From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ric Wheeler Subject: Re: openat(..., AT_UNLINKED) was Re: New copyfile system call - discuss before LSF? Date: Sun, 31 Mar 2013 19:28:40 -0400 Message-ID: <5158C6A8.9020505@redhat.com> References: <20130330194933.GB1005@amd.pavel.ucw.cz> <08D26E22-3856-43A4-8835-48C86CC5F71C@dilger.ca> <20130330214509.GB4322@amd.pavel.ucw.cz> <925D663D-D8F8-4297-A642-33C732354701@netapp.com> <20130331073604.GA13159@amd.pavel.ucw.cz> <1364754452.4771.10.camel@leira.trondhjem.org> <20130331183238.GA25751@amd.pavel.ucw.cz> <1364755493.4771.14.camel@leira.trondhjem.org> <20130331225022.GA31552@amd.pavel.ucw.cz> <5158C347.3090400@redhat.com> <20130331231854.GA32174@amd.pavel.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Myklebust, Trond" , Andreas Dilger , =?ISO-8859-1?Q?J=F6rn_Engel?= , Andy Lutomirski , Zach Brown , Paolo Bonzini , Linux FS Devel , "linux-kernel@vger.kernel.org" , "Chris L. Mason" , Christoph Hellwig , Alexander Viro , "Martin K. Petersen" , Hannes Reinecke , Joel Becker To: Pavel Machek Return-path: In-Reply-To: <20130331231854.GA32174@amd.pavel.ucw.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On 03/31/2013 07:18 PM, Pavel Machek wrote: > Hi! > >>>>>> Take a look at how many actively used filesystems out there that have >>>>>> some variant of sillyrename(), and explain what you want to do in those >>>>>> cases. >>>>> Well. Yes, there are non-unix filesystems around. You have to deal >>>>> with silly files on them, and this will not be different. >>>> So this would be a local POSIX filesystem only solution to a problem >>>> that has yet to be formulated? >>> Problem is "clasical create temp file then delete it" is racy. See the >>> archives. That is useful & common operation. >> Which race are you concerned with exactly? >> >> User wants to test for a file with name "foo.txt" >> >> * create "foo.txt~" (or whatever) >> * write contents into "foo.txt~" >> * rename "foo.txt~" to "foo.txt" >> >> Until rename is done, the file does not exists and is not complete. >> You will potentially have a garbage file to clean up if the program >> (or system) crashes, but that is not racy in a classic sense, right? > Well. If people rsync from you, they will start fetching incomplete > foo.txt~. Plus the garbage issue. That is not racy, just garbage (not trying to be pedantic, just trying to understand). I can see that the "~" file is annoying, but we have dealt with it for a *long* time :) Until it has the right name (on either the source or target system for rsync), it is not the file you are looking for. > >> This is more of a garbage clean up issue? > Also. Plus sometimes you want temporary "file" that is > deleted. Terminals use it for history, etc... There you would have a race, you can create a file and unlink it of course and still write to it, but you would have a potential empty file issue? Ric