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Date: Wed, 23 Nov 2016 03:40:04 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Omar Sandoval <osandov@osandov.com>
Cc: linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
        kernel-team@fb.com, Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH 2/3] vfs: add d_replace()
Message-ID: <20161123034004.GK1555@ZenIV.linux.org.uk>
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On Tue, Nov 22, 2016 at 12:25:02AM -0800, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> Changes the inode associated with a dentry. This'll be useful for
> implementations of linkat() AT_REPLACE.

Hard NAK.  That violates all kinds of assumptions made by VFS and
filesystems alike; never, ever do that.  If you have a reference to
a positive dentry, inode should *NEVER* change.

If it unhashed the old dentry, created a new one and attached inode to
it, it _might_ have a chance.  I'm less than sure it's a good idea, but
it this form it's a non-starter.

Again,

NAKed-by: Al Viro <viro@zeniv.linux.org.uk>

and don't bring it back in that form.