On Wed, Nov 15, 2017 at 11:29 PM, John Baldwin <j...@freebsd.org> wrote:
> On Wednesday, November 15, 2017 10:17:27 PM Warner Losh wrote: > > On Wed, Nov 15, 2017 at 6:46 PM, Ed Maste <ema...@freebsd.org> wrote: > > > > > On 15 November 2017 at 19:36, Warner Losh <i...@bsdimp.com> wrote: > > > > > > > > On Wed, Nov 15, 2017 at 5:05 PM, Ed Maste <ema...@freebsd.org> > wrote: > > > >> > > > >> On 15 November 2017 at 13:47, Rodney W. Grimes > > > >> <free...@pdx.rh.cn85.dnsmgr.net> wrote: > > > >> >> Author: emaste > > > >> >> Date: Wed Nov 15 18:40:40 2017 > > > >> >> New Revision: 325860 > > > >> >> URL: https://svnweb.freebsd.org/changeset/base/325860 > > > >> >> > > > >> >> Log: > > > >> >> newfs: warn if newer than kernel > > > >> >> > > > >> >> Creating a UFS filesystem with a newfs newer than the running > > > kernel, > > > >> >> and then mounting that filesystem, can lead to interesting > > > failures. > > > >> >> > > > >> >> Add a safety belt to explicitly warn when newfs is newer than > the > > > >> >> running kernel. > > > >> > > > > >> > You should probably make the warning if (newer || older) as > > > >> > either is likely to have interesting side effects, as are > > > >> > mounting ufs file systems on different versions. > > > >> > > > >> Why would an older newfs cause trouble? Forward compatibility > should be > > > >> fine > > > > > > > > The only scenario that 'old' would cause problems is that if you did > a > > > newfs > > > > with a new binary on a new kernel, mounted the file system, wrote > files > > > to > > > > it, then rebooted with an old kernel, mounted the filesystem there, > > > writing > > > > new files to it, and then unmounting and running with a new kernel. > > > > > > Right, but that's not older newfs. AFAICT there's no reason at all for > > > a (newer || older) warning. > > > > > > I concur. > > > > > I'm not sure that the new safety belt is reasonable. Today it's fine, > but > > > > over time it will start producing false-positive warnings since the > real > > > > issue is just before/after the cg change, not old/new in general. > I'd be > > > > tempted to make a check against newfs being >= 1200046 while the > kernel > > > is < > > > > 1200046. There wasn't a specific bump for this change to > sys/param.h, but > > > > this version was bumped within a few hours of Kirk's change. > > > > > > Well, we don't in general support using a userland newer than the > > > running kernel, other than on a best-effort basis to facilitate > > > upgrades and development. This one is only a warning so I don't see > > > much harm in leaving it in place, and it would catch any new cases of > > > a similar nature. If such a warning was already in place we might have > > > avoided the issue where our snapshots produced checksum mismatch > > > messages. But I don't have a strong objection to a hardcoded version > > > check. > > > > > > > What would have fixed the snapshot isn't a warning that nobody will > notice. > > But rather something like the following: > > No, what would really fix the snapshot is using makefs or the host newfs > instead of the target newfs during the build. That part of the release > process is still fundamentally broken and fixing that wouldn't require > various > one-off fixes for future changes that happen to introduce compatability but > would fix the entire class of issues. > I agree with that. However, more than just FreeBSD's release process uses the newly built tools to do things, so those tools shouldn't do dangerous things when it's trivial to know not to. They are orthogonal issues, imho. Netflix's upgrade process, for example, uses the new newfs on an old kernel, mounts the filesystem and then splats new content into the filesystem. The issue is larger than our somewhat imperfect (but working) release building process. Warmer _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
