kernel/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 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
  35 static 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  */
  67 static void logfs_erase_callback(struct erase_info *ei)
  68 {
  69         complete((struct completion *)ei->priv);
  70 }
  71
  72 static 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
  90 static 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
 118 static 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
 125 static 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
 148 static 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
 165 static 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
 183 static 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
 205 static 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
 229 static void logfs_mtd_put_device(struct logfs_super *s)
 230 {
 231         put_mtd_device(s->s_mtd);
 232 }
 233
 234 static 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);
 249 out:
 250         return err;
 251 }
 252
 253 static 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
 264 int 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 }