Public bug reported: If you do zfs send -D with 0.8.x userland and 2.0.x kernel, it will actually try to produce a deduplicated send stream (whereas 2.0.x userland stubs out that flag and prints a "this did nothing, stop trying to use it" note).
On the system that generated it (20.04 amd64, running 5.11.0-38-generic with zfs-0.8.3-1ubuntu12.13 zfs-kmod-2.0.2-1ubuntu5.1): $ dd if=/dev/urandom of=/badidea/1 bs=1M count=16 $ sudo dd if=/dev/urandom of=/badidea/1 bs=1M count=16 $ sudo cp /badidea/1 /badidea/2 $ sudo zfs snap badidea@snap1 $ sudo zfs send -RLeD badidea@snap1 > dedupstream $ sudo zfs recv badidea/badbadidea < dedupstream internal error: Unknown error 1037 Aborted On my Debian 10 testbed running zfs-2.1.99-422_gb0f3f393d (and same for kmod): cannot receive: stream has unsupported feature, feature flags = 7 This functionality was dropped in commit 196bee4cfd576fb15baa6a64ad6501c594f45497. Since it does all its voodoo in userland, it can indeed still generate a dedup'd stream. Might it make sense to at least print a warning if using zfs send --dedup with 2.0.x, as well as maybe copying the warning that 2.0.x spits out on attempting to receive such a stream, so people don't conclude that being unable to receive a send stream they generated means their system is broken? ** Affects: zfs-linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to zfs-linux in Ubuntu. https://bugs.launchpad.net/bugs/1949249 Title: zfs send --dedup with HWE kernel modules produces unreceivable stream Status in zfs-linux package in Ubuntu: New Bug description: If you do zfs send -D with 0.8.x userland and 2.0.x kernel, it will actually try to produce a deduplicated send stream (whereas 2.0.x userland stubs out that flag and prints a "this did nothing, stop trying to use it" note). On the system that generated it (20.04 amd64, running 5.11.0-38-generic with zfs-0.8.3-1ubuntu12.13 zfs-kmod-2.0.2-1ubuntu5.1): $ dd if=/dev/urandom of=/badidea/1 bs=1M count=16 $ sudo dd if=/dev/urandom of=/badidea/1 bs=1M count=16 $ sudo cp /badidea/1 /badidea/2 $ sudo zfs snap badidea@snap1 $ sudo zfs send -RLeD badidea@snap1 > dedupstream $ sudo zfs recv badidea/badbadidea < dedupstream internal error: Unknown error 1037 Aborted On my Debian 10 testbed running zfs-2.1.99-422_gb0f3f393d (and same for kmod): cannot receive: stream has unsupported feature, feature flags = 7 This functionality was dropped in commit 196bee4cfd576fb15baa6a64ad6501c594f45497. Since it does all its voodoo in userland, it can indeed still generate a dedup'd stream. Might it make sense to at least print a warning if using zfs send --dedup with 2.0.x, as well as maybe copying the warning that 2.0.x spits out on attempting to receive such a stream, so people don't conclude that being unable to receive a send stream they generated means their system is broken? To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/zfs-linux/+bug/1949249/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp