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
12 #include <linux/module.h>
13 #include <linux/fs.h>
14 #include <linux/mm.h>
15 #include <linux/pagemap.h>
16 #include <linux/highmem.h>
17 #include <linux/init.h>
18 #include <linux/string.h>
19 #include <linux/backing-dev.h>
20 #include <linux/ramfs.h>
21 #include <linux/pagevec.h>
22 #include <linux/mman.h>
23 #include <linux/sched.h>
24 #include <linux/slab.h>
25
26 #include <asm/uaccess.h>
27 #include "internal.h"
28
29 static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
30
31 const struct address_space_operations ramfs_aops = {
32 .readpage = simple_readpage,
33 .write_begin = simple_write_begin,
34 .write_end = simple_write_end,
35 .set_page_dirty = __set_page_dirty_no_writeback,
36 };
37
38 const struct file_operations ramfs_file_operations = {
39 .mmap = ramfs_nommu_mmap,
40 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
41 .read = do_sync_read,
42 .aio_read = generic_file_aio_read,
43 .write = do_sync_write,
44 .aio_write = generic_file_aio_write,
45 .fsync = noop_fsync,
46 .splice_read = generic_file_splice_read,
47 .splice_write = generic_file_splice_write,
48 .llseek = generic_file_llseek,
49 };
50
51 const struct inode_operations ramfs_file_inode_operations = {
52 .setattr = ramfs_nommu_setattr,
53 .getattr = simple_getattr,
54 };
55
56 /*****************************************************************************/
57 /*
58 * add a contiguous set of pages into a ramfs inode when it's truncated from
59 * size 0 on the assumption that it's going to be used for an mmap of shared
60 * memory
61 */
ramfs_nommu_expand_for_mapping(struct inode * inode,size_t newsize)62 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
63 {
64 unsigned long npages, xpages, loop;
65 struct page *pages;
66 unsigned order;
67 void *data;
68 int ret;
69
70 /* make various checks */
71 order = get_order(newsize);
72 if (unlikely(order >= MAX_ORDER))
73 return -EFBIG;
74
75 ret = inode_newsize_ok(inode, newsize);
76 if (ret)
77 return ret;
78
79 i_size_write(inode, newsize);
80
81 /* allocate enough contiguous pages to be able to satisfy the
82 * request */
83 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
84 if (!pages)
85 return -ENOMEM;
86
87 /* split the high-order page into an array of single pages */
88 xpages = 1UL << order;
89 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
90
91 split_page(pages, order);
92
93 /* trim off any pages we don't actually require */
94 for (loop = npages; loop < xpages; loop++)
95 __free_page(pages + loop);
96
97 /* clear the memory we allocated */
98 newsize = PAGE_SIZE * npages;
99 data = page_address(pages);
100 memset(data, 0, newsize);
101
102 /* attach all the pages to the inode's address space */
103 for (loop = 0; loop < npages; loop++) {
104 struct page *page = pages + loop;
105
106 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
107 GFP_KERNEL);
108 if (ret < 0)
109 goto add_error;
110
111 /* prevent the page from being discarded on memory pressure */
112 SetPageDirty(page);
113 SetPageUptodate(page);
114
115 unlock_page(page);
116 put_page(page);
117 }
118
119 return 0;
120
121 add_error:
122 while (loop < npages)
123 __free_page(pages + loop++);
124 return ret;
125 }
126
127 /*****************************************************************************/
128 /*
129 *
130 */
ramfs_nommu_resize(struct inode * inode,loff_t newsize,loff_t size)131 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
132 {
133 int ret;
134
135 /* assume a truncate from zero size is going to be for the purposes of
136 * shared mmap */
137 if (size == 0) {
138 if (unlikely(newsize >> 32))
139 return -EFBIG;
140
141 return ramfs_nommu_expand_for_mapping(inode, newsize);
142 }
143
144 /* check that a decrease in size doesn't cut off any shared mappings */
145 if (newsize < size) {
146 ret = nommu_shrink_inode_mappings(inode, size, newsize);
147 if (ret < 0)
148 return ret;
149 }
150
151 truncate_setsize(inode, newsize);
152 return 0;
153 }
154
155 /*****************************************************************************/
156 /*
157 * handle a change of attributes
158 * - we're specifically interested in a change of size
159 */
ramfs_nommu_setattr(struct dentry * dentry,struct iattr * ia)160 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
161 {
162 struct inode *inode = dentry->d_inode;
163 unsigned int old_ia_valid = ia->ia_valid;
164 int ret = 0;
165
166 /* POSIX UID/GID verification for setting inode attributes */
167 ret = inode_change_ok(inode, ia);
168 if (ret)
169 return ret;
170
171 /* pick out size-changing events */
172 if (ia->ia_valid & ATTR_SIZE) {
173 loff_t size = inode->i_size;
174
175 if (ia->ia_size != size) {
176 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
177 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
178 goto out;
179 } else {
180 /* we skipped the truncate but must still update
181 * timestamps
182 */
183 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
184 }
185 }
186
187 setattr_copy(inode, ia);
188 out:
189 ia->ia_valid = old_ia_valid;
190 return ret;
191 }
192
193 /*****************************************************************************/
194 /*
195 * try to determine where a shared mapping can be made
196 * - we require that:
197 * - the pages to be mapped must exist
198 * - the pages be physically contiguous in sequence
199 */
ramfs_nommu_get_unmapped_area(struct file * file,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)200 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
201 unsigned long addr, unsigned long len,
202 unsigned long pgoff, unsigned long flags)
203 {
204 unsigned long maxpages, lpages, nr, loop, ret;
205 struct inode *inode = file->f_path.dentry->d_inode;
206 struct page **pages = NULL, **ptr, *page;
207 loff_t isize;
208
209 if (!(flags & MAP_SHARED))
210 return addr;
211
212 /* the mapping mustn't extend beyond the EOF */
213 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
214 isize = i_size_read(inode);
215
216 ret = -EINVAL;
217 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
218 if (pgoff >= maxpages)
219 goto out;
220
221 if (maxpages - pgoff < lpages)
222 goto out;
223
224 /* gang-find the pages */
225 ret = -ENOMEM;
226 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
227 if (!pages)
228 goto out_free;
229
230 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
231 if (nr != lpages)
232 goto out_free_pages; /* leave if some pages were missing */
233
234 /* check the pages for physical adjacency */
235 ptr = pages;
236 page = *ptr++;
237 page++;
238 for (loop = lpages; loop > 1; loop--)
239 if (*ptr++ != page++)
240 goto out_free_pages;
241
242 /* okay - all conditions fulfilled */
243 ret = (unsigned long) page_address(pages[0]);
244
245 out_free_pages:
246 ptr = pages;
247 for (loop = nr; loop > 0; loop--)
248 put_page(*ptr++);
249 out_free:
250 kfree(pages);
251 out:
252 return ret;
253 }
254
255 /*****************************************************************************/
256 /*
257 * set up a mapping for shared memory segments
258 */
ramfs_nommu_mmap(struct file * file,struct vm_area_struct * vma)259 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
260 {
261 if (!(vma->vm_flags & VM_SHARED))
262 return -ENOSYS;
263
264 file_accessed(file);
265 vma->vm_ops = &generic_file_vm_ops;
266 return 0;
267 }
268