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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> | |
5c805365 | 23 | #include <linux/sched.h> |
642fb4d1 DH |
24 | |
25 | #include <asm/uaccess.h> | |
26 | #include "internal.h" | |
27 | ||
28 | static int ramfs_nommu_setattr(struct dentry *, struct iattr *); | |
29 | ||
f5e54d6e | 30 | const struct address_space_operations ramfs_aops = { |
642fb4d1 | 31 | .readpage = simple_readpage, |
800d15a5 NP |
32 | .write_begin = simple_write_begin, |
33 | .write_end = simple_write_end, | |
46626296 | 34 | .set_page_dirty = __set_page_dirty_no_writeback, |
642fb4d1 DH |
35 | }; |
36 | ||
4b6f5d20 | 37 | const struct file_operations ramfs_file_operations = { |
642fb4d1 DH |
38 | .mmap = ramfs_nommu_mmap, |
39 | .get_unmapped_area = ramfs_nommu_get_unmapped_area, | |
543ade1f BP |
40 | .read = do_sync_read, |
41 | .aio_read = generic_file_aio_read, | |
42 | .write = do_sync_write, | |
43 | .aio_write = generic_file_aio_write, | |
642fb4d1 | 44 | .fsync = simple_sync_file, |
5ffc4ef4 | 45 | .splice_read = generic_file_splice_read, |
8b3d3567 | 46 | .splice_write = generic_file_splice_write, |
642fb4d1 DH |
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 | */ | |
4b19de6d | 61 | int ramfs_nommu_expand_for_mapping(struct inode *inode, size_t newsize) |
642fb4d1 | 62 | { |
0f67b0b0 | 63 | unsigned long npages, xpages, loop; |
642fb4d1 DH |
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)) | |
c08d3b0e | 72 | return -EFBIG; |
642fb4d1 | 73 | |
c08d3b0e | 74 | ret = inode_newsize_ok(inode, newsize); |
75 | if (ret) | |
76 | return ret; | |
642fb4d1 DH |
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 | ||
84097518 | 90 | split_page(pages, order); |
642fb4d1 DH |
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 */ | |
642fb4d1 DH |
102 | for (loop = 0; loop < npages; loop++) { |
103 | struct page *page = pages + loop; | |
104 | ||
2678958e JW |
105 | ret = add_to_page_cache_lru(page, inode->i_mapping, loop, |
106 | GFP_KERNEL); | |
642fb4d1 DH |
107 | if (ret < 0) |
108 | goto add_error; | |
109 | ||
020fe22f EB |
110 | /* prevent the page from being discarded on memory pressure */ |
111 | SetPageDirty(page); | |
112 | ||
642fb4d1 DH |
113 | unlock_page(page); |
114 | } | |
115 | ||
642fb4d1 DH |
116 | return 0; |
117 | ||
c08d3b0e | 118 | add_error: |
2678958e JW |
119 | while (loop < npages) |
120 | __free_page(pages + loop++); | |
642fb4d1 DH |
121 | return ret; |
122 | } | |
123 | ||
124 | /*****************************************************************************/ | |
125 | /* | |
126 | * check that file shrinkage doesn't leave any VMAs dangling in midair | |
127 | */ | |
128 | static int ramfs_nommu_check_mappings(struct inode *inode, | |
129 | size_t newsize, size_t size) | |
130 | { | |
131 | struct vm_area_struct *vma; | |
132 | struct prio_tree_iter iter; | |
133 | ||
134 | /* search for VMAs that fall within the dead zone */ | |
135 | vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap, | |
136 | newsize >> PAGE_SHIFT, | |
137 | (size + PAGE_SIZE - 1) >> PAGE_SHIFT | |
138 | ) { | |
139 | /* found one - only interested if it's shared out of the page | |
140 | * cache */ | |
141 | if (vma->vm_flags & VM_SHARED) | |
142 | return -ETXTBSY; /* not quite true, but near enough */ | |
143 | } | |
144 | ||
145 | return 0; | |
146 | } | |
147 | ||
148 | /*****************************************************************************/ | |
149 | /* | |
150 | * | |
151 | */ | |
152 | static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size) | |
153 | { | |
154 | int ret; | |
155 | ||
156 | /* assume a truncate from zero size is going to be for the purposes of | |
157 | * shared mmap */ | |
158 | if (size == 0) { | |
159 | if (unlikely(newsize >> 32)) | |
160 | return -EFBIG; | |
161 | ||
162 | return ramfs_nommu_expand_for_mapping(inode, newsize); | |
163 | } | |
164 | ||
165 | /* check that a decrease in size doesn't cut off any shared mappings */ | |
166 | if (newsize < size) { | |
167 | ret = ramfs_nommu_check_mappings(inode, newsize, size); | |
168 | if (ret < 0) | |
169 | return ret; | |
170 | } | |
171 | ||
3f0a6766 | 172 | ret = vmtruncate(inode, newsize); |
642fb4d1 DH |
173 | |
174 | return ret; | |
175 | } | |
176 | ||
177 | /*****************************************************************************/ | |
178 | /* | |
179 | * handle a change of attributes | |
180 | * - we're specifically interested in a change of size | |
181 | */ | |
182 | static int ramfs_nommu_setattr(struct dentry *dentry, struct iattr *ia) | |
183 | { | |
184 | struct inode *inode = dentry->d_inode; | |
185 | unsigned int old_ia_valid = ia->ia_valid; | |
186 | int ret = 0; | |
187 | ||
85f6038f BW |
188 | /* POSIX UID/GID verification for setting inode attributes */ |
189 | ret = inode_change_ok(inode, ia); | |
190 | if (ret) | |
191 | return ret; | |
192 | ||
642fb4d1 DH |
193 | /* pick out size-changing events */ |
194 | if (ia->ia_valid & ATTR_SIZE) { | |
195 | loff_t size = i_size_read(inode); | |
196 | if (ia->ia_size != size) { | |
197 | ret = ramfs_nommu_resize(inode, ia->ia_size, size); | |
198 | if (ret < 0 || ia->ia_valid == ATTR_SIZE) | |
199 | goto out; | |
200 | } else { | |
201 | /* we skipped the truncate but must still update | |
202 | * timestamps | |
203 | */ | |
204 | ia->ia_valid |= ATTR_MTIME|ATTR_CTIME; | |
205 | } | |
206 | } | |
207 | ||
208 | ret = inode_setattr(inode, ia); | |
209 | out: | |
210 | ia->ia_valid = old_ia_valid; | |
211 | return ret; | |
212 | } | |
213 | ||
214 | /*****************************************************************************/ | |
215 | /* | |
216 | * try to determine where a shared mapping can be made | |
217 | * - we require that: | |
218 | * - the pages to be mapped must exist | |
219 | * - the pages be physically contiguous in sequence | |
220 | */ | |
221 | unsigned long ramfs_nommu_get_unmapped_area(struct file *file, | |
222 | unsigned long addr, unsigned long len, | |
223 | unsigned long pgoff, unsigned long flags) | |
224 | { | |
225 | unsigned long maxpages, lpages, nr, loop, ret; | |
a57c4d65 | 226 | struct inode *inode = file->f_path.dentry->d_inode; |
642fb4d1 DH |
227 | struct page **pages = NULL, **ptr, *page; |
228 | loff_t isize; | |
229 | ||
230 | if (!(flags & MAP_SHARED)) | |
231 | return addr; | |
232 | ||
233 | /* the mapping mustn't extend beyond the EOF */ | |
234 | lpages = (len + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
235 | isize = i_size_read(inode); | |
236 | ||
237 | ret = -EINVAL; | |
238 | maxpages = (isize + PAGE_SIZE - 1) >> PAGE_SHIFT; | |
239 | if (pgoff >= maxpages) | |
240 | goto out; | |
241 | ||
242 | if (maxpages - pgoff < lpages) | |
243 | goto out; | |
244 | ||
245 | /* gang-find the pages */ | |
246 | ret = -ENOMEM; | |
247 | pages = kzalloc(lpages * sizeof(struct page *), GFP_KERNEL); | |
248 | if (!pages) | |
0e8f989a | 249 | goto out_free; |
642fb4d1 DH |
250 | |
251 | nr = find_get_pages(inode->i_mapping, pgoff, lpages, pages); | |
252 | if (nr != lpages) | |
0e8f989a | 253 | goto out_free_pages; /* leave if some pages were missing */ |
642fb4d1 DH |
254 | |
255 | /* check the pages for physical adjacency */ | |
256 | ptr = pages; | |
257 | page = *ptr++; | |
258 | page++; | |
259 | for (loop = lpages; loop > 1; loop--) | |
260 | if (*ptr++ != page++) | |
0e8f989a | 261 | goto out_free_pages; |
642fb4d1 DH |
262 | |
263 | /* okay - all conditions fulfilled */ | |
264 | ret = (unsigned long) page_address(pages[0]); | |
265 | ||
0e8f989a DH |
266 | out_free_pages: |
267 | ptr = pages; | |
268 | for (loop = nr; loop > 0; loop--) | |
269 | put_page(*ptr++); | |
270 | out_free: | |
271 | kfree(pages); | |
272 | out: | |
642fb4d1 DH |
273 | return ret; |
274 | } | |
275 | ||
276 | /*****************************************************************************/ | |
277 | /* | |
21ff8216 | 278 | * set up a mapping for shared memory segments |
642fb4d1 DH |
279 | */ |
280 | int ramfs_nommu_mmap(struct file *file, struct vm_area_struct *vma) | |
281 | { | |
2e92a3ba DH |
282 | if (!(vma->vm_flags & VM_SHARED)) |
283 | return -ENOSYS; | |
284 | ||
285 | file_accessed(file); | |
286 | vma->vm_ops = &generic_file_vm_ops; | |
287 | return 0; | |
642fb4d1 | 288 | } |