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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#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}
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}