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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#include <linux/uuid.h>
20#include <linux/statfs.h>
21
22#include "kernfs-internal.h"
23
24struct kmem_cache *kernfs_node_cache __ro_after_init;
25struct kmem_cache *kernfs_iattrs_cache __ro_after_init;
26struct kernfs_global_locks *kernfs_locks __ro_after_init;
27
28static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
29{
30 struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
31 struct kernfs_syscall_ops *scops = root->syscall_ops;
32
33 if (scops && scops->show_options)
34 return scops->show_options(sf, root);
35 return 0;
36}
37
38static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
39{
40 struct kernfs_node *node = kernfs_dentry_node(dentry);
41 struct kernfs_root *root = kernfs_root(node);
42 struct kernfs_syscall_ops *scops = root->syscall_ops;
43
44 if (scops && scops->show_path)
45 return scops->show_path(sf, node, root);
46
47 seq_dentry(sf, dentry, " \t\n\\");
48 return 0;
49}
50
51static int kernfs_statfs(struct dentry *dentry, struct kstatfs *buf)
52{
53 simple_statfs(dentry, buf);
54 buf->f_fsid = uuid_to_fsid(dentry->d_sb->s_uuid.b);
55 return 0;
56}
57
58const struct super_operations kernfs_sops = {
59 .statfs = kernfs_statfs,
60 .drop_inode = generic_delete_inode,
61 .evict_inode = kernfs_evict_inode,
62
63 .show_options = kernfs_sop_show_options,
64 .show_path = kernfs_sop_show_path,
65};
66
67static int kernfs_encode_fh(struct inode *inode, __u32 *fh, int *max_len,
68 struct inode *parent)
69{
70 struct kernfs_node *kn = inode->i_private;
71
72 if (*max_len < 2) {
73 *max_len = 2;
74 return FILEID_INVALID;
75 }
76
77 *max_len = 2;
78 *(u64 *)fh = kn->id;
79 return FILEID_KERNFS;
80}
81
82static struct dentry *__kernfs_fh_to_dentry(struct super_block *sb,
83 struct fid *fid, int fh_len,
84 int fh_type, bool get_parent)
85{
86 struct kernfs_super_info *info = kernfs_info(sb);
87 struct kernfs_node *kn;
88 struct inode *inode;
89 u64 id;
90
91 if (fh_len < 2)
92 return NULL;
93
94 switch (fh_type) {
95 case FILEID_KERNFS:
96 id = *(u64 *)fid;
97 break;
98 case FILEID_INO32_GEN:
99 case FILEID_INO32_GEN_PARENT:
100 /*
101 * blk_log_action() exposes "LOW32,HIGH32" pair without
102 * type and userland can call us with generic fid
103 * constructed from them. Combine it back to ID. See
104 * blk_log_action().
105 */
106 id = ((u64)fid->i32.gen << 32) | fid->i32.ino;
107 break;
108 default:
109 return NULL;
110 }
111
112 kn = kernfs_find_and_get_node_by_id(info->root, id);
113 if (!kn)
114 return ERR_PTR(-ESTALE);
115
116 if (get_parent) {
117 struct kernfs_node *parent;
118
119 parent = kernfs_get_parent(kn);
120 kernfs_put(kn);
121 kn = parent;
122 if (!kn)
123 return ERR_PTR(-ESTALE);
124 }
125
126 inode = kernfs_get_inode(sb, kn);
127 kernfs_put(kn);
128 return d_obtain_alias(inode);
129}
130
131static struct dentry *kernfs_fh_to_dentry(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, false);
136}
137
138static struct dentry *kernfs_fh_to_parent(struct super_block *sb,
139 struct fid *fid, int fh_len,
140 int fh_type)
141{
142 return __kernfs_fh_to_dentry(sb, fid, fh_len, fh_type, true);
143}
144
145static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
146{
147 struct kernfs_node *kn = kernfs_dentry_node(child);
148
149 return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
150}
151
152static const struct export_operations kernfs_export_ops = {
153 .encode_fh = kernfs_encode_fh,
154 .fh_to_dentry = kernfs_fh_to_dentry,
155 .fh_to_parent = kernfs_fh_to_parent,
156 .get_parent = kernfs_get_parent_dentry,
157};
158
159/**
160 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
161 * @sb: the super_block in question
162 *
163 * Return: the kernfs_root associated with @sb. If @sb is not a kernfs one,
164 * %NULL is returned.
165 */
166struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
167{
168 if (sb->s_op == &kernfs_sops)
169 return kernfs_info(sb)->root;
170 return NULL;
171}
172
173/*
174 * find the next ancestor in the path down to @child, where @parent was the
175 * ancestor whose descendant we want to find.
176 *
177 * Say the path is /a/b/c/d. @child is d, @parent is %NULL. We return the root
178 * node. If @parent is b, then we return the node for c.
179 * Passing in d as @parent is not ok.
180 */
181static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
182 struct kernfs_node *parent)
183{
184 if (child == parent) {
185 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
186 return NULL;
187 }
188
189 while (child->parent != parent) {
190 if (!child->parent)
191 return NULL;
192 child = child->parent;
193 }
194
195 return child;
196}
197
198/**
199 * kernfs_node_dentry - get a dentry for the given kernfs_node
200 * @kn: kernfs_node for which a dentry is needed
201 * @sb: the kernfs super_block
202 *
203 * Return: the dentry pointer
204 */
205struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
206 struct super_block *sb)
207{
208 struct dentry *dentry;
209 struct kernfs_node *knparent;
210
211 BUG_ON(sb->s_op != &kernfs_sops);
212
213 dentry = dget(sb->s_root);
214
215 /* Check if this is the root kernfs_node */
216 if (!kn->parent)
217 return dentry;
218
219 knparent = find_next_ancestor(kn, NULL);
220 if (WARN_ON(!knparent)) {
221 dput(dentry);
222 return ERR_PTR(-EINVAL);
223 }
224
225 do {
226 struct dentry *dtmp;
227 struct kernfs_node *kntmp;
228
229 if (kn == knparent)
230 return dentry;
231 kntmp = find_next_ancestor(kn, knparent);
232 if (WARN_ON(!kntmp)) {
233 dput(dentry);
234 return ERR_PTR(-EINVAL);
235 }
236 dtmp = lookup_positive_unlocked(kntmp->name, dentry,
237 strlen(kntmp->name));
238 dput(dentry);
239 if (IS_ERR(dtmp))
240 return dtmp;
241 knparent = kntmp;
242 dentry = dtmp;
243 } while (true);
244}
245
246static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
247{
248 struct kernfs_super_info *info = kernfs_info(sb);
249 struct kernfs_root *kf_root = kfc->root;
250 struct inode *inode;
251 struct dentry *root;
252
253 info->sb = sb;
254 /* Userspace would break if executables or devices appear on sysfs */
255 sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
256 sb->s_blocksize = PAGE_SIZE;
257 sb->s_blocksize_bits = PAGE_SHIFT;
258 sb->s_magic = kfc->magic;
259 sb->s_op = &kernfs_sops;
260 sb->s_xattr = kernfs_xattr_handlers;
261 if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
262 sb->s_export_op = &kernfs_export_ops;
263 sb->s_time_gran = 1;
264
265 /* sysfs dentries and inodes don't require IO to create */
266 sb->s_shrink->seeks = 0;
267
268 /* get root inode, initialize and unlock it */
269 down_read(&kf_root->kernfs_rwsem);
270 inode = kernfs_get_inode(sb, info->root->kn);
271 up_read(&kf_root->kernfs_rwsem);
272 if (!inode) {
273 pr_debug("kernfs: could not get root inode\n");
274 return -ENOMEM;
275 }
276
277 /* instantiate and link root dentry */
278 root = d_make_root(inode);
279 if (!root) {
280 pr_debug("%s: could not get root dentry!\n", __func__);
281 return -ENOMEM;
282 }
283 sb->s_root = root;
284 sb->s_d_op = &kernfs_dops;
285 return 0;
286}
287
288static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
289{
290 struct kernfs_super_info *sb_info = kernfs_info(sb);
291 struct kernfs_super_info *info = fc->s_fs_info;
292
293 return sb_info->root == info->root && sb_info->ns == info->ns;
294}
295
296static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
297{
298 struct kernfs_fs_context *kfc = fc->fs_private;
299
300 kfc->ns_tag = NULL;
301 return set_anon_super_fc(sb, fc);
302}
303
304/**
305 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
306 * @sb: super_block of interest
307 *
308 * Return: the namespace tag associated with kernfs super_block @sb.
309 */
310const void *kernfs_super_ns(struct super_block *sb)
311{
312 struct kernfs_super_info *info = kernfs_info(sb);
313
314 return info->ns;
315}
316
317/**
318 * kernfs_get_tree - kernfs filesystem access/retrieval helper
319 * @fc: The filesystem context.
320 *
321 * This is to be called from each kernfs user's fs_context->ops->get_tree()
322 * implementation, which should set the specified ->@fs_type and ->@flags, and
323 * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
324 * respectively.
325 *
326 * Return: %0 on success, -errno on failure.
327 */
328int kernfs_get_tree(struct fs_context *fc)
329{
330 struct kernfs_fs_context *kfc = fc->fs_private;
331 struct super_block *sb;
332 struct kernfs_super_info *info;
333 int error;
334
335 info = kzalloc(sizeof(*info), GFP_KERNEL);
336 if (!info)
337 return -ENOMEM;
338
339 info->root = kfc->root;
340 info->ns = kfc->ns_tag;
341 INIT_LIST_HEAD(&info->node);
342
343 fc->s_fs_info = info;
344 sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
345 if (IS_ERR(sb))
346 return PTR_ERR(sb);
347
348 if (!sb->s_root) {
349 struct kernfs_super_info *info = kernfs_info(sb);
350 struct kernfs_root *root = kfc->root;
351
352 kfc->new_sb_created = true;
353
354 error = kernfs_fill_super(sb, kfc);
355 if (error) {
356 deactivate_locked_super(sb);
357 return error;
358 }
359 sb->s_flags |= SB_ACTIVE;
360
361 uuid_t uuid;
362 uuid_gen(&uuid);
363 super_set_uuid(sb, uuid.b, sizeof(uuid));
364
365 down_write(&root->kernfs_supers_rwsem);
366 list_add(&info->node, &info->root->supers);
367 up_write(&root->kernfs_supers_rwsem);
368 }
369
370 fc->root = dget(sb->s_root);
371 return 0;
372}
373
374void kernfs_free_fs_context(struct fs_context *fc)
375{
376 /* Note that we don't deal with kfc->ns_tag here. */
377 kfree(fc->s_fs_info);
378 fc->s_fs_info = NULL;
379}
380
381/**
382 * kernfs_kill_sb - kill_sb for kernfs
383 * @sb: super_block being killed
384 *
385 * This can be used directly for file_system_type->kill_sb(). If a kernfs
386 * user needs extra cleanup, it can implement its own kill_sb() and call
387 * this function at the end.
388 */
389void kernfs_kill_sb(struct super_block *sb)
390{
391 struct kernfs_super_info *info = kernfs_info(sb);
392 struct kernfs_root *root = info->root;
393
394 down_write(&root->kernfs_supers_rwsem);
395 list_del(&info->node);
396 up_write(&root->kernfs_supers_rwsem);
397
398 /*
399 * Remove the superblock from fs_supers/s_instances
400 * so we can't find it, before freeing kernfs_super_info.
401 */
402 kill_anon_super(sb);
403 kfree(info);
404}
405
406static void __init kernfs_mutex_init(void)
407{
408 int count;
409
410 for (count = 0; count < NR_KERNFS_LOCKS; count++)
411 mutex_init(&kernfs_locks->open_file_mutex[count]);
412}
413
414static void __init kernfs_lock_init(void)
415{
416 kernfs_locks = kmalloc(sizeof(struct kernfs_global_locks), GFP_KERNEL);
417 WARN_ON(!kernfs_locks);
418
419 kernfs_mutex_init();
420}
421
422void __init kernfs_init(void)
423{
424 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
425 sizeof(struct kernfs_node),
426 0, SLAB_PANIC, NULL);
427
428 /* Creates slab cache for kernfs inode attributes */
429 kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
430 sizeof(struct kernfs_iattrs),
431 0, SLAB_PANIC, NULL);
432
433 kernfs_lock_init();
434}
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}