illumos gate

The following script will cause the zfs receive operation to fail:

1. clean
   zpool destroy tank
   zpool destroy tanker
   rm -f /tank.img /tanker.img

1. create pools
   truncate -s 1g /tank.img
   truncate -s 1g /tanker.img
   zpool create tank /tank.img
   zpool create tanker /tanker.img

1. test case
   zfs create tank/fs
   echo blah > /tank/fs/blah
   zfs snapshot tank/fs@base
   echo grumble > /tank/fs/grumble
   echo blah > /tank/fs/blah2
   zfs snapshot tank/fs@snap2
   echo grumble > /tank/fs/mumble
   echo blah > /tank/fs/blah3
   zfs snapshot tank/fs@snap3
   zfs send -D -R tank/fs@snap3 > send.tank-new
   zfs receive -v tanker/myfs < send.tank-new

There's some additional discussion of this issue in the Linux ZFS tracker here: https://github.com/zfsonlinux/zfs/issues/2210

There are two problems here:

1. When receiving onto an existing filesystem, a snapshot created during the receive process does not get added to the guid->dataset mapping for the stream in dmu_recv_end. This results in failed lookups for deduped streams when a WRITE_BYREF record referred to a snapshot received earlier in the stream. The new snapshot is now always added.

2. The newly created snapshot was also not set properly in dmu_recv_end_sync when receiving onto an existing filesystem, referencing the snapshot before the new receiving dataset rather than the existing filesystem. In that case, it's now properly set with respect to origin_head.