tiny-shmem.c 3.2 KB

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  1. /*
  2. * tiny-shmem.c: simple shmemfs and tmpfs using ramfs code
  3. *
  4. * Matt Mackall <mpm@selenic.com> January, 2004
  5. * derived from mm/shmem.c and fs/ramfs/inode.c
  6. *
  7. * This is intended for small system where the benefits of the full
  8. * shmem code (swap-backed and resource-limited) are outweighed by
  9. * their complexity. On systems without swap this code should be
  10. * effectively equivalent, but much lighter weight.
  11. */
  12. #include <linux/fs.h>
  13. #include <linux/init.h>
  14. #include <linux/vfs.h>
  15. #include <linux/mount.h>
  16. #include <linux/file.h>
  17. #include <linux/mm.h>
  18. #include <linux/module.h>
  19. #include <linux/swap.h>
  20. #include <linux/ramfs.h>
  21. static struct file_system_type tmpfs_fs_type = {
  22. .name = "tmpfs",
  23. .get_sb = ramfs_get_sb,
  24. .kill_sb = kill_litter_super,
  25. };
  26. static struct vfsmount *shm_mnt;
  27. static int __init init_tmpfs(void)
  28. {
  29. BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
  30. shm_mnt = kern_mount(&tmpfs_fs_type);
  31. BUG_ON(IS_ERR(shm_mnt));
  32. return 0;
  33. }
  34. module_init(init_tmpfs)
  35. /*
  36. * shmem_file_setup - get an unlinked file living in tmpfs
  37. *
  38. * @name: name for dentry (to be seen in /proc/<pid>/maps
  39. * @size: size to be set for the file
  40. *
  41. */
  42. struct file *shmem_file_setup(char *name, loff_t size, unsigned long flags)
  43. {
  44. int error;
  45. struct file *file;
  46. struct inode *inode;
  47. struct dentry *dentry, *root;
  48. struct qstr this;
  49. if (IS_ERR(shm_mnt))
  50. return (void *)shm_mnt;
  51. error = -ENOMEM;
  52. this.name = name;
  53. this.len = strlen(name);
  54. this.hash = 0; /* will go */
  55. root = shm_mnt->mnt_root;
  56. dentry = d_alloc(root, &this);
  57. if (!dentry)
  58. goto put_memory;
  59. error = -ENFILE;
  60. file = get_empty_filp();
  61. if (!file)
  62. goto put_dentry;
  63. error = -ENOSPC;
  64. inode = ramfs_get_inode(root->d_sb, S_IFREG | S_IRWXUGO, 0);
  65. if (!inode)
  66. goto close_file;
  67. d_instantiate(dentry, inode);
  68. inode->i_nlink = 0; /* It is unlinked */
  69. file->f_path.mnt = mntget(shm_mnt);
  70. file->f_path.dentry = dentry;
  71. file->f_mapping = inode->i_mapping;
  72. file->f_op = &ramfs_file_operations;
  73. file->f_mode = FMODE_WRITE | FMODE_READ;
  74. /* notify everyone as to the change of file size */
  75. error = do_truncate(dentry, size, 0, file);
  76. if (error < 0)
  77. goto close_file;
  78. return file;
  79. close_file:
  80. put_filp(file);
  81. put_dentry:
  82. dput(dentry);
  83. put_memory:
  84. return ERR_PTR(error);
  85. }
  86. /*
  87. * shmem_zero_setup - setup a shared anonymous mapping
  88. *
  89. * @vma: the vma to be mmapped is prepared by do_mmap_pgoff
  90. */
  91. int shmem_zero_setup(struct vm_area_struct *vma)
  92. {
  93. struct file *file;
  94. loff_t size = vma->vm_end - vma->vm_start;
  95. file = shmem_file_setup("dev/zero", size, vma->vm_flags);
  96. if (IS_ERR(file))
  97. return PTR_ERR(file);
  98. if (vma->vm_file)
  99. fput(vma->vm_file);
  100. vma->vm_file = file;
  101. vma->vm_ops = &generic_file_vm_ops;
  102. return 0;
  103. }
  104. int shmem_unuse(swp_entry_t entry, struct page *page)
  105. {
  106. return 0;
  107. }
  108. #if 0
  109. int shmem_mmap(struct file *file, struct vm_area_struct *vma)
  110. {
  111. file_accessed(file);
  112. #ifndef CONFIG_MMU
  113. return ramfs_nommu_mmap(file, vma);
  114. #else
  115. return 0;
  116. #endif
  117. }
  118. #endif /* 0 */
  119. #ifndef CONFIG_MMU
  120. unsigned long shmem_get_unmapped_area(struct file *file,
  121. unsigned long addr,
  122. unsigned long len,
  123. unsigned long pgoff,
  124. unsigned long flags)
  125. {
  126. return ramfs_nommu_get_unmapped_area(file, addr, len, pgoff, flags);
  127. }
  128. #endif