Re: [PATCH v2] btrfs-progs: free-space-cache: Enhance free space cache free space check

[David Sterba <dsterba@suse.cz>]

On Fri, Mar 09, 2018 at 10:06:02AM +0200, Nikolay Borisov wrote:
> >>> +		 * space cache has less free space, and both kernel just discard
> >>> +		 * such cache. But if we find some case where free space cache
> >>> +		 * has more free space, this means under certain case such
> >>> +		 * cache can be loaded and cause double allocate.
> >>> +		 *
> >>> +		 * Detect such possibility here.
> >>> +		 */
> >>> +		if (diff > 0)
> >>> +			error(
> >>> +"free space cache has more free space than block group item, this could leads to serious corruption, please contact btrfs developers");
> >>
> >> I'm not entirely happy with this message. So they will post to the
> >> mailing list saying something along the lines of "I got this message
> >> what do I do no, please help".  Better to output actionable data so that
> >> the user can post it immediately.
> > 
> > Unfortunately, this is already the situation we don't expect to see.
> > 
> > What we really need is to know this could happen, and if possible some
> > info about the situation.
> > There is not much actionable data here.
> 
> Fair enough, at the very least I think we should put information how to
> contact btrfs developers. So put the address of the mailing list, I
> don't think it's safe to assume people will be aware of it .

This should go to the manual page or help string, and reference it from
here.