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642fb4d1 DH |
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> | |
131612df | 14 | #include <linux/mm.h> |
642fb4d1 DH |
15 | #include <linux/pagemap.h> |
16 | #include <linux/highmem.h> | |
17 | #include <linux/init.h> | |
18 | #include <linux/string.h> | |
19 | #include <linux/smp_lock.h> | |
20 | #include <linux/backing-dev.h> | |
21 | #include <linux/ramfs.h> | |
22 | #include <linux/quotaops.h> | |
23 | #include <linux/pagevec.h> | |
24 | #include <linux/mman.h> | |
25 | ||
26 | #include <asm/uaccess.h> | |
27 | #include "internal.h" | |
28 | ||
29 | static int ramfs_nommu_setattr(struct dentry *, struct iattr *); | |
30 | ||
f5e54d6e | 31 | const struct address_space_operations ramfs_aops = { |
642fb4d1 DH |
32 | .readpage = simple_readpage, |
33 | .prepare_write = simple_prepare_write, | |
131612df | 34 | .commit_write = simple_commit_write, |
46626296 | 35 | .set_page_dirty = __set_page_dirty_no_writeback, |
642fb4d1 DH |
36 | }; |
37 | ||
4b6f5d20 | 38 | const struct file_operations ramfs_file_operations = { |
642fb4d1 DH |
39 | .mmap = ramfs_nommu_mmap, |
40 | .get_unmapped_area = ramfs_nommu_get_unmapped_area, | |
543ade1f BP |
41 | .read = do_sync_read, |
42 | .aio_read = generic_file_aio_read, | |
43 | .write = do_sync_write, | |
44 | .aio_write = generic_file_aio_write, | |
642fb4d1 DH |
45 | .fsync = simple_sync_file, |
46 | .sendfile = generic_file_sendfile, | |
47 | .llseek = generic_file_llseek, | |
48 | }; | |
49 | ||
c5ef1c42 | 50 | const struct inode_operations ramfs_file_inode_operations = { |
642fb4d1 DH |
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 | */ | |
61 | static int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) | |
62 | { | |
63 | struct pagevec lru_pvec; | |
64 | unsigned long npages, xpages, loop, limit; | |
65 | struct page *pages; | |
66 | unsigned order; | |
67 | void *data; | |
68 | int ret; | |
69 | ||
70 | /* make various checks */ | |
71 | order = get_order(newsize); | |
72 | if (unlikely(order >= MAX_ORDER)) | |
73 | goto too_big; | |
74 | ||
75 | limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; | |
76 | if (limit != RLIM_INFINITY && newsize > limit) | |
77 | goto fsize_exceeded; | |
78 | ||
79 | if (newsize > inode->i_sb->s_maxbytes) | |
80 | goto too_big; | |
81 | ||
82 | i_size_write(inode, newsize); | |
83 | ||
84 | /* allocate enough contiguous pages to be able to satisfy the | |
85 | * request */ | |
86 | pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); | |
87 | if (!pages) | |
88 | return -ENOMEM; | |
89 | ||
90 | /* split the high-order page into an array of single pages */ | |
91 | xpages = 1UL << order; | |
92 | npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
93 | ||
84097518 | 94 | split_page(pages, order); |
642fb4d1 DH |
95 | |
96 | /* trim off any pages we don't actually require */ | |
97 | for (loop = npages; loop < xpages; loop++) | |
98 | __free_page(pages + loop); | |
99 | ||
100 | /* clear the memory we allocated */ | |
101 | newsize = PAGE_SIZE * npages; | |
102 | data = page_address(pages); | |
103 | memset(data, 0, newsize); | |
104 | ||
105 | /* attach all the pages to the inode's address space */ | |
106 | pagevec_init(&lru_pvec, 0); | |
107 | for (loop = 0; loop < npages; loop++) { | |
108 | struct page *page = pages + loop; | |
109 | ||
110 | ret = add_to_page_cache(page, inode->i_mapping, loop, GFP_KERNEL); | |
111 | if (ret < 0) | |
112 | goto add_error; | |
113 | ||
114 | if (!pagevec_add(&lru_pvec, page)) | |
115 | __pagevec_lru_add(&lru_pvec); | |
116 | ||
117 | unlock_page(page); | |
118 | } | |
119 | ||
120 | pagevec_lru_add(&lru_pvec); | |
121 | return 0; | |
122 | ||
123 | fsize_exceeded: | |
124 | send_sig(SIGXFSZ, current, 0); | |
125 | too_big: | |
126 | return -EFBIG; | |
127 | ||
128 | add_error: | |
129 | page_cache_release(pages + loop); | |
130 | for (loop++; loop < npages; loop++) | |
131 | __free_page(pages + loop); | |
132 | return ret; | |
133 | } | |
134 | ||
135 | /*****************************************************************************/ | |
136 | /* | |
137 | * check that file shrinkage doesn't leave any VMAs dangling in midair | |
138 | */ | |
139 | static int ramfs_nommu_check_mappings(struct inode *inode, | |
140 | size_t newsize, size_t size) | |
141 | { | |
142 | struct vm_area_struct *vma; | |
143 | struct prio_tree_iter iter; | |
144 | ||
145 | /* search for VMAs that fall within the dead zone */ | |
146 | vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, | |
147 | newsize >> PAGE_SHIFT, | |
148 | (size + PAGE_SIZE - 1) >> PAGE_SHIFT | |
149 | ) { | |
150 | /* found one - only interested if it's shared out of the page | |
151 | * cache */ | |
152 | if (vma->vm_flags & VM_SHARED) | |
153 | return -ETXTBSY; /* not quite true, but near enough */ | |
154 | } | |
155 | ||
156 | return 0; | |
157 | } | |
158 | ||
159 | /*****************************************************************************/ | |
160 | /* | |
161 | * | |
162 | */ | |
163 | static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) | |
164 | { | |
165 | int ret; | |
166 | ||
167 | /* assume a truncate from zero size is going to be for the purposes of | |
168 | * shared mmap */ | |
169 | if (size == 0) { | |
170 | if (unlikely(newsize >> 32)) | |
171 | return -EFBIG; | |
172 | ||
173 | return ramfs_nommu_expand_for_mapping(inode, newsize); | |
174 | } | |
175 | ||
176 | /* check that a decrease in size doesn't cut off any shared mappings */ | |
177 | if (newsize < size) { | |
178 | ret = ramfs_nommu_check_mappings(inode, newsize, size); | |
179 | if (ret < 0) | |
180 | return ret; | |
181 | } | |
182 | ||
183 | ret = vmtruncate(inode, size); | |
184 | ||
185 | return ret; | |
186 | } | |
187 | ||
188 | /*****************************************************************************/ | |
189 | /* | |
190 | * handle a change of attributes | |
191 | * - we're specifically interested in a change of size | |
192 | */ | |
193 | static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) | |
194 | { | |
195 | struct inode *inode = dentry->d_inode; | |
196 | unsigned int old_ia_valid = ia->ia_valid; | |
197 | int ret = 0; | |
198 | ||
199 | /* by providing our own setattr() method, we skip this quotaism */ | |
200 | if ((old_ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) || | |
201 | (old_ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid)) | |
202 | ret = DQUOT_TRANSFER(inode, ia) ? -EDQUOT : 0; | |
203 | ||
204 | /* pick out size-changing events */ | |
205 | if (ia->ia_valid & ATTR_SIZE) { | |
206 | loff_t size = i_size_read(inode); | |
207 | if (ia->ia_size != size) { | |
208 | ret = ramfs_nommu_resize(inode, ia->ia_size, size); | |
209 | if (ret < 0 || ia->ia_valid == ATTR_SIZE) | |
210 | goto out; | |
211 | } else { | |
212 | /* we skipped the truncate but must still update | |
213 | * timestamps | |
214 | */ | |
215 | ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; | |
216 | } | |
217 | } | |
218 | ||
219 | ret = inode_setattr(inode, ia); | |
220 | out: | |
221 | ia->ia_valid = old_ia_valid; | |
222 | return ret; | |
223 | } | |
224 | ||
225 | /*****************************************************************************/ | |
226 | /* | |
227 | * try to determine where a shared mapping can be made | |
228 | * - we require that: | |
229 | * - the pages to be mapped must exist | |
230 | * - the pages be physically contiguous in sequence | |
231 | */ | |
232 | unsigned long ramfs_nommu_get_unmapped_area(struct file *file, | |
233 | unsigned long addr, unsigned long len, | |
234 | unsigned long pgoff, unsigned long flags) | |
235 | { | |
236 | unsigned long maxpages, lpages, nr, loop, ret; | |
a57c4d65 | 237 | struct inode *inode = file->f_path.dentry->d_inode; |
642fb4d1 DH |
238 | struct page **pages = NULL, **ptr, *page; |
239 | loff_t isize; | |
240 | ||
241 | if (!(flags & MAP_SHARED)) | |
242 | return addr; | |
243 | ||
244 | /* the mapping mustn't extend beyond the EOF */ | |
245 | lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
246 | isize = i_size_read(inode); | |
247 | ||
248 | ret = -EINVAL; | |
249 | maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
250 | if (pgoff >= maxpages) | |
251 | goto out; | |
252 | ||
253 | if (maxpages - pgoff < lpages) | |
254 | goto out; | |
255 | ||
256 | /* gang-find the pages */ | |
257 | ret = -ENOMEM; | |
258 | pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); | |
259 | if (!pages) | |
260 | goto out; | |
261 | ||
262 | nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); | |
263 | if (nr != lpages) | |
264 | goto out; /* leave if some pages were missing */ | |
265 | ||
266 | /* check the pages for physical adjacency */ | |
267 | ptr = pages; | |
268 | page = *ptr++; | |
269 | page++; | |
270 | for (loop = lpages; loop > 1; loop--) | |
271 | if (*ptr++ != page++) | |
272 | goto out; | |
273 | ||
274 | /* okay - all conditions fulfilled */ | |
275 | ret = (unsigned long) page_address(pages[0]); | |
276 | ||
277 | out: | |
278 | if (pages) { | |
279 | ptr = pages; | |
280 | for (loop = lpages; loop > 0; loop--) | |
281 | put_page(*ptr++); | |
282 | kfree(pages); | |
283 | } | |
284 | ||
285 | return ret; | |
286 | } | |
287 | ||
288 | /*****************************************************************************/ | |
289 | /* | |
21ff8216 | 290 | * set up a mapping for shared memory segments |
642fb4d1 DH |
291 | */ |
292 | int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) | |
293 | { | |
21ff8216 | 294 | return vma->vm_flags & VM_SHARED ? 0 : -ENOSYS; |
642fb4d1 | 295 | } |