Date: Thu, 02 Jun 2005 09:43:32 +0200 From: Alexander Leidinger <Alexander@Leidinger.net> To: Don Lewis <truckman@FreeBSD.org> Cc: phk@phk.freebsd.dk, current@FreeBSD.org Subject: Re: [RFC] [PATCH] VM & VFS changes Message-ID: <20050602094332.949xldwlwk4c8k4g@netchild.homeip.net> In-Reply-To: <200506020637.j526bqXO002547@gw.catspoiler.org> References: <200506020637.j526bqXO002547@gw.catspoiler.org>
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Don Lewis <truckman@FreeBSD.org> wrote: >>>>> Wouldn't a loop like the following be enough? >>>>> while swap >>>>> umount unbusy-FS >>>>> swap-off swap >>>>> >>>>> This assumes that swap-off doesn't turns off the swap if it isn't >>>>> able to put >>>>> everything back into other swap or physical RAM areas. > I think this can be unwound in one pass if a list of the dependency > pairs is kept and then properly sorted before processing. The types of > dependencies are: > md depends on file system (vnode backed md) > md depends on swap (swap backed file system) > file system depends on md (md backed file system) > swap depends on md (swap on an md) > file system depends on file system (mount relationship) > First undo any dependencies that ultimately depend on swap, unconfigure > the swap devices, and finally undo any dependencies that swap depended > on. I still don't understand why my approach above doesn't solve this problem. A FS is busy when something is still open. So if the FS is used as a container for swap, the FS is busy and it isn't supposed to be umounted. If a md is configured on the swap area you want to disable with swap-off, my above description allows the call to fail. Since the md/swap/FS part is cycle-free, we have an upper bound of sum(#md)+sum(#swap)+sum(#FS) iterations (actually it's less than that, but my point is: a linear number of iterations with an upper bound) of this loop. When the loop finishes, no swap is enabled anymore. -> Goal reached. What am I overlooking? Bye, Alexander. -- http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7 http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137 Hiccuping & trembling into the WASTE DUMPS of New Jersey like some drunken CABBAGE PATCH DOLL, coughing in line at FIORUCCI'S!!
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