[PATCH] common/atomicwrites: fix _require_scratch_write_atomic when awu_max_fs is empty

[Zorro Lang <zlang@kernel.org>]

If a kernel doesn't support atomic write, _get_atomic_write_unit_min
and _get_atomic_write_unit_max will get nothing.

  local awu_min_bdev=$(_get_atomic_write_unit_min $SCRATCH_DEV)
  local awu_max_bdev=$(_get_atomic_write_unit_max $SCRATCH_DEV)

If $awu_min_bdev and $awu_max_bdev are empty, then the logic likes
"[ $awu_min_bdev -eq 0 ] && [ $awu_max_bdev -eq 0 ]" is meaningless,
and it causes g/767 hang on system which doesn't support atomic
write.

Signed-off-by: Zorro Lang <zlang@kernel.org>
---
 common/atomicwrites | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/common/atomicwrites b/common/atomicwrites
index 33526399d..bbcc4e7c5 100644
--- a/common/atomicwrites
+++ b/common/atomicwrites
@@ -47,8 +47,9 @@ _require_scratch_write_atomic_multi_fsblock()
 
 	_scratch_unmount
 
-	test $awu_max_fs -ge $((bsize * 2)) || \
+	if [ -z "$awu_max_fs" -o $awu_max_fs -lt $((bsize * 2)) ];then
 		_notrun "multi-block atomic writes not supported by this filesystem"
+	fi
 }
 
 _require_scratch_write_atomic()
@@ -58,7 +59,8 @@ _require_scratch_write_atomic()
 	local awu_min_bdev=$(_get_atomic_write_unit_min $SCRATCH_DEV)
 	local awu_max_bdev=$(_get_atomic_write_unit_max $SCRATCH_DEV)
 
-	if [ $awu_min_bdev -eq 0 ] && [ $awu_max_bdev -eq 0 ]; then
+	if [ -z "$awu_min_bdev" -o -z "$awu_max_bdev" ] || \
+		[ $awu_min_bdev -eq 0 -a $awu_max_bdev -eq 0 ];then
 		_notrun "write atomic not supported by this block device"
 	fi
 
@@ -75,7 +77,8 @@ _require_scratch_write_atomic()
 
 	_scratch_unmount
 
-	if [ $awu_min_fs -eq 0 ] && [ $awu_max_fs -eq 0 ]; then
+	if [ -z "$awu_min_fs" -o -z "$awu_max_fs" ] || \
+		[ $awu_min_fs -eq 0 -a $awu_max_fs -eq 0 ];then
 		_notrun "write atomic not supported by this filesystem"
 	fi
 }
-- 
2.49.0