1/* 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/mm.h>
15#include <linux/pagemap.h>
16#include <linux/highmem.h>
17#include <linux/init.h>
18#include <linux/string.h>
19#include <linux/backing-dev.h>
20#include <linux/ramfs.h>
21#include <linux/pagevec.h>
22#include <linux/mman.h>
23#include <linux/sched.h>
24#include <linux/slab.h>
25
26#include <asm/uaccess.h>
27#include "internal.h"
28
29static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
30static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
31						   unsigned long addr,
32						   unsigned long len,
33						   unsigned long pgoff,
34						   unsigned long flags);
35static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);
36
37const struct file_operations ramfs_file_operations = {
38	.mmap			= ramfs_nommu_mmap,
39	.get_unmapped_area	= ramfs_nommu_get_unmapped_area,
40	.read			= new_sync_read,
41	.read_iter		= generic_file_read_iter,
42	.write			= new_sync_write,
43	.write_iter		= generic_file_write_iter,
44	.fsync			= noop_fsync,
45	.splice_read		= generic_file_splice_read,
46	.splice_write		= iter_file_splice_write,
47	.llseek			= generic_file_llseek,
48};
49
50const struct inode_operations ramfs_file_inode_operations = {
51	.setattr		= ramfs_nommu_setattr,
52	.getattr		= simple_getattr,
53};
54
55/*****************************************************************************/
56/*
57 * add a contiguous set of pages into a ramfs inode when it's truncated from
58 * size 0 on the assumption that it's going to be used for an mmap of shared
59 * memory
60 */
61int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
62{
63	unsigned long npages, xpages, loop;
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		return -EFBIG;
73
74	ret = inode_newsize_ok(inode, newsize);
75	if (ret)
76		return ret;
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
90	split_page(pages, order);
91
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	for (loop = 0; loop < npages; loop++) {
103		struct page *page = pages + loop;
104
105		ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
106					GFP_KERNEL);
107		if (ret < 0)
108			goto add_error;
109
110		/* prevent the page from being discarded on memory pressure */
111		SetPageDirty(page);
112		SetPageUptodate(page);
113
114		unlock_page(page);
115		put_page(page);
116	}
117
118	return 0;
119
120add_error:
121	while (loop < npages)
122		__free_page(pages + loop++);
123	return ret;
124}
125
126/*****************************************************************************/
127/*
128 *
129 */
130static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
131{
132	int ret;
133
134	/* assume a truncate from zero size is going to be for the purposes of
135	 * shared mmap */
136	if (size == 0) {
137		if (unlikely(newsize >> 32))
138			return -EFBIG;
139
140		return ramfs_nommu_expand_for_mapping(inode, newsize);
141	}
142
143	/* check that a decrease in size doesn't cut off any shared mappings */
144	if (newsize < size) {
145		ret = nommu_shrink_inode_mappings(inode, size, newsize);
146		if (ret < 0)
147			return ret;
148	}
149
150	truncate_setsize(inode, newsize);
151	return 0;
152}
153
154/*****************************************************************************/
155/*
156 * handle a change of attributes
157 * - we're specifically interested in a change of size
158 */
159static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
160{
161	struct inode *inode = dentry->d_inode;
162	unsigned int old_ia_valid = ia->ia_valid;
163	int ret = 0;
164
165	/* POSIX UID/GID verification for setting inode attributes */
166	ret = inode_change_ok(inode, ia);
167	if (ret)
168		return ret;
169
170	/* pick out size-changing events */
171	if (ia->ia_valid & ATTR_SIZE) {
172		loff_t size = inode->i_size;
173
174		if (ia->ia_size != size) {
175			ret = ramfs_nommu_resize(inode, ia->ia_size, size);
176			if (ret < 0 || ia->ia_valid == ATTR_SIZE)
177				goto out;
178		} else {
179			/* we skipped the truncate but must still update
180			 * timestamps
181			 */
182			ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
183		}
184	}
185
186	setattr_copy(inode, ia);
187 out:
188	ia->ia_valid = old_ia_valid;
189	return ret;
190}
191
192/*****************************************************************************/
193/*
194 * try to determine where a shared mapping can be made
195 * - we require that:
196 *   - the pages to be mapped must exist
197 *   - the pages be physically contiguous in sequence
198 */
199static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
200					    unsigned long addr, unsigned long len,
201					    unsigned long pgoff, unsigned long flags)
202{
203	unsigned long maxpages, lpages, nr, loop, ret;
204	struct inode *inode = file_inode(file);
205	struct page **pages = NULL, **ptr, *page;
206	loff_t isize;
207
208	if (!(flags & MAP_SHARED))
209		return addr;
210
211	/* the mapping mustn't extend beyond the EOF */
212	lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
213	isize = i_size_read(inode);
214
215	ret = -EINVAL;
216	maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
217	if (pgoff >= maxpages)
218		goto out;
219
220	if (maxpages - pgoff < lpages)
221		goto out;
222
223	/* gang-find the pages */
224	ret = -ENOMEM;
225	pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
226	if (!pages)
227		goto out_free;
228
229	nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
230	if (nr != lpages)
231		goto out_free_pages; /* leave if some pages were missing */
232
233	/* check the pages for physical adjacency */
234	ptr = pages;
235	page = *ptr++;
236	page++;
237	for (loop = lpages; loop > 1; loop--)
238		if (*ptr++ != page++)
239			goto out_free_pages;
240
241	/* okay - all conditions fulfilled */
242	ret = (unsigned long) page_address(pages[0]);
243
244out_free_pages:
245	ptr = pages;
246	for (loop = nr; loop > 0; loop--)
247		put_page(*ptr++);
248out_free:
249	kfree(pages);
250out:
251	return ret;
252}
253
254/*****************************************************************************/
255/*
256 * set up a mapping for shared memory segments
257 */
258static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
259{
260	if (!(vma->vm_flags & VM_SHARED))
261		return -ENOSYS;
262
263	file_accessed(file);
264	vma->vm_ops = &generic_file_vm_ops;
265	return 0;
266}
267