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Tejun Heob8441ed2013-11-24 09:54:58 -05001/*
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 */
Tejun Heofa736a92013-11-28 14:54:44 -050010
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
Tejun Heoa797bfc2013-12-11 14:11:57 -050020struct kmem_cache *kernfs_node_cache;
Tejun Heofa736a92013-11-28 14:54:44 -050021
Tejun Heo6a7fed42014-02-03 14:09:10 -050022static 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
Li Zefanf41c5932014-02-14 16:57:27 +080042const struct super_operations kernfs_sops = {
Tejun Heofa736a92013-11-28 14:54:44 -050043 .statfs = simple_statfs,
44 .drop_inode = generic_delete_inode,
Tejun Heoc637b8a2013-12-11 14:11:58 -050045 .evict_inode = kernfs_evict_inode,
Tejun Heo6a7fed42014-02-03 14:09:10 -050046
47 .remount_fs = kernfs_sop_remount_fs,
48 .show_options = kernfs_sop_show_options,
Tejun Heofa736a92013-11-28 14:54:44 -050049};
50
Tejun Heo0c23b222014-02-03 14:09:15 -050051/**
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
Jianyu Zhan26fc9cd2014-04-26 15:40:28 +080065static int kernfs_fill_super(struct super_block *sb, unsigned long magic)
Tejun Heofa736a92013-11-28 14:54:44 -050066{
Tejun Heoc525aad2013-12-11 14:11:55 -050067 struct kernfs_super_info *info = kernfs_info(sb);
Tejun Heofa736a92013-11-28 14:54:44 -050068 struct inode *inode;
69 struct dentry *root;
70
Tejun Heo7d568a82014-04-09 11:07:30 -040071 info->sb = sb;
Tejun Heofa736a92013-11-28 14:54:44 -050072 sb->s_blocksize = PAGE_CACHE_SIZE;
73 sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
Jianyu Zhan26fc9cd2014-04-26 15:40:28 +080074 sb->s_magic = magic;
Tejun Heoa797bfc2013-12-11 14:11:57 -050075 sb->s_op = &kernfs_sops;
Tejun Heofa736a92013-11-28 14:54:44 -050076 sb->s_time_gran = 1;
77
78 /* get root inode, initialize and unlock it */
Tejun Heoa797bfc2013-12-11 14:11:57 -050079 mutex_lock(&kernfs_mutex);
Tejun Heoc637b8a2013-12-11 14:11:58 -050080 inode = kernfs_get_inode(sb, info->root->kn);
Tejun Heoa797bfc2013-12-11 14:11:57 -050081 mutex_unlock(&kernfs_mutex);
Tejun Heofa736a92013-11-28 14:54:44 -050082 if (!inode) {
Tejun Heoc637b8a2013-12-11 14:11:58 -050083 pr_debug("kernfs: could not get root inode\n");
Tejun Heofa736a92013-11-28 14:54:44 -050084 return -ENOMEM;
85 }
86
87 /* instantiate and link root dentry */
88 root = d_make_root(inode);
89 if (!root) {
90 pr_debug("%s: could not get root dentry!\n", __func__);
91 return -ENOMEM;
92 }
Tejun Heo324a56e2013-12-11 14:11:53 -050093 kernfs_get(info->root->kn);
94 root->d_fsdata = info->root->kn;
Tejun Heofa736a92013-11-28 14:54:44 -050095 sb->s_root = root;
Tejun Heoa797bfc2013-12-11 14:11:57 -050096 sb->s_d_op = &kernfs_dops;
Tejun Heofa736a92013-11-28 14:54:44 -050097 return 0;
98}
99
Tejun Heoc637b8a2013-12-11 14:11:58 -0500100static int kernfs_test_super(struct super_block *sb, void *data)
Tejun Heofa736a92013-11-28 14:54:44 -0500101{
Tejun Heoc525aad2013-12-11 14:11:55 -0500102 struct kernfs_super_info *sb_info = kernfs_info(sb);
103 struct kernfs_super_info *info = data;
Tejun Heofa736a92013-11-28 14:54:44 -0500104
105 return sb_info->root == info->root && sb_info->ns == info->ns;
106}
107
Tejun Heoc637b8a2013-12-11 14:11:58 -0500108static int kernfs_set_super(struct super_block *sb, void *data)
Tejun Heofa736a92013-11-28 14:54:44 -0500109{
110 int error;
111 error = set_anon_super(sb, data);
112 if (!error)
113 sb->s_fs_info = data;
114 return error;
115}
116
117/**
118 * kernfs_super_ns - determine the namespace tag of a kernfs super_block
119 * @sb: super_block of interest
120 *
121 * Return the namespace tag associated with kernfs super_block @sb.
122 */
123const void *kernfs_super_ns(struct super_block *sb)
124{
Tejun Heoc525aad2013-12-11 14:11:55 -0500125 struct kernfs_super_info *info = kernfs_info(sb);
Tejun Heofa736a92013-11-28 14:54:44 -0500126
127 return info->ns;
128}
129
130/**
131 * kernfs_mount_ns - kernfs mount helper
132 * @fs_type: file_system_type of the fs being mounted
133 * @flags: mount flags specified for the mount
134 * @root: kernfs_root of the hierarchy being mounted
Jianyu Zhan26fc9cd2014-04-26 15:40:28 +0800135 * @magic: file system specific magic number
Li Zefanfed95ba2014-02-25 19:28:44 +0800136 * @new_sb_created: tell the caller if we allocated a new superblock
Tejun Heofa736a92013-11-28 14:54:44 -0500137 * @ns: optional namespace tag of the mount
138 *
139 * This is to be called from each kernfs user's file_system_type->mount()
140 * implementation, which should pass through the specified @fs_type and
141 * @flags, and specify the hierarchy and namespace tag to mount via @root
142 * and @ns, respectively.
143 *
144 * The return value can be passed to the vfs layer verbatim.
145 */
146struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
Jianyu Zhan26fc9cd2014-04-26 15:40:28 +0800147 struct kernfs_root *root, unsigned long magic,
148 bool *new_sb_created, const void *ns)
Tejun Heofa736a92013-11-28 14:54:44 -0500149{
150 struct super_block *sb;
Tejun Heoc525aad2013-12-11 14:11:55 -0500151 struct kernfs_super_info *info;
Tejun Heofa736a92013-11-28 14:54:44 -0500152 int error;
153
154 info = kzalloc(sizeof(*info), GFP_KERNEL);
155 if (!info)
156 return ERR_PTR(-ENOMEM);
157
158 info->root = root;
159 info->ns = ns;
160
Tejun Heoc637b8a2013-12-11 14:11:58 -0500161 sb = sget(fs_type, kernfs_test_super, kernfs_set_super, flags, info);
Tejun Heofa736a92013-11-28 14:54:44 -0500162 if (IS_ERR(sb) || sb->s_fs_info != info)
163 kfree(info);
164 if (IS_ERR(sb))
165 return ERR_CAST(sb);
Li Zefanfed95ba2014-02-25 19:28:44 +0800166
167 if (new_sb_created)
168 *new_sb_created = !sb->s_root;
169
Tejun Heofa736a92013-11-28 14:54:44 -0500170 if (!sb->s_root) {
Tejun Heo7d568a82014-04-09 11:07:30 -0400171 struct kernfs_super_info *info = kernfs_info(sb);
172
Jianyu Zhan26fc9cd2014-04-26 15:40:28 +0800173 error = kernfs_fill_super(sb, magic);
Tejun Heofa736a92013-11-28 14:54:44 -0500174 if (error) {
175 deactivate_locked_super(sb);
176 return ERR_PTR(error);
177 }
178 sb->s_flags |= MS_ACTIVE;
Tejun Heo7d568a82014-04-09 11:07:30 -0400179
180 mutex_lock(&kernfs_mutex);
181 list_add(&info->node, &root->supers);
182 mutex_unlock(&kernfs_mutex);
Tejun Heofa736a92013-11-28 14:54:44 -0500183 }
184
185 return dget(sb->s_root);
186}
187
188/**
189 * kernfs_kill_sb - kill_sb for kernfs
190 * @sb: super_block being killed
191 *
192 * This can be used directly for file_system_type->kill_sb(). If a kernfs
193 * user needs extra cleanup, it can implement its own kill_sb() and call
194 * this function at the end.
195 */
196void kernfs_kill_sb(struct super_block *sb)
197{
Tejun Heoc525aad2013-12-11 14:11:55 -0500198 struct kernfs_super_info *info = kernfs_info(sb);
Tejun Heo324a56e2013-12-11 14:11:53 -0500199 struct kernfs_node *root_kn = sb->s_root->d_fsdata;
Tejun Heofa736a92013-11-28 14:54:44 -0500200
Tejun Heo7d568a82014-04-09 11:07:30 -0400201 mutex_lock(&kernfs_mutex);
202 list_del(&info->node);
203 mutex_unlock(&kernfs_mutex);
204
Tejun Heofa736a92013-11-28 14:54:44 -0500205 /*
206 * Remove the superblock from fs_supers/s_instances
Tejun Heoc525aad2013-12-11 14:11:55 -0500207 * so we can't find it, before freeing kernfs_super_info.
Tejun Heofa736a92013-11-28 14:54:44 -0500208 */
209 kill_anon_super(sb);
210 kfree(info);
Tejun Heo324a56e2013-12-11 14:11:53 -0500211 kernfs_put(root_kn);
Tejun Heofa736a92013-11-28 14:54:44 -0500212}
213
Li Zefan4e264452014-06-30 11:50:28 +0800214/**
215 * kernfs_pin_sb: try to pin the superblock associated with a kernfs_root
216 * @kernfs_root: the kernfs_root in question
217 * @ns: the namespace tag
218 *
219 * Pin the superblock so the superblock won't be destroyed in subsequent
220 * operations. This can be used to block ->kill_sb() which may be useful
221 * for kernfs users which dynamically manage superblocks.
222 *
223 * Returns NULL if there's no superblock associated to this kernfs_root, or
224 * -EINVAL if the superblock is being freed.
225 */
226struct super_block *kernfs_pin_sb(struct kernfs_root *root, const void *ns)
227{
228 struct kernfs_super_info *info;
229 struct super_block *sb = NULL;
230
231 mutex_lock(&kernfs_mutex);
232 list_for_each_entry(info, &root->supers, node) {
233 if (info->ns == ns) {
234 sb = info->sb;
235 if (!atomic_inc_not_zero(&info->sb->s_active))
236 sb = ERR_PTR(-EINVAL);
237 break;
238 }
239 }
240 mutex_unlock(&kernfs_mutex);
241 return sb;
242}
243
Tejun Heofa736a92013-11-28 14:54:44 -0500244void __init kernfs_init(void)
245{
Tejun Heoa797bfc2013-12-11 14:11:57 -0500246 kernfs_node_cache = kmem_cache_create("kernfs_node_cache",
Tejun Heo324a56e2013-12-11 14:11:53 -0500247 sizeof(struct kernfs_node),
Tejun Heofa736a92013-11-28 14:54:44 -0500248 0, SLAB_PANIC, NULL);
Tejun Heoc637b8a2013-12-11 14:11:58 -0500249 kernfs_inode_init();
Tejun Heofa736a92013-11-28 14:54:44 -0500250}