tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * fs/logfs/dev_mtd.c - Device access methods for MTD
3 *
4 * As should be obvious for Linux kernel code, license is GPLv2
5 *
6 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
7 */
8#include "logfs.h"
9#include <linux/completion.h>
10#include <linux/mount.h>
11#include <linux/sched.h>
12#include <linux/slab.h>
13
14#define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
15
16static int logfs_mtd_read(struct super_block *sb, loff_t ofs, size_t len,
17 void *buf)
18{
19 struct mtd_info *mtd = logfs_super(sb)->s_mtd;
20 size_t retlen;
21 int ret;
22
23 ret = mtd_read(mtd, ofs, len, &retlen, buf);
24 BUG_ON(ret == -EINVAL);
25 if (ret)
26 return ret;
27
28 /* Not sure if we should loop instead. */
29 if (retlen != len)
30 return -EIO;
31
32 return 0;
33}
34
35static int loffs_mtd_write(struct super_block *sb, loff_t ofs, size_t len,
36 void *buf)
37{
38 struct logfs_super *super = logfs_super(sb);
39 struct mtd_info *mtd = super->s_mtd;
40 size_t retlen;
41 loff_t page_start, page_end;
42 int ret;
43
44 if (super->s_flags & LOGFS_SB_FLAG_RO)
45 return -EROFS;
46
47 BUG_ON((ofs >= mtd->size) || (len > mtd->size - ofs));
48 BUG_ON(ofs != (ofs >> super->s_writeshift) << super->s_writeshift);
49 BUG_ON(len > PAGE_CACHE_SIZE);
50 page_start = ofs & PAGE_CACHE_MASK;
51 page_end = PAGE_CACHE_ALIGN(ofs + len) - 1;
52 ret = mtd_write(mtd, ofs, len, &retlen, buf);
53 if (ret || (retlen != len))
54 return -EIO;
55
56 return 0;
57}
58
59/*
60 * For as long as I can remember (since about 2001) mtd->erase has been an
61 * asynchronous interface lacking the first driver to actually use the
62 * asynchronous properties. So just to prevent the first implementor of such
63 * a thing from breaking logfs in 2350, we do the usual pointless dance to
64 * declare a completion variable and wait for completion before returning
65 * from logfs_mtd_erase(). What an exercise in futility!
66 */
67static void logfs_erase_callback(struct erase_info *ei)
68{
69 complete((struct completion *)ei->priv);
70}
71
72static int logfs_mtd_erase_mapping(struct super_block *sb, loff_t ofs,
73 size_t len)
74{
75 struct logfs_super *super = logfs_super(sb);
76 struct address_space *mapping = super->s_mapping_inode->i_mapping;
77 struct page *page;
78 pgoff_t index = ofs >> PAGE_SHIFT;
79
80 for (index = ofs >> PAGE_SHIFT; index < (ofs + len) >> PAGE_SHIFT; index++) {
81 page = find_get_page(mapping, index);
82 if (!page)
83 continue;
84 memset(page_address(page), 0xFF, PAGE_SIZE);
85 page_cache_release(page);
86 }
87 return 0;
88}
89
90static int logfs_mtd_erase(struct super_block *sb, loff_t ofs, size_t len,
91 int ensure_write)
92{
93 struct mtd_info *mtd = logfs_super(sb)->s_mtd;
94 struct erase_info ei;
95 DECLARE_COMPLETION_ONSTACK(complete);
96 int ret;
97
98 BUG_ON(len % mtd->erasesize);
99 if (logfs_super(sb)->s_flags & LOGFS_SB_FLAG_RO)
100 return -EROFS;
101
102 memset(&ei, 0, sizeof(ei));
103 ei.mtd = mtd;
104 ei.addr = ofs;
105 ei.len = len;
106 ei.callback = logfs_erase_callback;
107 ei.priv = (long)&complete;
108 ret = mtd_erase(mtd, &ei);
109 if (ret)
110 return -EIO;
111
112 wait_for_completion(&complete);
113 if (ei.state != MTD_ERASE_DONE)
114 return -EIO;
115 return logfs_mtd_erase_mapping(sb, ofs, len);
116}
117
118static void logfs_mtd_sync(struct super_block *sb)
119{
120 struct mtd_info *mtd = logfs_super(sb)->s_mtd;
121
122 mtd_sync(mtd);
123}
124
125static int logfs_mtd_readpage(void *_sb, struct page *page)
126{
127 struct super_block *sb = _sb;
128 int err;
129
130 err = logfs_mtd_read(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
131 page_address(page));
132 if (err == -EUCLEAN || err == -EBADMSG) {
133 /* -EBADMSG happens regularly on power failures */
134 err = 0;
135 /* FIXME: force GC this segment */
136 }
137 if (err) {
138 ClearPageUptodate(page);
139 SetPageError(page);
140 } else {
141 SetPageUptodate(page);
142 ClearPageError(page);
143 }
144 unlock_page(page);
145 return err;
146}
147
148static struct page *logfs_mtd_find_first_sb(struct super_block *sb, u64 *ofs)
149{
150 struct logfs_super *super = logfs_super(sb);
151 struct address_space *mapping = super->s_mapping_inode->i_mapping;
152 filler_t *filler = logfs_mtd_readpage;
153 struct mtd_info *mtd = super->s_mtd;
154
155 if (!mtd_can_have_bb(mtd))
156 return NULL;
157
158 *ofs = 0;
159 while (mtd_block_isbad(mtd, *ofs)) {
160 *ofs += mtd->erasesize;
161 if (*ofs >= mtd->size)
162 return NULL;
163 }
164 BUG_ON(*ofs & ~PAGE_MASK);
165 return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
166}
167
168static struct page *logfs_mtd_find_last_sb(struct super_block *sb, u64 *ofs)
169{
170 struct logfs_super *super = logfs_super(sb);
171 struct address_space *mapping = super->s_mapping_inode->i_mapping;
172 filler_t *filler = logfs_mtd_readpage;
173 struct mtd_info *mtd = super->s_mtd;
174
175 if (!mtd_can_have_bb(mtd))
176 return NULL;
177
178 *ofs = mtd->size - mtd->erasesize;
179 while (mtd_block_isbad(mtd, *ofs)) {
180 *ofs -= mtd->erasesize;
181 if (*ofs <= 0)
182 return NULL;
183 }
184 *ofs = *ofs + mtd->erasesize - 0x1000;
185 BUG_ON(*ofs & ~PAGE_MASK);
186 return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
187}
188
189static int __logfs_mtd_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
190 size_t nr_pages)
191{
192 struct logfs_super *super = logfs_super(sb);
193 struct address_space *mapping = super->s_mapping_inode->i_mapping;
194 struct page *page;
195 int i, err;
196
197 for (i = 0; i < nr_pages; i++) {
198 page = find_lock_page(mapping, index + i);
199 BUG_ON(!page);
200
201 err = loffs_mtd_write(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
202 page_address(page));
203 unlock_page(page);
204 page_cache_release(page);
205 if (err)
206 return err;
207 }
208 return 0;
209}
210
211static void logfs_mtd_writeseg(struct super_block *sb, u64 ofs, size_t len)
212{
213 struct logfs_super *super = logfs_super(sb);
214 int head;
215
216 if (super->s_flags & LOGFS_SB_FLAG_RO)
217 return;
218
219 if (len == 0) {
220 /* This can happen when the object fit perfectly into a
221 * segment, the segment gets written per sync and subsequently
222 * closed.
223 */
224 return;
225 }
226 head = ofs & (PAGE_SIZE - 1);
227 if (head) {
228 ofs -= head;
229 len += head;
230 }
231 len = PAGE_ALIGN(len);
232 __logfs_mtd_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
233}
234
235static void logfs_mtd_put_device(struct logfs_super *s)
236{
237 put_mtd_device(s->s_mtd);
238}
239
240static int logfs_mtd_can_write_buf(struct super_block *sb, u64 ofs)
241{
242 struct logfs_super *super = logfs_super(sb);
243 void *buf;
244 int err;
245
246 buf = kmalloc(super->s_writesize, GFP_KERNEL);
247 if (!buf)
248 return -ENOMEM;
249 err = logfs_mtd_read(sb, ofs, super->s_writesize, buf);
250 if (err)
251 goto out;
252 if (memchr_inv(buf, 0xff, super->s_writesize))
253 err = -EIO;
254 kfree(buf);
255out:
256 return err;
257}
258
259static const struct logfs_device_ops mtd_devops = {
260 .find_first_sb = logfs_mtd_find_first_sb,
261 .find_last_sb = logfs_mtd_find_last_sb,
262 .readpage = logfs_mtd_readpage,
263 .writeseg = logfs_mtd_writeseg,
264 .erase = logfs_mtd_erase,
265 .can_write_buf = logfs_mtd_can_write_buf,
266 .sync = logfs_mtd_sync,
267 .put_device = logfs_mtd_put_device,
268};
269
270int logfs_get_sb_mtd(struct logfs_super *s, int mtdnr)
271{
272 struct mtd_info *mtd = get_mtd_device(NULL, mtdnr);
273 if (IS_ERR(mtd))
274 return PTR_ERR(mtd);
275
276 s->s_bdev = NULL;
277 s->s_mtd = mtd;
278 s->s_devops = &mtd_devops;
279 return 0;
280}