @fs_type and
140 * @flags, and specify the hierarchy and namespace tag to mount via @root
141 * and @ns, respectively.
142 *
143 * The return value can be passed to the vfs layer verbatim.
144 */
145struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
146 struct kernfs_root *root, unsigned long magic,
147 bool *new_sb_created, const void *ns)
148{
149 struct super_block *sb;
150 struct kernfs_super_info *info;
151 int error;
152
153 info = kzalloc(sizeof(*info), GFP_KERNEL);
154 if (!info)
155 return ERR_PTR(-ENOMEM);
156
157 info->root = root;
158 info->ns = ns;
159
160 sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
161 if (IS_ERR(sb) || sb->s_fs_info != info)
162 kfree(info);
163 if (IS_ERR(sb))
164 return ERR_CAST(sb);
165
166 if (new_sb_created)
167 *new_sb_created = !sb->s_root;
168
169 if (!sb->s_root) {
170 error = kernfs_fill_super(sb, magic);
171 if (error) {
172 deactivate_locked_super(sb);
173 return ERR_PTR(error);
174 }
175 sb->s_flags |= MS_ACTIVE;
176 }
177
178 return dget(sb->s_root);
179}
180
181/**
182 * kernfs_kill_sb - kill_sb for kernfs
183 * @sb: super_block being killed
184 *
185 * This can be used directly for file_system_type->kill_sb(). If a kernfs
186 * user needs extra cleanup, it can implement its own kill_sb() and call
187 * this function at the end.
188 */
189void kernfs_kill_sb(struct super_block *sb)
190{
191 struct kernfs_super_info *info = kernfs_info(sb);
192 struct kernfs_node *root_kn = sb->s_root->d_fsdata;
193
194 /*
195 * Remove the superblock from fs_supers/s_instances
196 * so we can't find it, before freeing kernfs_super_info.
197 */
198 kill_anon_super(sb);
199 kfree(info);
200 kernfs_put(root_kn);
201}
202
203void __init kernfs_init(void)
204{
205 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
206 sizeof(struct kernfs_node),
207 0, SLAB_PANIC, NULL);
208 kernfs_inode_init();
209}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * fs/kernfs/mount.c - kernfs mount implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10#include <linux/fs.h>
11#include <linux/mount.h>
12#include <linux/init.h>
13#include <linux/magic.h>
14#include <linux/slab.h>
15#include <linux/pagemap.h>
16#include <linux/namei.h>
17#include <linux/seq_file.h>
18#include <linux/exportfs.h>
19
20#include "kernfs-internal.h"
21
22struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
23struct kernfs_global_locks *kernfs_locks;
24
25static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
26{
27 struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
28 struct kernfs_syscall_ops *scops = root->syscall_ops;
29
30 if (scops && scops->show_options)
31 return scops->show_options(sf, root);
32 return 0;
33}
34
35static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
36{
37 struct kernfs_node *node = kernfs_dentry_node(dentry);
38 struct kernfs_root *root = kernfs_root(node);
39 struct kernfs_syscall_ops *scops = root->syscall_ops;
40
41 if (scops && scops->show_path)
42 return scops->show_path(sf, node, root);
43
44 seq_dentry(sf, dentry, " \t\n\\");
45 return 0;
46}
47
48const struct super_operations kernfs_sops = {
49 .statfs = simple_statfs,
50 .drop_inode = generic_delete_inode,
51 .evict_inode = kernfs_evict_inode,
52
53 .show_options = kernfs_sop_show_options,
54 .show_path = kernfs_sop_show_path,
55};
56
57static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
58 struct inode *parent)
59{
60 struct kernfs_node *kn = inode->i_private;
61
62 if (*max_len < 2) {
63 *max_len = 2;
64 return FILEID_INVALID;
65 }
66
67 *max_len = 2;
68 *(u64 *)fh = kn->id;
69 return FILEID_KERNFS;
70}
71
72static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
73 struct fid *fid, int fh_len,
74 int fh_type, bool get_parent)
75{
76 struct kernfs_super_info *info = kernfs_info(sb);
77 struct kernfs_node *kn;
78 struct inode *inode;
79 u64 id;
80
81 if (fh_len < 2)
82 return NULL;
83
84 switch (fh_type) {
85 case FILEID_KERNFS:
86 id = *(u64 *)fid;
87 break;
88 case FILEID_INO32_GEN:
89 case FILEID_INO32_GEN_PARENT:
90 /*
91 * blk_log_action() exposes "LOW32,HIGH32" pair without
92 * type and userland can call us with generic fid
93 * constructed from them. Combine it back to ID. See
94 * blk_log_action().
95 */
96 id = ((u64)fid->i32.gen << 32) | fid->i32.ino;
97 break;
98 default:
99 return NULL;
100 }
101
102 kn = kernfs_find_and_get_node_by_id(info->root, id);
103 if (!kn)
104 return ERR_PTR(-ESTALE);
105
106 if (get_parent) {
107 struct kernfs_node *parent;
108
109 parent = kernfs_get_parent(kn);
110 kernfs_put(kn);
111 kn = parent;
112 if (!kn)
113 return ERR_PTR(-ESTALE);
114 }
115
116 inode = kernfs_get_inode(sb, kn);
117 kernfs_put(kn);
118 if (!inode)
119 return ERR_PTR(-ESTALE);
120
121 return d_obtain_alias(inode);
122}
123
124static struct dentry *kernfs_fh_to_dentry(struct super_block *sb,
125 struct fid *fid, int fh_len,
126 int fh_type)
127{
128 return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, false);
129}
130
131static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
132 struct fid *fid, int fh_len,
133 int fh_type)
134{
135 return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
136}
137
138static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
139{
140 struct kernfs_node *kn = kernfs_dentry_node(child);
141
142 return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
143}
144
145static const struct export_operations kernfs_export_ops = {
146 .encode_fh = kernfs_encode_fh,
147 .fh_to_dentry = kernfs_fh_to_dentry,
148 .fh_to_parent = kernfs_fh_to_parent,
149 .get_parent = kernfs_get_parent_dentry,
150};
151
152/**
153 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
154 * @sb: the super_block in question
155 *
156 * Return: the kernfs_root associated with @sb. If @sb is not a kernfs one,
157 * %NULL is returned.
158 */
159struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
160{
161 if (sb->s_op == &kernfs_sops)
162 return kernfs_info(sb)->root;
163 return NULL;
164}
165
166/*
167 * find the next ancestor in the path down to @child, where @parent was the
168 * ancestor whose descendant we want to find.
169 *
170 * Say the path is /a/b/c/d. @child is d, @parent is %NULL. We return the root
171 * node. If @parent is b, then we return the node for c.
172 * Passing in d as @parent is not ok.
173 */
174static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
175 struct kernfs_node *parent)
176{
177 if (child == parent) {
178 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
179 return NULL;
180 }
181
182 while (child->parent != parent) {
183 if (!child->parent)
184 return NULL;
185 child = child->parent;
186 }
187
188 return child;
189}
190
191/**
192 * kernfs_node_dentry - get a dentry for the given kernfs_node
193 * @kn: kernfs_node for which a dentry is needed
194 * @sb: the kernfs super_block
195 *
196 * Return: the dentry pointer
197 */
198struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
199 struct super_block *sb)
200{
201 struct dentry *dentry;
202 struct kernfs_node *knparent = NULL;
203
204 BUG_ON(sb->s_op != &kernfs_sops);
205
206 dentry = dget(sb->s_root);
207
208 /* Check if this is the root kernfs_node */
209 if (!kn->parent)
210 return dentry;
211
212 knparent = find_next_ancestor(kn, NULL);
213 if (WARN_ON(!knparent)) {
214 dput(dentry);
215 return ERR_PTR(-EINVAL);
216 }
217
218 do {
219 struct dentry *dtmp;
220 struct kernfs_node *kntmp;
221
222 if (kn == knparent)
223 return dentry;
224 kntmp = find_next_ancestor(kn, knparent);
225 if (WARN_ON(!kntmp)) {
226 dput(dentry);
227 return ERR_PTR(-EINVAL);
228 }
229 dtmp = lookup_positive_unlocked(kntmp->name, dentry,
230 strlen(kntmp->name));
231 dput(dentry);
232 if (IS_ERR(dtmp))
233 return dtmp;
234 knparent = kntmp;
235 dentry = dtmp;
236 } while (true);
237}
238
239static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
240{
241 struct kernfs_super_info *info = kernfs_info(sb);
242 struct kernfs_root *kf_root = kfc->root;
243 struct inode *inode;
244 struct dentry *root;
245
246 info->sb = sb;
247 /* Userspace would break if executables or devices appear on sysfs */
248 sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
249 sb->s_blocksize = PAGE_SIZE;
250 sb->s_blocksize_bits = PAGE_SHIFT;
251 sb->s_magic = kfc->magic;
252 sb->s_op = &kernfs_sops;
253 sb->s_xattr = kernfs_xattr_handlers;
254 if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
255 sb->s_export_op = &kernfs_export_ops;
256 sb->s_time_gran = 1;
257
258 /* sysfs dentries and inodes don't require IO to create */
259 sb->s_shrink.seeks = 0;
260
261 /* get root inode, initialize and unlock it */
262 down_read(&kf_root->kernfs_rwsem);
263 inode = kernfs_get_inode(sb, info->root->kn);
264 up_read(&kf_root->kernfs_rwsem);
265 if (!inode) {
266 pr_debug("kernfs: could not get root inode\n");
267 return -ENOMEM;
268 }
269
270 /* instantiate and link root dentry */
271 root = d_make_root(inode);
272 if (!root) {
273 pr_debug("%s: could not get root dentry!\n", __func__);
274 return -ENOMEM;
275 }
276 sb->s_root = root;
277 sb->s_d_op = &kernfs_dops;
278 return 0;
279}
280
281static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
282{
283 struct kernfs_super_info *sb_info = kernfs_info(sb);
284 struct kernfs_super_info *info = fc->s_fs_info;
285
286 return sb_info->root == info->root && sb_info->ns == info->ns;
287}
288
289static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
290{
291 struct kernfs_fs_context *kfc = fc->fs_private;
292
293 kfc->ns_tag = NULL;
294 return set_anon_super_fc(sb, fc);
295}
296
297/**
298 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
299 * @sb: super_block of interest
300 *
301 * Return: the namespace tag associated with kernfs super_block @sb.
302 */
303const void *kernfs_super_ns(struct super_block *sb)
304{
305 struct kernfs_super_info *info = kernfs_info(sb);
306
307 return info->ns;
308}
309
310/**
311 * kernfs_get_tree - kernfs filesystem access/retrieval helper
312 * @fc: The filesystem context.
313 *
314 * This is to be called from each kernfs user's fs_context->ops->get_tree()
315 * implementation, which should set the specified ->@fs_type and ->@flags, and
316 * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
317 * respectively.
318 *
319 * Return: %0 on success, -errno on failure.
320 */
321int kernfs_get_tree(struct fs_context *fc)
322{
323 struct kernfs_fs_context *kfc = fc->fs_private;
324 struct super_block *sb;
325 struct kernfs_super_info *info;
326 int error;
327
328 info = kzalloc(sizeof(*info), GFP_KERNEL);
329 if (!info)
330 return -ENOMEM;
331
332 info->root = kfc->root;
333 info->ns = kfc->ns_tag;
334 INIT_LIST_HEAD(&info->node);
335
336 fc->s_fs_info = info;
337 sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
338 if (IS_ERR(sb))
339 return PTR_ERR(sb);
340
341 if (!sb->s_root) {
342 struct kernfs_super_info *info = kernfs_info(sb);
343 struct kernfs_root *root = kfc->root;
344
345 kfc->new_sb_created = true;
346
347 error = kernfs_fill_super(sb, kfc);
348 if (error) {
349 deactivate_locked_super(sb);
350 return error;
351 }
352 sb->s_flags |= SB_ACTIVE;
353
354 down_write(&root->kernfs_rwsem);
355 list_add(&info->node, &info->root->supers);
356 up_write(&root->kernfs_rwsem);
357 }
358
359 fc->root = dget(sb->s_root);
360 return 0;
361}
362
363void kernfs_free_fs_context(struct fs_context *fc)
364{
365 /* Note that we don't deal with kfc->ns_tag here. */
366 kfree(fc->s_fs_info);
367 fc->s_fs_info = NULL;
368}
369
370/**
371 * kernfs_kill_sb - kill_sb for kernfs
372 * @sb: super_block being killed
373 *
374 * This can be used directly for file_system_type->kill_sb(). If a kernfs
375 * user needs extra cleanup, it can implement its own kill_sb() and call
376 * this function at the end.
377 */
378void kernfs_kill_sb(struct super_block *sb)
379{
380 struct kernfs_super_info *info = kernfs_info(sb);
381 struct kernfs_root *root = info->root;
382
383 down_write(&root->kernfs_rwsem);
384 list_del(&info->node);
385 up_write(&root->kernfs_rwsem);
386
387 /*
388 * Remove the superblock from fs_supers/s_instances
389 * so we can't find it, before freeing kernfs_super_info.
390 */
391 kill_anon_super(sb);
392 kfree(info);
393}
394
395static void __init kernfs_mutex_init(void)
396{
397 int count;
398
399 for (count = 0; count < NR_KERNFS_LOCKS; count++)
400 mutex_init(&kernfs_locks->open_file_mutex[count]);
401}
402
403static void __init kernfs_lock_init(void)
404{
405 kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
406 WARN_ON(!kernfs_locks);
407
408 kernfs_mutex_init();
409}
410
411void __init kernfs_init(void)
412{
413 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
414 sizeof(struct kernfs_node),
415 0, SLAB_PANIC, NULL);
416
417 /* Creates slab cache for kernfs inode attributes */
418 kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
419 sizeof(struct kernfs_iattrs),
420 0, SLAB_PANIC, NULL);
421
422 kernfs_lock_init();
423}