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