Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757059Ab3C3UIr (ORCPT ); Sat, 30 Mar 2013 16:08:47 -0400 Received: from mail-oa0-f48.google.com ([209.85.219.48]:64000 "EHLO mail-oa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756555Ab3C3UIp (ORCPT ); Sat, 30 Mar 2013 16:08:45 -0400 Subject: Re: New copyfile system call - discuss before LSF? Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: text/plain; charset=us-ascii From: Andreas Dilger In-Reply-To: <20130330194933.GB1005@amd.pavel.ucw.cz> Date: Sat, 30 Mar 2013 13:08:39 -0700 Cc: =?iso-8859-1?Q?J=F6rn_Engel?= , Andy Lutomirski , Zach Brown , "Myklebust, Trond" , Paolo Bonzini , Ric Wheeler , Linux FS Devel , "linux-kernel@vger.kernel.org" , "Chris L. Mason" , Christoph Hellwig , Alexander Viro , "Martin K. Petersen" , Hannes Reinecke , Joel Becker Content-Transfer-Encoding: 7bit Message-Id: <08D26E22-3856-43A4-8835-48C86CC5F71C@dilger.ca> References: <512606DF.5050706@redhat.com> <4FA345DA4F4AE44899BD2B03EEEC2FA9235D998C@SACEXCMBX04-PRD.hq.netapp.com> <512635D2.4090207@redhat.com> <51267CEB.8070805@redhat.com> <4FA345DA4F4AE44899BD2B03EEEC2FA9235DAA99@SACEXCMBX04-PRD.hq.netapp.com> <20130221222449.GY22221@lenny.home.zabbo.net> <512BD44C.40907@amacapital.net> <20130226210232.GA19510@logfs.org> <20130330194933.GB1005@amd.pavel.ucw.cz> To: Pavel Machek X-Mailer: Apple Mail (2.1085) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1157 Lines: 29 On 2013-03-30, at 12:49 PM, Pavel Machek wrote: > Hmm, really? AFAICT it would be simple to provide an > open_deleted_file("directory") syscall. You'd open_deleted_file(), > copy source file into it, then fsync(), then link it into filesystem. > > That should have atomicity properties reflected. Actually, the open_deleted_file() syscall is quite useful for many different things all by itself. Lots of applications need to create temporary files that are unlinked at application failure (without a race if app crashes after creating the file, but before unlinking). It also avoids exposing temporary files into the namespace if other applications are accessing the directory. We've added a library routine that does this for Lustre in a hackish way (magical filename created in target directory) for being able to migrate files between data servers, HSM, defragmentation, rsync, etc. Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/