linux-kernel - Re: [RFC PATCH 0/7] cross rename

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Date:	Wed, 02 Oct 2013 18:58:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Miklos Szeredi <miklos@...redi.hu>
CC:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	viro@...IV.linux.org.uk, torvalds@...ux-foundation.org,
	hch@...radead.org, akpm@...ux-foundation.org, dhowells@...hat.com,
	zab@...hat.com, jack@...e.cz, tytso@....edu, mszeredi@...e.cz
Subject: Re: [RFC PATCH 0/7] cross rename

On 10/01/2013 09:00 AM, Miklos Szeredi wrote:
> This series adds a new syscall, renameat2(), which is the same as renameat() but
> with a flags argument.  Internally i_op->reaname2() is also added, which can
> later be merged with ->rename() but is kept separately for now, since this would
> just blow up this patch without helping review.
> 
> The purpose of extending rename is to add cross-rename, a symmetric variant of
> rename, which exchanges the two files.  This allows interesting things, which
> were not possible before, for example atomically replacing a directory tree with
> a symlink, etc...
> 

I would suggest it shouldn't be renameat2() but rather renameat3(), i.e.
rename file A -> B, if B exists rename B to C.  It may not be desirable
to expose the stale B in the same namespace as A, but still want it to
be possible to scavenge it.  Obviously, A=C is a valid subcase.

	-hpa


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