On Tue, Jun 30, 2009 at 01:37:17PM -0400, Christoph Hellwig wrote: > On Fri, Jun 26, 2009 at 10:42:25AM +0200, Nick Piggin wrote: > > Yes well we could get rid of ->truncate and have filesystems do it > > themselves in setattr, but I figure that moving truncate into > > generic setattr is helpful (makes conversions a bit easier too). > > Did you see my patch? What do you think of that basic approach? > > I was waiting for a patch series for your for this to appear, but > noticed that you actually had a small proof of concept patch attached, > sorry :) No problem. I'm going to send out a patchset, I've just been working on exploring different ideas and trying to work out bugs. > Looking at your patch I really like that vmtruncate now really just > does what it's name claims to - truncate the VM-information about > the file (well, and the file size). I'm not so happy about > still keeping the two level setattr/truncate indirection. In my patch series, i_size update eventually is moved out to the filesystem too, and vmtruncate just is renamed to truncate_pagecache (vmtruncate is not such a bad name, but rename will nicely break unconverted modules). > But instead of folding truncate into setattr I wonder if we should > just add a new ->setsize (aka new trunacte) methodas a top-level > entry point instead of ->setattr with ATTR_SIZE given that size > changes don't have much in common with the reset of ->setattr. OK that would be possible and makes sense I guess. The new truncate which returns error could basically be renamed in-place. Shall we continue to give ATTR_SIZE to setattr, or take that out completely? I guess truncate can be considered special because it operates on data not only metadata. Looks like ->setsize would need a flag for ATTR_OPEN too? Any others? I'll do a bit of an audit when I get around to it... > The only bit shared is updating c/mtime and even that is conditional. > So I'd say take most of your patch, but instead of doing an all at > once migration migrate filesystems to the new ->setsize callback > incrementally and eventually kill off the old code. This means > we'll need a new name for the new vmtruncate-lite but should otherwise > be pretty easy. Makes sense. I'll try to structure it to allow incremental changeover. > > > The only problem is the generic aops calling > > > vmtruncate directly. > > > > What should be done is require that filesystems trim blocks past > > i_size in case of any errors. I actually need to fix up a few > > existing bugs in this area too, so I'll look at this.. > > Basically we want ->setattr with ATTR_SIZE, execept that we already > have i_sem and possibly other per-inode locks. Take a look at > > http://oss.sgi.com/archives/xfs/2008-04/msg00542.html > > and > > http://oss.sgi.com/archives/xfs/2009-03/msg00214.html OK thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
