Date: Tue, 27 Nov 2018 17:25:35 -0800 From: Kirk McKusick <mckusick@mckusick.com> To: Warner Losh <imp@bsdimp.com> Cc: Rick Macklem <rmacklem@uoguelph.ca>, Konstantin Belousov <kostikbel@gmail.com>, FreeBSD FS <freebsd-fs@freebsd.org>, "Julian H. Stacey" <jhs@berklix.com>, "soralx@cydem.org" <soralx@cydem.org> Subject: Re: [bug] fsck refuses to repair damaged UFS using backup superblock Message-ID: <201811280125.wAS1PZAG034119@chez.mckusick.com> In-Reply-To: <CANCZdfouJC6JxTGTE9WKWrfh=McMs5mPRqKrsW9nKT7xHpYDxQ@mail.gmail.com>
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> From: Warner Losh <imp@bsdimp.com> > Date: Sun, 25 Nov 2018 12:01:45 -0700 > Subject: Re: [bug] fsck refuses to repair damaged UFS using backup super= block > To: Kirk McKusick <mckusick@mckusick.com> > Cc: Rick Macklem <rmacklem@uoguelph.ca>, FreeBSD FS <freebsd-fs@freebsd.= org>, > "Julian H. Stacey" <jhs@berklix.com>, > "soralx@cydem.org" <soralx@cydem.org> > = > On Sun, Nov 25, 2018, 11:35 AM Kirk McKusick <mckusick@mckusick.com wrot= e: > = >>> From: Rick Macklem <rmacklem@uoguelph.ca> >>> To: "soralx@cydem.org" <soralx@cydem.org>, >>> Kirk McKusick <mckusick@mckusick.com> >>> CC: "freebsd-fs@freebsd.org" <freebsd-fs@freebsd.org>, >>> "Julian H. Stacey" >>> <jhs@berklix.com> >>> Subject: Re: [bug] fsck refuses to repair damaged UFS using backup >> superblock >>> Date: Sun, 25 Nov 2018 15:25:21 +0000 >>> >>> It would be nice if there was a way to override the check and boot >>> the system. (Is a loader tunable reasonable for this?) >>> >>> rick >> >> Rather than adding a loader tunable to override the check (which people >> would have to track down in the midst of a crisis), it might be better >> to simply have the loader print a warning when there is a mismatch and >> proceed to try using the filesystem. If successful, an fsck could then >> be run to try and clean it up. Does this seem reasonable? >> >> Kirk McKusick > = > Yes. You have a big chicken and egg issue otherwise. And not booting > seems like an extreme overreaction to a bad checksum. I can think > of no use case where you'd want it. Let's let people ask for it > with a decent use case before we do anything more than print a > warning and soldier on... > = > Warner My proposal is that when a filesystem is being mounted read-only that superblock check-hash failures should be warnings only. This is true not just at boot time, but always. We should probably set the FS_NEEDSFSCK flag so that if it is updated to read-write a warning will get printed. Since booting always starts up with the filesystem in read-only mode, this should solve the booting problem. Does this seem like a sensible solution? Kirk McKusick
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