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

[Miquel Raynal]

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