Re: [PATCH 1/1] ubi: Introduce block devices for UBI volumes

[Richard Weinberger <richard@nod.at>]

Am 09.02.2014 00:15, schrieb Willy Tarreau:
> On Sun, Feb 09, 2014 at 12:13:11AM +0100, Richard Weinberger wrote:
>> Am 09.02.2014 00:01, schrieb Willy Tarreau:
>>> On Sat, Feb 08, 2014 at 11:56:02PM +0100, Richard Weinberger wrote:
>>>> Am 08.02.2014 23:51, schrieb Willy Tarreau:
>>>>> On Sat, Feb 08, 2014 at 10:37:19PM +0100, Richard Weinberger wrote:
>>>>>>> +config MTD_UBI_BLOCK_WRITE_SUPPORT
>>>>>>> +       bool "Enable write support (DANGEROUS)"
>>>>>>> +       default n
>>>>>>> +       depends on MTD_UBI_BLOCK
>>>>>>> +       select MTD_UBI_BLOCK_CACHED
>>>>>>> +       help
>>>>>>> +          This is a *very* dangerous feature. Using a regular block-oriented
>>>>>>> +          filesystem might impact heavily on a flash device wear.
>>>>>>> +          Use with extreme caution.
>>>>>>> +
>>>>>>> +          If in doubt, say "N".
>>>>>>
>>>>>> I really vote for dropping write support at all.
>>>>>
>>>>> Why ? When you put a read-only filesystem there such as squashfs, the
>>>>> only writes you'll have will be updates, and write support will be the
>>>>> only way to update the filesystem. So removing write support seriously
>>>>> impacts the usefulness of the feature itself.
>>>>
>>>> So almost everyone has to enable MTD_UBI_BLOCK_WRITE_SUPPORT?
>>>> I thought there is another way to fill the volume with data...
>>>
>>> I personally don't see the use of disabling write support on anything
>>> unless the code is broken. Better emit a warning upon first write to
>>> mention that there is limited or no wear leveling. But preventing all
>>> reasonable users from using a useful feature just to save a few ignorant
>>> from shooting themselves in the foot is non-sense in my opinion.
>>
>> As Piergiorgio wrote, one can use ubiupdatevol to update his squashfs.
>> There is simply no use case for MTD_UBI_BLOCK_WRITE_SUPPORT.
> 
> I gave an example with ext2 for the config. It's a bit excessive to
> quickly declare "there is simply no use case for $put_your_option_here",
> it just means that *you* don't have this use case, which I perfectly
> respect.

The mail with your ext2 use case arrived afterward I've sent that mail.

So you are using ext2 as config filesystem because you're facing issues with ubifs?

Thanks,
//richard