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	*ofs = 0;
156	while (mtd_block_isbad(mtd, *ofs)) {
157		*ofs += mtd->erasesize;
158		if (*ofs >= mtd->size)
159			return NULL;
160	}
161	BUG_ON(*ofs & ~PAGE_MASK);
162	return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
163}
164
165static struct page *logfs_mtd_find_last_sb(struct super_block *sb, u64 *ofs)
166{
167	struct logfs_super *super = logfs_super(sb);
168	struct address_space *mapping = super->s_mapping_inode->i_mapping;
169	filler_t *filler = logfs_mtd_readpage;
170	struct mtd_info *mtd = super->s_mtd;
171
172	*ofs = mtd->size - mtd->erasesize;
173	while (mtd_block_isbad(mtd, *ofs)) {
174		*ofs -= mtd->erasesize;
175		if (*ofs <= 0)
176			return NULL;
177	}
178	*ofs = *ofs + mtd->erasesize - 0x1000;
179	BUG_ON(*ofs & ~PAGE_MASK);
180	return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
181}
182
183static int __logfs_mtd_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
184		size_t nr_pages)
185{
186	struct logfs_super *super = logfs_super(sb);
187	struct address_space *mapping = super->s_mapping_inode->i_mapping;
188	struct page *page;
189	int i, err;
190
191	for (i = 0; i < nr_pages; i++) {
192		page = find_lock_page(mapping, index + i);
193		BUG_ON(!page);
194
195		err = loffs_mtd_write(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
196					page_address(page));
197		unlock_page(page);
198		page_cache_release(page);
199		if (err)
200			return err;
201	}
202	return 0;
203}
204
205static void logfs_mtd_writeseg(struct super_block *sb, u64 ofs, size_t len)
206{
207	struct logfs_super *super = logfs_super(sb);
208	int head;
209
210	if (super->s_flags & LOGFS_SB_FLAG_RO)
211		return;
212
213	if (len == 0) {
214		/* This can happen when the object fit perfectly into a
215		 * segment, the segment gets written per sync and subsequently
216		 * closed.
217		 */
218		return;
219	}
220	head = ofs & (PAGE_SIZE - 1);
221	if (head) {
222		ofs -= head;
223		len += head;
224	}
225	len = PAGE_ALIGN(len);
226	__logfs_mtd_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
227}
228
229static void logfs_mtd_put_device(struct logfs_super *s)
230{
231	put_mtd_device(s->s_mtd);
232}
233
234static int logfs_mtd_can_write_buf(struct super_block *sb, u64 ofs)
235{
236	struct logfs_super *super = logfs_super(sb);
237	void *buf;
238	int err;
239
240	buf = kmalloc(super->s_writesize, GFP_KERNEL);
241	if (!buf)
242		return -ENOMEM;
243	err = logfs_mtd_read(sb, ofs, super->s_writesize, buf);
244	if (err)
245		goto out;
246	if (memchr_inv(buf, 0xff, super->s_writesize))
247		err = -EIO;
248	kfree(buf);
249out:
250	return err;
251}
252
253static const struct logfs_device_ops mtd_devops = {
254	.find_first_sb	= logfs_mtd_find_first_sb,
255	.find_last_sb	= logfs_mtd_find_last_sb,
256	.readpage	= logfs_mtd_readpage,
257	.writeseg	= logfs_mtd_writeseg,
258	.erase		= logfs_mtd_erase,
259	.can_write_buf	= logfs_mtd_can_write_buf,
260	.sync		= logfs_mtd_sync,
261	.put_device	= logfs_mtd_put_device,
262};
263
264int logfs_get_sb_mtd(struct logfs_super *s, int mtdnr)
265{
266	struct mtd_info *mtd = get_mtd_device(NULL, mtdnr);
267	if (IS_ERR(mtd))
268		return PTR_ERR(mtd);
269
270	s->s_bdev = NULL;
271	s->s_mtd = mtd;
272	s->s_devops = &mtd_devops;
273	return 0;
274}
275