> How long freeze takes depends on how much data is dirty in the
> filesystem, it should take a similar time to an unmount. However,
> unless this was a very large and dirty filesystem this feels
> like a long time - although it was all system time,
> so something was going on.
6 hours is a long time for an unmount! The volume is ~70GB, and had no
activity on it before I tried to create the snapshots - the machine had just
been rebooted before some attempts.
> The spot you kept seeing on the stack does not make much sense, vn_count
is
> basically an atomic_read.
It just seems that's the place I've hit the break key the most. A closer
examination of my console log suggests it isn't stuck in vn_count, there are
a few occurances of it being somewhere else in xfs_iflush_all - so maybe
it's got itself tangled in a loop for a few hours?
0xe95c3b88 0xc01a1a63 xfs_iflush_all+0xc3
(0xf6d1f000, 0x1, 0xf6d1f000, 0xc, 0xc039ce80)
0xe95c3b88 0xc01a1ab9 xfs_iflush_all+0x119
(0xf6d1f000, 0x1, 0xf6d1f000, 0xc, 0xc039ce80)
0xe95c3b88 0xc01a1ac3 xfs_iflush_all+0x123
(0xf6d1f000, 0x1, 0xf6d1f000, 0xc, 0xc039ce80)
> How repeatable is this?
The problem was persistent across reboots - I rebooted to install a
different LVM version at some stage (move to 1.0.2, from 1.0.1), and it
occurred five times in a row after that. I just rebooted now to say that it
still happens - but, alas - it doesn't want to any more. I'll try again at
some random times throughout the day.
Chris
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