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 <[email protected]>
Reviewed-by: Miquel Raynal <[email protected]>
---
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
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 <[email protected]>
> Reviewed-by: Miquel Raynal <[email protected]>
> ---
> drivers/mtd/mtdblock.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
$ ./scripts/get_maintainer.pl --file drivers/mtd/mtdblock.c
Miquel Raynal <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
Richard Weinberger <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
Vignesh Raghavendra <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
[email protected] (open list:MEMORY TECHNOLOGY DEVICES (MTD))
[email protected] (open list)
No where on there is my name/email, so why am I getting these?
confused,
greg k-h
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 <[email protected]>
>> Reviewed-by: Miquel Raynal <[email protected]>
>> ---
>> drivers/mtd/mtdblock.c | 11 +++++++----
>> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> $ ./scripts/get_maintainer.pl --file drivers/mtd/mtdblock.c
> Miquel Raynal <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Richard Weinberger <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Vignesh Raghavendra <[email protected]> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> [email protected] (open list:MEMORY TECHNOLOGY DEVICES (MTD))
> [email protected] (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: [email protected] and emailed you,
At v4, Cc: [email protected] was deleted, but forgot to remove you
from the recipient list
I'm very sorry to bother you
Thanks
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 <[email protected]>
> Reviewed-by: Miquel Raynal <[email protected]>
> ---
> 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;
> }
>
>
>