Date: Wed, 15 Nov 2017 22:37:24 -0700 From: Warner Losh <imp@bsdimp.com> To: Ed Maste <emaste@freebsd.org> Cc: "Rodney W. Grimes" <rgrimes@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, Kirk McKusick <mckusick@mckusick.com> Subject: Re: svn commit: r325860 - head/sbin/newfs Message-ID: <CANCZdfpHqGK4FsKa0-ZkmBLrLhR195Z5DC=RBkEs4PurvsWDJw@mail.gmail.com> In-Reply-To: <CANCZdfpxj_kRZ8BcBMXdsighwS6f=6-WNMXRvd0axfuoJuS6MA@mail.gmail.com> References: <201711151840.vAFIefKV002185@repo.freebsd.org> <201711151847.vAFIlGD9052509@pdx.rh.CN85.dnsmgr.net> <CAPyFy2BMDoA%2Bs76ddyNBYo1iC7TZq99_MNZi%2BmHFV6iAgQxgbQ@mail.gmail.com> <CANCZdfpN3Q68rxcGn75BCUwv47__=5p_=N%2BPpoqqQbnJTOb8zw@mail.gmail.com> <CAPyFy2DBB%2BrTZak8urufxqTxohKKv3%2BryxiteDugxnw-hsaS0g@mail.gmail.com> <CANCZdfpxj_kRZ8BcBMXdsighwS6f=6-WNMXRvd0axfuoJuS6MA@mail.gmail.com>
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On Wed, Nov 15, 2017 at 10:17 PM, Warner Losh <imp@bsdimp.com> wrote: > > > On Wed, Nov 15, 2017 at 6:46 PM, Ed Maste <emaste@freebsd.org> wrote: > >> On 15 November 2017 at 19:36, Warner Losh <imp@bsdimp.com> wrote: >> > >> > On Wed, Nov 15, 2017 at 5:05 PM, Ed Maste <emaste@freebsd.org> wrote: >> >> >> >> On 15 November 2017 at 13:47, Rodney W. Grimes >> >> <freebsd@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: > > diff --git a/sbin/fsck_ffs/pass5.c b/sbin/fsck_ffs/pass5.c > index 16c46bece00..06e1838a7f1 100644 > --- a/sbin/fsck_ffs/pass5.c > +++ b/sbin/fsck_ffs/pass5.c > @@ -73,6 +73,7 @@ pass5(void) > newcg->cg_niblk = fs->fs_ipg; > if (preen == 0 && yflag == 0 && fs->fs_magic == FS_UFS2_MAGIC && > fswritefd != -1 && (fs->fs_metackhash & CK_CYLGRP) == 0 && > + getosreldate() >= 1200046 && > reply("ADD CYLINDER GROUP CHECKSUM PROTECTION") != 0) { > fs->fs_metackhash |= CK_CYLGRP; > rewritecg = 1; > diff --git a/sbin/newfs/mkfs.c b/sbin/newfs/mkfs.c > index f68c42ec6b3..0e7ee539265 100644 > --- a/sbin/newfs/mkfs.c > +++ b/sbin/newfs/mkfs.c > @@ -495,7 +495,7 @@ restart: > /* > * Set flags for metadata that is being check-hashed. > */ > - if (Oflag > 1) > + if (Oflag > 1 && getosreldate() >= 1200046) > sblock.fs_metackhash = CK_CYLGRP; > > /* > > which would avoid setting the flag on a problematical kernel. Here forward > compat is easy, and the consequences are scary messages, so I think we > should do something more like the above. I don't think we need some kind of > "do it anyway" override flag. since that doesn't fit well with the rest of > UFS "works by default where we can figure it out" philosophy. > > I'll cleanup the above with a #define for 1200046. I've cc'd Kirk to see > what he thinks of the idea. It generally fits with what we've done in the > past for forward compat that's easy but protects the user from harshness. > I've gone ahead and tidied it up in https://reviews.freebsd.org/D13114 for anybody that's interested. Warner
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