linux-kernel - Re: [PATCH RFC] make reading /proc/mounts consistent

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Message-ID: <20120607022931.GB26406@jl-vm1.vm.bytemark.co.uk>
Date:	Thu, 7 Jun 2012 03:29:31 +0100
From:	Jamie Lokier <jamie@...reable.org>
To:	Vladimir Davydov <VDavydov@...allels.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] make reading /proc/mounts consistent

Vladimir Davydov wrote:
> >> This is achieved by keeping the position where a process stopped as a
> >> pointer to mount entry and resuming reading from the position. If a mount entry
> >> is removed, all processes that stopped on the entry are advanced i.e.  their
> >> position is moved to the next entry. To achieve this, all processes reading
> >> /proc/mounts are organized in a linked list.
> >> 
> >> An example of /proc/mounts inconsistency is here:
> >> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=593516
> > 
> > In the specific case of schroot I'm not convinced that you shouldn't
> > just increase the user space buffer size if you don't read everything.
> > Or to simply use mount namespaces to make unmounting unnecessary.
> 
> I agree, but there may be a lot of programs that already read
> /proc/mounts and don't care about its consistency.

I have cared about its consistency, but didn't realise it didn't
provide it.  Oops!  I will use a bigger buffer in future, thanks for
pointing it out ;-)

-- Jamie
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