2 * fs/kernfs/mount.c - kernfs mount implementation
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>
8 * This file is released under the GPLv2.
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>
21 #include "kernfs-internal.h"
23 struct kmem_cache *kernfs_node_cache, *kernfs_iattrs_cache;
25 static int kernfs_sop_show_options(struct seq_file *sf, struct dentry *dentry)
27 struct kernfs_root *root = kernfs_root(kernfs_dentry_node(dentry));
28 struct kernfs_syscall_ops *scops = root->syscall_ops;
30 if (scops && scops->show_options)
31 return scops->show_options(sf, root);
35 static int kernfs_sop_show_path(struct seq_file *sf, struct dentry *dentry)
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;
41 if (scops && scops->show_path)
42 return scops->show_path(sf, node, root);
44 seq_dentry(sf, dentry, " \t\n\\");
48 const struct super_operations kernfs_sops = {
49 .statfs = simple_statfs,
50 .drop_inode = generic_delete_inode,
51 .evict_inode = kernfs_evict_inode,
53 .show_options = kernfs_sop_show_options,
54 .show_path = kernfs_sop_show_path,
58 * Similar to kernfs_fh_get_inode, this one gets kernfs node from inode
59 * number and generation
61 struct kernfs_node *kernfs_get_node_by_id(struct kernfs_root *root,
62 const union kernfs_node_id *id)
64 struct kernfs_node *kn;
66 kn = kernfs_find_and_get_node_by_ino(root, id->ino);
69 if (kn->id.generation != id->generation) {
76 static struct inode *kernfs_fh_get_inode(struct super_block *sb,
77 u64 ino, u32 generation)
79 struct kernfs_super_info *info = kernfs_info(sb);
81 struct kernfs_node *kn;
84 return ERR_PTR(-ESTALE);
86 kn = kernfs_find_and_get_node_by_ino(info->root, ino);
88 return ERR_PTR(-ESTALE);
89 inode = kernfs_get_inode(sb, kn);
92 return ERR_PTR(-ESTALE);
94 if (generation && inode->i_generation != generation) {
95 /* we didn't find the right inode.. */
97 return ERR_PTR(-ESTALE);
102 static struct dentry *kernfs_fh_to_dentry(struct super_block *sb, struct fid *fid,
103 int fh_len, int fh_type)
105 return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
106 kernfs_fh_get_inode);
109 static struct dentry *kernfs_fh_to_parent(struct super_block *sb, struct fid *fid,
110 int fh_len, int fh_type)
112 return generic_fh_to_parent(sb, fid, fh_len, fh_type,
113 kernfs_fh_get_inode);
116 static struct dentry *kernfs_get_parent_dentry(struct dentry *child)
118 struct kernfs_node *kn = kernfs_dentry_node(child);
120 return d_obtain_alias(kernfs_get_inode(child->d_sb, kn->parent));
123 static const struct export_operations kernfs_export_ops = {
124 .fh_to_dentry = kernfs_fh_to_dentry,
125 .fh_to_parent = kernfs_fh_to_parent,
126 .get_parent = kernfs_get_parent_dentry,
130 * kernfs_root_from_sb - determine kernfs_root associated with a super_block
131 * @sb: the super_block in question
133 * Return the kernfs_root associated with @sb. If @sb is not a kernfs one,
136 struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
138 if (sb->s_op == &kernfs_sops)
139 return kernfs_info(sb)->root;
144 * find the next ancestor in the path down to @child, where @parent was the
145 * ancestor whose descendant we want to find.
147 * Say the path is /a/b/c/d. @child is d, @parent is NULL. We return the root
148 * node. If @parent is b, then we return the node for c.
149 * Passing in d as @parent is not ok.
151 static struct kernfs_node *find_next_ancestor(struct kernfs_node *child,
152 struct kernfs_node *parent)
154 if (child == parent) {
155 pr_crit_once("BUG in find_next_ancestor: called with parent == child");
159 while (child->parent != parent) {
162 child = child->parent;
169 * kernfs_node_dentry - get a dentry for the given kernfs_node
170 * @kn: kernfs_node for which a dentry is needed
171 * @sb: the kernfs super_block
173 struct dentry *kernfs_node_dentry(struct kernfs_node *kn,
174 struct super_block *sb)
176 struct dentry *dentry;
177 struct kernfs_node *knparent = NULL;
179 BUG_ON(sb->s_op != &kernfs_sops);
181 dentry = dget(sb->s_root);
183 /* Check if this is the root kernfs_node */
187 knparent = find_next_ancestor(kn, NULL);
188 if (WARN_ON(!knparent)) {
190 return ERR_PTR(-EINVAL);
195 struct kernfs_node *kntmp;
199 kntmp = find_next_ancestor(kn, knparent);
200 if (WARN_ON(!kntmp)) {
202 return ERR_PTR(-EINVAL);
204 dtmp = lookup_one_len_unlocked(kntmp->name, dentry,
205 strlen(kntmp->name));
214 static int kernfs_fill_super(struct super_block *sb, struct kernfs_fs_context *kfc)
216 struct kernfs_super_info *info = kernfs_info(sb);
221 /* Userspace would break if executables or devices appear on sysfs */
222 sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;
223 sb->s_blocksize = PAGE_SIZE;
224 sb->s_blocksize_bits = PAGE_SHIFT;
225 sb->s_magic = kfc->magic;
226 sb->s_op = &kernfs_sops;
227 sb->s_xattr = kernfs_xattr_handlers;
228 if (info->root->flags & KERNFS_ROOT_SUPPORT_EXPORTOP)
229 sb->s_export_op = &kernfs_export_ops;
232 /* sysfs dentries and inodes don't require IO to create */
233 sb->s_shrink.seeks = 0;
235 /* get root inode, initialize and unlock it */
236 mutex_lock(&kernfs_mutex);
237 inode = kernfs_get_inode(sb, info->root->kn);
238 mutex_unlock(&kernfs_mutex);
240 pr_debug("kernfs: could not get root inode\n");
244 /* instantiate and link root dentry */
245 root = d_make_root(inode);
247 pr_debug("%s: could not get root dentry!\n", __func__);
251 sb->s_d_op = &kernfs_dops;
255 static int kernfs_test_super(struct super_block *sb, struct fs_context *fc)
257 struct kernfs_super_info *sb_info = kernfs_info(sb);
258 struct kernfs_super_info *info = fc->s_fs_info;
260 return sb_info->root == info->root && sb_info->ns == info->ns;
263 static int kernfs_set_super(struct super_block *sb, struct fs_context *fc)
265 struct kernfs_fs_context *kfc = fc->fs_private;
268 return set_anon_super_fc(sb, fc);
272 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
273 * @sb: super_block of interest
275 * Return the namespace tag associated with kernfs super_block @sb.
277 const void *kernfs_super_ns(struct super_block *sb)
279 struct kernfs_super_info *info = kernfs_info(sb);
285 * kernfs_get_tree - kernfs filesystem access/retrieval helper
286 * @fc: The filesystem context.
288 * This is to be called from each kernfs user's fs_context->ops->get_tree()
289 * implementation, which should set the specified ->@fs_type and ->@flags, and
290 * specify the hierarchy and namespace tag to mount via ->@root and ->@ns,
293 int kernfs_get_tree(struct fs_context *fc)
295 struct kernfs_fs_context *kfc = fc->fs_private;
296 struct super_block *sb;
297 struct kernfs_super_info *info;
300 info = kzalloc(sizeof(*info), GFP_KERNEL);
304 info->root = kfc->root;
305 info->ns = kfc->ns_tag;
306 INIT_LIST_HEAD(&info->node);
308 fc->s_fs_info = info;
309 sb = sget_fc(fc, kernfs_test_super, kernfs_set_super);
314 struct kernfs_super_info *info = kernfs_info(sb);
316 kfc->new_sb_created = true;
318 error = kernfs_fill_super(sb, kfc);
320 deactivate_locked_super(sb);
323 sb->s_flags |= SB_ACTIVE;
325 mutex_lock(&kernfs_mutex);
326 list_add(&info->node, &info->root->supers);
327 mutex_unlock(&kernfs_mutex);
330 fc->root = dget(sb->s_root);
334 void kernfs_free_fs_context(struct fs_context *fc)
336 /* Note that we don't deal with kfc->ns_tag here. */
337 kfree(fc->s_fs_info);
338 fc->s_fs_info = NULL;
342 * kernfs_kill_sb - kill_sb for kernfs
343 * @sb: super_block being killed
345 * This can be used directly for file_system_type->kill_sb(). If a kernfs
346 * user needs extra cleanup, it can implement its own kill_sb() and call
347 * this function at the end.
349 void kernfs_kill_sb(struct super_block *sb)
351 struct kernfs_super_info *info = kernfs_info(sb);
353 mutex_lock(&kernfs_mutex);
354 list_del(&info->node);
355 mutex_unlock(&kernfs_mutex);
358 * Remove the superblock from fs_supers/s_instances
359 * so we can't find it, before freeing kernfs_super_info.
365 void __init kernfs_init(void)
369 * the slab is freed in RCU context, so kernfs_find_and_get_node_by_ino
370 * can access the slab lock free. This could introduce stale nodes,
371 * please see how kernfs_find_and_get_node_by_ino filters out stale
374 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
375 sizeof(struct kernfs_node),
377 SLAB_PANIC | SLAB_TYPESAFE_BY_RCU,
380 /* Creates slab cache for kernfs inode attributes */
381 kernfs_iattrs_cache = kmem_cache_create("kernfs_iattrs_cache",
382 sizeof(struct kernfs_iattrs),
383 0, SLAB_PANIC, NULL);