// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Direct MTD block device access
*
* Copyright © 1999-2010 David Woodhouse <dwmw2@infradead.org>
* Copyright © 2000-2003 Nicolas Pitre <nico@fluxnic.net>
*/
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/vmalloc.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/blktrans.h>
#include <linux/mutex.h>
#include <linux/major.h>
struct mtdblk_dev {
struct mtd_blktrans_dev mbd;
int count;
struct mutex cache_mutex;
unsigned char *cache_data;
unsigned long cache_offset;
unsigned int cache_size;
enum { STATE_EMPTY, STATE_CLEAN, STATE_DIRTY } cache_state;
};
/*
* Cache stuff...
*
* Since typical flash erasable sectors are much larger than what Linux's
* buffer cache can handle, we must implement read-modify-write on flash
* sectors for each block write requests. To avoid over-erasing flash sectors
* and to speed things up, we locally cache a whole flash sector while it is
* being written to until a different sector is required.
*/
static int erase_write (struct mtd_info *mtd, unsigned long pos,
unsigned int len, const char *buf)
{
struct erase_info erase;
size_t retlen;
int ret;
/*
* First, let's erase the flash block.
*/
erase.addr = pos;
erase.len = len;
ret = mtd_erase(mtd, &erase);
if (ret) {
printk (KERN_WARNING "mtdblock: erase of region [0x%lx, 0x%x] er=%d"
"on \"%s\" failed\n",
pos, len, ret,mtd->name);
return ret;
}
/*
* Next, write the data to flash.
*/
ret = mtd_write(mtd, pos, len, &retlen, buf);
if (ret)
return ret;
if (retlen != len)
return -EIO;
return 0;
}
static int write_cached_data (struct mtdblk_dev *mtdblk)
{
struct mtd_info *mtd = mtdblk->mbd.mtd;
int ret;
if (mtdblk->cache_state != STATE_DIRTY)
return 0;
pr_debug("mtdblock: writing cached data for \"%s\" "
"at 0x%lx, size 0x%x\n", mtd->name,
mtdblk->cache_offset, mtdblk->cache_size);
ret = erase_write (mtd, mtdblk->cache_offset,
mtdblk->cache_size, mtdblk->cache_data);
if (ret)
return ret;
/*
* Here we could arguably set the cache state to STATE_CLEAN.
* However this could lead to inconsistency since we will not
* be notified if this content is altered on the flash by other
* means. Let's declare it empty and leave buffering tasks to
* the buffer cache instead.
*/
mtdblk->cache_state = STATE_EMPTY;
return 0;
}
static int do_cached_write (struct mtdblk_dev *mtdblk, unsigned long pos,
int len, const char *buf)
{
struct mtd_info *mtd = mtdblk->mbd.mtd;
unsigned int sect_size = mtdblk->cache_size;
size_t retlen;
int ret;
pr_debug("mtdblock: write on \"%s\" at 0x%lx, size 0x%x\n",
mtd->name, pos, len);
if (!sect_size)
return mtd_write(mtd, pos, len, &retlen, buf);
while (len > 0) {
unsigned long sect_start = (pos/sect_size)*sect_size;
unsigned int offset = pos - sect_start;
unsigned int size = sect_size - offset;
if( size > len )
size = len;
if (size == sect_size) {
/*
* We are covering a whole sector. Thus there is no
* need to bother with the cache while it may still be
* useful for other partial writes.
*/
ret = erase_write (mtd, pos, size, buf);
if (ret)
return ret;
} else {
/* Partial sector: need to use the cache */
if (mtdblk->cache_state == STATE_DIRTY &&
mtdblk->cache_offset != sect_start) {
ret = write_cached_data(mtdblk);
if (ret)
return ret;
}
if (mtdblk->cache_state == STATE_EMPTY ||
mtdblk->cache_offset != sect_start) {
/* fill the cache with the current sector */
mtdblk->cache_state = STATE_EMPTY;
ret = mtd_read(mtd, sect_start, sect_size,
&retlen, mtdblk->cache_data);
if (ret && !mtd_is_bitflip(ret))
return ret;
if (retlen != sect_size)
return -EIO;
mtdblk->cache_offset = sect_start;
mtdblk->cache_size = sect_size;
mtdblk->cache_state = STATE_CLEAN;
}
/* write data to our local cache */
memcpy (mtdblk->cache_data + offset, buf, size);
mtdblk->cache_state = STATE_DIRTY;
}
buf += size;
pos += size;
len -= size;
}
return 0;
}
static int do_cached_read (struct mtdblk_dev *mtdblk, unsigned long pos,
int len, char *buf)
{
struct mtd_info *mtd = mtdblk->mbd.mtd;
unsigned int sect_size = mtdblk->cache_size;
size_t retlen;
int ret;
pr_debug("mtdblock: read on \"%s\" at 0x%lx, size 0x%x\n",
mtd->name, pos, len);
if (!sect_size) {
ret = mtd_read(mtd, pos, len, &retlen, buf);
if (ret && !mtd_is_bitflip(ret))
return ret;
return 0;
}
while (len > 0) {
unsigned long sect_start = (pos/sect_size)*sect_size;
unsigned int offset = pos - sect_start;
unsigned int size = sect_size - offset;
if (size > len)
size = len;
/*
* Check if the requested data is already cached
* Read the requested amount of data from our internal cache if it
* contains what we want, otherwise we read the data directly
* from flash.
*/
if (mtdblk->cache_state != STATE_EMPTY &&
mtdblk->cache_offset == sect_start) {
memcpy (buf, mtdblk->cache_data + offset, size);
} else {
ret = mtd_read(mtd, pos, size, &retlen, buf);
if (ret && !mtd_is_bitflip(ret))
return ret;
if (retlen != size)
return -EIO;
}
buf += size;
pos += size;
len -= size;
}
return 0;
}
static int mtdblock_readsect(struct mtd_blktrans_dev *dev,
unsigned long block, char *buf)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
return do_cached_read(mtdblk, block<<9, 512, buf);
}
static int mtdblock_writesect(struct mtd_blktrans_dev *dev,
unsigned long block, char *buf)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
if (unlikely(!mtdblk->cache_data && mtdblk->cache_size)) {
mtdblk->cache_data = vmalloc(mtdblk->mbd.mtd->erasesize);
if (!mtdblk->cache_data)
return -EINTR;
/* -EINTR is not really correct, but it is the best match
* documented in man 2 write for all cases. We could also
* return -EAGAIN sometimes, but why bother?
*/
}
return do_cached_write(mtdblk, block<<9, 512, buf);
}
static int mtdblock_open(struct mtd_blktrans_dev *mbd)
{
struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
pr_debug("mtdblock_open\n");
if (mtdblk->count) {
mtdblk->count++;
return 0;
}
/* OK, it's not open. Create cache info for it */
mtdblk->count = 1;
mutex_init(&mtdblk->cache_mutex);
mtdblk->cache_state = STATE_EMPTY;
if (!(mbd->mtd->flags & MTD_NO_ERASE) && mbd->mtd->erasesize) {
mtdblk->cache_size = mbd->mtd->erasesize;
mtdblk->cache_data = NULL;
}
pr_debug("ok\n");
return 0;
}
static void mtdblock_release(struct mtd_blktrans_dev *mbd)
{
struct mtdblk_dev *mtdblk = container_of(mbd, struct mtdblk_dev, mbd);
pr_debug("mtdblock_release\n");
mutex_lock(&mtdblk->cache_mutex);
write_cached_data(mtdblk);
mutex_unlock(&mtdblk->cache_mutex);
if (!--mtdblk->count) {
/*
* It was the last usage. Free the cache, but only sync if
* opened for writing.
*/
if (mbd->file_mode & FMODE_WRITE)
mtd_sync(mbd->mtd);
vfree(mtdblk->cache_data);
}
pr_debug("ok\n");
}
static int mtdblock_flush(struct mtd_blktrans_dev *dev)
{
struct mtdblk_dev *mtdblk = container_of(dev, struct mtdblk_dev, mbd);
mutex_lock(&mtdblk->cache_mutex);
write_cached_data(mtdblk);
mutex_unlock(&mtdblk->cache_mutex);
mtd_sync(dev->mtd);
return 0;
}
static void mtdblock_add_mtd(struct mtd_blktrans_ops *tr, struct mtd_info *mtd)
{
struct mtdblk_dev *dev = kzalloc(sizeof(*dev), GFP_KERNEL);
if (!dev)
return;
dev->mbd.mtd = mtd;
dev->mbd.devnum = mtd->index;
dev->mbd.size = mtd->size >> 9;
dev->mbd.tr = tr;
if (!(mtd->flags & MTD_WRITEABLE))
dev->mbd.readonly = 1;
if (add_mtd_blktrans_dev(&dev->mbd))
kfree(dev);
}
static void mtdblock_remove_dev(struct mtd_blktrans_dev *dev)
{
del_mtd_blktrans_dev(dev);
}
static struct mtd_blktrans_ops mtdblock_tr = {
.name = "mtdblock",
.major = MTD_BLOCK_MAJOR,
.part_bits = 0,
.blksize = 512,
.open = mtdblock_open,
.flush = mtdblock_flush,
.release = mtdblock_release,
.readsect = mtdblock_readsect,
.writesect = mtdblock_writesect,
.add_mtd = mtdblock_add_mtd,
.remove_dev = mtdblock_remove_dev,
.owner = THIS_MODULE,
};
static int __init init_mtdblock(void)
{
return register_mtd_blktrans(&mtdblock_tr);
}
static void __exit cleanup_mtdblock(void)
{
deregister_mtd_blktrans(&mtdblock_tr);
}
module_init(init_mtdblock);
module_exit(cleanup_mtdblock);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Nicolas Pitre <nico@fluxnic.net> et al.");
MODULE_DESCRIPTION("Caching read/erase/writeback block device emulation access to MTD devices");erase_write 这个在业务逻辑上是否存在逻辑BUG，该函数执行了nand 的erase 和 write ,在erase之前会先检测该地址是否为坏块，为坏块了则返回错误，即擦写都失败。既然nand是存在坏块的可能的，那么擦地址和写地址应该自动偏移，跳过坏块才对。
离线
不存在逻辑bug。因为函数参数指定了写入的位置，如果函数内部私自移开写位置，则为违抗指令。返回值很难描述变通行为的细节。
坏块，不就应该跳过吗？不跳过，指令就执行不下去了。
离线
我是用mkfs.ext4格式化始终报错,我把overlayfs分区改小了，然后正常了
# mkfs.ext4 /dev/mtdblock7
mke2fs 1.47.0 (5-Feb-2023)
Creating filesystem with 89984 1k blocks and 22528 inodes
Filesystem UUID: bb8c5630-6d33-4e10-9730-50693acf846e
Superblock backups stored on blocks:
[ 109.076672] nand: nand_erase_nand: attempt to erase a bad block at page 0x0000ffc0
Allocating group tables: done
[ 109.087194] mtdblock: erase of region [0x57c0000, 0x20000] on "overlayfs_a" failed
Writing inode tables:
[ 109.100275] blk_update_request: I/O error, dev mtdblock7, sector 562 op 0x1:(WRITE) flags 0x800 phys_seg 1 prio class 0
done
[ 109.122311] nand: nand_erase_nand: attempt to erase a bad block at page 0x0000ffc0
[ 109.129919] mtdblock: erase of region [0x57c0000, 0x20000] on "overlayfs_a" failed
[ 109.137513] blk_update_request: I/O error, dev mtdblock7, sector 11852 op 0x1:(WRITE) flags 0x800 phys_seg 1 prio class 0
Creating journal (4096 blocks): [ 109.240616] nand: nand_erase_nand: attempt to erase a bad block atpage 0x0000ffc0
[ 109.250679] mtdblock: erase of region [0x57c0000, 0x20000] on "overlayfs_a" failed
[ 109.258263] blk_update_request: I/O error, dev mtdblock7, sector 65538 op 0x1:(WRITE) flags 0x4000phys_seg 32 prio class 0
[ 109.269429] nand: nand_erase_nand: attempt to erase a bad block at page 0x0000ffc0
[ 109.277005] mtdblock: erase of region [0x57c0000, 0x20000] on "overlayfs_a" failed
[ 109.284573] blk_update_request: I/O error, dev mtdblock7, sector 65546 op 0x1:(WRITE) flags 0x4000phys_seg 31 prio class 0
[ 109.295726] nand: nand_erase_nand: attempt to erase a bad block at page 0x0000ffc0
[ 109.303286] mtdblock: erase of region [0x57c0000, 0x20000] on "overlayfs_a" failed离线