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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;
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}