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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 <linux/uaccess.h>
 39 #include <linux/fs_context.h>
 40 #include <linux/fs_parser.h>
 41 #include "internal.h"
 42 
 43 struct ramfs_mount_opts {
 44         umode_t mode;
 45 };
 46 
 47 struct ramfs_fs_info {
 48         struct ramfs_mount_opts mount_opts;
 49 };
 50 
 51 #define RAMFS_DEFAULT_MODE      0755
 52 
 53 static const struct super_operations ramfs_ops;
 54 static const struct inode_operations ramfs_dir_inode_operations;
 55 
 56 static const struct address_space_operations ramfs_aops = {
 57         .readpage       = simple_readpage,
 58         .write_begin    = simple_write_begin,
 59         .write_end      = simple_write_end,
 60         .set_page_dirty = __set_page_dirty_no_writeback,
 61 };
 62 
 63 struct inode *ramfs_get_inode(struct super_block *sb,
 64                                 const struct inode *dir, umode_t mode, dev_t dev)
 65 {
 66         struct inode * inode = new_inode(sb);
 67 
 68         if (inode) {
 69                 inode->i_ino = get_next_ino();
 70                 inode_init_owner(inode, dir, mode);
 71                 inode->i_mapping->a_ops = &ramfs_aops;
 72                 mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
 73                 mapping_set_unevictable(inode->i_mapping);
 74                 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
 75                 switch (mode & S_IFMT) {
 76                 default:
 77                         init_special_inode(inode, mode, dev);
 78                         break;
 79                 case S_IFREG:
 80                         inode->i_op = &ramfs_file_inode_operations;
 81                         inode->i_fop = &ramfs_file_operations;
 82                         break;
 83                 case S_IFDIR:
 84                         inode->i_op = &ramfs_dir_inode_operations;
 85                         inode->i_fop = &simple_dir_operations;
 86 
 87                         /* directory inodes start off with i_nlink == 2 (for "." entry) */
 88                         inc_nlink(inode);
 89                         break;
 90                 case S_IFLNK:
 91                         inode->i_op = &page_symlink_inode_operations;
 92                         inode_nohighmem(inode);
 93                         break;
 94                 }
 95         }
 96         return inode;
 97 }
 98 
 99 /*
100  * File creation. Allocate an inode, and we're done..
101  */
102 /* SMP-safe */
103 static int
104 ramfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
105 {
106         struct inode * inode = ramfs_get_inode(dir->i_sb, dir, mode, dev);
107         int error = -ENOSPC;
108 
109         if (inode) {
110                 d_instantiate(dentry, inode);
111                 dget(dentry);   /* Extra count - pin the dentry in core */
112                 error = 0;
113                 dir->i_mtime = dir->i_ctime = current_time(dir);
114         }
115         return error;
116 }
117 
118 static int ramfs_mkdir(struct inode * dir, struct dentry * dentry, umode_t mode)
119 {
120         int retval = ramfs_mknod(dir, dentry, mode | S_IFDIR, 0);
121         if (!retval)
122                 inc_nlink(dir);
123         return retval;
124 }
125 
126 static int ramfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, bool excl)
127 {
128         return ramfs_mknod(dir, dentry, mode | S_IFREG, 0);
129 }
130 
131 static int ramfs_symlink(struct inode * dir, struct dentry *dentry, const char * symname)
132 {
133         struct inode *inode;
134         int error = -ENOSPC;
135 
136         inode = ramfs_get_inode(dir->i_sb, dir, S_IFLNK|S_IRWXUGO, 0);
137         if (inode) {
138                 int l = strlen(symname)+1;
139                 error = page_symlink(inode, symname, l);
140                 if (!error) {
141                         d_instantiate(dentry, inode);
142                         dget(dentry);
143                         dir->i_mtime = dir->i_ctime = current_time(dir);
144                 } else
145                         iput(inode);
146         }
147         return error;
148 }
149 
150 static const struct inode_operations ramfs_dir_inode_operations = {
151         .create         = ramfs_create,
152         .lookup         = simple_lookup,
153         .link           = simple_link,
154         .unlink         = simple_unlink,
155         .symlink        = ramfs_symlink,
156         .mkdir          = ramfs_mkdir,
157         .rmdir          = simple_rmdir,
158         .mknod          = ramfs_mknod,
159         .rename         = simple_rename,
160 };
161 
162 /*
163  * Display the mount options in /proc/mounts.
164  */
165 static int ramfs_show_options(struct seq_file *m, struct dentry *root)
166 {
167         struct ramfs_fs_info *fsi = root->d_sb->s_fs_info;
168 
169         if (fsi->mount_opts.mode != RAMFS_DEFAULT_MODE)
170                 seq_printf(m, ",mode=%o", fsi->mount_opts.mode);
171         return 0;
172 }
173 
174 static const struct super_operations ramfs_ops = {
175         .statfs         = simple_statfs,
176         .drop_inode     = generic_delete_inode,
177         .show_options   = ramfs_show_options,
178 };
179 
180 enum ramfs_param {
181         Opt_mode,
182 };
183 
184 const struct fs_parameter_spec ramfs_fs_parameters[] = {
185         fsparam_u32oct("mode",  Opt_mode),
186         {}
187 };
188 
189 static int ramfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
190 {
191         struct fs_parse_result result;
192         struct ramfs_fs_info *fsi = fc->s_fs_info;
193         int opt;
194 
195         opt = fs_parse(fc, ramfs_fs_parameters, param, &result);
196         if (opt < 0) {
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                 if (opt == -ENOPARAM)
204                         opt = 0;
205                 return opt;
206         }
207 
208         switch (opt) {
209         case Opt_mode:
210                 fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
211                 break;
212         }
213 
214         return 0;
215 }
216 
217 static int ramfs_fill_super(struct super_block *sb, struct fs_context *fc)
218 {
219         struct ramfs_fs_info *fsi = sb->s_fs_info;
220         struct inode *inode;
221 
222         sb->s_maxbytes          = MAX_LFS_FILESIZE;
223         sb->s_blocksize         = PAGE_SIZE;
224         sb->s_blocksize_bits    = PAGE_SHIFT;
225         sb->s_magic             = RAMFS_MAGIC;
226         sb->s_op                = &ramfs_ops;
227         sb->s_time_gran         = 1;
228 
229         inode = ramfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
230         sb->s_root = d_make_root(inode);
231         if (!sb->s_root)
232                 return -ENOMEM;
233 
234         return 0;
235 }
236 
237 static int ramfs_get_tree(struct fs_context *fc)
238 {
239         return get_tree_nodev(fc, ramfs_fill_super);
240 }
241 
242 static void ramfs_free_fc(struct fs_context *fc)
243 {
244         kfree(fc->s_fs_info);
245 }
246 
247 static const struct fs_context_operations ramfs_context_ops = {
248         .free           = ramfs_free_fc,
249         .parse_param    = ramfs_parse_param,
250         .get_tree       = ramfs_get_tree,
251 };
252 
253 int ramfs_init_fs_context(struct fs_context *fc)
254 {
255         struct ramfs_fs_info *fsi;
256 
257         fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
258         if (!fsi)
259                 return -ENOMEM;
260 
261         fsi->mount_opts.mode = RAMFS_DEFAULT_MODE;
262         fc->s_fs_info = fsi;
263         fc->ops = &ramfs_context_ops;
264         return 0;
265 }
266 
267 static void ramfs_kill_sb(struct super_block *sb)
268 {
269         kfree(sb->s_fs_info);
270         kill_litter_super(sb);
271 }
272 
273 static struct file_system_type ramfs_fs_type = {
274         .name           = "ramfs",
275         .init_fs_context = ramfs_init_fs_context,
276         .parameters     = ramfs_fs_parameters,
277         .kill_sb        = ramfs_kill_sb,
278         .fs_flags       = FS_USERNS_MOUNT,
279 };
280 
281 static int __init init_ramfs_fs(void)
282 {
283         return register_filesystem(&ramfs_fs_type);
284 }
285 fs_initcall(init_ramfs_fs);
286 

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