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Commit | Line | Data |
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b8441ed2 TH |
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 | */ | |
fa736a95 TH |
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> | |
b89b3c17 | 17 | #include <linux/namei.h> |
5e5eb352 | 18 | #include <linux/seq_file.h> |
fa736a95 TH |
19 | |
20 | #include "kernfs-internal.h" | |
21 | ||
a797bfc3 | 22 | struct kmem_cache *kernfs_node_cache; |
fa736a95 | 23 | |
6a7fed4e TH |
24 | static 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 | ||
34 | static 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) | |
60b509b2 | 40 | return scops->show_options(sf, root); |
6a7fed4e TH |
41 | return 0; |
42 | } | |
43 | ||
5e5eb352 SH |
44 | static 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 | ||
124128d4 SH |
53 | seq_dentry(sf, dentry, " \t\n\\"); |
54 | return 0; | |
5e5eb352 SH |
55 | } |
56 | ||
f41c5934 | 57 | const struct super_operations kernfs_sops = { |
fa736a95 TH |
58 | .statfs = simple_statfs, |
59 | .drop_inode = generic_delete_inode, | |
c637b8ac | 60 | .evict_inode = kernfs_evict_inode, |
6a7fed4e TH |
61 | |
62 | .remount_fs = kernfs_sop_remount_fs, | |
63 | .show_options = kernfs_sop_show_options, | |
5e5eb352 | 64 | .show_path = kernfs_sop_show_path, |
fa736a95 TH |
65 | }; |
66 | ||
0c23b225 TH |
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 | */ | |
74 | struct 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 | ||
b89b3c17 AK |
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 | */ | |
89 | static struct kernfs_node * | |
90 | find_next_ancestor(struct kernfs_node *child, 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 | */ | |
111 | struct 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 (1); | |
147 | } | |
148 | ||
26fc9cd2 | 149 | static int kernfs_fill_super(struct super_block *sb, unsigned long magic) |
fa736a95 | 150 | { |
c525aadd | 151 | struct kernfs_super_info *info = kernfs_info(sb); |
fa736a95 TH |
152 | struct inode *inode; |
153 | struct dentry *root; | |
154 | ||
7d568a83 | 155 | info->sb = sb; |
d072065a EB |
156 | /* Userspace would break if executables appear on sysfs */ |
157 | sb->s_iflags |= SB_I_NOEXEC; | |
fa736a95 TH |
158 | sb->s_blocksize = PAGE_CACHE_SIZE; |
159 | sb->s_blocksize_bits = PAGE_CACHE_SHIFT; | |
26fc9cd2 | 160 | sb->s_magic = magic; |
a797bfc3 | 161 | sb->s_op = &kernfs_sops; |
fa736a95 TH |
162 | sb->s_time_gran = 1; |
163 | ||
164 | /* get root inode, initialize and unlock it */ | |
a797bfc3 | 165 | mutex_lock(&kernfs_mutex); |
c637b8ac | 166 | inode = kernfs_get_inode(sb, info->root->kn); |
a797bfc3 | 167 | mutex_unlock(&kernfs_mutex); |
fa736a95 | 168 | if (!inode) { |
c637b8ac | 169 | pr_debug("kernfs: could not get root inode\n"); |
fa736a95 TH |
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 | } | |
324a56e1 TH |
179 | kernfs_get(info->root->kn); |
180 | root->d_fsdata = info->root->kn; | |
fa736a95 | 181 | sb->s_root = root; |
a797bfc3 | 182 | sb->s_d_op = &kernfs_dops; |
fa736a95 TH |
183 | return 0; |
184 | } | |
185 | ||
c637b8ac | 186 | static int kernfs_test_super(struct super_block *sb, void *data) |
fa736a95 | 187 | { |
c525aadd TH |
188 | struct kernfs_super_info *sb_info = kernfs_info(sb); |
189 | struct kernfs_super_info *info = data; | |
fa736a95 | 190 | |
3988fb70 | 191 | return sb_info->root == info->root && sb_info->ns == info->ns; |
fa736a95 TH |
192 | } |
193 | ||
c637b8ac | 194 | static int kernfs_set_super(struct super_block *sb, void *data) |
fa736a95 TH |
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 | */ | |
209 | const void *kernfs_super_ns(struct super_block *sb) | |
210 | { | |
c525aadd | 211 | struct kernfs_super_info *info = kernfs_info(sb); |
fa736a95 TH |
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 | |
26fc9cd2 | 221 | * @magic: file system specific magic number |
fed95bab | 222 | * @new_sb_created: tell the caller if we allocated a new superblock |
fa736a95 TH |
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 | */ | |
232 | struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags, | |
26fc9cd2 JZ |
233 | struct kernfs_root *root, unsigned long magic, |
234 | bool *new_sb_created, const void *ns) | |
fa736a95 TH |
235 | { |
236 | struct super_block *sb; | |
c525aadd | 237 | struct kernfs_super_info *info; |
fa736a95 TH |
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 | ||
302cabb7 SF |
247 | sb = sget_userns(fs_type, kernfs_test_super, kernfs_set_super, flags, |
248 | &init_user_ns, info); | |
fa736a95 TH |
249 | if (IS_ERR(sb) || sb->s_fs_info != info) |
250 | kfree(info); | |
251 | if (IS_ERR(sb)) | |
252 | return ERR_CAST(sb); | |
fed95bab LZ |
253 | |
254 | if (new_sb_created) | |
255 | *new_sb_created = !sb->s_root; | |
256 | ||
fa736a95 | 257 | if (!sb->s_root) { |
7d568a83 TH |
258 | struct kernfs_super_info *info = kernfs_info(sb); |
259 | ||
26fc9cd2 | 260 | error = kernfs_fill_super(sb, magic); |
fa736a95 TH |
261 | if (error) { |
262 | deactivate_locked_super(sb); | |
263 | return ERR_PTR(error); | |
264 | } | |
265 | sb->s_flags |= MS_ACTIVE; | |
7d568a83 TH |
266 | |
267 | mutex_lock(&kernfs_mutex); | |
268 | list_add(&info->node, &root->supers); | |
269 | mutex_unlock(&kernfs_mutex); | |
fa736a95 TH |
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 | */ | |
283 | void kernfs_kill_sb(struct super_block *sb) | |
284 | { | |
c525aadd | 285 | struct kernfs_super_info *info = kernfs_info(sb); |
324a56e1 | 286 | struct kernfs_node *root_kn = sb->s_root->d_fsdata; |
fa736a95 | 287 | |
7d568a83 TH |
288 | mutex_lock(&kernfs_mutex); |
289 | list_del(&info->node); | |
290 | mutex_unlock(&kernfs_mutex); | |
291 | ||
fa736a95 TH |
292 | /* |
293 | * Remove the superblock from fs_supers/s_instances | |
c525aadd | 294 | * so we can't find it, before freeing kernfs_super_info. |
fa736a95 TH |
295 | */ |
296 | kill_anon_super(sb); | |
297 | kfree(info); | |
324a56e1 | 298 | kernfs_put(root_kn); |
fa736a95 TH |
299 | } |
300 | ||
4e26445f LZ |
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 | */ | |
313 | struct 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 | ||
fa736a95 TH |
331 | void __init kernfs_init(void) |
332 | { | |
a797bfc3 | 333 | kernfs_node_cache = kmem_cache_create("kernfs_node_cache", |
324a56e1 | 334 | sizeof(struct kernfs_node), |
fa736a95 | 335 | 0, SLAB_PANIC, NULL); |
fa736a95 | 336 | } |