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Linux/fs/configfs/mount.c

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

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