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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,
Badari Pulavarty543ade12006-09-30 23:28:48 -070039 .read = do_sync_read,
40 .aio_read = generic_file_aio_read,
41 .write = do_sync_write,
42 .aio_write = generic_file_aio_write,
David Howells642fb4d2006-01-06 00:11:41 -080043 .fsync = simple_sync_file,
44 .sendfile = generic_file_sendfile,
45 .llseek = generic_file_llseek,
46};
47
48struct inode_operations ramfs_file_inode_operations = {
49 .setattr = ramfs_nommu_setattr,
50 .getattr = simple_getattr,
51};
52
53/*****************************************************************************/
54/*
55 * add a contiguous set of pages into a ramfs inode when it's truncated from
56 * size 0 on the assumption that it's going to be used for an mmap of shared
57 * memory
58 */
59static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
60{
61 struct pagevec lru_pvec;
62 unsigned long npages, xpages, loop, limit;
63 struct page *pages;
64 unsigned order;
65 void *data;
66 int ret;
67
68 /* make various checks */
69 order = get_order(newsize);
70 if (unlikely(order >= MAX_ORDER))
71 goto too_big;
72
73 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
74 if (limit != RLIM_INFINITY && newsize > limit)
75 goto fsize_exceeded;
76
77 if (newsize > inode->i_sb->s_maxbytes)
78 goto too_big;
79
80 i_size_write(inode, newsize);
81
82 /* allocate enough contiguous pages to be able to satisfy the
83 * request */
84 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
85 if (!pages)
86 return -ENOMEM;
87
88 /* split the high-order page into an array of single pages */
89 xpages = 1UL << order;
90 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
91
Nick Piggin84097512006-03-22 00:08:34 -080092 split_page(pages, order);
David Howells642fb4d2006-01-06 00:11:41 -080093
94 /* trim off any pages we don't actually require */
95 for (loop = npages; loop < xpages; loop++)
96 __free_page(pages + loop);
97
98 /* clear the memory we allocated */
99 newsize = PAGE_SIZE * npages;
100 data = page_address(pages);
101 memset(data, 0, newsize);
102
103 /* attach all the pages to the inode's address space */
104 pagevec_init(&lru_pvec, 0);
105 for (loop = 0; loop < npages; loop++) {
106 struct page *page = pages + loop;
107
108 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
109 if (ret < 0)
110 goto add_error;
111
112 if (!pagevec_add(&lru_pvec, page))
113 __pagevec_lru_add(&lru_pvec);
114
115 unlock_page(page);
116 }
117
118 pagevec_lru_add(&lru_pvec);
119 return 0;
120
121 fsize_exceeded:
122 send_sig(SIGXFSZ, current, 0);
123 too_big:
124 return -EFBIG;
125
126 add_error:
127 page_cache_release(pages + loop);
128 for (loop++; loop < npages; loop++)
129 __free_page(pages + loop);
130 return ret;
131}
132
133/*****************************************************************************/
134/*
135 * check that file shrinkage doesn't leave any VMAs dangling in midair
136 */
137static int ramfs_nommu_check_mappings(struct inode *inode,
138 size_t newsize, size_t size)
139{
140 struct vm_area_struct *vma;
141 struct prio_tree_iter iter;
142
143 /* search for VMAs that fall within the dead zone */
144 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
145 newsize >> PAGE_SHIFT,
146 (size + PAGE_SIZE - 1) >> PAGE_SHIFT
147 ) {
148 /* found one - only interested if it's shared out of the page
149 * cache */
150 if (vma->vm_flags & VM_SHARED)
151 return -ETXTBSY; /* not quite true, but near enough */
152 }
153
154 return 0;
155}
156
157/*****************************************************************************/
158/*
159 *
160 */
161static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
162{
163 int ret;
164
165 /* assume a truncate from zero size is going to be for the purposes of
166 * shared mmap */
167 if (size == 0) {
168 if (unlikely(newsize >> 32))
169 return -EFBIG;
170
171 return ramfs_nommu_expand_for_mapping(inode, newsize);
172 }
173
174 /* check that a decrease in size doesn't cut off any shared mappings */
175 if (newsize < size) {
176 ret = ramfs_nommu_check_mappings(inode, newsize, size);
177 if (ret < 0)
178 return ret;
179 }
180
181 ret = vmtruncate(inode, size);
182
183 return ret;
184}
185
186/*****************************************************************************/
187/*
188 * handle a change of attributes
189 * - we're specifically interested in a change of size
190 */
191static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
192{
193 struct inode *inode = dentry->d_inode;
194 unsigned int old_ia_valid = ia->ia_valid;
195 int ret = 0;
196
197 /* by providing our own setattr() method, we skip this quotaism */
198 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
199 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
200 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
201
202 /* pick out size-changing events */
203 if (ia->ia_valid & ATTR_SIZE) {
204 loff_t size = i_size_read(inode);
205 if (ia->ia_size != size) {
206 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
207 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
208 goto out;
209 } else {
210 /* we skipped the truncate but must still update
211 * timestamps
212 */
213 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
214 }
215 }
216
217 ret = inode_setattr(inode, ia);
218 out:
219 ia->ia_valid = old_ia_valid;
220 return ret;
221}
222
223/*****************************************************************************/
224/*
225 * try to determine where a shared mapping can be made
226 * - we require that:
227 * - the pages to be mapped must exist
228 * - the pages be physically contiguous in sequence
229 */
230unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
231 unsigned long addr, unsigned long len,
232 unsigned long pgoff, unsigned long flags)
233{
234 unsigned long maxpages, lpages, nr, loop, ret;
Josef Sipeka57c4d62006-12-08 02:37:32 -0800235 struct inode *inode = file->f_path.dentry->d_inode;
David Howells642fb4d2006-01-06 00:11:41 -0800236 struct page **pages = NULL, **ptr, *page;
237 loff_t isize;
238
239 if (!(flags & MAP_SHARED))
240 return addr;
241
242 /* the mapping mustn't extend beyond the EOF */
243 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
244 isize = i_size_read(inode);
245
246 ret = -EINVAL;
247 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
248 if (pgoff >= maxpages)
249 goto out;
250
251 if (maxpages - pgoff < lpages)
252 goto out;
253
254 /* gang-find the pages */
255 ret = -ENOMEM;
256 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
257 if (!pages)
258 goto out;
259
260 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
261 if (nr != lpages)
262 goto out; /* leave if some pages were missing */
263
264 /* check the pages for physical adjacency */
265 ptr = pages;
266 page = *ptr++;
267 page++;
268 for (loop = lpages; loop > 1; loop--)
269 if (*ptr++ != page++)
270 goto out;
271
272 /* okay - all conditions fulfilled */
273 ret = (unsigned long) page_address(pages[0]);
274
275 out:
276 if (pages) {
277 ptr = pages;
278 for (loop = lpages; loop > 0; loop--)
279 put_page(*ptr++);
280 kfree(pages);
281 }
282
283 return ret;
284}
285
286/*****************************************************************************/
287/*
David Howells21ff8212006-07-10 04:44:52 -0700288 * set up a mapping for shared memory segments
David Howells642fb4d2006-01-06 00:11:41 -0800289 */
290int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
291{
David Howells21ff8212006-07-10 04:44:52 -0700292 return vma->vm_flags & VM_SHARED ? 0 : -ENOSYS;
David Howells642fb4d2006-01-06 00:11:41 -0800293}