fs/logfs/dev_mtd.c

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