linux-kernel - Re: ext3fs: umount+sync not enough to guarantee metadata-on-disk

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Message-ID: <20070610183148.GB4272@ucw.cz>
Date:	Sun, 10 Jun 2007 18:31:48 +0000
From:	Pavel Machek <pavel@....cz>
To:	Mark Lord <lkml@....ca>
Cc:	Chuck Ebbert <cebbert@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Stephen Tweedie <sct@...hat.com>,
	Theodore Ts'o <tytso@....edu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: ext3fs: umount+sync not enough to guarantee metadata-on-disk

Hi!

> >>Did this succeed?  If the application is still 
> >>truncating that file, the
> >>umount should have failed.
> >
> >Shouldn't sync should wait for truncate to finish?
> 
> The part that gets me here, and that others might be 
> missing,
> is that we are not waiting for ftruncate at this point.
> 
> We're waiting for unlink.  The application that was 
> doing ftruncate
> in tiny little doses has been sent a kill-9 signal, so 
> what should
> be happening now (confirmed by disk activity LEDs) is 
> the file should
> just be getting deleted the same as if we did "rm 
> bigfile" on it.

Well, AFAICT kill-9 signal delivery can take time. It still might be
doing ftruncate.

It would be interesting to know when in that sequence mythtv dies...
or perhaps put loop 'while killall -9 mythtv returns success, sleep 1'
into shutdown scripts?
							Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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