[PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly

[PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly

[Xiaoming Ni]

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;
 }
 
 
-- 
1.8.5.6


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: [PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly

[Greg KH]

On Tue, Mar 31, 2020 at 09:31:59AM +0800, 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(-)

$ ./scripts/get_maintainer.pl --file drivers/mtd/mtdblock.c
Miquel Raynal <miquel.raynal@bootlin.com> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
Richard Weinberger <richard@nod.at> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
Vignesh Raghavendra <vigneshr@ti.com> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
linux-mtd@lists.infradead.org (open list:MEMORY TECHNOLOGY DEVICES (MTD))
linux-kernel@vger.kernel.org (open list)


No where on there is my name/email, so why am I getting these?

confused,

greg k-h

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: [PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly

[Xiaoming Ni]

On 2020/3/31 18:05, Greg KH wrote:
> On Tue, Mar 31, 2020 at 09:31:59AM +0800, 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(-)
> 
> $ ./scripts/get_maintainer.pl --file drivers/mtd/mtdblock.c
> Miquel Raynal <miquel.raynal@bootlin.com> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Richard Weinberger <richard@nod.at> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Vignesh Raghavendra <vigneshr@ti.com> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> linux-mtd@lists.infradead.org (open list:MEMORY TECHNOLOGY DEVICES (MTD))
> linux-kernel@vger.kernel.org (open list)
> 
> 
> No where on there is my name/email, so why am I getting these?
> 
> confused,
> 
> greg k-h

At v3, I added Cc: stable@vger.kernel.org and emailed you,
At v4, Cc: stable@vger.kernel.org was deleted, but forgot to remove you 
from the recipient list
I'm very sorry to bother you
Thanks
Xiaoming Ni


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

ping; [PATCH v4] mtd: clear cache_state to avoid writing to bad blocks repeatedly

[Xiaoming Ni]

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;
>   }
>   
>   
> 



______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/