Date: Wed, 11 Jan 2012 17:36:18 -0800 (PST) From: Don Lewis <truckman@FreeBSD.org> To: jmg@funkthat.com Cc: alfred@FreeBSD.org, arch@FreeBSD.org, adrian@FreeBSD.org, nvass@gmx.com, dougb@FreeBSD.org Subject: Re: [patch] allow crash dumps to Linux swap partitions Message-ID: <201201120136.q0C1aI7i047108@gw.catspoiler.org> In-Reply-To: <20120112011301.GI52468@funkthat.com>
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On 11 Jan, John-Mark Gurney wrote: > Don Lewis wrote this message on Mon, Jan 09, 2012 at 02:09 -0800: >> On 9 Jan, Nikos Vassiliadis wrote: >> > On 1/9/2012 11:25 AM, Doug Barton wrote: >> >> Actually I'm fairly confident that we write dumps backwards from the end >> >> of the swap partition. It's done that way on purpose in case fsck'ing >> >> causes the system to swap, it may still be possible to save the dump. >> > >> > So, dumping core is safe, but not sharing the swap area... >> > It would be nice to be able to do that. >> >> According to the mkswap(8) man page (which hasn't been updated >> since 2.2 even though the machine is running a 2.6 kernel) on a nearby >> Linux machine, the metadata stored in the first page of the swap >> partition. It looks like we could safely coexist if we skipped the first >> page of the partition. Otherwise Linux will want mkswap to be run on the >> partition before it will swap to the partition. > > Don't we already skip the first 8k of the swap partition because back > in the day when bsdlabel's partition sector 0 was the same as the > slice sector 0, and so if any FS or swap wrote to the first 8k, it > would overwrite the bsdlabel? Yes, I mentioned this in a later message on this thread.
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