Date: Tue, 02 Sep 2003 00:58:40 -0600 From: Scott Long <scottl@freebsd.org> To: Doug Barton <DougB@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: swapon vs savecore dilemma Message-ID: <3F543FA0.7020801@freebsd.org> In-Reply-To: <20030901233731.U6074@znfgre.qbhto.arg> References: <41076.1062480964@critter.freebsd.dk> <20030901233731.U6074@znfgre.qbhto.arg>
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Doug Barton wrote: > On Tue, 2 Sep 2003, Poul-Henning Kamp wrote: > > >>Hmm, that was an unfortunate side effect. > > > Heh, well, stuff happens. I think your idea of opening swap exclusive is > probably a good one, but it will require some gymnastics to accomodate > it. One thing that'd really help is an option to savecore that tells us > if there is a dump to deal with or not. If I had that, we could do > something like this in /etc/rc.d/savecore > > if there is no dump > exit > else > does fsck -p of the fs to write the dump to succeed? > mount it rw > write the dump > clear the dump > exit > else > does try fsck -y of the fs without swap succeed? > mount, write, clear, exit > else > ??? > > At the ??? point I'm not sure how best to proceed, since if we swapon to > the same partition with the dump, it's likely to corrupt the dump, yes? > On the other hand, we're doing swapon before savecore now, so I guess > I'm curious about how dangerous this really is. > > Probably the right thing to do is to swapon, fsck -y, and if it succeeds > then swapoff, and try writing the dump anyway. I just want to be > sure before we start re-writing rc.d/savecore. > > So, the first question is does the pseudocode above look reasonable, and > the second question is what's the likelihood of getting an option to > savecore to detect a dump to play with? > > Doug > I still think that the real problem is in running swapon before savecore. In 99% of the cases out there, RAM scales with storage, so I really can't imaging fsck needing to swap, and certainly not in it's 'preen-before-background' mode. Scott
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