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

From: Jan Kara
Date: Mon Jun 11 2007 - 07:07:02 EST

> Chuck Ebbert wrote:
> >On 06/07/2007 11:41 AM, Andrew Morton wrote:
> >>> mount /var/lib/mythtv -oremount,ro
> >>> sync
> >>> umount /var/lib/mythtv
> >>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.
But if that app has been waiting in D state, kill -9 does nothing to it
until it wakes up, doesn't it? So fd's are still open and umount fails.

Jan Kara <jack@xxxxxxx>
SuSE CR Labs
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