Re: [PATCH v3] mtd:fix cache_state to avoid writing to bad blocks repeatedly

From: Xiaoming Ni
Date: Mon Mar 30 2020 - 10:26:11 EST


On 2020/3/30 21:52, Miquel Raynal wrote:
Hi Xiaoming,

Xiaoming Ni <nixiaoming@xxxxxxxxxx> wrote on Mon, 30 Mar 2020 21:45:25
+0800:

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: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Reviewed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx

Still missing:
* Fixes: tag
* Wrong title prefix


Fixes: 1da177e4c3f41524e88 "Linux-2.6.12-rc2"

Is it described like this?

Do I need to go to
https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git
to trace back the older commit records?

Thanks
Xiaoming Ni