Re: A sector-of-mismatch warning patch (was Re: Fault tolerance with badblocks)

[Nix <nix@esperi.org.uk>]

[getting back to this...]

On 19 May 2017, Shaohua Li told this:
> On Fri, May 19, 2017 at 11:31:23AM +0100, Nix wrote:
>> On 19 May 2017, NeilBrown verbalised:
>> >               we'd probably make the list of inconsistencies appear in a
>> > sysfs file.  That would be less 'crappy'.  But as I say, I don't think
>> > we really want to do that.
>> 
>> Aren't sysfs files in effect length-limited to one page (or at least
>> length-limited by virtue of being stored in memory?) It seems to me this
>> would just bring the same problem ratelimit is solving right back again,
>> except a sysfs file doesn't have a logging daemon sucking the contents
>> out constantly so you can overwrite your old output without worrying.
>> (And there is no other daemon running to do that, except mdadm in
>> monitor mode, which might not be running and really this job feels out
>> of scope for it anyway.)
>
> No, my question is not the print is ratelimited. The problem is dmesg isn't a
> good way to communicate info to userspace. You can easily lose all dmesg info
> with a simple 'dmesg -c'. sysfs file is more reliable. Length-limited isn't a
> problem, as you said, if there are a lot of mismatch, the array is toast.

I agree that in future having a mechanism for reporting this more easily
usable by programs would be good, and sysfs does seem like just such a
mechanism.

-- 
NULL && (void)