ZTS: Fix mmp_interval failure

The mmp_interval test case was failing on Fedora 30 due to the built-in
'echo' command terminating the script when it was unable to write to
the sysfs module parameter.  This change in behavior was observed with
ksh-2020.0.0-alpha1.  Resolve the issue by using the external cat
command which fails gracefully as expected.

Additionally, remove some incorrect quotes around the $? return values.

Reviewed-by: Giuseppe Di Natale <guss80@gmail.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #8906

diff --git a/tests/zfs-tests/include/libtest.shlib b/tests/zfs-tests/include/libtest.shlib
index 9c3c20fd9517363c21776e7b9158585d9c8452a6..7078eb30b1c64438cdc2fc402de05dbda6a4f456 100644 (file)
--- a/tests/zfs-tests/include/libtest.shlib
+++ b/tests/zfs-tests/include/libtest.shlib
@@ -3495,13 +3495,13 @@ function set_tunable_impl
        Linux)
                typeset zfs_tunables="/sys/module/$module/parameters"
                [[ -w "$zfs_tunables/$tunable" ]] || return 1
-               echo -n "$value" > "$zfs_tunables/$tunable"
-               return "$?"
+               cat >"$zfs_tunables/$tunable" <<<"$value"
+               return $?
                ;;
        SunOS)
                [[ "$module" -eq "zfs" ]] || return 1
                echo "${tunable}/${mdb_cmd}0t${value}" | mdb -kw
-               return "$?"
+               return $?
                ;;
        esac
 }
@@ -3528,7 +3528,7 @@ function get_tunable_impl
                typeset zfs_tunables="/sys/module/$module/parameters"
                [[ -f "$zfs_tunables/$tunable" ]] || return 1
                cat $zfs_tunables/$tunable
-               return "$?"
+               return $?
                ;;
        SunOS)
                [[ "$module" -eq "zfs" ]] || return 1