Script reproducing https://github.com/zfsonlinux/zfs/issues/7365

issue-#7365.sh

#!/bin/sh
set -x
issue="7365"
sdate="`date +%s`" # need a variable path/poolname component as can't reuse the same until reboot
tmpdir=/tmp/$issue
poolfile=$tmpdir/$sdate.ima
poolname=issue-$issue-$sdate
mountpoint=$tmpdir/source-$sdate

mkdir -p $tmpdir
touch $poolfile
truncate --size=1G $poolfile

echo > /sys/module/zfs/parameters/zfs_max_recordsize 16777216

zpool create -m none -d \
        -o feature@large_blocks=enabled \
        -O recordsize=16M $poolname $poolfile
zfs create $poolname/source -o mountpoint=$mountpoint

echo > $mountpoint/large.block                  # putting a byte in a file
truncate --size=16M $mountpoint/large.block     # and making it 16M long

zfs snap $poolname/source@testing
zfs send -L $poolname/source@testing \
        | zfs recv -v $poolname/target # hangs here in recv _after_ the 16M block received

# does not go below this line
zpool destroy $poolname
rm $poolfile