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

From: Mark Lord
Date: Mon Jun 11 2007 - 18:46:21 EST


Jan Kara wrote:
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.

Yeah, except the task is in Zombie state at this point.
But the umount does fail properly, so I no longer complain about that.

Cheers
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