Zfs import issue

[Peter Maloney]

Okay, then we have the same problem except I need one more zfs command
after the send to hang the filesystem. In my case, this means I can
simply never call zfs twice before the first is done. eg. a file based
lock in my scripts; or wrap the zfs command with something that locks.
Does this solve (workaround) your problem?

I find (in 8.2-STABLE, 8.3-STABLE) the file system works 100% during a
send unless there is something else with a "zfs" command that happens;
only zfs commands will hang/block , not ls, df, etc.; in my example
below, I destroyed a snapshot, and that command hung/blocked. And when
the hung/blocked zfs command is a write command, such as destroy, then
the filesystem is hung/blocked too, including ls, df, etc.. And when a
hung/blocked command is killed, it seems to be permanently hung (but
could just be enormously slow).

On 10/06/2012 05:04 AM, Ram Chander wrote:
> Yes importing means "zfs recv" , "df" hangs, "cd " to the filesystem
> hangs. Basically entire filesystem is inaccessbile. Once "zfs recv"
> completes, all is normal.
>
> On Thu, Oct 4, 2012 at 2:54 PM, Peter Maloney
> <peter.maloney at brockmann-consult.de
> <mailto:peter.maloney at brockmann-consult.de>> wrote:
>
>     I find this sort of thing to be common, but not exactly as you
>     describe.
>     I don't know if I tried df, but "zfs list" hangs (as well as any other
>     zfs related command, maybe even zdb). And I don't know what you mean
>     "importing zfs snapshot", so I'm guessing you mean zfs recv.
>
>     eg.
>
>     zfs send somedataset at somesnapshot | .......
>     (leave it running in background)
>
>     zfs list
>     (works fine; I guess it works because send is read-only)
>
>     zfs destroy somedataset at someothersnapshot
>     (hang; I guess because this is a write operation, so it needs to wait
>     for the read lock on zfs send to finish the transaction)
>
>     zfs list
>     (hang)
>
>     I'm not sure if df hangs too.
>
>     At this point, using kill -9 doesn't solve anything, and if you
>     kill the
>     zfs send, it's possible that every zfs command and df will hang.
>
>     And I don't know what, but I'm mostly sure there is something I
>     can run
>     that will make even "ls" hang after this point.
>
>
>     On 10/03/2012 03:34 PM, Andriy Gapon wrote:
>     > on 03/10/2012 14:43 Ram Chander said the following:
>     >> Hi,
>     >>
>     >>  I am importing zfs snapshot to freebsd-9 from anther host running
>     >> freebsd-9.  When the import happens, it locks the filesystem,
>     "df" hangs
>     >> and unable to use the filesystem. Once the import completes,
>     the filesystem
>     >> is back to normal and read/write works fine.  The same doesnt
>     happen in
>     >> Solaris/OpenIndiana.
>     >>
>     >> # uname -an
>     >> FreeBSD hostname 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Tue Jan  3
>     07:46:30
>     >> UTC 2012     root at farrell.cse.buffalo.edu:/
>     >> usr/obj/usr/src/sys/GENERIC  amd64
>     >>
>     >> Zfs ver: 28
>     >>
>     >>
>     >> Any inputs would be helpful. Is there any way to overcome this
>     freeze ?
>     > What if you add -n option to df?
>     >
>
>
>     --
>
>     --------------------------------------------
>     Peter Maloney
>     Brockmann Consult
>     Max-Planck-Str. 2
>     21502 Geesthacht
>     Germany
>     Tel: +49 4152 889 300
>     Fax: +49 4152 889 333
>     E-mail: peter.maloney at brockmann-consult.de
>     <mailto:peter.maloney at brockmann-consult.de>
>     Internet: http://www.brockmann-consult.de
>     --------------------------------------------
>
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