Date: Tue, 6 Feb 2001 11:52:10 -0600 (CST) From: Mike Silbersack <silby@silby.com> To: Rik van Riel <riel@conectiva.com.br> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, Charles Randall <crandall@matchlogic.com>, 'Matt Dillon' <dillon@earth.backplane.com>, Dan Phoenix <dphoenix@bravenet.com>, Alfred Perlstein <bright@wintelcom.net>, Jos Backus <josb@cncdsl.com>, <freebsd-hackers@FreeBSD.ORG> Subject: Re: soft updates and qmail (RE: qmail IO problems) Message-ID: <Pine.BSF.4.31.0102061149180.14899-100000@achilles.silby.com> In-Reply-To: <Pine.LNX.4.21.0102061538290.1535-100000@duckman.distro.conectiva>
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On Tue, 6 Feb 2001, Rik van Riel wrote: > The system call used to guarantee this is fsync (and friends?); > if qmail doesn't use it but makes assumptions that aren't true > on any decent OS out there ... > > regards, > > Rik Well, the various qmail programs do seem to fsync (though I'm not sure if it's in the right places.) In any case, this link seems to throw some light on the situation: ftp://elektroni.ee.tut.fi/pub/qmail_linux_metadata_message Now, I have no clue if this is correct or not, but the core of the explanation given on that page seems to be: --- So what is this all about? qmail relies on the BSD semantics of immediate update of directories on the disk when link(), unlink(), open() and rename() calls are used. But Linux writes them to the disk asynchronously. My library loaded before libc changes those calls to do the corresponding directory writes too. Then qmail should be reliable against power outages also in Linux. --- So, does anyone know if that is a correct assertion to make, and if softupdates does indeed break it? Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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