linux-kernel - Re: [PATCH v4 0/3] libfs,xenfs: replace /proc/xen/xenbus with a symlink

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Message-ID: <20161028162227.GN19539@ZenIV.linux.org.uk>
Date:   Fri, 28 Oct 2016 17:22:27 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     David Vrabel <david.vrabel@...rix.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH v4 0/3] libfs,xenfs: replace /proc/xen/xenbus with a
 symlink

On Fri, Oct 28, 2016 at 04:52:36PM +0100, David Vrabel wrote:
> Using /proc/xen/xenbus can cause deadlocks on the atomic file position
> mutex since this file should behave like a character device and not a
> regular file.  This is easiest to achive by making it a symlink to the
> existing /dev/xen/xenbus device.

What.  The.  Hell?  What's wrong with simply adding
	file->f_mode &= ~FMODE_ATOMIC_POS;	/* cdev-style semantics */

in the ->open() of those files, rather than going through all those
convolutions?