LXR linux/fs/logfs/dev

   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 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
  34static 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 exercise in futility!
  64 */
  65static void logfs_erase_callback(struct erase_info *ei)
  66{
  67        complete((struct completion *)ei->priv);
  68}
  69
  70static 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
  87static 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
 115static 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
 123static 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
 146static 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
 166static 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
 187static 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
 209static 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
 233static void mtd_put_device(struct logfs_super *s)
 234{
 235        put_mtd_device(s->s_mtd);
 236}
 237
 238static 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);
 253out:
 254        return err;
 255}
 256
 257static 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
 268int 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}
 279