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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> | |
642fb4d1 DH |
19 | #include <linux/backing-dev.h> |
20 | #include <linux/ramfs.h> | |
642fb4d1 DH |
21 | #include <linux/pagevec.h> |
22 | #include <linux/mman.h> | |
23 | ||
24 | #include <asm/uaccess.h> | |
25 | #include "internal.h" | |
26 | ||
27 | static int ramfs_nommu_setattr(struct dentry *, struct iattr *); | |
28 | ||
f5e54d6e | 29 | const struct address_space_operations ramfs_aops = { |
642fb4d1 | 30 | .readpage = simple_readpage, |
800d15a5 NP |
31 | .write_begin = simple_write_begin, |
32 | .write_end = simple_write_end, | |
46626296 | 33 | .set_page_dirty = __set_page_dirty_no_writeback, |
642fb4d1 DH |
34 | }; |
35 | ||
4b6f5d20 | 36 | const struct file_operations ramfs_file_operations = { |
642fb4d1 DH |
37 | .mmap = ramfs_nommu_mmap, |
38 | .get_unmapped_area = ramfs_nommu_get_unmapped_area, | |
543ade1f BP |
39 | .read = do_sync_read, |
40 | .aio_read = generic_file_aio_read, | |
41 | .write = do_sync_write, | |
42 | .aio_write = generic_file_aio_write, | |
642fb4d1 | 43 | .fsync = simple_sync_file, |
5ffc4ef4 | 44 | .splice_read = generic_file_splice_read, |
8b3d3567 | 45 | .splice_write = generic_file_splice_write, |
642fb4d1 DH |
46 | .llseek = generic_file_llseek, |
47 | }; | |
48 | ||
c5ef1c42 | 49 | const struct inode_operations ramfs_file_inode_operations = { |
642fb4d1 DH |
50 | .setattr = ramfs_nommu_setattr, |
51 | .getattr = simple_getattr, | |
52 | }; | |
53 | ||
54 | /*****************************************************************************/ | |
55 | /* | |
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 | |
58 | * memory | |
59 | */ | |
4b19de6d | 60 | int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) |
642fb4d1 | 61 | { |
642fb4d1 DH |
62 | unsigned long npages, xpages, loop, limit; |
63 | struct page *pages; | |
64 | unsigned order; | |
65 | void *data; | |
66 | int ret; | |
67 | ||
68 | /* make various checks */ | |
69 | order = get_order(newsize); | |
70 | if (unlikely(order >= MAX_ORDER)) | |
71 | goto too_big; | |
72 | ||
73 | limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; | |
74 | if (limit != RLIM_INFINITY && newsize > limit) | |
75 | goto fsize_exceeded; | |
76 | ||
77 | if (newsize > inode->i_sb->s_maxbytes) | |
78 | goto too_big; | |
79 | ||
80 | i_size_write(inode, newsize); | |
81 | ||
82 | /* allocate enough contiguous pages to be able to satisfy the | |
83 | * request */ | |
84 | pages = alloc_pages(mapping_gfp_mask(inode->i_mapping), order); | |
85 | if (!pages) | |
86 | return -ENOMEM; | |
87 | ||
88 | /* split the high-order page into an array of single pages */ | |
89 | xpages = 1UL << order; | |
90 | npages = (newsize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
91 | ||
84097518 | 92 | split_page(pages, order); |
642fb4d1 DH |
93 | |
94 | /* trim off any pages we don't actually require */ | |
95 | for (loop = npages; loop < xpages; loop++) | |
96 | __free_page(pages + loop); | |
97 | ||
98 | /* clear the memory we allocated */ | |
99 | newsize = PAGE_SIZE * npages; | |
100 | data = page_address(pages); | |
101 | memset(data, 0, newsize); | |
102 | ||
103 | /* attach all the pages to the inode's address space */ | |
642fb4d1 DH |
104 | for (loop = 0; loop < npages; loop++) { |
105 | struct page *page = pages + loop; | |
106 | ||
2678958e JW |
107 | ret = add_to_page_cache_lru(page, inode->i_mapping, loop, |
108 | GFP_KERNEL); | |
642fb4d1 DH |
109 | if (ret < 0) |
110 | goto add_error; | |
111 | ||
020fe22f EB |
112 | /* prevent the page from being discarded on memory pressure */ |
113 | SetPageDirty(page); | |
114 | ||
642fb4d1 DH |
115 | unlock_page(page); |
116 | } | |
117 | ||
642fb4d1 DH |
118 | return 0; |
119 | ||
120 | fsize_exceeded: | |
121 | send_sig(SIGXFSZ, current, 0); | |
122 | too_big: | |
123 | return -EFBIG; | |
124 | ||
125 | add_error: | |
2678958e JW |
126 | while (loop < npages) |
127 | __free_page(pages + loop++); | |
642fb4d1 DH |
128 | return ret; |
129 | } | |
130 | ||
131 | /*****************************************************************************/ | |
132 | /* | |
133 | * check that file shrinkage doesn't leave any VMAs dangling in midair | |
134 | */ | |
135 | static int ramfs_nommu_check_mappings(struct inode *inode, | |
136 | size_t newsize, size_t size) | |
137 | { | |
138 | struct vm_area_struct *vma; | |
139 | struct prio_tree_iter iter; | |
140 | ||
141 | /* search for VMAs that fall within the dead zone */ | |
142 | vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, | |
143 | newsize >> PAGE_SHIFT, | |
144 | (size + PAGE_SIZE - 1) >> PAGE_SHIFT | |
145 | ) { | |
146 | /* found one - only interested if it's shared out of the page | |
147 | * cache */ | |
148 | if (vma->vm_flags & VM_SHARED) | |
149 | return -ETXTBSY; /* not quite true, but near enough */ | |
150 | } | |
151 | ||
152 | return 0; | |
153 | } | |
154 | ||
155 | /*****************************************************************************/ | |
156 | /* | |
157 | * | |
158 | */ | |
159 | static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) | |
160 | { | |
161 | int ret; | |
162 | ||
163 | /* assume a truncate from zero size is going to be for the purposes of | |
164 | * shared mmap */ | |
165 | if (size == 0) { | |
166 | if (unlikely(newsize >> 32)) | |
167 | return -EFBIG; | |
168 | ||
169 | return ramfs_nommu_expand_for_mapping(inode, newsize); | |
170 | } | |
171 | ||
172 | /* check that a decrease in size doesn't cut off any shared mappings */ | |
173 | if (newsize < size) { | |
174 | ret = ramfs_nommu_check_mappings(inode, newsize, size); | |
175 | if (ret < 0) | |
176 | return ret; | |
177 | } | |
178 | ||
3f0a6766 | 179 | ret = vmtruncate(inode, newsize); |
642fb4d1 DH |
180 | |
181 | return ret; | |
182 | } | |
183 | ||
184 | /*****************************************************************************/ | |
185 | /* | |
186 | * handle a change of attributes | |
187 | * - we're specifically interested in a change of size | |
188 | */ | |
189 | static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) | |
190 | { | |
191 | struct inode *inode = dentry->d_inode; | |
192 | unsigned int old_ia_valid = ia->ia_valid; | |
193 | int ret = 0; | |
194 | ||
85f6038f BW |
195 | /* POSIX UID/GID verification for setting inode attributes */ |
196 | ret = inode_change_ok(inode, ia); | |
197 | if (ret) | |
198 | return ret; | |
199 | ||
642fb4d1 DH |
200 | /* pick out size-changing events */ |
201 | if (ia->ia_valid & ATTR_SIZE) { | |
202 | loff_t size = i_size_read(inode); | |
203 | if (ia->ia_size != size) { | |
204 | ret = ramfs_nommu_resize(inode, ia->ia_size, size); | |
205 | if (ret < 0 || ia->ia_valid == ATTR_SIZE) | |
206 | goto out; | |
207 | } else { | |
208 | /* we skipped the truncate but must still update | |
209 | * timestamps | |
210 | */ | |
211 | ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; | |
212 | } | |
213 | } | |
214 | ||
215 | ret = inode_setattr(inode, ia); | |
216 | out: | |
217 | ia->ia_valid = old_ia_valid; | |
218 | return ret; | |
219 | } | |
220 | ||
221 | /*****************************************************************************/ | |
222 | /* | |
223 | * try to determine where a shared mapping can be made | |
224 | * - we require that: | |
225 | * - the pages to be mapped must exist | |
226 | * - the pages be physically contiguous in sequence | |
227 | */ | |
228 | unsigned long ramfs_nommu_get_unmapped_area(struct file *file, | |
229 | unsigned long addr, unsigned long len, | |
230 | unsigned long pgoff, unsigned long flags) | |
231 | { | |
232 | unsigned long maxpages, lpages, nr, loop, ret; | |
a57c4d65 | 233 | struct inode *inode = file->f_path.dentry->d_inode; |
642fb4d1 DH |
234 | struct page **pages = NULL, **ptr, *page; |
235 | loff_t isize; | |
236 | ||
237 | if (!(flags & MAP_SHARED)) | |
238 | return addr; | |
239 | ||
240 | /* the mapping mustn't extend beyond the EOF */ | |
241 | lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
242 | isize = i_size_read(inode); | |
243 | ||
244 | ret = -EINVAL; | |
245 | maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
246 | if (pgoff >= maxpages) | |
247 | goto out; | |
248 | ||
249 | if (maxpages - pgoff < lpages) | |
250 | goto out; | |
251 | ||
252 | /* gang-find the pages */ | |
253 | ret = -ENOMEM; | |
254 | pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); | |
255 | if (!pages) | |
0e8f989a | 256 | goto out_free; |
642fb4d1 DH |
257 | |
258 | nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); | |
259 | if (nr != lpages) | |
0e8f989a | 260 | goto out_free_pages; /* leave if some pages were missing */ |
642fb4d1 DH |
261 | |
262 | /* check the pages for physical adjacency */ | |
263 | ptr = pages; | |
264 | page = *ptr++; | |
265 | page++; | |
266 | for (loop = lpages; loop > 1; loop--) | |
267 | if (*ptr++ != page++) | |
0e8f989a | 268 | goto out_free_pages; |
642fb4d1 DH |
269 | |
270 | /* okay - all conditions fulfilled */ | |
271 | ret = (unsigned long) page_address(pages[0]); | |
272 | ||
0e8f989a DH |
273 | out_free_pages: |
274 | ptr = pages; | |
275 | for (loop = nr; loop > 0; loop--) | |
276 | put_page(*ptr++); | |
277 | out_free: | |
278 | kfree(pages); | |
279 | out: | |
642fb4d1 DH |
280 | return ret; |
281 | } | |
282 | ||
283 | /*****************************************************************************/ | |
284 | /* | |
21ff8216 | 285 | * set up a mapping for shared memory segments |
642fb4d1 DH |
286 | */ |
287 | int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) | |
288 | { | |
2e92a3ba DH |
289 | if (!(vma->vm_flags & VM_SHARED)) |
290 | return -ENOSYS; | |
291 | ||
292 | file_accessed(file); | |
293 | vma->vm_ops = &generic_file_vm_ops; | |
294 | return 0; | |
642fb4d1 | 295 | } |