Re: [PATCH V2] Btrfs: disable online scrub repair on ro cases

[David Sterba <dsterba@suse.cz>]

On Mon, Dec 07, 2015 at 10:26:05AM -0800, Liu Bo wrote:
> On Mon, Dec 07, 2015 at 03:37:43PM +0100, David Sterba wrote:
> > On Fri, Dec 04, 2015 at 09:58:04AM -0800, Liu Bo wrote:
> > > This disables repair process on ro cases as it can cause system
> > > to be unresponsive on the ASSERT() in repair_io_failure().
> > > 
> > > This can happen when scrub is running and a hardware error pops up,
> > > we should fallback to ro mounts gracefully instead of being unresponsive.
> > 
> > So this will also report the error as uncorrectable. This might be a bit
> > misleading, if a device error happens first and then some potentially
> > corectable errors are detected. This could be accounted as 'unverified'
> > error, that has closet maning.
> 
> Make sense, we can do
> if (ret < 0 && ret == -EROFS)
> 	spin_lock();
> 	unverified++;
> 	spin_unlock()
> 
> However, in scrub_fixup_nodatasum() all errors including ENOMEM of path
> allocation and failure of trans are interpreted to 'uncorrectable', So I
> wander it means this 'uncorrectable' is only valid in this scrub process?

I'm not sure we have a proper definition of the various stats. My user
expectation is that 'uncorrectable' refers to permament errors, so we
should try to match the type of error everywhere.