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>
24 #include <asm/uaccess.h>
27 static int ramfs_nommu_setattr(struct dentry *, struct iattr *);
29 const struct address_space_operations ramfs_aops = {
30 .readpage = simple_readpage,
31 .write_begin = simple_write_begin,
32 .write_end = simple_write_end,
33 .set_page_dirty = __set_page_dirty_no_writeback,
36 const struct file_operations ramfs_file_operations = {
37 .mmap = ramfs_nommu_mmap,
38 .get_unmapped_area = ramfs_nommu_get_unmapped_area,
40 .aio_read = generic_file_aio_read,
41 .write = do_sync_write,
42 .aio_write = generic_file_aio_write,
43 .fsync = simple_sync_file,
44 .splice_read = generic_file_splice_read,
45 .splice_write = generic_file_splice_write,
46 .llseek = generic_file_llseek,
49 const struct inode_operations ramfs_file_inode_operations = {
50 .setattr = ramfs_nommu_setattr,
51 .getattr = simple_getattr,
54 /*****************************************************************************/
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
60 int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize)
62 struct pagevec lru_pvec;
63 unsigned long npages, xpages, loop, limit;
69 /* make various checks */
70 order = get_order(newsize);
71 if (unlikely(order >= MAX_ORDER))
74 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
75 if (limit != RLIM_INFINITY && newsize > limit)
78 if (newsize > inode->i_sb->s_maxbytes)
81 i_size_write(inode, newsize);
83 /* allocate enough contiguous pages to be able to satisfy the
85 pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order);
89 /* split the high-order page into an array of single pages */
90 xpages = 1UL << order;
91 npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT;
93 split_page(pages, order);
95 /* trim off any pages we don't actually require */
96 for (loop = npages; loop < xpages; loop++)
97 __free_page(pages + loop);
99 /* clear the memory we allocated */
100 newsize = PAGE_SIZE * npages;
101 data = page_address(pages);
102 memset(data, 0, newsize);
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;
109 ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL);
113 if (!pagevec_add(&lru_pvec, page))
114 __pagevec_lru_add_file(&lru_pvec);
116 /* prevent the page from being discarded on memory pressure */
122 pagevec_lru_add_file(&lru_pvec);
126 send_sig(SIGXFSZ, current, 0);
131 pagevec_lru_add_file(&lru_pvec);
132 page_cache_release(pages + loop);
133 for (loop++; loop < npages; loop++)
134 __free_page(pages + loop);
138 /*****************************************************************************/
140 * check that file shrinkage doesn't leave any VMAs dangling in midair
142 static int ramfs_nommu_check_mappings(struct inode *inode,
143 size_t newsize, size_t size)
145 struct vm_area_struct *vma;
146 struct prio_tree_iter iter;
148 /* search for VMAs that fall within the dead zone */
149 vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
150 newsize >> PAGE_SHIFT,
151 (size + PAGE_SIZE - 1) >> PAGE_SHIFT
153 /* found one - only interested if it's shared out of the page
155 if (vma->vm_flags & VM_SHARED)
156 return -ETXTBSY; /* not quite true, but near enough */
162 /*****************************************************************************/
166 static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
170 /* assume a truncate from zero size is going to be for the purposes of
173 if (unlikely(newsize >> 32))
176 return ramfs_nommu_expand_for_mapping(inode, newsize);
179 /* check that a decrease in size doesn't cut off any shared mappings */
180 if (newsize < size) {
181 ret = ramfs_nommu_check_mappings(inode, newsize, size);
186 ret = vmtruncate(inode, newsize);
191 /*****************************************************************************/
193 * handle a change of attributes
194 * - we're specifically interested in a change of size
196 static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia)
198 struct inode *inode = dentry->d_inode;
199 unsigned int old_ia_valid = ia->ia_valid;
202 /* POSIX UID/GID verification for setting inode attributes */
203 ret = inode_change_ok(inode, ia);
207 /* pick out size-changing events */
208 if (ia->ia_valid & ATTR_SIZE) {
209 loff_t size = i_size_read(inode);
210 if (ia->ia_size != size) {
211 ret = ramfs_nommu_resize(inode, ia->ia_size, size);
212 if (ret < 0 || ia->ia_valid == ATTR_SIZE)
215 /* we skipped the truncate but must still update
218 ia->ia_valid |= ATTR_MTIME|ATTR_CTIME;
222 ret = inode_setattr(inode, ia);
224 ia->ia_valid = old_ia_valid;
228 /*****************************************************************************/
230 * try to determine where a shared mapping can be made
232 * - the pages to be mapped must exist
233 * - the pages be physically contiguous in sequence
235 unsigned long ramfs_nommu_get_unmapped_area(struct file *file,
236 unsigned long addr, unsigned long len,
237 unsigned long pgoff, unsigned long flags)
239 unsigned long maxpages, lpages, nr, loop, ret;
240 struct inode *inode = file->f_path.dentry->d_inode;
241 struct page **pages = NULL, **ptr, *page;
244 if (!(flags & MAP_SHARED))
247 /* the mapping mustn't extend beyond the EOF */
248 lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
249 isize = i_size_read(inode);
252 maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT;
253 if (pgoff >= maxpages)
256 if (maxpages - pgoff < lpages)
259 /* gang-find the pages */
261 pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL);
265 nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages);
267 goto out_free_pages; /* leave if some pages were missing */
269 /* check the pages for physical adjacency */
273 for (loop = lpages; loop > 1; loop--)
274 if (*ptr++ != page++)
277 /* okay - all conditions fulfilled */
278 ret = (unsigned long) page_address(pages[0]);
282 for (loop = nr; loop > 0; loop--)
290 /*****************************************************************************/
292 * set up a mapping for shared memory segments
294 int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma)
296 if (!(vma->vm_flags & VM_SHARED))
300 vma->vm_ops = &generic_file_vm_ops;