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Linux/fs/configfs/mount.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /* -*- mode: c; c-basic-offset: 8; -*-
  3  * vim: noexpandtab sw=8 ts=8 sts=0:
  4  *
  5  * mount.c - operations for initializing and mounting configfs.
  6  *
  7  * Based on sysfs:
  8  *      sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
  9  *
 10  * configfs Copyright (C) 2005 Oracle.  All rights reserved.
 11  */
 12 
 13 #include <linux/fs.h>
 14 #include <linux/module.h>
 15 #include <linux/mount.h>
 16 #include <linux/fs_context.h>
 17 #include <linux/pagemap.h>
 18 #include <linux/init.h>
 19 #include <linux/slab.h>
 20 
 21 #include <linux/configfs.h>
 22 #include "configfs_internal.h"
 23 
 24 /* Random magic number */
 25 #define CONFIGFS_MAGIC 0x62656570
 26 
 27 static struct vfsmount *configfs_mount = NULL;
 28 struct kmem_cache *configfs_dir_cachep;
 29 static int configfs_mnt_count = 0;
 30 
 31 
 32 static void configfs_free_inode(struct inode *inode)
 33 {
 34         if (S_ISLNK(inode->i_mode))
 35                 kfree(inode->i_link);
 36         free_inode_nonrcu(inode);
 37 }
 38 
 39 static const struct super_operations configfs_ops = {
 40         .statfs         = simple_statfs,
 41         .drop_inode     = generic_delete_inode,
 42         .free_inode     = configfs_free_inode,
 43 };
 44 
 45 static struct config_group configfs_root_group = {
 46         .cg_item = {
 47                 .ci_namebuf     = "root",
 48                 .ci_name        = configfs_root_group.cg_item.ci_namebuf,
 49         },
 50 };
 51 
 52 int configfs_is_root(struct config_item *item)
 53 {
 54         return item == &configfs_root_group.cg_item;
 55 }
 56 
 57 static struct configfs_dirent configfs_root = {
 58         .s_sibling      = LIST_HEAD_INIT(configfs_root.s_sibling),
 59         .s_children     = LIST_HEAD_INIT(configfs_root.s_children),
 60         .s_element      = &configfs_root_group.cg_item,
 61         .s_type         = CONFIGFS_ROOT,
 62         .s_iattr        = NULL,
 63 };
 64 
 65 static int configfs_fill_super(struct super_block *sb, struct fs_context *fc)
 66 {
 67         struct inode *inode;
 68         struct dentry *root;
 69 
 70         sb->s_blocksize = PAGE_SIZE;
 71         sb->s_blocksize_bits = PAGE_SHIFT;
 72         sb->s_magic = CONFIGFS_MAGIC;
 73         sb->s_op = &configfs_ops;
 74         sb->s_time_gran = 1;
 75 
 76         inode = configfs_new_inode(S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
 77                                    &configfs_root, sb);
 78         if (inode) {
 79                 inode->i_op = &configfs_root_inode_operations;
 80                 inode->i_fop = &configfs_dir_operations;
 81                 /* directory inodes start off with i_nlink == 2 (for "." entry) */
 82                 inc_nlink(inode);
 83         } else {
 84                 pr_debug("could not get root inode\n");
 85                 return -ENOMEM;
 86         }
 87 
 88         root = d_make_root(inode);
 89         if (!root) {
 90                 pr_debug("%s: could not get root dentry!\n",__func__);
 91                 return -ENOMEM;
 92         }
 93         config_group_init(&configfs_root_group);
 94         configfs_root_group.cg_item.ci_dentry = root;
 95         root->d_fsdata = &configfs_root;
 96         sb->s_root = root;
 97         sb->s_d_op = &configfs_dentry_ops; /* the rest get that */
 98         return 0;
 99 }
100 
101 static int configfs_get_tree(struct fs_context *fc)
102 {
103         return get_tree_single(fc, configfs_fill_super);
104 }
105 
106 static const struct fs_context_operations configfs_context_ops = {
107         .get_tree       = configfs_get_tree,
108 };
109 
110 static int configfs_init_fs_context(struct fs_context *fc)
111 {
112         fc->ops = &configfs_context_ops;
113         return 0;
114 }
115 
116 static struct file_system_type configfs_fs_type = {
117         .owner          = THIS_MODULE,
118         .name           = "configfs",
119         .init_fs_context = configfs_init_fs_context,
120         .kill_sb        = kill_litter_super,
121 };
122 MODULE_ALIAS_FS("configfs");
123 
124 struct dentry *configfs_pin_fs(void)
125 {
126         int err = simple_pin_fs(&configfs_fs_type, &configfs_mount,
127                              &configfs_mnt_count);
128         return err ? ERR_PTR(err) : configfs_mount->mnt_root;
129 }
130 
131 void configfs_release_fs(void)
132 {
133         simple_release_fs(&configfs_mount, &configfs_mnt_count);
134 }
135 
136 
137 static int __init configfs_init(void)
138 {
139         int err = -ENOMEM;
140 
141         configfs_dir_cachep = kmem_cache_create("configfs_dir_cache",
142                                                 sizeof(struct configfs_dirent),
143                                                 0, 0, NULL);
144         if (!configfs_dir_cachep)
145                 goto out;
146 
147         err = sysfs_create_mount_point(kernel_kobj, "config");
148         if (err)
149                 goto out2;
150 
151         err = register_filesystem(&configfs_fs_type);
152         if (err)
153                 goto out3;
154 
155         return 0;
156 out3:
157         pr_err("Unable to register filesystem!\n");
158         sysfs_remove_mount_point(kernel_kobj, "config");
159 out2:
160         kmem_cache_destroy(configfs_dir_cachep);
161         configfs_dir_cachep = NULL;
162 out:
163         return err;
164 }
165 
166 static void __exit configfs_exit(void)
167 {
168         unregister_filesystem(&configfs_fs_type);
169         sysfs_remove_mount_point(kernel_kobj, "config");
170         kmem_cache_destroy(configfs_dir_cachep);
171         configfs_dir_cachep = NULL;
172 }
173 
174 MODULE_AUTHOR("Oracle");
175 MODULE_LICENSE("GPL");
176 MODULE_VERSION("0.0.2");
177 MODULE_DESCRIPTION("Simple RAM filesystem for user driven kernel subsystem configuration.");
178 
179 core_initcall(configfs_init);
180 module_exit(configfs_exit);
181 

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