blob: 677139b48e000d0d98100122c851eff5572aa14a [file] [log] [blame]
David Howells642fb4d2006-01-06 00:11:41 -08001/* 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/pagemap.h>
15#include <linux/highmem.h>
16#include <linux/init.h>
17#include <linux/string.h>
18#include <linux/smp_lock.h>
19#include <linux/backing-dev.h>
20#include <linux/ramfs.h>
21#include <linux/quotaops.h>
22#include <linux/pagevec.h>
23#include <linux/mman.h>
24
25#include <asm/uaccess.h>
26#include "internal.h"
27
28static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
29
Christoph Hellwigf5e54d62006-06-28 04:26:44 -070030const struct address_space_operations ramfs_aops = {
David Howells642fb4d2006-01-06 00:11:41 -080031 .readpage = simple_readpage,
32 .prepare_write = simple_prepare_write,
33 .commit_write = simple_commit_write
34};
35
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -080036const struct file_operations ramfs_file_operations = {
David Howells642fb4d2006-01-06 00:11:41 -080037 .mmap = ramfs_nommu_mmap,
38 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
39 .read = generic_file_read,
40 .write = generic_file_write,
41 .fsync = simple_sync_file,
42 .sendfile = generic_file_sendfile,
43 .llseek = generic_file_llseek,
44};
45
46struct inode_operations ramfs_file_inode_operations = {
47 .setattr = ramfs_nommu_setattr,
48 .getattr = simple_getattr,
49};
50
51/*****************************************************************************/
52/*
53 * add a contiguous set of pages into a ramfs inode when it's truncated from
54 * size 0 on the assumption that it's going to be used for an mmap of shared
55 * memory
56 */
57static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
58{
59 struct pagevec lru_pvec;
60 unsigned long npages, xpages, loop, limit;
61 struct page *pages;
62 unsigned order;
63 void *data;
64 int ret;
65
66 /* make various checks */
67 order = get_order(newsize);
68 if (unlikely(order >= MAX_ORDER))
69 goto too_big;
70
71 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
72 if (limit != RLIM_INFINITY && newsize > limit)
73 goto fsize_exceeded;
74
75 if (newsize > inode->i_sb->s_maxbytes)
76 goto too_big;
77
78 i_size_write(inode, newsize);
79
80 /* allocate enough contiguous pages to be able to satisfy the
81 * request */
82 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
83 if (!pages)
84 return -ENOMEM;
85
86 /* split the high-order page into an array of single pages */
87 xpages = 1UL << order;
88 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
89
Nick Piggin84097512006-03-22 00:08:34 -080090 split_page(pages, order);
David Howells642fb4d2006-01-06 00:11:41 -080091
92 /* trim off any pages we don't actually require */
93 for (loop = npages; loop < xpages; loop++)
94 __free_page(pages + loop);
95
96 /* clear the memory we allocated */
97 newsize = PAGE_SIZE * npages;
98 data = page_address(pages);
99 memset(data, 0, newsize);
100
101 /* attach all the pages to the inode's address space */
102 pagevec_init(&lru_pvec, 0);
103 for (loop = 0; loop < npages; loop++) {
104 struct page *page = pages + loop;
105
106 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
107 if (ret < 0)
108 goto add_error;
109
110 if (!pagevec_add(&lru_pvec, page))
111 __pagevec_lru_add(&lru_pvec);
112
113 unlock_page(page);
114 }
115
116 pagevec_lru_add(&lru_pvec);
117 return 0;
118
119 fsize_exceeded:
120 send_sig(SIGXFSZ, current, 0);
121 too_big:
122 return -EFBIG;
123
124 add_error:
125 page_cache_release(pages + loop);
126 for (loop++; loop < npages; loop++)
127 __free_page(pages + loop);
128 return ret;
129}
130
131/*****************************************************************************/
132/*
133 * check that file shrinkage doesn't leave any VMAs dangling in midair
134 */
135static int ramfs_nommu_check_mappings(struct inode *inode,
136 size_t newsize, size_t size)
137{
138 struct vm_area_struct *vma;
139 struct prio_tree_iter iter;
140
141 /* search for VMAs that fall within the dead zone */
142 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
143 newsize >> PAGE_SHIFT,
144 (size + PAGE_SIZE - 1) >> PAGE_SHIFT
145 ) {
146 /* found one - only interested if it's shared out of the page
147 * cache */
148 if (vma->vm_flags & VM_SHARED)
149 return -ETXTBSY; /* not quite true, but near enough */
150 }
151
152 return 0;
153}
154
155/*****************************************************************************/
156/*
157 *
158 */
159static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
160{
161 int ret;
162
163 /* assume a truncate from zero size is going to be for the purposes of
164 * shared mmap */
165 if (size == 0) {
166 if (unlikely(newsize >> 32))
167 return -EFBIG;
168
169 return ramfs_nommu_expand_for_mapping(inode, newsize);
170 }
171
172 /* check that a decrease in size doesn't cut off any shared mappings */
173 if (newsize < size) {
174 ret = ramfs_nommu_check_mappings(inode, newsize, size);
175 if (ret < 0)
176 return ret;
177 }
178
179 ret = vmtruncate(inode, size);
180
181 return ret;
182}
183
184/*****************************************************************************/
185/*
186 * handle a change of attributes
187 * - we're specifically interested in a change of size
188 */
189static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
190{
191 struct inode *inode = dentry->d_inode;
192 unsigned int old_ia_valid = ia->ia_valid;
193 int ret = 0;
194
195 /* by providing our own setattr() method, we skip this quotaism */
196 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
197 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
198 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
199
200 /* pick out size-changing events */
201 if (ia->ia_valid & ATTR_SIZE) {
202 loff_t size = i_size_read(inode);
203 if (ia->ia_size != size) {
204 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
205 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
206 goto out;
207 } else {
208 /* we skipped the truncate but must still update
209 * timestamps
210 */
211 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
212 }
213 }
214
215 ret = inode_setattr(inode, ia);
216 out:
217 ia->ia_valid = old_ia_valid;
218 return ret;
219}
220
221/*****************************************************************************/
222/*
223 * try to determine where a shared mapping can be made
224 * - we require that:
225 * - the pages to be mapped must exist
226 * - the pages be physically contiguous in sequence
227 */
228unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
229 unsigned long addr, unsigned long len,
230 unsigned long pgoff, unsigned long flags)
231{
232 unsigned long maxpages, lpages, nr, loop, ret;
233 struct inode *inode = file->f_dentry->d_inode;
234 struct page **pages = NULL, **ptr, *page;
235 loff_t isize;
236
237 if (!(flags & MAP_SHARED))
238 return addr;
239
240 /* the mapping mustn't extend beyond the EOF */
241 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
242 isize = i_size_read(inode);
243
244 ret = -EINVAL;
245 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
246 if (pgoff >= maxpages)
247 goto out;
248
249 if (maxpages - pgoff < lpages)
250 goto out;
251
252 /* gang-find the pages */
253 ret = -ENOMEM;
254 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
255 if (!pages)
256 goto out;
257
258 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
259 if (nr != lpages)
260 goto out; /* leave if some pages were missing */
261
262 /* check the pages for physical adjacency */
263 ptr = pages;
264 page = *ptr++;
265 page++;
266 for (loop = lpages; loop > 1; loop--)
267 if (*ptr++ != page++)
268 goto out;
269
270 /* okay - all conditions fulfilled */
271 ret = (unsigned long) page_address(pages[0]);
272
273 out:
274 if (pages) {
275 ptr = pages;
276 for (loop = lpages; loop > 0; loop--)
277 put_page(*ptr++);
278 kfree(pages);
279 }
280
281 return ret;
282}
283
284/*****************************************************************************/
285/*
David Howells21ff8212006-07-10 04:44:52 -0700286 * set up a mapping for shared memory segments
David Howells642fb4d2006-01-06 00:11:41 -0800287 */
288int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
289{
David Howells21ff8212006-07-10 04:44:52 -0700290 return vma->vm_flags & VM_SHARED ? 0 : -ENOSYS;
David Howells642fb4d2006-01-06 00:11:41 -0800291}