[LTP] [PUSHED] zram01.sh: Workaround division by 0 on vfat on ppc64le

[Richard Palethorpe]

Repeatedly read /sys/block/zram*/mm_stat for 1 sec. This should fix bug
on ppc64le on stable kernels, where mem_used_total is often 0.

Signed-off-by: Petr Vorel <pvorel@suse.cz>
Reviewed-by: Li Wang <liwang@redhat.com>
Reviewed-by: Richard Palethorpe <rpalethorpe@suse.com>

[rpalethorpe: s/loop/check/ suggested by Li]
---

rpalethorpe:
        This may not fix the problem, but it can rule out a simple race
        condition.

 .../kernel/device-drivers/zram/zram01.sh      | 27 +++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/testcases/kernel/device-drivers/zram/zram01.sh b/testcases/kernel/device-drivers/zram/zram01.sh
index 58d233f91..6bc305f2c 100755
--- a/testcases/kernel/device-drivers/zram/zram01.sh
+++ b/testcases/kernel/device-drivers/zram/zram01.sh
@@ -105,6 +105,26 @@ zram_mount()
 	tst_res TPASS "mount of zram device(s) succeeded"
 }
 
+read_mem_used_total()
+{
+	echo $(awk '{print $3}' $1)
+}
+
+# Reads /sys/block/zram*/mm_stat until mem_used_total is not 0.
+check_read_mem_used_total()
+{
+	local file="$1"
+	local mem_used_total
+
+	tst_res TINFO "$file"
+	cat $file >&2
+
+	mem_used_total=$(read_mem_used_total $file)
+	[ "$mem_used_total" -eq 0 ] && return 1
+
+	return 0
+}
+
 zram_fill_fs()
 {
 	local mem_used_total
@@ -133,9 +153,12 @@ zram_fill_fs()
 			continue
 		fi
 
-		mem_used_total=`awk '{print $3}' "/sys/block/zram$i/mm_stat"`
+		TST_RETRY_FUNC "check_read_mem_used_total /sys/block/zram$i/mm_stat" 0
+		mem_used_total=$(read_mem_used_total /sys/block/zram$i/mm_stat)
+		tst_res TINFO "mem_used_total: $mem_used_total"
+
 		v=$((100 * 1024 * $b / $mem_used_total))
-		r=`echo "scale=2; $v / 100 " | bc`
+		r=$(echo "scale=2; $v / 100 " | bc)
 
 		if [ "$v" -lt 100 ]; then
 			tst_res TFAIL "compression ratio: $r:1"
-- 
2.40.1