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
  13 #define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
  14
  15 static int mtd_read(struct super_block *sb, loff_t ofs, size_t len, void *buf)
  16 {
  17         struct mtd_info *mtd = logfs_super(sb)->s_mtd;
  18         size_t retlen;
  19         int ret;
  20
  21         ret = mtd->read(mtd, ofs, len, &retlen, buf);
  22         BUG_ON(ret == -EINVAL);
  23         if (ret)
  24                 return ret;
  25
  26         /* Not sure if we should loop instead. */
  27         if (retlen != len)
  28                 return -EIO;
  29
  30         return 0;
  31 }
  32
  33 static int mtd_write(struct super_block *sb, loff_t ofs, size_t len, void *buf)
  34 {
  35         struct logfs_super *super = logfs_super(sb);
  36         struct mtd_info *mtd = super->s_mtd;
  37         size_t retlen;
  38         loff_t page_start, page_end;
  39         int ret;
  40
  41         if (super->s_flags & LOGFS_SB_FLAG_RO)
  42                 return -EROFS;
  43
  44         BUG_ON((ofs >= mtd->size) || (len > mtd->size - ofs));
  45         BUG_ON(ofs != (ofs >> super->s_writeshift) << super->s_writeshift);
  46         BUG_ON(len > PAGE_CACHE_SIZE);
  47         page_start = ofs & PAGE_CACHE_MASK;
  48         page_end = PAGE_CACHE_ALIGN(ofs + len) - 1;
  49         ret = mtd->write(mtd, ofs, len, &retlen, buf);
  50         if (ret || (retlen != len))
  51                 return -EIO;
  52
  53         return 0;
  54 }
  55
  56 /*
  57  * For as long as I can remember (since about 2001) mtd->erase has been an
  58  * asynchronous interface lacking the first driver to actually use the
  59  * asynchronous properties.  So just to prevent the first implementor of such
  60  * a thing from breaking logfs in 2350, we do the usual pointless dance to
  61  * declare a completion variable and wait for completion before returning
  62  * from mtd_erase().  What an excercise in futility!
  63  */
  64 static void logfs_erase_callback(struct erase_info *ei)
  65 {
  66         complete((struct completion *)ei->priv);
  67 }
  68
  69 static int mtd_erase_mapping(struct super_block *sb, loff_t ofs, size_t len)
  70 {
  71         struct logfs_super *super = logfs_super(sb);
  72         struct address_space *mapping = super->s_mapping_inode->i_mapping;
  73         struct page *page;
  74         pgoff_t index = ofs >> PAGE_SHIFT;
  75
  76         for (index = ofs >> PAGE_SHIFT; index < (ofs + len) >> PAGE_SHIFT; index++) {
  77                 page = find_get_page(mapping, index);
  78                 if (!page)
  79                         continue;
  80                 memset(page_address(page), 0xFF, PAGE_SIZE);
  81                 page_cache_release(page);
  82         }
  83         return 0;
  84 }
  85
  86 static int mtd_erase(struct super_block *sb, loff_t ofs, size_t len,
  87                 int ensure_write)
  88 {
  89         struct mtd_info *mtd = logfs_super(sb)->s_mtd;
  90         struct erase_info ei;
  91         DECLARE_COMPLETION_ONSTACK(complete);
  92         int ret;
  93
  94         BUG_ON(len % mtd->erasesize);
  95         if (logfs_super(sb)->s_flags & LOGFS_SB_FLAG_RO)
  96                 return -EROFS;
  97
  98         memset(&ei, 0, sizeof(ei));
  99         ei.mtd = mtd;
 100         ei.addr = ofs;
 101         ei.len = len;
 102         ei.callback = logfs_erase_callback;
 103         ei.priv = (long)&complete;
 104         ret = mtd->erase(mtd, &ei);
 105         if (ret)
 106                 return -EIO;
 107
 108         wait_for_completion(&complete);
 109         if (ei.state != MTD_ERASE_DONE)
 110                 return -EIO;
 111         return mtd_erase_mapping(sb, ofs, len);
 112 }
 113
 114 static void mtd_sync(struct super_block *sb)
 115 {
 116         struct mtd_info *mtd = logfs_super(sb)->s_mtd;
 117
 118         if (mtd->sync)
 119                 mtd->sync(mtd);
 120 }
 121
 122 static int mtd_readpage(void *_sb, struct page *page)
 123 {
 124         struct super_block *sb = _sb;
 125         int err;
 126
 127         err = mtd_read(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
 128                         page_address(page));
 129         if (err == -EUCLEAN) {
 130                 err = 0;
 131                 /* FIXME: force GC this segment */
 132         }
 133         if (err) {
 134                 ClearPageUptodate(page);
 135                 SetPageError(page);
 136         } else {
 137                 SetPageUptodate(page);
 138                 ClearPageError(page);
 139         }
 140         unlock_page(page);
 141         return err;
 142 }
 143
 144 static struct page *mtd_find_first_sb(struct super_block *sb, u64 *ofs)
 145 {
 146         struct logfs_super *super = logfs_super(sb);
 147         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 148         filler_t *filler = mtd_readpage;
 149         struct mtd_info *mtd = super->s_mtd;
 150
 151         if (!mtd->block_isbad)
 152                 return NULL;
 153
 154         *ofs = 0;
 155         while (mtd->block_isbad(mtd, *ofs)) {
 156                 *ofs += mtd->erasesize;
 157                 if (*ofs >= mtd->size)
 158                         return NULL;
 159         }
 160         BUG_ON(*ofs & ~PAGE_MASK);
 161         return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
 162 }
 163
 164 static struct page *mtd_find_last_sb(struct super_block *sb, u64 *ofs)
 165 {
 166         struct logfs_super *super = logfs_super(sb);
 167         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 168         filler_t *filler = mtd_readpage;
 169         struct mtd_info *mtd = super->s_mtd;
 170
 171         if (!mtd->block_isbad)
 172                 return NULL;
 173
 174         *ofs = mtd->size - mtd->erasesize;
 175         while (mtd->block_isbad(mtd, *ofs)) {
 176                 *ofs -= mtd->erasesize;
 177                 if (*ofs <= 0)
 178                         return NULL;
 179         }
 180         *ofs = *ofs + mtd->erasesize - 0x1000;
 181         BUG_ON(*ofs & ~PAGE_MASK);
 182         return read_cache_page(mapping, *ofs >> PAGE_SHIFT, filler, sb);
 183 }
 184
 185 static int __mtd_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
 186                 size_t nr_pages)
 187 {
 188         struct logfs_super *super = logfs_super(sb);
 189         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 190         struct page *page;
 191         int i, err;
 192
 193         for (i = 0; i < nr_pages; i++) {
 194                 page = find_lock_page(mapping, index + i);
 195                 BUG_ON(!page);
 196
 197                 err = mtd_write(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
 198                                 page_address(page));
 199                 unlock_page(page);
 200                 page_cache_release(page);
 201                 if (err)
 202                         return err;
 203         }
 204         return 0;
 205 }
 206
 207 static void mtd_writeseg(struct super_block *sb, u64 ofs, size_t len)
 208 {
 209         struct logfs_super *super = logfs_super(sb);
 210         int head;
 211
 212         if (super->s_flags & LOGFS_SB_FLAG_RO)
 213                 return;
 214
 215         if (len == 0) {
 216                 /* This can happen when the object fit perfectly into a
 217                  * segment, the segment gets written per sync and subsequently
 218                  * closed.
 219                  */
 220                 return;
 221         }
 222         head = ofs & (PAGE_SIZE - 1);
 223         if (head) {
 224                 ofs -= head;
 225                 len += head;
 226         }
 227         len = PAGE_ALIGN(len);
 228         __mtd_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
 229 }
 230
 231 static void mtd_put_device(struct super_block *sb)
 232 {
 233         put_mtd_device(logfs_super(sb)->s_mtd);
 234 }
 235
 236 static const struct logfs_device_ops mtd_devops = {
 237         .find_first_sb  = mtd_find_first_sb,
 238         .find_last_sb   = mtd_find_last_sb,
 239         .readpage       = mtd_readpage,
 240         .writeseg       = mtd_writeseg,
 241         .erase          = mtd_erase,
 242         .sync           = mtd_sync,
 243         .put_device     = mtd_put_device,
 244 };
 245
 246 int logfs_get_sb_mtd(struct file_system_type *type, int flags,
 247                 int mtdnr, struct vfsmount *mnt)
 248 {
 249         struct mtd_info *mtd;
 250         const struct logfs_device_ops *devops = &mtd_devops;
 251
 252         mtd = get_mtd_device(NULL, mtdnr);
 253         return logfs_get_sb_device(type, flags, mtd, NULL, devops, mnt);
 254 }