Date: Wed, 14 Oct 2009 14:58:56 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Alexander Best <alexbestms@math.uni-muenster.de> Cc: freebsd-current@FreeBSD.org Subject: Re: panic when mounting device >= 2 times Message-ID: <4AD5BD00.4050700@icyb.net.ua> In-Reply-To: <permail-2009101411215080e26a0b00001bea-a_best01@message-id.uni-muenster.de> References: <permail-2009101411215080e26a0b00001bea-a_best01@message-id.uni-muenster.de>
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on 14/10/2009 14:21 Alexander Best said the following: > could somebody have a look at this PR please: > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/108968 > > this still exists in -CURRENT. This is because of serious and long-standing brokenness (probably from time of introduction of GEOM) in g_vfs_open/g_vfs_close. The essence: 1. we allow multiple concurrent read-only mounts of a device 2. but even a read-only mount mangles bufobj of device vnode 3. Bug! Trivial fix with POLA violation - prohibit concurrent RO mounts. Non-trivial fix - _somehow_ avoid changing or depending on device vnode bufobj. See this for even more evil example of this problem: http://lists.freebsd.org/pipermail/freebsd-fs/2009-February/005676.html -- Andriy Gapon
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