From mboxrd@z Thu Jan  1 00:00:00 1970
From: Zan Lynx <zlynx-HInyCGIudOg@public.gmane.org>
Subject: Re: [RFC] fs, proc: Introduce the /proc/<pid>/map_files/ directory v2
Date: Wed, 24 Aug 2011 09:05:21 -0600
Message-ID: <4E551331.1010709@acm.org>
References: <20110824085329.GL29452@sun>
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To: Cyrill Gorcunov <gorcunov-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, James Bottomley <jbottomley-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>, containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org, Nathan Lynch <ntl-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, LINUXFS-ML <linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Daniel Lezcano <dlezcano-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
List-Id: containers.vger.kernel.org

On 8/24/2011 2:53 AM, Cyrill Gorcunov wrote:
> From: Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
> 
> This one behaves similarly to the /proc/<pid>/fd/ one - it contains symlinks
> one for each mapping with file, the name of a symlink is vma->vm_start, the
> target is the file. Opening a symlink results in a file that point exactly
> to the same inode as them vma's one.
> 
> This thing is aimed to help checkpointing processes.
> 
> For example the ls -l of some arbitrary /proc/<pid>/map_files/
> 
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73a00000 -> /lib64/ld-2.5.so
[snip]

Just curious: How do these symlinks work when the process reading a
/proc file is in a chroot or a different namespace?

For example, a chroot environment might have independent copies of
/lib64/ld-2.5.so and a bind mount of /proc. Does the symlink then point
to the wrong file?

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Message-ID: <4E551331.1010709@acm.org>
Date: Wed, 24 Aug 2011 09:05:21 -0600
From: Zan Lynx <zlynx@acm.org>
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To: Cyrill Gorcunov <gorcunov@gmail.com>
CC: Nathan Lynch <ntl@pobox.com>, Oren Laadan <orenl@cs.columbia.edu>,
        Daniel Lezcano <dlezcano@fr.ibm.com>, Tejun Heo <tj@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Glauber Costa <glommer@parallels.com>, containers@lists.osdl.org,
        linux-kernel@vger.kernel.org, Pavel Emelyanov <xemul@parallels.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        LINUXFS-ML <linux-fsdevel@vger.kernel.org>,
        James Bottomley <jbottomley@parallels.com>
Subject: Re: [RFC] fs, proc: Introduce the /proc/<pid>/map_files/ directory
 v2
References: <20110824085329.GL29452@sun>
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On 8/24/2011 2:53 AM, Cyrill Gorcunov wrote:
> From: Pavel Emelyanov <xemul@parallels.com>
> 
> This one behaves similarly to the /proc/<pid>/fd/ one - it contains symlinks
> one for each mapping with file, the name of a symlink is vma->vm_start, the
> target is the file. Opening a symlink results in a file that point exactly
> to the same inode as them vma's one.
> 
> This thing is aimed to help checkpointing processes.
> 
> For example the ls -l of some arbitrary /proc/<pid>/map_files/
> 
>  | lr-x------ 1 cyrill cyrill 64 Aug  9 15:25 0x3d73a00000 -> /lib64/ld-2.5.so
[snip]

Just curious: How do these symlinks work when the process reading a
/proc file is in a chroot or a different namespace?

For example, a chroot environment might have independent copies of
/lib64/ld-2.5.so and a bind mount of /proc. Does the symlink then point
to the wrong file?