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 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
31 unsigned long addr,
32 unsigned long len,
33 unsigned long pgoff,
34 unsigned long flags);
35 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);
36
ramfs_mmap_capabilities(struct file * file)37 static unsigned ramfs_mmap_capabilities(struct file *file)
38 {
39 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |
40 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
41 }
42
43 const struct file_operations ramfs_file_operations = {
44 .mmap_capabilities = ramfs_mmap_capabilities,
45 .mmap = ramfs_nommu_mmap,
46 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
47 .read_iter = generic_file_read_iter,
48 .write_iter = generic_file_write_iter,
49 .fsync = noop_fsync,
50 .splice_read = generic_file_splice_read,
51 .splice_write = iter_file_splice_write,
52 .llseek = generic_file_llseek,
53 };
54
55 const struct inode_operations ramfs_file_inode_operations = {
56 .setattr = ramfs_nommu_setattr,
57 .getattr = simple_getattr,
58 };
59
60 /*****************************************************************************/
61 /*
62 * add a contiguous set of pages into a ramfs inode when it's truncated from
63 * size 0 on the assumption that it's going to be used for an mmap of shared
64 * memory
65 */
ramfs_nommu_expand_for_mapping(struct inode * inode,size_t newsize)66 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
67 {
68 unsigned long npages, xpages, loop;
69 struct page *pages;
70 unsigned order;
71 void *data;
72 int ret;
73 gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
74
75 /* make various checks */
76 order = get_order(newsize);
77 if (unlikely(order >= MAX_ORDER))
78 return -EFBIG;
79
80 ret = inode_newsize_ok(inode, newsize);
81 if (ret)
82 return ret;
83
84 i_size_write(inode, newsize);
85
86 /* allocate enough contiguous pages to be able to satisfy the
87 * request */
88 pages = alloc_pages(gfp, order);
89 if (!pages)
90 return -ENOMEM;
91
92 /* split the high-order page into an array of single pages */
93 xpages = 1UL << order;
94 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
95
96 split_page(pages, order);
97
98 /* trim off any pages we don't actually require */
99 for (loop = npages; loop < xpages; loop++)
100 __free_page(pages + loop);
101
102 /* clear the memory we allocated */
103 newsize = PAGE_SIZE * npages;
104 data = page_address(pages);
105 memset(data, 0, newsize);
106
107 /* attach all the pages to the inode's address space */
108 for (loop = 0; loop < npages; loop++) {
109 struct page *page = pages + loop;
110
111 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
112 gfp);
113 if (ret < 0)
114 goto add_error;
115
116 /* prevent the page from being discarded on memory pressure */
117 SetPageDirty(page);
118 SetPageUptodate(page);
119
120 unlock_page(page);
121 put_page(page);
122 }
123
124 return 0;
125
126 add_error:
127 while (loop < npages)
128 __free_page(pages + loop++);
129 return ret;
130 }
131
132 /*****************************************************************************/
133 /*
134 *
135 */
ramfs_nommu_resize(struct inode * inode,loff_t newsize,loff_t size)136 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
137 {
138 int ret;
139
140 /* assume a truncate from zero size is going to be for the purposes of
141 * shared mmap */
142 if (size == 0) {
143 if (unlikely(newsize >> 32))
144 return -EFBIG;
145
146 return ramfs_nommu_expand_for_mapping(inode, newsize);
147 }
148
149 /* check that a decrease in size doesn't cut off any shared mappings */
150 if (newsize < size) {
151 ret = nommu_shrink_inode_mappings(inode, size, newsize);
152 if (ret < 0)
153 return ret;
154 }
155
156 truncate_setsize(inode, newsize);
157 return 0;
158 }
159
160 /*****************************************************************************/
161 /*
162 * handle a change of attributes
163 * - we're specifically interested in a change of size
164 */
ramfs_nommu_setattr(struct dentry * dentry,struct iattr * ia)165 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
166 {
167 struct inode *inode = d_inode(dentry);
168 unsigned int old_ia_valid = ia->ia_valid;
169 int ret = 0;
170
171 /* POSIX UID/GID verification for setting inode attributes */
172 ret = inode_change_ok(inode, ia);
173 if (ret)
174 return ret;
175
176 /* pick out size-changing events */
177 if (ia->ia_valid & ATTR_SIZE) {
178 loff_t size = inode->i_size;
179
180 if (ia->ia_size != size) {
181 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
182 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
183 goto out;
184 } else {
185 /* we skipped the truncate but must still update
186 * timestamps
187 */
188 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
189 }
190 }
191
192 setattr_copy(inode, ia);
193 out:
194 ia->ia_valid = old_ia_valid;
195 return ret;
196 }
197
198 /*****************************************************************************/
199 /*
200 * try to determine where a shared mapping can be made
201 * - we require that:
202 * - the pages to be mapped must exist
203 * - the pages be physically contiguous in sequence
204 */
ramfs_nommu_get_unmapped_area(struct file * file,unsigned long addr,unsigned long len,unsigned long pgoff,unsigned long flags)205 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
206 unsigned long addr, unsigned long len,
207 unsigned long pgoff, unsigned long flags)
208 {
209 unsigned long maxpages, lpages, nr, loop, ret;
210 struct inode *inode = file_inode(file);
211 struct page **pages = NULL, **ptr, *page;
212 loff_t isize;
213
214 if (!(flags & MAP_SHARED))
215 return addr;
216
217 /* the mapping mustn't extend beyond the EOF */
218 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
219 isize = i_size_read(inode);
220
221 ret = -EINVAL;
222 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
223 if (pgoff >= maxpages)
224 goto out;
225
226 if (maxpages - pgoff < lpages)
227 goto out;
228
229 /* gang-find the pages */
230 ret = -ENOMEM;
231 pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
232 if (!pages)
233 goto out_free;
234
235 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
236 if (nr != lpages)
237 goto out_free_pages; /* leave if some pages were missing */
238
239 /* check the pages for physical adjacency */
240 ptr = pages;
241 page = *ptr++;
242 page++;
243 for (loop = lpages; loop > 1; loop--)
244 if (*ptr++ != page++)
245 goto out_free_pages;
246
247 /* okay - all conditions fulfilled */
248 ret = (unsigned long) page_address(pages[0]);
249
250 out_free_pages:
251 ptr = pages;
252 for (loop = nr; loop > 0; loop--)
253 put_page(*ptr++);
254 out_free:
255 kfree(pages);
256 out:
257 return ret;
258 }
259
260 /*****************************************************************************/
261 /*
262 * set up a mapping for shared memory segments
263 */
ramfs_nommu_mmap(struct file * file,struct vm_area_struct * vma)264 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
265 {
266 if (!(vma->vm_flags & VM_SHARED))
267 return -ENOSYS;
268
269 file_accessed(file);
270 vma->vm_ops = &generic_file_vm_ops;
271 return 0;
272 }
273