aboutsummaryrefslogtreecommitdiffstats
path: root/fs/ramfs/file-nommu.c
blob: b9b567a28376313a33b74ad9668eda99134b70bc (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
/* file-nommu.c: no-MMU version of ramfs
 *
 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>
#include <linux/ramfs.h>
#include <linux/quotaops.h>
#include <linux/pagevec.h>
#include <linux/mman.h>

#include <asm/uaccess.h>
#include "internal.h"

static int ramfs_nommu_setattr(struct dentry *, struct iattr *);

const struct address_space_operations ramfs_aops = {
	.readpage		= simple_readpage,
	.write_begin		= simple_write_begin,
	.write_end		= simple_write_end,
	.set_page_dirty		= __set_page_dirty_no_writeback,
};

const struct file_operations ramfs_file_operations = {
	.mmap			= ramfs_nommu_mmap,
	.get_unmapped_area	= ramfs_nommu_get_unmapped_area,
	.read			= do_sync_read,
	.aio_read		= generic_file_aio_read,
	.write			= do_sync_write,
	.aio_write		= generic_file_aio_write,
	.fsync			= simple_sync_file,
	.splice_read		= generic_file_splice_read,
	.splice_write		= generic_file_splice_write,
	.llseek			= generic_file_llseek,
};

const struct inode_operations ramfs_file_inode_operations = {
	.setattr		= ramfs_nommu_setattr,
	.getattr		= simple_getattr,
};

/*****************************************************************************/
/*
 * add a contiguous set of pages into a ramfs inode when it's truncated from
 * size 0 on the assumption that it's going to be used for an mmap of shared
 * memory
 */
int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
{
	struct pagevec lru_pvec;
	unsigned long npages, xpages, loop, limit;
	struct page *pages;
	unsigned order;
	void *data;
	int ret;

	/* make various checks */
	order = get_order(newsize);
	if (unlikely(order >= MAX_ORDER))
		goto too_big;

	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
	if (limit != RLIM_INFINITY && newsize > limit)
		goto fsize_exceeded;

	if (newsize > inode->i_sb->s_maxbytes)
		goto too_big;

	i_size_write(inode, newsize);

	/* allocate enough contiguous pages to be able to satisfy the
	 * request */
	pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
	if (!pages)
		return -ENOMEM;

	/* split the high-order page into an array of single pages */
	xpages = 1UL << order;
	npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;

	split_page(pages, order);

	/* trim off any pages we don't actually require */
	for (loop = npages; loop < xpages; loop++)
		__free_page(pages + loop);

	/* clear the memory we allocated */
	newsize = PAGE_SIZE * npages;
	data = page_address(pages);
	memset(data, 0, newsize);

	/* attach all the pages to the inode's address space */
	pagevec_init(&lru_pvec, 0);
	for (loop = 0; loop < npages; loop++) {
		struct page *page = pages + loop;

		ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
		if (ret < 0)
			goto add_error;

		if (!pagevec_add(&lru_pvec, page))
			__pagevec_lru_add_file(&lru_pvec);

		unlock_page(page);
	}

	pagevec_lru_add_file(&lru_pvec);
	return 0;

 fsize_exceeded:
	send_sig(SIGXFSZ, current, 0);
 too_big:
	return -EFBIG;

 add_error:
	page_cache_release(pages + loop);
	for (loop++; loop < npages; loop++)
		__free_page(pages + loop);
	return ret;
}

/*****************************************************************************/
/*
 * check that file shrinkage doesn't leave any VMAs dangling in midair
 */
static int ramfs_nommu_check_mappings(struct inode *inode,
				      size_t newsize, size_t size)
{
	struct vm_area_struct *vma;
	struct prio_tree_iter iter;

	/* search for VMAs that fall within the dead zone */
	vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
			      newsize >> PAGE_SHIFT,
			      (size + PAGE_SIZE - 1) >> PAGE_SHIFT
			      ) {
		/* found one - only interested if it's shared out of the page
		 * cache */
		if (vma->vm_flags & VM_SHARED)
			return -ETXTBSY; /* not quite true, but near enough */
	}

	return 0;
}

/*****************************************************************************/
/*
 *
 */
static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
{
	int ret;

	/* assume a truncate from zero size is going to be for the purposes of
	 * shared mmap */
	if (size == 0) {
		if (unlikely(newsize >> 32))
			return -EFBIG;

		return ramfs_nommu_expand_for_mapping(inode, newsize);
	}

	/* check that a decrease in size doesn't cut off any shared mappings */
	if (newsize < size) {
		ret = ramfs_nommu_check_mappings(inode, newsize, size);
		if (ret < 0)
			return ret;
	}

	ret = vmtruncate(inode, newsize);

	return ret;
}

/*****************************************************************************/
/*
 * handle a change of attributes
 * - we're specifically interested in a change of size
 */
static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
{
	struct inode *inode = dentry->d_inode;
	unsigned int old_ia_valid = ia->ia_valid;
	int ret = 0;

	/* POSIX UID/GID verification for setting inode attributes */
	ret = inode_change_ok(inode, ia);
	if (ret)
		return ret;

	/* by providing our own setattr() method, we skip this quotaism */
	if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
	    (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid))
		ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0;

	/* pick out size-changing events */
	if (ia->ia_valid & ATTR_SIZE) {
		loff_t size = i_size_read(inode);
		if (ia->ia_size != size) {
			ret = ramfs_nommu_resize(inode, ia->ia_size, size);
			if (ret < 0 || ia->ia_valid == ATTR_SIZE)
				goto out;
		} else {
			/* we skipped the truncate but must still update
			 * timestamps
			 */
			ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
		}
	}

	ret = inode_setattr(inode, ia);
 out:
	ia->ia_valid = old_ia_valid;
	return ret;
}

/*****************************************************************************/
/*
 * try to determine where a shared mapping can be made
 * - we require that:
 *   - the pages to be mapped must exist
 *   - the pages be physically contiguous in sequence
 */
unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
					    unsigned long addr, unsigned long len,
					    unsigned long pgoff, unsigned long flags)
{
	unsigned long maxpages, lpages, nr, loop, ret;
	struct inode *inode = file->f_path.dentry->d_inode;
	struct page **pages = NULL, **ptr, *page;
	loff_t isize;

	if (!(flags & MAP_SHARED))
		return addr;

	/* the mapping mustn't extend beyond the EOF */
	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
	isize = i_size_read(inode);

	ret = -EINVAL;
	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
	if (pgoff >= maxpages)
		goto out;

	if (maxpages - pgoff < lpages)
		goto out;

	/* gang-find the pages */
	ret = -ENOMEM;
	pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
	if (!pages)
		goto out_free;

	nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
	if (nr != lpages)
		goto out_free_pages; /* leave if some pages were missing */

	/* check the pages for physical adjacency */
	ptr = pages;
	page = *ptr++;
	page++;
	for (loop = lpages; loop > 1; loop--)
		if (*ptr++ != page++)
			goto out_free_pages;

	/* okay - all conditions fulfilled */
	ret = (unsigned long) page_address(pages[0]);

out_free_pages:
	ptr = pages;
	for (loop = nr; loop > 0; loop--)
		put_page(*ptr++);
out_free:
	kfree(pages);
out:
	return ret;
}

/*****************************************************************************/
/*
 * set up a mapping for shared memory segments
 */
int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
{
	if (!(vma->vm_flags & VM_SHARED))
		return -ENOSYS;

	file_accessed(file);
	vma->vm_ops = &generic_file_vm_ops;
	return 0;
}