mdadm/test: Add one test case for raid5 reshape

This case tries to allow raid5 reshape to use backwards direction.
It changes chunksize after reshape and stops the raid. Then starts
the raid again.

Signed-off-by: Xiao Ni <xni@redhat.com>
Suggested-by:  Jes Sorensen <jes.sorensen@gmail.com>
Suggested-by:  Zhilong Liu <zlliu@suse.com>
Suggested-by:  Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Jes Sorensen <jsorensen@fb.com>

test

@@ -320,6 +320,13 @@ check() {
 		grep -sq "inactive" /proc/mdstat ||
 			die "array is not inactive!"
 		;;
+	# It only can be used when there is only one raid
+	chunk )
+		chunk_size=`awk -F',' '/chunk/{print $2}' /proc/mdstat | awk -F'[a-z]' '{print $1}'`
+		if [ "$chunk_size" -ne "$2" ] ; then
+			die "chunksize should be $2, but it's $chunk_size"
+		fi
+		;;
 	* )
 		die "unknown check $1"
 		;;

tests/02r5grow

@@ -34,3 +34,20 @@ check nosync
 sh tests/testdev $md0 3 $[size/2] 128
 
 mdadm -S $md0
+
+# create a raid5 array and change the chunk
+mdadm -CR $md0 --level raid5 --metadata=1.1 --chunk=32 --raid-disks 3 --size $[size/2] $dev1 $dev2 $dev3
+check wait
+check state UUU
+check chunk 32
+
+mdadm $md0 --grow --chunk=64
+check reshape
+check wait
+check chunk 64
+
+mdadm -S $md0
+mdadm -A $md0 $dev1 $dev2 $dev3
+check state UUU
+check chunk 64
+mdadm -S $md0