lkml.org 
[lkml]   [2020]   [May]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Subjectping; [PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly
From
Date
ping

On 2020/3/31 9:31, Xiaoming Ni wrote:
> 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@huawei.com>
> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
> drivers/mtd/mtdblock.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/mtdblock.c b/drivers/mtd/mtdblock.c
> index 078e0f6..32e52d8 100644
> --- a/drivers/mtd/mtdblock.c
> +++ b/drivers/mtd/mtdblock.c
> @@ -89,8 +89,6 @@ static int write_cached_data (struct mtdblk_dev *mtdblk)
>
> 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.
> @@ -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
> * means. Let's declare it empty and leave buffering tasks to
> * 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;
> - return 0;
> + if (ret == 0 || ret == -EIO)
> + mtdblk->cache_state = STATE_EMPTY;
> + return ret;
> }
>
>
>


\
 
 \ /
  Last update: 2020-05-07 09:54    [W:0.058 / U:0.524 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site