[PATCH v2] selftests/zram: avoid subshells and bc for ratio calculations

[David Disseldorp <ddiss@suse.de>]

Awk is already called for /sys/block/zram#/mm_stat parsing, so use it
to also perform the floating point capacity vs consumption ratio
calculations. The test output is unchanged.

This allows bc to be dropped as a dependency for the zram selftests.
The documented free dependency can also be removed following
d18da7ec37195 ("selftests/zram01.sh: Fix compression ratio calculation")

Signed-off-by: David Disseldorp <ddiss@suse.de>
---
 tools/testing/selftests/zram/README    |  2 --
 tools/testing/selftests/zram/zram01.sh | 18 ++++++++----------
 2 files changed, 8 insertions(+), 12 deletions(-)

v2: drop unused dependencies from selftests/zram/README

diff --git a/tools/testing/selftests/zram/README b/tools/testing/selftests/zram/README
index 110b34834a6fa..510ca5a1087f5 100644
--- a/tools/testing/selftests/zram/README
+++ b/tools/testing/selftests/zram/README
@@ -27,9 +27,7 @@ zram01.sh: creates general purpose ram disks with ext4 filesystems
 zram02.sh: creates block device for swap
 
 Commands required for testing:
- - bc
  - dd
- - free
  - awk
  - mkswap
  - swapon
diff --git a/tools/testing/selftests/zram/zram01.sh b/tools/testing/selftests/zram/zram01.sh
index 8f4affe34f3e4..df1b1d4158989 100755
--- a/tools/testing/selftests/zram/zram01.sh
+++ b/tools/testing/selftests/zram/zram01.sh
@@ -33,7 +33,7 @@ zram_algs="lzo"
 
 zram_fill_fs()
 {
-	for i in $(seq $dev_start $dev_end); do
+	for ((i = $dev_start; i <= $dev_end && !ERR_CODE; i++)); do
 		echo "fill zram$i..."
 		local b=0
 		while [ true ]; do
@@ -44,15 +44,13 @@ zram_fill_fs()
 		done
 		echo "zram$i can be filled with '$b' KB"
 
-		local mem_used_total=`awk '{print $3}' "/sys/block/zram$i/mm_stat"`
-		local v=$((100 * 1024 * $b / $mem_used_total))
-		if [ "$v" -lt 100 ]; then
-			 echo "FAIL compression ratio: 0.$v:1"
-			 ERR_CODE=-1
-			 return
-		fi
-
-		echo "zram compression ratio: $(echo "scale=2; $v / 100 " | bc):1: OK"
+		awk -v b="$b" '{ v = (100 * 1024 * b / $3) } END {
+			if (v < 100) {
+				printf "FAIL compression ratio: 0.%u:1\n", v
+				exit 1
+			}
+			printf "zram compression ratio: %.2f:1: OK\n", v / 100
+		    }' "/sys/block/zram$i/mm_stat" || ERR_CODE=-1
 	done
 }
 
-- 
2.35.3