Date: Thu, 21 Apr 2011 11:03:30 +0400 From: Alex Zimnitsky <aavzz@yandex.ru> To: Daichi GOTO <daichi@freebsd.org> Cc: freebsd-fs@freebsd.org, freebsd-current@freebsd.org Subject: Re: RFC: unionfs multiple mounts, cross mounts and recursive mounts limits and manegement feature Message-ID: <1303369410.2152.21.camel@localhost> In-Reply-To: <20110421144947.b887081e.daichi@freebsd.org> References: <20110421144947.b887081e.daichi@freebsd.org>
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On Thu, 2011-04-21 at 14:49 +0900, Daichi GOTO wrote: > It is adjustable with sysctl value 'vfs.unionfs.recursive_limit' as > multiple mounts limits. The default value is 1 and it means two-layered ok. > Max value of 'vfs.unionfs.recursive_limit' is 8, it is heuristic value. > I couldn't get a system panic unless 'vfs.unionfs.recursive_limit' is over 8. > Hmm, 8 is not enough for me, i need more :) On the other hand, why do we need recursion in unionfs_statfs at all? IMHO recursion in kernel is evil because it has a potencial of resource exhaustion. This recursion in unionfs_statfs is used to gather statistic (some of which is faked according to comments in the procedure) why not replace recursion with cycle? (I'm not skilled enough do do that :) and a feature request: it would be great if it was possible to umount one of multiple unionfs: mount -t unionfs /var/ftpdata1 /var/ftp mount -t unionfs /var/ftpdata2 /var/ftp how to unmount /var/ftpdata1 only?
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