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TOMOYO Linux Cross Reference
Linux/fs/ramfs/inode.c

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  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/fs.h>
 27 #include <linux/pagemap.h>
 28 #include <linux/highmem.h>
 29 #include <linux/time.h>
 30 #include <linux/init.h>
 31 #include <linux/string.h>
 32 #include <linux/backing-dev.h>
 33 #include <linux/ramfs.h>
 34 #include <linux/sched.h>
 35 #include <linux/parser.h>
 36 #include <linux/magic.h>
 37 #include <linux/slab.h>
 38 #include <asm/uaccess.h>
 39 #include "internal.h"
 40 
 41 #define RAMFS_DEFAULT_MODE      0755
 42 
 43 static const struct super_operations ramfs_ops;
 44 static const struct inode_operations ramfs_dir_inode_operations;
 45 
 46 static struct backing_dev_info ramfs_backing_dev_info = {
 47         .name           = "ramfs",
 48         .ra_pages       = 0,    /* No readahead */
 49         .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK |
 50                           BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
 51                           BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
 52 };
 53 
 54 struct inode *ramfs_get_inode(struct super_block *sb,
 55                                 const struct inode *dir, umode_t mode, dev_t dev)
 56 {
 57         struct inode * inode = new_inode(sb);
 58 
 59         if (inode) {
 60                 inode->i_ino = get_next_ino();
 61                 inode_init_owner(inode, dir, mode);
 62                 inode->i_mapping->a_ops = &ramfs_aops;
 63                 inode->i_mapping->backing_dev_info = &ramfs_backing_dev_info;
 64                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
 65                 mapping_set_unevictable(inode->i_mapping);
 66                 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 67                 switch (mode & S_IFMT) {
 68                 default:
 69                         init_special_inode(inode, mode, dev);
 70                         break;
 71                 case S_IFREG:
 72                         inode->i_op = &ramfs_file_inode_operations;
 73                         inode->i_fop = &ramfs_file_operations;
 74                         break;
 75                 case S_IFDIR:
 76                         inode->i_op = &ramfs_dir_inode_operations;
 77                         inode->i_fop = &simple_dir_operations;
 78 
 79                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 80                         inc_nlink(inode);
 81                         break;
 82                 case S_IFLNK:
 83                         inode->i_op = &page_symlink_inode_operations;
 84                         break;
 85                 }
 86         }
 87         return inode;
 88 }
 89 
 90 /*
 91  * File creation. Allocate an inode, and we're done..
 92  */
 93 /* SMP-safe */
 94 static int
 95 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
 96 {
 97         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
 98         int error = -ENOSPC;
 99 
100         if (inode) {
101                 d_instantiate(dentry, inode);
102                 dget(dentry);   /* Extra count - pin the dentry in core */
103                 error = 0;
104                 dir->i_mtime = dir->i_ctime = CURRENT_TIME;
105         }
106         return error;
107 }
108 
109 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
110 {
111         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
112         if (!retval)
113                 inc_nlink(dir);
114         return retval;
115 }
116 
117 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
118 {
119         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
120 }
121 
122 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
123 {
124         struct inode *inode;
125         int error = -ENOSPC;
126 
127         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
128         if (inode) {
129                 int l = strlen(symname)+1;
130                 error = page_symlink(inode, symname, l);
131                 if (!error) {
132                         d_instantiate(dentry, inode);
133                         dget(dentry);
134                         dir->i_mtime = dir->i_ctime = CURRENT_TIME;
135                 } else
136                         iput(inode);
137         }
138         return error;
139 }
140 
141 static const struct inode_operations ramfs_dir_inode_operations = {
142         .create         = ramfs_create,
143         .lookup         = simple_lookup,
144         .link           = simple_link,
145         .unlink         = simple_unlink,
146         .symlink        = ramfs_symlink,
147         .mkdir          = ramfs_mkdir,
148         .rmdir          = simple_rmdir,
149         .mknod          = ramfs_mknod,
150         .rename         = simple_rename,
151 };
152 
153 static const struct super_operations ramfs_ops = {
154         .statfs         = simple_statfs,
155         .drop_inode     = generic_delete_inode,
156         .show_options   = generic_show_options,
157 };
158 
159 struct ramfs_mount_opts {
160         umode_t mode;
161 };
162 
163 enum {
164         Opt_mode,
165         Opt_err
166 };
167 
168 static const match_table_t tokens = {
169         {Opt_mode, "mode=%o"},
170         {Opt_err, NULL}
171 };
172 
173 struct ramfs_fs_info {
174         struct ramfs_mount_opts mount_opts;
175 };
176 
177 static int ramfs_parse_options(char *data, struct ramfs_mount_opts *opts)
178 {
179         substring_t args[MAX_OPT_ARGS];
180         int option;
181         int token;
182         char *p;
183 
184         opts->mode = RAMFS_DEFAULT_MODE;
185 
186         while ((p = strsep(&data, ",")) != NULL) {
187                 if (!*p)
188                         continue;
189 
190                 token = match_token(p, tokens, args);
191                 switch (token) {
192                 case Opt_mode:
193                         if (match_octal(&args[0], &option))
194                                 return -EINVAL;
195                         opts->mode = option & S_IALLUGO;
196                         break;
197                 /*
198                  * We might like to report bad mount options here;
199                  * but traditionally ramfs has ignored all mount options,
200                  * and as it is used as a !CONFIG_SHMEM simple substitute
201                  * for tmpfs, better continue to ignore other mount options.
202                  */
203                 }
204         }
205 
206         return 0;
207 }
208 
209 int ramfs_fill_super(struct super_block *sb, void *data, int silent)
210 {
211         struct ramfs_fs_info *fsi;
212         struct inode *inode;
213         int err;
214 
215         save_mount_options(sb, data);
216 
217         fsi = kzalloc(sizeof(struct ramfs_fs_info), GFP_KERNEL);
218         sb->s_fs_info = fsi;
219         if (!fsi)
220                 return -ENOMEM;
221 
222         err = ramfs_parse_options(data, &fsi->mount_opts);
223         if (err)
224                 return err;
225 
226         sb->s_maxbytes          = MAX_LFS_FILESIZE;
227         sb->s_blocksize         = PAGE_CACHE_SIZE;
228         sb->s_blocksize_bits    = PAGE_CACHE_SHIFT;
229         sb->s_magic             = RAMFS_MAGIC;
230         sb->s_op                = &ramfs_ops;
231         sb->s_time_gran         = 1;
232 
233         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
234         sb->s_root = d_make_root(inode);
235         if (!sb->s_root)
236                 return -ENOMEM;
237 
238         return 0;
239 }
240 
241 struct dentry *ramfs_mount(struct file_system_type *fs_type,
242         int flags, const char *dev_name, void *data)
243 {
244         return mount_nodev(fs_type, flags, data, ramfs_fill_super);
245 }
246 
247 static struct dentry *rootfs_mount(struct file_system_type *fs_type,
248         int flags, const char *dev_name, void *data)
249 {
250         return mount_nodev(fs_type, flags|MS_NOUSER, data, ramfs_fill_super);
251 }
252 
253 static void ramfs_kill_sb(struct super_block *sb)
254 {
255         kfree(sb->s_fs_info);
256         kill_litter_super(sb);
257 }
258 
259 static struct file_system_type ramfs_fs_type = {
260         .name           = "ramfs",
261         .mount          = ramfs_mount,
262         .kill_sb        = ramfs_kill_sb,
263         .fs_flags       = FS_USERNS_MOUNT,
264 };
265 static struct file_system_type rootfs_fs_type = {
266         .name           = "rootfs",
267         .mount          = rootfs_mount,
268         .kill_sb        = kill_litter_super,
269 };
270 
271 static int __init init_ramfs_fs(void)
272 {
273         return register_filesystem(&ramfs_fs_type);
274 }
275 module_init(init_ramfs_fs)
276 
277 int __init init_rootfs(void)
278 {
279         int err;
280 
281         err = bdi_init(&ramfs_backing_dev_info);
282         if (err)
283                 return err;
284 
285         err = register_filesystem(&rootfs_fs_type);
286         if (err)
287                 bdi_destroy(&ramfs_backing_dev_info);
288 
289         return err;
290 }
291 

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