inode.c 5.6 KB

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