file-nommu.c 6.6 KB

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  1. /* file-nommu.c: no-MMU version of ramfs
  2. *
  3. * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
  4. * Written by David Howells (dhowells@redhat.com)
  5. *
  6. * This program is free software; you can redistribute it and/or
  7. * modify it under the terms of the GNU General Public License
  8. * as published by the Free Software Foundation; either version
  9. * 2 of the License, or (at your option) any later version.
  10. */
  11. #include <linux/module.h>
  12. #include <linux/fs.h>
  13. #include <linux/mm.h>
  14. #include <linux/pagemap.h>
  15. #include <linux/highmem.h>
  16. #include <linux/init.h>
  17. #include <linux/string.h>
  18. #include <linux/backing-dev.h>
  19. #include <linux/ramfs.h>
  20. #include <linux/pagevec.h>
  21. #include <linux/mman.h>
  22. #include <linux/sched.h>
  23. #include <asm/uaccess.h>
  24. #include "internal.h"
  25. static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
  26. const struct address_space_operations ramfs_aops = {
  27. .readpage = simple_readpage,
  28. .write_begin = simple_write_begin,
  29. .write_end = simple_write_end,
  30. .set_page_dirty = __set_page_dirty_no_writeback,
  31. };
  32. const struct file_operations ramfs_file_operations = {
  33. .mmap = ramfs_nommu_mmap,
  34. .get_unmapped_area = ramfs_nommu_get_unmapped_area,
  35. .read = do_sync_read,
  36. .aio_read = generic_file_aio_read,
  37. .write = do_sync_write,
  38. .aio_write = generic_file_aio_write,
  39. .fsync = simple_sync_file,
  40. .splice_read = generic_file_splice_read,
  41. .splice_write = generic_file_splice_write,
  42. .llseek = generic_file_llseek,
  43. };
  44. const struct inode_operations ramfs_file_inode_operations = {
  45. .setattr = ramfs_nommu_setattr,
  46. .getattr = simple_getattr,
  47. };
  48. /*****************************************************************************/
  49. /*
  50. * add a contiguous set of pages into a ramfs inode when it's truncated from
  51. * size 0 on the assumption that it's going to be used for an mmap of shared
  52. * memory
  53. */
  54. int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
  55. {
  56. unsigned long npages, xpages, loop;
  57. struct page *pages;
  58. unsigned order;
  59. void *data;
  60. int ret;
  61. /* make various checks */
  62. order = get_order(newsize);
  63. if (unlikely(order >= MAX_ORDER))
  64. return -EFBIG;
  65. ret = inode_newsize_ok(inode, newsize);
  66. if (ret)
  67. return ret;
  68. i_size_write(inode, newsize);
  69. /* allocate enough contiguous pages to be able to satisfy the
  70. * request */
  71. pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
  72. if (!pages)
  73. return -ENOMEM;
  74. /* split the high-order page into an array of single pages */
  75. xpages = 1UL << order;
  76. npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  77. split_page(pages, order);
  78. /* trim off any pages we don't actually require */
  79. for (loop = npages; loop < xpages; loop++)
  80. __free_page(pages + loop);
  81. /* clear the memory we allocated */
  82. newsize = PAGE_SIZE * npages;
  83. data = page_address(pages);
  84. memset(data, 0, newsize);
  85. /* attach all the pages to the inode's address space */
  86. for (loop = 0; loop < npages; loop++) {
  87. struct page *page = pages + loop;
  88. ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
  89. GFP_KERNEL);
  90. if (ret < 0)
  91. goto add_error;
  92. /* prevent the page from being discarded on memory pressure */
  93. SetPageDirty(page);
  94. unlock_page(page);
  95. }
  96. return 0;
  97. add_error:
  98. while (loop < npages)
  99. __free_page(pages + loop++);
  100. return ret;
  101. }
  102. /*****************************************************************************/
  103. /*
  104. *
  105. */
  106. static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
  107. {
  108. int ret;
  109. /* assume a truncate from zero size is going to be for the purposes of
  110. * shared mmap */
  111. if (size == 0) {
  112. if (unlikely(newsize >> 32))
  113. return -EFBIG;
  114. return ramfs_nommu_expand_for_mapping(inode, newsize);
  115. }
  116. /* check that a decrease in size doesn't cut off any shared mappings */
  117. if (newsize < size) {
  118. ret = nommu_shrink_inode_mappings(inode, size, newsize);
  119. if (ret < 0)
  120. return ret;
  121. }
  122. ret = vmtruncate(inode, newsize);
  123. return ret;
  124. }
  125. /*****************************************************************************/
  126. /*
  127. * handle a change of attributes
  128. * - we're specifically interested in a change of size
  129. */
  130. static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
  131. {
  132. struct inode *inode = dentry->d_inode;
  133. unsigned int old_ia_valid = ia->ia_valid;
  134. int ret = 0;
  135. /* POSIX UID/GID verification for setting inode attributes */
  136. ret = inode_change_ok(inode, ia);
  137. if (ret)
  138. return ret;
  139. /* pick out size-changing events */
  140. if (ia->ia_valid & ATTR_SIZE) {
  141. loff_t size = i_size_read(inode);
  142. if (ia->ia_size != size) {
  143. ret = ramfs_nommu_resize(inode, ia->ia_size, size);
  144. if (ret < 0 || ia->ia_valid == ATTR_SIZE)
  145. goto out;
  146. } else {
  147. /* we skipped the truncate but must still update
  148. * timestamps
  149. */
  150. ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
  151. }
  152. }
  153. ret = inode_setattr(inode, ia);
  154. out:
  155. ia->ia_valid = old_ia_valid;
  156. return ret;
  157. }
  158. /*****************************************************************************/
  159. /*
  160. * try to determine where a shared mapping can be made
  161. * - we require that:
  162. * - the pages to be mapped must exist
  163. * - the pages be physically contiguous in sequence
  164. */
  165. unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
  166. unsigned long addr, unsigned long len,
  167. unsigned long pgoff, unsigned long flags)
  168. {
  169. unsigned long maxpages, lpages, nr, loop, ret;
  170. struct inode *inode = file->f_path.dentry->d_inode;
  171. struct page **pages = NULL, **ptr, *page;
  172. loff_t isize;
  173. if (!(flags & MAP_SHARED))
  174. return addr;
  175. /* the mapping mustn't extend beyond the EOF */
  176. lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
  177. isize = i_size_read(inode);
  178. ret = -EINVAL;
  179. maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
  180. if (pgoff >= maxpages)
  181. goto out;
  182. if (maxpages - pgoff < lpages)
  183. goto out;
  184. /* gang-find the pages */
  185. ret = -ENOMEM;
  186. pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
  187. if (!pages)
  188. goto out_free;
  189. nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
  190. if (nr != lpages)
  191. goto out_free_pages; /* leave if some pages were missing */
  192. /* check the pages for physical adjacency */
  193. ptr = pages;
  194. page = *ptr++;
  195. page++;
  196. for (loop = lpages; loop > 1; loop--)
  197. if (*ptr++ != page++)
  198. goto out_free_pages;
  199. /* okay - all conditions fulfilled */
  200. ret = (unsigned long) page_address(pages[0]);
  201. out_free_pages:
  202. ptr = pages;
  203. for (loop = nr; loop > 0; loop--)
  204. put_page(*ptr++);
  205. out_free:
  206. kfree(pages);
  207. out:
  208. return ret;
  209. }
  210. /*****************************************************************************/
  211. /*
  212. * set up a mapping for shared memory segments
  213. */
  214. int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
  215. {
  216. if (!(vma->vm_flags & VM_SHARED))
  217. return -ENOSYS;
  218. file_accessed(file);
  219. vma->vm_ops = &generic_file_vm_ops;
  220. return 0;
  221. }