On Tue, 19 Jun 2012, Spelic wrote: > Date: Tue, 19 Jun 2012 13:29:55 +0200 > From: Spelic <spelic@xxxxxxxxxxxxx> > To: Lukáš Czerner <lczerner@xxxxxxxxxx> > Cc: Mike Snitzer <snitzer@xxxxxxxxxx>, Dave Chinner <david@xxxxxxxxxxxxx>, > Spelic <spelic@xxxxxxxxxxxxx>, > device-mapper development <dm-devel@xxxxxxxxxx>, > linux-ext4@xxxxxxxxxxxxxxx, xfs@xxxxxxxxxxx > Subject: Re: Ext4 and xfs problems in dm-thin on allocation and discard > > On 06/19/12 08:32, Lukáš Czerner wrote: > > > > So do I understand correctly that even though the discard came > > through and thinp took advantage of it it still returns EOPNOTSUPP ? > > This seems rather suboptimal. IIRC there was a discussion to add an > > option to enable/disable sending discard in thinp target down > > to the device. > > I'll ask this too... > do I understand correctly that dm-thin returns EOPNOTSUPP to the filesystem > layer even though it is using the discard to unmap blocks, and at that point > XFS stops sending discards down there (while ext4 keeps sending them)? > > This looks like a bug of dm-thin to me. Discards are "supported" in such a > scenario. > > Do you have a patch for dm-thin so to prevent it sending EOPTNOTSUPP ? Yes, definitely this behaviour need to change in dm-thin. I do not have a path, it was merely a proposal how thing could be done. Not sure what Mike and rest of the dm folks think about this. -Lukas > > Thank you > S. >
