Commit 5788ccf3 authored by Xiaoming Ni's avatar Xiaoming Ni Committed by Richard Weinberger

mtd: clear cache_state to avoid writing to bad blocks repeatedly

The function call process is as follows:
	mtd_blktrans_work()
	  while (1)
	    do_blktrans_request()
	      mtdblock_writesect()
	        do_cached_write()
	          write_cached_data() /*if cache_state is STATE_DIRTY*/
	            erase_write()

write_cached_data() returns failure without modifying cache_state
and cache_offset. So when do_cached_write() is called again,
write_cached_data() will be called again to perform erase_write()
on the same cache_offset.

But if this cache_offset points to a bad block, erase_write() will
always return -EIO. Writing to this mtdblk is equivalent to losing
the current data, and repeatedly writing to the bad block.

Repeatedly writing a bad block has no real benefits,
but brings some negative effects:
1 Lost subsequent data
2 Loss of flash device life
3 erase_write() bad blocks are very time-consuming. For example:
	the function do_erase_oneblock() in chips/cfi_cmdset_0020.c or
	chips/cfi_cmdset_0002.c may take more than 20 seconds to return

Therefore, when erase_write() returns -EIO in write_cached_data(),
clear cache_state to avoid writing to bad blocks repeatedly.
Signed-off-by: default avatarXiaoming Ni <nixiaoming@huawei.com>
Reviewed-by: default avatarMiquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent eb13fa02
...@@ -89,8 +89,6 @@ static int write_cached_data (struct mtdblk_dev *mtdblk) ...@@ -89,8 +89,6 @@ static int write_cached_data (struct mtdblk_dev *mtdblk)
ret = erase_write (mtd, mtdblk->cache_offset, ret = erase_write (mtd, mtdblk->cache_offset,
mtdblk->cache_size, mtdblk->cache_data); mtdblk->cache_size, mtdblk->cache_data);
if (ret)
return ret;
/* /*
* Here we could arguably set the cache state to STATE_CLEAN. * Here we could arguably set the cache state to STATE_CLEAN.
...@@ -98,9 +96,14 @@ static int write_cached_data (struct mtdblk_dev *mtdblk) ...@@ -98,9 +96,14 @@ static int write_cached_data (struct mtdblk_dev *mtdblk)
* be notified if this content is altered on the flash by other * be notified if this content is altered on the flash by other
* means. Let's declare it empty and leave buffering tasks to * means. Let's declare it empty and leave buffering tasks to
* the buffer cache instead. * the buffer cache instead.
*
* If this cache_offset points to a bad block, data cannot be
* written to the device. Clear cache_state to avoid writing to
* bad blocks repeatedly.
*/ */
mtdblk->cache_state = STATE_EMPTY; if (ret == 0 || ret == -EIO)
return 0; mtdblk->cache_state = STATE_EMPTY;
return ret;
} }
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment