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 clocks repeatedly.
Signed-off-by: Xiaoming Ni <[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..98c25d6 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 clocks repeatedly
*/
- mtdblk->cache_state = STATE_EMPTY;
- return 0;
+ if (ret == 0 || ret == -EIO)
+ mtdblk->cache_state = STATE_EMPTY;
+ return ret;
}
--
1.8.5.6
Hi Xiaoming,
Xiaoming Ni <[email protected]> wrote on Sat, 28 Mar 2020 21:01:17
+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 clocks repeatedly.
blocks
>
> Signed-off-by: Xiaoming Ni <[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..98c25d6 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
Can you start your sentences with a capital letter please?
* If
> + * data cannot be written to the device.
> + * clear cache_state to avoid writing to bad clocks repeatedly
* Clear
And also please break your lines à 80, not 70.
> */
> - mtdblk->cache_state = STATE_EMPTY;
> - return 0;
> + if (ret == 0 || ret == -EIO)
> + mtdblk->cache_state = STATE_EMPTY;
> + return ret;
> }
>
>
Otherwise looks good to me.
With the above addressed:
Reviewed-by: Miquel Raynal <[email protected]>
Thanks,
Miquèl
Hi Xiaoming,
Xiaoming Ni <[email protected]> wrote on Sat, 28 Mar 2020 21:01:17
+0800:
Please also fix the title.
"mtd: clear ..."
Thanks,
Miquèl
On 2020/3/30 15:53, Miquel Raynal wrote:
> Hi Xiaoming,
>
> Xiaoming Ni <[email protected]> wrote on Sat, 28 Mar 2020 21:01:17
> +0800:
>
>> The function call process is as follows:
>> mtd_blktrans_work()
>> while (1)
....
>> + *
>> + * if this cache_offset points to a bad block
>
> Can you start your sentences with a capital letter please?
>
> * If
>
>> + * data cannot be written to the device.
>> + * clear cache_state to avoid writing to bad clocks repeatedly
>
> * Clear
>
> And also please break your lines à 80, not 70.
>
>> */
>> - mtdblk->cache_state = STATE_EMPTY;
>> - return 0;
>> + if (ret == 0 || ret == -EIO)
>> + mtdblk->cache_state = STATE_EMPTY;
Should I add a warning print for EIO here
>> + return ret;
>> }
>>
>>
>
> Otherwise looks good to me.
>
> With the above addressed:
>
> Reviewed-by: Miquel Raynal <[email protected]>
>
>
> Thanks,
> Miquèl
>
> .
Thanks for your advice, I will send v2 patch later
Thanks,
Xiaoming Ni
Hi Xiaoming,
Xiaoming Ni <[email protected]> wrote on Mon, 30 Mar 2020 16:44:29
+0800:
> On 2020/3/30 15:53, Miquel Raynal wrote:
> > Hi Xiaoming,
> >
> > Xiaoming Ni <[email protected]> wrote on Sat, 28 Mar 2020 21:01:17
> > +0800:
> >
> >> The function call process is as follows:
> >> mtd_blktrans_work()
> >> while (1)
> ....
>
> >> + *
> >> + * if this cache_offset points to a bad block
> >
> > Can you start your sentences with a capital letter please?
> >
> > * If
> >
> >> + * data cannot be written to the device.
> >> + * clear cache_state to avoid writing to bad clocks repeatedly
> >
> > * Clear
> >
> > And also please break your lines à 80, not 70.
> >
> >> */
> >> - mtdblk->cache_state = STATE_EMPTY;
> >> - return 0;
> >> + if (ret == 0 || ret == -EIO)
> >> + mtdblk->cache_state = STATE_EMPTY;
> Should I add a warning print for EIO here
I don't think so.
Thanks,
Miquèl