btrfs/237: adjust uuid heuristics

Using $(findmnt -n -o UUID mount-directory) only works on
util-linux v2.38, not on 2.37. Even debian-testing has util-linux
v2.37, so use a mechanism which has worked for longer to fetch the
UUID.

Without this the test fails on permission failure on accessing
the file /sys/fs/btrfs/"$uuid"/bg_reclaim_threshold as $uuid is
empty. So while at it, add a check to ensure the UUID is never
empty.

Use $AWK_PROG in case the preferred awk program is not the
preferred awk program.

Cc: Karel Zak <kzak@redhat.com>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Adam Manzanares <a.manzanares@samsung.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

diff --git a/tests/btrfs/237 b/tests/btrfs/237
index 5168777ee1ec9f1aded0fa1343a4603aa4daa69d..96940549ea0061c77ce2e0e1dc2bb879fe8c4e08 100755 (executable)
--- a/tests/btrfs/237
+++ b/tests/btrfs/237
@@ -41,7 +41,14 @@ zonesize=$((zonesize << 9))
 _scratch_mkfs >/dev/null 2>&1
 _scratch_mount -o commit=1 # 1s commit time to speed up test
 
-uuid=$(findmnt -n -o UUID "$SCRATCH_MNT")
+uuid=$($BTRFS_UTIL_PROG filesystem show $SCRATCH_DEV |grep uuid: |\
+        $AWK_PROG '{print $NF}')
+
+if [[ "$uuid" == "" ]]; then
+       echo "UUID for $SCRATCH_DEV is empty, this is not expected"
+       exit 1
+fi
+
 reclaim_threshold=75
 echo $reclaim_threshold > /sys/fs/btrfs/"$uuid"/bg_reclaim_threshold
 fill_percent=$((reclaim_threshold + 2))