release/src-rt-6.x.4708/linux/linux-2.6.36/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         }
 134         if (err) {
 135                 ClearPageUptodate(page);
 136                 SetPageError(page);
 137         } else {
 138                 SetPageUptodate(page);
 139                 ClearPageError(page);
 140         }
 141         unlock_page(page);
 142         return err;
 143 }
 144
 145 static struct page *mtd_find_first_sb(struct super_block *sb, u64 *ofs)
 146 {
 147         struct logfs_super *super = logfs_super(sb);
 148         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 149         filler_t *filler = mtd_readpage;
 150         struct mtd_info *mtd = super->s_mtd;
 151
 152         if (!mtd->block_isbad)
 153                 return NULL;
 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
 165 static struct page *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 = mtd_readpage;
 170         struct mtd_info *mtd = super->s_mtd;
 171
 172         if (!mtd->block_isbad)
 173                 return NULL;
 174
 175         *ofs = mtd->size - mtd->erasesize;
 176         while (mtd->block_isbad(mtd, *ofs)) {
 177                 *ofs -= mtd->erasesize;
 178                 if (*ofs <= 0)
 179                         return NULL;
 180         }
 181         *ofs = *ofs + mtd->erasesize - 0x1000;
 182         BUG_ON(*ofs & ~PAGE_MASK);
 183         return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
 184 }
 185
 186 static int __mtd_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
 187                 size_t nr_pages)
 188 {
 189         struct logfs_super *super = logfs_super(sb);
 190         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 191         struct page *page;
 192         int i, err;
 193
 194         for (i = 0; i < nr_pages; i++) {
 195                 page = find_lock_page(mapping, index + i);
 196                 BUG_ON(!page);
 197
 198                 err = mtd_write(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
 199                                 page_address(page));
 200                 unlock_page(page);
 201                 page_cache_release(page);
 202                 if (err)
 203                         return err;
 204         }
 205         return 0;
 206 }
 207
 208 static void mtd_writeseg(struct super_block *sb, u64 ofs, size_t len)
 209 {
 210         struct logfs_super *super = logfs_super(sb);
 211         int head;
 212
 213         if (super->s_flags & LOGFS_SB_FLAG_RO)
 214                 return;
 215
 216         if (len == 0) {
 217                 /* This can happen when the object fit perfectly into a
 218                  * segment, the segment gets written per sync and subsequently
 219                  * closed.
 220                  */
 221                 return;
 222         }
 223         head = ofs & (PAGE_SIZE - 1);
 224         if (head) {
 225                 ofs -= head;
 226                 len += head;
 227         }
 228         len = PAGE_ALIGN(len);
 229         __mtd_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
 230 }
 231
 232 static void mtd_put_device(struct super_block *sb)
 233 {
 234         put_mtd_device(logfs_super(sb)->s_mtd);
 235 }
 236
 237 static int mtd_can_write_buf(struct super_block *sb, u64 ofs)
 238 {
 239         struct logfs_super *super = logfs_super(sb);
 240         void *buf;
 241         int err;
 242
 243         buf = kmalloc(super->s_writesize, GFP_KERNEL);
 244         if (!buf)
 245                 return -ENOMEM;
 246         err = mtd_read(sb, ofs, super->s_writesize, buf);
 247         if (err)
 248                 goto out;
 249         if (memchr_inv(buf, 0xff, super->s_writesize))
 250                 err = -EIO;
 251         kfree(buf);
 252 out:
 253         return err;
 254 }
 255
 256 static const struct logfs_device_ops mtd_devops = {
 257         .find_first_sb  = mtd_find_first_sb,
 258         .find_last_sb   = mtd_find_last_sb,
 259         .readpage       = mtd_readpage,
 260         .writeseg       = mtd_writeseg,
 261         .erase          = mtd_erase,
 262         .can_write_buf  = mtd_can_write_buf,
 263         .sync           = mtd_sync,
 264         .put_device     = mtd_put_device,
 265 };
 266
 267 int logfs_get_sb_mtd(struct file_system_type *type, int flags,
 268                 int mtdnr, struct vfsmount *mnt)
 269 {
 270         struct mtd_info *mtd;
 271         const struct logfs_device_ops *devops = &mtd_devops;
 272
 273         mtd = get_mtd_device(NULL, mtdnr);
 274         if (IS_ERR(mtd))
 275                 return PTR_ERR(mtd);
 276         return logfs_get_sb_device(type, flags, mtd, NULL, devops, mnt);
 277 }