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Date:      Mon, 26 Oct 2015 11:44:25 +0000
From:      Matthew Seaman <m.seaman@infracaninophile.co.uk>
To:        freebsd-questions@freebsd.org
Subject:   Re: cd /.zfs/snapshot hangs (tmux put to uninterruptible sleep)
Message-ID:  <562E1219.4080203@infracaninophile.co.uk>
In-Reply-To: <562E0DDA.3020202@freebsd.org>
References:  <562CB2C2.6090402@kulturflatrate.net> <562CB8CF.7010504@FreeBSD.org> <562CC1DD.9060207@kulturflatrate.net> <562CC308.6060901@FreeBSD.org> <562CC547.8080308@kulturflatrate.net> <562CC7B6.5040404@FreeBSD.org> <562CC939.5060807@kulturflatrate.net> <562E0DDA.3020202@freebsd.org>

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On 10/26/15 11:26, Matthew Seaman wrote:
> On 10/25/15 12:21, Niklaas Baudet von Gersdorff wrote:
>> On 25/10/15 13:14, Matthew Seaman wrote:
>>> Please do go ahead and reset your system.  Just realizing it's happen=
ing
>>> to other people than me is sufficient incentive.
>>
>> OK. Thanks a lot for your help!
>>
>>> PS.  If you need to access one of the troublesome snapshots, use 'zfs=

>>> clone' -- it seems to avoid the various pitfalls.
>>
>> OK. Great.
>>
>=20
> Hmmm... I can't reproduce the problematic effect.  I set up a zfs with
> snapshots like so:
>=20
> # zfs list -t all -r tank/.......1
> NAME
>                     USED  AVAIL  REFER  MOUNTPOINT
> tank/.......1
>                      19K   769G    19K  /.......1
> tank/.......1@....3.........4.........5.........6.........7.........8..=
=2E.....
>                  0      -    19K  -
> tank/.......1@....3.........4.........5.........6.........7.........8..=
=2E......
>                 0      -    19K  -
> tank/.......1@....3.........4.........5.........6.........7.........8..=
=2E......9.........0
>      0      -    19K  -
>=20
> where the contents of the ZFS were:
>=20
> # find /.......1
> /.......1
> /.......1/aaa
> /.......1/aaa/bbb
> /.......1/aaa/bbb/ccc
>=20
> Sorry about the funky filenames -- they're just for counting the
> characters in the automount path for the snapshot.  The result is like
> so (if you can make it out despite the line wrapping my mail client
> wants to add):
>=20
> # find /.......1/.zfs/snapshot
> /.......1/.zfs/snapshot
> find:
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8.........:
> File name too long
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8........
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8......../aaa
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8......../aaa/bbb
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8......../aaa/bbb/ccc
> find:
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8.........9.........0:
> File name too long
>=20
> # cd
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8.........9.........0/aaa/bbb
>=20
> /.......1/.zfs/snapshot/....3.........4.........5.........6.........7..=
=2E......8.........9.........0/aaa/bbb:
> File name too long.
>=20
>=20
> ie.  a mounted path length of 88 characters is OK, but 89 or 100
> characters gets the 'name too long' error.  However, I can't detect any=

> problems after that.  No processes stuck trying to do IO.  So I guess
> that whatever the problem was, it has been fixed in 10.2-RELEASE
>=20
> 	Cheers,
>=20
> 	Matthew
>=20
>=20

Actually, here is the problem:

stingray:/:# zfs destroy -r tank/.......1
cannot unmount '/.......1': Device busy

But that is easily fixed by:

stingray:/:# zfs umount -f /.......1
stingray:/:# zfs destroy -r tank/.......1

I wonder if that's worth a PR?  I recall now this is exactly what I ran
into before, but it seems rather different to what you're seeing.

	Cheers,

	Matthew



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