Date: Wed, 7 Feb 2001 15:16:47 -0800 From: Alfred Perlstein <bright@wintelcom.net> To: Greg Black <gjb@gbch.net> Cc: mouss <usebsd@free.fr>, Tony Finch <dot@dotat.at>, Andre Oppermann <oppermann@monzoon.net>, Matt Dillon <dillon@earth.backplane.com>, Rik van Riel <riel@conectiva.com.br>, Mike Silbersack <silby@silby.com>, Poul-Henning Kamp <phk@critter.freebsd.dk>, Charles Randall <crandall@matchlogic.com>, Dan Phoenix <dphoenix@bravenet.com>, Jos Backus <josb@cncdsl.com>, freebsd-hackers@FreeBSD.ORG Subject: Re: soft updates and qmail (RE: qmail IO problems) Message-ID: <20010207151647.T26076@fw.wintelcom.net> In-Reply-To: <nospam-3a81b8a9470c94a@maxim.gbch.net>; from gjb@gbch.net on Thu, Feb 08, 2001 at 07:05:45AM %2B1000 References: <20010207110208.G74296@hand.dotat.at> <Pine.LNX.4.21.0102061555550.1535-100000@duckman.distro.conectiva> <3A805035.C71AAD5E@monzoon.net> <200102061943.f16Jhp365113@earth.backplane.com> <3A805938.96ED890D@monzoon.net> <20010207110208.G74296@hand.dotat.at> <4.3.0.20010207142937.045be410@pop.free.fr> <nospam-3a81b8a9470c94a@maxim.gbch.net>
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* Greg Black <gjb@gbch.net> [010207 13:05] wrote: > mouss wrote: > > > At 21:25 07/02/01 +1000, Greg Black wrote: > > >Tony Finch wrote: > > > > > > > Why not just use rename(2)? To protect against the new filename > > > > already existing? > > > > > >Why not just read the man page for rename(2) before making > > >suggestions? > > > > I find nothing convincing in the manpage. Could you please tell > > what I am missing. > > Read the man page, and concentrate on the second sentence under > the Description heading. I'm not sure if the same problem exists for link/unlink and if the problem applies to files (not just directories), but there's a per-FS flag "in-rename" that prevents concurrant rename(2)s on the same FS to prevent a race where something like this can happen: /a/b/c /x/y/z move /a/b to /x/y and at the same time try to move /x/y to /a/b. Without a global lock you can mess up the filesystem pretty badly. I don't think link/unlink can have this problem therefore you might gain more concurrancy by avoiding rename(2). -- -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] "I have the heart of a child; I keep it in a jar on my desk." To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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