linux-kernel - Re: writing file to disk: not as easy as it looks

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Message-ID: <20081203182603.GB22852@elf.ucw.cz>
Date:	Wed, 3 Dec 2008 19:26:03 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>
Cc:	Theodore Tso <tytso@....edu>, Chris Friesen <cfriesen@...tel.com>,
	kernel list <linux-kernel@...r.kernel.org>, aviro@...hat.com
Subject: Re: writing file to disk: not as easy as it looks

On Wed 2008-12-03 18:43:18, Mikulas Patocka wrote:
> > On Wed, Dec 03, 2008 at 09:46:40AM +0100, Pavel Machek wrote:
> > > Yes. fsync() seeems surprisingly high on Rusty's list of broken
> > > interfaces classification ('impossible to use correctly').
> 
> BTW where is that list.

http://ozlabs.org/~rusty/index.cgi/tech/2008-04-01.html

> > To be fair, fsync() was primarily intended for making sure that the
> > data had been written to disk, and not necessarily as a way of making
> > sure that write errors would be properly reflected back to the
> > application.  As you've pointed out, it's not really adequate for that
> > purpose.
> 
> Well, what else do you want to use for databases? (where crashing the 
> whole computer makes less damage than pretending that transaction was 
> committed while it wasn't).

I guess we could modify fsync() to fail if there was _ever_ write
problem on same filesystem. That would make it "safe". And as
ext2/ext3 can't handle metadata write errors anyway... maybe that
should be done?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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