Date: Wed, 07 Aug 2019 16:01:25 -0000 From: Kirk McKusick <mckusick@mckusick.com> To: "Poul-Henning Kamp" <phk@phk.freebsd.dk> Cc: Enji Cooper <yaneurabeya@gmail.com>, "O. Hartmann" <ohartmann@walstatt.org>, freebsd-current <freebsd-current@freebsd.org> Subject: Re: CURRENT: supeblock hash failure - CURRENT wrecking disks Message-ID: <201908071610.x77GAGDO043785@chez.mckusick.com> In-Reply-To: <42457.1565182943@critter.freebsd.dk>
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> To: Enji Cooper <yaneurabeya@gmail.com> > cc: "O. Hartmann" <ohartmann@walstatt.org>, > freebsd-current <freebsd-current@freebsd.org>, mckusick@mckusick= .com > Subject: Re: CURRENT: supeblock hash failure - CURRENT wrecking disks > From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> > -------- > In message <39FB31E6-A8EC-484C-B297-39C19A787E44@gmail.com>, Enji Cooper= writes > : > = > There is an "interesting" failure-mechanism when you move a disk > between 13/current and older systems which do not support ufs-hashes. > = > It will be prudent to make 11 and 12 clear the "use hashes" flags > in the superblocks of all filesystems they mount R/W, to limit > the amount havoc this will cause when people start playing with 13. > = > -- = > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > phk@FreeBSD.ORG | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe = > Never attribute to malice what can adequately be explained by incompeten= ce. Both stable-11 and stable-12 clear the "use hashes" flags. If the disk is moved back to a 13-head system they remain disabled until reenabled by running fsck in interactive mode and requesting that they be enabled. Kirk McKusick
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