On Mon, Jul 15, 2013 at 08:25:14PM -0700, Linus Torvalds wrote: > On Mon, Jul 15, 2013 at 7:38 PM, Dave Jones <davej@xxxxxxxxxx> wrote: > > > > The recent trinity changes shouldn't have really made > > any notable difference here. > > Hmm. I'm not aware pf anything that has changed in this area since > 3.10 - neither in execve, xfs or in splice. Not even since 3.9. It's been there for years..... > The "pipe -> cred_guard_mutex" lock chain is pretty direct, and can be > clearly attributed to splicing into /proc. Now, whether that is a > *good* idea or not is clearly debatable, and I do think that maybe we > should just not splice to/from proc files, but that doesn't seem to be > new, and I don't think it's necessarily *broken* per se, it's just > that splicing into /proc seems somewhat unnecessary, and various proc > files do end up taking locks that can be "interesting". But this is a new way of triggering the inversion, however.... > At the other end of the spectrum, the "cred_guard_mutex -> FS locks" > thing from execve() is also pretty clear, and probably not fixable or > necessarily something we'd even want to fix. > > But the "FS locks -> pipe" part is a bit questionable. Honestly, I'd > be much happier if XFS used generic_file_splice_read/write(). > > And looking more at that, I'm actually starting to think this is an > XFS locking problem. XFS really should not call back to splice while > holding the inode lock. > > But that XFS code doesn't seem new either. Is XFS a new thing for you > to test with? I posted patches to fix this i_mutex/i_iolock inversion a couple of years ago (july 2011): https://lkml.org/lkml/2011/7/18/4 And V2 was posted here and reviewed (aug 2011): http://xfs.9218.n7.nabble.com/PATCH-0-2-splice-i-mutex-vs-splice-write-deadlock-V2-tt4072.html#none It didn't get picked up by with a VFS tree, so sat moldering until somebody else reported it (Nov 2012) and it reposted it again, only to have it ignored again: http://oss.sgi.com/archives/xfs/2012-11/msg00671.html And I recently discussed it again with Al w.r.t. filesystem freeze problems he was looking at, and I was waiting for that to settle down before I posted the fixes again.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
