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

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Date:   Mon, 30 Mar 2020 22:25:36 +0800
From:   Xiaoming Ni <nixiaoming@...wei.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
CC:     <richard@....at>, <vigneshr@...com>, <gregkh@...uxfoundation.org>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <wangle6@...wei.com>, <zhangweimin12@...wei.com>,
        <yebin10@...wei.com>, <houtao1@...wei.com>, <stable@...nel.org>
Subject: Re: [PATCH v3] mtd:fix cache_state to avoid writing to bad blocks
 repeatedly

On 2020/3/30 21:52, Miquel Raynal wrote:
> Hi Xiaoming,
> 
> Xiaoming Ni <nixiaoming@...wei.com> 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@...wei.com>
>> Reviewed-by: Miquel Raynal <miquel.raynal@...tlin.com>
>> Cc: stable@...r.kernel.org
> 
> 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