diff mbox series

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

Message ID 1585575925-84017-1-git-send-email-nixiaoming@huawei.com
State Changes Requested
Headers show
Series [v3] mtd:fix cache_state to avoid writing to bad blocks repeatedly | expand

Commit Message

Xiaoming Ni March 30, 2020, 1:45 p.m. UTC 
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>
Cc: stable@vger.kernel.org
---
 drivers/mtd/mtdblock.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Miquel Raynal March 30, 2020, 1:52 p.m. UTC | #1 
Hi Xiaoming,

Xiaoming Ni <nixiaoming@huawei.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@huawei.com>
> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> Cc: stable@vger.kernel.org

Still missing:
* Fixes: tag
* Wrong title prefix
Xiaoming Ni March 30, 2020, 2:25 p.m. UTC | #2 
On 2020/3/30 21:52, Miquel Raynal wrote:
> Hi Xiaoming,
> 
> Xiaoming Ni <nixiaoming@huawei.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@huawei.com>
>> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
>> Cc: stable@vger.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
Miquel Raynal March 30, 2020, 2:55 p.m. UTC | #3 
Hi Xiaoming,

Xiaoming Ni <nixiaoming@huawei.com> wrote on Mon, 30 Mar 2020 22:25:36
+0800:

> On 2020/3/30 21:52, Miquel Raynal wrote:
> > Hi Xiaoming,
> > 
> > Xiaoming Ni <nixiaoming@huawei.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@huawei.com>
> >> Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
> >> Cc: stable@vger.kernel.org  
> > 
> > Still missing:
> > * Fixes: tag
> > * Wrong title prefix
> >   
> 
> Fixes: 	1da177e4c3f41524e88 "Linux-2.6.12-rc2"
> 
> Is it described like this?

The way to describe a commit is:

Fixes: 1da177e4c3f4 ("Linux-...")

But it is too old to be pointed, just drop both Fixes/Cc tags and just
fix the title please.

> 
> 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
> 
> 
> 
> 

Thanks,
Miquèl
diff mbox series

Patch

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;
 }