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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>
David Howells642fb4d2006-01-06 00:11:41 -080021#include <linux/pagevec.h>
22#include <linux/mman.h>
23
24#include <asm/uaccess.h>
25#include "internal.h"
26
27static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
28
Christoph Hellwigf5e54d62006-06-28 04:26:44 -070029const struct address_space_operations ramfs_aops = {
David Howells642fb4d2006-01-06 00:11:41 -080030 .readpage = simple_readpage,
Nick Piggin800d15a2007-10-16 01:25:03 -070031 .write_begin = simple_write_begin,
32 .write_end = simple_write_end,
Ken Chen46626292007-02-10 01:43:17 -080033 .set_page_dirty = __set_page_dirty_no_writeback,
David Howells642fb4d2006-01-06 00:11:41 -080034};
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,
Jens Axboe5ffc4ef2007-06-01 11:49:19 +020044 .splice_read = generic_file_splice_read,
Octavian Purdila8b3d3562008-07-04 09:33:33 +020045 .splice_write = generic_file_splice_write,
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 */
Nick Piggin4b19de62008-10-02 14:50:16 -070060int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
David Howells642fb4d2006-01-06 00:11:41 -080061{
David Howells642fb4d2006-01-06 00:11:41 -080062 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 */
David Howells642fb4d2006-01-06 00:11:41 -0800104 for (loop = 0; loop < npages; loop++) {
105 struct page *page = pages + loop;
106
Johannes Weiner26789582009-03-31 15:23:29 -0700107 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
108 GFP_KERNEL);
David Howells642fb4d2006-01-06 00:11:41 -0800109 if (ret < 0)
110 goto add_error;
111
Enrik Berkhan020fe222009-03-13 13:51:56 -0700112 /* prevent the page from being discarded on memory pressure */
113 SetPageDirty(page);
114
David Howells642fb4d2006-01-06 00:11:41 -0800115 unlock_page(page);
116 }
117
David Howells642fb4d2006-01-06 00:11:41 -0800118 return 0;
119
120 fsize_exceeded:
121 send_sig(SIGXFSZ, current, 0);
122 too_big:
123 return -EFBIG;
124
125 add_error:
Johannes Weiner26789582009-03-31 15:23:29 -0700126 while (loop < npages)
127 __free_page(pages + loop++);
David Howells642fb4d2006-01-06 00:11:41 -0800128 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
Bryan Wu3f0a6762007-05-31 11:31:55 +0800179 ret = vmtruncate(inode, newsize);
David Howells642fb4d2006-01-06 00:11:41 -0800180
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
Bryan Wu85f60382007-06-05 11:02:01 +0800195 /* POSIX UID/GID verification for setting inode attributes */
196 ret = inode_change_ok(inode, ia);
197 if (ret)
198 return ret;
199
David Howells642fb4d2006-01-06 00:11:41 -0800200 /* 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;
Josef Sipeka57c4d62006-12-08 02:37:32 -0800233 struct inode *inode = file->f_path.dentry->d_inode;
David Howells642fb4d2006-01-06 00:11:41 -0800234 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)
David Howells0e8f9892009-01-08 12:04:46 +0000256 goto out_free;
David Howells642fb4d2006-01-06 00:11:41 -0800257
258 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
259 if (nr != lpages)
David Howells0e8f9892009-01-08 12:04:46 +0000260 goto out_free_pages; /* leave if some pages were missing */
David Howells642fb4d2006-01-06 00:11:41 -0800261
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++)
David Howells0e8f9892009-01-08 12:04:46 +0000268 goto out_free_pages;
David Howells642fb4d2006-01-06 00:11:41 -0800269
270 /* okay - all conditions fulfilled */
271 ret = (unsigned long) page_address(pages[0]);
272
David Howells0e8f9892009-01-08 12:04:46 +0000273out_free_pages:
274 ptr = pages;
275 for (loop = nr; loop > 0; loop--)
276 put_page(*ptr++);
277out_free:
278 kfree(pages);
279out:
David Howells642fb4d2006-01-06 00:11:41 -0800280 return ret;
281}
282
283/*****************************************************************************/
284/*
David Howells21ff8212006-07-10 04:44:52 -0700285 * set up a mapping for shared memory segments
David Howells642fb4d2006-01-06 00:11:41 -0800286 */
287int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
288{
David Howells2e92a3b2007-07-31 00:37:24 -0700289 if (!(vma->vm_flags & VM_SHARED))
290 return -ENOSYS;
291
292 file_accessed(file);
293 vma->vm_ops = &generic_file_vm_ops;
294 return 0;
David Howells642fb4d2006-01-06 00:11:41 -0800295}