linux-kernel - Re: [patch] vfs: no "(unreachable)" prefix for SYSVIPC maps in /proc/PID/maps

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Date:	Tue, 8 Sep 2009 19:04:11 +0100 (BST)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	Miklos Szeredi <miklos@...redi.hu>
cc:	akpm@...ux-foundation.org, Valdis.Kletnieks@...edu, matthew@....cx,
	agruen@...e.de, viro@...iv.linux.org.uk, hch@....de,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] vfs: no "(unreachable)" prefix for SYSVIPC maps in
 /proc/PID/maps 

On Mon, 7 Sep 2009, Miklos Szeredi wrote:
> Another fix for vfs-fix-d_path-for-unreachable-paths.patch in -mm.
> 
> ----
> From: Miklos Szeredi <mszeredi@...e.cz>
> 
> The patch
> 
>   "vfs: fix d_path() for unreachable paths"
> 
> generally changed d_path() to report unreachable paths with a special
> prefix.  This has an effect on /proc/${PID}/maps as well for memory
> maps set up with shmem_file_setup() or hugetlb_file_setup().  These
> functions set up unlinked files under a kernel-private vfsmount.
> Since this vfsmount is unreachable from userspace, these maps will be
> reported with the "(unreachable)" prefix.
> 
> This is undesirable, because it changes the kernel ABI and might break
> applications for no good reason.
> 
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> ---
>  fs/hugetlbfs/inode.c |   17 +++++++++++++++++
>  mm/shmem.c           |   17 +++++++++++++++++
>  2 files changed, 34 insertions(+)

You can add my
Acked-by: Hugh Dickins <hugh.dickins@...cali.co.uk>
to this and to the preceding two patches.

And give yourself a gold star for putting your updates into the right
section of mm/shmem.c, to cover both CONFIG_SHMEM=y and not set.

My heart sinks a little with these patches, particularly this
last; but I bet your heart sank a little to have to do them, and
I reluctantly agree with you that they're all probably necessary.
They do as you've said - I checked again with the 10.3 gnome-vfs.

Thanks,
Hugh
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