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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>
Dimitri Gorokhovik131612d2006-12-29 16:48:24 -080014#include <linux/mm.h>
David Howells642fb4d2006-01-06 00:11:41 -080015#include <linux/pagemap.h>
16#include <linux/highmem.h>
17#include <linux/init.h>
18#include <linux/string.h>
David Howells642fb4d2006-01-06 00:11:41 -080019#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,
Nick Piggin800d15a2007-10-16 01:25:03 -070032 .write_begin = simple_write_begin,
33 .write_end = simple_write_end,
Ken Chen46626292007-02-10 01:43:17 -080034 .set_page_dirty = __set_page_dirty_no_writeback,
David Howells642fb4d2006-01-06 00:11:41 -080035};
36
Arjan van de Ven4b6f5d22006-03-28 01:56:42 -080037const struct file_operations ramfs_file_operations = {
David Howells642fb4d2006-01-06 00:11:41 -080038 .mmap = ramfs_nommu_mmap,
39 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
Badari Pulavarty543ade12006-09-30 23:28:48 -070040 .read = do_sync_read,
41 .aio_read = generic_file_aio_read,
42 .write = do_sync_write,
43 .aio_write = generic_file_aio_write,
David Howells642fb4d2006-01-06 00:11:41 -080044 .fsync = simple_sync_file,
Jens Axboe5ffc4ef2007-06-01 11:49:19 +020045 .splice_read = generic_file_splice_read,
David Howells642fb4d2006-01-06 00:11:41 -080046 .llseek = generic_file_llseek,
47};
48
Arjan van de Venc5ef1c42007-02-12 00:55:40 -080049const struct inode_operations ramfs_file_inode_operations = {
David Howells642fb4d2006-01-06 00:11:41 -080050 .setattr = ramfs_nommu_setattr,
51 .getattr = simple_getattr,
52};
53
54/*****************************************************************************/
55/*
56 * add a contiguous set of pages into a ramfs inode when it's truncated from
57 * size 0 on the assumption that it's going to be used for an mmap of shared
58 * memory
59 */
60static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
61{
62 struct pagevec lru_pvec;
63 unsigned long npages, xpages, loop, limit;
64 struct page *pages;
65 unsigned order;
66 void *data;
67 int ret;
68
69 /* make various checks */
70 order = get_order(newsize);
71 if (unlikely(order >= MAX_ORDER))
72 goto too_big;
73
74 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
75 if (limit != RLIM_INFINITY && newsize > limit)
76 goto fsize_exceeded;
77
78 if (newsize > inode->i_sb->s_maxbytes)
79 goto too_big;
80
81 i_size_write(inode, newsize);
82
83 /* allocate enough contiguous pages to be able to satisfy the
84 * request */
85 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
86 if (!pages)
87 return -ENOMEM;
88
89 /* split the high-order page into an array of single pages */
90 xpages = 1UL << order;
91 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
92
Nick Piggin84097512006-03-22 00:08:34 -080093 split_page(pages, order);
David Howells642fb4d2006-01-06 00:11:41 -080094
95 /* trim off any pages we don't actually require */
96 for (loop = npages; loop < xpages; loop++)
97 __free_page(pages + loop);
98
99 /* clear the memory we allocated */
100 newsize = PAGE_SIZE * npages;
101 data = page_address(pages);
102 memset(data, 0, newsize);
103
104 /* attach all the pages to the inode's address space */
105 pagevec_init(&lru_pvec, 0);
106 for (loop = 0; loop < npages; loop++) {
107 struct page *page = pages + loop;
108
109 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
110 if (ret < 0)
111 goto add_error;
112
113 if (!pagevec_add(&lru_pvec, page))
114 __pagevec_lru_add(&lru_pvec);
115
116 unlock_page(page);
117 }
118
119 pagevec_lru_add(&lru_pvec);
120 return 0;
121
122 fsize_exceeded:
123 send_sig(SIGXFSZ, current, 0);
124 too_big:
125 return -EFBIG;
126
127 add_error:
128 page_cache_release(pages + loop);
129 for (loop++; loop < npages; loop++)
130 __free_page(pages + loop);
131 return ret;
132}
133
134/*****************************************************************************/
135/*
136 * check that file shrinkage doesn't leave any VMAs dangling in midair
137 */
138static int ramfs_nommu_check_mappings(struct inode *inode,
139 size_t newsize, size_t size)
140{
141 struct vm_area_struct *vma;
142 struct prio_tree_iter iter;
143
144 /* search for VMAs that fall within the dead zone */
145 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
146 newsize >> PAGE_SHIFT,
147 (size + PAGE_SIZE - 1) >> PAGE_SHIFT
148 ) {
149 /* found one - only interested if it's shared out of the page
150 * cache */
151 if (vma->vm_flags & VM_SHARED)
152 return -ETXTBSY; /* not quite true, but near enough */
153 }
154
155 return 0;
156}
157
158/*****************************************************************************/
159/*
160 *
161 */
162static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
163{
164 int ret;
165
166 /* assume a truncate from zero size is going to be for the purposes of
167 * shared mmap */
168 if (size == 0) {
169 if (unlikely(newsize >> 32))
170 return -EFBIG;
171
172 return ramfs_nommu_expand_for_mapping(inode, newsize);
173 }
174
175 /* check that a decrease in size doesn't cut off any shared mappings */
176 if (newsize < size) {
177 ret = ramfs_nommu_check_mappings(inode, newsize, size);
178 if (ret < 0)
179 return ret;
180 }
181
Bryan Wu3f0a6762007-05-31 11:31:55 +0800182 ret = vmtruncate(inode, newsize);
David Howells642fb4d2006-01-06 00:11:41 -0800183
184 return ret;
185}
186
187/*****************************************************************************/
188/*
189 * handle a change of attributes
190 * - we're specifically interested in a change of size
191 */
192static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
193{
194 struct inode *inode = dentry->d_inode;
195 unsigned int old_ia_valid = ia->ia_valid;
196 int ret = 0;
197
Bryan Wu85f60382007-06-05 11:02:01 +0800198 /* POSIX UID/GID verification for setting inode attributes */
199 ret = inode_change_ok(inode, ia);
200 if (ret)
201 return ret;
202
David Howells642fb4d2006-01-06 00:11:41 -0800203 /* by providing our own setattr() method, we skip this quotaism */
204 if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
205 (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
206 ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;
207
208 /* pick out size-changing events */
209 if (ia->ia_valid & ATTR_SIZE) {
210 loff_t size = i_size_read(inode);
211 if (ia->ia_size != size) {
212 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
213 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
214 goto out;
215 } else {
216 /* we skipped the truncate but must still update
217 * timestamps
218 */
219 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
220 }
221 }
222
223 ret = inode_setattr(inode, ia);
224 out:
225 ia->ia_valid = old_ia_valid;
226 return ret;
227}
228
229/*****************************************************************************/
230/*
231 * try to determine where a shared mapping can be made
232 * - we require that:
233 * - the pages to be mapped must exist
234 * - the pages be physically contiguous in sequence
235 */
236unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
237 unsigned long addr, unsigned long len,
238 unsigned long pgoff, unsigned long flags)
239{
240 unsigned long maxpages, lpages, nr, loop, ret;
Josef Sipeka57c4d62006-12-08 02:37:32 -0800241 struct inode *inode = file->f_path.dentry->d_inode;
David Howells642fb4d2006-01-06 00:11:41 -0800242 struct page **pages = NULL, **ptr, *page;
243 loff_t isize;
244
245 if (!(flags & MAP_SHARED))
246 return addr;
247
248 /* the mapping mustn't extend beyond the EOF */
249 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
250 isize = i_size_read(inode);
251
252 ret = -EINVAL;
253 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
254 if (pgoff >= maxpages)
255 goto out;
256
257 if (maxpages - pgoff < lpages)
258 goto out;
259
260 /* gang-find the pages */
261 ret = -ENOMEM;
262 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
263 if (!pages)
264 goto out;
265
266 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
267 if (nr != lpages)
268 goto out; /* leave if some pages were missing */
269
270 /* check the pages for physical adjacency */
271 ptr = pages;
272 page = *ptr++;
273 page++;
274 for (loop = lpages; loop > 1; loop--)
275 if (*ptr++ != page++)
276 goto out;
277
278 /* okay - all conditions fulfilled */
279 ret = (unsigned long) page_address(pages[0]);
280
281 out:
282 if (pages) {
283 ptr = pages;
284 for (loop = lpages; loop > 0; loop--)
285 put_page(*ptr++);
286 kfree(pages);
287 }
288
289 return ret;
290}
291
292/*****************************************************************************/
293/*
David Howells21ff8212006-07-10 04:44:52 -0700294 * set up a mapping for shared memory segments
David Howells642fb4d2006-01-06 00:11:41 -0800295 */
296int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
297{
David Howells2e92a3b2007-07-31 00:37:24 -0700298 if (!(vma->vm_flags & VM_SHARED))
299 return -ENOSYS;
300
301 file_accessed(file);
302 vma->vm_ops = &generic_file_vm_ops;
303 return 0;
David Howells642fb4d2006-01-06 00:11:41 -0800304}