1 /* file-nommu.c: no-MMU version of ramfs
3 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
12 #include <linux/module.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>
26 #include <asm/uaccess.h>
29 static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
30 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
35 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma);
37 static unsigned ramfs_mmap_capabilities(struct file *file)
39 return NOMMU_MAP_DIRECT | NOMMU_MAP_COPY | NOMMU_MAP_READ |
40 NOMMU_MAP_WRITE | NOMMU_MAP_EXEC;
43 const struct file_operations ramfs_file_operations = {
44 .mmap_capabilities = ramfs_mmap_capabilities,
45 .mmap = ramfs_nommu_mmap,
46 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
47 .read = new_sync_read,
48 .read_iter = generic_file_read_iter,
49 .write = new_sync_write,
50 .write_iter = generic_file_write_iter,
52 .splice_read = generic_file_splice_read,
53 .splice_write = iter_file_splice_write,
54 .llseek = generic_file_llseek,
57 const struct inode_operations ramfs_file_inode_operations = {
58 .setattr = ramfs_nommu_setattr,
59 .getattr = simple_getattr,
62 /*****************************************************************************/
64 * add a contiguous set of pages into a ramfs inode when it's truncated from
65 * size 0 on the assumption that it's going to be used for an mmap of shared
68 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
70 unsigned long npages, xpages, loop;
76 /* make various checks */
77 order = get_order(newsize);
78 if (unlikely(order >= MAX_ORDER))
81 ret = inode_newsize_ok(inode, newsize);
85 i_size_write(inode, newsize);
87 /* allocate enough contiguous pages to be able to satisfy the
89 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
93 /* split the high-order page into an array of single pages */
94 xpages = 1UL << order;
95 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
97 split_page(pages, order);
99 /* trim off any pages we don't actually require */
100 for (loop = npages; loop < xpages; loop++)
101 __free_page(pages + loop);
103 /* clear the memory we allocated */
104 newsize = PAGE_SIZE * npages;
105 data = page_address(pages);
106 memset(data, 0, newsize);
108 /* attach all the pages to the inode's address space */
109 for (loop = 0; loop < npages; loop++) {
110 struct page *page = pages + loop;
112 ret = add_to_page_cache_lru(page, inode->i_mapping, loop,
117 /* prevent the page from being discarded on memory pressure */
119 SetPageUptodate(page);
128 while (loop < npages)
129 __free_page(pages + loop++);
133 /*****************************************************************************/
137 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
141 /* assume a truncate from zero size is going to be for the purposes of
144 if (unlikely(newsize >> 32))
147 return ramfs_nommu_expand_for_mapping(inode, newsize);
150 /* check that a decrease in size doesn't cut off any shared mappings */
151 if (newsize < size) {
152 ret = nommu_shrink_inode_mappings(inode, size, newsize);
157 truncate_setsize(inode, newsize);
161 /*****************************************************************************/
163 * handle a change of attributes
164 * - we're specifically interested in a change of size
166 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
168 struct inode *inode = dentry->d_inode;
169 unsigned int old_ia_valid = ia->ia_valid;
172 /* POSIX UID/GID verification for setting inode attributes */
173 ret = inode_change_ok(inode, ia);
177 /* pick out size-changing events */
178 if (ia->ia_valid & ATTR_SIZE) {
179 loff_t size = inode->i_size;
181 if (ia->ia_size != size) {
182 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
183 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
186 /* we skipped the truncate but must still update
189 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
193 setattr_copy(inode, ia);
195 ia->ia_valid = old_ia_valid;
199 /*****************************************************************************/
201 * try to determine where a shared mapping can be made
203 * - the pages to be mapped must exist
204 * - the pages be physically contiguous in sequence
206 static unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
207 unsigned long addr, unsigned long len,
208 unsigned long pgoff, unsigned long flags)
210 unsigned long maxpages, lpages, nr, loop, ret;
211 struct inode *inode = file_inode(file);
212 struct page **pages = NULL, **ptr, *page;
215 if (!(flags & MAP_SHARED))
218 /* the mapping mustn't extend beyond the EOF */
219 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
220 isize = i_size_read(inode);
223 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
224 if (pgoff >= maxpages)
227 if (maxpages - pgoff < lpages)
230 /* gang-find the pages */
232 pages = kcalloc(lpages, sizeof(struct page *), GFP_KERNEL);
236 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
238 goto out_free_pages; /* leave if some pages were missing */
240 /* check the pages for physical adjacency */
244 for (loop = lpages; loop > 1; loop--)
245 if (*ptr++ != page++)
248 /* okay - all conditions fulfilled */
249 ret = (unsigned long) page_address(pages[0]);
253 for (loop = nr; loop > 0; loop--)
261 /*****************************************************************************/
263 * set up a mapping for shared memory segments
265 static int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
267 if (!(vma->vm_flags & VM_SHARED))
271 vma->vm_ops = &generic_file_vm_ops;