Loading...
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}
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#include <linux/exportfs.h>
20
21#include "kernfs-internal.h"
22
23struct kmem_cache *kernfs_node_cache;
24
25static int kernfs_sop_remount_fs(struct super_block *sb, int *flags, char *data)
26{
27 struct kernfs_root *root = kernfs_info(sb)->root;
28 struct kernfs_syscall_ops *scops = root->syscall_ops;
29
30 if (scops && scops->remount_fs)
31 return scops->remount_fs(root, flags, data);
32 return 0;
33}
34
35static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
36{
37 struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
38 struct kernfs_syscall_ops *scops = root->syscall_ops;
39
40 if (scops && scops->show_options)
41 return scops->show_options(sf, root);
42 return 0;
43}
44
45static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
46{
47 struct kernfs_node *node = kernfs_dentry_node(dentry);
48 struct kernfs_root *root = kernfs_root(node);
49 struct kernfs_syscall_ops *scops = root->syscall_ops;
50
51 if (scops && scops->show_path)
52 return scops->show_path(sf, node, root);
53
54 seq_dentry(sf, dentry, " \t\n\\");
55 return 0;
56}
57
58const struct super_operations kernfs_sops = {
59 .statfs = simple_statfs,
60 .drop_inode = generic_delete_inode,
61 .evict_inode = kernfs_evict_inode,
62
63 .remount_fs = kernfs_sop_remount_fs,
64 .show_options = kernfs_sop_show_options,
65 .show_path = kernfs_sop_show_path,
66};
67
68/*
69 * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
70 * number and generation
71 */
72struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
73 const union kernfs_node_id *id)
74{
75 struct kernfs_node *kn;
76
77 kn = kernfs_find_and_get_node_by_ino(root, id->ino);
78 if (!kn)
79 return NULL;
80 if (kn->id.generation != id->generation) {
81 kernfs_put(kn);
82 return NULL;
83 }
84 return kn;
85}
86
87static struct inode *kernfs_fh_get_inode(struct super_block *sb,
88 u64 ino, u32 generation)
89{
90 struct kernfs_super_info *info = kernfs_info(sb);
91 struct inode *inode;
92 struct kernfs_node *kn;
93
94 if (ino == 0)
95 return ERR_PTR(-ESTALE);
96
97 kn = kernfs_find_and_get_node_by_ino(info->root, ino);
98 if (!kn)
99 return ERR_PTR(-ESTALE);
100 inode = kernfs_get_inode(sb, kn);
101 kernfs_put(kn);
102 if (!inode)
103 return ERR_PTR(-ESTALE);
104
105 if (generation && inode->i_generation != generation) {
106 /* we didn't find the right inode.. */
107 iput(inode);
108 return ERR_PTR(-ESTALE);
109 }
110 return inode;
111}
112
113static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
114 int fh_len, int fh_type)
115{
116 return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
117 kernfs_fh_get_inode);
118}
119
120static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
121 int fh_len, int fh_type)
122{
123 return generic_fh_to_parent(sb, fid, fh_len, fh_type,
124 kernfs_fh_get_inode);
125}
126
127static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
128{
129 struct kernfs_node *kn = kernfs_dentry_node(child);
130
131 return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
132}
133
134static const struct export_operations kernfs_export_ops = {
135 .fh_to_dentry = kernfs_fh_to_dentry,
136 .fh_to_parent = kernfs_fh_to_parent,
137 .get_parent = kernfs_get_parent_dentry,
138};
139
140/**
141 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
142 * @sb: the super_block in question
143 *
144 * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
145 * %NULL is returned.
146 */
147struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
148{
149 if (sb->s_op == &kernfs_sops)
150 return kernfs_info(sb)->root;
151 return NULL;
152}
153
154/*
155 * find the next ancestor in the path down to @child, where @parent was the
156 * ancestor whose descendant we want to find.
157 *
158 * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
159 * node. If @parent is b, then we return the node for c.
160 * Passing in d as @parent is not ok.
161 */
162static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
163 struct kernfs_node *parent)
164{
165 if (child == parent) {
166 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
167 return NULL;
168 }
169
170 while (child->parent != parent) {
171 if (!child->parent)
172 return NULL;
173 child = child->parent;
174 }
175
176 return child;
177}
178
179/**
180 * kernfs_node_dentry - get a dentry for the given kernfs_node
181 * @kn: kernfs_node for which a dentry is needed
182 * @sb: the kernfs super_block
183 */
184struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
185 struct super_block *sb)
186{
187 struct dentry *dentry;
188 struct kernfs_node *knparent = NULL;
189
190 BUG_ON(sb->s_op != &kernfs_sops);
191
192 dentry = dget(sb->s_root);
193
194 /* Check if this is the root kernfs_node */
195 if (!kn->parent)
196 return dentry;
197
198 knparent = find_next_ancestor(kn, NULL);
199 if (WARN_ON(!knparent))
200 return ERR_PTR(-EINVAL);
201
202 do {
203 struct dentry *dtmp;
204 struct kernfs_node *kntmp;
205
206 if (kn == knparent)
207 return dentry;
208 kntmp = find_next_ancestor(kn, knparent);
209 if (WARN_ON(!kntmp))
210 return ERR_PTR(-EINVAL);
211 dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
212 strlen(kntmp->name));
213 dput(dentry);
214 if (IS_ERR(dtmp))
215 return dtmp;
216 knparent = kntmp;
217 dentry = dtmp;
218 } while (true);
219}
220
221static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
222{
223 struct kernfs_super_info *info = kernfs_info(sb);
224 struct inode *inode;
225 struct dentry *root;
226
227 info->sb = sb;
228 /* Userspace would break if executables or devices appear on sysfs */
229 sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
230 sb->s_blocksize = PAGE_SIZE;
231 sb->s_blocksize_bits = PAGE_SHIFT;
232 sb->s_magic = magic;
233 sb->s_op = &kernfs_sops;
234 sb->s_xattr = kernfs_xattr_handlers;
235 if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
236 sb->s_export_op = &kernfs_export_ops;
237 sb->s_time_gran = 1;
238
239 /* get root inode, initialize and unlock it */
240 mutex_lock(&kernfs_mutex);
241 inode = kernfs_get_inode(sb, info->root->kn);
242 mutex_unlock(&kernfs_mutex);
243 if (!inode) {
244 pr_debug("kernfs: could not get root inode\n");
245 return -ENOMEM;
246 }
247
248 /* instantiate and link root dentry */
249 root = d_make_root(inode);
250 if (!root) {
251 pr_debug("%s: could not get root dentry!\n", __func__);
252 return -ENOMEM;
253 }
254 sb->s_root = root;
255 sb->s_d_op = &kernfs_dops;
256 return 0;
257}
258
259static int kernfs_test_super(struct super_block *sb, void *data)
260{
261 struct kernfs_super_info *sb_info = kernfs_info(sb);
262 struct kernfs_super_info *info = data;
263
264 return sb_info->root == info->root && sb_info->ns == info->ns;
265}
266
267static int kernfs_set_super(struct super_block *sb, void *data)
268{
269 int error;
270 error = set_anon_super(sb, data);
271 if (!error)
272 sb->s_fs_info = data;
273 return error;
274}
275
276/**
277 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
278 * @sb: super_block of interest
279 *
280 * Return the namespace tag associated with kernfs super_block @sb.
281 */
282const void *kernfs_super_ns(struct super_block *sb)
283{
284 struct kernfs_super_info *info = kernfs_info(sb);
285
286 return info->ns;
287}
288
289/**
290 * kernfs_mount_ns - kernfs mount helper
291 * @fs_type: file_system_type of the fs being mounted
292 * @flags: mount flags specified for the mount
293 * @root: kernfs_root of the hierarchy being mounted
294 * @magic: file system specific magic number
295 * @new_sb_created: tell the caller if we allocated a new superblock
296 * @ns: optional namespace tag of the mount
297 *
298 * This is to be called from each kernfs user's file_system_type->mount()
299 * implementation, which should pass through the specified @fs_type and
300 * @flags, and specify the hierarchy and namespace tag to mount via @root
301 * and @ns, respectively.
302 *
303 * The return value can be passed to the vfs layer verbatim.
304 */
305struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
306 struct kernfs_root *root, unsigned long magic,
307 bool *new_sb_created, const void *ns)
308{
309 struct super_block *sb;
310 struct kernfs_super_info *info;
311 int error;
312
313 info = kzalloc(sizeof(*info), GFP_KERNEL);
314 if (!info)
315 return ERR_PTR(-ENOMEM);
316
317 info->root = root;
318 info->ns = ns;
319 INIT_LIST_HEAD(&info->node);
320
321 sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags,
322 &init_user_ns, info);
323 if (IS_ERR(sb) || sb->s_fs_info != info)
324 kfree(info);
325 if (IS_ERR(sb))
326 return ERR_CAST(sb);
327
328 if (new_sb_created)
329 *new_sb_created = !sb->s_root;
330
331 if (!sb->s_root) {
332 struct kernfs_super_info *info = kernfs_info(sb);
333
334 error = kernfs_fill_super(sb, magic);
335 if (error) {
336 deactivate_locked_super(sb);
337 return ERR_PTR(error);
338 }
339 sb->s_flags |= SB_ACTIVE;
340
341 mutex_lock(&kernfs_mutex);
342 list_add(&info->node, &root->supers);
343 mutex_unlock(&kernfs_mutex);
344 }
345
346 return dget(sb->s_root);
347}
348
349/**
350 * kernfs_kill_sb - kill_sb for kernfs
351 * @sb: super_block being killed
352 *
353 * This can be used directly for file_system_type->kill_sb(). If a kernfs
354 * user needs extra cleanup, it can implement its own kill_sb() and call
355 * this function at the end.
356 */
357void kernfs_kill_sb(struct super_block *sb)
358{
359 struct kernfs_super_info *info = kernfs_info(sb);
360
361 mutex_lock(&kernfs_mutex);
362 list_del(&info->node);
363 mutex_unlock(&kernfs_mutex);
364
365 /*
366 * Remove the superblock from fs_supers/s_instances
367 * so we can't find it, before freeing kernfs_super_info.
368 */
369 kill_anon_super(sb);
370 kfree(info);
371}
372
373/**
374 * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
375 * @kernfs_root: the kernfs_root in question
376 * @ns: the namespace tag
377 *
378 * Pin the superblock so the superblock won't be destroyed in subsequent
379 * operations. This can be used to block ->kill_sb() which may be useful
380 * for kernfs users which dynamically manage superblocks.
381 *
382 * Returns NULL if there's no superblock associated to this kernfs_root, or
383 * -EINVAL if the superblock is being freed.
384 */
385struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
386{
387 struct kernfs_super_info *info;
388 struct super_block *sb = NULL;
389
390 mutex_lock(&kernfs_mutex);
391 list_for_each_entry(info, &root->supers, node) {
392 if (info->ns == ns) {
393 sb = info->sb;
394 if (!atomic_inc_not_zero(&info->sb->s_active))
395 sb = ERR_PTR(-EINVAL);
396 break;
397 }
398 }
399 mutex_unlock(&kernfs_mutex);
400 return sb;
401}
402
403void __init kernfs_init(void)
404{
405
406 /*
407 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
408 * can access the slab lock free. This could introduce stale nodes,
409 * please see how kernfs_find_and_get_node_by_ino filters out stale
410 * nodes.
411 */
412 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
413 sizeof(struct kernfs_node),
414 0,
415 SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
416 NULL);
417}