Date: Tue, 6 Feb 2001 10:16:22 -0800 (PST) From: Matt Dillon <dillon@earth.backplane.com> To: Julian Elischer <julian@elischer.org> Cc: Mike Silbersack <silby@silby.com>, Rik van Riel <riel@conectiva.com.br>, Poul-Henning Kamp <phk@critter.freebsd.dk>, Charles Randall <crandall@matchlogic.com>, Dan Phoenix <dphoenix@bravenet.com>, Alfred Perlstein <bright@wintelcom.net>, Jos Backus <josb@cncdsl.com>, freebsd-hackers@FreeBSD.ORG, mckusick@mckusick.com Subject: Re: soft updates and qmail (RE: qmail IO problems) Message-ID: <200102061816.f16IGMF62864@earth.backplane.com> References: <Pine.BSF.4.31.0102061149180.14899-100000@achilles.silby.com> <3A802F6E.D4582D54@elischer.org>
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:kirk said (but I have not completely checked it) that if you fsync a file,
:it will effectively fsync all the way back to the root of the filesystem.
:
:I don't know how true this is, but cerainly the inode is updated before
:fsync returns. I cannot tell if any directory entries pointing at that file
:that have not yet been sync'd are forced out before it returns....
:
: __--_|\ Julian Elischer
: / \ julian@elischer.org
This is totally 100% correct. If you fsync() a file, softupdates
will guarentee that not only is the file consistent, but that the
appropriate portions of the directory the file is in will be consistent.
If you crash right then, on boot/fsck the file will be found in the
directory.
A non-softupdates standard filesystem mount, whether it be normal,
synchronous, or asynchronous, cannot make that guarentee. Only
Journaled filesystems (XFS, ReiserFS) can make similar guarentees.
-Matt
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