xref: /openbmc/linux/fs/ramfs/inode.c (revision 87c2ce3b)
1 /*
2  * Resizable simple ram filesystem for Linux.
3  *
4  * Copyright (C) 2000 Linus Torvalds.
5  *               2000 Transmeta Corp.
6  *
7  * Usage limits added by David Gibson, Linuxcare Australia.
8  * This file is released under the GPL.
9  */
10 
11 /*
12  * NOTE! This filesystem is probably most useful
13  * not as a real filesystem, but as an example of
14  * how virtual filesystems can be written.
15  *
16  * It doesn't get much simpler than this. Consider
17  * that this file implements the full semantics of
18  * a POSIX-compliant read-write filesystem.
19  *
20  * Note in particular how the filesystem does not
21  * need to implement any data structures of its own
22  * to keep track of the virtual data: using the VFS
23  * caches is sufficient.
24  */
25 
26 #include <linux/module.h>
27 #include <linux/fs.h>
28 #include <linux/pagemap.h>
29 #include <linux/highmem.h>
30 #include <linux/init.h>
31 #include <linux/string.h>
32 #include <linux/smp_lock.h>
33 #include <linux/backing-dev.h>
34 #include <linux/ramfs.h>
35 
36 #include <asm/uaccess.h>
37 #include "internal.h"
38 
39 /* some random number */
40 #define RAMFS_MAGIC	0x858458f6
41 
42 static struct super_operations ramfs_ops;
43 static struct inode_operations ramfs_dir_inode_operations;
44 
45 static struct backing_dev_info ramfs_backing_dev_info = {
46 	.ra_pages	= 0,	/* No readahead */
47 	.capabilities	= BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
48 			  BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
49 			  BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
50 };
51 
52 struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
53 {
54 	struct inode * inode = new_inode(sb);
55 
56 	if (inode) {
57 		inode->i_mode = mode;
58 		inode->i_uid = current->fsuid;
59 		inode->i_gid = current->fsgid;
60 		inode->i_blksize = PAGE_CACHE_SIZE;
61 		inode->i_blocks = 0;
62 		inode->i_mapping->a_ops = &ramfs_aops;
63 		inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
64 		inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
65 		switch (mode & S_IFMT) {
66 		default:
67 			init_special_inode(inode, mode, dev);
68 			break;
69 		case S_IFREG:
70 			inode->i_op = &ramfs_file_inode_operations;
71 			inode->i_fop = &ramfs_file_operations;
72 			break;
73 		case S_IFDIR:
74 			inode->i_op = &ramfs_dir_inode_operations;
75 			inode->i_fop = &simple_dir_operations;
76 
77 			/* directory inodes start off with i_nlink == 2 (for "." entry) */
78 			inode->i_nlink++;
79 			break;
80 		case S_IFLNK:
81 			inode->i_op = &page_symlink_inode_operations;
82 			break;
83 		}
84 	}
85 	return inode;
86 }
87 
88 /*
89  * File creation. Allocate an inode, and we're done..
90  */
91 /* SMP-safe */
92 static int
93 ramfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
94 {
95 	struct inode * inode = ramfs_get_inode(dir->i_sb, mode, dev);
96 	int error = -ENOSPC;
97 
98 	if (inode) {
99 		if (dir->i_mode & S_ISGID) {
100 			inode->i_gid = dir->i_gid;
101 			if (S_ISDIR(mode))
102 				inode->i_mode |= S_ISGID;
103 		}
104 		d_instantiate(dentry, inode);
105 		dget(dentry);	/* Extra count - pin the dentry in core */
106 		error = 0;
107 	}
108 	return error;
109 }
110 
111 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, int mode)
112 {
113 	int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
114 	if (!retval)
115 		dir->i_nlink++;
116 	return retval;
117 }
118 
119 static int ramfs_create(struct inode *dir, struct dentry *dentry, int mode, struct nameidata *nd)
120 {
121 	return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
122 }
123 
124 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
125 {
126 	struct inode *inode;
127 	int error = -ENOSPC;
128 
129 	inode = ramfs_get_inode(dir->i_sb, S_IFLNK|S_IRWXUGO, 0);
130 	if (inode) {
131 		int l = strlen(symname)+1;
132 		error = page_symlink(inode, symname, l);
133 		if (!error) {
134 			if (dir->i_mode & S_ISGID)
135 				inode->i_gid = dir->i_gid;
136 			d_instantiate(dentry, inode);
137 			dget(dentry);
138 		} else
139 			iput(inode);
140 	}
141 	return error;
142 }
143 
144 static struct inode_operations ramfs_dir_inode_operations = {
145 	.create		= ramfs_create,
146 	.lookup		= simple_lookup,
147 	.link		= simple_link,
148 	.unlink		= simple_unlink,
149 	.symlink	= ramfs_symlink,
150 	.mkdir		= ramfs_mkdir,
151 	.rmdir		= simple_rmdir,
152 	.mknod		= ramfs_mknod,
153 	.rename		= simple_rename,
154 };
155 
156 static struct super_operations ramfs_ops = {
157 	.statfs		= simple_statfs,
158 	.drop_inode	= generic_delete_inode,
159 };
160 
161 static int ramfs_fill_super(struct super_block * sb, void * data, int silent)
162 {
163 	struct inode * inode;
164 	struct dentry * root;
165 
166 	sb->s_maxbytes = MAX_LFS_FILESIZE;
167 	sb->s_blocksize = PAGE_CACHE_SIZE;
168 	sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
169 	sb->s_magic = RAMFS_MAGIC;
170 	sb->s_op = &ramfs_ops;
171 	sb->s_time_gran = 1;
172 	inode = ramfs_get_inode(sb, S_IFDIR | 0755, 0);
173 	if (!inode)
174 		return -ENOMEM;
175 
176 	root = d_alloc_root(inode);
177 	if (!root) {
178 		iput(inode);
179 		return -ENOMEM;
180 	}
181 	sb->s_root = root;
182 	return 0;
183 }
184 
185 struct super_block *ramfs_get_sb(struct file_system_type *fs_type,
186 	int flags, const char *dev_name, void *data)
187 {
188 	return get_sb_nodev(fs_type, flags, data, ramfs_fill_super);
189 }
190 
191 static struct super_block *rootfs_get_sb(struct file_system_type *fs_type,
192 	int flags, const char *dev_name, void *data)
193 {
194 	return get_sb_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
195 }
196 
197 static struct file_system_type ramfs_fs_type = {
198 	.name		= "ramfs",
199 	.get_sb		= ramfs_get_sb,
200 	.kill_sb	= kill_litter_super,
201 };
202 static struct file_system_type rootfs_fs_type = {
203 	.name		= "rootfs",
204 	.get_sb		= rootfs_get_sb,
205 	.kill_sb	= kill_litter_super,
206 };
207 
208 static int __init init_ramfs_fs(void)
209 {
210 	return register_filesystem(&ramfs_fs_type);
211 }
212 
213 static void __exit exit_ramfs_fs(void)
214 {
215 	unregister_filesystem(&ramfs_fs_type);
216 }
217 
218 module_init(init_ramfs_fs)
219 module_exit(exit_ramfs_fs)
220 
221 int __init init_rootfs(void)
222 {
223 	return register_filesystem(&rootfs_fs_type);
224 }
225 
226 MODULE_LICENSE("GPL");
227