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@xxxxxxxxxx>
> > Reviewed-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> > ---
> >   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@xxxxxxxxxxx> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Richard Weinberger <richard@xxxxxx> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> Vignesh Raghavendra <vigneshr@xxxxxx> (maintainer:MEMORY TECHNOLOGY DEVICES (MTD))
> linux-mtd@xxxxxxxxxxxxxxxxxxx (open list:MEMORY TECHNOLOGY DEVICES (MTD))
> linux-kernel@xxxxxxxxxxxxxxx (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@xxxxxxxxxxxxxxx and emailed you,
At v4, Cc: stable@xxxxxxxxxxxxxxx was deleted, but forgot to remove you 
from the recipient list
I'm very sorry to bother you
Thanks
Xiaoming Ni